Recovery of FEV1 after histamine challenge in asthmatic children

Factors that influence the time necessary for complete recovery of FEV₁ after inhaling histamine were analysed in forty-five children with asthma. These included the initial bronchial obstruction (baseline FEV₁), the provocation dose of histamine producing a 20% fall in FEV₁ (PD₂₀) and the fall in FEV₁ after the histamine challenge. In addition it was also investigated whether a second challenge carried out after complete recovery of FEV₁ would produce a reproducible PD₂₀-histamine value. The time for complete recovery varied widely from 15 to more than 75 min. The time needed for complete recovery of FEV₁ after the histamine challenge seems to be mainly determined by the PD₂₀ value. The other factors such as initial bronchial obstruction and the fall in FEV₁ after the challenge showed no significant relationship with the recovery time. A second challenge with histamine resulted in a highly reproducible PD₂₀ value. The clinical implication of this study is that other tests can only be performed when FEV₁ has returned to 95% of baseline.