Apparatus for monitoring physiological signals

Abstract

The present invention relates to design improvements to reflective and transmissive photoplethysmographic (PPG) devices to reduce motion artifacts, avoid spurious and non-physiological baseline drift in the signal, and improve signal quality and accuracy of indices derived from PPG. The present invention can improve the accuracy of all PPG driven parameter estimations, such as blood oxygen saturation (SpO2), heart rate, heart rate variability, respiratory rate, blood pressure, and continuous measurement of arterial pulse wave volume (i.e. peripheral arterial tonometry and arterial pulse tonometry). The present invention also incorporates the ability to measure and / or track and / or compensate for changes in or absolute values of applied pressure between the sensor and the surface of the biological subject, which is applicable to all sensors or associated probes.

Description

W O 2 0 2 5 / 0 8 3 5 9 0 A 1 (12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (19) World Intellectual Property Organization International Bureau (43) International Publication Date 24 April 2025 (24.04.2025) (51) International Patent Classification: A61B 5 / 00 (2006.01) A61B 5 / 024 (2006.01) WIPO PCT A61B 5 / 0295 (2006.01) A61B 5 / 1455 (2006.01) (10) International Publication Number WO 2025 / 083590 A1 (21) International Application Number: PCT / IB2024 / 060167 (22) International Filing Date: 17 October 2024 (17.10.2024) (25) Filing Language: English (26) Publication Language: English (30) Priority Data: 2023903337 19 October 2023 (19.10.2023) AU (71) Applicant: COMPUMEDICS MEDICAL INNO- VATION PTY LTD [AU / AU]; 30-40 Flockhart Street, Ab- botsford, Victoria 3067 (AU). (72) Inventor: ALIAHMAD, Behzad; 30-40 Flockhart Street, Abbotsford, Victoria 3067 (AU). (81) Designated States (unless otherwise indicated, for every kind of national protection available): AE,(84) AG, AL, AM, AO, AT, AU, AZ, BA, BB, BG, BH, BN, BR, BW, BY, BZ, CA, CH, CL, CN, CO, CR, CU, CV, CZ, DE, DJ, DK, DM, (84) DO, ES, DZ, EG, EC Ge, GH, GM, GT, HN, HR, Hu, ID, IL, IN, IQ, IR, IS, IT, JM, JO, JP, KE, KG, KH, KN, KP, KR, KW, KZ, LA, LC, LK, LR, LS, LU, MW, MYN, MX, MX, MK, MD. MZ, NA, NG, NI, NO, NZ, OM, PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW, SA, SC, SD, SE, SG, SK, SL, ST, SV. SY, TH, TJ, TM, TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN, WS. ZA, ZM, ZW. Designated States (unless otherwise indicated, for every kind of regional protection available): ARIPO (BW, CV, GH, GM, KE, LR, LS, MW, MZ, NA, RW, SC, SD, SL, ST, SZ, TZ, UG, ZM, ZW), Eurasian, TJZ, TYZ, KY, TM, Europe, BZ, (AL, AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, FI, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV. MC, ME, MK, MT, NL. NO, PL, PT, O.AP, RO, SB, SE, RS. (BJ, CF, CG, CI, CM, GA, GN, GQ, GW, KM, ML, MR, NE, SN, TD, TG). Declarations under Rule 4.17: -as to the identity of the inventor (Rule 4.17(i)) - as to applicant's entitlement to apply for and be granted a patent (Rule 4.17(ii)) as to the applicant's entitlement to claim the priority of the earlier application (Rule 4.17(iii)) (54) Title: APPARATUS FOR MONITORING PHYSIOLOGICAL SIGNALS 16 5 8 6 4 7 3 19 18 1 14 11 13 12 17 FIG. 1 15 10 (57) Abstract: The present invention relates to the improvement in design of both reflective and transmissive photoplethysmography (PPG) devices to reduce motion artifacts, avoid false and non-physiological baseline shift in the signal, improve signal quality and accuracy of the metrics derived from the PPG. The invention results in an improved accuracy in estimation of all PPG driven parameters, such as blood oxygen saturation (SpO2), heart rate, heart rate variability, respiration rate, blood pressure and continuous measurement of the arterial pulse wave volume (i.e. peripheral and pulse arterial tonometry). The present invention incorporatesthe capability to measure and / or track and / or compensate for variations or absolute values of the applied pressure between a sensor and the surface of a biological subject, including all sensors or associated probes. [Continued on next page] WO 2025 / 083590 A1 Published: - with international search report (Art. 21(3)) in black and white; the international application as filed contained color or greyscale and is available for download from PATENTSCOРЕ 5 10 WO 2025 / 083590 Apparatus for Monitoring Physiological Signals Technical Field PCT / IB2024 / 060167 The present invention relates to an apparatus for acquiring electrophysiological signals associated with physiological processes, in particular, blood oxygen saturation of haemoglobin (SpO2) measurements. Background Photoplethysmography (PPG) is a non-invasive technique that is used for transcutaneous measurement of oxygen saturation of haemoglobin in arterial blood (i.e. SpO2) and allows for extraction of some valuable information such asheart rate, PPG driven respiration and respiration rate, arterial tone and pulse wave volume. It is a non-invasive technology that relies on two Light Emitting Diodes (LED), one Red 15 and one Near-Infrared (N-IR), plus a photodetector. 