Extracorporeal CO 2 Removal in a Lung Lavage Induced Respiratory Distress Syndrome

Abstract

Ten pigs with experimental respiratory distress syndrome were treated by extracorporeal CO₂ removal (ECCO₂-R) combined with low frequency positive pressure ventilation (LPPV). After lung damage had been induced by repeated lung lavages a PEEP trial was conducted in order to find the appropriate PEEP for the damaged lungs. This PEEP was then applied during the ECCO₂-R/LPPV period. Blood gas values improved significantly on extracorporeal bypass within a short time (pre-bypass paO₂: 54.2 ± 3.7 vs 168.5 ± 31.6 mmHg after 15 min on bypass, p < 0.001) and were kept constant during the next 4 hours. Minute ventilation (MV) was reduced from 4.01 ± 0.31 to 0.74 ± 0.07 l/min (p < 0.0001), FiO₂ of the ventilator from 1.0 to 0.46 ± 0.08 (p < 0.0001) whereas FiO₂ of the membrane lung (ML) was not changed significantly (FIO_2ML 0.59 ± 0.07 vs 0.53 ± 0.06). During controlled mechanical ventilation (CMV), comparable adequate gas exchange was only achieved at a significantly higher mean airway pressure ( $P\overline{aw}14.1\pm 0.08$ vs 21.2 ± 0.47 cmH20, p < 0.0001). Hemodynamic variables did not change significantly during bypass time. ECCO₂-R/LPPV driven by a simple renal perfusion system allows adequate gas exchange in experimental respiratory failure.