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A correction has been published: N Engl J Med 1999;341(23):1770.
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Background We previously observed that short-term survival after out-of-hospital cardiac arrest was greater with active compression–decompression cardiopulmonary resuscitation (CPR) than with standard CPR. In the current study, we assessed the effects of the active compression–decompression method on one-year survival.
Methods Patients who had cardiac arrest in the Paris metropolitan area or in Thionville, France, more than 80 percent of whom had asystole, were assigned to receive either standard CPR (377 patients) or active compression–decompression CPR (373 patients) according to whether their arrest occurred on an even or odd day of the month, respectively. The primary end point was survival at one year. The rate of survival to hospital discharge without neurologic impairment and the neurologic outcome were secondary end points.
Results Both the rate of hospital discharge without neurologic impairment (6 percent vs. 2 percent, P=0.01) and the one-year survival rate (5 percent vs. 2 percent, P=0.03) were significantly higher among patients who received active compression–decompression CPR than among those who received standard CPR. All patients who survived to one year had cardiac arrests that were witnessed. Nine of 17 one-year survivors in the active compression–decompression group and 2 of 7 in the standard group, respectively, initially had asystole or pulseless electrical activity. In 12 of the 17 survivors who had received active compression–decompression CPR, neurologic status returned to base line, as compared with 3 of 7 survivors who had received standard CPR (P=0.34).
Conclusions Active compression–decompression CPR performed during advanced life support significantly improved long-term survival rates among patients who had cardiac arrest outside the hospital.
The promising results of initial clinical studies3,4 led to the evaluation of active compression–decompression CPR in a large number of clinical trials.5,6,7,8,9,10,11,12 Although some failed to demonstrate significant benefit with this new technique,5,6,7,8,9,10 other studies found that short-term survival improved significantly with active compression–decompression CPR as compared with standard CPR.11,12 The primary purpose of the current study was to determine whether one-year survival and neurologic outcome would also be significantly improved with the use of active compression–decompression CPR when this technique is used during advanced life support. This study is a continuation of an evaluation performed from November 1993 to January 1995, in which we compared the effects of active compression–decompression CPR with standard CPR on short-term survival among patients with out-of-hospital cardiac arrest.12
Methods
Study Design
We assessed one-year survival in all patients who had cardiac arrest and received CPR in the Paris metropolitan area or Thionville, France, from November 1993 to May 1995. The study was approved by the Consultative Council for the Protection of Persons Volunteering for Biomedical Research of the Unité de Formation et de Recherche Lariboisière Saint-Louis, Paris. The two-tiered organization of the French emergency medical system has previously been described.12,13 Fifteen mobile intensive care units located throughout Paris and Thionville participated in this multicenter study. These units serve approximately 2.5 million residents. Patients at least 18 years of age were treated during advanced life support with active compression–decompression CPR if their cardiac arrests occurred on odd days of the month and with standard CPR if the arrests occurred on even days.
We followed the Utstein guidelines for reporting out-of-hospital cardiac arrests.14 According to practice guidelines, we excluded patients with cardiac arrest that was presumed to be irreversible, as indicated by clinical characteristics including rigid body tone, pale color, low temperature, and the presence of presacral edema; those with do-not-resuscitate orders or known terminal illness14; and those in whom a spontaneous palpable carotid or femoral pulse was restored with basic life support alone. As in previous studies, patients for whom the time from cardiac arrest to basic CPR exceeded 30 minutes were also excluded.12,15,16
End Points
The primary end point was survival at one year. Survival to hospital discharge without neurologic impairment and neurologic outcome were secondary end points. Intervals between events were recorded from the time of collapse until admission to the intensive care unit.14 The outcomes of patients and complications related to the method of CPR were recorded by one of us. This physician also supervised the collection of follow-up data for each patient after hospital discharge by regular telephone contact with the patient or the patient's general practitioner. Follow-up information gathered included general status and neurologic outcome, assessed according to Glasgow–Pittsburgh cerebral-performance categories.14 On this scale, a cerebral performance score of 1 indicates full neurologic recovery, whereas a score of 5 indicates profound neurologic impairment. Neurologic status one year after cardiac arrest was compared with neurologic function before arrest by questioning the family or the general practitioner.
