Schmekel B, Smith H J
Dept of Clinical Physiology, University Hospital, Linköping, Sweden.
Eur Respir J. 1997 Oct;10(10):2243-9. doi: 10.1183/09031936.97.10102243.
The measurement of forced expiratory volume in one second (FEV1) is often used to assess the effect of bronchial provocations, and deep inspiration is required beforehand. This may briefly alter the bronchial tone in a variable way in some subjects. The forced oscillation technique (FOT) is a test used to characterize the mechanical impedance of the respiratory system, and prior deep inspiration is not required. We tested the hypothesis that measurable bronchoconstriction would occur in all asthmatic subjects stimulated with isocapnic hyperventilation of dry cold air (IHCA). Twenty patients with mild asthma and nine healthy controls were exposed to IHCA, at 70% of their maximal voluntary ventilatory capacity for 4 min and the results were assessed both by applying the FOT and by measuring FEV1. Optimal cut-off levels were defined by receiver operating characteristic (ROC) curve analyses of the changes in respiratory resistance and reactance at 5-35 Hz, resonant frequency (fres) and FEV1. A positive result was present in the asthmatics when measured by FOT, and using ROC analyses the discriminative capacity to correctly diagnose asthma was greatest for responses in fres; the sensitivity was 89% and the specificity 100%. The sensitivity of FEV1 to correctly diagnose asthma was only 73%, and the specificity 88%. In conclusion, the results of this study suggest that the use of forced expiratory volume in one second for bronchial provocation tests by isocapnic hyperventilation of dry cold air may be misleading and that the bronchoconstriction thus elicited is measured with greater sensitivity and specificity by the forced oscillation technique than by forced expiratory volume in one second.
一秒用力呼气量（FEV1）的测量常用于评估支气管激发试验的效果，且事先需要进行深吸气。这可能会在某些受试者中以可变的方式短暂改变支气管张力。强迫振荡技术（FOT）是一种用于表征呼吸系统机械阻抗的测试，无需事先进行深吸气。我们检验了这样一个假设：所有哮喘患者在接受等容性干冷空气过度通气（IHCA）刺激时都会出现可测量的支气管收缩。20例轻度哮喘患者和9名健康对照者接受IHCA，以其最大自主通气量的70%进行4分钟，通过应用FOT和测量FEV1来评估结果。通过对5 - 35Hz呼吸阻力和电抗的变化、共振频率（fres）和FEV1进行受试者操作特征（ROC）曲线分析来定义最佳截断水平。通过FOT测量时，哮喘患者出现阳性结果，使用ROC分析，对哮喘进行正确诊断的判别能力在fres反应中最强；敏感性为89%，特异性为100%。FEV1对哮喘进行正确诊断的敏感性仅为73%，特异性为88%。总之，本研究结果表明，在等容性干冷空气过度通气的支气管激发试验中使用一秒用力呼气量可能会产生误导，并且通过强迫振荡技术比通过一秒用力呼气量能更敏感、更特异地测量由此引发的支气管收缩。
