Hypercapnia in late-phase ALI/ARDS: Providing spontaneous breathing using pumpless extracorporeal lung assist

Abstract

Objective: The fibroproliferative phase of late ALI/ARDS as described by Hudson and Hough (Clin Chest Med 27:671-677, 2006) is associated with pronounced reductions in pulmonary compliance and an accompanying hypercapnia complicating low tidal volume mechanical ventilation. We report the effects of extracorporeal CO2 removal by means of a novel pumpless extracorporeal lung assist (p-ECLA) on tidal volumes, airway pressures, breathing patterns and sedation management in pneumonia patients during late-phase ARDS. Design: Retrospective analysis. Setting: Fourteen-bed university hospital ICU. Patients: Ten consecutive late-phase ALI/ARDS patients with low pulmonary compliance, and severe hypercapnia. Intervention: Gas exchange, tidal volumes, airway pressures, breathing patterns and sedation requirements before (baseline) and after (2-4 days) initiation of treatment with p-ECLA were analysed. Patients were ventilated in a pressure-controlled mode with PEEP adjusted to pre-defined oxygenation goals. Measurements and main results: Median reduction in pCO2 was 50% following institution of p-ECLA. Extracorporeal CO2 removal enabled significant reduction in tidal volumes (to below 4 ml/kg predicted body weight) and inspiratory plateau pressures [30 (28.5/32.3) cmH2O, median 25, 75% percentiles]. Normalization of pCO2 levels permitted significant reduction in the dosages of analgesics and sedatives. The proportion of assisted spontaneous breathing increased within 24 h of instituting p-ECLA. Conclusion: Elimination of CO2 by p-ECLA therapy allowed reduction of ventilator-induced shear stress through ventilation with tidal volumes below 4 ml/kg predicted body weight in pneumonia patients with severely impaired pulmonary compliance during late-phase ARDS. p-ECLA treatment supported control of breathing pattern while sedation requirements were reduced and facilitated the implementation of assisted spontaneous breathing. © 2009 Springer-Verlag.