Percutaneous extracorporeal arteriovenous carbon dioxide removal improves survival in respiratory distress syndrome: A prospective randomized outcomes study in adult sheep

Objective: Arteriovenous carbon dioxide removal (AVCO2R) uses a simple arteriovenous shunt for CO2 removal to minimize barotrauma/volutrauma from mechanical ventilation. We performed a prospective randomized outcomes study of AVCO2R in our new, clinically relevant model of respiratory distress syndrome. Methods: Adult sheep (n = 18) received an LD50 severe smoke inhalation and 40% third-degree burn. When respiratory distress syndrome developed (PaO2/FIO2 < 200 at 40 to 48 hours), animals were randomized to the AVCO2R (n = 9) or sham group (n = 9) for 7 days. Ventilator management protocols mandated reductions in minute ventilation, first tidal volume to peak inspiratory pressure less than 30 cm H2O, then respiratory rate when PaCO2 was less than 40 mm Hg. PaO2 was kept above 60 mm Hg by adjusting FIO2. When FIO2 was 0.21, animals were weaned. Results: The study required 2946 animal-hours of critical care with 696 AVCO2R hours. One died in each group during model development. AVCO2R flow from 820 mL/min to 970 mL/min (11% to 14% cardiac output) removed CO2 at a rate of 92 to 116 mL/min (mean 103 mL/min; 93%-97% of CO2 production). Heart rate, mean arterial pressure, cardiac output, and pulmonary arterial wedge pressure remained relatively constant. Within 48 hours, AVCO2R allowed significant ventilator reductions versus baseline in the following measurements: tidal volume (420 to 270 mL), peak inspiratory pressure (25 to 14 cm H2O), minute ventilation (13 to 5 L/min), respiratory rate (26 to 16 breaths/min), and FIO2 (0.88 to 0.35). Ventilator-free days with AVCO2R were 3.9 versus 0.2 (P