Cardiopulmonary resuscitation during spaceflight: examining the role of timing devices

The majority of International Space Station (ISS) astronauts represent nonmedical professions. In order to serve as Crew Medical Officers (CMO), future crewmembers receive 40-70 h of medical training within 18 mo before missions, including cardiopulmonary resuscitation (CPR) per the Guidelines of the American Heart Association. CPR compliance with the Guidelines is known to vary even among trained clinicians, let alone minimally trained caregivers (e.g., bystanders, nonphysician astronauts). The purpose of this study was to evaluate the effect of timing devices, including audible metronomic tones, on CPR performed by nonmedical personnel, specifically 40 astronaut analogues trained in a fashion and within a timeframe similar to an ISS astronaut. Twenty bystander pairs performed two-person CPR for 4 min on a simulated cardiac arrest patient using three interventions: 1) CPR with no timing devices; 2) CPR with metronomic tones for chest compressions; and 3) CPR with a timing device and metronome for coordinating ventilation and compression rates, respectively. Each CPR performance was evaluated for compliance with the (then current) 2000 AHA Guidelines. Numbers of breaths and compressions significantly deviated from target values in the first two interventions (38 and 42 breaths vs. target of 32 breaths; 282 and 318 compressions vs. target of 240 compressions); the use of timing devices for both components of CPR resulted in significant improvement (32 breaths and 231 compressions). CPR timing devices that coordinate both breaths and compressions improve compliance of astronaut analogue rescuers with CPR guidelines, and may improve overall CPR performance and outcome.