Submaximal spiroergometric parameters are unaffected by severity of chronic obstructive pulmonary diseases

The Global initiative for chronic obstructive lung diseases (GOLD) reports a staging system for chronic obstructive pulmonary disease (COPD) based on airflow limitations at rest. Cardiopulmonary exercise testing (CPET) is used in surveys to determine the remaining working capacity concerning the degree of disability and the disability benefit payment after rehabilitation in patients with COPD. The aim of the present study was to examine if sub-maximal exercise levels also correlate with COPD disease stage.

A total of 63 consecutive male patients with COPD and 24 elderly healthy volunteers underwent pulmonary functional tests including CPET. Work capacity, oxygen uptake, ventilation volume, carbon dioxide production and arterial blood gases were measured.

Exercise capacity, oxygen uptake, ventilation volume, oxygen pulse, carbon dioxide output and arterial oxygen pressure decreased significantly (p<0.001) with advancing GOLD stage. Significant positive correlations (p<0.001) to GOLD stage were seen for the alveolar-arterial differences for oxygen pressure and arterial carbon dioxide pressure. Weight-related exercise capacity (p<0.001), oxygen uptake (p<0.01) and lactate concentrations (p<0.05) were significantly lower in patients with COPD. Reduction of (weight-related) oxygen uptake, ventilation volume, oxygen pulse or carbon dioxide output at identical sub-maximal workload was not detected according to GOLD stage, not in comparison of patients with healthy individuals.

The GOLD staging system correlates with maximal CPET. At identical workload, discrimination between patients with different GOLD stages and healthy individuals was not possible. For the detection of exercise impairment, maximal CPET is recommended.