Patterns of intrathoracic gas volume and airway resistance in children with asthma.

Airway resistance (Raw) decreases with an increase of lung volume (ITGV) during body-growth. In asthmatic subjects, an increase of Raw may be modified by hyperinflation. In this study thirty five asthmatic children underwent histamine challenges with the monitoring of changes of Raw and ITGV. Control measurements (after withhold of spasmolytic medication) showed increased values of ITGV and Raw with high interindividual variability. Histamine challenge resulted in a further increase of both ITGV and Raw in 18 patients (normal pattern). Twelve patients showed an increase predominantly of Raw (obstructive pattern), 5 patients an increase predominantly of ITGV (hyperinflatory pattern). On provocation and after bronchospasmolysis, all subjects presented the expected inverse relation between ITGV and Raw. The variability of ITGV-Raw patterns in children with asthma may agree with the concomitantly established role for vagal reflex mechanisms in prolonged inspiratory diaphragmatic innervation during experimentally induced bronchoconstriction in animals. In children with asthma the ITGV-Raw pattern may point to different risk profiles.