Total respiratory impedance in healthy children

Impedance of the total respiratory system was measured in 121 healthy children aged 4–16 years during spontaneous breathing by pseudo‐random forced oscillations between 3 and 10 Hz. Total respiratory resistance (Rrs), inertance (Irs) and compliance (Crs) were determined by least‐mean‐squares fitting. Estimates for inertance were reliable only for the larger children, where the values of Irs (0.0127 ± 0.0034 SD) were similar to those reported for normal adults. Rrs correlated significantly (P < 0.001) with height (r = −0.868), age (r= −0.865), and, in a subpopulation of the 6‐ to 16‐year‐old children, with forced vital capacity (r = −0.803), The corresponding correlation coefficients for Crs were 0.873, 0.844, and 0.853, respectively. Crs amounted to about a third of the static total compliance values of Sharp et al. (J Appl Physiol 1970; 29: 775–779) over the same interval of heights. In these relationships no significant difference was found between boys and girls.