Evaluation of an unrestrained cardiopulmonary resuscitation method in microgravity

Abstract

Study objectives: With the permanent presence of humans in Earth orbit, the potential need for cardiopulmonary resuscitation (CPR) in spaceflight is increasing. Current National Aeronautics and Space Administration (NASA) protocols for CPR administration in orbit require that the victim and rescuer be restrained, a process that takes several minutes to complete. Methods that would allow for the rapid initiation of unrestrained CPR warrant investigation. The objective of this experiment is to evalute the quality of CPR provided in a preintubated mannequin in microgravity during parabolic flight. Methods: While in microgravity, aboard NASA's KC-135, 4 novice rescuers provided CPR compressions and ventilations at a 5:1 ratio either unrestrained (UR) from behind the mannequin in a bear hug manner or using a standard side or waist straddle method with the mannequin and rescuer restrained (R). Ventilations were provided either with a bag-valve-mask (BVM) or the CardioVent Bellows on Sternum CPR adjunct (BSR). Depth of compression, compression and ventilation rate, and onboard g forces were recorded digitally. Results: In microgravity, the mean depths of compression were R-BVM 1.87±0.06 inches, UR-BVM 1.49±0.44 inches, and UR-BSR 1.63±0.29 inches, whereas the compression per minute (CPM) rates were R-BVM 93.7±10.0 CPM, UR-BVM 107.7±10.2 CPM, and UR-BSR 108.0±1.7 CPM. The lengths of time to complete a 5:1 cycle were R-BVM 4.98±0.34 seconds, UR-BVM 4.70±0.48 seconds, and UR-BSR 4.49±0.23 seconds. Ground-based measurements for standard CPR were 1.87±0.05 inches, 106.1±5.8 CPM, and 5.67±0.74 seconds. Conclusion: Although there was some individual variability, this experiment has demonstrated that CPR administered in microgravity can meet the American Heart Association standards for depth of compression (1.5 to 2.0 inches) and compression rate (around 100 CPM) and that CPR can be provided while unrestrained. The BSR CPR adjunct does not appear to provide any significant advantage over the BVM. The administration of CPR using the bear-hug maneuver and a BVM immediately after a blind intubation (previously shown to be possible in microgravity) while awaiting the setup of the restraint system may buy time during a cardiopulmonary emergency.