Basic and Advanced Life Support
During basic life support, either standard CPR or active compression–decompression CPR was performed by rescue and ambulance personnel from various emergency-medical-service organizations.12,13 All basic-life-support personnel were trained twice and tested monthly in the performance of both standard CPR and active compression–decompression CPR so that they could assist during advanced life support. During the study, not all of the more than 200 basic-life-support teams in Paris and Thionville were equipped with an active compression–decompression device. Consequently, we did not randomly assign the method of CPR used during basic life support in this study.
All 15 participating mobile intensive care units were equipped to perform either type of CPR for advanced life support. Physicians in these mobile units were trained and tested every three months during the study period. Standard CPR was always performed according to the recommendations of the American Heart Association and the European Resuscitation Council.17,18 Active compression–decompression CPR was performed with a CardioPump (Ambu International, Glostrup, Denmark) according to published recommendations.19,20 To prevent fatigue, the rescuer performing CPR by either technique was instructed to rest after three minutes, and another rescuer continued the resuscitation effort.
On arrival, physicians of the mobile intensive care units intubated patients and initiated ventilation with a portable pneumatic ventilator (Airox, BioMS, Pau, France). All resuscitation efforts with either method of CPR were performed only at the scene of the cardiac arrest and not in a moving vehicle. Patients were transported to the hospital only if they were successfully resuscitated at the scene.
Statistical Analysis
On the basis of a review of data from our earlier study12 and data from previous studies in France that found that the proportion of patients surviving one year after standard CPR and advanced life support was close to 2 percent,21 the sample size for each group was fixed at 375 patients, the number required for the study to have 80 percent power to detect an absolute difference of 4 percent between groups in the proportion of patients surviving after one year. In our previous study in Paris, we found that short-term survival was greater with active compression–decompression CPR than with standard CPR.12 In the current study, we extended that investigation and enrolled additional patients to meet the requirement for 375 patients in each group.
The data were analyzed according to the intention-to-treat principle. Since all the patients were studied for one year, the proportions of patients who survived in the two groups were compared with use of the chi-square test. When conditions of validity for the chi-square test were not fulfilled, Fisher's exact test was used and exact confidence intervals calculated. Continuous variables were compared with use of Student's t-test or with use of the Mann–Whitney distribution-free test in the case of nongaussian distribution. All tests were performed with biomedical Data Package software (University of California, Los Angeles) or StatXact software (Cytel, Cambridge, Mass.).
Results
A total of 1083 calls to emergency medical systems for assistance with cardiac arrests were recorded during the 19-month study period. Of the 1083 patients, 333 did not receive advanced life support and were excluded from enrollment. The excluded patients were well matched between the group that received standard CPR and the group that received active compression–decompression CPR, in the following ways. Basic life support was not provided to 111 patients who had irreversible arrest and to 9 patients who had do-not-resuscitate orders; advanced life support was not provided to 91 patients who had a terminal illness and to 114 patients for whom the time from collapse to initiation of basic CPR was known to be greater than 30 minutes; and 8 patients recovered after basic life support alone. The remaining 750 patients were treated with advanced life support.
Among the 750 patients were 47 who were erroneously treated with a CPR technique that did not correspond to the assignment strategy according to odd and even days: 27 patients received standard CPR instead of active compression–decompression CPR, and 20 patients received active compression–decompression CPR instead of standard CPR. The intention-to-treat analysis included 377 patients who were assigned to standard CPR and advanced life support and 373 who were assigned to active compression–decompression CPR and advanced life support. The base-line characteristics of the patients in the two study groups were similar (Table 1). The two groups were similar with regard to age, suspected cause of cardiac arrest, type of CPR during basic life support, and dose of epinephrine per minute. CPR was performed by a bystander for fewer than 10 percent of patients in each group.
