The correlation between the impedance cardiogram and end-tidal carbon dioxide during cardiopulmonary resuscitation in a porcine model of cardiac arrest

Abstract

Introduction: Studies were conducted to evaluate cardiopulmonary resuscitation (CPR) in a simulated low gravitational field, such as Mars (hypoG), aimed at providing an insight into the performance of terrestrial CPR. Methods: Two studies were conducted to evaluate external chest compressions (ECC) depth and rate, as well as perceived exertion (RPE) and the physiological cost, when 4 sets of 30 ECCs were performed on a standard CPR mannequin for 1.5min during Mars simulation, using terrestrial (1Gz) as control. The first study (n=20; 2005 guidelines) also evaluated the electromyographic (EMG) activity of four muscles (triceps brachii, erector spinae, upper rectus abdominis, pectoralis major). The second study (n=30; 2010 guidelines) included range of elbow flexion, minute ventilation (VE) and peak oxygen consumption (VO2 peak) measurements. HypoG simulation was achieved using a body suspension device (BSD) and a counterweight system. Results: In both studies, subjects successfully performed ECCs at 1Gz and hypoG. In the first study, therewere increases from 1Gz values of 32% (p<0.001) for RPE and 44% (p=0.002) for HR when ECCswere performedduringMars simulation. In hypoG, the triceps brachii showed less activity when compared with the other three muscles studied (p<0.001). A higher RPE (p<0.05) was also seen in the second study, which was accompanied by an increased VE (11.4±5.9 to 37.5±10.3 Lmin−1, p<0.05) and VO2 peak (3.2±1.1 to 20.5±7.6 mLkg−1 min−1, p<0.05). The arm flexion angle during hypogravity CPR, compared to 1Gz CPR, was also increased (4.3±2.8◦ to 14.0±8.1◦, p<0.05). Conclusion: Simulated reduction of upper body weight did not decrease the ability to perform proper ECCs, however, it increased the physiological cost and altered performance of the ‘straight arm’ CPR technique. These findings could be used to improve terrestrial CPR, especially when physical disparities are encounteredwith the rescuer being smaller and lighter than the patient.