Respiratory Impedance Measured By Impulse Oscillometry In Patients With Bronchial Asthma

Objective: To measure the variation and significance of respiratory impedance and pulmonary ventilation function in patients with bronchial asthma by impulse oscillometry(IOS) before or after the bronchial provocation test, investigate the relationship between the IOS method and bronchial provocation test, and evaluate the clinical significance in bronchial asthma by IOS method. Method: First of all, the basic level in 33 control cases and 44 asthmatic cases was measured, then the bronchial provocation test was performed. After the bronchial provocation test, pulmonary ventilation function and respiratory impedance were monitored. The parameters of pulmonary ventilation function and IOS(MasterScreen, Jaeger, Germany) in control cases were compared with the parameters in asthmatic cases before and after the bronchial provocation test, which were analyzed by correlation. Results: After the bronchial provocation test, various parameters concluding the resonance frequency (Fres), the impedance of the respiratory system (Zrs), the resistance of central airways (Re) and peripheral airways (Rp), the resistance (R) and the reactance (X) calculated in the frequency ranging from 5 to 35 Hz, and parameters such as forced expiratory volume in 1 second (FEV1), the ratio of forced expiratory volume in 1 second to forced vital capacity (FEV1/FVC), et al, got much higher than healthy control group and asthmatic group before test. Resistance curve showed markedly nonlinear decreasing course with increasing frequency, while reactance decreased. The resistance increased and the reactance descended in end-expiration. R and Fres were markedly negative correlated with parameters of pulmonary ventilation function. X and pulmonary ventilation function existed in obvious positive correlation. R showed linear with FEV1%predicted, and the correlation between R5 and FEV1%predicted was the strongest of all. Compared with healthy control group, the IOS indices and MEFV curve of the patients before the bronchial provocation test have not obviously risen. Conclusions: The parameters in IOS test may reflect the patient's physical characteristics of his respiratory system. It is a useful tool in testing the site and extent of airway block sensitively. R5 can be increased by 1.85 times as a positive criterion in bronchial provocation test. The tendency of Fres increase and X5 decrease showed more significant than MEFV curve test in the early stage of the reduction of pulmonarycompliance. There is a good relationship between R, X and FEV1, Vmax in MEFV curve test, which can be used for selecting and evaluating drugs for asthma patients. IOS is a simple and valuable test and only passive co-operation of patients is need, especially in children, the aged and patients with poor pulmonary functions. The normal parameters of IOS according to foreign studies are also useful to our Chinese people. But the establishing normal criterion for our Chinese people IOS test may be more helpful in its clinical application.