A novel and portable extracorporeal CO₂-removal device was evaluated to provide additional gas transfer, auxiliary to standard therapy in severe acute hypercapnic respiratory failure. A dual-lumen catheter was inserted percutaneously in five subjects (mean age 55±0.4 years) and, subsequently, connected to the CO₂-removal device. The median duration on support was 45 hours (interquartile range 26-156), with a blood flow rate of approximately 500 mL/min. The mean PaCO₂ decreased from 95.8±21.9 mmHg to 63.9±19.6 mmHg with the pH improving from 7.11±0.1 to 7.26±0.1 in the initial 4 hours of support. Three subjects were directly weaned from the CO₂-removal device and mechanical ventilation, one subject was converted to ECMO and one subject died following withdrawal of support. No systemic bleeding or device complications were observed. Low-flow CO₂ removal adjuvant to standard therapy was effective in steadily removing CO₂, limiting the progression of acidosis in subjects with severe acute hypercapnic respiratory failure.