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CPR with chest compression alone was as effective as CPR with chest compression and mouth-to-mouth ventilation
TR E AT MEN T
CPR with chest compression alone was as effective as CPR with chest compression and mouth-to-mouth ventilation Hallstrom A, Cobb L, Johnson E, Copass M. Cardiopulmonary resuscitation by chest compression alone or with mouth-to-mouth ventilation. New Engl J Med 2000;342:1546d1553
OBJECTIVE To determine the efficacy of dispatcher-instructed CPR by chest compression alone as compared to CPR by chest compression with mouth-to-mouth ventilation performed by bystanders at the scene of a cardiac arrest.
279 patients were randomly assigned to CPR with chest compression and mouth-to-mouth ventilation.
DESIGN Randomized, controlled clinical trial.
MAIN RESULTS Thirty-five (14.6%) patients in the CPR with chest compression alone group, compared to 29 (10.4%) patients in the CPR with chest compression and mouth-to-mouth ventilation group survived to hospital discharge, though this difference was not significant (P"0.18). The study was underpowered, as it did not attain the planned 700 eligible cardiac arrest episodes. Instructions were completely delivered in 81% of episodes assigned to CPR with chest compression alone, whereas only 62% of episodes assigned to CPR with chest compression plus mouth-to-mouth ventilation received complete instructions (P"0.005).
SETTING Urban, fire department based emergency medical dispatch service in Seattle, USA with an average advanced life support response time of approximately 4 min. PATIENTS 520 adult patients (mean age 68 years, 64% male) experiencing a cardiac arrest with a call placed to the cardiac response center. An additional 776 patients were excluded from the study for the following a priori criteria: there was no actual cardiac arrest; the cardiac arrest was induced by drugs, alcohol, or carbon monoxide poisoning; or an advanced life support system was not available or used before hospital admission. INTERVENTION 241 patients were randomly assigned to CPR with chest compression alone, and
Commentary This well-designed study clearly reflects the authors’ knowledge of EMS systems. However, the study was limited, as the authors point out, by the inabilility to include all randomized patients in an intention-to-treat fashion. It was impossible to determine exclusion criteria at the point where a cardiac arrest patient is identified and intervention becomes necessary, and so a large number of patients were excluded from the analysis after randomization. The a priori exclusion criteria used in the study were legitimate: cardiac arrest induced by drugs, alcohol or carbon monoxide poisoning is reasonable as these groups are more often resuscitated and the cause of arrest is predominately respiratory. Outcomes of the excluded patients are reported with no statistically significant difference reported between patients receiving chest compressions with and without mouth-to-mouth ventilation. This is important, as the usefulness of ventilation in CPR for arrests due to primary respiratory causes may be paramount.1 104
Evidence-based Cardiovascular Medicine (2000) 4, 104d105 doi:10.1054/ebcm.2000.0340, available online at http://www.idealibrary.com on
MAIN OUTCOME MEASURES The primary end-point was survival to hospital discharge.
CONCLUSION In-hospital survival after CPR by chest compression alone was similar to that after compression plus mouth-to-mouth ventilation, when performed on cardiac arrest patients by bystanders given dispatcher-instructed CPR.
One important ancillary point is made in that dispatcherinstructed CPR without mouth-to-mouth ventilation more often results in CPR delivery to the patient, presumably because of the faster, easier instructions (81 vs 62% instruction completion prior to EMS arrival, P"0.005), and the lack of mouth-to-mouth contact as reflected in a larger refusal rate of bystanders to perform CPR (7.2 vs 2.9%). One puzzling question arises from these observations: if approximately 20% less patients received bystander CPR in the mouth-to-mouth ventilation group as compared to the chest compression alone group, and bystander CPR is associated with a 50% increase in survival, why does this not translate into a statistically significant difference between the two groups? No clear answer to this question is given. It is possible that the small sample size plays a part. Another possibility is that bystander-initiated CPR and dispatcherinstructed CPR may not be equivalent in terms of their effect on patient survival. However, the most important limitation of the study is that it was terminated prematurely. The sample size requirements ^ 2000 Harcourt Publishers Ltd
(already minimized because of the use of a one-sided alternate hypothesis) were not met and the result was a study with insufficient statistical power to provide a definitive answer to the research question posed. With this in mind, the conclusion could read: ‘this study demonstrates there is no large difference in survival rate between the two groups’. Another minor study limitation was the inability to assess quality of CPR given by bystanders, which may be reflected more in the mouth-to-mouth ventilation group, as it is the more difficult intervention to perform. One must view all these limitations as part of the overall clinical context of the problem. It is likely that the patients in this study would have not received bystander CPR in the absence of the EMS system. In a scenario where dispatcher-instructed CPR and bystander-initiated CPR are equivalent, the more and the earlier CPR is administered to these patients, the better, thus
^ 2000 Harcourt Publishers Ltd
strengthening the conclusion that chest compression alone may be the preferred method. Theresa Schwab, MD Andrew Worster, MD McMaster University, Hamilton, Ontario, Canada Literature cited 1. Becker LB, Berg RA, Pepe PE, et al. A reappraisal of mouthto-mouth ventilation during bystander-initiated cardiopulmonary resuscitation: a statement for healthcare professionals from the Ventilation Working Group of the Basic Life Support and Pediatric Life Support Subcommittees, American Heart Association. Circulation 1997; 96: 2102d2112
Evidence-based Cardiovascular Medicine (2000) 4, 104}105
105
CPR with chest compression alone was as effective as CPR with chest compression and mouth-to-mouth ventilation Hallstrom A, Cobb L, Johnson E, Copass M. Cardiopulmonary resuscitation by chest compression alone or with mouth-to-mouth ventilation. New Engl J Med 2000;342:1546d1553
OBJECTIVE To determine the efficacy of dispatcher-instructed CPR by chest compression alone as compared to CPR by chest compression with mouth-to-mouth ventilation performed by bystanders at the scene of a cardiac arrest.
