Passive respiratory mechanics measured during natural sleep in healthy term neonates and infants up to 8 weeks of life

The single occlusion technique (SOT) is a simple and noninvasive technique for measurement of passive respiratory mechanics in infants. Reference values based on measurements of a large population of healthy infants performed outside specialized research laboratories are lacking. The aim of this study was to present reference values for passive respiratory mechanics based on a large population of healthy term neonates and infants measured during natural sleep in routine care. As part of the ongoing Wheezing Illnesses Study Leidsche Rijn (WHISTLER), the compliance (C rs ) and resistance (R rs ) of the respiratory system were measured in 450 healthy unsedated neonates and infants with a mean age of 4.6 ± 1.3 weeks. Multivariable regression analysis, with gestational age, age at measurement, body size, sex, and ethnicity as possible predictors, was carried out to estimate prediction equations for mean C rs and R rs values. Technically acceptable lung function measurements could be performed in 328 (73%) neonates and infants. Median C rs was 39.5 (range 14.8–79.1) ml/kPa and median R rs was 7.4 (range 3.8–19.5) kPa/L/sec. The following regression equations for C rs and R rs were obtained: ln C rs  = 1.677 + 1.3 × 10 −4  × birth weight (g) + 0.030 × birth length (cm) and ln R rs  = 2.496–3.1 × 10 −6  × birth length 3 (cm 3 ) − 0.114 × sex. We provided reference values for passive respiratory mechanics using the SOT in a large population of healthy term neonates and infants measured during natural sleep. These data provide a frame of reference for assessing the normality of SOT measurements performed in routine care. Pediatr Pulmonol. 2006, 41:1058–1064. © 2006 Wiley‐Liss, Inc.