Tissue oxygen saturation detection and related apparatus and methods
A wearable optical device is described for optically detecting parameters of interest within muscle, such as during physical activity or when at rest. The parameters of interest include oxygenation level and/or hemoglobin concentrations in some situations. The detected parameters, such as oxygenation level, may be used to assess physical performance, such as the extent to which the muscle is utilizing aerobic or anaerobic processes. Methods for determining the parameters of interest, such as oxygenation level, from the detected optical signals are also described, and feedback may be provided to a user.
1 . A system for optical measurement of oxygenation, the system comprising:
a wearable housing;
an optical source array in the wearable housing including a plurality of optical sources;
a plurality of optical detectors in the wearable housing, the plurality of optical sources and the plurality of optical detectors arranged in three or more source-detector pairs formed between at least two optical sources and at least two optical detectors, wherein:
the plurality of optical detectors and optical sources are arranged into two or more zones,
each of the two or more zones includes at least one pair of the optical sources or at least one pair of the optical detectors,
the two or more zones are arranged in a line spanning a surface above a volume of tissue, and
the optical detectors and the optical sources are arranged within the two or more zones such that none of the two or more zones include both an optical source and an optical detector and one or more source-detector pairs between two of the two or more zones are at different distances than one or more other source-detector pairs between the two of the two or more zones, and
each source-detector pair spanning the two or more zones probes a same volume of tissue spanned by the line between the two or more zones; and
a processor configured to convert optical signals from the plurality of optical detectors into an indication of oxygenation or hemoglobin concentration including one or more of muscle oxygenation (SmO 2 ), oxygenated hemoglobin concentration (HbO 2 ), deoxygenated hemoglobin concentration (Hb), or total hemoglobin concentration (HbT), wherein the processor is configured to apply a plurality of curve fitting procedures to a plurality of alternative combinations of the plurality of optical sources and the plurality of optical detectors to obtain depth-dependent information about the indication of oxygenation or hemoglobin concentration in inhomogeneous tissue having different optical properties at different depths.
2 . The system of claim 1 , wherein the plurality of optical detectors include at least a second optical detector larger than a first optical detector.
3 . The system of claim 1 , wherein the plurality of optical sources includes certain optical sources arranged substantially linearly with respect to one another.
4 . The system of claim 1 , wherein the plurality of optical detectors includes certain optical detectors arranged substantially linearly with respect to one another.
5 . The system of claim 1 , wherein the processor is disposed within the wearable housing and is coupled to outputs of the plurality of optical detectors.
6 . The system of claim 1 , further comprising an adjustable strap affixed to the wearable housing.
7 . The system of claim 1 , wherein the processor is configured to convert optical signals from the plurality of optical detectors into an indication of muscle oxygenation.
8 . The system of claim 1 , wherein the processor is configured to convert optical signals from the plurality of optical detectors into an indication of total hemoglobin concentration.
9 . The system of claim 1 , wherein the processor is configured to convert optical signals from the plurality of optical detectors into an indication of deoxygenated hemoglobin concentration.
10 . The system of claim 1 , further comprising a coil disposed on or within the wearable housing, the coil configured to receive a wireless charging signal.
11 . The system of claim 1 , further comprising wireless communication circuitry configured to wirelessly transmit data indicative of signals produced by the plurality of optical detectors.
12 . The system of claim 1 , wherein the wearable housing includes a recess in which the optical source array is disposed such that the optical source array lies beneath a surface of the wearable housing.
13 . The system of claim 1 , wherein the wearable housing includes a recess in which the plurality of optical detectors are disposed such that the plurality of optical detectors lie beneath a surface of the wearable housing.
14 . The system of claim 1 , wherein the plurality of optical sources includes certain optical sources arranged non-linearly with respect to one another.
15 . The system of claim 1 , wherein the plurality of optical detectors includes certain optical detectors arranged non-linearly with respect to one another.
16 . The system of claim 1 , wherein the plurality of optical sources include a plurality of LEDs.
17 . The system of claim 1 , wherein the plurality of optical sources emit light signals with at least two peak wavelengths in the red-to-infrared spectrum.
18 . The system of claim 1 , wherein the plurality of optical sources emit light signals with at least two peak wavelengths of 660 nanometers and 855 nanometers.
19 . The system of claim 1 , wherein the inhomogeneous tissue includes adipose tissue located superficially to muscle.
20 . The system of claim 1 , wherein the depth dependent information includes a measurement of superficial fat content in the tissue.