CT measurement of airway wall thickness and emphysema in COPD: Correlation with pulmonary hypertension - 04/04/15

Pulmonary hypertension (PH) is a common complication of COPD associated with increased mortality. The mechanisms coupling PH and bronchial obstruction are unknown; in particular PH appears unrelated to emphysema. We hypothesized that CT measurement of airway remodeling instead of emphysema may correlate with PH in COPD.

Data were retrieved from 60 COPD patients who had both right heart catheterization (RHC) and CT in a period of stability, and no other disease known to cause PH. CT measurement of airway wall thickness (WT) was assessed from the third to the fifth bronchial generation in 4 bronchial paths. Low lung area percentage (LAA %) was used to quantify emphysema extent.

Thirty-four out of 60 COPD patients had PH (mean pulmonary arterial pressure [PAP_m]≥25mmHg). There was no difference between the two groups regarding age, sex, and spirometric results, whereas there was more profound hypoxemia in the PH group. WT measured at the fourth (WT4) and fifth generation (WT5) was increased in COPD with PH and correlated with PAP_m (r=0.40; P=0.01 and r=0.63; P<0.001, respectively). Conversely, there was no difference or correlation between PAP_m and LAA % (r=0.13; P=0.28).

This study demonstrates for the first time an association between structural alteration of bronchi and PH in COPD. Unlike quantification of emphysema, CT measurement of bronchial wall thickness correlates with PAP_m and could estimate the severity of PH in COPD. Airway remodeling burden is not limited to airflow limitation to explain COPD severity and mortality (Fig. 1).