• Pedro Vitale Mendes, Marcelo Park, Alexandre Toledo Maciel, Débora Prudêncio E Silva, Natalia Friedrich, Edzangela Vasconcelos Santos Barbosa, Adriana Sayuri Hirota, Guilherme Pinto Paula Schettino, Luciano Cesar Pontes Azevedo, and Eduardo Leite Vieira Costa.
• Research and Education Institute, Hospital Sírio-Libanês, São Paulo, Brazil. p.mendes@hc.fm.usp.br.
• Intensive Care Med Exp. 2016 Dec 1;4(1):1.

BackgroundExtracorporeal membrane oxygenation (ECMO) is a technique widely used worldwide to improve gas exchange. Changes in ECMO settings affect both oxygen and carbon dioxide. The impact on oxygenation can be followed closely by continuous pulse oximeter. Conversely, carbon dioxide equilibrates much slower and is not usually monitored directly.MethodsWe investigated the time to stabilization of arterial carbon dioxide partial pressure (PaCO2) following step changes in ECMO settings in 5 apnoeic porcine models under veno-venous ECMO support with polymethylpentene membranes. We collected sequential arterial blood gases at a pre-specified interval of 50 min using a sequence of standardized blood and sweep gas flow combinations.ResultsFollowing the changes in ECMO parameters, the kinetics of carbon dioxide was dependent on sweep gas and ECMO blood flow. With a blood flow of 1500 mL/min, PaCO2 takes longer than 50 min to equilibrate following the changes in sweep gas flow. Furthermore, the sweep gas flow from 3.0 to 10.0 L/min did not significantly affect PaCO2. However, with a blood flow of 3500 mL/min, 50 min was enough for PaCO2 to reach the equilibrium and every increment of sweep gas flow (up to 10.0 L/min) resulted in additional reductions of PaCO2.ConclusionsFifty minutes was enough to reach the equilibrium of PaCO2 after ECMO initiation or after changes in blood and sweep gas flow with an ECMO blood flow of 3500 ml/min. Longer periods may be necessary with lower ECMO blood flows.

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