Measurement of systemic oxygen consumption in patients during extracorporeal membrane oxygenation — description of a new method and the first clinical observations

Background: Extracorporeal membrane oxygenation (ECMO) provides temporary life-saving support for patients with severe cardiac failure, but is associated with significant morbidity and mortality. While ECMO enables oxygen delivery (DO 2 ), little is known about oxygen consumption (VO 2 ), largely due to technical difficulties. We aimed to introduce the adaptation of respiratory mass spectrometry to measure VO 2 in patients during ECMO and to use this unique model to determine the pathological dependency of VO 2 on DO 2 in humans. Methods and Patients: Respiratory mass spectrometry remains the ‘state-of-the-art’ method, allowing the highly sensitive and rapid measurement of VO 2 in critically ill patients. The principle and design of the respiratory mass spectrometer are described, together with the setting up of this machine with the ECMO oxygenator and the native lungs of the patients. In two patients with severe dilated cardiomyopathy and little cardiac contraction, the decrease in pump flow and, hence, DO 2 by 20% was associated with a decrease in VO 2 by 5% and 8%, respectively, whereas the increase in pump flow was not associated with any significant change in VO 2 . Conclusions: The direct measurement of VO 2 by respiratory mass spectrometry in ECMO patients provides a unique technique for clinical research on the metabolism and VO 2 -DO 2 relationship in this special group of critically ill patients. Our pilot study is the first to demonstrate a pathological dependency of VO 2 on DO 2 in humans. Further studies are warranted with this technique to examine the changes and the factors affecting systemic oxygen transport in patients during ECMO.