AUTHOR=Bosco Gerardo , Rizzato Alex , Martani Luca , Schiavo Simone , Talamonti Ennio , Garetto Giacomo , Paganini Matteo , Camporesi Enrico M. , Moon Richard E. 

TITLE=Arterial Blood Gas Analysis in Breath-Hold Divers at Depth

JOURNAL=Frontiers in Physiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2018.01558

DOI=10.3389/fphys.2018.01558

ISSN=1664-042X

ABSTRACT=<p>The present study aimed to evaluate the partial pressure of arterial blood gases in breath-hold divers performing a submersion at 40 m. Eight breath-hold divers were enrolled for the trials held at “Y-40 THE DEEP JOY” pool (Montegrotto Terme, Padova, Italy). Prior to submersion, an arterial cannula in the radial artery of the non-dominant limb was positioned. All divers performed a sled-assisted breath-hold dive to 40 m. Three blood samplings occurred: at 10 min prior to submersion, at 40 m depth, and within 2 min after diver’s surfacing and after resuming normal ventilation. Blood samples were analyzed immediately on site. Six subjects completed the experiment, without diving-related problems. The theoretically predicted hyperoxia at the bottom was observed in 4 divers out of 6, while the other 2 experienced a reduction in the partial pressure of oxygen (paO<sub>2</sub>) at the bottom. There were no significant increases in arterial partial pressure of carbon dioxide (paCO<sub>2</sub>) at the end of descent in 4 of 6 divers, while in 2 divers paCO<sub>2</sub> decreased. Arterial mean pH and mean bicarbonate (<inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mrow><mml:mi mathcolor="black" mathvariant="normal">HCO</mml:mi></mml:mrow><mml:mrow><mml:mi mathcolor="black" mathvariant="normal">3</mml:mi></mml:mrow><mml:mrow><mml:mn mathcolor="black" mathvariant="normal">−</mml:mn></mml:mrow></mml:msubsup></mml:mrow></mml:math></inline-formula>) levels exhibited minor changes. There was a statistically significant increase in mean arterial lactate level after the exercise. Ours was the first attempt to verify real changes in blood gases at a depth of 40 m during a breath-hold descent in free-divers. We demonstrated that, at depth, relative hypoxemia can occur, presumably caused by lung compression. Also, hypercapnia exists at depth, to a lesser degree than would be expected from calculations, presumably because of pre-dive hyperventilation and carbon dioxide distribution in blood and tissues.</p>