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Monitoring in the field
British Journal of Anaesthesia 97 (1): 46–56 (2006)
doi:10.1093/bja/ael136
Advance Access publication June 2, 2006
Monitoring in the field N. M. McGuire1 2* 1
Royal Air Force, RAF Innsworth, UK. 2Adult Intensive Care, John Radcliffe Hospital, Oxford OX3 9DU, UK *E-mail: [email protected]
Br J Anaesth 2006; 97: 46–56 Keywords: complications, aeromedical; complications, military; monitoring, field
Introduction: the military medical services Military medical services care for military and civilian patients injured in hostilities, accidents, or with acute illnesses. Many of these patients become unwell away from centres with established medical care facilities and need care and treatment in the field. This review explores the requirements for one important aspect of this care, patient monitoring. In military practice, monitoring needs to take place in temporary, but static locations, such as field hospitals, and during patient transfers to centres for more definitive care. Environmental factors, relating both to the location of the patient, and the modes of transport used by the military, as well as the regulations regarding carriage of medical equipment mean careful equipment selection and team training are very important. In spite of operating in adverse conditions, the Military Medical Services operate to professional standards of care comparable with their civilian counterparts. The UK Defence Medical Services (DMS) are committed to provide health care in the field to the level expected within the National Heath Service (NHS).2 A field hospital provides all normal care, where practical, as well as having provision
for surge capacity for major incidents. Patient monitoring in field hospitals reflects the standards set by professional bodies such as the Association of Anaesthetists of Great Britain and Ireland (AAGBI) and the UK Intensive Care Society14 21 22 for UK-based hospital practice, although monitoring is often enhanced to compensate for the environment. There is little, if any, published information on monitoring in the field which would meet today’s ‘evidence-based’ criteria, nor is there ever likely to be. Rather, this review is based on the experiences of the DMS in procuring equipment to meet very stringent requirements and developing an effective aeromedical evacuation service. It is also based on practical experience during military deployments abroad, missions during peace keeping, humanitarian missions and support for combat operations. This review covers monitoring in two different environments, in the field hospital and during transfers, and then covers the vital role of training.
The stable field environment Conditions in the field are invariably austere and resources are limited. In addition, the environment may be actively
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This review looks at the challenges faced when monitoring patients in the field environment. It is considered from the perspective of the UK Defence Medical Services and their experiences over the past 20 yr. The lessons learned are applicable to many other circumstances where a high standard of care, for a large spectrum of patients, is to be delivered in the most inhospitable conditions. The environmental influences on monitoring equipment such as extremes of heat, cold and altitude must be considered and dealt with. Minimal monitoring standards required by professional bodies have to be undertaken, but there is a need to exceed them to compensate for the untoward effects of hostile environments. Patient and machine variables monitored and their relative importance in the field are also explored. Varying field locations are illustrated and the types of monitoring required to care for patients in different areas of field units are discussed. Patient transfers and the particular difficulties encountered in the military context are also reviewed. Undertaking aeromedical evacuation is one of the most challenging environments in the field and the solutions required to undertake it are explored. These considerations are used to propose design requirements necessary to provide appropriate monitoring in all other field conditions. The standards set for carriage of equipment in the air and the testing required allowing compliance with the regulations in force in the UK, are outlined. Finally the importance of practitioner training to undertake these roles in the field is discussed.
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Fig 1. Anaesthetic equipment and monitoring in mature field operations.
Fig 2. Resuscitation in the field hospital.
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temperatures of up to 50 C are encountered in summer in hot, arid climates and can lead to surface temperatures of 65 C or more. In cold climates temperatures may reduce to 15 C or less and be much lower when wind chill is taken into account. Even in desert conditions, where day time temperatures are high, without cloud cover night temperatures may reduce to freezing or below. Humidity is low in deserts, but may approach 100% in tropical zones. There are also the effects of rapid changes of temperature and humidity at the same time. This is in marked contrast to conditions usually found in modern, heated or air-conditioned hospitals where most practitioners work. The majority of medical devices are designed to be used in these fixed, wellappointed locations, with minimal regard being given to function in extreme environmental conditions. In the field there are the more direct environmental hazards to equipment from rain, dust and even salt mist ingress. Not only are these conditions physically and chemically damaging to the monitoring equipment, they also predispose to microbiological growth and colonization of equipment. The combined effect of all of these influences is to cause expansion, shrinkage, distortion, mould growth and corrosion. Equipment casings, seals, components and adhesives can degrade rapidly, which may interfere both with the functioning and longevity of equipment. Service intervals of equipment need to be shortened and the overall lifespan of devices is reduced. Unreliability of monitoring equipment may result in critical incidents and patient harm. The shelf life of consumables for monitors may be reduced as well. Extra servicing and premature failure of devices also leads to increased cost. To overcome these problems requires that some equipment be modified and some be cared for or packaged differently. Many of these issues are addressed when the equipment is assessed for transfers in military air transport, where a lot of the environmental factors listed above may be encountered. In the field environment the familiar audible and visual indicators which indicate machine malfunction may be lost because of increased background noise, low light conditions or other distractions. In these circumstances the monitors which monitor the medical devices themselves need to be observed more closely. A simple example would be the display on a syringe driver, which gives an indication of infusion rate and volume delivered, and displays user prompts if there is a problem preventing the drug being infused. These ‘machine monitors’ provide information regarding the status and function of the electromechanical devices in use, and indicators which provide information about normal status are as important as those indicating malfunction. Machine-monitored variables depend on the type and function of the equipment involved and include indicators of pressure variation, device cycling or of delivery of gas or fluid (Table 1). It is for this reason that some devices are unsuitable for use outside civilian hospitals and sometimes even away from a given location in these hospitals. In the example
hostile, even when ‘combat’ is not occurring in the military context. These factors often impair the ability to undertake even basic activities, such as simple medical care and invariably make it difficult to monitor patients effectively. Military field units may be in relatively fixed locations. This is usually the case for large field hospitals (Fig. 1) and for dedicated hospital ships. If the field hospital is in a fixed location environmental conditions and supplies of resources can be relatively stable. However, in major disasters or in exposed locations (Fig. 2) there may be a constant and changing environmental or military threat so the field hospital may have to move at short notice. This also applies to forward locations in highly mobile battle conditions. Field hospitals have to operate in all environments, usually without the benefits of climate control. Air
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Table 1 Machine-monitored variables Multifunction monitor
Ventilator
Volumetric pump
Syringe driver
Suction apparatus
ECG connections Artifact report Defibrillator power selected Mains power Battery status Mode (manual, auto) Malfunction indication
Oxygen pressure Inspired oxygen level Air pressure Normal function or malfunction Turbine function Battery status Power supply
Delivered pressure Rate of delivery Volume delivered Infusion volume set Air in i.v. line Battery status
Pressure Rate of delivery Volume delivered Syringe near empty
Suction pressure Battery status Charging status Mains power
of the disconnected ventilator; if the sound of the disconnection was undetectable, because of ambient noise or distraction, an audio visual alarm (of sufficient volume and brightness) should be triggered and in addition the indicators of cycling or flow should show that ventilation is not occurring. If these adjuncts to safety are not provided the patient is at increased risk, and the ventilator may be unsuitable for field hospital use. The patient flow through a field hospital is very similar to a civilian hospital. Patients are directed to different areas according to their clinical needs as they progress through the field unit. Intensity of monitoring varies, escalating or reducing, according to the nature and stage of the patient’s illness. For the majority of military patients discharge means entry into the strategic medical evacuation chain for return to the NHS. The monitoring used is identical to that used in civilian practice in equivalent care areas. In resuscitation areas clinical observation is supported by monitoring ECG, ventilatory frequency, pulse oximetry, non-invasive blood pressure and temperature. Other variables such as invasive pressures, arterial blood gases and end-tidal CO2 are measured as required. In the operating theatre the concentration of inhalational agents, inspired oxygen and end-tidal CO2, are routinely measured according to minimal monitoring standards for anaesthesia. This is particularly important to avoid errors when using apparatus such as draw over vaporizers, which are not routinely used in everyday practice. High-dependency and intensive care have the enhanced monitoring necessary to care for the critically ill. Monitoring strategies and equipment are adapted to allow for all potential scenarios. Patient-monitored variables used in routine monitoring are shown in Table 2. Ideal monitoring equipment for field use measures all of the variables required to deliver full care. As such it has the capability equivalent to that found in fixed facilities. As all equipment should be, it must be highly user-friendly with intuitive menus and have indications of both normal and abnormal function. In addition it must be reliable, rugged, have the capability to utilize multiple power supplies, be economic to run and comply with all of the relevant regulations. Solving problems for the highly demanding air environment often provides answers to all of the areas of concern in a field hospital. Some of the most important characteristics of ideal field and transfer equipment are summarized in Table 3.
