Contribution of Impedance Measurement of the Respiratory System to Bronchial Challenge Tests

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Abstract
The contribution of impedance measurement of the respiratory system to bronchial challenge tests was studied in 64 asthmatics and 23 control subjects. After histamine challenge, resistance values increased significantly at all frequencies but most markedly at the lower frequencies in the asthmatic group; reactance values significantly decreased at all frequencies. In the control group, resistance significantly increased at 8 and 12 Hz. However, reactance decreased significantly at all frequencies. By multiple logistic model analysis, a simple discriminant score was found with great discriminating power to differentiate asthmatics and nonasthmatics. The discriminating score equals 9 .times. FEV1aft - 7 .times. FEV1bef. Adding the forced oscillation technique to the equipment for measuring the bronchial response after challenging procedures can give information about the localization of the response to the challenge in the respiratory system.