Extracorporeal membrane oxygenation (ECMO) can cause blood water loss due to insensible perspiration via oxygenators and plasma leakage. The accurate quantification of water loss is crucial for maintaining fluid balance in patients on ECMO. Although several studies have experimentally investigated water loss in ECMO, the factors influencing this loss and the methods for measuring plasma leakage-related water loss remain uninvestigated.

In this study, we incorporated a fluid replacement set into a closed circuit and examined the effects of circulating fluid temperature, oxygenator pressure, and gas flow rate on insensible water loss via an oxygenator. Furthermore, we measured water loss due to plasma leakage by circulating pure water and a solution with a lower surface tension than that of healthy human plasma in the same circuit.

Our findings revealed that insensible water loss from the oxygenator was significantly influenced by the circulating fluid temperature and gas flow rate, but was not affected by the oxygenator pressure. Additionally, the difference in water loss between pure water and the low-surface-tension solution accurately represented the water loss due to plasma leakage.

Water loss from the oxygenator depends on the temperature and gas flow, and plasma leakage can be quantified by accounting for the insensible loss in a closed-loop system.