279 patients were randomly assigned to CPR with chest compression and mouth-to-mouth ventilation.
DESIGN Randomized, controlled clinical trial.
MAIN RESULTS Thirty-five (14.6%) patients in the CPR with chest compression alone group, compared to 29 (10.4%) patients in the CPR with chest compression and mouth-to-mouth ventilation group survived to hospital discharge, though this difference was not significant (P"0.18). The study was underpowered, as it did not attain the planned 700 eligible cardiac arrest episodes. Instructions were completely delivered in 81% of episodes assigned to CPR with chest compression alone, whereas only 62% of episodes assigned to CPR with chest compression plus mouth-to-mouth ventilation received complete instructions (P"0.005).
SETTING Urban, fire department based emergency medical dispatch service in Seattle, USA with an average advanced life support response time of approximately 4 min. PATIENTS 520 adult patients (mean age 68 years, 64% male) experiencing a cardiac arrest with a call placed to the cardiac response center. An additional 776 patients were excluded from the study for the following a priori criteria: there was no actual cardiac arrest; the cardiac arrest was induced by drugs, alcohol, or carbon monoxide poisoning; or an advanced life support system was not available or used before hospital admission. INTERVENTION 241 patients were randomly assigned to CPR with chest compression alone, and
Commentary This well-designed study clearly reflects the authors’ knowledge of EMS systems. However, the study was limited, as the authors point out, by the inabilility to include all randomized patients in an intention-to-treat fashion. It was impossible to determine exclusion criteria at the point where a cardiac arrest patient is identified and intervention becomes necessary, and so a large number of patients were excluded from the analysis after randomization. The a priori exclusion criteria used in the study were legitimate: cardiac arrest induced by drugs, alcohol or carbon monoxide poisoning is reasonable as these groups are more often resuscitated and the cause of arrest is predominately respiratory. Outcomes of the excluded patients are reported with no statistically significant difference reported between patients receiving chest compressions with and without mouth-to-mouth ventilation. This is important, as the usefulness of ventilation in CPR for arrests due to primary respiratory causes may be paramount.1 104
Evidence-based Cardiovascular Medicine (2000) 4, 104d105 doi:10.1054/ebcm.2000.0340, available online at http://www.idealibrary.com on
MAIN OUTCOME MEASURES The primary end-point was survival to hospital discharge.
CONCLUSION In-hospital survival after CPR by chest compression alone was similar to that after compression plus mouth-to-mouth ventilation, when performed on cardiac arrest patients by bystanders given dispatcher-instructed CPR.
One important ancillary point is made in that dispatcherinstructed CPR without mouth-to-mouth ventilation more often results in CPR delivery to the patient, presumably because of the faster, easier instructions (81 vs 62% instruction completion prior to EMS arrival, P"0.005), and the lack of mouth-to-mouth contact as reflected in a larger refusal rate of bystanders to perform CPR (7.2 vs 2.9%). One puzzling question arises from these observations: if approximately 20% less patients received bystander CPR in the mouth-to-mouth ventilation group as compared to the chest compression alone group, and bystander CPR is associated with a 50% increase in survival, why does this not translate into a statistically significant difference between the two groups? No clear answer to this question is given. It is possible that the small sample size plays a part. Another possibility is that bystander-initiated CPR and dispatcherinstructed CPR may not be equivalent in terms of their effect on patient survival. However, the most important limitation of the study is that it was terminated prematurely. The sample size requirements ^ 2000 Harcourt Publishers Ltd
(already minimized because of the use of a one-sided alternate hypothesis) were not met and the result was a study with insufficient statistical power to provide a definitive answer to the research question posed. With this in mind, the conclusion could read: ‘this study demonstrates there is no large difference in survival rate between the two groups’. Another minor study limitation was the inability to assess quality of CPR given by bystanders, which may be reflected more in the mouth-to-mouth ventilation group, as it is the more difficult intervention to perform. One must view all these limitations as part of the overall clinical context of the problem. It is likely that the patients in this study would have not received bystander CPR in the absence of the EMS system. In a scenario where dispatcher-instructed CPR and bystander-initiated CPR are equivalent, the more and the earlier CPR is administered to these patients, the better, thus
^ 2000 Harcourt Publishers Ltd
strengthening the conclusion that chest compression alone may be the preferred method. Theresa Schwab, MD Andrew Worster, MD McMaster University, Hamilton, Ontario, Canada Literature cited 1. Becker LB, Berg RA, Pepe PE, et al. A reappraisal of mouthto-mouth ventilation during bystander-initiated cardiopulmonary resuscitation: a statement for healthcare professionals from the Ventilation Working Group of the Basic Life Support and Pediatric Life Support Subcommittees, American Heart Association. Circulation 1997; 96: 2102d2112
Evidence-based Cardiovascular Medicine (2000) 4, 104}105
105