Inhalative provocation test. When is it positive?

A range for the airway resistance (R), reference resistance (Rref), quotient (R/Rref) measured by whole body plethysmography is given for unspecific inhalative provocation in asthmatic patients. 1. In patients with an initial R/Rref value less than 2 (R about 0,6 kPa/l/s) the non allergic reaction did not exceed an R/Rref quotient of 2,7. 2. Those patients with an initial R/Rref quotient greater than 2 but less than 5 reached an R/Rref value of 8.5 after non allergic provocation, which equals an R of about 1,75 kPa/l/s. It is recommended to provoke only those patients in whom the initial R/Rref quotient is in the beginning smaller than 2; because it is otherwise difficult to separate allergic from non allergic reactions and the necessary allergen induced bronchospasm might be harmful. Reference values for specific airway resistance have the advantage that we do not need a panting manouvre against a closed shutter which is often difficult to achieve especially with children during an asthmatic attack.