Future directions for resuscitation research. II. External cardiopulmonary resuscitation basic life support

resuscitation

Resuscitation 32 (1996) 63-75

Future directions for resuscitation research. II. External cardiopulmonary resuscitation basic life support ’ Nicholas Bircher”, Charles Ottob, Charles Babbsc, Allan Braslpwd, Ahmed Idris”, Jean-Peter Keilf, William Kaye’, John Laneh, Tohru Morioka’, Wolfgang I&se”, Lars Wik’ ‘(Moderaror) Sofar Centerfor Resuscitation Research, Universiry of Pittsburgh. Pidurgh, b(Ca-maakra~or). Tucson,AZ, USA cLufayette, IN, USA dAlexandria, VA, USA ‘Miami, FL, USA ‘Magdeburg. Germany Wrovidence, RI, USA bCampinas,Brazil iKumomoto, Japan jOdo, Norway

PA, USA

Received 14 October 1995; revision received 20 November 1995;accepted 20 November 1995

In suddencardiac deaths outside hospitals, the present performance of external cardiopulmonary resuscitation-basic life support (CPR-BLS), as a bridge to advanced life support (ALS) attempts for restoration of sp@ntan#o%% eimtkttion (ROW), still yields suboptimal results. Therefore, future education research should develop more e&W.ive, simpler and quicker ways to enable everyone to acquire the necessaryBLS skills. Individua%& self-traisiag by lay persons is be@ revived. Although airway control and direct mouth-to-mouth ventilation skills am dif%ult to ae&re, they fri&nd$ wham must continue to be taught to the lay public and health professionals, prim&y for use OD Thebestway inFectiosriskinotaproblem.Inchildrenand~~victims,stepsAaadB~Qaay to ventilate and oxygenate during the initiation of brief external CPR-BLS should be re-eval~ti. There is a #e@t for added positive pressure ventilation, During chest compressions in humans, steps A and B are deservemevahmtion. The low perfusion pressures(borderline blood flows) produced by standard external CPR remain the most serious limitation of this method. In spite of extensive efforts so far, novel iaboratory researchto remedy Ackltcssa/l cowespoadenceto: Peter Safar, M.D., SCRR, University of Pittsburgh, 3434Fifth Avenue, Pittsburgh, PA ! 5260,USA. Tel.: 412 624 6735; Fax: 412 624 0943. K&xi by: Peter Safar, Uwe Ebmeyer and Laurence Katz, Safer Center for Resuscitation Research,University of Pittsburgh, PA, USA. ‘From a discus&n at the International Resuscitation Research Conference of May 1994at the University of Pittsburgh. For introduction and other topics of this conference, set the journal Criricol Care Medicine, supplement of February 1996. 0300-9572@6/515.000 1996Eisevier Science Ireland Ltd. All rights reserved SSDi OXtO-9572(95)00935-M

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this limitation is important for the development of more effective emergencyartificial circulation. The results of such studiesare greatly influenced by different details in animal models. Active compression-decompression(ACD) external CPR, also called ‘push-pull’ CPR, with a plunger-type device used by hand or a machine, and intermittent abdominal compression(IAC) external CPR are both promising moditications of standard external CPR. Both needfurther experimental and clinical claritkation. For BLS, developing a more effective purely manual CPR-BLS method for help in rapid ROSC should be given high priority. Portable external CPR machines need improvements. They will serve for bridging ROSGresistant casesthrough transport and ALS attempts, primarily by freeing the hands of health professionals for more effective sophisticated ALS measures. Keyworc!r:Airway; Artificial circulation; Artificial ventilation; Basic life support; Cardiac arrest; Cardiopulmonary resuscitation; Emergency care; First aid; Hypoperfusion; Mouth-to-mouth breathing

1. Introductioll Bircher

We will speakvery briefly in broad conceptual terms about some of the potential directions of research concerning external cardiopulmonary resuscitation-basiclife support (CPR-BLS). What is left to be known?How can we refinewhat we are doing in the laboratory to better predict what we are going to be able to offer patients? In that regard,important are not only experimentalmodels, but also researchand developmentrelated to better educating the general public and medical professionals. BLS is the first link in the chain of survival [l-3]. It is important to initiate CPR-BLS as early as possible,but it is not the only priority in terms of restarting the heart and optimixing outcome after cardiac arrest. Teaching someoneto recognize and to managecardiac arrest should also includecalling for competenthelp, that is calling for somebodywho knows how to restart the heart and has the equipmentto do so. Similarly, when you model CPR in the laboratory, it is important to actually measureoutcome [4-71. Rather than the assortmentof surrogate variables that are available to us, like vascular pressuresor coronary blood flow, it is important to actually restart the heart and determineto what degreeit remainsfunctional. It is alsoimportant to describein detail the experimentalmodel being used, including arrest interval, drugs, and other details of advancedlife support (ALS) to achieve

