Value of Cardiopulmonary Exercise Testing in the Prognosis Assessment of Chronic Obstructive Pulmonary Disease Patients: A Retrospective, Multicentre Cohort Study

Abstract

Introduction: Chronic obstructive pulmonary disease (COPD) is one of the most common chronic diseases associated with high mortality. Previous studies suggested a prognostic role for peak oxygen uptake (VO2peak) assessed during cardiopulmonary exercise testing (CPET) in patients with COPD. However, most of these studies had small sample sizes or short follow-up periods, and despite their relevance, CPET parameters are not included in the Global Initiative for Chronic Obstructive Lung Disease (GOLD) tool for assessment of severity.

Objectives: We therefore aimed to assess the prognostic value of CPET parameters in a large cohort of outpatients with COPD.

Methods: In this retrospective, multicentre cohort study, medical records of patients with COPD who underwent CPET during 2004-2017 were reviewed and demographics, smoking habits, GOLD grade and category, exacerbation frequency, dyspnoea score, lung function measurements, and CPET parameters were documented. Relationships with survival were evaluated using Kaplan-Meier analysis, Cox regression, and receiver operating characteristic (ROC) curves.

Results: Of a total of 347 patients, 312 patients were included. Five-year and 10-year survival probability was 75% and 57%, respectively. VO2peak significantly predicted survival (hazard ratio: 0.886 [95% confidence interval: 0.830; 0.946]). The optimal VO2peak threshold for discrimination of 5-year survival was 14.6 mL/kg/min (area under ROC curve: 0.713). Five-year survival in patients with VO2peak <14.6 mL/kg/min versus ≥ 14.6 mL/kg/min was 60% versus 86% in GOLD categories A/B and 64% versus 90% in GOLD categories C/D.

Conclusions: We confirm that VO2peak is a highly significant predictor of survival in COPD patients and recommend the incorporation of VO2peak into the assessment of COPD severity.

Keywords: All-cause mortality; Cardiopulmonary exercise testing; Chronic obstructive pulmonary disease; Lung function; Prognosis.

Fig. 1

Patient flow. COPD, chronic obstructive pulmonary disease; CPET, cardiopulmonary exercise testing; FEV₁, forced expiratory volume in 1 s.

Fig. 2

All-cause mortality according to GOLD grades. GOLD, global initiative for chronic obstructive lung disease.

Fig. 3

Survival according to the mBODE index (n = 275). mBODE, modified BMI, airflow obstruction, dyspnoea, and exercise capacity.

Fig. 4

Survival according to individual components of the mBODE index (n = 275). BMI, body mass index; FEV₁, forced expiratory volume in 1 s; mBODE, modified BMI, airflow obstruction, dyspnoea, and exercise capacity; mMRC, modified medical research council dyspnoea scale; VO₂peak, peak oxygen uptake.

Fig. 5

VO₂peak for discrimination of survival at 5 years. In ROC analysis (upper panels), VO₂peak = 14.6 mL/kg/min and VO₂peak = 55% predicted were identified as the optimal thresholds for prediction of survival at 5 years. Kaplan-Meier plots (lower panels) show survival in patient subgroups defined based on these thresholds. AUC, area under the curve (reported with 95% confidence interval); VO₂peak, peak oxygen uptake; ROC, receiver operating characteristic.

Fig. 6

ROC analysis of VO₂peak and multidimensional prognostic indices for discrimination of survival at 3 (left) and 5 (right) years. ADO, age, dyspnoea, and airflow obstruction; AUC, area under the curve (reported with 95% confidence interval); DOSE, dyspnoea, airflow obstruction, current smoking status, and exacerbations; mBODE, modified BMI, airflow obstruction, dyspnoea, and exercise capacity; VO₂peak, peak oxygen uptake; ROC, receiver operating characteristic.

Fig. 7

Kaplan-Meier analysis of survival in patients stratified by GOLD category and VO₂peak. GOLD, global initiative for chronic obstructive lung disease; VO₂peak, peak oxygen uptake.

Fig. 8

Suggested inclusion of VO₂peak in the GOLD ABCD refined assessment tool. COPD, chronic obstructive pulmonary disease assessment test; GOLD, global initiative for chronic obstructive lung disease; mMRC, modified medical research council dyspnoea scale; VO₂peak, peak oxygen uptake.