Abstract Objective In order to investigate pathophysiology of exercise induced asthma (EIA), the impedance of the respiratory system was studied using impulse oscillometry (IOS). EIA is a temporary increase in airwa...Abstract Objective In order to investigate pathophysiology of exercise induced asthma (EIA), the impedance of the respiratory system was studied using impulse oscillometry (IOS). EIA is a temporary increase in airway resistance, which occurs after several minutes of strenuous exercise. Most asthmatics experience EIA. Patients and methods Respiratory impedance was measured with IOS (MasterScreen, Jaeger, Germany) in 14 healthy volunteers and 14 asthmatics as baseline value at first. The procedure of exercise challenge with an ergometer (Corival 300 Gould Co.) increased heart rate to 90% of predicted maximum values in 3-4 min and maintained for 6 min. After challenge, measurements with IOS were made immediately at 5 min intervals for 5 times. Results The maximal increase of respiratory impedance occurred at 5-10 min after exercise and the increment magnitude of peripheral resistance (99.6%) was more than that of central resistance (13.5%) in asthmatics. After challenge, R5Hz, R5Hz-R20Hz, Zrespir (total impedance), resonance frequency (Fres) and X5Hz from patients changed significantly. The increment value of R5Hz-R20Hz from asthmatics was≥0.032kpa/l·s -1 and the change ratio of X5Hz from 71.4% of asthmatics was ≥41% (2SD beyond the mean response of nonashmatics). Air trapping loop was expressed in V T Zrespir graph in 57.1% patients. All subjects underwent IOS measurement. Conclusion Exercise test can diagnose asthma and evaluate efficacy of treatment for bronchial asthma. Because the patients usually have shortness of breath after exercise challenge, the measurement with spirometry (FEV 1) may not be accurate. IOS is based on measurement of the relationship between an external pressure pulse applied to the respiratory system and the resulting respiratory airflow. The spectral ratio of the amplitude of the pressure wave signal to the resulting flow signal constitutes the impedance of the respiratory system, from which the resistance (R) and the reactance (X, including elastance and inertance) of respiratory system in the frequency range 5Hz to 35Hz can be calculated. Our data showed that the increment value of R5Hz-R20Hz was more sensitive than other indices for detecting exercise induced asthma. The bronchoconstriction took place in peripheral airway mainly after exercise. Because obstruction of small bronchi during expiration and impedance increased abruptly, air trapping loops were expressed in V T Zrespir graph after challenge in asthmatics. Fres is the frequency point where the absolute value of elastance equals to that of inertance. X5Hz reflects the condition of compliance of lungs. Fres shifted right and change ratio of X5Hz increased after exercise were relative to the compliance decrease of lungs. The airway response of exercise challenge may be assessed more accurately and more conveniently with IOS that did not require a maximal inspiration and forced expiration.展开更多
文摘Abstract Objective In order to investigate pathophysiology of exercise induced asthma (EIA), the impedance of the respiratory system was studied using impulse oscillometry (IOS). EIA is a temporary increase in airway resistance, which occurs after several minutes of strenuous exercise. Most asthmatics experience EIA. Patients and methods Respiratory impedance was measured with IOS (MasterScreen, Jaeger, Germany) in 14 healthy volunteers and 14 asthmatics as baseline value at first. The procedure of exercise challenge with an ergometer (Corival 300 Gould Co.) increased heart rate to 90% of predicted maximum values in 3-4 min and maintained for 6 min. After challenge, measurements with IOS were made immediately at 5 min intervals for 5 times. Results The maximal increase of respiratory impedance occurred at 5-10 min after exercise and the increment magnitude of peripheral resistance (99.6%) was more than that of central resistance (13.5%) in asthmatics. After challenge, R5Hz, R5Hz-R20Hz, Zrespir (total impedance), resonance frequency (Fres) and X5Hz from patients changed significantly. The increment value of R5Hz-R20Hz from asthmatics was≥0.032kpa/l·s -1 and the change ratio of X5Hz from 71.4% of asthmatics was ≥41% (2SD beyond the mean response of nonashmatics). Air trapping loop was expressed in V T Zrespir graph in 57.1% patients. All subjects underwent IOS measurement. Conclusion Exercise test can diagnose asthma and evaluate efficacy of treatment for bronchial asthma. Because the patients usually have shortness of breath after exercise challenge, the measurement with spirometry (FEV 1) may not be accurate. IOS is based on measurement of the relationship between an external pressure pulse applied to the respiratory system and the resulting respiratory airflow. The spectral ratio of the amplitude of the pressure wave signal to the resulting flow signal constitutes the impedance of the respiratory system, from which the resistance (R) and the reactance (X, including elastance and inertance) of respiratory system in the frequency range 5Hz to 35Hz can be calculated. Our data showed that the increment value of R5Hz-R20Hz was more sensitive than other indices for detecting exercise induced asthma. The bronchoconstriction took place in peripheral airway mainly after exercise. Because obstruction of small bronchi during expiration and impedance increased abruptly, air trapping loops were expressed in V T Zrespir graph after challenge in asthmatics. Fres is the frequency point where the absolute value of elastance equals to that of inertance. X5Hz reflects the condition of compliance of lungs. Fres shifted right and change ratio of X5Hz increased after exercise were relative to the compliance decrease of lungs. The airway response of exercise challenge may be assessed more accurately and more conveniently with IOS that did not require a maximal inspiration and forced expiration.
