Determining the best technique: Methods, challenges, and innovations of performing microgravity CPR

Background

Space travel has always been one of humanity's grand visions. Though previously only selected astronauts could make this journey, commercial spaceflight has become a new frontier for exploration. Travelling in microgravity has many effects on the human body; the risk of unlikely but potentially fatal conditions, such as cardiac arrest, increases. On Earth, as in space, cardiac arrest demands immediate intervention through CPR. However, microgravity causes weightlessness which necessitates alternative techniques. CPR is governed by International CPR Guidelines (2020/21), which state that external chest compressions (ECC) must reach a depth of 50–60 mm, at a rate of 100–120 compressions per minute (CPM). This narrative review aims to investigate which microgravity CPR (mCPR) method is most effective according to these guidelines, as well as their challenges and innovations.

Methods

A literature search was conducted; initially 240 papers were found from the following databases: OVID (MEDLINE and EMBASE), SCOPUS, Web of Science, NASA Technical Reports Server, and Imperial Library Search was used for other records. Duplicates were removed and each reviewer assessed the papers for relevance. 25 studies were found, dating from 1990 to 2022, with 10 of these being primary research.

Results

The seven main techniques for conducting mCPR are the standard side position (SSP), waist straddle (WS), reverse bear-hug (RBH), handstand (HS), Evetts-Russomano (ER), Schmitz-Hinkelbein (SHB) and Cologne method (CM). Other methods include using various assistive devices, including the Stryker LUCAS 3, which had the greatest ECC depth of any method (49.9 ± 0.7 mm). Of the non-device methods, the HS was found to have the largest mean ECC depth (43.7 mm) and had the greatest mean ECC rate (105 CPM). ER achieved a mean ECC depth of 43.3 mm and mean ECC rate of 100.3 CPM. This is slightly less than that of HS, however based on practicality, ER may be easier to perform.

Discussion

CPR is difficult to carry out to acceptable standards (according to International 2020/2021 guidelines) even on Earth, where gravity allows body weight to provide the force needed for ECC. Despite a device providing the most effective chest compressions, it may not be feasible to bring to space due to size and weight constraints. Otherwise, the HS and ER are generally accepted as the most effective and least fatiguing mCPR methods. However, further research is required, as these results are based on limited data.