High-Resolution Computed Tomography Evaluation of Peripheral Airways in Asthma Patients: Comparison of Focal and Diffuse Air Trapping

Abstract

Background: Air trapping evaluated in high-resolution computed tomography (HRCT) reflects changes in small bronchi. We simultaneously evaluated focal and diffuse air trapping in asthmatic patients. Objectives: (1) To evaluate air trapping and bronchial wall thickness in asthmatics. (2) To estimate the relationship between air trapping and bronchial wall thickness, pulmonary function tests (PFTs), age, gender and asthma severity. (3) To compare air trapping between subgroups of asthmatic patients with normal FEV₁ % pred. and FEV₁/FVC % and controls. (4) To compare air trapping and bronchial wall thickness between aspirin-induced asthmatics (AIA) and aspirin-tolerant asthmatics (ATA). Methods: Both groups (asthmatics and controls) included 30 patients. All patients underwent HRCT and PFTs. Results: Focal (p < 0.0001) and diffuse (p = 0.0004) air trappings and bronchial wall thickness (T: p < 0.0001; T/D: p < 0.0001; WA%: p < 0.0001) were significantly greater in asthmatics. Focal and diffuse air trappings were inversely correlated (p = 0.021). Diffuse air trapping correlated with bronchial wall thickness: T/D (p = 0.047), T (p = 0.037), and WA% (p = 0.048). There was a significant difference in the extent of focal air trapping between a subgroup of asthmatics with normal FEV₁ % pred. and FEV₁/FVC % and controls (p < 0.0001). There were no significant differences in focal (p = 0.095) and diffuse air trapping (p = 0.186) and bronchial wall thickness (T: p = 0.086; T/D: p = 0.428; WA%: p = 0.428) between AIA and ATA patients. Conclusions: Both focal and diffuse air trappings provide valuable diagnostic information and therefore deserve to be estimated. The lack of significant differences in air trapping and bronchial wall thickness between AIA and ATA patients needs further investigation.

Airway Remodelling in Asthma and COPD: Findings, Similarities, and Differences Using Quantitative CT

“…Nevertheless, low-density areas are not specific for air trapping since emphysema and local hypoperfusion of lung tissue may have the same effect. Various methods have been reported for air-trapping measurement using CT, from visual grading [41] to manual counting [42]. A Semiautomatic method of quantification has been reported using the density mask technique.…”

“…In asthmatic patients, air-trapping scores correlated with small airway obstruction, assessed by FEV1 and FEF25–75%, which is consistent with small distal airway alterations. Moreover, the focal and diffuse air trapping (E/I ratio) have been shown to correlate with airway wall thickness (WA%) [42]. This should indicate that the remodelling process involves both proximal and distal airways in asthma.…”

In Vivo Computed Tomography as a Research Tool to Investigate Asthma and COPD: Where Do We Stand?

“…In asthma, Mikos et al [24] measured air trapping on CT scans thanks to a manual method, at a window level of −600 HU and a window width of 1600 HU. Focal air trapping was assessed on end-expiratory scans, superimposing a 10 × 10 mm grid.…”

“…Mikos et al using a manual method, showed that focal and diffuse air trapping (E/I ratio) correlated with airway wall thickness (WA%) [24]. Focal air trapping was significantly increased in a subgroup of 10 asthmatics patients with normal FEV1% predicted and FEV1/FVC%.…”

Opportunity to Control Asthma: A Role of Small Airways

“…С помощью КТВР показано, что у больных БА с нормальными значениями показате лей функции внешнего дыхания (ФВД) имеет место неоднородность вентиляции и наличие локальных "воздушных ловушек", что может указывать на не достаточный контроль над воспалением в мелких бронхах при нормальном ОФВ1 [32][33][34].…”