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 Landser 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 H2O.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 H2O.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 H2O.s2/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 H2O.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.