Effect of in-water oxygen prebreathing at different depths on decompression-induced bubble formation and platelet activation

Abstract

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.

Pre-dive Whole-Body Vibration Better Reduces Decompression-Induced Vascular Gas Emboli than Oxygenation or a Combination of Both

“…Nonetheless, Castagna et al found that oxygen prebreathing provides a significant reduction in decompression-induced bubble formation, regardless of the experimental conditions (Castagna et al, 2009). This is confirmed by the work of Bosco et al although hyperbaric oxygen seems more effective (Bosco et al, 2010). …”

“…Several practical, simple and feasible pre-dive measures have been studied such as endurance exercise (Blatteau et al, 2005; Castagna et al, 2011), pre-dive exposition to a warm environment (Blatteau et al, 2008), oral hydration (Gempp et al, 2009) or ingestion of dark chocolate (Theunissen et al, 2015). Others have tested the benefit of pre-dive oxygenation (Castagna et al, 2009; Bosco et al, 2010), or whole-body vibration (Germonpré et al, 2009). All of these studies show a positive effect with a significant decrease of post-dive VGE.…”

Exercise after SCUBA diving increases the incidence of arterial gas embolism

“…One alternative to this proposal is that a decrease in arterialization is related to an increased rate of nitrogen elimination, seen as a reduction of bubble load in the right heart. Oxygen prebreathing is used in high-altitude flights and astronaut extravehicular activity to eliminate nitrogen from the blood via an increased concentration gradient, and this principle has also been applied to SCUBA diving (2). This denucleation protocol can last between 1 and 4 h for high-altitude excursions (30).…”

Oxygen pretreatment as protection against decompression sickness in rats: pressure and time necessary for hypothesized denucleation and renucleation

“…However, it was chosen not to increase the number of animals solely for that purpose. Bosco et al (2010) have shown in divers that in-water oxygen prebreathing at a depth of 6 msw or 12 msw yielded lower bubble scores than prebreathing oxygen at the surface. Their Wndings agree with the evidence for increased protection against DCS as the prebreathe oxygen pressure increases.…”

“…Three studies on humans pretreated with pure oxygen, at normobaric pressure for 30 min, 1.6 ATA for 45 min, and 1.0, 1.6, or 2.2 ATA for 20 min, are encouraging (Bosco et al 2010;Castagna et al 2009;LandolW et al 2006).…”