Abstract
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.
Highlights
Extracorporeal membrane oxygenation (ECMO) is a technique widely used worldwide to improve gas exchange
In order to optimize the frequency of changes in ECMO settings, it would be of utmost importance to know how long it takes for carbon dioxide (CO2) to equilibrate after ECMO support initiation or any parameter change
arterial carbon dioxide partial pressure (PaCO2) increased with the reduction of sweep gas flow from 3 to 1.5 L/min; an elevation of sweep gas flow from 1.5 to 10 L/min was associated with a slight fall of PaCO2 to levels similar to those observed with 3 L/min
Summary
Extracorporeal membrane oxygenation (ECMO) is a technique widely used worldwide to improve gas exchange. Changes in ECMO settings affect both oxygen and carbon dioxide. Extracorporeal membrane oxygenation (ECMO) has been successfully used to support severely hypoxemic patients [1,2,3,4,5,6,7]. After initiation of extracorporeal support, blood flow and sweep gas flow are adjusted to achieve target values of arterial oxygen (PaO2), pH, and carbon dioxide (PaCO2) partial pressures. Titrating these ECMO settings can involve multiple steps because, frequently, the initially chosen parameters will not produce the desired result in terms of blood gases, leading to at least one more cycle of parameter change and blood gas analysis. In order to optimize the frequency of changes in ECMO settings, it would be of utmost importance to know how long it takes for CO2 to equilibrate after ECMO support initiation or any parameter change
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