Ting Yu, MD; Max Harry Weil,
MD, PhD; Wanchun Tang, MD; Shijie
Sun, MD; Kada Klouche, MD; Heitor Povoas, MD; Joe Bisera, MSEE
From The Institute of
Critical Care Medicine,
Correspondence to Max Harry Weil, MD, PhD, The Institute of Critical Care Medicine, 1695
Background— Current versions of automated external
defibrillators (AEDs) require frequent
stopping of chest compression for rhythm analyses and capacity
charging. The present study was undertaken to evaluate the effects
of these interruptions during the operation of AEDs.
Methods and Results— Ventricular fibrillation was electrically induced
in 20 male domestic swine weighing between 37.5 and 43 kg that were
untreated for 7 minutes before CPR was started. Defibrillation was
attempted with up to 3 sequential 150-J biphasic shocks, but each
was preceded by 3-, 10-, 15-, or 20-second interruptions of chest
compression. The interruptions corresponded to those that were
mandated by commercially marketed AEDs for rhythm
analyses and capacitor charge. The sequence of up to 3 electrical
shocks and delays were repeated at 1-minute intervals until the
animals were successfully resuscitated or for a total of 15 minutes.
Spontaneous circulation was restored in each of 5 animals in which precordial compression was delayed for 3 seconds
before the delivery of the first and subsequent shocks but in none
of the animals in which the delay was >15 seconds before the
delivery of the first and subsequent shocks. Longer intervals of CPR
interventions were required, and there was correspondingly greater
failure of resuscitation in close relationship to increasing delays.
The durations of interruptions were inversely related to the
durations of subthreshold levels of coronary perfusion
pressure. Postresuscitation arterial pressure and
left ventricular ejection fraction were more severely impaired with
increasing delays.
Conclusions— Interruptions of precordial
compression for rhythm analyses that exceed 15 seconds before each
shock compromise the outcome of CPR and increase the severity of postresuscitation myocardial dysfunction.
Key Words:
cardiopulmonary resuscitation • fibrillation • defibrillation • compression •
myocardium