Impact of sweep gas flow on extracorporeal CO2 removal (ECCO2R)

Stephan Strassmann; Michaela Merten; Simone Schäfer; Jonas de Moll; Daniel Brodie; Anders Larsson; Wolfram Windisch; Christian Karagiannidis

doi:10.1186/s40635-019-0244-3

Impact of sweep gas flow on extracorporeal CO₂ removal (ECCO₂R)

Intensive Care Med Exp. 2019 Mar 25;7(1):17. doi: 10.1186/s40635-019-0244-3.

Authors

Stephan Strassmann¹, Michaela Merten¹, Simone Schäfer¹, Jonas de Moll¹, Daniel Brodie², Anders Larsson³, Wolfram Windisch¹, Christian Karagiannidis⁴

Affiliations

¹ Department of Pneumology and Critical Care Medicine, Cologne-Merheim Hospital, ARDS and ECMO Centre, Kliniken der Stadt Köln gGmbH, Witten/Herdecke University Hospital, Ostmerheimer Strasse 200, D-51109, Cologne, Germany.
² Division of Pulmonary, Allergy and Critical Care, Columbia University College of Physicians and Surgeons/New York-Presbyterian Hospital, New York, NY, USA.
³ Hedenstierna Laboratory, Anesthesiology and Intensive Care, Department of Surgical Sciences, Uppsala University, Uppsala, Sweden.
⁴ Department of Pneumology and Critical Care Medicine, Cologne-Merheim Hospital, ARDS and ECMO Centre, Kliniken der Stadt Köln gGmbH, Witten/Herdecke University Hospital, Ostmerheimer Strasse 200, D-51109, Cologne, Germany. Christian.Karagiannidis@uni-wh.de.

Abstract

Background: Veno-venous extracorporeal carbon dioxide (CO₂) removal (vv-ECCO₂R) is increasingly being used in the setting of acute respiratory failure. Blood flow rates range in clinical practice from 200 mL/min to more than 1500 mL/min, and sweep gas flow rates range from less than 1 to more than 10 L/min. The present porcine model study was aimed at determining the impact of varying sweep gas flow rates on CO₂ removal under different blood flow conditions and membrane lung surface areas.

Methods: Two different membrane lungs, with surface areas of 0.4 and 0.8m², were used in nine pigs with experimentally-induced hypercapnia. During each experiment, the blood flow was increased stepwise from 300 to 900 mL/min, with further increases up to 1800 mL/min with the larger membrane lung in steps of 300 mL/min. Sweep gas was titrated under each condition from 2 to 8 L/min in steps of 2 L/min. Extracorporeal CO₂ elimination was normalized to a PaCO₂ of 45 mmHg before the membrane lung.

Results: Reversal of hypercapnia was only feasible when blood flow rates above 900 mL/min were used with a membrane lung surface area of at least 0.8m². The membrane lung with a surface of 0.4m² allowed a maximum normalized CO₂ elimination rate of 41 ± 6 mL/min with 8 L/min sweep gas flow and 900 mL blood flow/min. The increase in sweep gas flow from 2 to 8 L/min increased normalized CO₂ elimination from 35 ± 5 to 41 ± 6 with 900 mL blood flow/min, whereas with lower blood flow rates, any increase was less effective, levelling out at 4 L sweep gas flow/min. The membrane lung with a surface area of 0.8m² allowed a maximum normalized CO₂ elimination rate of 101 ± 12 mL/min with increasing influence of sweep gas flow. The delta of normalized CO₂ elimination increased from 4 ± 2 to 26 ± 7 mL/min with blood flow rates being increased from 300 to 1800 mL/min, respectively.

Conclusions: The influence of sweep gas flow on the CO₂ removal capacity of ECCO₂R systems depends predominantly on blood flow rate and membrane lung surface area. In this model, considerable CO₂ removal occurred only with the larger membrane lung surface of 0.8m² and when blood flow rates of ≥ 900 mL/min were used.

Keywords: ARDS; COPD; ECCO2R; ECMO; Extracorporeal carbon dioxide removal.