Evaluation of nasal impedance using the forced oscillation technique in infants

By applying oscillations to the respiratory system through a rigid face mask, the infant‐adapted Lándsér forced oscillation technique measures impedance of the total respiratory system including the nose, at frequencies from 4 to 52 Hz. The present study was aimed at evaluating nasal impedance in infants from consecutive forced oscillation measurements through both nostrils and each nostril separately, using a simple electrical model. In 30 asthmatic infants with varying degrees of nasal obstruction, aged 1–16 months, calculated nasal resistance (R n ) at 24 Hz ranged from 1 to 16 cm H 2 O · L −1 · s. The ratio of R n to total respiratory system resistance varied between 1 and 48% (mean: 16%). In seven non‐asthmatic infants, aged 0‐12 months, R n was between 1 and 11 cm H 2 O · L −1 · s. Nasal patency (evaluated clinically) was correlated with the calculated R n ( P < 0.05). R n showed almost no frequency dependence between 24 and 48 Hz as demonstrated by a mean slope of −0.09 ± 0.08 cm H 2 O · s 2 /L for the asthmatic and of −0.08 ± 0.07 for the non‐asthmatic infants. In seven of the asthmatic infants the differences between two R n determinations at a 45 min interval ranged from −1.7 to 3.8 cm H 2 O · L −1 · s −1 at 24 Hz and from −3.6 to 1.0 at 48 Hz. Changes in R n did not correlate with changes in total respiratory system resistance ( P > 0.05). In conclusion, nasal impedance can be approximated from three consecutive measurements through both nostrils and through each nostril separately.Pediatr Pulmonol. 1991 ; 11 :1‐7.