Pulmonary Function and Regional Distribution of Emphysema as Determined by High-Resolution Computed Tomography

Abstract

In patients with pulmonary emphysema, emphysematous changes are not uniform and vary from minimum alveolar destruction to advanced bullous formation, depending on the lobe or site in the lungs. However, we have little knowledge on whether or how this nonuniformity or localization affects pulmonary function in PE patients. Therefore, we measured the computed tomography (CT) density of divided sites in lungs with high-resolution CT images from 25 PE patients (FEV_1.0%, mean ± SD 36 ± 9%, %DL_CO 48 ± 16%, all men, 68 ± 4 years) and compared them to various parameters of pulmonary function. The mean CT density of whole lungs correlated with 12 pulmonary function parameters including FEV_1.0 and diffusion capacity. When both lung fields were divided into peripheral, intermediate and central portions, the CT density of the central portion correlated with all pulmonary function parameters with which CT density of whole lungs correlated. In contrast, the CT density of the peripheral portion significantly correlated with only 7 parameters with smaller correlation coefficient values than those of the central portion. When divided into upper, middle and lower portions, the CT densities of upper, middle and lower portions correlated with 6, 8 and 10 of the 12 pulmonary function parameters which correlated with the density of whole lungs, respectively. The delta value of CT densities between the upper and lower portions or between the lateral and medial portions correlated with obstructive impairment (FEV_1.0 and FEV_1.0%). These findings suggest that (1) central rather than peripheral emphysematous changes affect pulmonary function, and (2) uniformity of emphysematous change correlates with the severity of airway obstruction in PE patients.

Quantitative computed tomography assessment of lung structure and function in pulmonary emphysema

“…Thus, in the relatively underventilated upper lung zone, emphysema produces smaller measurable pulmonary dysfunction than in the lower zone. Consistently, GURNEY et al [67] and HARAGUSHI et al [68] showed that the extent of emphysema had higher correlations with DL,CO in the lower lung zone than in the upper lung zone, even though the upper lung zone was more severely affected by emphysema. On the basis of the lobar distribution of emphysema as determined by CT, SAITOH et al [69] reported that the airflow limitation, the RV and the TLC were higher in the predominantly lower-lobe emphysematous group than in the predominantly upper-lobe emphysematous group.…”

Outcomes for COPD pharmacological trials: from lung function to biomarkers

“…Mean lung density (MLD) is calculated by averaging the density of all pixels in the image that represent the entire lung. It has been validated by correlation with lung function tests [320][321][322][323]. The percentile point is defined as the cut-off density value in Hounsfield units (HU), for which a predetermined percentage of all voxels has a lower value and, as with MLD, is also influenced by density changes in all lung structures [324,325].…”

Computed tomographic emphysema distribution: relationship to clinical features in a cohort of smokers

“…NAKANO et al [11] also found that core disease was related to disease severity (as measured by pulmonary function tests), with lower/core disease more related to spirometry, and upper/core to carbon monoxide transfer factor. HARAGUCHI et al [10] found that centrally distributed emphysema had the strongest relationship to pulmonary function, and also that lower-zone disease related better than upper.…”

“…Areas of the lung with a density below a given threshold (commonly -950 Hounsfield units (HU)) are designated as emphysematous. This technique has been validated against pathology [3,4] and pulmonary function [5,6]. In addition, the technology can be used to assess the distribution of emphysematous disease, an approach that has been utilised in assessing patients for (and in the outcomes of) lung volume reduction surgery [7,8] and also in monitoring changes in emphysema longitudinally in a 1 -antitrypsin-deficient patients [9].…”

“…This heterogeneity is reflected in the wide variation in clinical features seen. Despite this, there is a paucity of studies investigating how differences in the distribution of emphysema relate to different clinical features among patients with COPD [10,11].…”