Pumpless extracorporeal CO 2 removal restores normocapnia and is associated with less regional perfusion in experimental acute lung injury

Background Lung protective ventilation may lead to hypoventilation with subsequent hypercapnic acidosis ( HA ). If HA cannot be tolerated or occurs despite increasing respiratory rate or buffering, extracorporeal CO 2 ‐removal using a percutaneous extracorporeal lung assist (p ECLA ) is an option. We hypothesised that compensation of HA using p ECLA impairs regional perfusion. To test this hypothesis we determined organ blood flows in a lung‐injury model with combined hypercapnic and metabolic acidosis. Methods After induction of lung injury using hydrochloric acid ( HCl ) aspiration and metabolic acidosis by intravenous HCl infusion in nine pigs, an arterial‐venous p ECLA device was inserted. In randomised order, four treatments were tested: p ECLA shunt (1) with and (2) without HA , and clamped p ECLA shunt (3) with and (4) without HA . Regional blood flows were measured with the coloured microsphere technique. Results HA resulted in higher perfusion in adrenal glands, spleen and parts of splanchnic area ( P  < 0.05) compared with normocapnia. During CO 2 ‐removal with p ECLA , regional perfusion decreased to levels comparable with those without p ECLA and normocapnia. Cardiac output ( CO ) increased during HA without a p ECLA shunt and was highest during HA with a p ECLA shunt compared with normocapnia. During CO 2 ‐removal with p ECLA , this variable decreased but stayed higher than during normocapnia with clamped p ECLA shunt ( P  < 0.05). Conclusion In our lung‐injury model, HA was associated with increased systemic and regional blood flow in several organs. p ECLA provides effective CO 2 removal, requiring a higher CO for perfusion of the p ECLA device without improvement of regional organ perfusion.