developed with the chest pump model in mind, in which
circumferential pressure can be delivered around the thorax, and
not just to the sternum, for forward flow to occur (Figure 8C).
Animal and human studies suggested that this type of device
improved myocardial perfusion pressure.87,88 Two recent human
trials were published in 2006, one showing a trend toward
decreased survival and the other showing improved survival
with load-distributing band CPR.89,90 Several methodological
differences may explain the discrepant results and also highlight
the challenges of conducting and comparing human studies of
resuscitation. In the conventional CPR arm of these 2 trials, for
example, survival to hospital discharge after outpatient ventricular
tachycardia/ventricular fibrillation arrest was 22.7% in one
and 5.2% in the other, despite the latter having shorter response
times, with a similar mean age and occurrence of bystander CPR
in the 2 cohorts.