restoration of spontaneouscirculation (ROSC). For example,there are some physiologistswho honestly believe that sodium bicarbonate is an ‘anestheticdrug’, becausewhen they give an anesthetic they feel compelledto correct the pH with sodium bicarbonateto correct the ensuingacidosis. If the pre-insult preparation deranges the model so badly that the animal needs to be resuscitatedbefore starting an experiment, the measurements madewill not be very representative of the real-life situation. We havean ongoing needfor additional clinical measurementsin patients [3]. The documentation we haveobtainedwithin the context of large-scale randomizedclinical trials [8-lo] doesnot allow us to say very much about the quality of CPR being provided. The details of this reporting need to be refti. Finally, it is important for thoseof us who work in the laboratory to recognixethat unlike many of the animal models, individual steps in clinical resuscitationsdo not always get done instantly. For example,if a dog is aheady attachedto a cardiopulmonary bypass(CPB) machinein the laboratory, ALS measuresmay be taken at a rapid rate [ 111.Few patientscometo the emergencyroom already cannulated [ 121.Cycles of validation are necessaryas we go from the laboratory to patients and back to the laboratory. Ultimately, we needa similar cycle for educational studies to take an educationaltechnique or program to the general public. We have to ensure that we reach both educationaland therapeuticgoals.

N. Birder et al. /Resuscitation 32 (1996) 63-75

Otto

What are the questions on BLS that basic laboratory and clinical research need to answer over the next few years?We are taIking about a very applied type of research, that is you carefully design your studies, ask answerable questions, and determine an appropriate number of animals or patients. If your study is not powerful enough to answer the question, then it is not worth doing. where should we go with the ABCs of BLS? Let us start with step A, ‘airway control’ - Safar’s, Elam’s and Gordon’s studies in the 1950s have shown that steps A and B are important [13-191. Safar showed in comatosehumans that the tongue is falling back, which closes the airway and that even in the prone position, the airway can still be closed [13]. The problems are well-defined. Anesthesiologists have developed effective techniques to keep the airway open [1,20,21]; however, even anesthesiologistswho provide airway control everyday have learned that the techniques are not always simple and are not always effective [21]. Trying to take these techniques to the lay public is not simpIe. If there is an area that really needs more attention, it is airway management,which is often the most poorly performed CPR step [22]. A question is whether to get better models for people to practice on or to improve correct teaching methods. Concerning step B, ‘breathing control’, if airway is important, is artificial ventilation equally important? That is a question that has been ignored for 20 or 30 years and really needs to be readdressed. A number of surveys of health care professionals and others have confirmed that many people are reluctant to perform mouth-to-mouth resuscitation (231. Some have started to look again at whether and how important artificial ventilation is during CPR-BLS. Animal studies have suggested that step B might not be so important [24,25]. In pigs, during cardiac arrest, after closed-chest cardiac compressions without an endotracheal tube for 10 min, recovery was the same as in animals that received ventilation and standard CPR through an endotracheal tube for the same 10 min

WI. Safar (Appendix 1,4A), basedon his early work

65

in this area [13-161, b&eves strongly that pigs are not humans and that humans wiII not do as well. That may well be true. Perhaps our friends from the Netherlands are correct when they say we should be doing CAB instead of ABC [26,23]. CPR? what is the right way to v&late We do not know. We know that ve&I&iou influences arterial PC& Does it have any effect on mixed venous PCq? Does it have an effect on tissue acidosis? The interaction of blood flow and ventilation is an area that has urair ing external CPR, is it good into patients [14,28]? For BLS, I do not know an alternative. Concerning step C, ‘circulation support’, where do we go from here?Which alter&ative t&mique for chest compressions Let us look at standard chest compressionsin chmcaI &u&s. flurry of interest with the theories of biood flow in the 1980s[29] over how we do chest compressions - by ‘Thumper’, vest, high impulse, etc. methods. This enthusiasm seemsto have tapered off, except for looking at specifii types of CPR, such as intermittent abdominaI compressions(IAC) and active How we may account for some of the differences we are seeing in results. One example of why we seedi&rent results can be found in highdose In our laborato of uncontrolled ventricular fib find a di@brencebetween standard and h&&dose

dard settings. We were nary perfusion pmssures. Even without the alternative teclmiques, we need to look at how we are doing standard chest compressionsin humans and what gives us the best results. Use of Thumpers, which has become common in clinical situations

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for prolonged resuscitation attempts, may not be the best way to go about doing chest compressions. We need more data in humans and animals.