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We found that with the use of active compression–decompression CPR during advanced life support, the rate of survival at one year was more than twice the survival rate with standard CPR. The majority of patients who benefited from the active compression–decompression technique had an initial rhythm of asystole. Although the results with the use of standard CPR in Paris were similar to those previously observed in large metropolitan areas in other developed countries,5,11,22 the one-year survival rates associated with the use of active compression–decompression CPR in our study were higher than the hospital-discharge rates associated with standard CPR in many metropolitan areas that have well-trained emergency personnel.21,22,23,24
All the one-year survivors in both groups in this study had a cardiac arrest that was witnessed. As compared with long-term survivors in the standard-CPR group, long-term survivors who received active compression–decompression CPR during advanced life support had a shorter duration of CPR during this phase before the return of spontaneous circulation, even though the mobile intensive care unit arrived significantly later. Moreover, an important feature of our study population was that more than 80 percent of the patients in each group had asystole when the cardiac rhythm was first recorded. Taken together, the results suggest that in patients who have out-of-hospital arrest, it may be particularly important to "prime the pump" with active compression–decompression CPR to restore sufficient metabolic support for cardiac contractility.
The percentage of patients with an initial rhythm of asystole was higher in our study than in other studies of active compression–decompression CPR.5,6,7,8,9,10,11 This may be because electrocardiographic monitoring is initiated by the advanced-life-support team on arrival, usually about 20 minutes after the cardiac arrest. Although asystole is thought to be a rhythm with a very poor prognosis, especially as compared with ventricular fibrillation, and although it was present in the majority of our patients, our overall rates of resuscitation were similar to those for studies in other large cities with efficient emergency systems where more patients were initially found to have ventricular fibrillation rather than asystole.5,7,10,11,12
The use of active compression–decompression CPR, as compared with standard CPR, has led to improved short-term outcomes in several clinical trials.11,12,25,26 However, the outcomes observed worldwide with active compression–decompression CPR have been inconsistent.3,4,5,6,7,8,9,10,11,12,25,26 Probably the most important reason for this inconsistency relates to training. In some studies, the rescue personnel were introduced to active compression–decompression CPR just one or two months before the clinical studies were initiated.5,7,9,10 By contrast, the emergency medical teams in the current study had used or had been familiar with this technique for more than two years before the study began. Moreover, training of all the personnel in both active compression–decompression CPR and standard CPR was frequent and rigorous and focused on use of the gauge on the suction device for monitoring compression and especially decompression. This approach has been shown to be essential for proper performance of the new CPR technique.19,20 In at least one large trial that had negative results, use of the gauge was not thought to be important.5 However, in support of training and use of the gauge are the results of a recent multicenter trial in France and Belgium that compared treatment with high and low doses of epinephrine in more than 3000 patients who had out-of-hospital cardiac arrest.26 Active compression–decompression CPR was rigorously taught at sites equipped to administer this type of CPR, and nearly 1000 patients received active compression–decompression CPR. Among patients who received low doses of epinephrine, hospital-discharge rates were 50 percent higher in the subgroup that received active compression–decompression CPR than in the subgroup that received standard CPR (P<0.05).
Where and for how long CPR is performed is another factor that is critical to effective resuscitation. Active compression–decompression CPR requires more effort than standard CPR.5,7,10,27 Recognizing this, the rescue personnel in the current study took three-minute turns to prevent fatigue while performing CPR. Moreover, in all cases CPR was performed at the scene of the arrest and not in a moving vehicle. Others have shown that standard CPR and especially active compression–decompression CPR are much more difficult to perform in a moving vehicle than under stationary conditions.28 Unlike other clinical trials of the active compression–decompression technique, in which CPR was often performed in a moving vehicle,5,7,10 in the current study we were able to maintain high-quality performance of both CPR techniques throughout the resuscitation effort.
