Ratio of venous-to-arterial PCO2 to arteriovenous oxygen content difference during regional ischemic or hypoxic hypoxia

Abstract The purpose of the study was to evaluate the behavior of the venous-to-arterial CO2 tension difference (ΔPCO2) over the arterial-to-venous oxygen content difference (ΔO2) ratio (ΔPCO2/ΔO2) and the difference between venous-to-arterial CO2 content calculated with the Douglas’ equation (ΔCCO2...

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Autores principales:	Jihad Mallat, Benoit Vallet
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2021
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/0db96d97dbb44dab9725c86f78089e1f
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spelling	oai:doaj.org-article:0db96d97dbb44dab9725c86f78089e1f2021-12-02T17:15:24ZRatio of venous-to-arterial PCO2 to arteriovenous oxygen content difference during regional ischemic or hypoxic hypoxia10.1038/s41598-021-89703-52045-2322https://doaj.org/article/0db96d97dbb44dab9725c86f78089e1f2021-05-01T00:00:00Zhttps://doi.org/10.1038/s41598-021-89703-5https://doaj.org/toc/2045-2322Abstract The purpose of the study was to evaluate the behavior of the venous-to-arterial CO2 tension difference (ΔPCO2) over the arterial-to-venous oxygen content difference (ΔO2) ratio (ΔPCO2/ΔO2) and the difference between venous-to-arterial CO2 content calculated with the Douglas’ equation (ΔCCO2D) over ΔO2 ratio (ΔCCO2D/ΔO2) and their abilities to reflect the occurrence of anaerobic metabolism in two experimental models of tissue hypoxia: ischemic hypoxia (IH) and hypoxic hypoxia (HH). We also aimed to assess the influence of metabolic acidosis and Haldane effects on the PCO2/CO2 content relationship. In a vascularly isolated, innervated dog hindlimb perfused with a pump-membrane oxygenator system, the oxygen delivery (DO2) was lowered in a stepwise manner to decrease it beyond critical DO2 (DO2crit) by lowering either arterial PO2 (HH-model) or flow (IH-model). Twelve anesthetized and mechanically ventilated dogs were studied, 6 in each model. Limb DO2, oxygen consumption ( $${\dot{\text{V}}\text{O}}_{2}$$ V ˙ O 2 ), ΔPCO2/ΔO2, and ΔCCO2D/ΔO2 were obtained every 15 min. Beyond DO2crit, $${\dot{\text{V}}\text{O}}_{2}$$ V ˙ O 2 decreased, indicating dysoxia. ΔPCO2/ΔO2, and ΔCCO2D/ΔO2 increased significantly only after reaching DO2crit in both models. At DO2crit, ΔPCO2/ΔO2 was significantly higher in the HH-model than in the IH-model (1.82 ± 0.09 vs. 1.39 ± 0.06, p = 0.002). At DO2crit, ΔCCO2D/ΔO2 was not significantly different between the two groups (0.87 ± 0.05 for IH vs. 1.01 ± 0.06 for HH, p = 0.09). Below DO2crit, we observed a discrepancy between the behavior of the two indices. In both models, ΔPCO2/ΔO2 continued to increase significantly (higher in the HH-model), whereas ΔCCO2D/ΔO2 tended to decrease to become not significantly different from its baseline in the IH-model. Metabolic acidosis significantly influenced the PCO2/CO2 content relationship, but not the Haldane effect. ΔPCO2/ΔO2 was able to depict the occurrence of anaerobic metabolism in both tissue hypoxia models. However, at very low DO2 values, ΔPCO2/ΔO2 did not only reflect the ongoing anaerobic metabolism; it was confounded by the effects of metabolic acidosis on the CO2–hemoglobin dissociation curve, and then it should be interpreted with caution.Jihad MallatBenoit ValletNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 11, Iss 1, Pp 1-8 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Jihad Mallat Benoit Vallet Ratio of venous-to-arterial PCO2 to arteriovenous oxygen content difference during regional ischemic or hypoxic hypoxia
