Methacholine Bronchoprovocation Tests
Twelve individuals from the stable asthmatic group participated in this phase of the study; six individuals had low MW/FEV, ratios, whereas the other six had normal MW/FEV, ratios. Methacholine was inhaled from a Wright nebulizer during two-min periods of tidal ventilation. Subjects wore a nose clip. Each period of tidal breathing of aerosol was followed immediately by determination of SGaw in the body plethysmograph; FEV, also was measured at 45, 90, and (in some cases) 180 s after each period of inhalation of methacholine. The first aerosol inhaled was the normal saline diluent. Methacholine was then inhaled in doubling concentrations between the ranges of 0.015 to 32 mg/ml or until the challenge was completed. Administration of each dose of methacholine always began 5 min after the initiation of administration of the previous methacholine dose. All oral and inhaled drugs were withheld for a minimum of 12 h prior to challenge with methacholine. The MW/ FEV, ratio as well as SGaw, SGawDI, and SGawMW were measured (as described previously) immediately before each methacholine challenge. my canadian pharmacy
Inhalations were continued until the maximum dose of methacholine was administered or until the FEV, had decreased by more than 25 percent. The noncumulative provocative concentrations (PC) producing 20 and 35 percent decrements in FEV, and SGaw (PC* FEV,; PCMSGaw) were interpolated from the methacholine dose-response curve; these provocative concentrations (PCaoFEV,; PCMSGaw) were considered representative of the sensitivity of the airway. Reactivity of the airways was calculated as the slope of the relationship between noncumulative methacholine dose and SGaw response, beginning with the interpolated concentration causing a 25 percent reduction in SGaw. A minimum of three data points was required for this calculation; this criterion was met by all 12 asthmatic subjects who participated in methacholine testing. We also calculated the slopes of methacholine dose-response curves (defined as change in measured response/geometric mean dose [GMD] of methacholine).