20 The principal application of a photoplethysmogram to measure SpO2 is based on the principle that the amount of red and near-infrared light absorbed by oxygenated (HbO2) and deoxygenated (Hb) Haemoglobin differ significantly. Hb absorbs a greater amount of red and a lower amount of N-IR light compared to HbO2. In other words, Hb reflects lower amount of red and greater amount of N-IR light compared to HbO2. This characteristic has been used as the basis for development of two types of oximeters known as i) transmissive and ii) reflective. In transmissive oximeters the photo diodes and the detector are placed on opposite sides of the measurement site, 25 such as the fingertips, and the amount of light transmitted through the tissue is detected by thereceiver, while in reflective oximeters both the light source and the detector are placed on the same side of the measurement site and the amount of light reflected from the tissue is captured. In both cases, the amount of light absorbed / reflected fluctuates because of i) changes in arterial blood volume during 30 systolic and diastolic phases of the cardiac cycle and ii) variations in blood oxygen concentration. The relative amount of red to N-IR absorbed is used to differentiate between cardiac cyclic variations and the changes in blood oxygen concentration. The accuracy of measurements of transmissive and reflective PPG devices is 35 susceptible to motion and change in contact pressure between a sensor and the skin. For the PPG devices to work reliably, a stable contact pressure is required which is not easily achievable as the pressure may change as the patient moves and, in the 1 WO 2025 / 083590 PCT / IB2024 / 060167 case where there is high amount of motion. Weak contact pressure canresult in severe light leakage and therefore, a weak and noisy PPG signal. In contrast, excessive pressure can result in vascular constriction, temporarily reduce or block blood perfusion and alter the morphology of the PPG signal. In both cases, non- 5 optimal contact pressure changes the morphology of the PPG signals (i.e. both Red and IR) and the relative intensity of Red to N-IR absorbed / reflected, resulting in a significant reduction in the accuracy and baseline of all PPG driven signals, including but not limited to, SpO2. This presents a problem especially when it comes to continuous monitoring over a long period of time, such as during an overnight sleep 10 study; as the contact pressure may vary by changes in position during sleep. This can introduce a bias in the diagnosis of medical conditions such as cardiopulmonary complications, sleep apnoea, chronic obstructive pulmonary disease (COPD) and heart failure. Non-optimal contact pressure will also lead to heaviercontamination of PPG by motion artifacts, reduced signal to noise ratio, PPG baseline wandering and 15 unreliable or erroneous heart rate measurements. What is needed is a better design for PPG devices to minimise these problems and provide improved measured 20 signals. Summary of the Invention The present invention provides apparatus with improved measurement of biological signals, in particular, photoplethysmographic measurements, of a subject. In one aspect, the invention provides apparatus for monitoring physiological signals of a subject, comprising of a flexible substrate for application to the subject's skin, 25 including at least one sensor for monitoring the physiological signals of the subject, a sensor for measuring oxygen concentration of blood, and a floating or sprung optical sensor to mechanically regulate the contact pressure and ensure vascular constrictions due to application of the sensor is always controlled, limited, and / or minimised. The invention advantageouslyprovides a mechanism for measuring the 30 pressure of the flexible substrate against the skin, or any limb or other surface part of the body. Preferably, the flexible substrate comprises of a flexible pressure sensitive material. Preferably, the invention incorporates an algorithm for automatic and real- time optimisation of the signals and adjustment to derived metrics according to the measured contact pressure. Preferably, the invention incorporates the capability to 35 measure and / or track and / or compensate for variations or absolute values of the applied pressure between a sensor and the surface of a subject, including all sensors or associated probes. Preferably, one or more applied sensor(s) or probe(s) can be 2 WO 2025 / 083590 PCT / IB2024 / 060167 deployed to achieve said functionality. Preferably, the measures or outcomes from the sensor can be modified, adapted, compensated, or computed in anyway considering the "applied pressure between a sensor and the surface of a subject' aspart of a related algorithm or any form of related computation. 