Care of long-term ventilator patients

Of o n 9 Vent ator ati nts by ButchTrego,RRT,RCP

pproximately 15,000 patients per day require some form of mechanical ventilation. Many patients only require short stays on ventilators whereas others require long-term ventilator assistance. This article focuses on patients who require long-term ventilation, and includes a description of the three types of long-term ventilator patients, weaning techniques, and transitioning patients who cannot be weaned to home care. Most patients who require long-term ventilation exhibit one of three characteristics: 9 Respiratory failure caused by end organ disease, such as chronic obstructive pulmonary disease (COPD), chronic bronchitis, and congestive heart faihtre

9 Respiratory failure secondary to mechanical failure, such as cervical level spinal cord injury or neuromuscular diseases like polio, multiple sclerosis, or Guillian-Barr6 syndrome 9 Respiratory failure caused by failure of the respiratory center in brain Although some characteristics and weaning techniques may be similar in all three categories, each has its own set of difficulties and will be examined separately.

Pulmonary COPDPatients First let's examine pulmonary or coronary disease patients. These patients usually present to the emergency room in moderate to severe respiratory disffess. Many respond favor-

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C'E~ ably to bronchodilator therapy while in the emergency room, and therefore are sent to a nursing unit or back home rather than to an ICU. But within 2 to 4 hours, many of them are found to be in similar if not more severe distress than their original presentation. The majority will need to be immediately intubated and placed onto mechanical ventilation. One method of assisting these patients through their exacerbation period is bidirectional intermittent positive airway pressure (BIPAP). BIPAP is a form of ventilatory assistance that uses two levels of continuous positive airway pressure (CPAP). CPAP places a positive force on the alveoli in the periphery of the lungs keeping the alveoli from collapsing. BIPAP uses the variance in pressures that occurs between inspiration and expiration as an equalizer to maintain a steady pressure level. BIPAP can be administered with or without oxygen, and can be delivered via mask, endotracheal tube (ET), or tracheostomy tube. BIPAP can assist patients' breathing and help them through short periods of exacerbation, but will not completely take over the function of breathing. When managing patients on mechanical ventilation, it is best to allow their muscles to completely relax for the first 24 to 48 hours. During this time they should be vigorously treated for the underlying cause of their exacerbation. It might take longer than 48 hours to resolve the cause, but letting them rest any longer will allow their muscles to begin to weaken. These patients should be made to do some of the work of breathing even though most of their breathing is being performed by the ventilator. Intensive weaning should be started as soon as the cause for the exacerbation has been resolved or conffolled. This doesn't mean the patients' treatments will be eliminated, but rather that the acute phase is over and they are ready to begin working their muscles again.

Patients With Absent Respiratory Muscle Innervation This form of respiratory failure has many causes. In this section, spinal cord injuries and a broad overview of progressive neuromuscular patients are reviewed. Let's start with an overview of the sites at which inspiratory and expiratory muscles innervate from the spinal cord. Most inspiratory muscles innervate from C3-8, with the diaphragm innervating at C3-5. The diaphragm is the main muscle of inspiration. The thoracic inspiratory muscles don't begin innervation until T1 and continue through T l l . The expiratory muscles, which actively assist in coughing, begin innervation at T1 and continue through L1. Many patients with a thoracic level spinal cord injury may be mechanically ventilated because they are unable to clear their secretions secondary to poor cough.

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Approximately 15,000 patients per day require some form of mechanicalventilation Let's examine weaning patient with a high-level spinal cord injury between C3-4 and C7-8. These patients have moderate to hill diaphragm innervation, no intercostal muscle innervation, and almost no coughing ability. No patients above the level of C2-3 will be able to be completely weaned from mechanical ventilation because they have only partial innervation of inspiratory muscles. Those muscles can only support breathing for so long before they fatigue and fail. The key to weaning a patient with a high-level spinal cord injury from a mechanical ventilator is large breaths (predicted vital capacity) and chest wall expansion (to keep the rib cage flexible). Patients injured at this level will lose most of their ffmctional residual capacity because they have no innervation to expiratory muscles (volume of air used in a forceflfl cough). For this reason, large breaths are needed to keep their lungs fully expanded and to keep atelectasis from developing. Most volume ventilators are unable to provide a large enough volume of air to fully expand the lungs on most patients with this type of spinal cord injury. Some pressure limited ventilators may be able to achieve a predicted vital capacity breath. A recommended practice is to deliver intermittent positivepressure breathing (IPPB) treatments to these patients using pressure of up to 40 cwp until their predicted vital capacity has been achieved. This can be done as often as needed; however, usually treatment is scheduled every 4 hours. When IPPB is used in conjunction with the previously detailed weaning practices, these patients can be weaned from a mechanical ventilator fairly quickly. Conlraindications to using high pressures on/PPB treatments are hemoptysis, recent or current chest tubes, asthma (although when used in conjunction with a bronchodilator, IPPB is generally safe), or rapid increase or decrease in blood pressure.

