Kjeld Thomas, Isbrand Anders Brenøe, Arendrup Henrik Christian, Højberg Jens, Bejder Jacob, Krag Thomas O, Vissing John, Tolbod Lars Poulsen, Harms Johannes Hendrik, Gormsen Lars Christian, Fuglø Dan, Hansen Egon Godthaab
Department of Anesthesiology, Herlev Hospital, University of Copenhagen, Copenhagen, Denmark.
Department of Clinical Medicine, Faculty of Medicine, University of Copenhagen, Copenhagen, Denmark.
Front Physiol. 2024 Jul 31;15:1296537. doi: 10.3389/fphys.2024.1296537. eCollection 2024.
Elite breath-hold divers (BHD) possess several oxygen conserving adaptations to endure long dives similar to diving mammals. During dives, Bottlenose Dolphins may increase the alveolar ventilation (V) to perfusion (Q) ratio to increase alveolar oxygen delivery. We hypothesized that BHD possess similar adaptive mechanisms during apnea.
Pulmonary blood volume (PBV) was determined by echocardiography, O-HO PET/CT, and cardiac MRi, (n = 6) during and after maximum apneas. Pulmonary function was determined by body box spirometry and compared to matched controls. After 2 min of apnea, the PBV determined by echocardiography and O-HO-PET/CT decreased by 26% and 41%, respectively. After 4 min of apnea, the PBV assessed by echocardiography and cardiac MRi decreased by 48% and 67%, respectively (n = 6). Fractional saturation (F)OHb determined by arterial blood-gas-analyses collected after warm-up and a 5-minute pool-apnea (n = 9) decreased by 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.
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 decrease PBV during apnea and in turn increase V/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.
This manuscript addresses novel knowledge on tolerance to hypoxia during diving, which is shared by elite breath-hold divers and adult diving mammals: Our study indicates that elite breath-hold divers gradually decrease pulmonary blood volume and in turn increase VA/Q, to increase alveolar oxygen delivery during maximum apnea to tolerate decreasing oxygen levels similar to the Bottlenose Dolphin.
精英屏气潜水者（BHD）具备多种氧气保存适应机制，以耐受与潜水哺乳动物类似的长时间潜水。在潜水过程中，宽吻海豚可能会提高肺泡通气（V）与灌注（Q）比值，以增加肺泡氧气输送。我们假设BHD在屏气期间具有类似的适应机制。
通过超声心动图、O-HO PET/CT和心脏磁共振成像（n = 6）在最大屏气期间及之后测定肺血容量（PBV）。通过体箱肺量计测定肺功能，并与匹配的对照组进行比较。屏气2分钟后，超声心动图和O-HO-PET/CT测定的PBV分别下降了26%和41%。屏气4分钟后，超声心动图和心脏磁共振成像评估的PBV分别下降了48%和67%（n = 6）。热身和5分钟泳池屏气后采集的动脉血气分析测定的氧合血红蛋白分数饱和度（F）OHb下降了43%。与匹配的对照组（n = 8）相比，肺量计显示BHD（n = 9）的总肺容量和肺泡肺容量更高，但扩散常数更低。
我们的结果与之前的研究形成对比，之前的研究表明BHD和匹配的对照组在肺气体交换方面相似。我们得出结论，精英BHD 1）的扩散常数低于匹配的对照组，2）在屏气期间逐渐降低PBV，进而增加V/Q以在最大屏气期间增加肺泡氧气输送。我们认为BHD具有与潜水哺乳动物类似的肺部适应能力，以耐受组织氧合降低。
本手稿阐述了关于潜水期间对缺氧耐受性的新知识，这是精英屏气潜水者和成年潜水哺乳动物所共有的：我们的研究表明，精英屏气潜水者逐渐减少肺血容量，进而增加VA/Q，以在最大屏气期间增加肺泡氧气输送，从而耐受与宽吻海豚类似的氧水平降低。