5 Brief Description of the Figures 10 15 FIG.1 is side view of an embodiment of the invention incorporating the inventive reflective pulse oximeter equipped with pressure sensitive material or sensor. FIG.2 is a side view of an embodiment of invention incorporating the inventive transmissive finger clip pulse oximeter equipped with pressure sensitive material or sensor, showing a finger being inserted into the clip. Detailed Description of the Invention The present invention relates to the improvement in design of both reflective and transmissive photoplethysmography (PPG) devices to reduce motion artifacts, avoid false and non-physiological baseline shift in the signal, improve signal quality and accuracy of the metrics derived from the PPG. The invention results in an improved 20 accuracy in estimation of all PPG driven parameters, such as blood oxygen saturation (SpO2), heart rate, heart rate variability, respirationrate, blood pressure, and continuous measurement of the arterial pulse wave volume (i.e. peripheral and pulse arterial tonometry). The present invention incorporates the capability to measure and / or track and / or compensate for variations or absolute values of the 25 applied pressure between a sensor and the surface of a biological subject, including all sensors or associated probes. The invention most advantageously introduces a mechanism for the pulse oximeters to continuously monitor the contact pressure between the skin and the sensor and adjust / optimise the signals according to the contact pressure. The invention 30 incorporates a floating or sprung optical sensor to mechanically regulate the contact pressure and ensure vascular constrictions due to application of the sensor is always controlled, limited, and / or minimised. Advantageously, the invention provides a mechanism for measuring the pressure of the flexible substrate against the skin, or any limb or other surface part ofthe body. The invention may incorporate an 35 algorithm for automatic and real-time optimisation of the signals and adjustment to derived metrics according to the measured contact pressure. 3 WO 2025 / 083590 PCT / IB2024 / 060167 5 10 15 The invention may include the ability for measures or outcomes from the sensor to be modified, adapted, compensated, or computed in anyway considering the applied pressure between a sensor and the surface of a biological subject as part of a related algorithm or any form of related computation. The invention may assist in differentiation between cases with naturally low perfusion and blood flow restriction (i.e. vascular constriction) due to increased contact pressure. Advantageously, the invention can assist in differentiation between genuine low SpO2 baseline (i.e., are a result of conditions such as but not limited to Chronic obstructive pulmonary disease) and artifactual low baseline because of non-optimal contact pressure between skin and the sensor.This invention includes applications beyond the translucent body sites such as finger, toe, and earlobe where only transmissive optical sensors can be used. It expands the option / choices for greater choices of measuring sites and opens number of opportunities for development of wearable devices such as smart watches, forehead, and chest-worn PPG monitors with clinical grade level of accuracy. The invention preferably incorporates the application of a flexible pressure sensitive material such as "Velostat" or "Linqsatat" and / or an electronic pressure sensor, to engage with a spring-loaded optical sensor. The optical sensor is mounted on a spring of known type and specifications which can be made in any form such as a 20 coil or folded metal, to regulate the contact pressure against any body part. Addition of a presser sensor (or pressure sensitive material) to the spring-loaded optical sensor allows for the real-time measurement of a pressure signal that relates to the integrity of theconnection between the skin and the sensor. 25 The figures illustrate preferred embodiments of the invention. Other embodiments within the scope of the claims are possible. Referring now to FIG 1 is an embodiment of the reflective PPG device according to the invention, which incorporates a pulse oximetry function is shown on the skin 1 (i.e. measurement site). Depending on the location of the measurement site, it incorporates either a strap or adhesive patch 2 to 30 stay in place. The transmitter 3 and receiver 10 both are mounted on a rigid substrate 15 which itself is connected to the main rigid substrate 5 via two flexible substrates 9 and 18. These two substrates carry electrical signals from 15 to 16 and then to 5, which has all the electronic components 4, via the third flexible substrate 19. The pressure sensitive material or sensor 7 is placed between the two rigid substrates 5 35 and 16 to sense the contact pressure. A spiral spring 6 with a metal bar 12 to house 4 WO2025 / 083590 PCT / IB2024 / 060167 5 10 the spring is placed between substrates 15 and 16. This mechanism allows for the sensors and lenses move inside the plastic housing 8. This provides a capacity to absorb and release energy, add cushioning and help regulating contact force based on the shape of the measurement site. The transceivers 3 and 10 are covered by the plastic case 15 that has two cut-outs positioned on top of each of the sensors. These two cut-outs hold optical lenses 11 and 17 to carry light with a U-shaped optical isolator 13 in the middle, to block light leakage between the transmitter 3 and the receiver 10. This isolator has a U-shape to house the metal bar 12 when the spring 6 is compressed. Referring now to FIG 2, the drawing provides a further example of the embodiment of the invention as a transmissive PPG with finger clip probe showing a finger 1 being inserted into the clip. It has top 4 and bottom 9 housings which are interconnected with spring 7. The bottom housing9 houses the receiver 11 is fitted on the rigid 15 substrate 10 mounted on the pressure sensitive material 8. The top housing 4 houses the transmitter 3 mounted on the rigid substrate 5. All electronic components 2 are mounted on the other side of a rigid substrate 5. Inside the device opening there is the silicon cushion 6 to take the shape of the finger 1 and help regulating contact force between finger 1 and the transceivers 3 and 11. This cushion also 20 provides optical isolation and avoids light leaking from 3 to 11. 