LUNG-FUNCTION BY TIDAL BREATHING IN AWAKE HEALTHY NEWBORN-INFANTS

The increasing availability of appliances for measuring lung function in infants may allow clinical and epidemiological applications. The ai m of the present study was to establish reference values for tidal bre athing lung function in awake newborn infants and to investigate poten tial sources of variability. Tidal flow-volume loops were measured in 803 awake, healthy infants (427 males and 376 females) and passive res piratory mechanics (single-breath occlusion technique) in 664. Mean po stnatal age was 2.7+/-0.9 (SD) days, gestational age 39.8 +/-1.4 weeks I and birthweight 3.59+/-0.49 kg. Tidal expiratory volume (VT), peak tidal expiratory flow (PEF), and mid-expiratory flow increased signifi cantly with increasing birthweight. Flow ratios: ratio of time to PEF to total expiratory time (TPEF/TE), ratio of volume to PEF to total ex piratory volume (VPEF/VE); and ratio of tidal flow at 252 remaining ex piration to PEF (TEF(25)/PEF), were highest in 1 day old infants (medi ans 0.39, 0.46 and 0.81 respectively), decreasing to a minimum in 4-5 day old infants, but were not influenced by birthweight. Tidal flows a nd flow ratios were higher in males versus females, even after weight adjustment, Respiratory rates correlated significantly with tidal flow s (r=0.66), inversely with VT (r=-0.40), but not with flow ratios. Mea n compliance of the respiratory system was 1.18 ml.cmH(2)O(-1).kg birt hweight (95% confidence interval (95% CI) 1.15-1.21) and mean resistan ce 0.051 cmH(2)O.ml(-1).s (95% CI 0.049-0.054). These results demonstr ate that lung function in awake healthy infants varies according to we ight, gender and postnatal age. The present data may serve as a basis for reference values to be used in cross-sectional and prospective stu dies.