influence of oxygen enriched gases during decompression on bubble formation and endothelial function in selfcontained underwater breathing apparatus diving a randomized controlled study aim to 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 vascularendothelial function during decompression after selfcontained underwater breathing apparatus divingmethods this 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 arterialendothelial function was evaluated by brachial artery flow mediated dilatation fmd before and after diveresults nitrox 99 significantly reduced bubble formation after cough compared with air and nitrox 50 grade 1 vs 3 and vs 3 respectively p0026 nitrox 50 significantly decreased postdive fmd compared with predive fmd 362557 vs 1211682 p0010 while nitrox 99 did not cause any significant changeconclusion nitrox 99 reduced bubble formation did not change postdive fmd and decreased total dive duration indicating that it might better preserve endothelial function compared with air and nitrox 50 dive protocols