Wesseling G J, Vanderhoven-Augustin I M, Wouters E F
Department of Pulmonary Diseases, University Hospital Maastricht, The Netherlands.
Thorax. 1993 Mar;48(3):254-9. doi: 10.1136/thx.48.3.254.
Impedance measurements by the forced pseudo random noise oscillation technique can be used to study the mechanical characteristics of the respiratory system. The objective of this study was to analyse the changes in impedance to a cold air provocation test in patients with asthma, and to correlate these changes with those in the forced expiratory volume in one second (FEV1).
The response to isocapnic hyperventilation with cold air was assessed by respiratory impedance measurements and spirometry in 60 patients with bronchial asthma in whom the provocative dose of histamine resulting in a 20% fall in FEV1 (PD20) was < or = 8 mumol.
Cold air provocation resulted in a mean(SD) fall in FEV1 from 3.75(0.85) litres to 3.10(0.90) litres. The mean(SD) decrease in FEV1 as a percentage of predicted was 15.4(3.8)%. The oscillatory resistance at 8 Hz increased from a mean(SD) of 0.367(0.108) kPa/l/s to 0.613(0.213) kPa/l/s and at 28 Hz the resistance increased from 0.348(0.089) to 0.403(0.099) kPa/l/s. Frequency dependence of resistance became significantly more negative. The reactance at 8 Hz decreased from a mean(SD) of -0.035 (0.041) kPa/l/s to -0.234(0.199) kPa/l/s, and the resonant frequency increased from 12.5(4.9) Hz to 25.7(9.1) Hz. Significant correlations were calculated between the decrease in FEV1 and changes in the various impedance parameters, especially between the decrease in FEV1 and the increase in resistance at 8 Hz (r = -0.66), and the decrease in FEV1 and the increase in the resonant frequency (r = -0.63).
Cold air provocation in asthmatic subjects results in changes in the impedance of the respiratory system that correlate well with the changes in FEV1. These changes in impedance reflect ventilatory inhomogeneities in the peripheral compartment of the bronchial tree. These observations show the value of this technique in the evaluation of induced bronchoconstriction, as both a quantitative and a qualitative analysis of the response is possible.
通过强迫伪随机噪声振荡技术进行的阻抗测量可用于研究呼吸系统的力学特性。本研究的目的是分析哮喘患者冷空气激发试验中阻抗的变化，并将这些变化与一秒用力呼气容积（FEV1）的变化相关联。
对60例组胺激发剂量导致FEV1下降20%（PD20）≤8 μmol的支气管哮喘患者，通过呼吸阻抗测量和肺量计评估其对冷空气等碳酸血症过度通气的反应。
冷空气激发导致FEV1均值（标准差）从3.75（0.85）升降至3.10（0.90）升。FEV1下降的均值（标准差）占预测值的百分比为15.4（3.8）%。8 Hz时的振荡阻力从均值（标准差）0.367（0.108）kPa/l/s增加到0.613（0.213）kPa/l/s，28 Hz时阻力从0.348（0.089）增加到0.403（0.099）kPa/l/s。阻力的频率依赖性变得显著更负。8 Hz时的电抗从均值（标准差）-0.035（0.041）kPa/l/s降至-0.234（0.199）kPa/l/s，共振频率从12.5（4.9）Hz增加到25.7（9.1）Hz。计算了FEV1下降与各种阻抗参数变化之间的显著相关性，特别是FEV1下降与8 Hz时阻力增加之间（r = -0.66），以及FEV1下降与共振频率增加之间（r = -0.63）。
哮喘患者的冷空气激发导致呼吸系统阻抗变化，与FEV1变化密切相关。这些阻抗变化反映了支气管树外周部分的通气不均匀性。这些观察结果表明该技术在评估诱发支气管收缩方面的价值，因为对反应进行定量和定性分析都是可能的。
