Complete respiratory support with AVCO2R and CPAP-mimic ventilation for total gas exchange in sheep

The altered respiratory mechanics in patients with chronic obstructive pulmonary disease (COPD) present unique challenges with regard to treatment during an acute exacerbation that often leads to respiratory support with mechanical ventilation. Alternative therapies are badly needed to reduce morbidity and mortality associated with mechanical ventilator use. We hypothesized that arteriovenous carbon dioxide removal (AVCO2R) coupled with continuous positive airway pressure (CPAP) would achieve total gas exchange eliminating the need for intubation/mechanical ventilation, thus reducing baro/volutrauma. This hypothesis was tested in six adult sedated apneic sheep with AVCO2R administered through a simple arteriovenous (AV) shunt for CO2 removal. Because it is impractical to apply a CPAP mask to conscious sheep, the CPAP was mimicked in intubated/sedated sheep by positive end-expiratory pressure (PEEP) of 5-10 mmH2O with negligible ventilation. The AVCO2R and CPAP-mimic maintained Pao2 and Paco2 in the normal physiological ranges. The CO2 removal was 120-150 ml/min through AVCO2R with AV blood flow of 1.1-1.5 L/min. A high fraction of inspired oxygen percentage (Fio2) level (89 ± 3%) was required to achieve 40 ± 7% O2 in the small bronchus. Thus, AVCO2R and CPAP-mimic achieved total gas exchange in anesthetized sheep and may be a potential option for acute COPD exacerbation in humans.