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/m 2 ) 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.
Effect of in-water oxygen prebreathing at different depths on decompression-induced bubble formation and platelet activation in scuba divers was evaluated. Six volunteers participated in four diving protocols, with 2 wk of recovery between dives. On dive 1, before diving, all divers breathed normally for 20 min at the surface of the sea (Air). On dive 2, before diving, all divers breathed 100% oxygen for 20 min at the surface of the sea [normobaric oxygenation (NBO)]. On dive 3, before diving, all divers breathed 100% O2 for 20 min at 6 m of seawater [msw; hyperbaric oxygenation (HBO) 1.6 atmospheres absolute (ATA)]. On dive 4, before diving, all divers breathed 100% O2 for 20 min at 12 msw (HBO 2.2 ATA). Then they dove to 30 msw (4 ATA) for 20 min breathing air from scuba. After each dive, blood samples were collected as soon as the divers surfaced. Bubbles were measured at 20 and 50 min after decompression and converted to bubble count estimate (BCE) and numeric bubble grade (NBG). BCE and NBG were significantly lower in NBO than in Air [0.142+/-0.034 vs. 0.191+/-0.066 (P<0.05) and 1.61+/-0.25 vs. 1.89+/-0.31 (P<0.05), respectively] at 20 min, but not at 50 min. HBO at 1.6 ATA and 2.2 ATA has a similar significant effect of reducing BCE and NBG. BCE was 0.067+/-0.026 and 0.040+/-0.018 at 20 min and 0.030+/-0.022 and 0.020+/-0.020 at 50 min. NBG was 1.11+/-0.17 and 0.92+/-0.16 at 20 min and 0.83+/-0.18 and 0.75+/-0.16 at 50 min. Prebreathing NBO and HBO significantly alleviated decompression-induced platelet activation. Activation of CD62p was 3.0+/-0.4, 13.5+/-1.3, 10.7+/-0.9, 4.5+/-0.7, and 7.6+/-0.8% for baseline, Air, NBO, HBO at 1.6 ATA, and HBO at 2.2 ATA, respectively. The data show that prebreathing oxygen, more effective with HBO than NBO, decreases air bubbles and platelet activation and, therefore, may be beneficial in reducing the development of decompression sickness.
The incidence of adverse effects in our subjects was low and pre-chamber clinical selection appeared to be effective in reducing the risk of barotitis.
Pilot training and expertise are key aspects in aviation. A traditional way of evaluating pilot expertise is to measure performance output. However, this approach provides a narrow view of the pilot’s capacity, especially with regard to mental and emotional profile. The aim of this study is hence to investigate whether neurophysiological data can be employed as an additional objective measure to assess the expertise of pilots. In this regard, it has been demonstrated that mental effort can be used as an indirect measure of operator expertise and capacity. An increase in mental effort, for instance, can automatically result in a decrease in the remaining capacity of the operator. To better investigate this aspect, we ask two groups of Italian Air Force pilots, experienced (Experts) and unexperienced (Novices), to undergo unusual attitude recovery flight training simulations. Their behavioral (unusual attitude recovery time), subjective (mental effort demand perception) and neurophysiological data (Electroencephalogram, EEG; Electrocardiogram, ECG) are collected during the entire flight simulations. Although the two groups do not exhibit differences in terms of unusual attitude recovery time and mental effort demand perception, the EEG-based mental effort index shows how Novices request significantly higher mental effort during unusual conditions.
The prevalence of barotitis after hypobaric chamber training is low in our study, suggesting that a pre-chamber medical check including clinical examination and tympanometry could be effective in identifying subjects at risk.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.