Evaluation method of a contact pressure between an optical sensor and the skin of a user and associated device
An evaluation method of a contact pressure between an optical sensor and a skin of a user, the method including a) determination of first optical data, using a first optical signal obtained by the optical sensor at a first wavelength, b) determination of second optical data, using a second optical signal obtained by the optical sensor at a second wavelength, different from the first wavelength, c) analysis of at least one comparison of the first optical data with the second optical data, the analysis generating information relating to the contact pressure between the optical sensor and the skin.
1 . A notification generation method for evaluating a contact pressure between an optical sensor of a measuring device and a skin of a user, the method comprising:
a) determining first optical data, using a first optical signal obtained by the optical sensor at a first wavelength, the first optical signal being an optical signal modulated by the heartbeat and the determining of the first optical data comprising processing involving extraction of pulsatile data from the first optical signal, wherein the first optical data comprises the first pulsatile data;
b) determining second optical data, using a second optical signal obtained by the optical sensor at a second wavelength, different from the first wavelength, the second optical signal being an optical signal modulated by the heartbeat and the determining of the second optical data comprising processing involving extraction of pulsatile data from the second optical signal, wherein the second optical data comprises the second pulsatile data;
c) analyzing at least one comparison of the first optical data with the second optical data, the analyzing generating information identifying an excessive contact pressure between the optical sensor and the skin, and
d) depending at least on a result of the analyzing, generating notification instructions for the user, the notification prompting the user to modify the contact pressure between the skin and the measuring device.
2 . The notification generation method according to claim 1 , wherein the comparison is carried out by calculating a parameter from the first optical data and the second optical data, a value of the parameter being representative of the contact pressure between the optical sensor and the skin, wherein the calculating of the parameter comprises calculating a ratio between the first optical data and the second optical data.
3 . The notification generation method according to claim 2 , wherein analyzing the at least one comparison comprises comparing a value of the parameter with a threshold.
4 . The notification generation method according to claim 3 , wherein the threshold is between 0.5 and 10.
5 . The notification generation method according to claim 1 , wherein each determining of the first and second optical data comprises transmitting an optical signal at, respectively, the first and second wavelengths and receiving, respectively, the first and second optical signals that have passed through the biological tissues of the user.
6 . The notification generation method according to claim 1 , wherein the first optical data are determined using a first perfusion index and the second optical data are determined using a second perfusion index.
7 . The notification generation method according to claim 1 , wherein the first wavelength is less than 600 nm and the second wavelength is strictly greater than 600 nm.
8 . The notification generation method according to claim 1 , wherein the first wavelength is between 400 and 600 nm and the second wavelength is between 600 and 1000 nm.
9 . The notification generation method according to claim 1 , wherein a difference between the first wavelength and the second wavelength is at least 50 nm.
10 . The notification generation method according to claim 1 , wherein the first wavelength is less than 540 nm and the second wavelength is greater than 650 nm or greater than 800 nm.
11 . The notification generation method according to claim 1 , wherein the first wavelength is between 480 nm and 540 nm and the second wavelength is between 650 nm and 665 nm or between 920 nm and 960 nm.
12 . The notification generation method according to claim 1 , wherein the first wavelength corresponds to green, blue or yellow, and the second wavelength corresponds to red or infrared.
13 . The notification generation method according to claim 1 , comprising:
determining third optical data, using a third optical signal obtained by the optical sensor at a third wavelength, different from the first wavelength and the second wavelength,
the third optical signal being a heartbeat-modulated optical signal and the determining of the third optical data comprising processing involving extraction of pulsatile data from the third optical signal,
the analyzing comprising analysis of a first comparison of the first optical data with the second optical data and analysis of a second comparison of the first optical data with the third optical data.
14 . The notification generation method according to claim 13 , wherein the first and second comparisons are carried out by a calculation of a first parameter from the first optical data and the second optical data, and a calculation of a second parameter from the first optical data and the third optical data, wherein values of the first and second parameters comprising information relating to the contact pressure between the optical sensor and the skin, the analyzing comprising a comparison of each of the first and second parameters with a threshold.
15 . The notification generation method according to claim 13 , wherein the third wavelength is greater than 800 nm.
16 . The notification generation method according to claim 1 , comprising initiating an optical measurement using the optical sensor and interrupting the optical measurement depending on a result of the analyzing.
17 . A non-transitory computer readable medium comprising machine readable instructions which, when the instructions are executed by a computer, cause the computer to implement the method according to claim 1 .
18 . A measuring device comprising an optical sensor comprising a light source configured to generate light towards a skin of the user and a light receiver, configured to detect light from the skin of the user, wherein the measuring device is configured to implement the method according to claim 1 .
19 . The measuring device according to claim 18 , comprising a wristband for tightening the optical sensor against the skin of the user.
20 . The notification generation method according to claim 1 , wherein the measuring device is configured to receive a finger on the optical sensor.
21 . The notification generation method according to claim 1 , wherein determining the first optical data comprises calculating a first perfusion index for the first optical signal and determining the second optical data comprises calculating a second perfusion index for the second optical signal, each perfusion index being a ratio of a pulsatile AC component to a non-pulsatile DC component of the respective optical signal.
22 . The notification generation method according to claim 1 , wherein analyzing the at least one comparison comprises calculating a parameter as a ratio of the first optical data to the second optical data and comparing the parameter to a predefined threshold, the method further comprising generating the notification instructions when the parameter indicates that the contact pressure exceeds the threshold.
23 . A notification-generation method for evaluating contact pressure between a wearable optical sensor and a user's skin, comprising:
(a) obtaining a first photoplethysmography (PPG) signal at a first wavelength in the range of 480-540 nm and extracting a first pulsatile component from said first PPG signal to produce first optical data;
(b) obtaining a second PPG signal at a second wavelength in the range of 650-1000 nm and extracting a second pulsatile component from said second PPG signal to produce second optical data;
(c) calculating a ratio of the first optical data to the second optical data, wherein the first optical data and second optical data each comprise a heartbeat-induced pulsatile amplitude of the respective PPG signal;
(d) comparing the calculated ratio to a predetermined pressure-indicative threshold associated with an excessive contact pressure; and
(e) based on the comparison, automatically generating a notification to the user to adjust contact pressure between the sensor and the skin when the comparison indicates the contact pressure is excessive.