5 WO 2025 / 083590 Claims PCT / IB2024 / 060167 1. Apparatus for monitoring physiological signals of a subject, comprising of: a) a flexible substrate for application to the subject's skin; b) at least one sensor engaged with the flexible substrate for monitoring the physiological signals of the subject; c) a sensor engaged with the flexible substrate for measuring oxygen concentration of blood; and d) a floating or sprung optical sensor engaged with the flexible substrateto mechanically regulate the contact pressure and ensure vascular constrictions due to application of the sensor is always controlled, limited, and / or minimised. 2. The apparatus of claim 1, where the flexible substrate comprises of a flexible pressure sensitive material. 3. The apparatus of claim 1 or claim 2, further incorporating a microprocessor programmed with an algorithm to calculate automatic and real-time optimisation of the monitored signals and adjust derived metrics according to the measured contact pressure. 4. The apparatus of any of claim 1 to claim 3, further incorporating a microprocessor programmed to calculate and / or track and / or compensate for variations or absolute values of the applied pressure between the sensor and the surface of the subject. 6 1 / 2 2 1 6 1 8 00 1 9 5 1 5 2 1 7 F I G . 1 WO 2025 / 083590 PCT / IB2024 / 060167 1 0 N S 2 / 2 WO 2025 / 083590 PCT / IB2024 / 060167 6 1 1 1 0 8 F I G . 2 INTERNATIONAL SEARCH REPORT International application No. PCT / IB2024 / 060167 A.CLASSIFICATION OF SUBJEСТ МАТTER A61B 5 / 00 (2006.01) A61B 5 / 024 (2006.01) A61B 5 / 0295 (2006.01) A61B 5 / 1455 (2006.01) According to International Patent Classification (IPC) or to both national classification and IPC B. FIELDS SEARCHED Minimum documentation searched (classification system followed by classification symbols) Documentation searched other than minimum documentation to the extent that such documents are included in the fields searched Electronic data base consulted during the international search (name of data base and, where practicable, search terms used) PATENW cluster, (IPC / CPC): A61B5 / 02416, A61B5 / 0295, A61B5 / 14552, A61B5 / 6843, A61B5 / 6824, A61B5 / 681, A61B5 / 6826, A61B5 / 1455, A61B5 / 02007, A61B5 / 72, A61B5 / 0261. Keywords in addition to classification: Pulse oximeter, PPG, pressure sensor, spring, sprung, clip, elastic, pressure sensor, optic sensor, blood oxygen concentration, floating sensor, resilient, flexible, and similar terms in various combinations. Google Patents,Espacenet using similar keywords and classification symbols. C. DOCUMENTS CONSIDERED TO BE RELEVANT Category* Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No. Documents are listed in the continuation of Box C ☑ Further documents are listed in the continuation of Box C Special categories of cited documents: "A" document defining the general state of the art which is not "D" "E" considered to be of particular relevance document cited by the applicant in the international application earlier application or patent but published on or after the international filing date "L" document which may throw doubts on priority claim(s) or which is cited to establish the publication date of another citation or other special reason (as specified) "Ο" "P" document referring to an oral disclosure, use, exhibition or other means document published prior to the international filing date but later than the priority date claimed Date of the actualcompletion of the international search 17 January 2025 Name and mailing address of the ISA / AU AUSTRALIAN PATENT OFFICE PO BOX 200, WODEN ACТ 2606, AUSTRALIA Email address: pct@ipaustralia.gov.au Form PCT / ISA / 210 (fifth sheet) (July 2019) "ד ☑ See patent family annex later document published after the international filing date or priority date and not in conflict with the application but cited to understand the principle or theory underlying the invention "X" document of particular relevance; the claimed invention cannot be considered novel or cannot be considered to involve an inventive step when the document is taken alone "" document of particular relevance; the claimed invention cannot be considered to involve an inventive step when the document is combined with one or more other such documents, such combination being obvious to a person skilled in the art document member of the same patent family Date of mailing of the international search report 17 January 2025 Authorised officerSue Christie AUSTRALIAN PATENT OFFICE (ISO 9001 Quality Certified Service) Telephone No. +61 2 6283 7978 INTERNATIONAL SEARCH REPORT C (Continuation). DOCUMENTS CONSIDERED TO BE RELEVANT International application No. PCT / IB2024 / 060167 Category* Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No. US 2022 / 0225934 A1 (WEAR2B LTD) 21 July 2022 X Figs. 1 and 3;