description	Abstract The purpose of the study was to evaluate the behavior of the venous-to-arterial CO2 tension difference (ΔPCO2) over the arterial-to-venous oxygen content difference (ΔO2) ratio (ΔPCO2/ΔO2) and the difference between venous-to-arterial CO2 content calculated with the Douglas’ equation (ΔCCO2D) over ΔO2 ratio (ΔCCO2D/ΔO2) and their abilities to reflect the occurrence of anaerobic metabolism in two experimental models of tissue hypoxia: ischemic hypoxia (IH) and hypoxic hypoxia (HH). We also aimed to assess the influence of metabolic acidosis and Haldane effects on the PCO2/CO2 content relationship. In a vascularly isolated, innervated dog hindlimb perfused with a pump-membrane oxygenator system, the oxygen delivery (DO2) was lowered in a stepwise manner to decrease it beyond critical DO2 (DO2crit) by lowering either arterial PO2 (HH-model) or flow (IH-model). Twelve anesthetized and mechanically ventilated dogs were studied, 6 in each model. Limb DO2, oxygen consumption ( $${\dot{\text{V}}\text{O}}_{2}$$ V ˙ O 2 ), ΔPCO2/ΔO2, and ΔCCO2D/ΔO2 were obtained every 15 min. Beyond DO2crit, $${\dot{\text{V}}\text{O}}_{2}$$ V ˙ O 2 decreased, indicating dysoxia. ΔPCO2/ΔO2, and ΔCCO2D/ΔO2 increased significantly only after reaching DO2crit in both models. At DO2crit, ΔPCO2/ΔO2 was significantly higher in the HH-model than in the IH-model (1.82 ± 0.09 vs. 1.39 ± 0.06, p = 0.002). At DO2crit, ΔCCO2D/ΔO2 was not significantly different between the two groups (0.87 ± 0.05 for IH vs. 1.01 ± 0.06 for HH, p = 0.09). Below DO2crit, we observed a discrepancy between the behavior of the two indices. In both models, ΔPCO2/ΔO2 continued to increase significantly (higher in the HH-model), whereas ΔCCO2D/ΔO2 tended to decrease to become not significantly different from its baseline in the IH-model. Metabolic acidosis significantly influenced the PCO2/CO2 content relationship, but not the Haldane effect. ΔPCO2/ΔO2 was able to depict the occurrence of anaerobic metabolism in both tissue hypoxia models. However, at very low DO2 values, ΔPCO2/ΔO2 did not only reflect the ongoing anaerobic metabolism; it was confounded by the effects of metabolic acidosis on the CO2–hemoglobin dissociation curve, and then it should be interpreted with caution.
format	article
author	Jihad Mallat Benoit Vallet
author_facet	Jihad Mallat Benoit Vallet
author_sort	Jihad Mallat
title	Ratio of venous-to-arterial PCO2 to arteriovenous oxygen content difference during regional ischemic or hypoxic hypoxia
title_short	Ratio of venous-to-arterial PCO2 to arteriovenous oxygen content difference during regional ischemic or hypoxic hypoxia
title_full	Ratio of venous-to-arterial PCO2 to arteriovenous oxygen content difference during regional ischemic or hypoxic hypoxia
title_fullStr	Ratio of venous-to-arterial PCO2 to arteriovenous oxygen content difference during regional ischemic or hypoxic hypoxia
title_full_unstemmed	Ratio of venous-to-arterial PCO2 to arteriovenous oxygen content difference during regional ischemic or hypoxic hypoxia
title_sort	ratio of venous-to-arterial pco2 to arteriovenous oxygen content difference during regional ischemic or hypoxic hypoxia
publisher	Nature Portfolio
publishDate	2021
url	https://doaj.org/article/0db96d97dbb44dab9725c86f78089e1f
work_keys_str_mv	AT jihadmallat ratioofvenoustoarterialpco2toarteriovenousoxygencontentdifferenceduringregionalischemicorhypoxichypoxia AT benoitvallet ratioofvenoustoarterialpco2toarteriovenousoxygencontentdifferenceduringregionalischemicorhypoxichypoxia
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Ratio of venous-to-arterial PCO2 to arteriovenous oxygen content difference during regional ischemic or hypoxic hypoxia

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