Department of Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia. falkassimi @ yahoo.com
Respiration. 2011;82(1):19-27. doi: 10.1159/000323075. Epub 2011 Jan 29.
Irreversible airways obstruction in smokers is usually attributed to chronic obstructive pulmonary disease (COPD). We speculate that some of these are cases of asthma indistinguishable from COPD.
To determine the prevalence of asthma in a 'COPD' population and how to differentiate the two conditions.
This was a prospective observational study of smokers fulfilling the Global Initiative for Chronic Obstructive Lung Disease definition of COPD [mean post-salbutamol forced expiratory volume in 1 s (FEV1) 66.9% predicted]. They were classified into 4 groups, as follows: (1) inhaled corticosteroid (ICS)-responsive asthma, defined by normalization of spirometry upon ICS treatment; (2) irreversible asthma, defined as airway obstruction for 1 year and bronchial biopsy indicating asthma; (3) COPD, in the presence of bilateral panlobular emphysema with bullae on high-resolution computed tomography, hypercapneic respiratory failure or bronchial biopsy indicating COPD, and (4) unclassified airflow limitation (AFL).
Eighty patients fulfilled the definition of COPD. The initial diagnosis was COPD in 57.5% and asthma in 42.5%. The final diagnosis was ICS-responsive asthma in 48 patients (60%), irreversible asthma in 8 (10%), COPD in 16 (20%) and unclassified AFL in 8 (10%). A normal transfer coefficient for carbon monoxide (KCO) and an FEV1 fluctuation ≥18% during 1 year of follow-up distinguished irreversible asthma and COPD. Seven of the 8 patients with irreversible asthma had improved FEV1 at the end of 1 year (median 320 ml compared with -29 ml in COPD). Five out of the 8 unclassified AFL cases had normal KCO and a large improvement in FEV(1) suggestive of irreversible asthma.
COPD, even in heavy smokers, includes cases of asthma. FEV1 fluctuation during 1 year is a novel concept which may distinguish irreversible asthma and COPD.
吸烟者不可逆的气道阻塞通常归因于慢性阻塞性肺疾病（COPD）。我们推测，其中一些是与 COPD 难以区分的哮喘病例。
确定“COPD”人群中哮喘的患病率以及如何区分这两种疾病。
这是一项对符合全球慢性阻塞性肺疾病倡议（COPD）定义的吸烟者进行的前瞻性观察性研究[沙丁胺醇后 1 秒用力呼气量（FEV1）平均预测值 66.9%]。他们分为 4 组，如下所示：（1）吸入皮质类固醇（ICS）反应性哮喘，定义为 ICS 治疗后肺功能正常化；（2）不可逆性哮喘，定义为气道阻塞 1 年，支气管活检提示哮喘；（3）COPD，存在双侧全小叶肺气肿和高分辨率计算机断层扫描上的大疱、高碳酸血症性呼吸衰竭或支气管活检提示 COPD，以及（4）未分类的气流受限（AFL）。
80 例患者符合 COPD 定义。初始诊断为 COPD 的占 57.5%，哮喘的占 42.5%。最终诊断为 ICS 反应性哮喘 48 例（60%），不可逆性哮喘 8 例（10%），COPD 16 例（20%），未分类 AFL 8 例（10%）。一氧化碳转移系数（KCO）正常和 1 年内 FEV1 波动≥18%可区分不可逆性哮喘和 COPD。8 例不可逆性哮喘中有 7 例在 1 年结束时 FEV1 得到改善（中位数为 320ml，而 COPD 为-29ml）。8 例未分类 AFL 中有 5 例 KCO 正常，FEV1 明显改善提示不可逆性哮喘。
即使在重度吸烟者中，COPD 也包括哮喘病例。1 年内 FEV1 波动是一个新概念，可能区分不可逆性哮喘和 COPD。
