NASAL AIRWAY DIMENSIONS AND LUNG-FUNCTION IN AWAKE, HEALTHY NEONATES

Possible relations between nasal airway dimensions and measures of lun g function are not well established. It has been suggested that a majo r part of airway resistance is found in the nose. However, little is k nown about the shape of tidal flow volume (TFV) loops in relation to n asal caliber. We therefore investigated whether lung function assessed by tidal breathing in healthy newborn infants was affected by nasal a irway dimensions. Nasal airway dimensions were measured in 17 healthy newborn babies (mean age, 2.7 days) by acoustic rhinometry before and immediately after lung function measurements. Lung function was evalua ted by TFV loops and passive respiratory mechanics (single-breath occl usion technique), first with both nostrils open, and subsequently imme diately after occlusion of the larger of the two nostrils, causing at least a 50% reduction in nasal minimum cross-sectional area (MCA). Nei ther the TFV expiratory ratios (time and volume to reach peak flow to total time and volume, respectively [t(PTEF)/t(E) and V-PTEF/V-E, resp ectively]), nor resistance or compliance of the total respiratory syst em differed significantly regardless of whether one or both nostrils w ere open. With one nostril closed there were no significant effects on any of the measured lung function parameters. We conclude that in hea lthy awake neonates reducing the cross-sectional area of nasal dimensi ons by 50% does not affect TFV loops or passive respiratory mechanics. (C) 1998 Wiley-Liss, Inc.