Assessment of forced expiratory volume-time parameters in detecting histamine-induced bronchoconstriction in wheezy infants.

A new technique recently introduced allows the measurement of infant lung function from lung volumes raised by a pump prior to generation of forced expiratory flow-volume (FEFV) curves. Forced expiratory volume-time (FEV1) parameters rather than traditional flow parameters are used. The aim of this study was to assess the usefulness of FEV1 parameters in detecting airway responsiveness to histamine in recurrently wheezy infants. Ten infants (age 7-18 months) sedated with 80 mg/kg chloral hydrate underwent a histamine inhalation challenge. Throughout the challenge FEFV curves were generated from end-tidal inspiration. Raised FEFV curves, from a lung volume preset by 15 cmH2O inflation pressure, were gathered at baseline and after the final concentration of histamine. The mean fall from baseline was 47% in maximal flow at functional residual capacity (VmaxFRC) (P < 0.0005), 15.5% in FEV0.5 (P < 0.0001), 13.5% in FEV0.75 (P < 0.005), and 11.0% in FEV1.0 (P = 0.057), after the final concentration of histamine delivered. Tidal volume and inspiratory volume reached above FRC between pre- and posthistamine did not change. Mean oxygen saturation fell significantly from 97 to 93%. We conclude that FEV1 parameters adequately detect reduced lung function during histamine-induced bronchoconstriction and appear suitable for histamine challenge testing in infants.