Patent ID: 8515537

Claim:
A method for controlling a therapy in a patient, comprising; sensing an activity sensor signal; detecting a change in activity level of the patient from the activity sensor signal; sensing an optical sensor signal corresponding to tissue light attenuation in a tissue volume; computing a tissue oxygenation measurement from the optical sensor signal in response to detecting the change in activity level, the tissue oxygenation measurement comprising contributions from arterial and venous blood in a measurement volume, wherein computing the tissue oxygenation measurement comprises computing a trend; detecting a decrease in tissue oxygenation in response to the tissue oxygenation measurement, wherein detecting a decrease in the tissue oxygenation measurement comprises: defining a plurality of thresholds for each one of a respective plurality of activity levels, selecting one of the plurality of thresholds in response to detecting the change in activity; and comparing the tissue oxygenation measurement and the selected one of the plurality of thresholds; and adjusting a parameter controlling delivery of the therapy in response to detecting the decreased tissue oxygenation.