Letter by Ristagno and Gullo Regarding Article, “Survival Is Similar After Standard Treatment and Chest Compression Only in Out-of-Hospital Bystander Cardiopulmonary Resuscitation”
To the Editor:
We appreciated the elegant study by Bohm et al,1 which has reported equivalency of survival among victims of cardiac arrest who received standard cardiopulmonary resuscitation (CPR) and those who received chest compressions–only (CCo) CPR. According to this study, smaller ventilations are required to maintain optimal ventilation/perfusion ratios during CPR, and in animal models, adverse outcomes followed prolonged interruptions in chest compressions for mouth-to-mouth ventilation.2 During lung inflation, venous return is transiently reduced, with the result that preload and ultimately aortic diastolic pressure is decreased. Systemic blood flow and organ perfusions are correspondingly reduced.
The highest priority after “sudden death” is to start chest compressions to maintain at least minimal coronary and cerebral perfusions. Early CPR delays the onset of ischemic myocardial injury and facilitates defibrillation. The results of the study by Bohm et al support this concept of performing continuous chest compressions without interruption. Bystander-initiated CPR, whether by minimally trained nonprofessional rescuers or by well-organized professional emergency medical response providers, has increased survival after out-of-hospital cardiac arrest.3
However, the ambulance response time reported by Bohm et al was only 6 minutes in patients treated with CCo, an interval that was significantly shorter than that for victims treated with standard CPR. This difference was obviously related to outcomes, as also hypothesized by the same authors. Even a totally occluded airway during the first 6 minutes of cardiac arrest, in fact, did not compromise survival if reasonable circulation was provided with chest compressions.4
The need for rescue breathing during the initial management of sudden cardiac arrest is currently being debated. In experimental settings, only animals ventilated during CPR attained a return of spontaneous circulation, in contrast to the failure of the CCo approach. Only when ventilation was performed during CPR did the arterial oxygen content stay at two thirds of the normal range, whereas with CCo, the arterial blood was desaturated, with no arterial-venous oxygen differences after 2 minutes.5
In recent decades, continuous clinical and experimental advancements have introduced new changes in treatment of cardiac arrest with the aim of improving outcomes. The concept of “early defibrillation” represents an example. When the interval between the estimated onset of ventricular fibrillation and the delivery of the first shock is <5 minutes, the likelihood is that an immediate defibrillation attempt will be successful. Where early defibrillation is possible, therefore, CCo might represent a valid alternative to standard CPR. Studies have revealed significant advantages in training and performance through using this simplified approach when compared with the standard approach, especially in the case of lay rescuers. CCo is thus an interesting and exciting addition to the current American Heart Association guidelines, but given that every new treatment requires caution and further investigations, we support and applaud the article of Bohm et al as initial strong clinical evidence of the minor role of ventilation during CPR. In settings of longer time between cardiac arrest and defibrillation, however, decreased survival has been reported and effects on neurological and final outcomes remain to be proved. Under these conditions, therefore, it might seem reasonable to suggest the standard approach, including ventilation, to reduce arterial blood desaturation and allow for minimal oxygen delivery to the vital organs.
Bohm K, Rosenqvist M, Herlitz J, Hollenberg J, Svensson L. Survival is similar after standard treatment and chest compression only in out-of-hospital bystander cardiopulmonary resuscitation. Circulation. 2007; 116: 2908–2912.
Kern KB, Hilwig RW, Berg RA, Sanders AB, Ewy GA. Importance of continuous chest compressions during cardiopulmonary resuscitation: improved outcome during a simulated single lay-rescuer scenario. Circulation. 2002; 105: 645–649.