Battery status
Table 2 Patient-monitored variables
Table 3 Characteristics of ideal transfer equipment Characteristic
Note
Type Weight Fixation Size
Measures variables required Lightweight, portable Can be fixed to the required standard Easy storage with displays large enough to be visible Low centre of gravity. Easily fixed, held and moved Easily manipulated controls. Recognized modes and settings Menu led with expected variables immediately available User-friendly, interchangeable with universal connections Loss of function reverts to least hazardous condition Normal function indicated Identified promptly both visually and audibly Visual and audible failure indicator. Reverts to failsafe mode Survives environment, movement and handling High reliability, low failure risk Has all required functions for that equipment type Data collection and transmission, remote alarms Multiple and independent Worldwide voltage and frequency Able to use aircraft auxiliary power supply Exchangeable internal battery and external connection Internal battery covering external power failure Low consumption, multiple types, ambient air as failsafe Maintain all functions in all environments Complies with relevant regulations and standards Complies with generic specification Supplied with complete training package
Shape Simplicity of operation Intuitive controls Consumables Failsafe Function indication Abnormal function Failure Rugged Reliability Functional Interfaces Power supplies Mains power supply Aircraft power supply Battery power supply Back-up battery Medical gases Equipment characteristics STANAGS/DEF STAN/IEC/ISO Generic specification Training programme
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ECG Non-invasive blood pressure Invasive blood pressure Central venous pressure Intracranial pressure End-tidal CO2 concentration Oxygen saturation Neuromuscular block Temperature Tidal volume Respiratory frequency Inspiratory pressures (mean, peak, plateau, PEEP)
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Patient transfers In routine intra-hospital and inter-hospital transfers practitioners are often content with a lower standard of monitoring. They accept this risk, on behalf of the patient, because it is only for a ‘short period of time’. It is often delegated to trainees who have had no formal teaching in transfers and are mostly unaware of the pitfalls. What is actually required, in an isolated and mobile situation, is continuous high-quality monitoring of the same variables that are deemed essential in the static environment, by experienced practitioners capable of responding appropriately to changes in their condition. UK Military doctrine states that care should be seamless, continuous and progressive throughout the evacuation chain.28 With extended timelines and this expectation, the standards applied in routine practice are not sufficient. Many of the features required for monitoring equipment used for long transfers in difficult circumstances are overlooked, misunderstood or not implemented by manufacturers. These include effects of the surroundings on the devices and the effects of the devices on equipment nearby. Often equipment used for transferring patients in civilian practice does not fit the desired profile well and even that supposedly designed for transfers is often inadequate. Equipment that is used for transfers must be, rugged and highly reliable. It must have sufficient internal power for the duration of the transfer and additional capability for unexpected delays. If battery life is limited the batteries must be able to be replaced, or the device must be capable of utilizing multiple power supplies (aircraft supplies, vehicle supplies, external batteries, inverters, and mains supplies). Changing batteries or power supplies preferably should not interrupt the device’s function. Devices must also be able to be restrained appropriately while in use, as they may be exposed to considerable ‘g’ forces and vibration in aircraft or even surface vehicles. Suitable tie-down systems, straps and clamp systems are needed. Transferring patients directly from the battlefield causes other difficulties. This may be by land or air, but invariably, frontline vehicles used in evacuation of casualties are designed for operational survivability and little consideration is given to space or comfort. Not only is monitoring extremely difficult, but even basic care is hard to deliver and in combat ‘scoop and run’ often precludes detailed monitoring. Similar difficulties are encountered by police medics dealing with injured officers in civil unrest situations.25 Evacuation by air has probably been practised since the 1920s23 and provides more extreme examples of many of the problems encountered in other transfer situations. Military air transfer may be fixed or rotary wing aircraft and may be tactical or strategic. Forward tactical transfer is usually by rotary wing, because it is fast and flexible, being able to avoid ground hazards and obstacles.
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Tactical transfers vary from a few minutes to 1 or 2 h. Longer missions are unusual, because other considerations, such as the range of the aircraft, are important. It is also more difficult to provide increasing levels of care with a continually moving patient. This is most significant in primary evacuation, because a patient may not be fully resuscitated and deteriorate unacceptably without definitive interventions. Logistic issues are considered when planning. Tactical fixed wing missions are used to access higher levels of care or the onward strategic evacuation chain. Intra-theatre tactical transfer may be in rotary or fixed wing aircraft, depending on circumstances. Fixed wing transfers in tactical aircraft are not usually for longer than around 4 h, with well-stabilized patients. These times are based on accepted clinical considerations of care of the sick and wounded from the military doctrine. Observing timelines reduces the opportunity for the patient to deteriorate in the adverse conditions of the tactical environment. For the DMS, strategic transfer is usually from a field or base facility to a UK NHS hospital. For some countries and during specific operations, staging facilities providing intermediate or definitive care may be used. During war fighting or international repatriations there are a variety of problems which can upset the timings and flight plans. Aircraft may be delayed, diverted or be unable to land at the destination airport. Weather can change, permissions to fly over countries may be withdrawn or be denied and problems with avionics can occur. Royal Air Force strategic aeromedical evacuation planning assumes that care will be provided, largely unsupported, for up to 24 h. This allows for long transfers, such as from the Falkland Islands or for a number of untoward logistic events to occur before significant resource problems arise. In flight patient care is progressive and proactive as it is in the hospital and monitoring that would be appropriate to that setting must also be available. Air transfer usually precludes surgical procedures, but even this eventuality must be considered for extended lines and where hostile conditions exist. Even in the worst case, the aim is to deliver the patient in as good a condition as they were when the transfer began and ideally they should improve. Patients who are critically ill may deteriorate despite best efforts, but this should not be attributable to the transfer itself. The concept is of a continuous chain of high-quality care, reducing morbidity and mortality to an absolute minimum (Figs 3 and 4). Minimal monitoring standards require the monitoring of inspired oxygen and end-tidal CO2 in ventilated patients. Polarographic oxygen analysers consume less power and are less likely to be susceptible to electromagnetic interference (EMI) than equivalent paramagnetic analysers. The disadvantage is that they measure the partial pressure of oxygen and rely on an algorithm to calculate percentage. Partial pressure decreases as an aircraft gains altitude, even with pressurized cabins, although the percentage of the gases remains the same as those at sea level. As a result the devices
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Fig 3. Monitoring during critical care aeromedical evacuation.
Fig 4. Essential equipment for intensive care in the air.
under-read the oxygen percentage at altitude, although the value on the readout gives the ‘equivalent’ sea level FIO2. More sophisticated devices may have barometric pressure compensation built in. With portable devices a correction factor may need to be applied to obtain the correct concentration or a manual recalibration at ambient pressure may be possible. Unlike oxygen monitors, end-tidal CO2 monitors are unaffected by altitude in the ventilated patient. If the patient’s CO2 production is constant the end-tidal partial pressure remains the same. All end-tidal devices (even those that display percentages and not partial pressure) actually measure partial pressure and as this is constant for CO2 they will read virtually the same at altitude as they do at sea level. The end-tidal partial pressure of oxygen and nitrogen,
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however, fall with altitude and therefore the actual percentage of CO2 rises despite this. In the spontaneously breathing patient, who is compensating for hypoxia at higher altitudes, end-tidal CO2 will decrease as a result of hyperventilation, but this is not an issue at normal cabin altitude unless lung function is abnormal to begin with, and is negated by adding inspired oxygen. Side-stream capnography is susceptible to water in sample tubes and machines using this system are not usually designed for anything other than short transfers. The pumps used in these systems often consume a lot of power. Mainstream measurement is practical, but also uses considerable power which needs to be allowed for and adds weight to tracheal tube connections. Although a recommendation for minimal monitoring, in the critically ill the discrepancies which occur because of alveolar–arterial differences, high positive end expiratory pressure and reduced cardiac output may reduce this monitor to a sophisticated disconnection detector. When power is a consideration for a monitor, regular measurement of arterial blood gases is a better option, provided other disconnect alarms are adequate. Depending on their design some ventilators will monitor ambient pressure and compensate for changes in gas density and viscosity that occur with changes in altitude. With others manual compensation must be made. On volume preset ventilators delivered tidal volumes will be less than set tidal volumes unless these compensations are undertaken in ventilators with compressors or turbines supplying air to the system. Gas-driven constant flow generators will be less susceptible to these effects because of the high pressure driving gas for their fluidic circuits, but the lower partial pressure of entrained air for the inspired gas will affect tidal volume and minute ventilation. To avoid these issues close monitoring of these variables must be undertaken. The characteristics of equipment must be understood before it is taken into the air and it must also be monitored continuously in flight. Change in pressure affects equipment and components which contain air. As ambient pressure is reduced bubbles may expand in fluids within monitoring transducers and cause dampening of arterial or venous pressure waves leading to inaccurate readings. Meticulous removal of air will avoid this. Most fluids contain some dissolved gas which will come out of solution at altitude and will form bubbles which may coalesce and present further hazard. In this situation the use of air detection monitoring in fluid delivery systems and the use of air traps is of value. Air traps have to be watched closely as their volume may increase and allow air into lines if not adjusted correctly. Balloons on catheters in the pulmonary circulation present a potential problem if they expand. Deflating them and reviewing the need for these devices reduces the hazard. Monitoring and support equipment also have items such as touch control pads which contain air and may be vulnerable to pressure change. Equipment itself is not usually air tight, but transport containers may be and
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generation of multiple artifacts. In these conditions alarms may be activated inappropriately. In view of the inability to rely on clinical signs and the paradox that machine-monitored variables are of greater importance yet potentially unreliable presents a dilemma. To overcome this, enhanced monitoring must be undertaken and measures taken to ensure the accuracy of what is actually measured. The limitations of oximetry in the critically ill are well known. Research into specific effects of altitude has been limited to the static simulated environment, with low numbers of patients being studied, but there are suggestions of reduced accuracy of pulse oximetry.17 In practice the effect of vibration may be significant, but new technologies may help to overcome the effects of motion artifact.3 16 The effects of coarse and fine vibration generated by aircraft have not been studied on this type of monitor as far as the author is aware. To avoid effects the sites where probes are attached should be padded and restrained to avoid movement if at all practical. In this environment measurement of arterial blood gases remains the gold standard and should be undertaken where any doubt of accuracy exists. It is also advised that for the critically ill, where oximetry is often of limited value, arterial blood gases are measured before and after transferring to a transport ventilator, if the ventilator settings are changed in transfer or if there is suspicion that the condition of the patient has changed. Even if there are no apparent changes the gases should be checked at least every hour in transit, as is the practice in the intensive care. Hand-held devices are commercially available to measure blood gases and other variables. These devices use a small sample of blood which is injected into a cartridge containing reagents. This is then read by the hand-held device. The operating range for barometric pressure, humidity and temperature limited, but are wide enough for use in most circumstances. The limitations of space and lighting within the aircraft environment may impair visibility. As with the other environmental considerations, some aircraft provide better conditions than others. In these conditions certain types of display on monitors are difficult to see in low light or from acute angles and bright sunlight can render monitor screens unreadable. At night aircraft lights are routinely dimmed on take-off and landing. In the military environment, some missions require that internal red light is used before landing to accustom the crew to low light conditions outside the aircraft. On other missions when the aircrew are using night vision equipment all light sources are extinguished. In these circumstances there may be a complete blackout for a number of hours before landing. There have been occasions where subsequent unloading of equipment and loading of the patient have been undertaken in complete darkness as well. This is then followed by flight in the same conditions of blackout. To reduce the effect of inertial forces and vibration, impact resistant and absorbent foam materials are
