Kinetics of the recovery of airway response caused by inhaled histamine.

The time course of recovery from airway response induced by the inhalation of progressively doubling doses of histamine phosphate (3 to 4 depending on the subject) was studied in 8 asthmatic subjects by serial measurements of lung resistance (RL). For every subject, the time required for functional recovery became longer with increasing histamine doses and/or degrees of airway response. The slopes of the curves obtained from a single exponential fit relating time on the abscissa and functional recovery on the ordinate were significantly (F = 4.9 to 50.0, p less than 0.01) and progressively lower in 7 of 8 instances. This suggested a multiple compartment model, which was confirmed (r2 greater than or equal to 0.95) in 5 subjects by applying a double exponential regression that provided the most satisfactory fit. We conclude that the recovery from airway response caused by inhaled histamine is longer with increasing doses of histamine and/or degrees of airway response. A double-compartment model, a fast one followed by a slow one, fit this pattern of recovery in 5 of the 8 subjects.