The impact of different gas mixtures on inflammatory responses in advanced recreational divers

INTRODUCTION: Decompression sickness (DCS) is considered a 'bubble disease'. Intravascular bubbles activate inflammatory responses associated with endothelial dysfunction. Breathing gas has been proposed as a potential risk factor but this is inadequately studied. Different gases are used in scuba diving. Helium-containing 'trimix' could theoretically mitigate inflammation and therefore reduce DCS risk. This study determined the effect of air and trimix on the inflammatory response following dives to 50 metres of sea water, and evaluated the differences between them in advanced recreational divers. METHODS: Thirty-three divers were enrolled in this observational study and were divided in two groups: 17 subjects were included in the air group, and 16 different subjects were included in the trimix (21% oxygen, 35% helium, 44% nitrogen) group. Each subject conducted a single dive, and both groups used a similar diving profile of identical duration. A venous blood sample was taken 30 min before diving and 2 h after surfacing to evaluate changes in interleukins (IL) IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, tumour necrosis factor α (TNFα), vascular endothelial growth factor (VEGF), Interferon γ (IFN-γ), monocyte chemoattractant protein 1 (MCP-1) and epithelial growth factor (EGF) after diving. RESULTS: No differences were observed between groups in demographic data or diving experience. Following the dive, IL-6 values showed a slight increase, while IL-8 and EGF decreased in both groups, without significant variation between the groups. CONCLUSIONS: In physically fit divers, trimix and air gas mixture during deep diving did not cause relevant changes in the inflammatory markers tested.