Department of Biomedical Engineering, 44 Cummington St., Boston University, Boston, MA 02215, USA.
Respir Res. 2011 Jul 15;12(1):96. doi: 10.1186/1465-9921-12-96.
Asthmatics exhibit reduced airway dilation at maximal inspiration, likely due to structural differences in airway walls and/or functional differences in airway smooth muscle, factors that may also increase airway responsiveness to bronchoconstricting stimuli. The goal of this study was to test the hypothesis that the minimal airway resistance achievable during a maximal inspiration (R(min)) is abnormally elevated in subjects with airway hyperresponsiveness.
The R(min) was measured in 34 nonasthmatic and 35 asthmatic subjects using forced oscillations at 8 Hz. R(min) and spirometric indices were measured before and after bronchodilation (albuterol) and bronchoconstriction (methacholine). A preliminary study of 84 healthy subjects first established height dependence of baseline R(min) values.
Asthmatics had a higher baseline R(min) % predicted than nonasthmatic subjects (134 ± 33 vs. 109 ± 19 % predicted, p = 0.0004). Sensitivity-specificity analysis using receiver operating characteristic curves indicated that baseline R(min) was able to identify subjects with airway hyperresponsiveness (PC20 < 16 mg/mL) better than most spirometric indices (Area under curve = 0.85, 0.78, and 0.87 for R(min) % predicted, FEV1 % predicted, and FEF25-75 % predicted, respectively). Also, 80% of the subjects with baseline R(min) < 100% predicted did not have airway hyperresponsiveness while 100% of subjects with R(min) > 145% predicted had hyperresponsive airways, regardless of clinical classification as asthmatic or nonasthmatic.
These findings suggest that baseline R(min), a measurement that is easier to perform than spirometry, performs as well as or better than standard spirometric indices in distinguishing subjects with airway hyperresponsiveness from those without hyperresponsive airways. The relationship of baseline R(min) to asthma and airway hyperresponsiveness likely reflects a causal relation between conditions that stiffen airway walls and hyperresponsiveness. In conjunction with symptom history, R(min) could provide a clinically useful tool for assessing asthma and monitoring response to treatment.
哮喘患者在最大吸气时表现出气道扩张减少，这可能是由于气道壁的结构差异和/或气道平滑肌的功能差异所致，这些因素也可能增加气道对缩窄刺激的反应性。本研究的目的是检验气道高反应性患者在最大吸气时可达到的最小气道阻力（R(min)）异常升高的假设。
使用 8Hz 强迫振荡技术测量 34 名非哮喘患者和 35 名哮喘患者的 R(min)。在支气管扩张（沙丁胺醇）和支气管收缩（乙酰甲胆碱）前后测量 R(min)和肺量计指标。对 84 名健康受试者的初步研究首先确定了基础 R(min)值的身高依赖性。
哮喘患者的基础 R(min)预测值高于非哮喘患者（134±33%预测值比 109±19%预测值，p=0.0004）。使用受试者工作特征曲线的敏感性特异性分析表明，基础 R(min)比大多数肺量计指标（预测值的 R(min)%、FEV1%和 FEF25-75%的曲线下面积分别为 0.85、0.78 和 0.87）更能识别气道高反应性患者（PC20<16mg/mL）。此外，80%的基础 R(min)<100%预测值的患者没有气道高反应性，而 100%的 R(min)>145%预测值的患者均有气道高反应性，无论临床分类为哮喘还是非哮喘。
这些发现表明，与肺量计相比，更容易进行的基础 R(min)测量在区分气道高反应性患者和非气道高反应性患者方面与标准肺量计指标一样有效或更有效。基础 R(min)与哮喘和气道高反应性的关系可能反映了使气道壁变硬和高反应性的条件之间的因果关系。结合症状史，R(min)可为评估哮喘和监测治疗反应提供一种有用的临床工具。
