脉冲振荡肺功能支气管舒张试验阳性标准的确定

Determination of positive bronchodilating response using impulse oscillation system in children

目的探讨在使用脉冲振荡肺功能(IOS)检测时,如何判断支气管舒张试验阳性。方法随机抽取发作期哮喘患儿156例,均进行最大呼气流量-容积和IOS测定,然后进行支气管舒张试验。以第一秒用力呼气容积(FEV1)和最大呼气中段流量(MMEF)作为金标准,分别计算IOS主要参数,即呼吸总阻抗(Zrs)、气道总粘性阻力(R5)、电抗(X5)在不同改善率水平时其对诊断的敏感度与特异度,并计算两种肺功能主要参数间的回归方程。结果吸入支气管舒张剂后,患儿肺功能显著改善,两种肺功能主要参数的改善率均存在显著相关(P<0.01),其中X5改善率与最大呼气流量-容积曲线参数改善率相关性最强(相关系数分别为0.676、0.571),Zrs次之。无论使用FEV1改善率≥15%,还是使用MMEF改善率≥30%作参照,IOS参数以Zrs、R5下降≥20%,X5下降≥30%作为舒张试验阳性有着较高的敏感度和特异度。回归方程结果显示,与FEV1改善15%、MMEF改善30%对应的Zrs、R5、X5的降低率分别为21.7%、21.3%;19.9%、19.5%;30.1%、29.6%。结论用IOS进行支气管舒张试验,只有在Zrs、R5下降≥20%,X5下降≥30%时,才能考虑作为试验阳性。

Objective Impulse oscillation system （IOS） as an approach to lung function determination is suitable for children, especially for preschool children in that it only requires the individual to be examined to breathing stably with tidal volume. However, until now there have been no uniformly agreed criteria for positive bronchial reversibility test in clinical practice. A screening method was applied to seek for answer when this question in the hope of providing objective evidence for clinical diagnosis of respiratory diseases, esp. asthma. Methods One hundred and fifty-six children patients during asthma attack were recruited randomly for this study from January to December, 2004. These patients included 103 boys and 53 girls aged from 5 to 18 years with mean age of 8. 84 ±2. 58 years, who visited the doctors in the Clinical and Educational Centre for Asthma, Capital Institute of Pediatrics and were diagnosed as asthma. Maximal expiratory flow volume and IOS lung function were determined followed by bronchodilator reversibility test in all patients. The sensitivity and specificity of IOS parameters, total respiratory impedance （Zrs）, respiratory resistance at 5 Hz （R S） and reactance at 5 Hz （X5） for diagnosing asthma at different improvement levels after inhalation of bronchodilator were calculated respectively using forced expiratory volume in first second （FEV1 ） and maximal mid-expiratory flow （MMEF） as gold standard. And the regression equation between parameters of lung function which were determined with the two different methods was analyzed. Results After inhalation of bronchodilator, the lung function of the children was improved significantly （P 〈0. 01 ） , with the FEV1, MMEF increase and Zrs, RS, and X5 decrease. There were significantly positive correlations （ P 〈 0. 01 ） between the improvement rate of parameters of lung functions determined with the two methods, and the highest correlation coefficients existed between X5 and FEVl and MMEF （respectively 0. 676, 0. 571 ）, correlation coefficients between X5 and Zrs ranked second （0. 519 and 0. 505, respectively）. When an increase of FEV1 equal to or greater than 15% , or increase of MMEF equal to or greater than 30% was used as reference for positive bronchial reversibility, the sensitivity and specificity were relatively high for considering positive bronchial reversibility test with at least 20% decrease of Zrs, RS, and 30% decrease of X5 with IOS lung function. The sensitivity and specificity of Zrs, R5 and X5 calculated from FEV1 were 0. 62, 0. 51 ; 0.49, 0. 54 ; 0. 70, and 0. 54, respectively. The sensitivity and specificity of Zrs, R5 and X5 calculated from MMEF were 0. 63, 0. 54 ; 0. 53, 0. 60 ; 0. 60, and 0. 58, respectively. The regression equation showed that the decrease of Zrs, R5 and X5 corresponding to 15% increase of FEV1 and 30% increase of MMEF were 21.7%, 21.3% ; 19.9%, 19. 5% ;30. 1% , and 29. 6%, respectively. Condusion When lung function is determined with lOS in children, only when decrease of Zrs and R5 is equal to or more than 20% and decrease of X5 is 30% or more after inhalation of bronchodilator, can the bronchial reversibility test be considered as positive.