Commentary on Viewpoint: Revisiting the effects of the reciprocal function between alveolar ventilation and CO 2 partial pressure (PACO2) on PACO2 homeostasis at rest and in exercise.

ViewpointCommentary on Viewpoint: Revisiting the effects of the reciprocal function between alveolar ventilation and CO2 partial pressure (PACO2) on PACO2 homeostasis at rest and in exercisePublished Online:04 Oct 2022https://doi.org/10.1152/japplphysiol.00468.2022MoreSectionsPDF (114 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat The neglected role of carbon dioxide storesLorenzo Giosa,12 Giulia Roveri,3 and Mattia Busana4.Author Affiliations1Centre for Human and Applied Physiological Sciences, King’s College London, London, United Kingdom.2Department of Intensive Care, Guy’s and St. Thomas’ NHS Foundation Trust, London, United Kingdom.3Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy.4Department of Anesthesiology, University Medical Center Göttingen, Gottingen, Germany.to the editor: Haouzi (1) showed that the plant gain [i.e., the absolute change in alveolar partial pressure of carbon dioxide (PACO2) for a given change in alveolar ventilation (V̇a)] is a function of V̇a, metabolic CO2 production (V̇co2), and inspired carbon dioxide fraction (PICO2). However, especially in the intensive care unit (ICU), it is worth remembering that the kinetics of PACO2 (i.e., how fast the expected PACO2 is reached) are also strongly dependent on the pool of whole body CO2 stores. Recent studies (2) have confirmed the model of Cherniack (3), suggesting that when the system is stressed (by changes in V̇a or V̇co2) the time needed to reach the new equilibrium (i.e., the new PACO2 imposed by the plant gain) is a function of the amount of CO2 body stores and of their perfusion. About 1.75 L/kg of CO2 is stored in the healthy adult human body, but the pool can substantially increase during stable [e.g., chronic obstructive pulmonary disease (COPD)] (4) or permissive [e.g., acute respiratory distress syndrome (ARDS)] hypercapnia (5). These situations are frequently encountered in the ICU, where cardiac output (a reflection of CO2 stores perfusion) is also highly variable as a consequence of sedation and positive pressure ventilation. This physiological background may help interpret some ICU-related stressful events like weaning from mechanical ventilation: here, the interplay between possible long-term hypercapnia (affecting the amount of stored CO2) and liberation from sedation and positive intrathoracic pressure (affecting their perfusion) may lead to unpredictable dynamic changes in PACO2, with variable consequences on the patient’s breathing pattern.DISCLOSURESNo conflicts of interest, financial or otherwise, are declared by the authors.REFERENCES1. Haouzi P. Revisiting the effects of the reciprocal function between alveolar ventilation and CO2 partial pressure (PaCO2) on PaCO2 homeostasis at rest and in exercise. J Appl Physiol (1985). doi:10.1152/japplphysiol.00058.2022. Link | Google Scholar2. Giosa L, Busana M, Bonifazi M, Romitti F, Vassalli F, Pasticci I, Macri MM, D’Albo R, Collino F, Gatta A, Palumbo MM, Herrmann P, Moerer O, Iapichino G, Meissner K, Quintel M, Gattinoni L. Mobilizing carbon dioxide stores. An experimental study. Am J Respir Crit Care Med 203: 318–327, 2021. doi:10.1164/rccm.202005-1687OC. Crossref | PubMed | ISI | Google Scholar3. Cherniack NS, Longobardo GS. Oxygen and carbon dioxide gas stores of the body. Physiol Rev 50: 196–243, 1970. doi:10.1152/physrev.1970.50.2.196.Link | ISI | Google Scholar4. Pisani L, Nava S, Desiderio E, Polverino M, Tonetti T, Ranieri VM. Extracorporeal CO 2 removal (ECCO 2 R) in patients with stable COPD with chronic hypercapnia: a proof-of-concept study. Thorax 75: 897–900, 2020. doi:10.1136/thoraxjnl-2020-214744.Crossref | PubMed | ISI | Google Scholar5. Hickling KG, Henderson SJ, Jackson R. Low mortality associated with low volume pressure limited ventilation with permissive hypercapnia in severe adult respiratory distress syndrome. Intensive Care Med 16: 372–377, 1990. doi:10.1007/BF01735174.Crossref | PubMed | ISI | Google ScholarREFERENCES1. Haouzi P. Revisiting the effects of the reciprocal function between alveolar ventilation and CO2 partial pressure (PaCO2) on PaCO2 homeostasis at rest and in exercise. J Appl Physiol (1985). doi:10.1152/japplphysiol.00058.2022. Link | Google Scholar2. Giosa L, Busana M, Bonifazi M, Romitti F, Vassalli F, Pasticci I, Macri MM, D’Albo R, Collino F, Gatta A, Palumbo MM, Herrmann P, Moerer O, Iapichino G, Meissner K, Quintel M, Gattinoni L. Mobilizing carbon dioxide stores. An experimental study. Am J Respir Crit Care Med 203: 318–327, 2021. doi:10.1164/rccm.202005-1687OC. Crossref | PubMed | ISI | Google Scholar3. Cherniack NS, Longobardo GS. Oxygen and carbon dioxide gas stores of the body. Physiol Rev 50: 196–243, 1970. doi:10.1152/physrev.1970.50.2.196.Link | ISI | Google Scholar4. Pisani L, Nava S, Desiderio E, Polverino M, Tonetti T, Ranieri VM. Extracorporeal CO 2 removal (ECCO 2 R) in patients with stable COPD with chronic hypercapnia: a proof-of-concept study. Thorax 75: 897–900, 2020. doi:10.1136/thoraxjnl-2020-214744.Crossref | PubMed | ISI | Google Scholar5. Hickling KG, Henderson SJ, Jackson R. Low mortality associated with low volume pressure limited ventilation with permissive hypercapnia in severe adult respiratory distress syndrome. Intensive Care Med 16: 372–377, 1990. doi:10.1007/BF01735174.Crossref | PubMed | ISI | Google Scholar Download PDF Previous Back to Top Next FiguresReferencesRelatedInformation Related ArticlesRevisiting the effects of the reciprocal function between alveolar ventilation and CO2 partial pressure (PACO2) on PACO2 homeostasis at rest and in exercise 04 Oct 2022Journal of Applied PhysiologyLast Word on Viewpoint: Revisiting the effects of the reciprocal function between alveolar ventilation and CO2 partial pressure (PACO2) on PACO2 homeostasis at rest and in exercise 04 Oct 2022Journal of Applied PhysiologyCited ByLast Word on Viewpoint: Revisiting the effects of the reciprocal function between alveolar ventilation and CO2 partial pressure (PACO2) on PACO2 homeostasis at rest and in exercisePhilippe Haouzi4 October 2022 | Journal of Applied Physiology, Vol. 133, No. 4 More from this issue > Volume 133Issue 4October 2022Pages 917-917 Crossmark Copyright & PermissionsCopyright © 2022 the American Physiological Society.https://doi.org/10.1152/japplphysiol.00468.2022PubMed36194684History Published online 4 October 2022 Published in print 1 October 2022 Metrics