Patent ID: 8585602

Claim:
A system that is configured to produce an indicator that measures a response of a blood circulation system of a subject to postural change, comprising: pre-processing circuitry configured to detect a signal dependent upon an arterial blood volume in a limb of the subject when the subject is in a first posture and configured to detect a signal dependent upon an arterial blood volume in the limb of the subject responsive to a change in the subject's posture from the first posture to a second posture, different from the first posture; and processing circuitry configured to calculate a quantitative indicator that quantifies the response of the subject's blood circulation system to postural change and is dependent upon a ratio of a first input value to a second input value, wherein the processing circuitry is configured to determine automatically when the posture change occurs, the processing circuitry is configured to control the first input value to be the signal detected prior to the detected postural change; and the processing circuitry is configured to control the second input value to be the signal detected after the detected postural change.