Pulmonary Oxygen Toxicity When Partial Pressure Is 2 atm (200 kPa)
Abstract
Even asymptomatic exposures to elevated oxygen partial pressure (PO2) can influence subsequent exposures. A model previously presented predicts accumulation of pulmonary effects after exposures to PO2 = 140 kPa (1.4 atm). However, that model cannot be used with oxygen accelerated decompression or after deep excursions. Dry chamber exposures to PO2 of 200 kPa (2 ATA on 100% humidified O2) were conducted to examine cumulative effects at PO2 more representative of those scenarios. Experiments were single (n=27), or paired three-hour exposures with surface intervals (SI) 15 to 17 hours (n=31), six hours (n=33), or three hours (n=36); single two-hour dives (n=12) had no incidence of pulmonary oxygen toxicity. A set (n=27) of three, 30-minute dives with two-hour SI was also assessed. Flow-volume loops and diffusing capacity and symptoms were recorded before and after exposures. Significant (p<0.05) mean changes from baseline in pulmonary function indices after second exposures occurred immediately after surfacing for all SI and persisted for two days for three-hour SI and for one day for 15-hour SI. Incidences of symptoms were 15% immediately after one exposure and 28%, 38%, and 31% immediately after a second with 15-, six-, or three-hour SI, respectively; and those of changes in pulmonary function indices ( PF) were 5%, 11%, 12%, and 14% for single exposures and 15-, six-, or three-hour SI, respectively. After the third 30-minute dive, 7% of subjects had symptoms or PF. Two days following the second exposure, resolution of symptoms was incomplete after six- or 15-hour SI, as was resolution of PF after 15-hr SI. The incidences indicate nonlinear superposition of effects of a first and second exposure, are not readily explained by delayed-onset injury, and are not amenable to treatment like that for the 140 kPa model.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 2013
- Accession Number
- ADA607426
Entities
People
- Barbara E. Shykoff
Organizations
- United States Navy Experimental Diving Unit