Non invasive direct writing recorder of Larynageal, central and peripheral airway hypersensitivity.

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We examined the dose-response curves to methacholine in 6 normal subjects and 13 asthmatics by simultaneous assessment of respiratory resistance (Rrs) and anatomic dead space (Vdan). Methacholine was continuously inhaled in stepwise inctemented concentrations furing tidal breathing until a nearly twofoldincrease in respitatory resistance (Rrs) was observed. Largeairway response was determined by Voan,and overall airway response was determined by Rrs. Small air-ways response was inferred from Rrs when the decrease Vdan was slight. Respiratory resistance was measured with the 5-Hz oscillation technique, and the Dan was measured by langley's method (14) With CO_2 ad the testgas, andboth were recorded simultaneously breath by breath. Im the normal subject Vdan decreased by 28 (+-)7%7Mean (+-)SD) and Rrs increased simultaneously by 100%, suggesting a large airways responder. Five asthmatics were large large airway responders in a manner similar to that of the notmal subjects, but in 8 asthmatics, Vdan decresed by 100% orless,whereas Rrs increased by 100%,suggesting that the increase in Rrs was due to an increase in small sirways resistance(small airways responder). In the asthmatic subjects, small airways responders showed more hypersensitivity than did large airways responders (P<0.01). These results suggest thet the site of airway response is one of the determining factors in bronchial hypersensitibity