Noninvasive quantification of muscle oxygen in subjects with and without claudication

The disabling pain of intermittent claudication (IC) arises from oxygen deprivation in the lower limbs during walking. Measurement of the oxygen deficiency within the limb tissue now appears possible with recently expanded understanding of the photon transport through tissue for photons in the visible and near infrared range. Noninvasive measurement consists of preferentially measuring photons that have traveled more deeply into limb tissues and that, therefore, may reach locations of ischemic tissue. Oxygen measurements appear to be possible up to a depth approaching 1.5 cm beneath the surface of the skin. The present study reports on data acquired from the limbs of 11 subjects with IC and 12 subjects without IC. The subjects with IC are patients with clinical findings of claudication based upon segmental Doppler pressure profiles and subjective reports by the patient of pain during exercise. The subjects without IC are individuals with no prior history of ischemic vascular disease. The results consist of photon reflectance measurements at red and infrared wavelengths (approximately 660 nm and 880 nm respectively) taken before, during, and after exercise. Infrared reflectance indices are plotted as well as oxygenation indices generated from combining red and infrared reflectances. A compilation of exercise data shows responses that are generally consistent with the expected physiological responses to mild exercise in subjects with and without IC. We anticipate that the findings of this study may lead to an objective noninvasive testing procedure for measuring the ischemic and exercise-induced changes in muscle oxygenation in the presence of claudication. If the testing of ischemic hypoxia continues to show consistency and accuracy in determining the disability of the subjects with IC, future studies can more effectively test modes of conservative management, such as cessation of smoking, alternative exercise regimens, weight loss, and alternative pharmacological agents.