Respiratory acidosis can become a serious problem during protective ventilation of severe lung failure. A pumpless arteriovenous 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
acute respiratory distress syndrome, haemodynamic parameters, oxygen consumption and
carbon dioxide production as well as gas transfer through the iLA were analysed. The measurements demonstrated a significant dependency of blood flow via the iLA device on
cannula size (mean+/-sd 1.59+/-0.52 L x min(-1) for 15 French (Fr), 1.94+/-0.35 L x min(-1) for 17 Fr, and 2.22 +/-0.45 L x min(-1) for 19 Fr) and on mean arterial pressure.
Oxygen transfer capacity averaged 41.7+/-20.8 mL x min(-1),
carbon dioxide removal was 148.0+/-63.4 mL x min(-1). Within two hours of iLA treatment, arterial
oxygen partial pressure/inspired
oxygen fraction ratio increased significantly and a fast improvement in arterial
carbon dioxide partial pressure and pH was observed. Interventional lung assist eliminates approximately 50% 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.