Methemoglobin Formation in Humans During Exposure to Hyperbaric Oxygen in a Standard Navy Decompression Treatment Table

Stephen C. Wood · Joseph D. Bloom · Arthur A. Messier

Jan 1971 · Defense Technical Information Center

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An investigation was conducted to determine whether oxygen breathing at pressures greater than lATA had any deleterious effects on oxygen transport in humans. Two male subjects were exposed to Standard Navy Decompression Treatment Table 6 which prescribes O2 breathing at 60 FSW and 30 FSW with air breathing intervals to allay O2 induced pulmonary toxicity. Blood samples were obtained during the decompression table. There were significant changes in both subjects in the concentration of methemoglobin which increased from control values of 1 to 4% to 7 to 9% of total hemoglobin at 60 FSW and 6 to 8% at 30 FSW and returned to control values upon surfacing. Previous studies performed elsewhere in which this parameter was determined concluded that hemoglobin oxidation does not result from breathing OHP. These conclusions, however, were based on pre- and post-exposure measurements only. The findings of this study are significant in view of the known bimodal influence of methemoglobin on oxygen transport: decreased O2 capacity and a shift of the oxygen dissociation curve to the left. Levels of methemoglobin of 7.6% have been shown to significantly reduce O2 delivery to tissues on which the partial pressure of O2 (PO2) is 30 mm Hg or less. This would include cardiac and cerebral tissue. (Author)