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[0072] . 1-4 US 2023 / 0098937 A1 (TALLINN UNIVERSITY OF TECHNOLOGY) 30 March 2023 A WHOLE DOCUMENT 1-4 US 2017 / 0347957 A1 (KONINKLIJKE PHILIPS N. V.) 07 December 2017 A WHOLE DOCUMENT 1-4 Form PCT / ISA / 210 (fifth sheet) (July 2019) INTERNATIONAL SEARCH REPORT Information on patentfamily members International application No. PCT / IB2024 / 060167 This Annex lists known patent family members relating to the patent documents cited in the above-mentioned international search report. The Australian Patent Office is in no way liable for these particulars which are merely given for the purpose of information. Patent Document / s Cited in Search Report Patent Family Member / s Publication Number Publication Date Publication Number Publication Date US 2022 / 0225934 A1 21 July 2022 US 2022225934 A1 21 Jul 2022 CN 113993448 A 28 Jan 2022 EP 3975831 Al 06 Apr 2022 JP 2022534604 A 02 Aug 2022 KR 20220012934 A 04 Feb 2022 WO 2020240552 A1 03 Dec 2020 US 11504017 B2 22 November 2022 US 2020288999 A1 17 Sep 2020 US 11504017 B2 22 Nov 2022 EP 3225156 A1 04 Oct 2017 EP 3225156 B1 05 Jan 2022 JP 2019509120 A 04 Apr 2019 JP 6858789 B2 14 Apr 2021 PH 12018501658 A1 03 Jun 2019 WO 2017168041 A1 05 Oct 2017 US 2018 / 0035943 A1 08 February 2018 US 2018035943 A1 08 Feb 2018 US 10736570 B2 11 Aug2020 US 2018146870A1 31 May 2018 US 10849513 B2 01 Dec 2020 US 2021076957 A1 18 Mar 2021 US 11911137 B2 27 Feb 2024 US 2017020399 A1 26 Jan 2017 US 2024156362 A1 16 May 2024 WO 2018025199 A1 08 Feb 2018 US 2007 / 0078316 A1 05 April 2007 US 2007078316 A1 05 Apr 2007 US 7483731 B2 27 Jan 2009 TW 200726443 А 16 Jul 2007 US 2009118598 A1 07 May 2009 US 8352009 B2 08 Jan 2013 WO 2007041330 A1 12 Apr 2007 US 2023 / 0172471 A1 08 June 2023 US 2023172471 A1 08 Jun 2023 US 11857303 B2 02 Jan 2024 CA 3238042 A1 15 Jun 2023 CN 118284363 A 02 Jul 2024 EP 4444175 A1 16 Oct 2024 WO 2023107483 Al 15 Jun 2023 Due to data integration issues this family listing may not include 10 digit Australian applications filed since May 2001. Form PCT / ISA / 210 (Family Annex) (July 2019) INTERNATIONAL SEARCH REPORT Information on patent family members International application No. PCT / IB2024 / 060167 This Annex lists known patent family members relating to the patent documents cited in the above-mentioned internationalsearch report. The Australian Patent Office is in no way liable for these particulars which are merely given for the purpose of information. Patent Document / s Cited in Search Report Patent Family Member / s Publication Number Publication Date Publication Number Publication Date WO 2009 / 032074 A1 12 March 2009 WO 2009032074 A1 12 Mar 2009 WO 2009032073 Al 12 Mar 2009 US 2021 / 0145363 A1 20 May 2021 US 2021145363 A1 20 May 2021 CN 112469327 A 09 Mar 2021 EP 3809951 Al 28 Apr 2021 EP 3809951 B1 31 Jul 2024 WO 2019243629 A1 26 Dec 2019 US 2022 / 0167889 A1 02 June 2022 US 2022167889 A1 02 Jun 2022 US 2013 / 0296714 A1 22 August 2013 US 2013296714 A1 07 Nov 2013 US 9289177 B2 22 Mar 2016 AU 2012207635 A1 02 May 2013 AU 2012207635 B2 16 Jul 2015 CA 2815643 A 26 Jul 2012 CN 103228205 A 31 Jul 2013 CN 103228205 B 30 Sep 2015 CN 103327886 A 25 Sep 2013 CN 103327886 В 22 Jun 2016 CN 103384493 A 06 Nov 2013 CN 103384493 B 15 Feb 2017 EP 2632326 A1 04 Sep 2013 EP 2665409 A1 27 Nov 2013 EP 3127478 A1 08Feb 2017 EP 3127478 B1 09 Jun 2021 JP 2014507209 A 27 Mar 2014 JP 5771288 B2 26 Aug 2015 SG 189431 A1 31 May 2013 SG 189432 A1 31 May 2013 SG 189433 A1 31 May 2013 SG 189912 A1 28 Jun 2013 SG 189913 A1 28 Jun 2013 SG 190397 A1 28 Jun 2013 US 2012190944 A1 26 Jul 2012 US 8761853 B2 24 Jun 2014 US 2013289366 A1 31 Oct 2013 US 9232915 B2 12 Jan 2016 Due to data integration issues this family listing may not include 10 digit Australian applications filed since May 2001. Form PCT / ISA / 210 (Family Annex)(July 2019) INTERNATIONAL SEARCH REPORT Information on patent family members International application No. PCT / IB2024 / 060167 This Annex lists known patent family members relating to the patent documents cited in the above-mentioned international search report. The Australian Patent Office is in no way liable for these particulars which are merely given for the purpose of information. Patent Document / s Cited