EUCAPNIC VOLUNTARY HYPERVENTILATION AS A BRONCHOPROVOCATION TECHNIQUE- A DEVELOPMENT OF A STANDARDIZED DOSING SCHEDULE IN ASTHMATICS

A variety of dosing schedules have been reported for the hyperventilat ion method of bronchoprovocation testing. To evaluate the effect of ch allenge technique on the bronchoconstrictive response, we had 16 subje cts perform eucapnic voluntary hyperventilation (EVH) with dry, room t emperature gas using four different dosing schedules. The hyperventila tion challenge dosages included the following: (1) a target minute ven tilation (V over dot E) of 20 x FEV(1) for 6 min; (2) a target V over dot E of 15 x FEV(1) for 12 min; (3) an interrupted challenge with a t arget V over dot E of 30 x FEV(1) for 2 min repeated 3 times; and (4) a target V over dot E of 30 x FEV(1) for 6 min. Challenges 2, 3, and 4 gave identical absolute ventilatory challenges (identical factor FEV( 1) x minutes) but at different V over dot E dosages or time, Challenge s 1 and 4 were of identical length, but different target V over dot E. The mean postchallenge fall in FEV(1) was 16.6+/-10.9%, 11.0+/-8.1%, 19.6+/-9.9%, and 26.7+/-11.3% for challenges 1, 2, 3, and 4, respectiv ely. The response to an identical EVH challenge (FEV(1) x 30 for 6 min ) was reproducible when performed on separate days. We conclude that t he challenge technique used for hyperventilation testing will have a s ignificant impact on the bronchoconstrictive response and must be take n into account when interpreting study results. Tests may be quantitat ively comparable over a narrow range of challenge time and V over dot E. We recommend that a 6-min uninterrupted EVH challenge using room te mperature gas at a target V over dot E of 30xFEV(1) be adopted as the ''standard'' challenge.