Effects of hyperbaric air exposure with oxygen breathing during decompression on the exhaled volatile organic compounds.

BACKGROUND: This study aimed to investigate changes in exhaled volatile organic compounds (VOCs) in divers exposed to hyperbaric air. METHODS: A total of 17 adult divers underwent two sessions of hyperbaric air exposure at 30 m (400 kPa), separated by a one-week interval. In the first exposure, the divers were decompressed with hyperbaric air alone; in the second exposure, they breathed 100% oxygen for 30 min when decompressed to 18 m. The composition and concentration of VOCs in exhaled breath were measured before exposure, at the initiation of decompression, and after exposure. RESULTS: The results showed that, during decompression with air, several olefins and alkanes, such as 1-heptene and n-heptane, increased after hyperbaric exposure. In contrast, during decompression with oxygen, alkanes, such as 2,2-dimethylbutane, and oxygenated compounds, such as acetone and isopropanol, decreased. Dimethyl sulfide decreased under both conditions. Compared with VOCs immediately before decompression, acrolein and isoprene increased significantly after exposure under both conditions; several alkanes, ketones, and olefins, including n-heptane, 2-butanone, and 1-heptene, decreased significantly during decompression with air; dimethyl sulfide increased significantly, and carbon disulfide showed an upward trend in the decompression with oxygen group after hyperbaric exposure. The fold change in peroxidation-related olefins and alkanes was markedly higher, and the fold change in carbon disulfide tended to increase in the decompression with oxygen group compared with the decompression with air group. CONCLUSION: Oxygen breathing during decompression appears to delay or alter the clearance of certain exhaled alkanes, ketones, and olefins while promoting the generation of sulfur-containing compounds.