Fig. 9.

The classification of severe, moderate, and mild is made on the level of ventilation required to induce a positive response. For example, ≥10% fall in FEV₁. The response is severe if a positive response is obtained at 30% maximum voluntary ventilation (MVV), moderate if it is positive at 60% MVV, and mild if it is positive at 90% MVV. A fall in FEV₁ greater than 30% whatever the ventilation would be regarded as severe. This plot can be used for a multistage or single-stage test. Maximum voluntary ventilation can be calculated on the predicted or actual FEV₁ with MVV=35×FEV₁. By relating the ventilation to a common predicted value, values between subjects can be compared. This also allows the intensity of exercise inducing the response to be estimated. Reproduced with permission from (2).