Methacholine inhalation challenge. Practical consequences of using duplicate spirograms after each concentration.
Several studies have shown that during bronchial provocation tests with pharmacologic agents, a prior deep inspiration causes transient bronchodilatation in normal subjects and patients with allergic rhinitis. We investigated the influence of using two consecutive spirograms after each methacholine concentration on the results of methacholine inhalation challenge. Methacholine inhalation challenge was performed in 70 nonsmoking subjects (26 with current asthma, 23 asymptomatic asthmatic patients and 21 patients with allergic rhinitis). The aerosols (PBS, followed by twofold increasing concentrations of methacholine from 0.095 to 50 mg/mL) were inhaled by tidal breathing for two minutes; after two minutes of aerosol inhalation, the subject performed two forced vital capacity maneuvers, 30 to 40 seconds apart. Separate dose-response curves were constructed from FEV1 values of the first and second spirogram. The PC20FEV1 (provocative concentration of methacholine required to produce a 20% fall in FEV1) was calculated from the log dose-response curves (first and second spirogram). The PC20 values obtained from the first (PC20-1) and second (PC20-2) spirogram were not significantly different in patients with current asthma, but the PC20-2 values were higher than the PC20-1 values in asymptomatic asthmatic patients (P < .01) as well as in patients with allergic rhinitis (P < .01). On the other hand, the PC20-2 values were one doubling concentration of PC20-1 values in one current asthmatic patient, one asymptomatic asthmatic patient and five patients with allergic rhinitis. We conclude that the choice of the first or second FEV1 obtained after each methacholine concentration significantly modifies the PC20 in asymptomatic asthmatic patients and patients with allergic rhinitis.(ABSTRACT TRUNCATED AT 250 WORDS)
Prieto
L
L
Sección de Alergia y Servicio de Neumología, Hospital Doctor Peset, Valencia, Spain.
Marín
J
J
D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000175:diagnosis / Q000503:physiopathology; D001985:Bronchial Provocation Tests; D004305:Dose-Response Relationship, Drug; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008688:Methacholine Compounds / Q000008:administration & dosage; D008875:Middle Aged; D012130:Respiratory Hypersensitivity / Q000175:diagnosis* / Q000503:physiopathology; D012221:Rhinitis, Allergic, Perennial / Q000175:diagnosis / Q000503:physiopathology; D006255:Rhinitis, Allergic, Seasonal / Q000175:diagnosis / Q000503:physiopathology; D013147:Spirometry
D008688:Methacholine Compounds