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In its first edition, Principles of Clinical Medicine for Space Flight established itself as the authoritative reference on the contemporary knowledge base of space medicine and standards of care for space flyers. It received excellent notices and is used in the curricula of civilian and military training programs and used as a source of questions for the Aerospace Medicine Certifying Examination under the American Board of Preventive Medicine. In the intervening few years, the continuous manning of the International Space Station has both strengthened existing knowledge and uncovered new and significant phenomena related to the human in space. The Second Edition incorporates this information. Gaps in the first edition will be addressed with the addition new and revised chapters. This edition is extensively peer reviewed and represents the most up to date knowledge.
It is important to understand the risk of serious hypobaric decompression sickness (DCS) to develop procedures and treatment responses to mitigate the risk. Since it is not ethical to conduct prospective tests about serious DCS with humans, the necessary information was gathered from 73 published reports. We hypothesize that a 4-hr 100% oxygen (O2) prebreathe results in a very low risk of serious DCS, and test this through analysis. We evaluated 258 tests containing information from 79,366 exposures in altitude chambers. Serious DCS was documented in 918 men during the tests. A risk function analysis with maximum likelihood optimization was performed to identify significant explanatory variables, and to create a predictive model for the probability of serious DCS [P(serious DCS)]. Useful variables were Tissue Ratio, the planned time spent at altitude (Talt), and whether or not repetitive exercise was performed at altitude. Tissue Ratio is P1N2/P2, where P1N2 is calculated (N2) pressure in a compartment with a 180-min half-time for N2 pressure just before ascent, and P2 is ambient pressure after ascent. A prebreathe and decompression profile Shuttle astronauts use for extravehicular activity (EVA) includes a 4-hr prebreathe with 100% O2, an ascent to P2=4.3 lb per sq. in. absolute, and a Talt=6 hr. The P(serious DCS) is: 0.0014 (0.00096-0.00196, 95% confidence interval) with exercise and 0.00025 (0.00016-0.00035) without exercise. Given 100 Shuttle EVAs to date and no report of serious DCS, the true risk is less than 0.03 with 95% confidence (Binomial Theorem). It is problematic to estimate the risk of serious DCS since it appears infrequently, even if the estimate is based on thousands of altitude chamber exposures. The true risk to astronauts may lie between the extremes of the confidence intervals since the contribution of other factors, particularly exercise, to the risk of serious DCS during EVA is unknown. A simple model that only accounts for four important variables in retrospective data is still helpful to increase our understanding about the risk of serious DCS.
Vols. for 1963- include as pt. 2 of the Jan. issue: Medical subject headings.