MOMENT ANALYSIS OF MULTIBREATH NITROGEN WASHOUT IN HEALTHY PRETERM INFANTS

Moment analysis (MA) of multibreath nitrogen washout (MBNW) has not pr eviously been applied to newborn infants. The aim of the present study was to adapt this method to healthy preterm infants using an improved technique suitable for small infants, and to determine reference valu es of MA. Twenty healthy preterm infants with a mean birth weight (+/- SD) of 1,666 +/- 402 g and a mean gestational age of 31.3 +/- 2.1 wee ks were studied during their first 7-28 days of life. Computerized bed side equipment with very low dead space was constructed. The limits of normal variability were determined from results of duplicate studies. Outcome variables included functional residual capacity (FRC), the fi rst-to-zeroth moment ratio (M-1/M-0), the second-to-zeroth moment rati o (M-2/M-0), and the lung clearance index (LCI). The starting point fo r MA had considerable impact on the results. Mean M-1/M-0 and M-2/M-0 were 2.18 +/- 0.18 and 8.71 +/- 1.24, respectively. No significant rel ation between moment ratios and weight, gender or age was found. Intra subject coefficients of variation (CV) for M-1/M-0 (7.9 +/- 5.9%) and for M-2/M-0 (12.1 +/- 9.1%) and intersubject CV for M-1/M-0 (8%) and M -2/M-0 (14%) were similar to those reported in children and adults. Me an lung clearance index was 10.8 +/- 1.4 and intra- and intersubject C Vs were 11.3 +/- 8.9% and 13%, respectively. Mean functional residual capacity (FRC) was 22.5 +/- 2.1 ml/kg. Mean intra- and intersubject CV s for FRC were 8.3% and 9%, respectively. We conclude that the MBNW te st can be performed by a simple bedside method and that MA appears to be a suitable method for measuring gas mixing in preterm infants. (C) 1998 Wiley-Liss. Inc.