We must teach stepsA and B with direct mouthto-mouth ventilation to everyone [14,19,28]. You may need it at home or among friends. For children, mouth-to-mouth breathing, not defibrillation is the principle resuscitation method. In the third world, with about 4 billion people, even maskswhich cost $10 each are too expensive. The few that are around may be stolen or disappear. Carrying a used tubing section worth less than $1 in your pocket would be practical. You insert the tube into one nostril, pinch the mouth and the other nostril, pull on the chin - all with one hand - and hold the outer end of the tube with the other hand, and blow. 2. Jzdueatlon reservcb Keil and Roese

The importance of bystanders in casesof cardiopulmonary arrest is indisputable [l-3,34]. We all know that BLS procedures include prompt recognition; call for help; and airway control, breathing and circulation support. The immediate delivery of CPR-BLS by bystandersand the early extension to ALS improve survival from cardiac arrest and reduce subsequentmorbidity [34,35]. That is why efforts should be made to train both health professionals and millions of lay people. Lay personscan learn CPR-BLS through standard courses [ 1,2,36]. For training the masses,however, current standard CPR courses are longer than necessary.Individualized self-gauged practice on manikins, coachedby pictures and audiotapes, has proven to be as effective as instructors’ courses [37-391. There are many problems in designing optimal BLS courses. Although most people can successfully learn to perform BLS, skill retention is universally poor. It is important to recognize the difference between practical skills and knowledge retention. For example, physicians and nurses have worse BLS retention than lay persons.

32 (1996) 63-75

We conducted a study (Appendix 1, 2A) in which we intended to combine acceptedand proven concepts with new possibilities of instruction to obtain a long-term effect and skill retention [40,41]. Intensive training techniques involving long courses of 6-8 h have resulted in improved skill retention in some cases.We feel that this is neither necessary nor practical. Attention of course participants lapsesafter about 40 min. This is the reason why we provided intensive training with a time frame of only 45 min and no more than 10 participants. We prefer to lecture in a more pragmatic way and to use a leaflet or short video tape, or to conduct a short demonstration on a manikin. A combination of all these seemsbest. The video is a sample of simulated accidents and demonstrations on a manikin. The video is shorter than 7 min, the whole theoretical part of the course is less than 15 min. The result is an increase in practical training time. It is our intention to motivate a rescuer to act in an emergency.All participants can train on their own manikin. The manikin is a skill meter and family trainer made by Laerdal. Sensoryinput and feedback about performance are necessary for learning CPR. Practice proved imperative for successful learning and retention in our study, as it did in previous education researchprojects on the teachability of CPR-BLS [36-391. Our course ends with a short discussion. To investigate the effectivenessof our courses, we conducted a prospective randomized trial which included 5 study groups with 50 young college students in each group. In addition to the training materials of a standard CPR course, the trainees received a leaflet, video and simple CPR manikin to take home for 6 months. All participants had to pass a skill test before and immediately after the CPR course, and again at 4 weeks and at 6 months. Skill acquisition after use of the video and home trainer was very good [40,41]. We concluded that skill retention can be high with short but exercise-intensive training. Since we studied university students with high motivation, further studies are neededwith more diverse populations and different ages.

N. Birder et al. /Resuscitation 32 (19%) 63-75

Wik In Norway, we performed a study in which we trained over 1080people at home with an informal 30-60 min practice. The teacher was either a spouseor another relative 1421.The study proved that lay people without any formal teaching experience are able to function as teachers at home when the students are friends and family. The study even documented that the home-trained group performed better CPR compared to a standard Red Cross course trained group. When talking about airway control, anesthesiologists get nervous when they hear messagesabout skipping ventilation. Steps A and B must be used in most comatoseor very sick patients, also those without cardiac arrest. The public must be taught to also take care of the airway for people in car accidents, falls and other emergencies. (ACD) CPR Morioka Manual active compression-decompression (ACD) CPR was introduced for further evaluation in 1992 [43-48]. A hand-operated suction-piston device, the CardiopumpTM (Ambu Co.), for expanding the chest between sternal compressions, the 10th World Congress of in the Netherlands that year. I introduced this manual ACD method, which I call the ‘pushpull method of external CPR’ to Japan via television broadcasts ([48] and Appendix 1, 3A). Repeatedchest compressionswith conventional external CPR will gradually decreasethe functional residual capacity {FRC) of the lungs and produce microatebactases.The chest expansion (‘pull’ phase) of ACD-CPR will recover FRC and prevent the development of microatelectasesand the resulting pulmonary shunt effect. The push-pull method increases ventilation and venous return and may decrease the possibility of liver injury sometimes encounter4 with vigorous compression on the collapsed chest during conventional external CPR.

