COPD phenotypes on computed tomography and its relationship with exercise and ventilatory function

Abstract

Introduction: Quantitative computed tomography (CT) has been used to phenotype patients with chronic obstructive pulmonary disease (COPD). The relationship of COPD phenotypes and disease severity has recently gained attention.

Objective: To evaluate the relationship between CT phenotypes of COPD patients and ventilatory function tests and 6-min walk test (6MWT) findings.

Methods: COPD patients were phenotyped into normal, air dominant, emphysema dominant and mixed type based on CT scans using two cutoffs: percentage of low attenuation area (%LAA) less than a threshold of -950 Hounsfield units of 15% and the upper quartile value of the percentage of bronchial wall area (WA%/BSA).

Results: Eighty (80) COPD patients (78.8% males) were included. Median age was of 66,5±16 years. COPD phenotypes were categorized as normal (n=32, 40.0%), air dominant (n=21, 26.3%), emphysema dominant (n=20, 25.0%) and mixed type (n=7, 8.8%). Mixed type showed the lowest body mass index (BMI), DLCO and KCO values and the most 6MWT desaturation (p<0.05) followed by emphysema dominant type. The emphysema score (LAA%) was inversely correlated to percentage predicted FEV1 (r=-0.292, p<0.05), DLCO (r=-0.542, p<0,05), BMI (r=-0.453, p<0.05) and aortic pulmonary artery ratio (r=-0.341, p<0.05). Conversely, the emphysema score was positively correlated to predicted TLC (r=0.261, p<0.05) and 6MWT desaturation (r=0.416, p<0.05).

Conclusion: Emphysema phenotypes (dominant or mixed) on CT were characterized by worst lung function and greater exercise impairment. CT phenotyping may become an important complementary tool to ventilatory function to illustrate disease severity.