title: Successive deep dives impair endothelial function and enhance oxidative stress in man.
abstract: The aim of this study was to assess the effects of successive deep dives on endothelial function of large conduit arteries and plasma pro-oxidant and antioxidant activity. Seven experienced divers performed six dives in six consecutive days using a compressed mixture of oxygen, helium and nitrogen (trimix) with diving depths ranging from 55 to 80 m. Before and after first, third and sixth dive, venous gas emboli formation and brachial artery function (flow-mediated dilation, FMD) was assessed by ultrasound. In addition, plasma antioxidant capacity (AOC) was measured by ferric reducing antioxidant power, and the level of oxidative stress was assessed by thiobarbituric acid-reactive substances (TBARS) method. Although the FMD was reduced to a similar extent after each dive, the comparison of predive FMD showed a reduction from 8.6% recorded before the first dive to 6.3% before the third (P = 0.03) and 5.7% before the sixth dive (P = 0.003). A gradual shift in baseline was also detected with TBARS assay, with malondialdehyde values increasing from 0.10 ± 0.02 μmol l⁻¹ before the first dive to 0.16 ± 0.03 before the sixth (P = 0.005). Predive plasma AOC values also showed a decreasing trend from 0.67 ± 0.20 mmol l⁻¹ trolox equivalents (first day) to 0.56 ± 0.12 (sixth day), although statistical significance was not reached (P = 0.08). This is the first documentation of acute endothelial dysfunction in the large conduit arteries occurring after successive deep trimix dives. Both endothelial function and plasma pro-oxidant and antioxidant activity did not return to baseline during the course of repetitive dives, indicating possible cumulative and longer lasting detrimental effects.
authors: Department of Physiology, University of Split School of Medicine, Soltanska 2, Split, Croatia.
authors: Ante
authors: A
authors: Obad
authors: Jasna
authors: J
authors: Marinovic
authors: Marko
authors: M
authors: Ljubkovic
authors: Toni
authors: T
authors: Breskovic
authors: Darko
authors: D
authors: Modun
authors: Mladen
authors: M
authors: Boban
authors: Zeljko
authors: Z
authors: Dujic
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D001916:Brachial Artery / Q000000981:diagnostic imaging / Q000503:physiopathology*; D017523:Croatia; D004242:Diving / Q000009:adverse effects*; D004618:Embolism, Air / Q000000981:diagnostic imaging / Q000209:etiology; D004730:Endothelium, Vascular / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008315:Malondialdehyde / Q000097:blood; D008875:Middle Aged; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D020127:Recovery of Function; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D013997:Time Factors; D014463:Ultrasonography; D014664:Vasodilation
chemical_list: D015415:Biomarkers; D017392:Thiobarbituric Acid Reactive Substances; D008315:Malondialdehyde