Comparison of different techniques for in microgravity-a simple mathematic estimation of cardiopulmonary resuscitation quality for space environment

Background: Since astronauts are selected carefully, are usually young, and are intensively observed before and during training, relevant medical problems are rare. Nevertheless, there is a certain risk for a cardiac arrest in space requiring cardiopulmonary resuscitation (CPR). Up to now, there are 5 known techniques to perform CPR in microgravity. The aim of the present study was to analyze different techniques for CPR during microgravity about quality of CPR.

Material and methods: To identify relevant publications on CPR quality in microgravity, a systematic analysis with defined searching criteria was performed in the PubMed database (http://www.pubmed.com). For analysis, the keywords ("reanimation" or "CPR" or "resuscitation") and ("space" or "microgravity" or "weightlessness") and the specific names of the techniques ("Standard-technique" or "Straddling-manoeuvre" or "Reverse-bear-hug-technique" or "Evetts-Russomano-technique" or "Hand-stand-technique") were used. To compare quality and effectiveness of different techniques, we used the compression product (CP), a mathematical estimation for cardiac output.

Results: Using the predefined keywords for literature search, 4 different publications were identified (parabolic flight or under simulated conditions on earth) dealing with CPR efforts in microgravity and giving specific numbers. No study was performed under real-space conditions. Regarding compression depth, the handstand (HS) technique as well as the reverse bear hug (RBH) technique met parameters of the guidelines for CPR in 1G environments best (HS ratio, 0.91 ± 0.07; RBH ratio, 0.82 ± 0.13). Concerning compression rate, 4 of 5 techniques reached the required compression rate (ratio: HS, 1.08 ± 0.11; Evetts-Russomano [ER], 1.01 ± 0.06; standard side straddle, 1.00 ± 0.03; and straddling maneuver, 1.03 ± 0.12). The RBH method did not meet the required criteria (0.89 ± 0.09). The HS method showed the highest cardiac output (69.3% above the required CP), followed by the ER technique (33.0% above the required CP).

Conclusions: Concerning CPR quality, the HS seems to be most effective to treat a cardiac arrest. In some environmental conditions where this technique cannot be used, the ER technique is a good alternative because CPR quality is only slightly lower.