Chest-Compression-Only vs. Standard Cardiopulmonary Resuscitation: Shouldn't We Wait for More Evidence?

Provision of cardiopulmonary resuscitation (CPR) extends the time interval over which defibrillation can be successful andthus increases the likelihood of survival from cardiac arrest. Despite massive training efforts andcommunity awareness programs to educate individuals about the importance of CPR until the arrival of emergency medical services (EMS), rates of bystander CPR in most places remain low. While it is generally agreed that bystander CPR is beneficial, the form such CPR should take is debated. Should bystander CPR consist of rescue breathing alternating with chest compression (standard CPR) or should it consist of chest compression only? Critics of standard CPR argue that provision of ventilations needlessly complicates CPR training, interrupts circulatory support provided by chest compressions, andmay be less effective than the administration of only chest compressions. They call for changes in resuscitation guidelines, reflected in a science advisory statement recently issued by the American Heart Association (AHA),¹ recommending chest-compression-only CPR.², ³ This advisory was based on three studies in humans (all category 4 level of evidence) that have been published since the 2005 resuscitation guidelines.⁴ Other organizations such as the European Resuscitation Council,⁵ the Resuscitation Council of the United Kingdom,⁶ andseveral researchers⁷, ⁸ have suggested waiting for more definitive evidence before undertaking such a drastic change in cardiac resuscitation. Deciding on the optimal method of CPR involves issues of oxygenation, circulation, andlayperson education. We must consider each of these carefully in determining whether ventilatory support has a place in CPR.

Proponents of chest-compression-only CPR argue that the current guidelines for provision of artificial ventilations were derived from experimental data based on paralyzed, anesthetized subjects who had normal circulation but were apneic andthus required ventilatory support. In contrast, in the immediate aftermath of cardiac arrest due to ventricular fibrillation or other arrhythmias, the principal problem is one of absent circulation (or only that which is provided by CPR). In this setting, it is argued that provision of oxygen andventilation is of less importance because the primary emergency that such patients face is not respiratory insufficiency, but low blood flow.⁹

Proponents of the need for ventilatory support during resuscitation argue that oxygen is vital for maintaining organ viability andthere is little reason to circulate blood if its oxygen content is depleted. When cardiac arrest stems from a primary cardiac etiology, rather than asphyxiation, blood oxygenation levels are initially preserved. However, after a few minutes, the blood oxygen saturation declines steadily andadequate ventilation becomes a more crucial component of successful resuscitation.¹⁰ Studies from the early 1960s convincingly demonstrate that chest compression alone cannot maintain or restore blood oxygen saturation,¹¹, ¹² andproponents of keeping artificial ventilation in CPR guidelines argue that oxygen input is just as vital for patients in cardiac arrest.

Supporters on both sides of this issue also differ over the ability of laypeople to initiate andperform standard CPR satisfactorily. Proponents of chest-compression-only CPR argue that simplifying the protocol for bystander CPR will lead to less reluctance to initiate CPR andwill make CPR easier to teach, learn, andremember. Several studies have shown that both laypeople andhealth workers may be discouraged from starting CPR because of health andsafety concerns,¹³, ¹⁴, ¹⁵ especially when CPR is to be performed on a stranger.¹⁶ The additional steps required to perform rescue breathing can also be confusing for laypeople to learn¹⁷ andretain over time.¹⁸ Among medical students, chest-compression-only CPR skills were shown to decline less over 18 months than standard CPR skills,¹⁹ though this has not been comparably examined in persons without medical training. Finally, proponents of chest-compression-only CPR also argue that bystanders who are trained to provide ventilations take longer to initiate CPR.²⁰

Advocates of standard CPR argue that apprehension andfear of causing further harm to the victim of cardiac arrest, rather than concerns for one's own health, are more often cited as reasons for not initiating CPR. One study reported that only 1.1% of participants who failed to initiate CPR cited objection to the mouth-to-mouth ventilation as their reason, compared with 46% who reported that they did not start CPR because of having been panic-stricken or anxious about making the situation worse.²¹ Furthermore, the elimination of rescue breathing from CPR protocols even before ongoing randomized trials addressing this question have been completed risks creating confusion over “flip-flops” in guideline recommendations. If the guidelines are changed multiple times, laypeople may be even more uncertain about the correct procedures andmay be more likely not initiate any form of CPR. Furthermore, though the chest-compression-only method of CPR leads to more compressions per minute andcan be begun more rapidly than standard CPR, the quality of the compressions is worse.²²