in Search Report Patent Family Member / s Publication Number Publication Date PublicationNumber Publication Date US 2013296665 A1 07 Nov 2013 US 9072439 B2 07 Jul 2015 US 2013296666 A1 07 Nov 2013 US 9480407 B2 01 Nov 2016 US 2013296673 A1 07 Nov 2013 US 9538927 B2 10 Jan 2017 WO 2012099534 A2 26 Jul 2012 WO 2012099535 A1 26 Jul 2012 WO 2012099536 A1 26 Jul 2012 WO 2012099537 A1 26 Jul 2012 WO 2012099538 A1 26 Jul 2012 WO 2012099539 A1 26 Jul 2012 US 2023 / 0098937 A1 30 March 2023 US 2023098937 A1 30 Mar 2023 EP 4114250 A1 11 Jan 2023 WO 2021176358 A1 10 Sep 2021 US 2017 / 0347957 A1 07 December 2017 US 2017347957 A1 07 Dec 2017 US 10575780 B2 03 Mar 2020 BR 112017012758 A2 26 Dec 2017 CN 106999058 A 01 Aug 2017 CN 106999058 В 13 Apr 2021 EP 3232904 A1 25 Oct 2017 JP 2018504171 A 15 Feb 2018 JP 6684282 B2 22 Apr 2020 RU 2017125449A 23 Jan 2019 WO 2016096391 A1 23 Jun 2016 WO 2016097271 A2 23 Jun 2016 End of Annex Due to data integration issues this family listing may not include 10 digit Australian applications filed since May 2001. Form PCT / ISA / 210 (Family Annex)(July 2019)(19) State Intellectual Property Office (12) Invention Patent Application (10) Application Publication Number (43) Application Publication Date (21) Application Number 202480066588.2 (22) Application Date 2024.10.17 (30) Priority Data 2023903337 2023.10.19 AU (85) PCT International Application Entering National Phase Date 2026.04.16 (86) PCT International Application Application Data PCT / IB2024 / 060167 2024.10.17 (87) PCT International Application Publication Data WO2025 / 083590 EN 2025.04.24 (71) Applicant Compmedix Medical Innovation Pte Ltd Address Victoria, Australia (72) Inventor B. Ali Ahmad (74) Patent Agency Guangzhou Jiaquan Patent & Trademark Agency Co., Ltd. 44205 Patent Attorney Wu Zhijian (51) Int.Cl. A61B 5 / 00 (2006.01) A61B 5 / 024 (2006.01) A61B 5 / 0295 (2006.01) A61B 5 / 1455 (2006.01) (54) Invention Title Apparatus for Monitoring Physiological Signals (57) Abstract This invention relates to design improvements for reflective and transmissive photoplethysmography (PPG) devices to reduce motion artifacts, avoid spurious and non-physiological baseline drift in the signal, and improve signal quality and the accuracy of various indicators derived from PPG. This invention improves the accuracy of all PPG-driven parameter estimations, such as continuous measurements of blood oxygen saturation (SpO2), heart rate, heart rate variability, respiratory rate, blood pressure, and arterial pulse wave volume (i.e., peripheral arterial tension measurement and arterial pulse tension measurement). This invention also incorporates the ability to measure and / or track and / or compensate for changes or absolute values ​​of pressure applied between a sensor and the surface of a biological subject, an ability applicable to all sensors or related probes. Claims 1 page, Description 3 pages, Drawings 2 pages. CN 122055095 A 2026.05.15 CN 1 22 05 50 95 A 1. An apparatus for monitoring physiological signals of a subject, comprising: a) a flexible substrate for attachment to the skin of a subject; b) at least one sensor coupled to said flexible substrate for monitoring physiological signals of said subject; c) a sensor coupled to said flexible substrate for measuring blood oxygen concentration; and d) a floating or elastically supported optical sensor coupled to said flexible substrate for mechanically adjusting contact pressure and ensuring that vasoconstriction caused by the application of the sensor is always controlled, limited, and / or minimized.2. The device according to claim 1, wherein the flexible substrate comprises a flexible pressure-sensitive material. 3. The device according to claim 1 or 2, further comprising a microprocessor programmed with an algorithm for automatically and in real-time optimizing the monitored signal and adjusting the derived index according to the measured contact pressure. 4. The device according to any one of claims 1 to 3, further comprising a microprocessor programmed to calculate and / or track and / or compensate for changes or absolute values ​​of pressure applied between the sensor and the subject surface. Claims 1 / 1 page 2 CN 122055095 A Device for Monitoring Physiological Signals Technical Field