67

We tried use of the CardiopumpTM with a compression pmasure of

with tracheal tube withheld for 5 mm during each procedure. Al-

chest-pressurealone. After 5 min the push-pull method, the P&Q normal. With a tracheal tube in place, the IFPV of standard CPR may be reduced or omitted when using the push-pull method. This made onerescuer CPR easier and more practical. We also made smaller push-pull devices for children and neonates. A one-way valve for air escapewas added. Since the elasticity of the chest wall differs between persons, we gaugefrom the pump. A sternal of soft silioone rub&r was . base of the suction cup to prevent precordial skin injury by repeated compressions. During our initial animal experiments, the pushpull method had to be iuterrupted often becauseof air leakage through a space between the suction cup and the protruding sternum of the prevent air leakage, a skirt made of fiim mate&l was attached at the rim of the suction cup to prevent air leakage in lean patients with deep intercostal spaces. We studied cardiopulmomuy push-pull method in dogs a& pigs

pressureswere lower with which did not produce th pressions(high impulse CPR) sible with the standard method. Psu2 and pH, values were higher and P.&O2values were lower

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with the push-pull method. In intubated patients, tidal volumes were larger with the push-pull method than with chest compressions alone. Neither the conventional nor the push-pull method is applicable for patients during transportation on a litter. We are developing a push-pull device driven with a battery activated piston, fixed on a precordial metal frame [49]. Our push-pull device also has equipment for airway control. In the presenceof trained personnel, tracheal intubation is available and recommended. Ambulance paramedicsin Japan are not yet allowed to use tracheal intubation. For their use, there is an oropharyngeal airway attached. The pushpull method should be promoted for use in hospitals and by mobile ICU teams (emergencymedical technicians), and then perhaps even by the public. Although the cardiopump is still expensive in Japan, it will become inexpensive if it becomes popular. The push-pull method will not reduce the importance of conventional CPR. The push-pull method, however, is too effective to be neglected. Uncontrolled clinical use has resulted in many anecdotal successes,even a case of spontaneous defibrillation. Wik Published laboratory studies show that ACDCPR may be more effective than standard external CPR [43-541. The most important tools for CPR, however, are our two hands. It does not matter how much equipment you bring, unless it frees your hands and can then increasethe level of effectiveness.Indications for manual CPR are obvious. Standard external CPR is very tiring, particularly when we have to perform compressions for more than 1 h. We have, in hypothermia cases,performed chest compressionsfor 4 h and the victim walked out completely normal a few weeks later (K. Lexow, personal communication, the Norwegian accidental hypothermia study) [55]. Mechanical chest compressions and active decompressioncan be used as a standby after ROSC in caseof rearrest or after acute myocardial infarction. It can also be used as a support during severe bradycardia with hypotension. During manual

CPR you cannot concentrate on the intellectual part of resuscitation. A device which is easy to carry with you may also be helpful for use during transport. Mechanical CPR can also be used as a bridge to CPB or intra-aortic balloon pumping, or other ultra-advanced life support methods to come [6,11,12]. Two studies evaluated cerebral blood flow (CBF) during ACD-CPR (50,521.In one animal study, a mechanical device was used for ACDCPR (prototype by Ambu Co.) and for standard CPR [50]. We used a new mechanical electrically driven device (not yet available) designedfor laboratory animals, to perform both standard and ACD-CPR (‘Heartsaver 2000,’ Medreco Co., Norway) [53]. Mechanical ACD-CPR gave higher carotid blood flow and coronary perfusion pressure than mechanical standard external CPR. In pigs, end-tidal CO, with active ventilation by bagvalve-tube was the sameduring ACD-CPR as during standard CPR [53]. All our studies were with a tracheal tube and bag-valve unit, which allows inspiration to occur during sternal decompressions. ACD-CPR with tracheal tube in large animals and in humans could produce minute ventilation without additional IPPV, with IO/mm chest decompressions.Tidal volumes (lung expansion) were smaller than with IPPV. Esophageal pressure, reflecting intrathoracic pressure in our study, showed that we were able to achieve a 5-15 mmHg negative pressureinside the thorax with active decompressions.Manual ACD-CPR is tiring and there are some caseswhen it is impossible to usethe device; therefore, we must not forget to use our hands and brains. Paramedics practicing manual ACD, on a special ACD-CPR suitable manikin, had a greater tendency to follow each decompressionwith a lessvigorous sternal compression than when using compressions alone. I am frightened about trying to get this device out to everyone. We risk sending a messagethat you cannot do CPR without equipment, which is totally wrong! People can do very effective standard-external CPR without any equipment. We should restrict the use of push-pull devices to the ambulance and hospital, not give them to the lay public. We have to set the limit as to what lay people can do. The cost of devices and training is

