PERCENTILE CURVES OF FUNCTIONAL RESIDUAL CAPACITY IN NEWBORN-INFANTS

Background: Helium dilution or nitrogen washout techniques are commonl y used to measure the functional residual capacity (FRC) in newborn ba bies. For both techniques equipment is available. Its clinical applica tion, however, was difficult since there were no FRC reference ranges for the different weight groups of newborn infants; reference studies are very time consuming and cause several technical and ethical proble ms. Methods: Statistical methods were used to evaluate several results from the literature and to exclude significantly differing data of so me authors. Measured values of FRC were related to body weight, and th e percentiles of FRC/kg were estimated by the smoothed cumulative dist ribution function of the pooled data. Results: No significant differen ces were found between the results of helium dilution and nitrogen was hout techniques. The distribution of 178 results showed a significant skewedness (x5% = 18.3 ml/kg; x50% = 27.5 ml/kg x95% = 42.8 ml/kg), wh ich could also be seen in the percentile curves calculated approximate ly, assuming a linear development of functional residual capacity with body weight. Conclusion: Percentile curves describe best the developm ent and interindividual variability of FRC in newborn babies as our ev aluation could show. We conclude that the nonparametric estimation of percentiles is more adequate for the description than the use of simpl e regression models.