003. Association between dynamic hyperinflation and emphysema distribution in chronic obstructive pulmonary disease (COPD) patients

Abstract

Background

Dynamic hyperinflation (DH) is a major contributor of both dyspnea and reduced exercise capacity among patients with chronic obstructive pulmonary disease (COPD). The relationship between the pattern of distribution of emphysema (homogeneous versus heterogeneous) and DH has not been previously studied. The aim of the study was to compare the impact of emphysema distribution on DH during a maximal cardiopulmonary exercise testing (CPET) in severe COPD.

Methods

Data on COPD patients who underwent thorax high-resolution computed tomography, full lung function measurements and maximal CPET were retrospectively analysed. Resting inspiratory capacity (rIC) was calculated by averaging four resting IC maneuvers. ΔIC was calculated by subtracting the peak IC (pIC), that is the IC measured during the last 30 seconds of maximum exercise, from rIC and was expressed as ratio of rIC (ΔIC ratio). Emphysema quantification was conducted at 3 predefined levels for each patient using the syngo PULMO-CT (Siemens AG); a difference >25% between best and worse slice defined heterogeneous emphysema. Student’s t-test was used for group comparison, after normality of distribution was assessed; level of P<0.05 was considered significant.

Results

We identified 51 patients with heterogeneous emphysema (62.7% male; 60.9±7.5 years old; FEV₁%=32.4±11.4; TLCO%=34.1±10) and 13 with homogeneous emphysema (61.5% male; 62.5±5.9 years old; FEV₁%=28.1±10.3; TLCO%=33.3±11.5) who fulfilled the enrolment criteria. ΔIC ratio (0.40±0.1 vs. 0.31±0.13, P=0.031) was higher in patients with homogeneous compared to those with heterogeneous emphysema.

Conclusions

Homogeneous emphysema is associated with more DH during maximum exercise in COPD patients. Therefore, CT assessed emphysema pattern may have a role to play when considering treatment options, and may aid to form strategies to improve patient selection and responder rates for lung volume reduction techniques.