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important. In Norway, the ACD device costs about $125. Some people do not go to CPR causes becausethey are too expensive.We should think about useof defibrillators and other devices by first responders(EMTs and firefighters).

adult lies betweenthe level of the uml&fcus and azisoftheaorta

Lane We are talking about a pump or mechanicaldevice used in the hospital or by paramedics.You also talked about the lay public using devicesto bypassthe problem of doing mouth-to-mouth resuscitation on unknown persons on the street. Wherewill limits be drawn on the use of devices outside the hospital?If the pump ends up in the handsof the public, how much training will be involved?What would the cost be?How can it work without the patient being intubated? I urge simplicity and no emphasison devicesfor BLS by lay pSOilS.

Babbs (Appendix 1, IA)

During the past century, a wide variety of investigat~rshavedocumented, both in animalsand in man, improved blood pressureand blood flow abovethe diaphragm when sometype of external compressionwas applied below the diaphragm in addition to conveutioual resuscitativemeasures. Rhythmic&y in&posed abdominal compressions (IAC) aaxn to provide evengreater hemodynamic benefit and substantially lessrisk than does continuous abdominal binding [56]. Both total flow and the distribution of flow to vital organs above the diaphragmare improved;while the chancesof liver entrapmeut and damageduring chest compression are reduced. Clinical results, now in severalhundred ts, show a dramatic doubling of pwfbsion presums and survivalin patients resuscitatedin the hospital, when the techniqueof mannal interpot& abdominal compression-CPR (IAC-CPR) is performed [Sal. Future researchinvolving multiple institutions will require standardi2ati~n of the manual technique for abdominal compression. If one’s goal is to maximhe direct aortic compressioq invoking the ‘abdominal pump’ mechanism, the best site for external compressionin an

exammattonof the aortic with straight arms extendedto rescuer’sright hand is positionedso the a~~~*~~~~,~*~~ tingt~d~f~.~~~~t~~t. The correct force of art [56]. This leftnique for selectiveaortic compression sent a further refimement of manipulation in resuscitation.If sue&a is used consistentlyin future trials, the Railpotential of IA&! outcomefollowing cardiacarresta& resuscitation may be revealed. 4. vm

What will be the substitutefor or modification of mouth-to-mouth ventilation in the uext S-10 years?I want to again remind t&t the results of cardiac resusc&tion in ttl%&kIare dismal. There have been only 24 couscioussurvivors.Ventilation for the infant is asimpo&ant as defibrillation for the adult. Wik

Concerningventilation, the As and Bs of CPRBLS are important not only for c&k arrest, but also for trauma victims. Methods to open the air-

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way should always be taught. Studies that show that chestcompressionsalone can maintain ventilation should be taken only for what the facts tell you. Safarhaspointed out sincethe 1950sthat animals have straight natural upper airways, while humans have ‘kinked’ natural upper airways, which invariably obstruct in coma in the absence of backward tilt of the head and/or jaw thrust [13-191. Animals or intubated patients might be ventilatedsomewhatwith chestcompressions,but this is not the casefor comatoseunintubated humans.Laboratory data should not be taken assup port to stop consideringventilation during CPR. I disagreewith suchrecommendations.Evenwith a trachealtube in place in humans$ith cardiac arrest,chestcompressionsalone moveminimal tidal volumesbelow FRC, and sometimesno ventilation when the lungs are congested[16]. Bircher

What should we tell peopleto do if they do not have a barrier device?Health care professionals obviouslyshould carry a mouth-to-mouth adjunct with them.This obviatessomeof the perceivedinfectionrisks. In the hospital,we are surroundedby expensiveequipment and ideally would not wind up doing direct mouth-to-mouth ventilation anyhow. What should we teach people who are not likely to have such equipment?The perception of risk may be enough to alter their behavior. This doesnot meanthat the perceivedrisk shouldcause us to changewhat we recommend.It is a legitimate recommendation,basedon what we know, to continue to teachand perform mouth-to-mouth ventilation. In so far as education goes, physicians know what is recommended,but they also know that this is not necessarilywhat they themselvesor others are going to do. That in itself should not causeus to modify the recommendations. We can try to modify the attitude without modifying the recommendation,simply by educating people about what to do when encountering a completestranger and about the minimal risk to their own health and safety. It is fair to say in termsof relativerisks and basedon what we know at this point, that your chancesof dying from contracting a fatal diseaseduring CPR are much less

than beingkilled by an aeroplanefalling out of the sky. This does not make us modify flight paths over large population areas. Braslow In the US, 70-80% of cardiac arrestshappenat home.Generally,the rescuerwill know the person and therefore the primary teaching should be direct mouth-to-mouth resuscitation.In the present curricula thereis a sectionon useof a pocket maskor other device.That is ahight to teach,however,it should not be pushedinto the forefront. Otto

