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.