require to be vented. Some equipment may have to be modified to avoid problems with specific components. The disposable items used with clinical monitors must be packaged to maintain their integrity and avoid contamination. The packaging contains gas and may be damaged as they expand at altitude and must be carefully inspected before the item is used. Finally, aircraft ascend and descend reasonably rapidly, so ambient pressure, temperature, and as a consequence relative humidity may change quickly. Drop and topple tests are required for medical equipment to obtain the compulsory ‘Conformite Europe´ene’ marking.7 There are also standards relating to resistance to forces with the carriage of equipment in land-based ambulances.1 For air carriage the standards are more rigorous and equipment carried by air must be able to resist damage during the three-dimensional inertial forces which are encountered during normal flight while continuing to function. In the event of an accident to prevent secondary damage, casings must remain intact and not break from restraints. These regulations apply equally to any packaging used to protect the equipment on an outward journey, and during the transfer with the patient. Solutions which provide protection against vibration have assisted in complying with these regulations. Noise is a problem in many vehicles, but it is a particular problem with aircraft. It poses health and safety hazards to the patient and attending staff and interferes with communication. It is a greater problem in rotary wing, small aircraft and larger military aircraft, designed for the transport of freight. The disorientation caused by constant loud noise with varying frequencies compounds the lack of normal feedback from familiar sounds. Increasing the volume of alarms may assist, but it is often negated by protective equipment and communication headsets. Further developments in alarm technology may be of value, such as linked, graded alerts which can be fed into the headsets worn by the clinical staff. Equipment not specifically designed to be used in this environment may be unexpectedly disrupted for other reasons such as batteries or attachments being dislodged. During the vibration testing of equipment used by the RAF, for example, the battery pack of a monitor became displaced and the monitor failed testing. To solve the problem the battery compartment was modified. In extreme vibration monitoring of infusions must be controlled by mechanical devices as manually timing a drip may be impossible. Clinical monitoring such as palpating the pulse, measuring blood pressure, viewing respiratory patterns and seeing colour changes is often difficult or impossible in aircraft. This is because of reduced or altered lighting, noise and vibration. Additionally an aircraft is mobile in three dimensions and exerts inertial forces on the crew, patient and equipment. In these circumstances monitors also may become unreliable. Variables such as ECG, non-invasive blood pressure and pulse oximetry are subject to the
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devices in the proximity, which may be generating electrical or magnetic emissions. Radiated emissions are the electromagnetic outputs which inadvertently occur because of the passage of electrical current through components and cables within devices. These emissions may be constant or may produce spikes of output, such as those associated with the discharge of a defibrillator. Emissions vary with different modes of operation and the electrical loads applied to the device. They vary with the particular power supply being used and when switching between multiple power supplies. Conducted emissions are those which feedback through cables during operation of a device. These may lead to emissions affecting other equipment through the power supply. The device may also be sensitive to conducted emissions attributable to the activity of other equipment attached to the same power supply. This sensitivity may be exposed when switching inductive loads produces electrical spikes. Signal cables are also susceptible to conducted emissions. To reduce these effects to acceptable levels or stop them altogether requires attention to build quality and proper testing to identify modifications which may be required. The casing enclosing electrical equipment must be highly conductive and any joints in the casing must be electrically tight and also highly conductive. Screw holes in casings can be protected by using conductive washers. Components within the casing can be electrically designed to reduce output spikes when operating and specific shielding may be applied to certain components if this cannot be done. Electrical filters can be applied to monitoring and power cables and external connections can be constructed to avoid electrical leaks. The production of EMI is possible from any electrical device, no matter how small and is not confined to devices that contain radio transmitters. This is because any component which has current flow has an associated electrical field and is a potential source of interference. These emissions may escape from equipment casings, but they are particularly associated with screens and cables. For example, in a recent incident, an incorrectly configured monitor was tested and the screen output was in the order of 100 times that of an actively scanning mobile telephone. Cables that carry power to equipment or link the equipment to the patient (signal cables) can radiate emissions, acting as aerials. Mobile telephones and portable radio handsets provide an example of portable communications equipment which can cause problems with medical devices, including monitors. Mobile telephones produce significant radiated emissions as they scan and transmit, even when a call is not being made. This can interfere with nearby electrical equipment producing untoward effects on displays and can affect the accuracy or function of equipment. As a result there have been adverse event warnings by the Medical Devices Agency, now part of the Medicines and Healthcare products
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incorporated into modified equipment. Locking washers and mounting components on isolating fixtures also contribute to attenuating these effects. Some equipment is fitted with additional padding within restraint packaging. To aid visibility, high-definition colour screens, with wide viewing angles are used. If the screen can be configured it is an advantage, as being able to flip the display adds to flexibility in positioning monitors. In enforced low light conditions, monitoring displays may be dimmed or shielded with variably opaque covers. The equipment, including the attached patient interfaces, used to monitor in the field may be categorized according to function, type or role. From the engineering perspective it may be either mechanical, electrical or a mixture of both. Mechanical devices within monitors, such as pumps for gas analysis or non-invasive blood pressure are susceptible to contamination and must be protected by appropriate filters. Fans for cooling computer processors also draw contaminants into equipment and require protection with filters. To deal with extremes of temperature insulation or larger heat sinks may be applied to components. Electrical devices require further consideration as their specification may require other modification. In the field there are many factors influencing monitoring outside the control of the operators. Those relating to climate have been alluded to above. Some are peculiar to the military environment, but may become more important in the increasingly technologically complex environment in which civilian practice occurs. For example, there may be powerful communications equipment nearby or aircraft operating in close proximity. Problems can also be associated with transmitters with High Performance Radio Local Area Networks or Terrestrial Trunked Radio Systems.29 While these factors do not often lead to overt difficulties they can occasionally have untoward effects, by producing induced currents in nearby monitoring equipment. The same situation occurs with mobile phones, but military transmitters may be orders of magnitude more powerful. In modern warfare, weapons specifically designed to interfere with electronic equipment have been deployed and will undoubtedly be used again. These weapons include electromagnetic pulse (EMP) weapons11 24 which are designated as non-lethal in normal circumstances, but would create lifethreatening situations to patients in the hospital environment. They were developed after the discovery of the EMP phenomenon, while studying the effects of nuclear weapons.6 13 The screens, computer processors, transformers and other electrical components of critical care monitoring devices may produce significant EMI or electromagnetic compatibility (EMC) problems. EMI is the effect on other equipment, in the proximity of a device which interferes with normal function of that equipment. This adverse influence is attributable to the electrical or magnetic emissions that are transmitted from it. EMC is the susceptibility of a device to interference and abnormal function caused by electrical
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This has been superseded by the Airworthy Medical Equipment (AME) test programme. This testing began in the 1980s to ensure that all medical equipment carried on RAF aircraft was compliant with relevant standards and regulations. It also addressed the issue of potential interference of aircraft systems on medical equipment. In addition to EMC, AME testing considers the overall survivability of equipment in aircraft. Examples of the variables tested are in Table 4. There are absolute requirements to test variables such as the effects of sudden or explosive decompression or the effects of changes in gravitational forces in a simulated aircraft environment. Despite this requirement, pragmatism still demands certain compromises. For example, testing to assess waterproof characteristics is acceptable to assess the effects of liquid splash as immersing equipment completely is clearly outside normal use. Taking the test to an inappropriate level unnecessarily increases the cost of producing equipment and does not increase flight safety. If equipment is to be connected to aircraft power supplies, more rigorous testing is required to assess the effect of conductive emissions. More demands are made if rectifiers, inverters or transformers are used to convert the aircraft supply from 115 V and 400 Hz to either a DC voltage of a different frequency and voltage of AC power. To avoid this extra cost batteries as internal or external power supplies are often used instead. They also provide self-sufficiency if aircraft power is not available. The cost of testing equipment may be as much as £20k per item and this is not insignificant if low cost items are required to have the full range of tests. To simplify matters and to still satisfy the aircraft authorities a Generic Specification12 of equipment to support patients in the air was produced. As a result of this, as Table 4 Test variables Test variables Electromagnetic compatibility Conducted emissions Radiated susceptibility Conducted susceptibility (low frequency) Conducted susceptibility (high frequency) Electrostatic discharge Shock, drop and topple survivability Altitude Sudden decompression Explosive decompression Vibration Acceleration (crash conditions) Humidity Mould growth Salt corrosion Fluid contamination Waterproofness Temperature Sand and dustproofing Requirements of aircraft design and technical authorities: aircraft electrical and mechanical interface requirements Other regulations
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Regulatory Agency (MHRA).8 9 For this reason their use in hospitals has been restricted. Updates from the MHRA have attempted to rationalize advice18 19 on the use of any communications devices, but despite these documents, confusion still remains. Electromagnetic radiation may affect monitoring equipment, but also equipment used by the transfer team has the potential to create interference which will cause problems with an aircraft’s electronics. The use of mobile telephones on aircraft is completely prohibited because of concerns that they may interfere with critical systems such as flight controls and navigation. Conductive or radiated emissions may be significant from any of the equipment used to support a patient. Laptop computers have also been implicated in interfering with aircraft navigation systems.26 Modern medical support equipment and in particular monitoring have screens in addition to containing the electrical components already discussed. Airline cabin attendants routinely direct that certain types of electronic equipment are switched off during take-off and landing. This is to reduce the potential effects these devices may have at these crucial times. In military aircraft device emissions may be detected and electronic countermeasures initiated. This may trigger the inappropriate release of chaff (strips of metal, foil or glass fibre with metal content used to reflect electromagnetic energy) and flares from an armed aircraft. In flight the flight crew will also undertake immediate evasive manoeuvres for obvious reasons. Sudden changes in aircraft attitude may cause injury to passengers or medical team members and patients. On the ground the release of countermeasures may be extremely hazardous because of the nature of the released material and the proximity of other installations such as refuelling equipment. For this reason Aircraft Authorities of NATO have tight controls over the electromagnetic characteristics of devices used in military aircraft. These controls are embodied in the Standard NATO Agreements (STANAGS) that lay out in detail, the levels of electrical and magnetic outputs which are acceptable within different aircraft types. There are also regulations pertaining to materials used in construction of equipment and for power supplies. This is important in the case of portable equipment, as some types of internal batteries can cause problems. Lithium ion batteries, common in many types of equipment, are actually categorized as dangerous air cargo as in certain circumstances they can explode. The connection to aircraft power supplies is a further issue because of radiated conducted emissions. Aircraft Authorities such as the Civil Aviation Authority have regulations that deal with the carriage of equipment in addition to that integral to the aircraft. These regulations also cover equipment which is not related to and may potentially interfere with aircraft function. At present restrictions relating to medical equipment are such that ‘carry on’ equipment is usually exempt. For the RAF, equipment testing was undertaken as the Special Purpose Medical Equipment testing programme.