The majority of peoplewe are talking about, on whom to perform CPR, are not drowning victims but victims of sudden cardiac death. For them, circulation is much more important than breathing. Thereis an anecdotefrom a Seattletelephone dispatcherwhere a caller asked, ‘Why is it that everytime I stop pressingon his chestto blow in his mouth he losesconsciousnessand everytime I start pumping on his chest again he opens his eyes?’ If advancedlife support with defibrillation and intubation is only 4-5 min away, it may be unimportant to ventilatefor those 4-5 min. If you are going to do 1 h of CPR, no one believesthat you do not haveto open the airway and perform effective ventilation.

In my understandingof the literature, I thought they went through this 30 years ago and demonstrated, through the works of &far and Gordon [16-19,571,that adequateventilation could not be accomplishedthrough chest compressionsalone. This is why they added ventilation to chestcompressions. Oneof the mostdifficult things to teachin terms of retention is airway control and ventilation [58]. I would like to commentin terms of the training issues.The study by Keil and Roese [40,41] is fascinatingbecausethey havereducedCPR training to the essence.It is always nice to hear about

N. Birder

et al. / Resuscitaiion 32 (19%) 63-75

a new way. It has been demonstrated many times that retention is poor 1581.Years ago we monitored several CPR classes with a traditional 4-h course with 2 manikins, lo-12 students, and 2 instructors [58]. The average time on the manikin was 8 min. Keil increased the time to 30 min per person with the manikin, and that seemsto be the answer. We should stop thinking about course lengths and concentrate solely on how much time on the manikin the student should have. With very inexpensive manikins available now, we can have one manikin per student [59]. The 45-min class sounds outrageous by AHA standards. We have gone from 16 h to 8 h to 4 h to 2 h to 45 min; however, that seemsto be the answer. Trainees must have more time developing their psychomotor skills, rather than the instructor spending time talking and the students waiting and watching

WI. Wik Safar has pointed out since the early 1960s [l&36-39] that there should not be such a limit as a fmed learning or practice time. This can be avoided by individ&.ized self-training with selfpractice coached by video tape or audio tape until perfection. This may or may not be checked out by an instructor. Self-training proved in some of the early education research projects more effective than fmed time instructors’ training [37-391.

71

airway remains m With the triple airway Safar [1,13-15,611, along positive pressureventilrttion w&h technique, the upptr airway remain unoccluded. The person tion would immediately have whether there was air flow Could we produce ventilati queswhile keeping theu without adjuncts, while provide tidal volumes? quately investigated yet. Morioka When considering emergency artifttil ventilation for a patient with AIDS, when no equipment is available, I would recomm& USCOfthCprODC, hip-lift back-pressuremethod by Ivy, rather than the Holger-Nielsen prone back-pressure arm-lift method (571. If the supine position is a prerequisite, I would use the Silvester supine chestpressure arm-lift method [62]. In tion the upper airway is kept asked if the airway is open, manual art&&l vent&ion. If we use the prone position and back-pressme and if the airway is kept open, there should be good ventilation provided. Wik

Zdris This is not trite. &far showed in the 1950sthat Safar and Gordon did extremely valuable experiments in the 1950sconcerning manual ventilation vs. mouth-to-mouth ventilation in unconscious, cumrimd humans [13-19,571. These researchers showed that ideally they could produce adequate tidal volumes and minute ventilation with the manual technique via the intubated airway 1571. The problem is that during unconsciousness without tracheal tube, the upper airway inevitably becomesobstructed [13-151, and only 25% of the subjects they studied had adequate tidal volumes generated during unconsciousness with manual techni&es. The sole advantage of mouth-tomouth ventilation is to ensure that the upper

and back-pressure arm-lift methods of artificial ventilation without tracheal tube, in curarized human volunteers, in the 195&r,he found that the relatively safestairway and tion was produoed with supine chest-pressurearmunder the shoulders so in a spontaneously tilted bar&ward position, or is

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so maintained by a second operator (571.!&far if a manual ventilation alternative is absohkiy wanted, the Brosch-Silvestermethod could also be modified.In addition to producing ventilation, re suggeststhat one could add somecirculation by following each arm raising with several sternal compressions,rather than only one compressionfor exhalation.The operator works from the vertex of the victim. A second operator, he feels, might even help with airway control by reachingtoward the headof the victim betweenthe legs of the ventilating-circulatingoperator [57]. fdS,

