Abstract
Background: The 6-min walk test (6MWT) has been used to assess functional exercise performance in patients with COPD. Although hypoxemia has been occasionally accompanied with the 6MWT in patients with COPD, the oxygenation state of the lower limb muscles during the test has not been investigated.
Aims: To determine the oxygenation state of the calf muscle during the 6MWT in patients with COPD and healthy elderly subjects using a mobile near infrared spectroscopy (NIRS) device. Methods: Seven male patients with COPD (COPD group: age, 71.4 ± 2.8 years) and 6 healthy elderly men (H group: age, 69.2 ± 4.1 years) performed the 6MWT. Changes in oxygenated hemoglobin (oxy-Hb), deoxygenated hemoglobin (deoxy-Hb), and total hemoglobin (t-Hb) in the right gastrocnemius muscles (MG) during the 6MWT were measured by NIRS. In addition, SpO2 and pulse rate were monitored by a pulse oximeter. Δt-Hb and Δoxy-Hb were calculated from the difference between the lowest value at the early phase of walking and the value at the cessation of the 6MWT. Exercise intensity was estimated by the Karvonen formula.
Results: The lowest value of SpO2 during the 6MWT was 84.6 ± 9.2% in the COPD group. Walking distance was not significantly different between the COPD (492.3 ± 56.5 m) and the H group (578.0 ± 42.9 m). The COPD group showed low Δoxy-Hb values despite a low exercise intensity. The oxy-Hb value decreased along with SpO2 in two patients with COPD.
Conclusion: The oxygenation state of MG during the 6MWT in patients with COPD may be different from that in healthy elderly men. The blood oxygen saturation may influence the oxygenation of MG during the 6MWT.
- Copyright ©ERS 2015