Public access defibrillatorsBMJ 2003; 326 doi: https://doi.org/10.1136/bmj.326.7381.162 (Published 18 January 2003) Cite this as: BMJ 2003;326:162
Potential efficacy of public access defibrillation may be underestimated
- Malcolm F Woollard (Malcolm.firstname.lastname@example.org), executive officer
- Pre-hospital Emergency Research Unit, University of Wales College of Medicine, Cardiff CF11 8PL
- University of Wales College of Medicine, Cardiff CF14 4XN
- Department of Medical Cardiology, Glasgow Royal Infirmary, Glasgow G31 2ER
- Scottish Ambulance Service Headquarters, Edinburgh EH10 5UU
- Robertson Centre for Biostatistics, University of Glasgow, Glasgow G12 8QQ
- Cumbria and Lancashire Health Protection Unit, Preston Business Centre, Preston PR2 8DY
- Internal Medicine Department, Hospital Dr Gustavo Aldereguía Lima, Ave 5 de Septiembre y Calle 51A, Cienfuegos 55 100, Cuba
EDITOR—Pell et al provide useful data on the appropriate location of public access defibrillators.1 Not all of their conclusions, however, seem to be based on firm evidence.
They say that arrests that occur in obvious sites for locating defibrillators already have the shortest response times, yet only 340 out of 2646 (13%) patients in a suitable site received an ambulance within 3 minutes. Response time is not defined: a detail important in allowing valid comparison with other early defibrillation strategies.
The Department of Health defines this interval as starting when a chief complaint is identified by an ambulance dispatcher and ending when an ambulance stops at the scene. The time taken for a bystander to determine that action is needed and make a 999 call, as well as the time taken by the crew to reach the patient's side and deliver a counter-shock, are excluded.
The complete interval from collapse to first counter-shock is a key variable in determining outcome from cardiac arrest.2 Public access defibrillators may reduce the delays inherent in dialling 999 and consequently the time to first shock, even when the ambulance response is under 3 minutes. This potential benefit has not been included in the model used by Pell et al. Neither do they allow for the incremental benefits of a reduction in response time at intervals of more than four minutes. Mortality increases by 4% for each minute's delay to first shock.3
The authors say that provision of automated external defibrillators to other first responders could double overall survival to discharge, referring to their previously published article.4 This paper does not provide such evidence, concluding only that responding to 90% of calls within five minutes would increase the proportion of survivors to 10-11%. It requires a very large assumption to suggest …