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

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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.

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