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compromise their safety. With such a device it is often necessary to sedate a patient inappropriately and use neuromuscular blocking agents that would not normally be required. This should demand additional monitoring for the ventilator and the use of a peripheral nerve stimulator as there are also greater concerns regarding disconnections or awareness when a patient is not spontaneously breathing. In practice the simple transfer ventilator has less monitoring and few individuals use the additional monitoring that they should have in this situation. A more capable ventilator, with the required monitoring avoids compromise. Aeromedical transfer of critically ill patients is one of the most demanding areas of medicine and should only be undertaken by those who are specifically trained and equipped.20 This reduces the risk to the patient and stress on personnel. An equipment training course was specifically designed for RAF personnel undertaking critical care aeromedical duties. This Critical Care Air Support Team Equipment training was designed to provide team members with a complete educational package on the equipment they use during transfer. It is undertaken within the ICU setting to maintain relevance and to allow for consolidation of knowledge. The training is assessed by examination and when personnel complete the course they understand in detail the normal function and idiosyncrasies of their equipment. Practitioners routinely respond to alarms and alerts which may occur during patient care. They appraise the situation, using other variables, to assess the significance of these warnings. They are also aware of the subtle indicators of normal function that are in the background. With experience these become familiar and can be a significant adjunct to monitoring. Trained and experienced practitioners may be alerted to potential problems before alarms trigger and will be able to act accordingly. For example, noting the change in sound as a ventilator becomes disconnected. Here the experienced practitioner would respond before disconnection alarms were triggered and well before a change in the patient’s vital signs triggered alarms. The final element of training is therefore practice and hence experience.
Organization and training Human factors are extremely important in the field as it is a high-stress environment. If the human factors are not addressed, regardless of how effective the monitors are, there will be a failure to recognize abnormalities and no action will be taken.31 There is little or no peer support in austere isolated locations and it is impractical to have the user and maintenance manuals for all of the devices used. The use of portable electronic storage may assist with the latter, but in theory such devices require testing for use in the air, and the equipment itself. Full discussion of human factors is not appropriate in the context of clinical monitoring alone, but is relevant to the complete delivery of care.4 10 15 30 Organization and high-quality training (Fig. 5) are the key to success in the field,5 provided the equipment meets the criteria outlined in this review. Each item must be understood in detail to avoid making fundamental errors regarding capability, function, mode selection and alarm indications. The commonest mistakes made during transfers are overestimating battery life and misunderstanding mode settings.27 Monitors of these variables must be accurate, user-friendly and understood. Detailed training also does much to reduce errors of and allows standards to be properly assessed and maintained. Training also leads to a greater understanding of the care that is possible in the field. Accepting functionally inferior machines adds risk to the patient or negates previous progress that the patient has made. For example, using a so-called simple transfer ventilator when transferring a patient, or using it as a field ICU ventilator, will potentially
Conclusion Effective monitoring in the field demands the appreciation of a number of factors. It depends on having an understanding of the rigours of the environment and a thorough knowledge of the capabilities and limitations of devices being used. Personnel must be properly trained to survive and function in the environment, as well as be able to care for and protect their patients. This requires that they are current in clinical practice and have undertaken a detailed training. Meeting these requirements reduces the risk to patients and personnel and allows for advanced patient care in the field. The feedback loop is completed when experienced and well-trained practitioners constantly
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new equipment is required the general performance characteristics are already known. This enables the engineering authorities to evaluate the most cost-effective solution, while providing all of the functions for optimal care, demanded of the operators. Other issues such as ease of maintenance are also taken into account. As an added benefit the Generic Specification provides manufacturers with the opportunity to view what is expected of equipment when undertaking future research and development. This rational approach has saved much time and reduced costs while maintaining the highest standards. All equipment, including monitoring equipment, needs to be maintained to the highest levels and this requires adhering to the most rigorous schedule recommended by the manufacturer, or in some cases, these standards need to be exceeded. All equipment has up-to-date servicing before being transferred to the field and it is checked again before being brought into use. In the case of equipment used for patient transfers it must also have had appropriate user checks before a mission. It is more appropriate that the team using the equipment is responsible for servicing and user checks as they have ownership of any subsequent problems.
Monitoring in the field
Capability requirement
Training needs analysis
Entry level professional training
Generic training
Aircraft equipment Dunker drills Dinghy drills Smoke drills Aircraft safety Aircraft familiarisation Winch training
Examination Theory Practical
Clinical consolidation Mentorship
Equipment Theory Practical Transfer medicine Infectious diseases Monitoring Ventilation Law and ethics Health and safety Standards Aviation medicine Inter hospital transfers Intra hospital transfers Fitness to fly
Workshops and practical experience
Relevant clinical practice
CEPD
Practitioner: capable, current, credible, confident (defensible) Fig 5 Training practitioners for critical care aeromedical support team roles in the RAF. CEPD, continuing education and professional development.
3 Barker SJ. ‘Motion-resistant’ pulse oximetry: a comparison of new and old models. Anesth Analg 2002; 95: 967–72 4 The British Military Surgery Pocket Book. Crown Copyright, 2004 5 Borthwick M, McGuire NM, Scott D. How to prepare for the unexpected. Pharm J 2005; 275: 141–2 6 Chronister RD et al. Nuclear Hardness Test Planning Guide for Program Managers. DNA-H-90-140, 1993. Available from http:// www.dtra.mil/toolbox/directorates/td/programs/rtfc/defin.cfm 7 Council Directive 93/68/EEC of 22 July 1993. Available from http://www.ce-marking.org/directive-9368eec-ce-marking. html 8 Emergency service radios and mobile data terminals: compatibility problems with medical devices. Device Bulletin 1999 (02). Medical Devices Agency publication, 1999. Available from http://www. mhra.go.uk 9 Electromagnetic Compatibility of Medical Devices with Mobile Communications. Device Bulletin 9702. Medical Devices Agency publication, 1997. Available from http://www.mhra.go.uk
monitor the situation and respond to problems identified, in a timely and appropriate way.
Acknowledgement The author is grateful to Dr D. Young, Clinical Director AICU, John Radcliffe Hospital Oxford, for his help and advice during the preparation of this manuscript.
References 1 Air, water and difficult terrain ambulances. Medical Devices interface requirements for the continuity of patient care. BS EN 13718-1: 2002. . Available from http://www.standardsdirect. org/standards/standards1/StandardsCatalogue24_view_11040. html 2 Army Medical Services Core Doctrine. D/AMD/113/18, 2000
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Leadership Teamwork Fitness Weapons Survival Security
Role specific training
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22
23 24
25
26 27 28 29
30
31
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Anaesthetists of Great Britain and Ireland, Revised December 2000. Available from http://www.aagbi.org/guidelines.html Recommendations for the Transfer of Patients with Acute Head Injuries to Neurosurgical Units. The Neuroanaesthesia Society of Great Britain & Ireland and The Association of Anaesthetists of Great Britain and Ireland, 1996. Available from http://www.aagbi. org/pdf/26doc.pdf Scholl MD, Geshekter CL. The Zed Expedition: the world’s first air ambulance? J R Soc Med 1989; 82: 679–80 Schwartau W. Information Warfare—Cyberterroism: Protecting Your Personal Security in the Electronic Age. New York: Thunder’s Mouth Press, 1996 Spiers G. Resuscitation, riots and the police. New developments in ambulance resuscitation. Ambulance Services Institute Seminar, Telford, April 2006 Strauss B, Morgan GM. Everyday threats to aircraft safety. Issues Sci Technol, 2002/2003: 82–6 Thames Valley Critical Care Network. Working Party Transfer Surveys, 2003,2004 United Kingdom Joint Medical Doctrine. Joint Warfare Publication, 4.03 Update on Electromagnetic Compatibility of Medical Devices with Mobile Communications: TETRA (Terrestrial Trunked Radio System) and Outside media broadcasts from hospital premises. Safety Notice 2001 (06). Medical Device Alert. Medical Devices Agency, March 2001. Available from http://www.mhra. go.uk U.S. Army Center for Health Promotion and Preventive Medicine, Health Information Operations Division—Health Information, June 2004. Available from http://chppmwwwapgea.army.mil Young D. Does monitoring affect ICU outcome? Joint RCoA/BJA Symposium on Clinical Monitoring, March 15–16, 2006
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10 Field Marshal Lord Carver. Morale in battle—the medical and the military. J R Soc Med 1989; 82: 67–71 11 Fulghum D.A. EMP weapons lead race for non-lethal technology. Aviation Week and Space Technology 1993; 61 12 Generic Specification for Special Purpose Aeromedical Equipment (SPAME)—Final Issue 4. ERA Technology Report Feb 2006. Available from http://www.era.co.uk 13 Glasstone S, Dolan PJ. The Effects of Nuclear Weapons, 3rd Edn. U.S. Department of Defense and Department of Energy, 1977 14 Guidelines for the transport of the critically ill adult. Intensive Care Society, 2002. Available from http://www.ics.ac.uk 15 Jones N, Roberts P, Greenberg N. Peer-group risk assessment: a post-traumatic management strategy for hierarchical organizations. Occup Med (Lond) 2003; 53: 469–75 16 Jopling MW, Mannheimer PD, Bebout DE. Sensitivity and specificity performance during motion artefact in three pulse oximeters designed for use in motion. Annual Meeting Abstracts ASA, October 14–18, 2005 17 Mehm WJ, Dillard TA, Berg BW, Dooley JW, Rajagopal KR. Accuracy of oxyhemoglobin saturation monitors during simulated altitude exposure of men with chronic obstructive pulmonary disease. Aviat Space Environ Med 1991; 62: 418–21 18 Mobile communications interference. Medicines and Healthcare Products Regulatory Agency publication, 2005. Available from http://www.mhra.go.uk 19 New advice issued on the use of mobile phones in hospitals. Reference 2004/0287. Press Release, Medicines and Healthcare products Regulatory Agency, July 29, 2004. Available from http:// www.mhra.go.uk 20 Rainford DJ, Gradwell DP. Ernstings Aviation Medicine, 4th Edn, London: Hodder Arnold, 2006. 21 Recommendations for Standards of Monitoring During Anaesthesia and Recovery, 3rd Edn. The Association of
doi:10.1093/bja/ael136
Advance Access publication June 2, 2006
Monitoring in the field N. M. McGuire1 2* 1
Royal Air Force, RAF Innsworth, UK. 2Adult Intensive Care, John Radcliffe Hospital, Oxford OX3 9DU, UK *E-mail: [email protected]
Br J Anaesth 2006; 97: 46–56 Keywords: complications, aeromedical; complications, military; monitoring, field
Introduction: the military medical services Military medical services care for military and civilian patients injured in hostilities, accidents, or with acute illnesses. Many of these patients become unwell away from centres with established medical care facilities and need care and treatment in the field. This review explores the requirements for one important aspect of this care, patient monitoring. In military practice, monitoring needs to take place in temporary, but static locations, such as field hospitals, and during patient transfers to centres for more definitive care. Environmental factors, relating both to the location of the patient, and the modes of transport used by the military, as well as the regulations regarding carriage of medical equipment mean careful equipment selection and team training are very important. In spite of operating in adverse conditions, the Military Medical Services operate to professional standards of care comparable with their civilian counterparts. The UK Defence Medical Services (DMS) are committed to provide health care in the field to the level expected within the National Heath Service (NHS).2 A field hospital provides all normal care, where practical, as well as having provision
for surge capacity for major incidents. Patient monitoring in field hospitals reflects the standards set by professional bodies such as the Association of Anaesthetists of Great Britain and Ireland (AAGBI) and the UK Intensive Care Society14 21 22 for UK-based hospital practice, although monitoring is often enhanced to compensate for the environment. There is little, if any, published information on monitoring in the field which would meet today’s ‘evidence-based’ criteria, nor is there ever likely to be. Rather, this review is based on the experiences of the DMS in procuring equipment to meet very stringent requirements and developing an effective aeromedical evacuation service. It is also based on practical experience during military deployments abroad, missions during peace keeping, humanitarian missions and support for combat operations. This review covers monitoring in two different environments, in the field hospital and during transfers, and then covers the vital role of training.
