Assessment of lung function in neonates during extracorporeal membrane oxygenation

We report our experience with pulmonary function testing in 11 out of 22 full-term neonates with severe respiratory failure, treated at the ECMO center Graz (Austria) during the period from 1990 to 1995. Altogether 17 out of 22 patients survived ECMO and all of them were successfully weaned from ECMO. Pulmonary function was assessed by monitoring expiratory tidal volume on the ventilator and estimating respiratory system compliance from the ratio tidal volume/(PIP-PEEP). In addition, compliance, and functional residual capacity were measured using a computerized pulmonary function system (PEDS). Compliance (mean +/- SD) decreased markedly after 24 hours of ECMO, compared with baseline values (0.20 +/- 0.12 vs 0.12 +/- 0.13 ml/cmH2O/kg) and was significantly higher (0.43 +/- 0.14 ml/cmH2O/kg, p < 0.01) before ECMO stop. When tidal volumes increased continuously ECMO blood flow could be decreased, indicating lung recovery. Most patients had a tidal volume of > 7 ml/kg prior to decannulation. Functional residual capacity and corresponding dynamic compliance, measured in 5 patients, ranged from 18.6 to 29.6 ml/kg and 0.49 to 0.57 ml/cmH2O/kg at this time. Functional residual capacity (mean +/- SD) increased significantly when surfactant was administered to promote weaning from ECMO (8.28 +/- 0.9 vs 19.0 +/- 1.0 ml/kg, p < 0.01). We conclude that the assessment of lung function has improved our understanding of pulmonary recovery during ECMO. Its clinical significance in determining the optimum time of weaning from ECMO needs further evaluation.