Exercise-Induced Changes in Oxygen Saturation in the Calf Muscles of Elderly Subjects With Peripheral Vascular Disease

Abstract

This study noninvasively measured hemoglobin oxygen saturation in young (n = 6,28 ± 6 yrs), old healthy (n = 20, 68 ± 7 yrs), and old subjects with mild peripheral vascular disease (PVD) (n = 8,72 ± 4 yrs). Hemoglobin oxygen saturation was measured as the difference in absorption at 760 and 850 nm light using near-infrared spectroscopy (NIRS). The lateral soleus muscle was studied after mild plantar flexion exercise. The time constant of recovery of oxygen saturation (HBO₂Tc) was 21.5 ± 8.6 s in young, 26.9 ± 13.5 s in old healthy subjects. PVD subjects had HbO₂Tc values of 104.4 ± 41.1 s in their “bad” leg and57.6 ± 42.2 s in their “good” leg. The correlation between HbO₂Tc and ankle-arm pressures was significant (r² = .63, p < .001). Six younger normal, five older normal, and seven PVD subjects also performed a progressive walking test. Normal subjects completed the test without difficulty, and older normal subjects showed progressive deoxygenation. PVD subjects complained of calf pain (4 out of 5 were able to finish) and showed near-maximal deoxygenation throughout the test. In summary, NIRS measurements show promise as a method of evaluating the kinetics of oxygen saturation, particularly in patients with mild peripheral vascular disease.