The stable field environment Conditions in the field are invariably austere and resources are limited. In addition, the environment may be actively
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This review looks at the challenges faced when monitoring patients in the field environment. It is considered from the perspective of the UK Defence Medical Services and their experiences over the past 20 yr. The lessons learned are applicable to many other circumstances where a high standard of care, for a large spectrum of patients, is to be delivered in the most inhospitable conditions. The environmental influences on monitoring equipment such as extremes of heat, cold and altitude must be considered and dealt with. Minimal monitoring standards required by professional bodies have to be undertaken, but there is a need to exceed them to compensate for the untoward effects of hostile environments. Patient and machine variables monitored and their relative importance in the field are also explored. Varying field locations are illustrated and the types of monitoring required to care for patients in different areas of field units are discussed. Patient transfers and the particular difficulties encountered in the military context are also reviewed. Undertaking aeromedical evacuation is one of the most challenging environments in the field and the solutions required to undertake it are explored. These considerations are used to propose design requirements necessary to provide appropriate monitoring in all other field conditions. The standards set for carriage of equipment in the air and the testing required allowing compliance with the regulations in force in the UK, are outlined. Finally the importance of practitioner training to undertake these roles in the field is discussed.
Monitoring in the field
Fig 1. Anaesthetic equipment and monitoring in mature field operations.
Fig 2. Resuscitation in the field hospital.
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temperatures of up to 50 C are encountered in summer in hot, arid climates and can lead to surface temperatures of 65 C or more. In cold climates temperatures may reduce to 15 C or less and be much lower when wind chill is taken into account. Even in desert conditions, where day time temperatures are high, without cloud cover night temperatures may reduce to freezing or below. Humidity is low in deserts, but may approach 100% in tropical zones. There are also the effects of rapid changes of temperature and humidity at the same time. This is in marked contrast to conditions usually found in modern, heated or air-conditioned hospitals where most practitioners work. The majority of medical devices are designed to be used in these fixed, wellappointed locations, with minimal regard being given to function in extreme environmental conditions. In the field there are the more direct environmental hazards to equipment from rain, dust and even salt mist ingress. Not only are these conditions physically and chemically damaging to the monitoring equipment, they also predispose to microbiological growth and colonization of equipment. The combined effect of all of these influences is to cause expansion, shrinkage, distortion, mould growth and corrosion. Equipment casings, seals, components and adhesives can degrade rapidly, which may interfere both with the functioning and longevity of equipment. Service intervals of equipment need to be shortened and the overall lifespan of devices is reduced. Unreliability of monitoring equipment may result in critical incidents and patient harm. The shelf life of consumables for monitors may be reduced as well. Extra servicing and premature failure of devices also leads to increased cost. To overcome these problems requires that some equipment be modified and some be cared for or packaged differently. Many of these issues are addressed when the equipment is assessed for transfers in military air transport, where a lot of the environmental factors listed above may be encountered. In the field environment the familiar audible and visual indicators which indicate machine malfunction may be lost because of increased background noise, low light conditions or other distractions. In these circumstances the monitors which monitor the medical devices themselves need to be observed more closely. A simple example would be the display on a syringe driver, which gives an indication of infusion rate and volume delivered, and displays user prompts if there is a problem preventing the drug being infused. These ‘machine monitors’ provide information regarding the status and function of the electromechanical devices in use, and indicators which provide information about normal status are as important as those indicating malfunction. Machine-monitored variables depend on the type and function of the equipment involved and include indicators of pressure variation, device cycling or of delivery of gas or fluid (Table 1). It is for this reason that some devices are unsuitable for use outside civilian hospitals and sometimes even away from a given location in these hospitals. In the example
hostile, even when ‘combat’ is not occurring in the military context. These factors often impair the ability to undertake even basic activities, such as simple medical care and invariably make it difficult to monitor patients effectively. Military field units may be in relatively fixed locations. This is usually the case for large field hospitals (Fig. 1) and for dedicated hospital ships. If the field hospital is in a fixed location environmental conditions and supplies of resources can be relatively stable. However, in major disasters or in exposed locations (Fig. 2) there may be a constant and changing environmental or military threat so the field hospital may have to move at short notice. This also applies to forward locations in highly mobile battle conditions. Field hospitals have to operate in all environments, usually without the benefits of climate control. Air
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Table 1 Machine-monitored variables Multifunction monitor
Ventilator
Volumetric pump
Syringe driver
Suction apparatus
ECG connections Artifact report Defibrillator power selected Mains power Battery status Mode (manual, auto) Malfunction indication
Oxygen pressure Inspired oxygen level Air pressure Normal function or malfunction Turbine function Battery status Power supply
Delivered pressure Rate of delivery Volume delivered Infusion volume set Air in i.v. line Battery status
Pressure Rate of delivery Volume delivered Syringe near empty
Suction pressure Battery status Charging status Mains power
of the disconnected ventilator; if the sound of the disconnection was undetectable, because of ambient noise or distraction, an audio visual alarm (of sufficient volume and brightness) should be triggered and in addition the indicators of cycling or flow should show that ventilation is not occurring. If these adjuncts to safety are not provided the patient is at increased risk, and the ventilator may be unsuitable for field hospital use. The patient flow through a field hospital is very similar to a civilian hospital. Patients are directed to different areas according to their clinical needs as they progress through the field unit. Intensity of monitoring varies, escalating or reducing, according to the nature and stage of the patient’s illness. For the majority of military patients discharge means entry into the strategic medical evacuation chain for return to the NHS. The monitoring used is identical to that used in civilian practice in equivalent care areas. In resuscitation areas clinical observation is supported by monitoring ECG, ventilatory frequency, pulse oximetry, non-invasive blood pressure and temperature. Other variables such as invasive pressures, arterial blood gases and end-tidal CO2 are measured as required. In the operating theatre the concentration of inhalational agents, inspired oxygen and end-tidal CO2, are routinely measured according to minimal monitoring standards for anaesthesia. This is particularly important to avoid errors when using apparatus such as draw over vaporizers, which are not routinely used in everyday practice. High-dependency and intensive care have the enhanced monitoring necessary to care for the critically ill. Monitoring strategies and equipment are adapted to allow for all potential scenarios. Patient-monitored variables used in routine monitoring are shown in Table 2. Ideal monitoring equipment for field use measures all of the variables required to deliver full care. As such it has the capability equivalent to that found in fixed facilities. As all equipment should be, it must be highly user-friendly with intuitive menus and have indications of both normal and abnormal function. In addition it must be reliable, rugged, have the capability to utilize multiple power supplies, be economic to run and comply with all of the relevant regulations. Solving problems for the highly demanding air environment often provides answers to all of the areas of concern in a field hospital. Some of the most important characteristics of ideal field and transfer equipment are summarized in Table 3.
