The failure of FEVj-specific normal ranges of PD20FEVJ to improve sensitivity or specificity in detecting questionnaire-reported asthma or wheezing has several possible explanations. Measurements of airway responsiveness are imperfect at discriminating between asthmatics and nonasthmatics in population samples,’ and altering the criteria for an abnormal challenge test may have little impact relative to other sources […]
A number of mechanisms have been proposed as the basis for the relationship between nonspecific airway responsiveness and prechallenge pulmonary function.’ Because resistance to flow through a tube is inversely proportional to the radius to the fourth power, a given degree of bronchoconstrictor-induced circumferential airway narrowing can be expected to cause a proportionally larger increase […]
The 547 asymptomatic subjects with normal pulmonary function were grouped according to quintile of prechallenge FEV, (percent predicted), and the fifth percentiles of PD20FEV, within each quintile of FEV, were calculated (Table 2). The fifth percentile of methacholine PD20FEV, increased with increasing quintile of prechallenge FEV,. This relationship is shown graphically in Figure 1, in […]
Between April 1984 and June 1990, 1,410 men reported for at least one examination. Two hundred fifteen subjects were lifetime nonsmokers and denied any history of respiratory illness or symptoms. Regression analysis restricted to these 215 subjects yielded the following equations: Predicted FVC (L) = -4.46 + 0.155 height (in) – 0.0324 age (yrs) Predicted […]
Methacholine inhalation challenge testing was performed as previously described. Solutions were aerosolized by a nebulizer (DeVilbiss 646) powered by an air compressor (DeVilbiss). All inhalations were 6-s vital capacity inhalations followed by 2 s of breathholding. Seconds were counted aloud from a digital stopwatch after careful instruction and practice. Inhalations were done seated and wearing […]
Sample The Normative Aging Study is a longitudinal cohort study of health and aging established at the Veterans Administration’s Outpatient Clinic in Boston in 1963. Volunteers were recruited by advertisement and accepted into the study only if initial health screening revealed no evidence of chronic diseases including asthma, sinusitis, hypertension, or heart disease. The initial […]
Methacholine challenge testing is currently being used as a diagnostic test for a variety of clinical indications. In patients presenting with chronic cough of uncertain cause, challenge testing has been advocated as a means to determine whether the cough is associated with airway hyperresponsiveness (“cough variant asthma”) and likely to respond to bronchodilator therapy. Methacholine […]