MEASUREMENT OF LUNG-VOLUMES AND PULMONARY MECHANICS DURING WEANING OFNEWBORN-INFANTS WITH INTRACTABLE RESPIRATORY-FAILURE FROM EXTRACORPOREAL MEMBRANE-OXYGENATION

Newborn infants with intractable respiratory failure who require extra corporeal membrane oxygenation (ECMO) experience diffuse pulmonary ate lectasis shortly after initiation of ECMO. Atelectasis is likely due t o the primary lung injury and the reduction of applied inspiratory ven tilator pressure when the respirator settings are changed to the ''res t settings.'' These pathophysiologic changes result in a decrease in l ung compliance and lung volumes. We hypothesized that improving lung f unctions observed during ECMO and indicated by an increase in lung vol umes will predict successful weaning from ECMO. Sixteen infants (mean +/- SEM: gestational age, 40.3 +/- 0.3 weeks; birth weight, 3.5 +/- 0. 1 kg) with meconium aspiration syndrome (n = 13), sepsis (n = 2), and persistent pulmonary hypertension (n = 1) were studied. We measured pa ssive respiratory system mechanics and lung volumes initially during f ull ECMO support (115 +/- 18 h on ECMO, Study I), and then within 24 h prior to weaning from ECMO (Study II). Respiratory system compliance (C-rs), respiratory system resistance (R(rs)), functional residual cap acity (FRC), and tidal volume (V-T) were measured. Prior to Study I lu ng volumes were too small to be detected. C-rs increased between Study I and Study II (0.41 +/- 0.05 to 0.63 +/- 0.05 mL/cmH(2)O/kg, P < 0.0 5), and V-T increased between Study I and Study II (5.6 +/- 0.6 to 10. 4 +/- 0.8 mL/kg, P = 0.0005). FRC increased from 3.6 +/- 1.0 to 7.9 +/ - 0.9 mL/kg (P = 0.0001). There was no change in R(rs) (88 +/- 8 to 89 +/- 6 cm H2O/L/s, P = 0.9). The combination of C-rs > 0.5 mL/cmH(2)O/ kg and FRC > 5 mL/kg was a better predictor (P = 0.0002) of readiness to wean from ECMO than either C-rs (>0.5 mL/cmH(2)O/kg, P = 0.057) or FRC (>5 mL/kg, P = 0.007) alone. The combination of FRC and C-rs had a sensitivity of 73.3% and specificity of 100% for successful decannula tion. We conclude that repeated measurements of FRC and C-rs can asses s lung recovery and may assist in establishing criteria for successful weaning from ECMO. (C) 1995 Wiley-Liss, Inc.