Signs of Gas Trapping in Normal Lung Density Regions in Smokers

Abstract

Subthreshold gas trapping representing mild small airway disease is prevalent in normal-appearing lung regions in smokers without airflow obstruction, and it is associated with respiratory morbidity. Clinical trial registered with www.clinicaltrials.gov (NCT00608764).

Respiratory symptoms and small airway dysfunction in current and former smokers without spirometric COPD

“…Half the subjects had an abnormal MDNW or IOS measurement, and in one quarter there was an overlap in abnormal IOS and MBNW variables. The results of the study and those from previous studies using physiological tests and CT imaging biomarkers demonstrate that small airway dysfunction is commonly found in this group of current and former smokers. Interestingly, smokers without spirometric COPD following smoking cessation show sustained improvements of conductive airway dysfunction (S cond ), but not in acinar airway function (S acin ) suggesting that some abnormalities of small airway disease are reversible, possibly due to reduced inflammation or hypersecretion …”

“…The function of peripheral airways is abnormal in some smokers without COPD assessed by physiological techniques, such as multiple breath nitrogen washout (MBNW) and impulse oscillometry (IOS) . Analysis of expiratory and inspiratory computed tomography (CT) images detects increased nonemphysematous air trapping, a surrogate for functional small airways disease, in ever‐smokers with normal spirometry . However, little is known about whether small airway dysfunction assessed by physiological tests, such as MBNW or IOS are worse in symptomatic smokers without COPD compared to asymptomatic smokers.…”

“…8,9 Analysis of expiratory and inspiratory computed tomography (CT) images detects increased nonemphysematous air trapping, a surrogate for functional small airways disease, in ever-smokers with normal spirometry. [10][11][12] However, little is known about whether small airway dysfunction assessed by physiological tests, such as MBNW or IOS are worse in symptomatic smokers without COPD compared to asymptomatic smokers. In this issue of Respirology, Jetmalani et al 13 report the results of a prospective, observational study designed to determine the prevalence of respiratory symptoms (chronic bronchitis, dyspnoea, wheeze) and small airway dysfunction and their interrelationship in eighty young to middle-aged current and former smokers without spirometric COPD.…”

“…Nevertheless, the difference in abnormalities between symptomatic and asymptomatic subjects was relatively small. Previous studies in older smokers with normal spirometry have reported that CT air trapping is associated with worse clinical outcomes 12 and lung function decline, 10 whereas CT airway wall thickness is associated with symptoms of chronic bronchitis. 1 Although important, the study by Jetmalani et al 13 has some limitations.…”

Lung volumes identify an at-risk group in persons with prolonged secondhand tobacco smoke exposure but without overt airflow obstruction

“…Our findings are consistent with another recent report about the association of gas trapping on CT imaging and respiratory symptoms in a cohort of smokers without spirometric COPD. 41 …”