Publication
Key Role of Respiratory Quotient to Reduce the Occurrence of Hypoxemia During Extracorporeal Gas Exchange: A Theoretical Analysis*
Publisher:
Ovid Technologies (Wolters Kluwer Health)
Date:
07-10-2020
DOI:
10.1097/CCM.0000000000004619
Abstract: Extracorporeal respiratory support, including low blood flow systems providing mainly extracorporeal CO 2 removal, are increasingly applied in clinical practice. Gas exchange physiology during extracorporeal respiratory support is complex and differs between full extracorporeal membrane oxygenation and extracorporeal CO 2 removal. Aim of the present article is to review pathophysiological aspects which are relevant for the understanding of hypoxemia development during extracorporeal CO 2 removal. We will describe the mathematical and physiologic background underlying changes in respiratory quotient and alveolar oxygen tension during venovenous extracorporeal gas exchange and highlight the clinical implications. Theoretical analysis of venovenous extracorporeal gas exchange. Italian university research hospital. None. None. While the effect of extracorporeal CO 2 removal on the respiratory quotient of the native lung has long been known, the role of extracorporeal oxygenation in dictating changes in the respiratory quotient has been less addressed. Indeed, both extracorporeal CO 2 removal and extracorporeal oxygen delivery affect the respiratory quotient of the native lung and thus influence the alveolar P o 2 . Indeed, for the same amount of extracorporeal CO 2 extraction, it is possible to reduce the F io 2 , reduce the risk of absorption atelectasis, and maintain the same alveolar P o 2 , by increasing the extracorporeal oxygen delivery. Worsening of hypoxemia is frequent during low-flow extracorporeal CO 2 removal combined with ultraprotective mechanical ventilation. In this context, increasing extracorporeal oxygen delivery, increases the respiratory quotient of the native lung and could reduce both the occurrence of alveolar hypoxia and absorption atelectasis, thus optimizing the residual lung function.