A Model for Predicting Central Nervous System Toxicity from Hyperbaric Oxygen Exposure in Man: Effects of Immersion, Exercise, and Old and New Data
Abstract
We analyzed symptoms of central nervous system (CNS) oxygen toxicity from 1726 controlled human hyperbaric 02 exposures at PO2 (Partial pressure of 02) levels ranging from 0.3 to 2.9 atmospheres (atm) using risk models and maximum likelihood analysis, and tested specific hypotheses with likelihood ratios. The data were sorted into dry and immersed, no-exercise, and exercise conditions; new studies were separated from those before 1972. The analysis showed that CNS toxicity, in contrast to pulmonary, increases non-linearly with 02 level (power on 02 > 2) and time: the longer an exposure has been, the riskier additional exposure becomes (power on time > 1.2). Immersion and exercise each significantly increased the risk of toxicity at any PO2 and time combination. Older studies of immersed, exercised subjects predicted significantly more risk than new studies conducted under comparable conditions and could not be combined for parameter estimation. Reasons for this incompatibility are discussed. Parameters obtained from only the new data predict that current U.S. Navy depth/time limits for 02 diving should keep the incidence of 02 toxicity below 1%, provided recommended purging procedures are followed.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1994
- Accession Number
- ADA278348
Entities
People
- A. L. Harabin
- L. D. Homer
- S. S. Survanshi