Compression-only CPR may improve survival for patients in cardiac arrest due to shockable rhythms treated by bystanders with public access defibrillation
- 1University of Warwick, Warwick Clinical Trials Unit, Gibbett Hill, Coventry, B93 9BE, UK
- 2West Midlands Ambulance Service NHS Foundation Trust, Waterfront Way, Brierley Hill, West Midlands DY5 1LX, UK
- 3Heart of England NHS Foundation Trust, Bordesley Green East, Birmingham, B9 5SS, UK
- Correspondence to: Professor Gavin D Perkins
University of Warwick, Warwick Clinical Trials Unit, Gibbett Hill, Coventry, B93 9BE, UK;
Commentary on: Iwami T, Kitamura T, Kawamura T, et al.; for the Japanese Circulation Society Resuscitation Science Study (JCS-ReSS) Group. Chest compression-only cardiopulmonary resuscitation for out-of-hospital cardiac arrest with public-access defibrillation: a nationwide cohort study. Circulation 2012;126:2844–51.
Less than 1 in 10 victims of out-of-hospital cardiac arrests (OHCA) survive.1 Bystander cardiopulmonary resuscitation (CPR) doubles the chances of survival,2 yet is only undertaken in one-third of cases.3 Chest compression-only CPR (CCCPR) has emerged as an alternative to standard CPR, which includes compressions and ventilations. This method is easier to learn and retain and eliminates the necessity for mouth-to-mouth contact (which may be an impediment to a bystander starting CPR). Furthermore, it reduces potentially harmful interruptions in chest compressions caused during ventilations.
A meta-analysis of three randomised controlled trials found that when emergency medical dispatchers (EMD) provided telephone instructions to bystanders to initiate CCCPR instead of standard CPR, this improved survival to hospital discharge by 22%.4 In contrast, a meta-analysis of seven observational studies where bystanders initiated CCCPR saw no improvement in survival as compared to standard CPR.4
Iwami and colleagues sought to examine the success of bystander CCCPR among patients sustaining a witnessed OHCA who received shocks from a public access automated external defibrillator (AED).
This study was a prospective observational cohort study. Data were extracted from the All-Japan Utstein OHCA registry for 2005 to 2009. Patients who had a witnessed OHCA of suspected cardiac origin and received shocks from a public access AED were included. The study compared survival rates between patients treated with bystander CCCPR versus standard CPR. The main outcomes were the rate of prehospital return of spontaneous circulation (ROSC), 1 month survival and neurologically favourable 1 month survival.
From a population of 547 153 OHCA, a small cohort of 1376 (0.25%) patients with a suspected cardiac cause of their arrest, who received bystander CPR and shocks from a public access AED were included. CCCPR led to better outcomes than standard CPR (CCCPR vs standard CPR ROSC 50.2% vs 40.5%, p<0.001; 1 month survival 46.4% vs 39.9%, p=0.018; neurologically favourable survival 40.7% vs 32.9%, p=0.003). Multivariate analysis identified age and CCCPR (adjusted OR=1.33, 95% CI 1.03 to 1.7) as independent predictors of neurologically favourable survival. Temporal changes in the proportion of patients treated with bystander CCCPR were observed from a baseline rate of 5.1% in 2005 to 44.4% in 2009 (p<0.001).
The findings of this study are consistent with a previous research that reports bystander initiated CCCPR may be beneficial for the subgroup of adult patients that sustained a witnessed OHCA of presumed cardiac origin. When all the cases of OHCA (cardiac and non-cardiac) are considered, previous work from the Japanese registry identified that standard CPR is associated with better outcomes than CCCPR (adjusted OR=1.17, 95% CI 1.01 to 1.35). This is largely due to patients with arrests of non-cardiac origin, younger people and people in whom there was delay in the start of CPR having better outcomes if treated with standard CPR.
A generic weakness of observational studies is the potential of unmeasured factors confounding the association between the intervention and outcome. A potentially unreported confounder in this study is the link between chest compressions and early shock success. International resuscitation guidelines have recommended starting resuscitation with 30 chest compressions since 2005.5 If successful, defibrillation occurred during the first series of chest compressions, these patients would have been included in the CCCPR group as they did not reach the point in the resuscitation algorithm where ventilations were indicated. This would inflate the number of survivors in the CCCPR group. The authors acknowledge additional limitations, including the fact that the quality of CPR was not measured and the possibility that EMD may prompt CCCPR if ventilations were difficult.
It is difficult to see how the findings of this study could be implemented in practice. The patients studied represent only a small proportion (0.3%) of all OHCA. Moreover, this group is identified only after the AED is activated, and delivers a shock rather than at the point that resuscitation efforts are started. The groups excluded were those with non-shockable rhythms, which are more common in children, those with a primary respiratory cause of their arrest and/or prolonged downtime. These are the patients who experienced better outcomes if standard CPR is performed.