Prognostic value of key variables from cardiopulmonary exercise testing in patients with COPD: 42-month follow-up

Aim: To identify better predictors of early death in patients with chronic obstructive pulmonary disease (COPD) using potential predictors derived from key measures obtained from cardiopulmonary exercise testing (CPET).

Methods: This is a prospective, cohort study with 42-month follow-up in 126 COPD patients. Every patient completed the clinical evaluation, followed by a pulmonary function test and CPET. CPET was performed on a cycle ergometer with electromagnetic braking and ventilatory expired analysis was measured breath-by-breath using a computer-based system. Peak oxygen consumption (V̇O_2, mlO_2. kg^-1_. min^-1), minute ventilation/carbon dioxide production and the, minute ventilation (V̇_E, L/min), and the V̇_E/carbon dioxide production (V̇_E/V̇CO₂) slope were obtained from CPET.

Results: 48 (38%) patients died during the 42-month follow-up. Kaplan Meier analysis revealed a V̇_E/V̇CO₂ slope ≥30, peak V̇_E ≤ 25.7L/min and peak V̇O₂ ≤ 13.8 mlO_2. kg^-1_. min^-1were strong predictors of mortality in COPD patients. Cox regression revealed that the V̇O₂ peak ≤13.8 mlO_2. kg^-1_. min^-1 (CI 95% 0.08-0.93), V̇_E/V̇CO₂ slope ≥30 (CI 95% 0.07-0.94), V̇_E peak ≤25.7 L/min (CI 95% 0.01-0.15), Sex (CI 95% 0.04-0.55) and Age (CI 95% 1.03-1.2) were the main predictors of mortality risk.

Conclusion: Diminished exercise capacity and peak ventilation as well as ventilatory inefficiency are independent prognostic markers. Similar to patients with heart failure, CPET may be a valuable clinical assessment in the COPD population.