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Author: Johnny Conkin Publisher: ISBN: Category : Aviation medicine Languages : en Pages : 60
Book Description
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.
Author: Johnny Conkin Publisher: ISBN: Category : Aviation medicine Languages : en Pages : 60
Book Description
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.
Author: Kristin K. Woodruff Publisher: ISBN: Category : Decompression sickness Languages : en Pages : 44
Book Description
Decompression sickness (DCS) is a serious risk to astronauts performing extravehicular activity (EVA). To reduce this risk, the addition of ten minutes of moderate exercise (75% V02pk) during prebreathe has been shown to decrease the total prebreathe time from 4 to 2 hours and to decrease the incidence of DCS. The overall purpose of this pilot study was to develop an exercise protocol using flight hardware and an in-flight physical fitness cycle test to perform prebreathe exercise before an EVA. Eleven subjects volunteered to participate in this study. The first objective of this study was to compare the steady-state heart rate (HR) and oxygen consumption (V02) from a submaximal arm and leg exercise (ALE) session with those predicted from a maximal ALE test. The second objective was to compare the steady-state HR and V02 from a submaximal elastic tube and leg exercise (TLE) session with those predicted from the maximal ALE test.
Author: Ronald R. Robinson Publisher: ISBN: Category : Aviation medicine Languages : en Pages : 20
Book Description
Estimating the risk of decompression sickness (DCS) in aircraft operations remains a challenge, making the reduction of this risk through the development of operationally acceptable denitrogenation schedules difficult. In addition, the medical recommendations which are promulgated are often not supported by rigorous evaluation of the available data, but are instead arrived at by negotiation with the aircraft operations community, are adapted from other similar aircraft operations, or are based upon the opinion of the local medical community. We present a systematic approach for defining DCS risk in aircraft operations by analyzing the data available for a specific aircraft, flight profile, and aviator population. Once the risk of DCS in a particular aircraft operation is known, appropriate steps can be taken to reduce this risk to a level acceptable to the applicable aviation community. Using this technique will allow any aviation medical community to arrive at the best estimate of DCS risk for its specific mission and aviator population and will allow systematic reevaluation of the decisions regarding DCS risk reduction when additional data are available.
Author: Michael R. Dobbs Publisher: Elsevier Health Sciences ISBN: 0323052606 Category : Medical Languages : en Pages : 729
Book Description
Clinical Neurotoxicology offers accurate, relevant, and comprehensive coverage of a field that has grown tremendously in the last 20 years. You'll get a current symptomatic approach to treating disorders caused by neurotoxic agents, environmental factors-such as heavy metals and pesticides-and more. Apply discussions of cellular and molecular processes and pathology to clinical neurology. Leading authorities and up-and-coming clinical neurotoxicologists present their expertise on wide-ranging, global subjects and debate controversies in the specialty, including Gulf War Syndrome. And, Expert Consult functionality allows you to access the full text of the book online, from any Internet connection. Provides a complete listing of neurotoxic agents-from manufactured to environmental-so you get comprehensive, clinical coverage. Covers how toxins manifest themselves according to age and co-morbidity so that you can address the needs of all your patients. Offers broad and in-depth coverage of toxins from all over the world through contributions by leading authorities and up-and-coming clinical neurotoxicologists. Features discussion of controversial and unusual topics such as Gulf War Syndrome, Parkinson's Disease, motor neuron disease, as well as other issues that are still in question. Includes access to www.expertconsult.com, a companion website where you can quickly search the complete contents of the book. Your purchase entitles you to access the web site until the next edition is published, or until the current edition is no longer offered for sale by Elsevier, whichever occurs first. If the next edition is published less than one year after your purchase, you will be entitled to online access for one year from your date of purchase. Elsevier reserves the right to offer a suitable replacement product (such as a downloadable or CD-ROM-based electronic version) should online access to the web site be discontinued.
Author: Johnny Conkin
Author: Johnny Conkin
Author: United States. National Aeronautics and Space Administration
Author: Johnny Conkin
Author: 
Author: Kristin K. Woodruff
Author: 
Author: Johnny Conkin
Author: Laura A. Thompson
Author: Ronald R. Robinson
Author: Michael R. Dobbs