Battery status
Table 2 Patient-monitored variables
Table 3 Characteristics of ideal transfer equipment Characteristic
Note
Type Weight Fixation Size
Measures variables required Lightweight, portable Can be fixed to the required standard Easy storage with displays large enough to be visible Low centre of gravity. Easily fixed, held and moved Easily manipulated controls. Recognized modes and settings Menu led with expected variables immediately available User-friendly, interchangeable with universal connections Loss of function reverts to least hazardous condition Normal function indicated Identified promptly both visually and audibly Visual and audible failure indicator. Reverts to failsafe mode Survives environment, movement and handling High reliability, low failure risk Has all required functions for that equipment type Data collection and transmission, remote alarms Multiple and independent Worldwide voltage and frequency Able to use aircraft auxiliary power supply Exchangeable internal battery and external connection Internal battery covering external power failure Low consumption, multiple types, ambient air as failsafe Maintain all functions in all environments Complies with relevant regulations and standards Complies with generic specification Supplied with complete training package
Shape Simplicity of operation Intuitive controls Consumables Failsafe Function indication Abnormal function Failure Rugged Reliability Functional Interfaces Power supplies Mains power supply Aircraft power supply Battery power supply Back-up battery Medical gases Equipment characteristics STANAGS/DEF STAN/IEC/ISO Generic specification Training programme
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ECG Non-invasive blood pressure Invasive blood pressure Central venous pressure Intracranial pressure End-tidal CO2 concentration Oxygen saturation Neuromuscular block Temperature Tidal volume Respiratory frequency Inspiratory pressures (mean, peak, plateau, PEEP)
Monitoring in the field
Patient transfers In routine intra-hospital and inter-hospital transfers practitioners are often content with a lower standard of monitoring. They accept this risk, on behalf of the patient, because it is only for a ‘short period of time’. It is often delegated to trainees who have had no formal teaching in transfers and are mostly unaware of the pitfalls. What is actually required, in an isolated and mobile situation, is continuous high-quality monitoring of the same variables that are deemed essential in the static environment, by experienced practitioners capable of responding appropriately to changes in their condition. UK Military doctrine states that care should be seamless, continuous and progressive throughout the evacuation chain.28 With extended timelines and this expectation, the standards applied in routine practice are not sufficient. Many of the features required for monitoring equipment used for long transfers in difficult circumstances are overlooked, misunderstood or not implemented by manufacturers. These include effects of the surroundings on the devices and the effects of the devices on equipment nearby. Often equipment used for transferring patients in civilian practice does not fit the desired profile well and even that supposedly designed for transfers is often inadequate. Equipment that is used for transfers must be, rugged and highly reliable. It must have sufficient internal power for the duration of the transfer and additional capability for unexpected delays. If battery life is limited the batteries must be able to be replaced, or the device must be capable of utilizing multiple power supplies (aircraft supplies, vehicle supplies, external batteries, inverters, and mains supplies). Changing batteries or power supplies preferably should not interrupt the device’s function. Devices must also be able to be restrained appropriately while in use, as they may be exposed to considerable ‘g’ forces and vibration in aircraft or even surface vehicles. Suitable tie-down systems, straps and clamp systems are needed. Transferring patients directly from the battlefield causes other difficulties. This may be by land or air, but invariably, frontline vehicles used in evacuation of casualties are designed for operational survivability and little consideration is given to space or comfort. Not only is monitoring extremely difficult, but even basic care is hard to deliver and in combat ‘scoop and run’ often precludes detailed monitoring. Similar difficulties are encountered by police medics dealing with injured officers in civil unrest situations.25 Evacuation by air has probably been practised since the 1920s23 and provides more extreme examples of many of the problems encountered in other transfer situations. Military air transfer may be fixed or rotary wing aircraft and may be tactical or strategic. Forward tactical transfer is usually by rotary wing, because it is fast and flexible, being able to avoid ground hazards and obstacles.
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Tactical transfers vary from a few minutes to 1 or 2 h. Longer missions are unusual, because other considerations, such as the range of the aircraft, are important. It is also more difficult to provide increasing levels of care with a continually moving patient. This is most significant in primary evacuation, because a patient may not be fully resuscitated and deteriorate unacceptably without definitive interventions. Logistic issues are considered when planning. Tactical fixed wing missions are used to access higher levels of care or the onward strategic evacuation chain. Intra-theatre tactical transfer may be in rotary or fixed wing aircraft, depending on circumstances. Fixed wing transfers in tactical aircraft are not usually for longer than around 4 h, with well-stabilized patients. These times are based on accepted clinical considerations of care of the sick and wounded from the military doctrine. Observing timelines reduces the opportunity for the patient to deteriorate in the adverse conditions of the tactical environment. For the DMS, strategic transfer is usually from a field or base facility to a UK NHS hospital. For some countries and during specific operations, staging facilities providing intermediate or definitive care may be used. During war fighting or international repatriations there are a variety of problems which can upset the timings and flight plans. Aircraft may be delayed, diverted or be unable to land at the destination airport. Weather can change, permissions to fly over countries may be withdrawn or be denied and problems with avionics can occur. Royal Air Force strategic aeromedical evacuation planning assumes that care will be provided, largely unsupported, for up to 24 h. This allows for long transfers, such as from the Falkland Islands or for a number of untoward logistic events to occur before significant resource problems arise. In flight patient care is progressive and proactive as it is in the hospital and monitoring that would be appropriate to that setting must also be available. Air transfer usually precludes surgical procedures, but even this eventuality must be considered for extended lines and where hostile conditions exist. Even in the worst case, the aim is to deliver the patient in as good a condition as they were when the transfer began and ideally they should improve. Patients who are critically ill may deteriorate despite best efforts, but this should not be attributable to the transfer itself. The concept is of a continuous chain of high-quality care, reducing morbidity and mortality to an absolute minimum (Figs 3 and 4). Minimal monitoring standards require the monitoring of inspired oxygen and end-tidal CO2 in ventilated patients. Polarographic oxygen analysers consume less power and are less likely to be susceptible to electromagnetic interference (EMI) than equivalent paramagnetic analysers. The disadvantage is that they measure the partial pressure of oxygen and rely on an algorithm to calculate percentage. Partial pressure decreases as an aircraft gains altitude, even with pressurized cabins, although the percentage of the gases remains the same as those at sea level. As a result the devices
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Fig 3. Monitoring during critical care aeromedical evacuation.
Fig 4. Essential equipment for intensive care in the air.
under-read the oxygen percentage at altitude, although the value on the readout gives the ‘equivalent’ sea level FIO2. More sophisticated devices may have barometric pressure compensation built in. With portable devices a correction factor may need to be applied to obtain the correct concentration or a manual recalibration at ambient pressure may be possible. Unlike oxygen monitors, end-tidal CO2 monitors are unaffected by altitude in the ventilated patient. If the patient’s CO2 production is constant the end-tidal partial pressure remains the same. All end-tidal devices (even those that display percentages and not partial pressure) actually measure partial pressure and as this is constant for CO2 they will read virtually the same at altitude as they do at sea level. The end-tidal partial pressure of oxygen and nitrogen,
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however, fall with altitude and therefore the actual percentage of CO2 rises despite this. In the spontaneously breathing patient, who is compensating for hypoxia at higher altitudes, end-tidal CO2 will decrease as a result of hyperventilation, but this is not an issue at normal cabin altitude unless lung function is abnormal to begin with, and is negated by adding inspired oxygen. Side-stream capnography is susceptible to water in sample tubes and machines using this system are not usually designed for anything other than short transfers. The pumps used in these systems often consume a lot of power. Mainstream measurement is practical, but also uses considerable power which needs to be allowed for and adds weight to tracheal tube connections. Although a recommendation for minimal monitoring, in the critically ill the discrepancies which occur because of alveolar–arterial differences, high positive end expiratory pressure and reduced cardiac output may reduce this monitor to a sophisticated disconnection detector. When power is a consideration for a monitor, regular measurement of arterial blood gases is a better option, provided other disconnect alarms are adequate. Depending on their design some ventilators will monitor ambient pressure and compensate for changes in gas density and viscosity that occur with changes in altitude. With others manual compensation must be made. On volume preset ventilators delivered tidal volumes will be less than set tidal volumes unless these compensations are undertaken in ventilators with compressors or turbines supplying air to the system. Gas-driven constant flow generators will be less susceptible to these effects because of the high pressure driving gas for their fluidic circuits, but the lower partial pressure of entrained air for the inspired gas will affect tidal volume and minute ventilation. To avoid these issues close monitoring of these variables must be undertaken. The characteristics of equipment must be understood before it is taken into the air and it must also be monitored continuously in flight. Change in pressure affects equipment and components which contain air. As ambient pressure is reduced bubbles may expand in fluids within monitoring transducers and cause dampening of arterial or venous pressure waves leading to inaccurate readings. Meticulous removal of air will avoid this. Most fluids contain some dissolved gas which will come out of solution at altitude and will form bubbles which may coalesce and present further hazard. In this situation the use of air detection monitoring in fluid delivery systems and the use of air traps is of value. Air traps have to be watched closely as their volume may increase and allow air into lines if not adjusted correctly. Balloons on catheters in the pulmonary circulation present a potential problem if they expand. Deflating them and reviewing the need for these devices reduces the hazard. Monitoring and support equipment also have items such as touch control pads which contain air and may be vulnerable to pressure change. Equipment itself is not usually air tight, but transport containers may be and
Monitoring in the field
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generation of multiple artifacts. In these conditions alarms may be activated inappropriately. In view of the inability to rely on clinical signs and the paradox that machine-monitored variables are of greater importance yet potentially unreliable presents a dilemma. To overcome this, enhanced monitoring must be undertaken and measures taken to ensure the accuracy of what is actually measured. The limitations of oximetry in the critically ill are well known. Research into specific effects of altitude has been limited to the static simulated environment, with low numbers of patients being studied, but there are suggestions of reduced accuracy of pulse oximetry.17 In practice the effect of vibration may be significant, but new technologies may help to overcome the effects of motion artifact.3 16 The effects of coarse and fine vibration generated by aircraft have not been studied on this type of monitor as far as the author is aware. To avoid effects the sites where probes are attached should be padded and restrained to avoid movement if at all practical. In this environment measurement of arterial blood gases remains the gold standard and should be undertaken where any doubt of accuracy exists. It is also advised that for the critically ill, where oximetry is often of limited value, arterial blood gases are measured before and after transferring to a transport ventilator, if the ventilator settings are changed in transfer or if there is suspicion that the condition of the patient has changed. Even if there are no apparent changes the gases should be checked at least every hour in transit, as is the practice in the intensive care. Hand-held devices are commercially available to measure blood gases and other variables. These devices use a small sample of blood which is injected into a cartridge containing reagents. This is then read by the hand-held device. The operating range for barometric pressure, humidity and temperature limited, but are wide enough for use in most circumstances. The limitations of space and lighting within the aircraft environment may impair visibility. As with the other environmental considerations, some aircraft provide better conditions than others. In these conditions certain types of display on monitors are difficult to see in low light or from acute angles and bright sunlight can render monitor screens unreadable. At night aircraft lights are routinely dimmed on take-off and landing. In the military environment, some missions require that internal red light is used before landing to accustom the crew to low light conditions outside the aircraft. On other missions when the aircrew are using night vision equipment all light sources are extinguished. In these circumstances there may be a complete blackout for a number of hours before landing. There have been occasions where subsequent unloading of equipment and loading of the patient have been undertaken in complete darkness as well. This is then followed by flight in the same conditions of blackout. To reduce the effect of inertial forces and vibration, impact resistant and absorbent foam materials are
