Assessment of Respiratory lmpedance During Deep Slow Breathing with lmpulse Oscillometry in Patients with Chronic Obstructive Pulmonary Disease

Objective: To observe the relationship of deep slow respiratory pattern and respiratory impedance(RI) in patients with chronic obstructive pulmonary disease (COPD). Methods: RI under normal respiration and during deep slow respira tion was measured one after the other with impulse oscillometry for 8 patients with COPD and for 9 healthy volunteers as control. Results: When r espiration was changed from normal pattern to the deep slow pattern, the tida l volume increased and respiratory frequency significantly decreased in both gro ups , the total respiratory impedance (Z respir) showed a decreasing trend in COPD group, but with no obvious change in the control group. No chang e in the resonant frequency (fres) was found in both groups, and the respiratory viscous resistance obviously decreased in the COPD group(R5: P =0.0168 ; R20: P =0.0498; R5—R20: P =0.0388),though in the control group it was unchanged. Conclusion: IOS detection could reflect the response he terogeneity of different compartments of respiratory system during tidal breathi ng. During deep slow respiration, the viscous resistance in both central airw ay and peripheral airway was decreased in patients with COPD. RI measurement by impulse oscillometry may be a convenient pathophysiological method for studying the application of breathing exercise in patients with COPD.

The applicable value of respiratory impedance for the stage 0 of chronic obstructive pulmonary disease

Objective ：To evaluate the applicable value of respiratory impedance for the stage 0 of chronic obstructive pulmonary disease （COPD）. Methods：Respiratory impedance was measured by impulse oscillometry （lOS） in 41 cases at stage 0 of COPD （NHLBI/WHO, 2001 Standard） and their conventional pulmonary function values were compared with 42 healthy subjects. Both groups had no significant deviation in age, stature and avoirdupois, etc. Master-Screen pulmonary function test system （Jaeger Co, Germany） were used to determine IOS parameters including viscous resistance of 5Hz, 20 Hz and 35Hz （R5, R20, R35）, reactance of 5Hz, 35 Hz （X3, X35）, resonant frequency （Fres） ,total respiratory impedance （Zrs） and routine pulmonary function values including forced expiratory volume in one second to predicted value （FEV1 % ）, forced expiratory volume in one second to forced vital capacity ratio（ FEV1/ FVC% ）, maximal mid expiratory flow （MMEF%）,V23% and V50%. Results：Both groups had no significant deviation in FEV1%, FEV1/FVC% and X35（P〉0.05）. It was increased significantly in viscous resistance of 5Hz, 20 Hz and 35Hz （R5, R20, R35） in COPD group than that in healthy group （P〈0.01）. So were Fres and Zrs （P〈0.01）. MMEF%,V25%,V50% and reactance of 5Hz （X5） in COPD group were marked lower than that in healthy group （P〈0.01）. The sensitivity of MMEF%, V25%,V50% was higher than others, but its specificity was lower. In parameters of IOS, Fres was the most sensitive index for diagnosis of the small airway function and its specificity was higher than that of MMEF%, V25% ,V50%. Conclusion：In the risk case at the stage 0 of COPD, MMEF%, V25% and V50% could be decreased, but Fres, R5 ,R5-20 could be increased in spite of FEV1% and FEV1/FVC% in normal range.

Clinical experiment of exercise induced asthma and respiratory impedance assessed with impulse oscillometry to measure exercise response of asthmatics

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.