[0001] The present invention relates to a device for acquiring electrophysiological signals related to physiological processes, and more particularly to a device for measuring hemoglobin oxygen saturation (SpO2). Background Art

[0002] Photoplethysmography (PPG) is a non-invasive technique used to transcutaneously measure the oxygen saturation (SpO2) of hemoglobin in arterial blood and to extract valuable information such as heart rate, respiratory rate and respiratory frequency derived from PPG, arterial tension, and pulse wave volume. This technique is non-invasive and relies on two light-emitting diodes (LEDs): a red LED and a near-infrared (N-IR) LED, and a photodetector.

[0003] The main principle of measuring SpO2 using PPG signals is that oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb) have significantly different absorption rates for red and near-infrared light. Compared to HbO2, Hb absorbs more red light and less near-infrared (N-IR) light. In other words, compared to HbO2, Hb reflects less red light and more near-infrared light. Based on this characteristic, two types of pulse oximeters have been developed: (i) transmissive pulse oximeters and (ii) reflective pulse oximeters.

[0004] In a transmissive pulse oximeter, the photodiode and detector are respectively positioned on opposite sides of the measurement site, such as the fingertip, and the receiver detects the amount of light transmitted through the tissue; while in a reflective pulse oximeter, the light source and detector are both positioned on the same side of the measurement site, and the measurement is performed by capturing the amount of light reflected back from the tissue. In both cases, the amount of absorbed or reflected light fluctuates due to: (i) changes in arterial blood volume during the systolic and diastolic phases of the cardiac cycle; and (ii) changes in blood oxygen concentration.

[0005] By comparing the relative proportions of red light and near-infrared light absorption, changes caused by the cardiac cycle and changes caused by changes in blood oxygen concentration can be distinguished.

[0006] The measurement accuracy of transmissive and reflective PPG devices is easily affected by movement and contact between the sensor and the skin.The effects of pressure variations. For PPG devices to operate reliably, stable contact pressure is required, but this is not easily achieved because pressure can change as the patient moves, especially with significant movement. Insufficient contact pressure leads to severe light leakage, resulting in a weak and noisy PPG signal. Conversely, excessive pressure causes vasoconstriction, temporarily reducing or blocking blood perfusion and altering the morphology of the PPG signal.

[0007] In both cases, suboptimal contact pressure alters the morphology of the PPG signal (i.e., red and infrared signals) and the relative intensity of red and near-infrared light absorption / reflection, significantly reducing the accuracy of all PPG-driven signals (including but not limited to SpO2) and causing baseline shifts. This problem is particularly pronounced when continuous monitoring over extended periods is required, such as during overnight sleep studies, as contact pressure can change due to positional variations during sleep. This can introduce bias in the diagnosis of certain medical conditions, such as cardiopulmonary complications, sleep apnea, chronic obstructive pulmonary disease (COPD), and heart failure. Suboptimal contact pressure can also lead to more severe motion artifact contamination of PPG signals, reduced signal-to-noise ratio, PPG baseline drift, and unreliable or erroneous heart rate measurements.

[0008] Therefore, an improved PPG device design is needed to minimize the above problems and provide a better measurement signal. Specification 1 / 3 page 3 CN 122055095 A Summary of the Invention

[0009] The present invention provides an apparatus for improving the measurement of biological signals (especially photoplethysmography signals) of a subject. In one aspect, the present invention provides an apparatus for monitoring physiological signals of a subject, the apparatus comprising: a flexible substrate for attachment to the subject's skin, at least one sensor for monitoring the subject's physiological signals, a sensor for measuring blood oxygen concentration, and a floating or elastically supported optical sensor for mechanically adjusting the contact pressure and ensuring that vasoconstriction caused by the application of the sensor is always controlled, limited, and / or minimized.

[0010] The present invention advantageously provides a mechanism for measuring the pressure applied by a flexible substrate relative to skin, limbs, or other body surface areas. Preferably, the flexible substrate comprises a flexible pressure-sensitive material. Preferably, the invention incorporates an algorithm for automatically and in real-time optimization of the signal based on the measured contact pressure, and adjustment of the derived indices. Preferably, the invention also incorporates the ability to measure and / or track and / or compensate for changes in applied pressure or its absolute value between the sensor and the subject's surface, a capability applicable to all sensors or associated probes. Preferably, one or more applied sensors or probes can be deployed to achieve the above functions. Preferably, the measurement results from the sensor...The result or output can be modified, adjusted, compensated, or calculated in the relevant algorithm or any form of relevant calculation, taking the "pressure applied between the sensor and the subject's surface" as a parameter.

[0011] Figure 1 is a side view of an embodiment of the present invention, which includes a reflective pulse oximeter equipped with a pressure-sensitive material or pressure sensor.

[0012] Figure 2 is a side view of an embodiment of the present invention, which includes a transmissive finger clip pulse oximeter equipped with a pressure-sensitive material or pressure sensor, showing a finger inserted into the finger clip.

[0013] The present invention relates to improvements in the design of reflective and transmissive photoplethysmography (PPG) devices to reduce motion artifacts, avoid spurious and non-physiological baseline drift in the signal, and improve signal quality and the accuracy of various indicators derived from PPG. This invention improves the accuracy of estimations of all PPG-driven parameters, such as oxygen saturation (SpO2), heart rate, heart rate variability, respiratory rate, blood pressure, and continuous measurement of arterial pulse wave volume (i.e., peripheral arterial tension measurement and arterial pulse tension measurement).

[0014] This invention also incorporates the ability to measure and / or track and / or compensate for changes in or the absolute value of pressure applied between the sensor and the surface of a biological subject, applicable to all sensors or associated probes.

[0015] This invention particularly advantageously introduces a mechanism for pulse oximeters to continuously monitor the contact pressure between the skin and the sensor and to adjust / optimize the signal based on this contact pressure. This invention employs a floating or elastically supported optical sensor to mechanically regulate the contact pressure and ensure that vasoconstriction caused by the application of the sensor is always controlled, limited, and / or minimized.

[0016] Furthermore, this invention advantageously provides a mechanism for measuring the pressure applied to a flexible substrate relative to the skin, limb, or other body surface. The present invention can also incorporate an algorithm for automatically and in real-time optimization of the signal based on the measured contact pressure, and adjustment of the resulting indices.

