Correlation of cardiopulmonary exercise testing parameters with quality of life in stable COPD patients

The precise head to head relationships between Cardio-pulmonary exercise testing (CPET) parameters and patients' daily symptoms/activities and the disease social/emotional impact are less well defined. In this study, the correlation of COPD daily symptoms and quality of life [assessed by St. George's Respiratory Questionnaire (SGRQ)] and COPD severity index (BODE-index) with CPET parameters were investigated.

Symptom-limited CPET was performed in 37 consecutive COPD (GOLD I-III) subjects during non-exacerbation phase. The SGRQ was also completed by each patient.

SGRQ-score correlated negatively with FEV1 (r=-0.49, P<0.01), predicted maximal work-rate (%WR-max) (r=-0.44, P<0.01), V'O2/WR (r=-0.52, P<0.01) and breathing reserve (r=-0.50, P<0.01). However it did not correlate with Peak-V'O2% predicted (r=-0.27, P=0.10). In 20 (54.1%) subjects in which leg fatigue was the main cause for stopping the test, Peak-V'O2, %WR-max, HR-Reserve and Breathing reserve were higher (P=0.04, <0.01, 0.04 and <0.01 respectively) than the others. There was also a significant correlation between BODE-index and ∆VO2/∆WR (r=-0.64, P<0.001) and breathing-reserve (r=-0.38, P=0.018).

The observed relationships between CPET parameter and daily subjective complaints in COPD were not strong. Those who discontinued the CPET because of leg fatigue were in the earlier stages of COPD. Significant negative correlation between ∆VO2/∆WR and BODE-index suggests that along with COPD progression, regardless of negative past history, other comorbidities such as cardiac/musculoskeletal problems should be sought.