Association of exercise capacity and endothelial function in patients with severe exacerbations of chronic obstructive pulmonary disease

Abstract

Severe acute exacerbations of chronic obstructive pulmonary disease (AECOPD) are associated with significant poor outcomes including an increased risk of cardiovascular (CV) events and exercise intolerance. Endothelial dysfunction might contribute to an impaired vascular homeostasis and consequently to CV events and exercise capacity. This study aimed to evaluate the association between exercise capacity and endothelial function in patients with severe AECOPD. Forty-five COPD patients diagnosed with severe AECOPD and admitted to the University Hospital of São Carlos from 2017 to 2019 were enrolled in this observational clinical study. Endothelial Function was assessed by brachial artery ultrasonography (M-Turbo, Sonosite, Bottle, WA, USA) and Flow Mediated Dilatation (FMD) technique in absolute (mm) and percentage values (%). Walking distance (6MWD) obtained by six-minute walk test was considered to characterize the exercise capacity. Pearson's correlation analysis and linear regression model were applied and a significance level of 5%. There was a significant positive correlation between exercise capacity and endothelial function. Pearson correlation coefficient were 0.36 (p = 0.02) and 0.40 (p = 0.01) between 6MWD and FMD in mm and %, respectively. Linear regression model revealed 6MWD (p = 0.007), accounting for 15% of FMD (%) variance (R² adjusted). FMD (%) = 2.11 + (0.0081*6MWD). Exercise capacity is associated with endothelial function in patients with severe AECOPD. FMD was found to be increasing with increasing walked distance. Further research is needed to provide evidence of effectiveness of rehabilitation on exercise capacity and endothelial function in these patients and its prognostic value.

Figure 1

Measurement of FMD. The baseline diameter (D1) between the proximal and distal intima was recorded before RH. The Cuff was inflated at 200 mmHg during 5 min. Immediately after brachial artery ischemia, the diameter post RH (D2) was recorded. The release of cuff should cause increased flow to the region, promoting increased shear stress, greater release of nitric oxide and, consequently, vasodilation. FMD was expressed as the change in percentage: [(baseline diameter − diameter post RH)/baseline diameter × 100] and absolute (diameter post RH − baseline diameter).

Figure 2

Study flow. COPD chronic obstructive pulmonary disease;

Figure 3

Correlations between exercise capacity and endothelial function. Data are presented as the correlation coefficient (r) and p <  0.05. Relationship between exercise capacity and endothelial function: (A) The FMD (mm) was positively associated with the 6MWD; (B) The FMD (%) was positively associated with the 6MWD. FMD (mm): absolute values; 6MWD was expressed in meters. The figure was create using SigmaPlot version 11.0, from Systat Software, Inc., San Jose California USA, www.systatsoftware.com.