C'E'U Some patients with higher-level spinal cord injuries may benefit from alternative forms of ventilation, such as exsufflation belts, chest curasses, pneumosnits, and mask/mouthpiece ventilation combinations. As previously mentioned, patients with high-level spinal cord injuries have almost no cough. These patients need to be assistive coughed by using one of two methods--they can be coughed by using an abdominal thrust technique or a ptussive squeeze technique. The abdominal thrust technique is done by placing a hand sideways between the naval and the xiphoid process, having patients inhale on their own or using assistive inhalation with an IPPB machine or adult resuscitation bag, then forcefully pressing against their abdomen at the word "cough." A ptussive squeeze is performed by placing hands on both sides of the lower rib cage (around the floating ribs), having patient inhale as above and pressing inward at the word "cough." The technique for weaning patients with progressive neurologic respiratory failure differs from that for weaning patients with spinal cord injuries in that it must be achieved at a much slower pace. Typically respiratory failure will have a

sudden onset because the disease process shuts down partial or entire respiratory muscle innervation. Patients with progressive neurologic respiratory failure require a gradual approach to exercising their respiratory muscles. When weanIng these patients it is important not to overly slxess their respiratory muscles. Overworking them will cause respiratory failure. The weaning process is the same as previously described, but the pace is much slower, These patients may only be able to stay off ventilation for several hours during the day, then resume ventilation for nocturnal and/or intermittent rest during the day.

Patients With Respiratory Failure From Brain Injury Many patients need mechanical ventilation for one of two reasons. One is the result of aspiration pneumonia secondary to damaged swallow reflexes. The second may be caused by an injury or accident occurring in the brainstem that damages the center regulating respiration. In the case of aspiration pneumonia, most patients will need to be intubated with a tracheostomy tube. An ET tube will allow the pneumonia to resolve so the patient can be weaned from the ventilator. When the ET tube is removed, however, the airway protection

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C'E~ the cuff provided will be gone and aspiration will recur. Tracheostomy will allow these patients a secondary airway and a means of protecting their lungs while waiting to see if dysphagia clears. The weaning process for these patients will be the same as previously described as long as the cuffs on their tracheostomy tubes remain inflated. The test for aspiration is fairly simple. If the patient, before intubation or tracheostomy placement, has a persistent cough when drinking liquids or eating food, aspiration is likely. These patients should be given a dysphasiagram, an x-ray procedure in which different consistencies of barium are swallowed to see where the breakdown in the swallowing process is occurring. Another method is a fiberoptic endoscopic study, which visualizes the swallowing process through a fiberoptic scope run through the patient's nose into the oropharynx. In many cases, only certain consistencies of food or liquids cannot be tolerated, and a modified diet can be set up to allow patients to eat orally. If a tracheostomy tube is in place, a swallowing test with different consistencies of dyed foods is given to the patient to swallow. If any of these food are seen in the tracheostomy tube after a spontaneous or assisted cough, then a dysphsiagram or fiberoptic study is ordered. If there is an injury to the brainstem area, especially the pons, there is no specific treatment. Spontaneous respiration may occur and trials should be performed daily to monitor for this. These trials simply lower the set respiratory rate and watch for any signs of spontaneous respirations. Once spontaneous respirations are seen, weaning should begin as aggressively as the patient can tolerate. Many patients on ventilators can be transferred to a rehabilitation hospital or to a skilled nursing facility capable of handling this level of care. Many of these facilities can continue with weaning or fully wean the patient from mechanical ventilation. Along with ventilator weaning, these patients can simultaneously receive other therapy to help them improve their overall strength and function before they are discharged with less cost than remaining in an ICU or step-down unit.

WeaningTechniques There are two widely accepted methods of weaning patients. One is to place them in synchronous independent mandatory ventilation (SIMV) and reduce the SIMV rate. The other is to place them on CPAP with pressure support and reduce the pressure support. Either method seems to be effective in weaning these patients. Other forms of weaning are equally effective, but these two methods will be our focus. Weaning using SIMV rate reduction is performed as follows. When patients are in the SIMV mode, they are allowed to

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breath on their own as often as they like but are given synchronized machine breaths at a set number of breaths per minute. For example, if patients are on an SIMV rate of 8, they could be breathing 20 total breaths per minute, but 8 breaths would be machine breaths. Many types of ventilators will allow a bias flow of air to continuously flow through the circuit to reduce the amount of work needed to obtain a breath in between SIMV breaths. To wean these patients, the rate of SIMV breaths is slowly reduced until a level of two to four breaths per minute is reached. Patients then are either taken off the ventilator for short periods of time and placed onto a T-bar aerosol system, or they are placed onto CPAP on the ventilator. Patients may also be weaned using pressure support and CPAP. Patients are placed on CPAP at a level of pressure support needed to allow them to breath comfortably. Pressure support is a modality that gives patients a dialed pressure breath for the first 75% of their own triggered breath and tapers off at the end of each breath. Pressure support can be dialed up to 30 to 35 cwp. Rates above that level can cause barotrauma, and weaning should be delayed. Weaning from pressure support is essentially the same as from SIMV, in which the pressure support is reduced until the patient can tolerate it. Once a pressure support level of four to six is reached, pressure support can be discontinued and the patient can be placed on T-bar or CPAP.

