[Studies on airway hyperresponsiveness by the Astograph(r) method in asthmatics and young adult non-asthmatic...

We investigated airway hyperresponsiveness (AHR) by the continuous inhalation method using an Astograph(R) in 105 asthmatics and 141 non-asthmatic asymptomatics. The range of Dmin (1 U=one minute inhalation of 1 mg/ml of methacholine) of asthmatics was 0.001 to 28.70 U, and that of adjusted Dmin of non-asthmatic asymptomatics was 0.28 to 190 U; thus, an apparent overlap was recognized in the distributions of Dmin. Ninety-five percent of asthmatics had a Dmin lower than 7 U, and 95% of non-asthmatic asymptomatics had a Dmin higher than 0.9 U. Presuming that almost all asthmatics had AHR, it was inferred that nearly half of non-asthmatic asymptomatics had AHR, too. Comparison with previous reports suggests that AHR in healthy people may be increasing generally. When Dmin is determined to be>7 U by the Astograph(R) method, it is likely that the patient does not have asthma. When a patient has a Dmin<0.9 U, it is highly probable that the patient has asthma.