Exercise-induced hypoxaemia in emphysematous type chronic obstructive pulmonary disease.

To investigate gas exchange response to exercise, we studied 16 male patients with moderate-to-serve airflow obstruction (forced expiratory volume in one second (FEV1) 39 +/- 10% of predicted value), mild-modest arterial hypoxaemia (arterial oxygen tension (Pa,O2) 9.6 +/- 0.87 kPa) and no arterial hypercapnia (arterial carbon dioxide tension (Pa,CO2) 5.04 +/- 0.45 kPa), referred to as emphysematous-type chronic obstructive pulmonary disease (COPD) clinical pattern. During maximal exercise tests, Pa,O2 increased by more than 0.3 kPa in eight patients (Group A) and fell by more than 0.3 kPa in the other eight patients (Group B). Pulmonary function tests, maximal inspiratory pressure at the mouth, values at maximum cycle incremental exercise and baseline arterial blood gases did not differ significantly between the two groups. We, therefore, showed that common pulmonary function measurements at rest and during exercise were not useful in identifying patients who underwent exercise-induced hypoxaemia. Furthermore, we suggest that patients with the same clinical pattern of chronic obstructive pulmonary disease and the same degree of airflow obstruction and gas exchange impairment could develop a different adaptation to a maximal exercise test, and that the presence of exercise-induced hypoxaemia might be related to pathological features of emphysema more than to different respiratory functional measurements.