Correlation of levels of obstruction in COPD with lactate and six-minute walk test

Chronic obstructive pulmonary disease (COPD) is a leading cause of morbid-mortality world wide, leading not only to pulmonary damage but also to multi-systemic impairment, with repercussions on skeletal Muscles and the ability to undertake effort, as measured in the six-minute walk test (6-MWT). Aims: To correlate the level of obstruction in COPD with lactate concentration and heart rate (HR) at rest, and distance walked. To correlate distance walked with blood gas analysis and correlate desaturation in 6-MWT with post 6-MWT lactate concentration and heart rate. Methods: COPD patients underwent spirometry, blood gas analysis and 6-MWT to evaluate distance walked, heart rate, capillary lactate (CL) concentration pre- and post 6MWT, and desaturation with 6-MWT. Results: 91 patients with all levels of obstruction were evaluated. HR and CL increased significantly post 6-MWT. The decrease in peripheral saturation of haemoglobin to oxygen observed with 6-MWT was also significant. The distance walked was shorter the greater the obstruction. The correlation analysis was significantly positive between FEV1 and distance walked, negative between FEV1 and HR at rest and negative between distance walked and PaCO2, and not significant for the other variables. Conclusions: Increased obstruction in COPD and higher PaCO2 values contribute to a reduction in distance walked in 6-MWT. The level of obstruction in COPD leads to a haemodynamic impairment with increased HR at rest of these patients.