Proponents of chest-compression-only CPR argue that human andanimal studies have shown no differences in survival andneurologic outcomes between the two methods of CPR. While a few animal studies have shown that pigs receiving chest-compression-only CPR had the same rates of survival as those receiving standard CPR,²³, ²⁴, ²⁵, ²⁶, ²⁷ in several of these studies²³, ²⁵, ²⁶ the pigs had open endotracheal tubes, which allowed significant amounts of passive ventilation, even when no ventilations were given. Pigs in cardiac arrest also tend to gasp at greater rates than humans, which increases their oxygenation levels.⁷ In a study in which the pigs' gasping reflexes were paralyzed, survival was worse in the chest-compression-only group compared with the group that received ventilations.²⁸ It has also been argued that unconscious humans are much more likely to have obstructed airways than are pigs, so the results of the animal studies are not applicable to humans.²⁹

Another argument in support of standard CPR is that the “screening” benefit of mouth-to-mouth ventilation helps to sort out patients in true cardiac arrest from patients who are unconscious because they have just fainted or had a seizure. In King County, Washington, for example, about 50% of the situations in which the emergency dispatcher begins to deliver telephone CPR instructions turn out not to be cardiac arrests. In many of these instances, the provision of rescue breathing is what leads the bystander to realize the patient is not in cardiac arrest andthus it is not necessary to deliver chest compressions, which may injure the patient needlessly.

A few studies in humans demonstrate that chest-compression-only CPR is as effective as standard CPR. The single prospective randomized clinical trial addressing this issue involved CPR instructions from emergency dispatchers in Seattle andshowed no difference in survival between patients who were randomly assigned to receive standard CPR versus chest-compression-only CPR from bystanders.³⁰, ³¹ However, proponents of standard CPR argue that this study was designed to examine differences in outcome of CPR instructions given over the telephone, rather than across-the-board guideline changes for all bystanders. Also, the rapid response time in Seattle of about 3.5 minutes on average may have precluded the opportunity to show any difference between the two methods of bystander CPR. Since most communities have appreciably longer response times than this, it may be erroneous to assume the results of this study will be applicable to other locations.

All other human studies have been observational in their designs. For example, a 1993 study from Belgium reported that survival two weeks after cardiac arrest was almost the same in patients receiving good-quality standard CPR as in those receiving high-quality chest compressions only.³² A Japanese study also showed no difference between groups receiving the two types of CPR andeven found improvements in neurologic outcome in patients who received chest-compression-only CPR.³ A second Japanese study showed comparable one-year survival in patients receiving either standard or chest-compression-only CPR among those treated within 15 minutes after collapse. However, in the few survivors whose arrests had gone untreated for more than 15 minutes, those who received rescue breathing had better neurologic outcomes.³³ A Swedish study showed no difference in one-month survival between recipients of the two methods of CPR.⁸ Finally, in a Dutch study, survival to hospital discharge was also not significantly different between patients receiving chest-compression-only CPR andthose receiving standard CPR.³⁴ Proponents of maintaining rescue breathing as part of CPR guidelines argue that these studies are flawed because it was unclear what prompted some bystanders to perform chest-compression-only CPR. Since the groups receiving the two types of CPR were not randomly assigned, they would be expected to have differences that may be related to survival.

If one accepts the arguments marshaled by advocates for chest compression only, it remains to be answered to whom the new guidelines should apply—laypersons, professional EMS personnel, and/or bystanders performing dispatch-assisted telephone CPR? The advisory statement recently issued by the AHA suggests that untrained bystanders perform chest-compression-only CPR andtrained bystanders perform rescue breathing if they feel confident in their abilities to do so.¹ This advisory does not address EMS or dispatcher-assisted CPR protocols. However, if laypersons are told to perform chest-compression-only, why should professionals act differently?

Another vital question is whether one type of CPR should fit all circumstances. Proponents of chest-compression-only admit that rescue breathing is required in asphyxial collapse or anaphylaxis, andthe recent advisory issued by the AHA emphasizes that bystanders should not use chest-compression-only CPR for cardiac arrests in children, patients whose arrests appear to have resulted from noncardiac causes, or patients whose arrests were not witnessed. Thus, advocates of chest-compression-only argue that the circumstances of the arrest should dictate the type of CPR. Is it reasonable to ask laypeople to make these determinations? While it may be practical to expect health professionals to understand andimplement different protocols, it is difficult to imagine that untrained citizens will be able to distinguish andrecall the proper courses of treatment depending on the circumstance.

This is a complex issue, andproponents for both methods of CPR have strong arguments. Is there a way to bring clarity to the controversy? Perhaps the best course of action at this point is to await the results of two ongoing international randomized clinical trials. One trial is the Dispatcher-Assisted Resuscitation Trial (DART) involving emergency dispatch centers in King andThurston Counties in Washington State andin London, England. The other is the TANGO study, which involves all dispatch centers in Sweden andFinland. Both trials randomize callers who report cardiac arrests with instructions to give either standard or chest-compression-only CPR. Thus far, the two trials have enrolled over 4,000 patients, andpreliminary results are expected within a year. Given that standard CPR has never shown itself to be harmful, the question is whether to exercise a little patience or to risk the remorse of a rush to change before all the evidence is in.