Pre-treatment with hyperbaric oxygenation reduces bubble formation and platelet activation

Abstract

Bubble formation and platelet activation are major factors contributing to decompression sickness. We hypothesized that pretreatment with hyperbaric oxygen immediately before a dive may reduce bubble formation and platelet activation in humans. Five healthy volunteer subjects (1 female and 4 males; age, 33.6±2.9 years; height, 170±3 cm; weight, 71±8 kg, body mass index, 24.5±22.0 kg/m²) participated in this study with a 4-day protocol. On day 1, a multiplace hyperbaric chamber was used to compress all subjects with air to 4 atmosphere absolute (ATA) for 25 minutes; they were then decompressed to surface pressure at a rate of 10 m/min. Once surface pressure was reached, they were monitored with precordial ultrasonic Doppler at 20 min, 50 min and 80 min. Venous blood samples were obtained immediately before and after pressure exposure. On day 2, all subjects were compressed at 1.6 ATA for 45 min with 100% oxygen; they were then decompressed to surface pressure at a rate of 10 m/min. As soon as they reached surface pressure, they were immediately exposed to the same compression-decompression protocol as day 1; blood samples were taken after the second pressure exposure. Platelet activation was examined before and after exposure. On days 3 and 4, we inverted the protocol to minimize the influence of the first immersion on bubble formation. In comparison to the standard compression protocol, compression after hyperbaric oxygenation led to significantly reduced bubble numbers and platelet activation (11.4%±0.7% vs. 5.4%±0.5%, p<0.05). This study shows that hyperbaric oxygenation pretreatment significantly reduces decompression-induced bubble formation and platelet activation. Hyperbaric oxygenation pretreatment may reduce the risk of decompression sickness in at-risk activities.