In the recent French trials of CPR, a physician was present at the scene of cardiac arrest to administer and guide advanced life support.12,26 In studies in the United States, Canada, and Britain, physicians were not routinely present in the field.5,6,7,8,10,11 In addition, in France, CPR was performed for at least 30 minutes after the arrival of the mobile intensive care unit, regardless of the patient's initial cardiac rhythm. Prolonging CPR may be particularly important for patients found in asystole. In the current study, many patients required more than 20 minutes of CPR before they were successfully resuscitated. In other studies, patients in asystole received 10 to 15 minutes of CPR, and often, if they were not revived, all further rescue efforts were terminated.5,6,7,10,11
Finally, another difference between the current study and some other studies relates to sample size. The number of participants in each group in this study was calculated to ensure sufficient power to detect an expected difference in long-term end points, according to the results of an initial investigation.12 All the principal end points in other studies were short-term outcomes, and some of those studies did not have sufficient statistical power to reveal differences between the two methods of CPR in terms of hospital-discharge rates or longer-term survival.3,4,5,6,8,9,11 In one study,11 the 95 percent confidence interval of the odds ratio for hospital discharge included the value of 3.2 found for the odds ratio in the current study.
One of the limitations of the current study was that investigators could not be blinded to the method of CPR used in each group. Although the base-line characteristics of the patients were similar in the two groups, it is possible that bias on the part of the rescue personnel played a part in the technique used and hence in the outcomes. However, in our previous study, the duration of the resuscitation effort for patients who did not recover was the same for both CPR techniques.12 Moreover, the fact that many rescue personnel had been performing the new technique for a 19-month period decreased the possibility of bias. In any case, it is clear from a review of our previous experience that both short- and long-term survival rates have never been higher in France.
The results of this study show that the performance of active compression–decompression CPR, as compared with standard CPR, by advanced-life-support personnel increased the one-year survival rates of patients who had out-of-hospital cardiac arrest, but overall mortality was still very high. It will be essential to improve many of the interventions both before and after the patient's arrival at the hospital in order to maximize survival after cardiac arrest. Though not a panacea, active compression–decompression CPR increases the patient's chance of short- and long-term survival. Its use should be encouraged once sufficient numbers of rescue personnel have been trained to perform this new technique.
Supported in part by an institutional grant program of Université Paris VII and the Unité de Formation et de Recherche Lariboisière Saint-Louis, Paris.
We are indebted to the basic- and advanced-life-support teams, especially the Lariboisière University Hospital medical team, for their help in this study.
Source Information
From the Service Mobile d'Urgence et de Réanimation (SMUR) and the Department of Anesthesiology and Critical Care, Lariboisière University Hospital, Paris (P.P., F.A., D.P.); the Cardiac Arrhythmia Center, University of Minnesota, Minneapolis (K.G.L.); the Biophysics Laboratory, Fernand Widal Hospital, Paris (E.V.); Urgences–SMUR, Thionville Hospital (SMUR 57), Thionville, France (J.-L.P.); Urgences–SMUR, Lagny Hospital (Service d'Aide Médicale Urgente [SAMU] 77), Lagny, France (D.E.); SMUR and the Department of Anesthesiology and Critical Care, La Pitié–Salpétrière University Hospital (SAMU 75), Paris (P.E.); SMUR, Pontoise Hospital (SAMU 95), Pontoise, France (R.G.); SMUR, Montfermeil Hospital (SAMU 93), Montfermeil, France (P.C.); and SMUR, Aulnay-sous-Bois Hospital (SAMU 93), Aulnay-sous-Bois, France (J.B.).
Address reprint requests to Dr. Plaisance at the Department of Anesthesiology and Critical Care, Lariboisière University Hospital, 2 rue Ambroise Paré, 75475 Paris CEDEX 10, France, or at plaisance{at}claranet.fr.
References
Other members of the French Active Compression–Decompression Cardiopulmonary Resuscitation Study Group were J.-P. Cantineau, M.D., and M. Gizzi, M.D. (Service d'Aide Médicale Urgente [SAMU] 94), C. Ferracci, M.D., and C. Leopold, M.D. (SAMU 92), M. Giroud, M.D. (SAMU 95), B. Hennequin, M.D., C. Lapandry, M.D., P. Magne, M.D., and C. Prudhomme, M.D. (SAMU 93), and Y. Lambert, M.D. (SAMU 78).
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Related Letters:
Active Compression–Decompression Cardiopulmonary Resuscitation
Callaham M., Bubb M. R., Martens P., Plaisance P.
Extract |
Full Text
N Engl J Med 1999;
341:1770-1772, Dec 2, 1999.
Correspondence
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