Brown R H, Croisille P, Mudge B, Diemer F B, Permutt S, Togias A
Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins Medical Institutions, Baltimore, Maryland, USA.
Am J Respir Crit Care Med. 2000 Apr;161(4 Pt 1):1256-63. doi: 10.1164/ajrccm.161.4.9806051.
Normal subjects prevented from taking a deep breath show changes in airflow similar to those of asthmatics when challenged with methacholine (MCh). To confirm airway narrowing by MCh in this setting and to determine its location, we concurrently measured changes in airway lumenal area using high resolution computed tomography (HRCT) and airflow using partial spirometry in five normal subjects challenged with increasing doses of MCh under prohibition of deep breaths. In an attempt to improve imaging accuracy, we corrected for the changes in lung volume during bronchoprovocation. At every step of the provocation, scanning was performed at approximately the same lung volume. On the HRCT images, airway area decreased in response to the increasing doses of MCh to 91 +/- 2%, 88 +/- 2%, and 80 +/- 2% of baseline at the doses of MCh 0.25, 0.75, and 2.5 mg/ml, respectively (p < 0.001). Airway narrowing showed no predilection for particular airway sizes and occurred in a heterogeneous pattern. The changes in the mean airway lumenal area as measured by HRCT and the mean partial spirometric outcomes were highly correlated: FEV(1)p (r(2) = 0.46, p = 0.001), FVCp (r(2) = 0.20, p = 0.05), FEV(1)/FVCp (r(2) = 0.55, p = 0.002), MMEFp (r(2) = 0.31, p = 0.01), and taup (r(2) = 0.51, p = 0.0004). We conclude that in normal subjects who are prevented from taking a deep breath, the spirometric changes occurring with aerosol MCh challenge are associated with conducting airway narrowing.
正常受试者在被阻止深呼吸时，用乙酰甲胆碱（MCh）激发后会出现与哮喘患者类似的气流变化。为了证实这种情况下MCh引起的气道狭窄并确定其位置，我们在5名正常受试者被禁止深呼吸的情况下，使用高分辨率计算机断层扫描（HRCT）同时测量气道管腔面积的变化，并使用部分肺活量测定法测量气流变化，这些受试者接受递增剂量的MCh激发。为了提高成像准确性，我们对支气管激发过程中肺容积的变化进行了校正。在激发的每个步骤，扫描均在大致相同的肺容积下进行。在HRCT图像上，随着MCh剂量增加，气道面积分别降至基线的91±2%、88±2%和80±2%，MCh剂量分别为0.25、0.75和2.5mg/ml（p<0.001）。气道狭窄对特定气道大小无偏好，且呈异质性分布。HRCT测量的平均气道管腔面积变化与平均部分肺活量测定结果高度相关：第1秒用力呼气容积百分比（FEV(1)p，r(2)=0.46，p=0.001）、用力肺活量百分比（FVCp，r(2)=0.20，p=0.05）、FEV(1)/FVC百分比（FEV(1)/FVCp，r(2)=0.55，p=0.002）、最大呼气中期流速百分比（MMEFp，r(2)=0.31，p=0.01）和呼气时间常数百分比（taup，r(2)=0.51，p=0.0004）。我们得出结论，在被阻止深呼吸的正常受试者中，雾化MCh激发时发生的肺活量测定变化与传导气道狭窄有关。
