Automatic Control of veno-venous Extracorporeal Lung Assist
Veno-venous extracorporeal lung assist (ECLA) is used to provide sufficient gas exchange even in most severe cases of acute respiratory distress syndrome. Commercially available systems are manually controlled, although an automatically controlled ECLA could enable individualized and continuous adaption to clinical requirements.
Therefore, we developed a demonstrator with an integrated control algorithm to keep continuously measured peripheral oxygen saturation and partial pressure of carbon dioxide constant by automatically adjusting extracorporeal blood and gas flow. The “SmartECLA” system was tested in six animal experiments with increasing pulmonary hypoventilation and hypoxic inspiratory gas mixture to simulate progressive acute respiratory failure.
During a cumulative evaluation time of 32 hours for all animals automatic ECLA control resulted in a peripheral oxygen saturation ? 90 % in 98 % of the time with the lowest value of 82 % for 15 sec. Partial pressure of venous carbon dioxide was between 40 and 49 mmHg in 97 % of the time with no value < 35 mmHg or > 49 mmHg. With decreasing inspiratory oxygen concentration extracorporeal oxygen uptake increased from 68 ± 25 to 154 ± 34 mL·min-1 (p<0.05) and reducing respiratory rate resulted in increasing extracorporeal carbon dioxide elimination from 71 ± 37 to 92 ± 37 mL·min-1 (p<0.05).
The “SmartECLA” demonstrator allowed reliable automatic control of the extracorporeal circuit. Proof of concept could be demonstrated for this novel automatically controlled veno-venous ECLA circuit.