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ORIGINAL RESEARCH article

Front. Physiol.
Sec. Respiratory Physiology and Pathophysiology
Volume 15 - 2024 | doi: 10.3389/fphys.2024.1296537

Pulmonary vascular adaptations to hypoxia during maximum apnea in elite breath hold divers

Provisionally accepted
Thomas Kjeld Thomas Kjeld 1*Anders Isbrand Anders Isbrand 2Henrik C. Arendrup Henrik C. Arendrup 2Jens Højberg Jens Højberg 3Jacob Bejder Jacob Bejder 4Thomas O. Krag Thomas O. Krag 5John Vissing John Vissing 5Lars P. Tolbod Lars P. Tolbod 6Lars C. Gormsen Lars C. Gormsen 6Dan Fuglø Dan Fuglø 7Egon G. Hansen Egon G. Hansen 8
  • 1 Copenhagen Neuromuscular Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
  • 2 Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Capital Region of Denmark, Denmark
  • 3 Department of Cardiothoracic Anesthesiology, Rigshospitalet, University of Copenhagen, Copenhagen, Capital Region of Denmark, Denmark
  • 4 Department of Nutrition, Exercise and Sports, Faculty of Natural and Life Sciences, University of Copenhagen, Copenhagen, Capital Region of Denmark, Denmark
  • 5 Department of Neurology, Rigshospitalet, University of Copenhagen, Copenhagen, Capital Region of Denmark, Denmark
  • 6 Department of Nuclear Medicine and PET Center, Aarhus University Hospital, Aarhus, Denmark
  • 7 Department of Nuclear Medicine, Herlev Hospital, Herlev, Denmark
  • 8 Department of Anesthesiology, Herlev Hospital, University of Copenhagen, Copenhagen, Denmark

The final, formatted version of the article will be published soon.

    Introduction: Elite breath hold divers (BHD) possess several oxygen conserving adaptations to endure long dives similar to diving mammals like the Dolphin. During dives, Bottlenose Dolphins may increase the alveolar ventilation (VA) to perfusion (Q) ratio to increase alveolar oxygen delivery. We hypothesized that BHD possess similar adaptive mechanisms during apnea. Methods and results: Pulmonary blood volume (PBV) was determined by echocardiography, 15O-H2O-PET/CT, and cardiac MRi, whereas the oxygen binding properties of the hemoglobin was quantified by arterial blood gas analyses before, during and after maximum pool apneas. Pulmonary function was determined by body box spirometry and compared to matched controls. After 2 min of apnea, PBV determined by echocardiography and 15O-H2O-PET/CT decreased 26% and 41%, respectively. After 4 min of apnea, PBV assessed by echocardiography and cardiac MRi decreased further by 48% and 67%, respectively (n=6). Fractional saturation (F)O2Hb determined by arterial blood-gas-analyses collected after warm-up and a 5-minute pool-apnea (n=9) decreased 43%. Compared to matched controls (n=8), spirometry revealed a higher total and alveolar-lung-capacity in BHD (n=9), but a lower diffusion-constant. Conclusion: Our results contrast with previous studies, that demonstrated similar lung gas transfer in BHD and matched controls. We conclude that elite BHD 1) have a lower diffusion-constant than matched controls, and 2) gradually decreases PBV during apnea and in turn increases VA/Q to increase alveolar oxygen delivery during maximum apnea. We suggest that BHD possess pulmonary adaptations similar to diving mammals to tolerate decreasing tissue-oxygenation.

    Keywords: cardiac MR (CMR), Cardiac PET/CT, Echocardiagraphy, Freediving, pulmonary vascular adaptions

    Received: 19 Sep 2023; Accepted: 24 Jun 2024.

    Copyright: © 2024 Kjeld, Isbrand, Arendrup, Højberg, Bejder, Krag, Vissing, Tolbod, Gormsen, Fuglø and Hansen. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Thomas Kjeld, Copenhagen Neuromuscular Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark

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