Impact of pulmonary artery pressure on exercise function in severe COPD

Abstract

Background: Although pulmonary hypertension commonly complicates COPD, the functional consequences of increased pulmonary artery pressures in patients with this condition remain poorly defined.

Methods: We conducted a cross-sectional analysis of a cohort of 362 patients with severe COPD who were evaluated for lung transplantation. Patients with pulmonary hemodynamics measured by cardiac catheterization and available 6-min walk test results were included. The association of mean pulmonary artery pressure (mPAP) with pulmonary function, echocardiographic variables, and 6-min walk distance was assessed.

Results: The prevalence of pulmonary hypertension (mPAP, > 25 mm Hg; pulmonary artery occlusion pressure [PAOP], < 16 mm Hg) was 23% (95% confidence interval, 19 to 27%). In bivariate analysis, higher mPAP was associated with lower FVC and FEV(1), higher Pco(2) and lower Po(2) in arterial blood, and more right heart dysfunction. Multivariate analysis demonstrated that higher mPAP was associated with shorter distance walked in 6 min, even after adjustment for age, gender, race, height, weight, FEV(1), and PAOP (-11 m for every 5 mm Hg rise in mPAP; 95% confidence interval, -21 to -0.7; p = 0.04).

Conclusions: Higher pulmonary artery pressures are associated with reduced exercise function in patients with severe COPD, even after controlling for demographics, anthropomorphics, severity of airflow obstruction, and PAOP. Whether treatments aimed at lowering pulmonary artery pressures may improve clinical outcomes in COPD, however, remains unknown.

Figure 1

Six-minute walk distance declines with increasing mPAP even after adjustment for age, gender, race, height, weight, FEV₁, and PAOP. Data are presented as the least square means from linear regression with SE bars. The p value reflects the overall test for trend.