require to be vented. Some equipment may have to be modified to avoid problems with specific components. The disposable items used with clinical monitors must be packaged to maintain their integrity and avoid contamination. The packaging contains gas and may be damaged as they expand at altitude and must be carefully inspected before the item is used. Finally, aircraft ascend and descend reasonably rapidly, so ambient pressure, temperature, and as a consequence relative humidity may change quickly. Drop and topple tests are required for medical equipment to obtain the compulsory ‘Conformite Europe´ene’ marking.7 There are also standards relating to resistance to forces with the carriage of equipment in land-based ambulances.1 For air carriage the standards are more rigorous and equipment carried by air must be able to resist damage during the three-dimensional inertial forces which are encountered during normal flight while continuing to function. In the event of an accident to prevent secondary damage, casings must remain intact and not break from restraints. These regulations apply equally to any packaging used to protect the equipment on an outward journey, and during the transfer with the patient. Solutions which provide protection against vibration have assisted in complying with these regulations. Noise is a problem in many vehicles, but it is a particular problem with aircraft. It poses health and safety hazards to the patient and attending staff and interferes with communication. It is a greater problem in rotary wing, small aircraft and larger military aircraft, designed for the transport of freight. The disorientation caused by constant loud noise with varying frequencies compounds the lack of normal feedback from familiar sounds. Increasing the volume of alarms may assist, but it is often negated by protective equipment and communication headsets. Further developments in alarm technology may be of value, such as linked, graded alerts which can be fed into the headsets worn by the clinical staff. Equipment not specifically designed to be used in this environment may be unexpectedly disrupted for other reasons such as batteries or attachments being dislodged. During the vibration testing of equipment used by the RAF, for example, the battery pack of a monitor became displaced and the monitor failed testing. To solve the problem the battery compartment was modified. In extreme vibration monitoring of infusions must be controlled by mechanical devices as manually timing a drip may be impossible. Clinical monitoring such as palpating the pulse, measuring blood pressure, viewing respiratory patterns and seeing colour changes is often difficult or impossible in aircraft. This is because of reduced or altered lighting, noise and vibration. Additionally an aircraft is mobile in three dimensions and exerts inertial forces on the crew, patient and equipment. In these circumstances monitors also may become unreliable. Variables such as ECG, non-invasive blood pressure and pulse oximetry are subject to the
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devices in the proximity, which may be generating electrical or magnetic emissions. Radiated emissions are the electromagnetic outputs which inadvertently occur because of the passage of electrical current through components and cables within devices. These emissions may be constant or may produce spikes of output, such as those associated with the discharge of a defibrillator. Emissions vary with different modes of operation and the electrical loads applied to the device. They vary with the particular power supply being used and when switching between multiple power supplies. Conducted emissions are those which feedback through cables during operation of a device. These may lead to emissions affecting other equipment through the power supply. The device may also be sensitive to conducted emissions attributable to the activity of other equipment attached to the same power supply. This sensitivity may be exposed when switching inductive loads produces electrical spikes. Signal cables are also susceptible to conducted emissions. To reduce these effects to acceptable levels or stop them altogether requires attention to build quality and proper testing to identify modifications which may be required. The casing enclosing electrical equipment must be highly conductive and any joints in the casing must be electrically tight and also highly conductive. Screw holes in casings can be protected by using conductive washers. Components within the casing can be electrically designed to reduce output spikes when operating and specific shielding may be applied to certain components if this cannot be done. Electrical filters can be applied to monitoring and power cables and external connections can be constructed to avoid electrical leaks. The production of EMI is possible from any electrical device, no matter how small and is not confined to devices that contain radio transmitters. This is because any component which has current flow has an associated electrical field and is a potential source of interference. These emissions may escape from equipment casings, but they are particularly associated with screens and cables. For example, in a recent incident, an incorrectly configured monitor was tested and the screen output was in the order of 100 times that of an actively scanning mobile telephone. Cables that carry power to equipment or link the equipment to the patient (signal cables) can radiate emissions, acting as aerials. Mobile telephones and portable radio handsets provide an example of portable communications equipment which can cause problems with medical devices, including monitors. Mobile telephones produce significant radiated emissions as they scan and transmit, even when a call is not being made. This can interfere with nearby electrical equipment producing untoward effects on displays and can affect the accuracy or function of equipment. As a result there have been adverse event warnings by the Medical Devices Agency, now part of the Medicines and Healthcare products
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incorporated into modified equipment. Locking washers and mounting components on isolating fixtures also contribute to attenuating these effects. Some equipment is fitted with additional padding within restraint packaging. To aid visibility, high-definition colour screens, with wide viewing angles are used. If the screen can be configured it is an advantage, as being able to flip the display adds to flexibility in positioning monitors. In enforced low light conditions, monitoring displays may be dimmed or shielded with variably opaque covers. The equipment, including the attached patient interfaces, used to monitor in the field may be categorized according to function, type or role. From the engineering perspective it may be either mechanical, electrical or a mixture of both. Mechanical devices within monitors, such as pumps for gas analysis or non-invasive blood pressure are susceptible to contamination and must be protected by appropriate filters. Fans for cooling computer processors also draw contaminants into equipment and require protection with filters. To deal with extremes of temperature insulation or larger heat sinks may be applied to components. Electrical devices require further consideration as their specification may require other modification. In the field there are many factors influencing monitoring outside the control of the operators. Those relating to climate have been alluded to above. Some are peculiar to the military environment, but may become more important in the increasingly technologically complex environment in which civilian practice occurs. For example, there may be powerful communications equipment nearby or aircraft operating in close proximity. Problems can also be associated with transmitters with High Performance Radio Local Area Networks or Terrestrial Trunked Radio Systems.29 While these factors do not often lead to overt difficulties they can occasionally have untoward effects, by producing induced currents in nearby monitoring equipment. The same situation occurs with mobile phones, but military transmitters may be orders of magnitude more powerful. In modern warfare, weapons specifically designed to interfere with electronic equipment have been deployed and will undoubtedly be used again. These weapons include electromagnetic pulse (EMP) weapons11 24 which are designated as non-lethal in normal circumstances, but would create lifethreatening situations to patients in the hospital environment. They were developed after the discovery of the EMP phenomenon, while studying the effects of nuclear weapons.6 13 The screens, computer processors, transformers and other electrical components of critical care monitoring devices may produce significant EMI or electromagnetic compatibility (EMC) problems. EMI is the effect on other equipment, in the proximity of a device which interferes with normal function of that equipment. This adverse influence is attributable to the electrical or magnetic emissions that are transmitted from it. EMC is the susceptibility of a device to interference and abnormal function caused by electrical
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This has been superseded by the Airworthy Medical Equipment (AME) test programme. This testing began in the 1980s to ensure that all medical equipment carried on RAF aircraft was compliant with relevant standards and regulations. It also addressed the issue of potential interference of aircraft systems on medical equipment. In addition to EMC, AME testing considers the overall survivability of equipment in aircraft. Examples of the variables tested are in Table 4. There are absolute requirements to test variables such as the effects of sudden or explosive decompression or the effects of changes in gravitational forces in a simulated aircraft environment. Despite this requirement, pragmatism still demands certain compromises. For example, testing to assess waterproof characteristics is acceptable to assess the effects of liquid splash as immersing equipment completely is clearly outside normal use. Taking the test to an inappropriate level unnecessarily increases the cost of producing equipment and does not increase flight safety. If equipment is to be connected to aircraft power supplies, more rigorous testing is required to assess the effect of conductive emissions. More demands are made if rectifiers, inverters or transformers are used to convert the aircraft supply from 115 V and 400 Hz to either a DC voltage of a different frequency and voltage of AC power. To avoid this extra cost batteries as internal or external power supplies are often used instead. They also provide self-sufficiency if aircraft power is not available. The cost of testing equipment may be as much as £20k per item and this is not insignificant if low cost items are required to have the full range of tests. To simplify matters and to still satisfy the aircraft authorities a Generic Specification12 of equipment to support patients in the air was produced. As a result of this, as Table 4 Test variables Test variables Electromagnetic compatibility Conducted emissions Radiated susceptibility Conducted susceptibility (low frequency) Conducted susceptibility (high frequency) Electrostatic discharge Shock, drop and topple survivability Altitude Sudden decompression Explosive decompression Vibration Acceleration (crash conditions) Humidity Mould growth Salt corrosion Fluid contamination Waterproofness Temperature Sand and dustproofing Requirements of aircraft design and technical authorities: aircraft electrical and mechanical interface requirements Other regulations
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Regulatory Agency (MHRA).8 9 For this reason their use in hospitals has been restricted. Updates from the MHRA have attempted to rationalize advice18 19 on the use of any communications devices, but despite these documents, confusion still remains. Electromagnetic radiation may affect monitoring equipment, but also equipment used by the transfer team has the potential to create interference which will cause problems with an aircraft’s electronics. The use of mobile telephones on aircraft is completely prohibited because of concerns that they may interfere with critical systems such as flight controls and navigation. Conductive or radiated emissions may be significant from any of the equipment used to support a patient. Laptop computers have also been implicated in interfering with aircraft navigation systems.26 Modern medical support equipment and in particular monitoring have screens in addition to containing the electrical components already discussed. Airline cabin attendants routinely direct that certain types of electronic equipment are switched off during take-off and landing. This is to reduce the potential effects these devices may have at these crucial times. In military aircraft device emissions may be detected and electronic countermeasures initiated. This may trigger the inappropriate release of chaff (strips of metal, foil or glass fibre with metal content used to reflect electromagnetic energy) and flares from an armed aircraft. In flight the flight crew will also undertake immediate evasive manoeuvres for obvious reasons. Sudden changes in aircraft attitude may cause injury to passengers or medical team members and patients. On the ground the release of countermeasures may be extremely hazardous because of the nature of the released material and the proximity of other installations such as refuelling equipment. For this reason Aircraft Authorities of NATO have tight controls over the electromagnetic characteristics of devices used in military aircraft. These controls are embodied in the Standard NATO Agreements (STANAGS) that lay out in detail, the levels of electrical and magnetic outputs which are acceptable within different aircraft types. There are also regulations pertaining to materials used in construction of equipment and for power supplies. This is important in the case of portable equipment, as some types of internal batteries can cause problems. Lithium ion batteries, common in many types of equipment, are actually categorized as dangerous air cargo as in certain circumstances they can explode. The connection to aircraft power supplies is a further issue because of radiated conducted emissions. Aircraft Authorities such as the Civil Aviation Authority have regulations that deal with the carriage of equipment in addition to that integral to the aircraft. These regulations also cover equipment which is not related to and may potentially interfere with aircraft function. At present restrictions relating to medical equipment are such that ‘carry on’ equipment is usually exempt. For the RAF, equipment testing was undertaken as the Special Purpose Medical Equipment testing programme.
