Pumpless arterio-venous extracorporeal lung assist compared with veno-venous extracorporeal membrane oxygenation during experimental lung injury.

BACKGROUND: Extracorporeal lung support is effective to prevent hypoxaemia and excessive hypercapnia with respiratory acidosis in acute respiratory distress syndrome. Miniaturized veno-venous extracorporeal membrane oxygenation (mECMO) and arterio-venous pumpless extracorporeal lung assist (pECLA) were compared for respiratory and haemodynamic response and extracorporeal gas exchange and device characteristics.

METHODS: After induction of acute lung injury by repeated lung lavage, 16 anaesthetized and mechanically ventilated pigs were randomized to mECMO (Medos Hilite/Deltastream) or pECLA (iLA Novalung) for 24 h.

RESULTS: Improved gas exchange allowed reduced ventilation and plateau pressure in both groups. An arterio-venous shunt flow of up to 30% of cardiac output resulted in a left cardiac work of 6.8 (2.0) kg m for pECLA compared with 5.0 (1.4) kg m for mECMO after 24 h (P<0.05). Both devices provided adequate oxygen delivery to organs. The oxygen transfer of pECLA was lower than mECMO due to inflow of arterial oxygenated blood [16 (5) compared with 64 (28) ml min(-1) after 24 h, P<0.05]. Unexpectedly, the carbon dioxide transfer rate was also lower [58 (28) compared with 111 (42) ml min(-1) after 24 h, P<0.05], probably caused by a Haldane effect preventing higher transfer rates in combination with lower extracorporeal blood flow.

CONCLUSIONS: Both devices have the potential to unload the lungs from gas transfer sufficiently to facilitate lung-protective ventilation. Although technically less complex, oxygen uptake and carbon dioxide removal are limited in pECLA, and cardiac work was increased. mECMO overcomes these limitations and might provide better cardiopulmonary protection.