Humidity does not affect central nervous system oxygen toxicity.
Arieli, R., and Y. Moskovitz.
Israel Naval Medical Institute, Israel Defense Force Medical Corps, Haifa 31080, Israel
APStracts 8:0318A, 2001.
Central nervous system (CNS) oxygen toxicity can occur as convulsions and loss of consciousness when hyperbaric oxygen is breathed in diving and hyperbaric medical therapy. Lin and Jamieson (J Appl Physiol 75: 1980-1983, 1993) reported that humidity in the inspired gas enhances CNS oxygen toxicity. Because alveolar gas is fully saturated with water vapor, we could not see a cause and effect and surmised that other factors, such as metabolic rate, might be involved. Rats were exposed to 507- and 608-kPa O2 in dry (31 or 14%) or humid (99%) atmosphere until the appearance of the first electrical discharge preceding the clinical convulsions. Each rat served as its own control. A thermoneutral temperature (28 ± 0.4°C) yielded resting CO2 production of 0.81 ± 0.06 ml•g"minus"1•h"minus"1. Latency to the first electrical discharge was not affected by humidity. At 507-kPa O2, latency was 23 ± 0.4 and 22 ± 0.7 min in dry and humid conditions, respectively, and, at 608-kPa O2, latency was 15 ± 4 and 14 ± 3 min in dry and humid conditions, respectively. When no effects of CO2 and metabolic rate are present, humidity does not affect CNS oxygen toxicity. Relevance of the findings to diving and hyperbaric therapy is discussed.
Received 23 January 2001; accepted in final form 27 April 2001.
APS Manuscript Number A64-1.
Article publication pending J Appl Physiol
ISSN 1080-4757 Copyright 2001 The American Physiological Society.
Published in APStracts on 29 June 2001