In his commentary (Arieli, 2025), Dr. Arieli has pointed out that in a series of arterial blood gas measurements in divers at 15 and 42 meters of freshwater (mfw), using a prediction method based on constant arterial:alveolar (a:A) PO2 ratio (Moon et al., 1987), the predicted arterial PO2 at the greater depth was inaccurate (Paganini et al., 2024). Indeed, at predicted PO2 values in the range of 650–750 mmHg measured values were significantly lower: 427–511 mmHg. He suggests that this might be due to augmented tidal changes in perfusion as a result of the breathing cycle and greater gas density. Arieli has proposed this plausible mechanism to explain why arterial PO2 might be higher than expected during diving (Arieli, 1992). He notes that this is supported by the observations of Weaver (Weaver and Howe, 1992), where arterial PO2 was higher than predicted by the constant a:A ratio.
However, in our case the measured PO2 was lower than predicted. All of the measurements in this study were obtained at 1 ATA, with predicted arterial PO2’s close to atmospheric pressure (around 760 mmHg at sea level). Accurate calibration of any blood gas analyzer requires a two-point calibration below and above the unknown blood sample. During this experiment the measurements were obtained at 1 ATA, where a high point calibration is not possible for a PO2 close to or exceeding ambient pressure minus water vapor pressure (around 713 mmHg). Similarly, in Weaver’s report of PO2 values in volunteers in a hyperbaric chamber measured at 1 ATA, for which an empirical correction algorithm was developed (Weaver and Howe, 1992). On the other hand, the hyperbaric measurements reported by Moon et al. up to PO2 values close to 1,700 mmHg (Moon et al., 1987) were obtained using an arterial blood gas machine calibrated inside the hyperbaric chamber. Additionally, blood samples with high PO2 are inordinately predisposed to erroneously low measurements due to diffusion of oxygen from the sample into small gas bubbles that may be present in the syringe, as may have been the case in the highest values reported by Moon (Moon et al., 1987).
We believe therefore that the measurements at 42 mfw were artifactually low due to the challenge of accurate calibration of the PO2 electrode.
Statements
Author contributions
RM: Writing – original draft, Writing – review & editing. MP: Writing – original draft, Writing – review & editing. EC: Writing – original draft, Writing – review & editing. GB: Writing – original draft, Writing – review & editing.
Funding
The author(s) declare financial support was received for the research and/or publication of this article. Funding for this research was provided by the Office of Naval Research (Grant No. N00014-23-1-2757). Open Access funding provided by Università degli Studi di Padova | University of Padua, Open Science Committee.
Conflict of interest
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision.
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The author(s) declare that no Generative AI was used in the creation of this manuscript.
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All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.
References
1
ArieliR. (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
2
ArieliR. (2025). Commentary: Arterial blood gases in SCUBA divers at depth. Front. Mar. Sci.12. doi: 10.3389/fmars.2025.1557303
3
MoonR. E.CamporesiE. M.SheltonD. L.Greenbaum (1987). “Prediction of arterial PO2 during hyperbaric treatment,” in Underwater and hyperbaric physiology IX. Proceedings of the ninth international symposium on underwater and hyperbaric physiology. Eds. BoveA. A.BachrachA. J. (Undersea and Hyperbaric Medical Society, Bethesda, MD), 1127–1131.
4
PaganiniM.ZucchiL.GiaconT. A.MartaniL.Mrakic-SpostaS.GarettoG.et al. (2024). Arterial blood gases in SCUBA divers at depth. Front. Mar. Sci.11. doi: 10.3389/fmars.2024.1445692
5
WeaverL. K.HoweS. (1992). Normobaric measurement of arterial oxygen tension in subjects exposed to hyperbaric oxygen. Chest102, 1175–1181. doi: 10.1378/chest.102.4.1175
Summary
Keywords
SCUBA diving, arterial blood gas, environmental physiology, diving physiology, oxygen
Citation
Moon RE, Paganini M, Camporesi EM and Bosco G (2025) Response: Commentary: Arterial blood gases in SCUBA divers at depth. Front. Mar. Sci. 12:1611509. doi: 10.3389/fmars.2025.1611509
Received
14 April 2025
Accepted
18 July 2025
Published
09 September 2025
Volume
12 - 2025
Edited by
Mark R. Patterson, Northeastern University, United States
Reviewed by
Arnaud Druelle, L’Hôpital d’Instruction des Armées Sainte-Anne, France
Updates
Copyright
© 2025 Moon, Paganini, Camporesi and Bosco.
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: Gerardo Bosco, gerardo.bosco@unipd.it
Disclaimer
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.