Morioka

Ventilation during external CPR is not only to give oxygenand removecarbon dioxide, but also to open up bronchi and alveoli. Using chestcompressionsalone will increasemicroatelectases.To preventthis, we need ventilation. Birder

With regardsto the airway and the CAB controversy,I want to remind you about dog experimentswe performedsomeyearsago [27]. We used room air, then VF and startedchestcompressions while keepingthe tracheal tube clampedto simulate obstruction of the natural airway. It took about 2 min beforeoxygendesaturationoccurred. Then, however,the desaturation was very rapid. Short-termventilation may not makemuch differenceif in suddencardiacdeath, the delay in ventilation is only 30 s with a CAB as comparedto the ABC technique;however, a permanent omission of airway and ventilation will havesignificantrisk. Downplaying its importance in lay training has significantnegativeimplications. The rate of chestcompressionshas always been questioned.It has changedover the past 15 years, even in what we are teaching lay persons and health professionals.Actual clinical performance dependson what people feel comfortable doing, how fast or how slow they are doing it. That might be somethingto reevaluate. Using chestcompressionmachines,what should the rate of compressionsbe?Which rate optimizes

heart filling as well as perfusion pressure?Slower rates may help optimixe hemodynamicvariables. Wik

In most published ACD-CPR studies, a frequencyof 6040 compressionsper min is used.We used IlO/minand measuredarterial and venous blood flow and gasesin pigs [53]. We do not know how much we should push and pull. We do not know how much decompressionshould be used. Whetherratesare 60 or 120per min is not very important if rescuersdo not start CPR promptly or at all.

I reviewedthe literature on the origins of the 152 and 51 ratio. It seemsbasedon dog studies by Harris and Safar [63]. I question whether we really know what optimal compression:ventilation rates and ratios should be in patients. The 15:2 ratio, based on performanceby an experienced CPR provider on a recording manikin, was found to be the least tiring 1641.Higher rates [65] or a greater compressionforce [66], which have been demonstratedto either increasecardiac output or yield higher end-tidal carbon dioxide levels,may be better.Now you are sayingthat sloweris better. Maybe it doesnot matter. One of the reasonswhy the AHA is downplaying rigid rates and ratios is becauseit does not matter. Ventilate a couple of timesslowly until the chestrisesand then push fast 10 or 15 times and alternate. Otto

We would like to offer a hypothesisfor the people who are actively investigatingthis. The negative intrathoracic pressurewith activedecompression may be alteredquite dramaticallyby the time the heart needsrefilling. The intravascular pressure gradient between the femoral vein and the right atrium during CPR, that is the gradient that favors tilling, is very small. A slight alteration of the gradientmight dramaticallyincreasethe rate at which the chestfills. We need somemeasurement of that. it may be that if you can optimize the rate

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of refilling, a higher rate becomes more effieacious,That is, if you refill maximallywith each activedecompression,the rate with fixbd compression stroke vohtmesmay becomemore variable. Right now, using conventional CPR between a rate of40 and 120,it is impossibleto demonstrate di%rent carotid flows in adult humans 1671. Daring manual ACD-CPR over the long haul, puRingupward from an uncomfortableposition is strenuous.If you are going to do this for an extendedperiod of time, you may prefer a mechanical deviceto do it for you. Wik

Safar has pointed out (Appendix 1,4A) that a breakthrough in ptehuspital CPR performance would occur with consistentreversibilityof 10min normothermiccardiac arrest (no-flow) to survival s is becausemobile ICU without brain 10 min. This has essenresponsetimes are a tially been achieved in dogs (681. The next chaBengeis for researchto reduce the over 50% failure rate to achieveROSC in prehospital cases of suddendeath, Sick heartsneedhigher coronary perfusion pressures.Bystander CPR steps ABC without devicesneedmod&&on for maximizing per&&m pressures.The ultimate will be ‘bridging’ from the unresuscitableheart situation with maximal achievableemergencyblood flow and oxygenation to prolonged CPB to help the heart overcome stunning, recover from transient ischemia,or to help hospital teams correct the underlying disorder, that primarily has made ROSC impossible. The search for increasingly more ef&ctive emergency artificial circulation measures,which do not require complicated expensiveequipment,should continue. A

Supportedby the US Army (USAMRMC, grant #AMlX7-94-J-4013), the Laerdal Foundation for Acute Medicine, and Baxter Laboratories.

