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Blunted hypoxic pulmonary vasoconstriction in apnoea divers

journal contribution
posted on 12.09.2022, 13:54 authored by Tyler Kelly, Courtney Brown, Mohini Bryant-Ekstrand, Rachel LordRachel Lord, Tony DawkinsTony Dawkins, Aimee DraneAimee Drane, Joel E. Futral, Otto Barak, Tanja Dragun, Michael StembridgeMichael Stembridge, Boris Spajić, Ivan Drvis, Joseph W. Duke, Philip N. Ainslie, Glen E. Foster, Zeljko Dujic, Andrew T. Lovering

 Competitive apnoea divers repetitively dive to depths beyond 50 m. During the final portions of ascent, Divers experience significant hypoxaemia. Additionally, hyperbaria during diving increases thoracic blood volume while simultaneously reducing lung volume, increasing pulmonary artery pressure. We hypothesized that Divers would have exaggerated hypoxic pulmonary vasoconstriction leading to increased right-heart work due to their repetitive hypoxaemia and hyperbaria, and that the administration of sildenafil would have a greater effect in reducing pulmonary resistance in Divers. We recruited 16 Divers and 16 age and sex matched non-diving controls (Controls). Using a double-blinded, placebo-controlled, cross-over design, participants were evaluated for normal cardiac and lung function, then their cardiopulmonary responses to 20–30 minutes of isocapnic hypoxia (end-tidal PO2 = 50 mm Hg) were measured one hour following ingestion of 50 mg sildenafil or placebo. Cardiac structure and cardiopulmonary function were similar at baseline. With placebo, Divers had a significantly smaller increase in total pulmonary resistance than controls after 20–30 minutes isocapnic hypoxia (Δ -3.85 ± 72.85 vs 73.74 ± 91.06 dynes/sec/cm–5, p = .0222). With sildenafil, Divers and Controls had similarly blunted increases in total pulmonary resistance after 20–30 minutes of hypoxia. Divers also had a significantly lower systemic vascular resistance following sildenafil in normoxia. These data indicate that repetitive apnoea diving leads to a blunted hypoxic pulmonary vasoconstriction. We suggest this is a beneficial adaption allowing for increased cardiac output with reduced right heart work and thus reducing cardiac oxygen utilization under hypoxemic conditions. 

History

Published in

Experimental Physiology

Publisher

Wiley

Version

AM (Accepted Manuscript)

Citation

Kelly, T., Brown, C., Bryant‐Ekstrand, M., Lord, R., Dawkins, T., Drane, A., Futral, J.E., Barak, O., Dragun, T., Stembridge, M. and Spajić, B. (2022) 'Blunted hypoxic pulmonary vasoconstriction in apnoea divers', Experimental Physiology. DOI: 10.1113/EP090326

Print ISSN

0958-0670

Electronic ISSN

1469-445X

Cardiff Met Affiliation

  • Cardiff School of Sport and Health Sciences

Cardiff Met Authors

Rachel Lord Tony Dawkins Aimee Drane Mike Stembridge

Cardiff Met Research Centre/Group

  • Cardiovascular Physiology

Copyright Holder

© The Publisher

Language

en

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