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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 CO2-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 CO2-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 CO2-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 CO2 removal, requiring a higher CO for perfusion of the p ECLA device without improvement of regional organ perfusion. [ABSTRACT FROM AUTHOR]