Abstract
In an attempt to evaluate the effect of deep inspiration (DI) on maximum expiratory flow (Vmax), spirogram and partial and maximum expiratory flow-volume curve were analyzed and 3Hz respiratoty impedance (Zrs) was measured before and after inhalation of ipratropium bromide (Sch 1000) in 10 normal subjects and 10 patients with bronchial asthma.
In normal subjects, Vmax after DI (MEF25) was significantly greater than the value obtained after tidal inspiration (PEF25). In contrast, DI caused no consistent change in Vmax in asthmatic patients. After inhalation of Sch 1000, Vmax after DI became lower than that after tidal inspiration in both normal and asthmatic subjects.
When the effect of Sch 1000 was assessed by percentile increase of various respiratory parameters after drug inhalation, the improvement of DI-involved indices, such as FVC, FEV1.0, MEFmax, MeF50 and MEF25, was greater in asthmatic patients than in normal controls, However the improvement of DI-independent values, such as PEF25 and Zrs, showed no significant difference between the two groups.
These findings indicate that: 1) vagal nerve-mediated basal brochomotor tone exists in normal controls as well as in asthmatic patients; 2) although the increased vagal tone is a feature of bronchial sathma, its contribution to the effect of DI is not uniform among the patients; 3) in airway reversibility tests with Sch 1000 inhalation, asthmatic patients can be differentiated from normal controls by DI-involved indices, especially FEV1.0
