| Abstract | Post-extubation chest radiographs (CXRs) are frequently requested on the neonatal
intensive care unit, but it is controversial whether they generate useful information. A low
lung volume assessed by measurement of functional residual capacity (FRC) post extubation
has been demonstrated to predict extubation failure, which is a subsequent requirement for
increased respiratory support. We have previously shown that the CXR lung area obtained
by computer assisted analysis significantly correlated with FRC and, therefore, speculated
that a low CXR lung area post extubation would reliably predict extubation failure. The aim
of this study was to test the hypothesis by analysing CXRs from 20 infants, with median
gestational age of 28 weeks (range 25-33 weeks) and postnatal age 4 days (range 1-11
days). CXRs were obtained within 4 h of extubation and were scanned and analysed using a
Power Macintosh computer with a Wacom A5 Ultra pad and NIH image software. The
cardiac, mediastinal and thymic shadows, and areas of perihilar and lobar consolidation were
subtracted from the thoracic area to give the lung area. Seven infants failed extubation and
differed significantly from the rest of the cohort only with regard to their CXR lung area,
median gestational age, birth weight and postnatal age. Receiver operator characteristic
(ROC) curves were constructed and the areas under each ROC curve were compared.
Analysis demonstrated that a low CXR lung area and an older postnatal age were the best
predictors of extubation failure. A post-extubation CXR lung area of < 8.5 cm2 had the
highest specificity (100%) in predicting extubation failure. We conclude that routine
post-extubation CXRs can have a useful role. |