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Ran Arieli1,2*- 1Israel Naval Medical Institute, Israel Defense Forces Medical Corps, Haifa, Israel
- 2Eliachar Research Laboratory, Western Galilee Medical Center, Nahariya, Israel
A Commentary on
Arterial blood gases in SCUBA divers at depth
By Paganini M, Zucchi L, Giacon TA, Martani L, Mrakic-Sposta S, Garetto G, McKnight JC, Camporesi EM, Moon RE and Bosco G (2024) Front. Mar. Sci. 11:1445692. doi: 10.3389/fmars.2024.1445692
In a recent interesting study (Paganini et al., 2024), arterial PO2 was measured while diving to 15 m and 42 m of freshwater (mfw). It was explored whether calculation of arterial PO2 at depth could use the arterial/alveolar [partial pressures of oxygen ratio (a:A ratio)] at 1 ATA, as suggested by Moon et al. (1987). The a:A ratio calculated from the baseline arterial blood gases obtained at rest, out of the water, adequately predicted the PaO2 at depth. However, at the greater depth of 22 mfw, the calculation proved to be inaccurate. In addition, Weaver and Howe (1992) presented higher PaO2 than that predicted by the a:A ratio.
Although the slower diffusion while breathing dense gas should increase the alveolar–arterial difference in PO2 (A-a)DO2, it is well documented that breathing dense gas begets an opposite result and reduces the (A-a)DO2. During the breathing cycle, pressure reduction at inspiration causes an increase in venous return. Thus, during normal breathing, lung perfusion increases by 18% at inspiration. With the increase in gas density, breathing resistance is increased, and so there is an increase in pressure swings during the breathing cycle. This would cause an increase in tidal perfusion in the lung. When the increase in alveolar PO2 during inspiration meets an increased perfusion, higher oxygenation is expected. Thus, the decrease in (A-a)DO2 can be related to better timing between perfusion and elevated PAO2. Modeling this assumption in a single-compartment lung, Arieli and Farhi (1985) presented that at dense gas breathing, (A-a)DO2 was reduced by 2 torr. Expanding the model to nine vertical differently perfused lung compartments, Arieli (1992) calculated a decreased (A-a)DO2 by 4–5 torr. The increase in cycling perfusion of the lung at a high pressure would explain why the a:A prediction would be inaccurate at the high pressure. Therefore, I claim that in any discussion of arterial PO2 at high pressure, cycling perfusion in the lung must be considered.
Author contributions
RA: Writing – original draft, Writing – review & editing.
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The author(s) declare that no financial support was received for the research, authorship, and/or publication of this article.
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References
Arieli R. (1992). Cyclic perfusion of the lung by dense gas breathing may reduce the (A- a)DO2. J. Basic Clin. Physiol. Pharmacol. 3, 207–221. doi: 10.1515/jbcpp.1992.3.3.207
Arieli R., Farhi L. E. (1985). Gas exchange in tidally ventilated and non-steadily perfused lung model. Respir. Physiol. 60, 297–309. doi: 10.1016/0034-5687(85)90059-3
Moon R., Camporesi E., Shelton D. (1987). “Prediction of arterial PO2 during hyperbaric treatment,” in Proceedings of the Ninth International Symposium on Underwater and Hyperbaric Physiology (Undersea & Hyperbaric Medical Society, Bethesda, MD), 1127–1131.
Paganini M., Zucchi L., Giacon T. A., Martani L., Mrakic-Sposta S., Garetto G., et al. (2024). Arterial blood gases in SCUBA divers at depth. Front. Mar. Sci. 11. doi: 10.3389/fmars.2024.144569
Keywords: high pressure, diving, arterial oxygen, dense gas, depth
Citation: Arieli R (2025) Commentary: Arterial blood gases in SCUBA divers at depth. Front. Mar. Sci. 12:1557303. doi: 10.3389/fmars.2025.1557303
Received: 09 January 2025; Accepted: 03 February 2025;
Published: 05 March 2025.
Edited by:
Pieter-Jan A.M. Van Ooij, Royal Netherlands Navy, NetherlandsReviewed by:
Ingrid Eftedal, Norwegian University of Science and Technology, NorwayCopyright © 2025 Arieli. 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) and the copyright owner(s) 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: Ran Arieli, YXJpZWxpMTk0MEBnbWFpbC5jb20=