Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article


Master of Science




Shoemaker, J.K.

2nd Supervisor

Dickey, J.P.



Professional breath-hold diving has been linked to acute dangers; however, the long-term impacts on vascular health are unknown. The endothelium releases vasodilator substances and its functionality is an indicator of vascular health. We are testing the hypothesis that chronic exposure to severe hypoxia may alter endothelial function in breath hold divers. Divers and controls completed a flow-mediated dilation (FMD) protocol, where brachial blood flow velocity was measured following blood flow occlusion. Percent FMD was calculated as the primary measure of endothelial function. T-tests assessed the statistical significance of between-group differences. The %FMD were similar between groups (p >0.05); however, divers had reduced peak reactive hyperemia (PRH) compared to controls (p< 0.05). Accordingly, endothelial function was not altered in divers but they displayed reductions in PRH. This suggests that divers expressed a reduced microvascular dilatory response to ischemia, rather than impairments in endothelial function or the conduit artery response.