Extracorporeal pumpless interventional lung assist in clinical practice: determinants of efficacy

¹ Dept of Internal Medicine II
² Dept of Cardiothoracic Surgery
³ Dept of Anesthesiology
⁴ Dept of Internal Medicine I, University Hospital of Regensburg, Germany

^* To whom correspondence should be addressed. E-mail: thomas.mueller{at}klinik.uni-regensburg.de.

	Abstract

Respiratory acidosis can become a serious problem during protective ventilation of severe lung failure. A pumpless arterio-venous interventional lung assist (iLA) for extracorporeal carbon dioxide removal has been used increasingly to control critical respiratory situations. The present study sought to evaluate the factors determining the efficacy of iLA and calculate its contribution to gas exchange.

In a cohort of 96 patients with severe ARDS, hemodynamic parameters, oxygen consumption and carbon dioxide production as well as gastransfer through the iLA were analysed.

Our measurements demonstrated a significant dependency of blood flow via the iLA – device on cannula size (1.59 +/- 0.52 l·min^-1 for 15 Fr, 1.94 +/- 0.35 l·min^-1 for 17 Fr, and 2.22 +/- 0.45 l·min^-1 for 19 Fr, p<0.001) and on mean arterial pressure. The oxygen transfer capacity averaged 41.7 +/- 20.8 ml·min^-1, carbon dioxide removal was 148.0 +/- 63.4 ml·min^-1. Within two hours of iLA treatment, PaO₂/FiO₂ increased significantly and a fast improvement of PaCO₂ and pH was observed.

Interventional lung assist eliminates approximately 50 percent of calculated total carbon dioxide production with rapid normalisation of respiratory acidosis. Despite limited contribution to oxygen transfer it may allow a more protective ventilation in severe respiratory failure.