Comparison of refractoriness after exercise- and hyperventilation-induced asthma.

To study the relationship of bronchoconstriction and refractoriness we performed pairs of exercise and hyperventilation tests in 15 patients (mean [SEM] age 28.5 [2.8] years) with a history of exercise-induced asthma. Mean (SEM) maximum specific airway resistance (SRaw) increased during the first exercise test to 33.9 (4.5) and during the second exercise test to 29.8 (5.2) cmH2O x s (n.s.). Mean (SEM) maximum specific airway resistance (SRaw) increased during the first hyperventilation test to 44.0 (5.9) and during the second hyperventilation test to 27.4 (3.3) cmH2O x s (p less than 0.01). Mean maximum bronchoconstriction after corresponding exercise and hyperventilation tests did not differ statistically. There was a significantly larger inter-individual variability in the airway response to hyperventilation (p less than 0.001). From these data we suggest that similar refractoriness can be observed after both exercise and hyperventilation.