Ueda Tetsuya, Niimi Akio, Matsumoto Hisako, Takemura Masaya, Hirai Toyohiro, Yamaguchi Masafumi, Matsuoka Hirofumi, Jinnai Makiko, Muro Shigeo, Chin Kazuo, Mishima Michiaki
Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
J Allergy Clin Immunol. 2006 Nov;118(5):1019-25. doi: 10.1016/j.jaci.2006.07.032. Epub 2006 Sep 12.
Small airways may have an important role in asthma but are more difficult to assess pathologically than central airways. Computed tomographic indices of lung density are assumed to reflect air trapping and may be a useful noninvasive measure of small airways disease, but their pathophysiological relevance remains undetermined.
To evaluate lung density on high-resolution computed tomography and examine its correlations with clinical and physiologic variables in 29 patients with stable asthma.
Both lungs were scanned at full-inspiratory and full-expiratory phases to quantify percentage of lung field occupied by low attenuation area (LAA%; < -960 Hounsfield units) and mean lung density. Asthma severity, pulmonary function, methacholine airway sensitivity and reactivity, and sputum eosinophil counts were evaluated.
The mean lung density increased and LAA% decreased in all patients at expiratory phase compared with inspiratory phase. The inspiratory density indices and expiratory mean lung density correlated only with FEV(1)/forced vital capacity (FVC). Expiratory LAA% correlated more strongly than other variables with FEV(1)/FVC and with indices of peripheral airflow obstruction. Expiratory/inspiratory ratios of LAA% and mean lung density correlated, the former more strongly, with disease severity, residual volume/total lung capacity, and airway sensitivity, as well as with indices of global (FEV(1) and FEV(1)/FVC) and peripheral airflow obstruction.
Expiratory/inspiratory high-resolution computed tomography is useful for assessing small airways disease in asthma. Small airways involvement is associated with airflow obstruction, airway hypersensitivity, and more severe disease.
Small airways are an important therapeutic target in asthma.
小气道在哮喘发病中可能起重要作用，但与中央气道相比，其病理评估更为困难。肺密度的计算机断层扫描指数被认为可反映气体潴留情况，可能是一种有用的小气道疾病无创检测指标，但其病理生理相关性仍未明确。
评估29例稳定期哮喘患者的高分辨率计算机断层扫描肺密度，并探讨其与临床和生理变量的相关性。
在全吸气和全呼气期对双肺进行扫描，以量化低衰减区（LAA%；＜-960亨氏单位）占肺野的百分比及平均肺密度。评估哮喘严重程度、肺功能、乙酰甲胆碱气道敏感性和反应性以及痰液嗜酸性粒细胞计数。
与吸气期相比，所有患者呼气期的平均肺密度增加，LAA%降低。吸气密度指数和呼气平均肺密度仅与第1秒用力呼气容积（FEV₁）/用力肺活量（FVC）相关。呼气LAA%与FEV₁/FVC及外周气流阻塞指数的相关性比其他变量更强。LAA%和平均肺密度的呼气/吸气比值与疾病严重程度、残气量/肺总量和气道敏感性以及整体（FEV₁和FEV₁/FVC）和外周气流阻塞指数相关，前者相关性更强。
呼气/吸气高分辨率计算机断层扫描有助于评估哮喘中的小气道疾病。小气道受累与气流阻塞、气道高敏反应及更严重的疾病相关。
小气道是哮喘重要的治疗靶点。