[0017] The present invention can also modify, adjust, compensate, or calculate the measurement results or outputs from the sensor in a related algorithm or any form of related calculation, using the pressure applied between the sensor and the surface of the biological subject as a parameter.

[0018] The present invention can also help distinguish between cases of blood flow restriction (i.e., vasoconstriction) due to natural hypoperfusion and cases of blood flow restriction due to increased contact pressure. Furthermore, the present invention is advantageous in distinguishing between a true low SpO2 baseline (e.g., caused by conditions such as chronic obstructive pulmonary disease) and a pseudo-low baseline caused by imperfect contact pressure between the skin and the sensor.

[0019] The application of this invention is not limited to translucent body parts such as fingers, toes, and earlobes, where only transmissive optical sensors can be used. This invention expands the range of selectable measurement sites, providing more possibilities for developing wearable devices with clinical-grade accuracy, such as smartwatches, forehead-worn, and chest-worn PPG monitoring devices.

[0020] Preferably, this invention employs a flexible pressure-sensitive material, such as “Velostat” or “Linqstat,” and / or an electronic pressure sensor, combined with a spring-loaded optical sensor. The optical sensor is mounted on a spring of known type and specifications, which can be made in any form, such as a helical spring or a folded metal structure, to adjust its contact pressure relative to any part of the body. The addition of a pressure sensor (or pressure-sensitive material) to the spring-loaded optical sensor enables real-time measurement of pressure signals related to the integrity of the connection between the skin and the sensor.

[0021] The accompanying drawings illustrate preferred embodiments of the invention. Those skilled in the art will understand that other embodiments may exist within the scope of the claims.

[0022] Referring now to FIG1, an embodiment of a reflective PPG device according to the invention is shown, which includes pulse oximetry and is disposed on the skin 1 (i.e., the measurement site). Depending on the location of the measurement site, the device includes a strip structure or adhesive patch 2 to hold the device in place. A transmitter 3 and a receiver 10 are both mounted on a rigid substrate 15, which is connected to a main rigid substrate 5 via two flexible substrates 9 and 18. These two flexible substrates are used to transmit electrical signals from 15 to 16, and then via a third flexible substrate 19 to the main rigid substrate 5 containing all electronic components 4.

[0023] A pressure-sensitive material or pressure sensor 7 is disposed between the two rigid substrates 5 and 16 for detecting contact pressure. A helical spring 6 and a metal rod 12 for housing the spring are disposed between substrates 15 and 16. This structure allows the sensor and lens to move within a plastic housing 8, thereby providing the ability to absorb and release energy and providing cushioning, while also helping to adjust the contact force according to the shape of the measurement site.

[0024] The transmitter 3 and receiver 10 are covered by a plastic housing 15, which has two openings above the two sensors respectively. These openings are used to mount optical lenses 11 and 17 to conduct light, and a U-shaped optical isolator 13 is provided between them to prevent light leakage between the transmitter 3 and receiver 10. The isolator has a U-shaped structure to accommodate the metal rod 12 when the spring 6 is compressed.

[0025] Referring now to FIG2, another embodiment of the invention is shown, namely a transmissive PPG finger clip probe, showing a finger 1 inserted into the finger clip. The device includes an upper housing 4 and a lower housing 9, which are connected by a spring 7.Connection. The lower housing 9 houses the receiver 11, which is mounted on a rigid base 10, which in turn is mounted on a pressure-sensitive material 8. The upper housing 4 houses the transmitter 3, which is mounted on a rigid base 5. All electronic components 2 are mounted on the other side of the rigid base 5.

[0026] A silicone pad 6 is provided inside the opening of the device, which can conform to the shape of the finger 1 and help adjust the contact force between the finger 1 and the transmitter 3 and the receiver 11. The silicone pad can also provide optical isolation and prevent light from leaking from the transmitter 3 to the receiver 11. Specification 3 / 3 page 5 CN 122055095 A Figure 1 Specification Figure 1 / 2 page 6 CN 122055095 A Figure 2 Specification Figure 2 / 2 page 7 CN 122055095 A

Claims

1. A device for monitoring physiological signals of a subject, comprising: a) A flexible substrate for attaching to the subject's skin; b) At least one sensor attached to the flexible substrate for monitoring the physiological signals of the subject; c) A sensor coupled to the flexible substrate for measuring the oxygen concentration in blood; as well as d) A floating or elastically supported optical sensor, which is combined with the flexible substrate, for mechanically adjusting the contact pressure and ensuring that vasoconstriction caused by the application of the sensor is always controlled, limited and / or minimized.

2. The device according to claim 1, wherein the flexible substrate comprises a flexible pressure-sensitive material.

3. The apparatus according to claim 1 or 2 further includes a microprocessor programmed with an algorithm for automatically and in real-time optimizing the monitored signal and adjusting the derived parameters based on the measured contact pressure.

4. The apparatus according to any one of claims 1 to 3, further comprising a microprocessor programmed to calculate and / or track and / or compensate for changes or absolute values ​​of pressure applied between the sensor and the subject surface.

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