Abstract
Rationale – Chronic Obstructive Pulmonary Disease (COPD) is a combination of chronic bronchitis and emphysema, which both may lead to airway obstruction. Under normal circumstances, airway dimensions vary as a function of inspiration level. We aim to study the influence of COPD and emphysema on the airway distensibility, defined as the ratio of relative change in lumen diameter to the relative change in total lung volume (TLV) divided by predicted total lung capacity (pTLC) .
Methods – We included 1900 participants from the Danish Lung Cancer Screening Trial (DLCST); all randomized to annual low-dose CT for a period of 5 years (table 1). Images were reconstructed both with high contrast resolution (3 mm, kernel C) for emphysema analysis and with high spatial resolution (1 mm, kernel D) for airway analysis. Images were analysed by in-house developed software designed to segment lungs and localize the interior and exterior airway wall surface in three dimensions, and branches were matched in consecutive scans by image registration. Emphysema was defined as attenuation <-910 Hounsfield Units (HU), referred to as % low-attenuation area 910 (%LAA910). Emphysema limits were set at <10% (not present), 10-20% (mild), 20%-30% (moderate) or >30% (severe). Spirometry was performed annually and participants were divided into severity groups according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD).
Data were analysed in a mixed effects regression model with log(airway lumen diameter) as outcome and airway generations 0-7, log(TLV) and GOLD status or %LAA910 as explanatory variables including possible interactions.
Results – On average 1.0, 2.0, 3.9, 7.6, 15.2, 25.3, 27.6, and 19.2 airways per subject were included from generation 0-7. Results are shown in figures 1 and 2 for GOLD groups and emphysema, respectively.
Conclusions – Airway distensibility decreases significantly with increasing severity of both GOLD status and emphysema, indicating that in COPD the dynamic change in airway calibre during respiration is compromised. Chronic bronchitis and emphysema appear to be interacting in causing airway narrowing, the latter most likely due to loss of elastic recoil of surrounding tissue.
Methods – We included 1900 participants from the Danish Lung Cancer Screening Trial (DLCST); all randomized to annual low-dose CT for a period of 5 years (table 1). Images were reconstructed both with high contrast resolution (3 mm, kernel C) for emphysema analysis and with high spatial resolution (1 mm, kernel D) for airway analysis. Images were analysed by in-house developed software designed to segment lungs and localize the interior and exterior airway wall surface in three dimensions, and branches were matched in consecutive scans by image registration. Emphysema was defined as attenuation <-910 Hounsfield Units (HU), referred to as % low-attenuation area 910 (%LAA910). Emphysema limits were set at <10% (not present), 10-20% (mild), 20%-30% (moderate) or >30% (severe). Spirometry was performed annually and participants were divided into severity groups according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD).
Data were analysed in a mixed effects regression model with log(airway lumen diameter) as outcome and airway generations 0-7, log(TLV) and GOLD status or %LAA910 as explanatory variables including possible interactions.
Results – On average 1.0, 2.0, 3.9, 7.6, 15.2, 25.3, 27.6, and 19.2 airways per subject were included from generation 0-7. Results are shown in figures 1 and 2 for GOLD groups and emphysema, respectively.
Conclusions – Airway distensibility decreases significantly with increasing severity of both GOLD status and emphysema, indicating that in COPD the dynamic change in airway calibre during respiration is compromised. Chronic bronchitis and emphysema appear to be interacting in causing airway narrowing, the latter most likely due to loss of elastic recoil of surrounding tissue.
| Original language | Danish |
|---|---|
| Publication date | 2013 |
| Number of pages | 1 |
| Publication status | Published - 2013 |