Effect of Hematocrit on the CO2 Removal Rate of Artificial Lungs

Extracorporeal CO2 removal (ECCO2R) can permit lung protective or noninvasive ventilation strategies in patients with chronic obstructive pulmonary disease (COPD) and acute respiratory distress syndrome (ARDS). With evidence supporting ECCO2R growing, investigating factors which affect CO2 removal is necessary. Multiple factors are known to affect the CO2 removal rate (vCO2) which can complicate the interpretation of changes in vCO2; however, the effect of hematocrit on the vCO2 of artificial lungs has not been investigated. This in vitro study evaluates the relationship between hematocrit level and vCO2 within an ECCO2R device. In vitro gas transfer was measured in bovine blood in accordance with the ISO 7199 standard. Plasma and saline were used to hemodilute the blood to hematocrits between 33% and 8%. The vCO2 significantly decreased as the blood was hemodiluted with saline and plasma by 42% and 32%, respectively, between a hematocrit of 33% and 8%. The hemodilution method did not significantly affect the vCO2. In conclusion, the hematocrit level significantly affects vCO2 and should be taken into account when interpreting changes in the vCO2 of an ECCO2R device.