Letter by Stewart Regarding Articles, “Increasing Use of Cardiopulmonary Resuscitation During Out-of-Hospital Ventricular Fibrillation Arrest: Survival Implications of Guideline Changes” and “Measuring Progress in Resuscitation: It’s Time for a Better Tool”
To the Editor:
I read with interest the recent article by Rea et al1 and the editorial by Ornato and Peberdy.2 Both papers point to the underlying reason for the American Heart Association’s new defibrillation guideline. The change in the defibrillation guideline results from recognition that automated external defibrillators (AEDs) have a serious shortcoming compared with manual defibrillators. Clearly identifying defibrillator type (AED versus manual) as an important confounding variable is necessary to clarify the significance of results from resuscitation research.
AHA guidelines and training materials have promoted AEDs for more than a decade, advocating their use by trained caregivers as well as the lay public, with little acknowledgement of a major disadvantage: the requirement to stop chest compressions for periods of automated rhythm analysis. There is now for the first time a clear statement from the AHA that AEDs should not be used when manual defibrillators and trained operators are available.3 However, the new defibrillation guideline makes no distinction between manual defibrillators and AEDs–though it is clearly intended to mitigate the effects of pauses in chest compressions when using AEDs, and though no rationale is presented for its application to manual defibrillation.4 This tends to obscure the importance of defibrillator type as a confounding variable in clinical studies, as well as possibly compromising treatment with manual defibrillators.
The study by Rea et al1 provides important support for using the new guideline with AEDs but not for its use with manual defibrillators. The editorial2 also touches on the problem of AED use interfering with CPR but leaves the impression that the defibrillation guideline is somehow based on the “3-phase” model of cardiac arrest.5 This is not the case: the new guideline does not call for varying treatment based on time interval from collapse to start of treatment, the central inference from the 3-phase model; rather, the guideline is intended to lessen the problem of AED-required gaps in CPR after treatment has started. It seems likely that the boundary between the “electrical” phase (defibrillation first) and the “circulatory” phase (CPR first) in the model might vary according to defibrillator type. In studies testing this model, and more generally in research on defibrillation, defibrillator type (AED or manual) should be clearly identified as a confounding variable.
Rea TD, Helbock M, Perry S, Garcia M, Cloyd D, Becker L, Eisenberg M. Increasing use of cardiopulmonary resuscitation during out-of-hospital ventricular fibrillation arrest: survival implications of guideline changes. Circulation. 2006; 114: 2760–2765.
Ornato JP, Peberdy MA. Measuring progress in resuscitation: it’s time for a better tool. Circulation. 2006; 114: 2754–2756.
American Heart Association, Field JM, ed. Advanced Cardiovascular Life Support Provider Manual. Dallas, American Heart Association, 2006, p. 43.
2005 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiac care. Part 5: Electrical therapies: automated external defibrillators, defibrillation, cardioversion, and pacing. Circulation. 2005; 112 [Suppl I]: IV-35–IV-46.