LUNG-VOLUME MEASUREMENTS IMMEDIATELY AFTER EXTUBATION BY PREDICTION OF EXTUBATION FAILURE IN PREMATURE-INFANTS

To test the hypothesis that premature infants in whom extubation fails in the first 10 days of life have low volume lungs, functional residu al capacity (FRC) was measured in the first hour after extubation. Onc e extubated, infants received the appropriate level of inspired oxygen necessary to maintain acceptable arterial oxygen saturation. After hu midification, oxygen was bled into a headbox, and FRC was assessed usi ng a helium gas dilution technique and a specially designed infant cir cuit. The results were related to extubation failure, which was diagno sed when the infant required nasal continuous positive airway pressure or re-intubation and ventilation within 48 hours. The latter two form s of respiratory support were instituted by the clinical team, wheneve r the infant developed recurrent or severe apnea or respiratory acidos is. Infants were eligible for entry into the study when born premature ly and extubated within the first 10 days of life. Twenty infants init ially ventilated for respiratory distress syndrome at a median gestati onal age of 29 weeks (range, 26-36 weeks) were studied at a median pos tnatal age of 3 days (range, 1-7 days). All were receiving theophyllin e. Extubation failed in seven infants, who did not differ significantl y from the rest of the cohort regarding gestational age, birthweight, postnatal age, or inspired oxygen concentration (F1O2) at extubation, but their maximum F1O2 during ventilation was higher than in those inf ants who did not require reintubation (P < 0.05). In the infants who f ailed extubation, the median FRC was 19 ml/kg (range, 12-27 ml/kg), wh ich was lower than that of the infants in whom extubation was successf ully accomplished (median, 28 ml/kg; range, 19-37 ml/kg; P< 0.01). An FRC of less than 26 ml/kg had a sensitivity of 71% and specificity of 77% in predicting extubation failure. These results support the hypoth esis that a very low lung volume relates to extubation failure in the first 10 days of life. (C) 1996 Wiley-Liss, Inc.