Evaluation of External Cardiac Massage Performance During Hypogravity Simulation

Abstract

Preservation of astronaut crew health during an exploration mission to the Moon or Mars will be crucial to mission success. The likelihood of a life-threatening medical condition occuring during a mission to Mars has been estimated by NASA to be 1% per year (Johnston, 1998; Johnston, Campbell, Billica, & Gilmore, 2004). Since basic life support is a vital skill in critical care medicine, plans must be in place for cardiopulmonary resuscitation in both microgravity and hypogravity (i.e., on the surface of the Moon or Mars). Following the design of a body suspension device to simulate a hypogravity environment, subjects performed external chest compressions in 1G, 0.17G (Lunar), 0.38G (Mars), and 0.7G (Planet X). Chest compression adequacy was assessed by means of rate and depth. Heart rate immediately before and after three minutes of chest compression gave a measure of rescuer fatigue. Elbow flexion was measured using an electrogoniometer in order to assess the use of arm muscles to achieve chest compressions. This study found that the mean depth (Lunar and Mars) and rate (Mars) of chest compression was below American Heart Association recommendations during hypogravity simulation in the female group. Furthermore, elbow flexion proved to be significantly greater during Lunar and Mars hypogravity simulation than that of the 1G control condition, suggesting that upper arm force may be used to counter the loss of body weight in an attempt to maintain adequate chest compression under these conditions.

Extraterrestrial CPR and Its Applications in Terrestrial Medicine

“…It consists of carbon steel bars, 0.6 mm × 0.3 mm in thickness, which are shaped into a prism frame. It has a height of 2000 mm, with a base of 3000 mm × 2260 mm [46]. This BSD has been used to simulate microgravity by fully suspending a volunteer and CPR mannequin.…”

“…A carabineer connects the steel wire to the attachment point on the back of the body harness (Fesp P100PGP). The manikin was positioned on the floor during the hypogravity simulation and +1 Gz [6,46,47]. Figure 5 presents a schematic view of CPR being performed during ground-based hypogravity simulation.…”

“…However, a reduction in the upper body weight of the rescuer due to a reduced gravitational field will lead to a decreased ability to generate force through acceleration of the upper body and the subsequent transfer of that force through the straight arms. Research has shown that a natural tendency to adapt takes place, seeking to generate more force by flexing/extending the upper limbs in order to augment acceleration of the upper body [46]. In instances where traditional CPR in hypogravity is not sufficient to generate enough force to achieve the necessary depth of chest compressions, rescuers are encouraged to have a combined technique of accelerating their upper body and extending their upper limbs to generate enough force to compress the chest to 50-60 mm [45,47].…”

“…Initial hypogravity studies showed that CPR in hypogravity, particularly Lunar and Martian environments, was feasible using traditional terrestrial CPR. Furthermore, they highlighted the occurrence of an increase in the arm flexion angle of the rescuer [46]. Traditional teaching of BLS and CPR advocates that arms should be kept rigid in order to transfer the force of acceleration of the rescuers' upper body to the chest of the patient.…”

“…These studies show that for CPR to be effective, and achieve guideline recommendations, the rescuer needs to flex and extend their arms, up to 14° (±8.1°), and use their upper limb musculature to generate force to compress the chest to a sufficient depth. This was even greater in microgravity using the ER method, up to 16.5° (±10.1°); however, as the technique used is markedly different to terrestrial CPR, a direct comparison between the two is difficult [46,47,50] (Figure 12). Similar to the microgravity studies, the physiological cost was measured subjectively and objectively, using the Borg scale and VO 2 , respectively.…”