The oxygenation level of a tissue is an important marker of the health of the tissue. Sustained extreme oxygenation levels, in either direction, can cause irreparable damage. In stroke survivors, it has been shown that the blood flow to paretic limbs is significantly reduced compared to a non-paretic limb. We hypothesize that hemodynamic activity in stroke affected muscles is suppressed as compared to normal muscles.A clear understanding of the way stroke-affected limbs respond to rehabilitation exercises and a convenient method for monitoring this progress will allow clinicians and therapists to tailor treatments based on individual response.

In order to measure the hemodynamic activity, we developed a prototype optical sensor to measure the relative changes in the concentration of oxygenated and reduced hemoglobin (Hb and HbO2) in the tissue using Beer’s Law:

The sensor consists of four LEDs and twelve photodetectors.Three near infrared (NIR) light are used for our oximetry measurements because if its ability to penetrate tissues. The are placed along the flexors and extensors of a subject while they undergo a hand exercise. The exercise consists of pushing on a force plate using one’s fingers

Left: placement of the probes on the muscles of the subject. Right: experimental setup.

This figure shows the repsonse of muscle oxygenation (Oxy) an the blood volume for four patients during periods of exercise. Exercise is performed during the periods in which the light blue step function is high, and rest occurs when the step function is low. The intensity of the exercise given as a percent of the MVC is noted for each interval.