Modulation of airway caliber by deep inhalation in children

To elucidate whether deep inhalation (DI) modulates changes in airway calib er in childhood, we measured the effect of DI on respiratory impedance befo re and after inhaled methacholine or salbutamol in 4- to 7-yr-old children (n = 15) suffering from recurrent wheezing. In all children, the real part of impedance between 12 and 16 Hz (Re[Z]12-16) increased after methacholine from 5.6 +/- 1.2 to 8.2 +/- 1.6 cmH(2)O.l(-1) s (P < 0.001) and resonance frequency from 18 +/- 3 to 25 +/- 5 Hz (P < 0.001). These changes were part ially reversed by DT: Re[Z]12-16 decreased to 7.2 +/- 1.2 cmH(2)O l(-1) s ( P < 0.01) and resonance frequency to 19 +/- 5 Hz (P < 0.001). In nine child ren, on a separate occasion, Re[Z]12-16 decreased after salbutamol. from 8. 3 +/- 1.9 to 5.1 +/- 0.9 cmH(2)O l(-1) s (P < 0.001) and resonance frequenc y from 21 +/- 6 to 15 +/- 3 Hz (P < 0.05). The decrease of Re[Z](12-16) was partially reversed by DI (to 6.2 +/- 1.4 cmH(2)O l(-1) s, P < 0.01), but r esonance frequency did not change significantly (P = 0.75). We conclude tha t in 4- to 7-yr-old children pharmacologically induced changes in airway ca liber are modulated by DI. These findings suggest that airway-to-parenchyma interdependence is operative in this age range.