Measurement of the non-specific threshold stimulus for the bronchial tree by continuous monitoring of respiratory resistance using the oscillation method.

Bronchial hyperreactivity to various stimuli has been used as one of the diagnostic criteria of chronic obstructive lung diseases. We studied bronchial responsiveness to histamine in 30 patients with acute or chronic bronchitis, 28 patients with bronchial asthma and in 42 more patients with other lung diseases, using a new device--the Astograph--which yielded graphically a continuous dose-response curve of the respiratory resistance by the oscillation method during the inhalation of histamine diphosphate. The results of this method were compared with the results of FEV1 and FEF25-75 before and after the challenge procedure. An increase of the respiratory resistance (Ros) during the challenge test gave an indication of a decrease of FEV1. The increase of Ros and the decrease of FEV1 and FEF25-75 were most pronounced in the asthmatics. Not in all cases was there a correlation between the increase of Ros and the decrease of FEV1, possibly due to imperfections in the design of the equipment. We believe that the Ros measurement cannot be totally exchanged for the conventional method. The use of the Astograph alone cannot be recommended because of the false-negative reactions. A combination Astograph/Floop equipment is rather expensive, but it is the most rational and ideal. The test itself does not induce bronchoconstriction and is simple and time-saving. However, this procedure is not yet advised as a diagnostic tool for a challenge test with allergens in the diagnosis of bronchial asthma. A further investigation on the validity and security of such a provocation is still needed.