Bronchial response time to a bronchodilating agent--orciprenaline.

The specific airway conductance (Gaw/Vtg) of 4 normal subjects and 5 subjects with respiratory diseases was measured before and after inhalation of orciprenaline. There was an almost maximum increase in Gaw/Vtg within 3 to 4 minutes in both groups of subjects after inhalation of orciprenaline. From the observed relatively rapid bronchodilatation, it would appear that the increased Gaw/Vtg is produced by the local action rather than the systematic effect of inhaled orciprenaline. Although there are many reports the administration of a bronchodilating agent produces a decrease of airway resistance, the bronchial response time is unknown to get appreciate effect after inhalation of a bronchodilator. The pur pose of this study was to investigate the early response of airway after inhala tion of a bronchodilator. METHODS The whole-body pressure plethysmographic method1,2 was used to measure airway resistance (Raw) and thoracic gas volume (Vtg). Raw was measured during the expiratory phase between zero airflow and 0.5 liter/sec. The resistance of the heated flowmeter-shutter mouth piece assembly (0.25 cmH2O/liter per sec) was subtracted from Raw measurements. The dead-space volume of this assem bly was 55 ml. Volume change was monitered as an integrated airflow tracing. Functional residual capacity (FRG) and Vtg at which Raw was measured were calculated from the volume tracing and the plethysmographic determination of Vtg 3 After five measurements of Raw and Vtg for control, measurements of Raw 41 42 J. Kagawa, S. Katagiri, and M. Tajika and Vtg were made generally every 30 seconds and required 5 seconds of time as described previously,4 after initial inhalation of a bronchodilator. Orciprenaline sulfate ('Alotec'-Boehringer Ingelheim Labs.) was used as a bronchodilator. Orciprenaline is a derivative of the same group as isoproterenol. Table 1 Gaw/Vtg and FRC for before and after inhalation of orciprenaline M=Mean value (1/cm H2O•Esec.) S.D.=Standard Deviation of Gaw/Vtg Bronchial Response Time 43 It was administered by oral inhalation of 2 puffs as aerosol with hand nebulizer. One puff will give approximately 0.75 mg of orciprenaline. All inhalations were made during a deep inspiration, followed by a few seconds breath holding. All data were calculated as specific airway conductance (Gaw/Vtg, where Vtg was the lung volume at which Raw was measured) to allow for possible changes in lung volume during the study.