The investigators simulated cardiac arrest using mannequins that provide real-time feedback on the effectiveness of chest compressions and ventilations, according to Dr. Carvalho.
Chest compressions were defined as correctly performed if they were administered at a rate of at least 100/minute, with correct sternal hand placement, a depth of at least 1.5 inches, and a release step.
"The teams were very similar in terms of age, gender, self-reported fitness, and years of experience," Dr. Carvalho reported. Overall, 46% of team members were registered nurses, 15% were obstetricians, and 39% were anesthesiologists. Most (88%) had current certification in advanced cardiac life support.
Study results showed that within the transport group, there was a significant decrease in the percentage of chest compressions performed correctly between phase I and phase II, with a return to baseline in phase III. In contrast, the percentage was generally similar across phases in the stationary group, except for a small fall-off in phase III that he attributed to possible fatigue.
During phase II, the percentage of chest compressions performed correctly was 93% in the stationary group, compared with only 32% in the transport group.
"The reason for [more incorrect compressions] was primarily insufficient depth, but also the sternal hand being too low and no release," Dr. Carvalho commented. "Interestingly, we thought that the rate would be different [between groups], but we did not find significant differences. No one actually did a rate below 100."
Additional analyses showed that there was an interruption in CPR for 92% of teams in the transport group during phase II, compared with just 7% in the stationary group.
In the transport group, team members used a variety of positions when attempting to administer CPR while moving: most knelt next to the mannequin on the gurney, but some straddled the mannequin or ran alongside the gurney. Those running alongside "tended to have a lot of interruptions as they moved past the usual obstructions," he noted.
Mean tidal volume also dropped significantly in the transport group in phase II, whereas it remained essentially constant in the stationary group. However, Dr. Carvalho cautioned, the mannequins were only mask-ventilated and not intubated, which may have affected these results.
"There’s a lot of limitations with any simulated study," he acknowledged. "Obviously, this was a simulated arrest. The mannequin is really just a torso; we can’t administer left uterine displacement, it doesn’t have a pregnant belly, and we didn’t intubate." Also, teams were trained on the mannequin just before the study.
Dr. Carvalho disclosed no relevant conflicts of interest.