A new method for the performance of external chest compressions during hypogravity simulation

Introduction: 2015 UK resuscitation guidelines aim for 50-60mm depth when giving external chest compressions (ECCs). This is achievable in hypogravity if the rescuer flexes and extends their arms during CPR, or using a new method trialed; the 'Mackaill-Russomano' (MR CPR) method. Methods: 10 participants performed 3 sets of 30 ECCs in accordance with 2015 guidelines. A control was used at 1Gz, with eight further conditions using Mars and Moon simulations, with and without braces in the terrestrial position and using the MR CPR method. The MR CPR method involved straddling the mannequin, using its legs for stabilization. A body suspension device, with counterweights, simulated hypogravity environments. ECC depth, rate, angle of arm flexion and heart rate (HR) were measured. Results: Participants completed all conditions, and ECC rate was achieved throughout. Mean (+/- SD) ECC depth using the MR CPR method at 0.38Gz was 54.1 +/- 0.55mm with braces; 50.5 +/- 1.7mm without. ECCs were below 50mm at 0.17Gz using the MR CPR method (47.5 +/- 1.47mm with braces; 47.4 +/- 0.87mm without). In the terrestrial position, ECCs were more effective without braces (49.4 +/- 0.26mm at 0.38Gz; 43.9 +/- 0.87mm at 0.17Gz) than with braces (48.5 +/- 0.28mm at 0.38Gz; 42.4 +/- 0.3mm at 0.17Gz). Flexion increased from approximately 2 degrees - 8 degrees with and without braces respectively. HR did not change significantly from control. Discussion: 2015 guidelines were achieved using the MR CPR method at 0.38Gz, with no significant difference with and without braces. Participants were closer to achieving the required ECC depth in the terrestrial position without braces. ECC depth was not achieved at 0.17Gz, due to a greater reduction in effective body weight.