Arterial and mixed venous oxygen desaturation during incremental exercise in patients with chronic pulmonary disease

We evaluated arterial and mixed venous oxygen desaturation during symptom-limited exercise in patients with chronic pulmonary disease. Patients were divided into five groups according to disease: [chronic pulmonary emphysema (CPE), chronic bronchitis (CB), pulmonary tuberculosis sequalae (TB-seq), fibrosing lung disease (FLD), and pulmonary vascular disease (PVD)]. There were no significant difference in the values of arterial (PaO2) and mixed venous (PvO2) oxygen tension before and at the end of exercise among the five groups, whereas absolute decreases in PvO2 were significantly larger in PVD and FLD. The changes in PvO2 were similar to the changes in the coefficient of oxygen delivery (COD) which is equal to oxygen transport divided by oxygen consumption. These results suggest that the relative decrease in oxygen transport during exercise due to the high ratio of oxygen extraction by tissues is an important factor to determine decreases in PvO2 in pulmonary hypertensive disease and fibrosing lung disease.