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compromise their safety. With such a device it is often necessary to sedate a patient inappropriately and use neuromuscular blocking agents that would not normally be required. This should demand additional monitoring for the ventilator and the use of a peripheral nerve stimulator as there are also greater concerns regarding disconnections or awareness when a patient is not spontaneously breathing. In practice the simple transfer ventilator has less monitoring and few individuals use the additional monitoring that they should have in this situation. A more capable ventilator, with the required monitoring avoids compromise. Aeromedical transfer of critically ill patients is one of the most demanding areas of medicine and should only be undertaken by those who are specifically trained and equipped.20 This reduces the risk to the patient and stress on personnel. An equipment training course was specifically designed for RAF personnel undertaking critical care aeromedical duties. This Critical Care Air Support Team Equipment training was designed to provide team members with a complete educational package on the equipment they use during transfer. It is undertaken within the ICU setting to maintain relevance and to allow for consolidation of knowledge. The training is assessed by examination and when personnel complete the course they understand in detail the normal function and idiosyncrasies of their equipment. Practitioners routinely respond to alarms and alerts which may occur during patient care. They appraise the situation, using other variables, to assess the significance of these warnings. They are also aware of the subtle indicators of normal function that are in the background. With experience these become familiar and can be a significant adjunct to monitoring. Trained and experienced practitioners may be alerted to potential problems before alarms trigger and will be able to act accordingly. For example, noting the change in sound as a ventilator becomes disconnected. Here the experienced practitioner would respond before disconnection alarms were triggered and well before a change in the patient’s vital signs triggered alarms. The final element of training is therefore practice and hence experience.
Organization and training Human factors are extremely important in the field as it is a high-stress environment. If the human factors are not addressed, regardless of how effective the monitors are, there will be a failure to recognize abnormalities and no action will be taken.31 There is little or no peer support in austere isolated locations and it is impractical to have the user and maintenance manuals for all of the devices used. The use of portable electronic storage may assist with the latter, but in theory such devices require testing for use in the air, and the equipment itself. Full discussion of human factors is not appropriate in the context of clinical monitoring alone, but is relevant to the complete delivery of care.4 10 15 30 Organization and high-quality training (Fig. 5) are the key to success in the field,5 provided the equipment meets the criteria outlined in this review. Each item must be understood in detail to avoid making fundamental errors regarding capability, function, mode selection and alarm indications. The commonest mistakes made during transfers are overestimating battery life and misunderstanding mode settings.27 Monitors of these variables must be accurate, user-friendly and understood. Detailed training also does much to reduce errors of and allows standards to be properly assessed and maintained. Training also leads to a greater understanding of the care that is possible in the field. Accepting functionally inferior machines adds risk to the patient or negates previous progress that the patient has made. For example, using a so-called simple transfer ventilator when transferring a patient, or using it as a field ICU ventilator, will potentially
Conclusion Effective monitoring in the field demands the appreciation of a number of factors. It depends on having an understanding of the rigours of the environment and a thorough knowledge of the capabilities and limitations of devices being used. Personnel must be properly trained to survive and function in the environment, as well as be able to care for and protect their patients. This requires that they are current in clinical practice and have undertaken a detailed training. Meeting these requirements reduces the risk to patients and personnel and allows for advanced patient care in the field. The feedback loop is completed when experienced and well-trained practitioners constantly
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new equipment is required the general performance characteristics are already known. This enables the engineering authorities to evaluate the most cost-effective solution, while providing all of the functions for optimal care, demanded of the operators. Other issues such as ease of maintenance are also taken into account. As an added benefit the Generic Specification provides manufacturers with the opportunity to view what is expected of equipment when undertaking future research and development. This rational approach has saved much time and reduced costs while maintaining the highest standards. All equipment, including monitoring equipment, needs to be maintained to the highest levels and this requires adhering to the most rigorous schedule recommended by the manufacturer, or in some cases, these standards need to be exceeded. All equipment has up-to-date servicing before being transferred to the field and it is checked again before being brought into use. In the case of equipment used for patient transfers it must also have had appropriate user checks before a mission. It is more appropriate that the team using the equipment is responsible for servicing and user checks as they have ownership of any subsequent problems.
Monitoring in the field
Capability requirement
Training needs analysis
Entry level professional training
Generic training
Aircraft equipment Dunker drills Dinghy drills Smoke drills Aircraft safety Aircraft familiarisation Winch training
Examination Theory Practical
Clinical consolidation Mentorship
Equipment Theory Practical Transfer medicine Infectious diseases Monitoring Ventilation Law and ethics Health and safety Standards Aviation medicine Inter hospital transfers Intra hospital transfers Fitness to fly
Workshops and practical experience
Relevant clinical practice
CEPD
Practitioner: capable, current, credible, confident (defensible) Fig 5 Training practitioners for critical care aeromedical support team roles in the RAF. CEPD, continuing education and professional development.
3 Barker SJ. ‘Motion-resistant’ pulse oximetry: a comparison of new and old models. Anesth Analg 2002; 95: 967–72 4 The British Military Surgery Pocket Book. Crown Copyright, 2004 5 Borthwick M, McGuire NM, Scott D. How to prepare for the unexpected. Pharm J 2005; 275: 141–2 6 Chronister RD et al. Nuclear Hardness Test Planning Guide for Program Managers. DNA-H-90-140, 1993. Available from http:// www.dtra.mil/toolbox/directorates/td/programs/rtfc/defin.cfm 7 Council Directive 93/68/EEC of 22 July 1993. Available from http://www.ce-marking.org/directive-9368eec-ce-marking. html 8 Emergency service radios and mobile data terminals: compatibility problems with medical devices. Device Bulletin 1999 (02). Medical Devices Agency publication, 1999. Available from http://www. mhra.go.uk 9 Electromagnetic Compatibility of Medical Devices with Mobile Communications. Device Bulletin 9702. Medical Devices Agency publication, 1997. Available from http://www.mhra.go.uk
monitor the situation and respond to problems identified, in a timely and appropriate way.
Acknowledgement The author is grateful to Dr D. Young, Clinical Director AICU, John Radcliffe Hospital Oxford, for his help and advice during the preparation of this manuscript.
References 1 Air, water and difficult terrain ambulances. Medical Devices interface requirements for the continuity of patient care. BS EN 13718-1: 2002. . Available from http://www.standardsdirect. org/standards/standards1/StandardsCatalogue24_view_11040. html 2 Army Medical Services Core Doctrine. D/AMD/113/18, 2000
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Leadership Teamwork Fitness Weapons Survival Security
Role specific training
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23 24
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26 27 28 29
30
31
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Anaesthetists of Great Britain and Ireland, Revised December 2000. Available from http://www.aagbi.org/guidelines.html Recommendations for the Transfer of Patients with Acute Head Injuries to Neurosurgical Units. The Neuroanaesthesia Society of Great Britain & Ireland and The Association of Anaesthetists of Great Britain and Ireland, 1996. Available from http://www.aagbi. org/pdf/26doc.pdf Scholl MD, Geshekter CL. The Zed Expedition: the world’s first air ambulance? J R Soc Med 1989; 82: 679–80 Schwartau W. Information Warfare—Cyberterroism: Protecting Your Personal Security in the Electronic Age. New York: Thunder’s Mouth Press, 1996 Spiers G. Resuscitation, riots and the police. New developments in ambulance resuscitation. Ambulance Services Institute Seminar, Telford, April 2006 Strauss B, Morgan GM. Everyday threats to aircraft safety. Issues Sci Technol, 2002/2003: 82–6 Thames Valley Critical Care Network. Working Party Transfer Surveys, 2003,2004 United Kingdom Joint Medical Doctrine. Joint Warfare Publication, 4.03 Update on Electromagnetic Compatibility of Medical Devices with Mobile Communications: TETRA (Terrestrial Trunked Radio System) and Outside media broadcasts from hospital premises. Safety Notice 2001 (06). Medical Device Alert. Medical Devices Agency, March 2001. Available from http://www.mhra. go.uk U.S. Army Center for Health Promotion and Preventive Medicine, Health Information Operations Division—Health Information, June 2004. Available from http://chppmwwwapgea.army.mil Young D. Does monitoring affect ICU outcome? Joint RCoA/BJA Symposium on Clinical Monitoring, March 15–16, 2006
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10 Field Marshal Lord Carver. Morale in battle—the medical and the military. J R Soc Med 1989; 82: 67–71 11 Fulghum D.A. EMP weapons lead race for non-lethal technology. Aviation Week and Space Technology 1993; 61 12 Generic Specification for Special Purpose Aeromedical Equipment (SPAME)—Final Issue 4. ERA Technology Report Feb 2006. Available from http://www.era.co.uk 13 Glasstone S, Dolan PJ. The Effects of Nuclear Weapons, 3rd Edn. U.S. Department of Defense and Department of Energy, 1977 14 Guidelines for the transport of the critically ill adult. Intensive Care Society, 2002. Available from http://www.ics.ac.uk 15 Jones N, Roberts P, Greenberg N. Peer-group risk assessment: a post-traumatic management strategy for hierarchical organizations. Occup Med (Lond) 2003; 53: 469–75 16 Jopling MW, Mannheimer PD, Bebout DE. Sensitivity and specificity performance during motion artefact in three pulse oximeters designed for use in motion. Annual Meeting Abstracts ASA, October 14–18, 2005 17 Mehm WJ, Dillard TA, Berg BW, Dooley JW, Rajagopal KR. Accuracy of oxyhemoglobin saturation monitors during simulated altitude exposure of men with chronic obstructive pulmonary disease. Aviat Space Environ Med 1991; 62: 418–21 18 Mobile communications interference. Medicines and Healthcare Products Regulatory Agency publication, 2005. Available from http://www.mhra.go.uk 19 New advice issued on the use of mobile phones in hospitals. Reference 2004/0287. Press Release, Medicines and Healthcare products Regulatory Agency, July 29, 2004. Available from http:// www.mhra.go.uk 20 Rainford DJ, Gradwell DP. Ernstings Aviation Medicine, 4th Edn, London: Hodder Arnold, 2006. 21 Recommendations for Standards of Monitoring During Anaesthesia and Recovery, 3rd Edn. The Association of