searchConferencein P&&burgh, May 1985available from P. Safar, SCRR, 3434 Fifth Avenue, Pittsburgh, PA 15260,USA. 1A. Babbs CF: Optimal pressionin exta’ers wing Center, Purdue University, Lafayette, IN, USA. 2A. Keil JP, ReeseW: Basiclife support - Wow to teach and how to demrn&e the teaching effect? tensive sity, Magdeburg, Germany. 3A. Morioka T, Suzuki K, Matsumoto M: A new simpiifii push-pug device for cardiac massage.Kumamoto CoRegefor science and Welfare,Kumamoto UniversitySchoolof Me&&e, Japan. 4A. Safar P: Sqgestions for future reaaarchon cardiac arrest (CA) and cerebral resuscitation(CPCR). SCRR, University of Pittsburgh, PA, USA. References ill Safer P, Bin&r N. CeFdiopidatloatuyCwhral Resuscitation, ouidaliaa by tke WorId F tion of !hcietiw of (WFSA), cdn. 3. Lmdm: WI3 sa

t988.

w AnldoanHavt~tion diopuhnwyResw&ath diae CIve (ECC). J Am 2171-2295. 131 Cummins R, R%mUMEhd from OUf-l3f-hoapw cwdiac arrest: wwein style. circulatioa 1991;8): 9@-975. 141 Biibar NG, Safar P. Cercbrt4 prcwwtkm duriag cardiopulmonary resuscitation in dogs. Crit Care Mpd 1985; 13: 185-M. P, et al. Long+fm Mimal PI Safar P, Chvoid models for the 8 bmin isdmmia. In: Wauquier A, Borgera M, Amary WK, Cdr., FbztwtIon of Tissues Against Hypoxia. Amsterdam: Ekvier, 1982; 147-170.

M .%f&UP.Theprrnaationandthcnpy-d In: Ftwadis N ted). 171

Abstractsof the International ResuscitationRe-

181 Brain Resu&ation Clinical Trial I Study Group, Abramson NS, Safer P, Detre K, et al. Randomized clini-

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N. Birder et al. /Resuscitation 32 (1996) 63-75

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N. Bircher et al. /Resuscitation 32 (1996) 63-75 (411 Keil JP, Schmidt U, ReeseW, et al. Can teaching materials improve skill retention after basic life support training? Anaesthetist 1995;44 (Suppi. 2): S400 (abstract). [42] Wik L, Brennan RT, Braslow A. A peer-training model for instruction of basic cardiac life support. Resuscitation 1995;29: 119-128. [43] Cohen TJ, Tucker KJ, Lurie KG, et al. Active compressiondecompression:a new method of cardiopulmonary resuscitation. J Am Med Assoc 1992; 267: 2916-2923. [44] Cohen TJ, Goldner BG, Maccaro PC, et al. A comparison of active compressiondecompressioncardiopulmonary resuscitation with standard cardiopulmonary resuscitationfor cardiac arrests occurring in the hospital. N End J Med 1993; 329: 1918-1921. [45] Tucker KJ, Galli F, Savitt MA, et al. Active compressiondecompression resuscitation: effect on resuscitation successafter in-hospital cardiac arrest. J Am Coil Cardiol 1994,24: 201-209. 146) Lurie KG, Shuhx J, Callaham ML, et al. Evaluation of active compression-decompressionCPR in victims of out-of-hospital cardiac arrest. J Am Med Assoc 1994; 271: 1405-1411. [47l SchwabTM, Calhtham ML, Madsen CD, et al. A randomixed clinical trial of active compressiondecompression CPR vs. standard CPR in out-of-hospital cardiac arrest in two cities. J Am Med Assoc 1995; 273: 1261-1268. [48] Suxuki K, Mataumoto M, Tajiri A, et al. Ventilatory effect of cardiac massage by sternal compression with push-pug device. Clin Anesth (Japanese) 1993; 17: 1307-1310. [49] Morioka T. Artificial lung and resuscitation. Jpn Med News (Nihon Iji Shinpo) 1993;2618: 12-17. [Ml Liidner KH, Pfenninger EG, Schurman W, et al. Effectives of active compressiondecompression resuscitation on myocardial and cerebral blood flow in pigs. Circulation 1993;88: 1254-1263. [51] Chang MW, Cot&n P, Lurie KG, et al. Augmentation of late diastolic coronary flow velocity: the mechanismof improved myocardial perfusion during active compression-decompression cardiopulmonary resuscitation. Circulation 1993;88: 1027(abstract). [52] Chang MW, Coffeen P, Lurie KG, et al. Active compression-decompressionCPR improves vital organ perfusion in a dog model of ventricular tibrillation. Chest 1994, 1% 1250-1259. (531 Wik L, Naess PA, Ilebekk A, et al. Siiuhaneous active compression-decompression and abdominal binding increasecarotid blood Bow additively during cardiopulmonary resuscitation (CPR) in pigs. Resuscitation 1994; 28: 55-64. 1541 Wik L, Mauer D, Robertson C. The first European pre-

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