Monitoring The WeaningProcess Methods of measuring the patient's tolerance of the weaning include respiratory rate, tidal volume, and rapid shallow breathing index (RSBI). The respiratory rates should be between 10 and 25 breaths per minute. Generally respiratory rates greater than 25 breaths per minute cause too much work to the respiratory muscles for successful weaning. Tidal volume (the amount of air in liters per minute the patient is breathing each breath) should be set large enough for the patient to achieve an adequate minute volume (the amount of air breathed per minute). The respiratory rate and the tidal volume are multiplied together to calculate minute volume. For example, a tidal volume of 400 ml or .4 L and a respiratory rate of 20 breaths per minute would give you a minute volume of 8 L/min. The amount of minute volume is determined by the age, size, and weight of the patient. RSBI is calculated by dividing the respiratory rate by the tidal volume in liters per minute. This test must be performed while the patient is breathing spontaneously for 60 seconds. Values of 100 or greater are considered poor for weaning. If we use the example of 20 breaths per minute and divide it by .4 L, we achieve an index of 50. This would be desirable for weaning. Some external monitors can provide valuable information on how well the patient is tolerating the weaning process. The

C'E'U oxygen saturation monitor is good for determining how well the patient is being oxygenated. Some oxygen saturation monitors are built into the microprocessor of the ventilator. An oxygen saturation monitor is not as reliable as an arterial blood gas monitor and the results, if questionable, should be backed up by arterial blood gas monitoring. A good saturation level is 90% or greater. A CO2 monitor is another useful tool to monitor weaning. The newer monitors have a close reliable correlation between CO2 exhaled and PaCO2. The CO2 monitor range should be between 35 to 45 mm Hg. An esophageal balloon monitor is a useful tool to measure work of breathing. When the balloon is inflated, it measures esophageal pressures, which accurately reflect transthoracic pressures. When weaning parameters are changed, a reading should be done 15 to 30 minutes afterward to assess how well the changes are being tolerated. By using the calculated and monitored values to guide the weaning process, the patient should be weaned in a reasonable amount of time. It is difficult to define a specific time frame because patients tolerate weaning differently. It is appropriate for laboratory studies to monitor oxygen-carrying capacity, white blood cell count, and an arterial blood gas to monitor gas exchange. Many other laboratory tests may be ordered depending on the cause of respiratory failure. If results of any of the basic laboratory tests are significantly abnormal, weaning will be increasingly difficult, if it is possible at all. Medications that can delay weaning are sedatives when used in excess. Many times the patient's agitation comes from not being able to get enough air from the ventilator. In this case, the flow rate and flow patterns or the modality in which the breaths are being delivered may need to be changed. If sedatives must be used, they should be short-acting and in small amounts as needed to achieve sedation.

Home Care For The Ventilator Patient In any of the three mentioned categories, there will be patients who cannot be weaned. These patients may be set up on a portable home ventilation system. The transfer from a bedside hospital ventilator to a portable home ventilator should be easily tolerated by the patient.

if necessary, modified to be more accessible to the patient. Doorways, bathrooms, and bedrooms may need to be enlarged to accommodate the wheelchair, breathing treatment equipment, suction equipment, and possible oxygen equipment. A wheelchair capable of handling the patients' weight as well as their portable ventilator and battery (standard wheelchairs have a maximum weight capacity of 250 lbs.) must also be ordered before discharge. Caregivers may also consider a wheelchair-accessible van for transporting the patient. When deciding whether to buy or lease a portable ventilator, leasing is the preferred option. Portable ventilators need to be serviced and maintained about every 10,000 hours (some will need maintenance more frequently, others less). The cost of maintenance is between $700 and $1500 plus the cost of shipping it to and from manufacturer or distributor. If there is a problem with the ventilator, the company leasing the ventilator to you will bring a replacement to the patient instead of waiting for a replacement ventilator to arrive from the manufacturer or distributor. If you decide to purchase the ventilator, a maintenance agreement is strongly suggested. Purchasing two ventilators is strongly recommended for times when one unit is not operating or is in need of maintenance.

Conclusion At Baylor Institute for Rehabilitation more than 95% of patients admitted on a ventilator have been weaned. The patients who have not been weaned have been either those with spinal cord injury at the level of C2-3, patients who have had neuromuscular diseases (such as polio) or those with extreme health problems that complicated the weaning process. For these patients, a great deal of training and education for the family member is given to successfully transfer patients from hospital to home.

Butch Trego, RRT, RCP, is Director of Respiratory Care at Baylor Institute for Rehabilitation at Gaston Episcopal Hospital.

Bringing a ventilator patient home will require the primary caregivers to undergo extensive training. They will need to know how to troubleshoot the ventilator for mechanical problems, adjust the ventilator if settings are accidentally altered, deliver bronchodilator treatments, suction the patient, change and clean ventilator and breathing treatment circuits, and monitor warning signs of impending respiratory problems. Other factors besides placing the patient onto this portable system must be addressed. The home must be evaluated and,

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