• Ivana Šegrt Ribičić, Maja Valić, Joško Božić, Ante Obad, Duška Glavaš, Igor Glavičić, and Zoran Valić.
• Maja Valić, Department of Neuroscience, University of Split School of Medicine, Soltanska 2, 21000 Split, Croatia, maja.valic@mefst.hr.
• Croat. Med. J. 2019 Jun 13; 60 (3): 265-272.

AimTo assess the effect of air, gas mixture composed of 50% nitrogen and 50% oxygen (nitrox 50), or gas mixture composed of 1% nitrogen and 99% oxygen (nitrox 99) on bubble formation and vascular/endothelial function during decompression after self-contained underwater breathing apparatus diving.MethodsThis randomized controlled study, conducted in 2014, involved ten divers. Each diver performed three dives in a randomized protocol using three gases: air, nitrox 50, or nitrox 99 during ascent. The dives were performed on three different days limited to 45 m sea water (msw) depth with 20 min bottom time. Nitrogen bubbles formation was assessed by ultrasound detection after dive. Arterial/endothelial function was evaluated by brachial artery flow mediated dilatation (FMD) before and after dive.ResultsNitrox 99 significantly reduced bubble formation after cough compared with air and nitrox 50 (grade 1 vs 3 and vs 3, respectively, P=0.026). Nitrox 50 significantly decreased post-dive FMD compared with pre-dive FMD (3.62 ± 5.57% vs 12.11 ± 6.82% P=0.010), while nitrox 99 did not cause any significant change.ConclusionNitrox 99 reduced bubble formation, did not change post-dive FMD, and decreased total dive duration, indicating that it might better preserve endothelial function compared with air and nitrox 50 dive protocols.

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