Single breath assessment of bronchial responsiveness: a comparison with the astograph method

Bronchial responsiveness to inhaled doubling concentrations of acetylcholine using the astograph and single breath techniques was assessed in 7 males and 11 females (mean age 22.7, SD = 2.05 and 21.2, SD = 1.11 years for male and female respectively) healthy volunteers. Eleven (61%) of the subjects had neither a history of allergy nor wheezes. Five (28%) had allergic rhinitis and two (11%) had asthma. Seven (64%) of the normal subjects, all asthmatic and subjects with allergic rhinitis responded to inhaled acetylcholine. Respiratory conductance (Grs) and the one second forced expired volume (FEV1) expressed as percentages of the baseline values were compared on a semilogarithmic scale against cumulative dose. In most subjects the pattern of the curves showed close similarities in the two methods. The bronchial sensitivity i. e. minimum cumulative dose of acetylcholine just sufficient to start a fall in the FEV1 and Grs (CminS and CminA respectively), showed good correlation (r = 0.750, P less than 0.01). The results indicate that bronchial responsiveness can be reliably assessed using the simple single breath method as well as the more complex astograph method.