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Background Recent studies have demonstrated improved cardiopulmonary circulation during cardiac arrest with the use of a hand-held suction device (Ambu CardioPump) to perform active compression-decompression cardiopulmonary resuscitation (CPR). The purpose of this study was to compare active compression-decompression with standard CPR during cardiac arrests in hospitalized patients.
Methods All patients over the age of 18 years who had a witnessed cardiac arrest while hospitalized at our center were enrolled in this trial; they were randomly assigned according to their medical-record numbers to receive either active compression-decompression or standard CPR. The study end points were the rates of initial resuscitation, survival at 24 hours, hospital discharge, and neurologic outcome. Compressions were performed according to the recommendations of the American Heart Association (80 to 100 compressions per minute; depth of compression, 3.8 to 5.1 cm [1.5 to 2 in.]; and 50 percent of the cycle spent in compression).
Results Sixty-two patients (45 men and 17 women) with a mean age (±SE) of 68 ±2 years were entered into the trial. Sixty-two percent of the patients who underwent active compression-decompression were initially resuscitated, as compared with 30 percent of the patients who received standard CPR (P<0.03); 45 percent of the patients who underwent active compression-decompression survived for at least 24 hours, as compared with 9 percent of patients who underwent standard CPR (P<0.004). Two of the 62 study patients survived to hospital discharge; both were randomly assigned to receive active compression-decompression. Neurologic outcome, as measured by the Glasgow coma score, was better with active compression-decompression (8.0 ±1.3) than with standard CPR (3.5 ±0.3; P<0.02).
Conclusions In this preliminary study, we found that, as compared with standard CPR, active compression-decompression CPR improved the rate of initial resuscitation, survival at 24 hours, and neurologic outcome after in-hospital cardiac arrest. Larger trials will be required to assess the potential benefit in terms of long-term survival.
Methods
This study was approved by the North Shore University Hospital-Cornell University Medical College institutional review board for compassionate use (without informed consent) during cardiac arrest. The eligible subjects were all hospitalized patients over the age of 18 years who had nontraumatic, witnessed cardiac arrests. The exclusion criteria included respiratory arrest without hemodynamic collapse, inability to achieve prompt endotracheal intubation within the first 15 minutes after the arrest, and do-not-resuscitate orders. All patients were randomly assigned by means of their medical-record numbers to receive a single type of CPR throughout their hospitalizations; patients with even numbers were assigned to active compression-decompression CPR and those with odd numbers to standard CPR. Compressions were performed according to the recommendations of the American Heart Association (80 to 100 compressions per minute; depth of compression, 3.8 to 5.1 cm [1.5 to 2 in.]; and 50 percent of the cycle spent in the compression phase). Figure 1 shows the Ambu CardioPump that was used for active compression-decompression. Compressions were performed at a pressure of 29.5 to 50.0 kg (65 to 110 lb), equivalent to a compression depth of 3.8 to 5.1 cm, depending on the stiffness of the chest, and were not interrupted for ventilation5,6. The cardiac-arrest team consisted of a senior resident (team leader) and two junior residents in internal medicine (all three trained in advanced cardiac life support) and an anesthesiologist to assist with endotracheal intubation. Bag ventilation was performed with 100 percent delivered oxygen. The role of the team leader was to ensure consistency in the location, rate, and depth of CPR compressions as well as advanced cardiac life support during both CPR techniques. Active compression-decompression CPR was performed by members of the arrest team who were specifically trained in this technique. The study was conducted in the medical intensive care unit, the coronary care unit, the cardiac-catheterization laboratory, and the medical wards at North Shore University Hospital-Cornell University Medical College. The end points for the study were the rate of successful initial resuscitation, defined as return of pulse and systolic blood pressure (above 90 mm Hg) for at least 1 hour, survival at 24 hours, discharge from the hospital, and neurologic outcome as assessed by means of the Glasgow coma score (in which 3 is the worst score and 15 the best score) approximately 24 hours after resuscitation7,8.
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The outcomes of the initial resuscitation attempts, survival at 24 hours, and hospital discharge in the groups assigned to active compression-decompression and standard CPR were analyzed and compared with use of chi-square analysis, with Yates' correction9,10. Before this study began, we performed a power calculation that determined that a sample of 20 patients per group was necessary, on the basis of the following assumptions: an initial rate of resuscitation and 24-hour survival of 30 percent in the standard-CPR group; demonstration of an absolute difference of 40 percent (from 30 percent to 70 percent) in the active-compression-decompression group; a two-sided alpha level of 0.05; and a beta error of 0.20. The primary analysis of resuscitation rates was limited to the first cardiac arrest in each of the patients assigned to each group. A secondary analysis evaluated the eventual outcomes in each group. The neurologic outcomes of patients who received standard and active compression-decompression CPR were compared with the use of an independent-samples t-test. A two-tailed P value of less than 0.05 was considered to indicate statistical significance. All other data are presented as means ±SE.
