Early utilization of extracorporeal CO₂ removal for treatment of acute respiratory distress syndrome due to smoke inhalation and burns in sheep

Introduction: In thermally injured patients, inhalation injury is often associated with acute respiratory distress syndrome (ARDS), and is an independent predictor of increased morbidity and mortality. Extracorporeal CO₂ removal (ECCO₂R) therapy offers new possibilities in protective mechanical ventilation in ARDS patients.We performed an early application of ECCO₂R in mild-To-moderate ARDS in sheep ventilated in BiPAP mode. Our aim was to investigate its effect on severity of the lung injury. Material and Methods: Non-pregnant farm-bred ewes (n=15) were anesthetized and injured by a combination of wood-bark smoke inhalation and a 40% total body surface area full-Thickness burn, and were observed for 72 h or death. The animals were randomized to a Hemolung group (n=7) or a Control group (n=8) at time of ARDS onset. ECCO₂R was performed in the Hemolung group after onset of ARDS. Histopathology, CTscans, systemic and pulmonary variables, and CO₂ removal were examined. Results: Early application of ECCO₂R therapy with Hemolung in spontaneously breathing sheep decreased PaCO₂ significantly, while the device removed about 70mL of CO₂ per minute. This did not result in lower minute ventilation in the Hemolung group. Lungpathology and CTscans did not show a difference between groups. Conclusion: In an ovine model of ARDS due to smoke inhalation and burn injury, early institution of ECCO₂R in spontaneously breathing animals was effective in removing CO₂ and in reducing PaCO₂. However, it had no effect on reducing the severity of lung injury or mortality. Further studies are necessary to detail the interaction between extracorporeal CO2 removal and pulmonary physiology.