Results
Sixty-two patients (45 men and 17 women) with a mean age of 68 ±2 years were entered into the trial between October 15, 1992, and April 16, 1993. Twenty-nine patients (47 percent) were randomly assigned to active compression-decompression CPR and 33 patients (53 percent) to standard CPR. The CardioPump adhered to all patients regardless of the shape of the chest. Overall, this cohort represented an extremely ill population, in which at least 60 percent of the patients had a preexisting terminal illness. Table 1 and Table 2 list the clinical diagnoses, initial arrest rhythms, and base-line clinical characteristics of the two groups, which were similar. Several patients in each group had more than one clinical diagnosis. The mechanisms of arrest included electromechanical dissociation (defined as a cardiac rhythm without a palpable pulse) in 27 patients, asystole in 14 patients, and refractory ventricular tachycardia or ventricular fibrillation in 21 patients.
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Discussion
This study demonstrates improved rates of initial resuscitation, 24-hour survival, and neurologic outcome with active compression-decompression CPR as compared with standard CPR. The rates of initial resuscitation and 24-hour survival with standard CPR in this study are similar to those reported in previous studies11,12,13. Overall, a high percentage of patients in this study (at least 60 percent) had a preexisting terminal illness. Subsequently, 11 of the 28 patients who survived the initial resuscitation (39 percent) were given do-not-resuscitate status by their attending physicians (despite hemodynamic and neurologic recovery). This complicated the assessment of the effect of active compression-decompression on survival to hospital discharge. This preliminary study was terminated by the Food and Drug Administration on April 16, 1993, in favor of a multicenter trial that is planned in the future to determine whether this technique improves long-term survival.
Since Kouwenhoven et al. described the technique of CPR by closed-chest cardiac massage,14 several investigators have attempted to develop methods to enhance both cardiopulmonary circulation and survival. These techniques include military antishock trousers,15 high-impulse CPR,16,17 the mechanical Thumper (Michigan Instruments, Grand Rapids, Mich.),18 interposed-abdominal-counterpulsation CPR,19,20 and the circumferential pneumatic vest21,22. However, none of these methods have gained wide acceptance. Recent data on both interposed-abdominal-counterpulsation and vest CPR suggest a benefit from their use; however, both methods have important limitations16,17,18,19,22. Interposed-abdominal-counterpulsation CPR requires at least two operators and a third operator to perform ventilation. The vest is a highly complex device that requires expensive equipment (estimated cost, $8,000 to $10,000) and substantial time to set up. The device we studied is small and hand-held; it weighs only 0.7 kg (1.5 lb) and is inexpensive (estimated cost, $200). It is easy to use and its use is intuitive for anyone who has performed standard CPR. In addition, it is portable, requires no set-up time, and has a gauge that assists in the proper performance of the technique. To date, no complications have been reported with this device, and specifically, no increased incidence of rib fractures has been observed. On the basis of the limited efficacy of standard CPR and data on the use of active compression-decompression in animals and humans that have demonstrated improvement in cardiopulmonary circulation, ventilation, cerebral and myocardial perfusion, rates of initial resuscitation, 24-hour survival, and neurologic recovery, we believe that this may be a more effective method of CPR for patients with nontraumatic cardiac arrest1,2,3,4.
The mechanism of the improvement in cardiopulmonary circulation produced by active compression-decompression CPR remains speculative. Transesophageal echocardiography has demonstrated enhanced diastolic filling during active chest decompressions2,23. It may be that greater chest expansion results in a greater decrease in intrathoracic pressure, thereby increasing venous return and augmenting cardiac output2,23,24. The technique is probably more effective than standard CPR because of its ability to augment ventilation and myocardial and cerebral perfusion2,3.
On the basis of our preliminary study, we conclude that active compression-decompression is a simple and easy-to-perform technique for CPR that improves the rate of initial resuscitation, survival at 24 hours, and neurologic outcome after cardiac arrest, as compared with standard CPR. Further research is necessary to determine whether active compression-decompression CPR is associated with a long-term improvement in survival.
Dr. Todd J. Cohen is a coinventor of the technique of active compression-decompression cardiopulmonary resuscitation. All rights to this invention belong to the University of California (where this technique was developed and later licensed to Ambu International, Copenhagen, Denmark). The University of California has applied for a patent on this device (patent pending), and university policy provides for a percentage of royalties to go to the inventors.
We are indebted to Drs. Martin Lesser and Francine Mandel of the Biostatistics Department at North Shore University Hospital-Cornell University Medical College for statistical assistance; to Drs. Peter Reiser, Lawrence Scherr, and Stanley Katz for their assistance and encouragement throughout this study; to the medical house staff and cardiology fellows for their participation; to Ambu International (Copenhagen, Denmark) for supplying the active-compression-decompression devices (CardioPump) and the CPR Pal mannequin; and to Paula Magenheimer for assistance in the preparation of the manuscript.
Source Information
Presented as part of the 1993 Courmand & Comroe Young Investigator Award Competition at the 66th Scientific Session of the American Heart Association, Atlanta, November 8, 1993.
From the Electrophysiology Section, Department of Medicine, North Shore University Hospital-Cornell University Medical College, 300 Community Dr., Manhasset, NY 11030, where reprint requests should be addressed to Dr. Todd Cohen.
References
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Related Letters:
Active Compression-Decompression Cardiopulmonary Resuscitation
Stone P. G., Sachs F. L., Cohen T. J.
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Full Text
N Engl J Med 1994;
330:1391, May 12, 1994.
Correspondence
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