# US 2024/0188903 A1 · System and method of measuring venous oxygen saturation using intelligent pulse averaging with integrated ekg and ppg sensors

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- Number: US 2024/0188903 A1
- Document ID: US20240188903A1
- Status: Published application
- Kind: A1
- Application number: 18/429,323
- Filed: 2024-01-31
- Published: 2024-06-13
- Earliest claimed: 2020-04-14
- Assignees: Hemocept Inc.
- Applicants: Hemocept Inc.
- Inventors: Eric Raman; Kevin Peterson; Iain Hueton
- Web page: https://patentgrep.com/patent/US20240188903A1

## CPC

- A61B 5/7285: {for synchronizing or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal}
- A61B 5/0006: {ECG or EEG signals}
- A61B 5/0036: {including treatment, e.g., using an implantable medical device, ablating, ventilating}
- A61B 5/004: {adapted for image acquisition of a particular organ or body part (A61B5/0082 takes precedence; arrangements for optical scanning A61B5/0062)}
- A61B 5/0205: Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
- A61B 5/02125: {of pulse wave propagation time}
- A61B 5/024: Measuring pulse rate or heart rate
- A61B 5/02416: {using photoplethysmograph signals, e.g. generated by infrared radiation (A61B5/14552 takes precedence)}
- A61B 5/02438: {with portable devices, e.g. worn by the patient}
- A61B 5/14: {Devices for taking samples of blood (hypodermic syringes A61M5/00); Measuring characteristics of blood in vivo, e.g. gas concentration within the blood, pH-value of blood (measuring of blood pressure A61B5/02; non-radiation detecting or locating of foreign bodies in blood A61B5/06)}
- A61B 5/14551: {for measuring blood gases}
- A61B 5/14552: {Details of sensors specially adapted therefor}
- A61B 5/256: Wearable electrodes, e.g. having straps or bands
- A61B 5/282: Holders for multiple electrodes (for introduction into the body A61B5/287)
- A61B 5/349: Detecting specific parameters of the electrocardiograph cycle
- A61B 5/352: Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
- A61B 5/366: Detecting abnormal QRS complex, e.g. widening
- A61B 5/4839: {combined with drug delivery}
- A61B 5/4875: {Hydration status, fluid retention of the body}
- A61B 5/6823: {Trunk, e.g., chest, back, abdomen, hip}
- A61B 5/6831: {Straps, bands or harnesses}
- A61B 5/6833: {Adhesive patches}
- G16H 40/63: for local operation
- A61B 5/02427: {Details of sensor}
- A61B 5/0245: by using sensing means generating electric signals, {i.e. ECG signals}
- A61B 2560/0223: of calibration, e.g. protocols for calibrating sensors
- A61B 2562/146: for optical coupling
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- G16H: HEALTHCARE INFORMATICS, i.e. INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR THE HANDLING OR PROCESSING OF MEDICAL OR HEALTHCARE DATA

## Abstract

A system using combined electrocardiography (EKG) and photoplethysmography (PPG) sensing, to determine venous oxygen saturation is described. The system uses averaging of similar pulses based on Prior (or n−1) R-to-R pulse wave duration, and current (or n) R-to-R pulse wave duration for evaluation of the metabolic reserve and/or stress of the patient.

## Claims

### Claim 1

A computer logic system for determining venous oxygen saturation, the computer logic system configured to:
obtain (a) a PPG signal from a device that includes at least one PPG sensor mounted thereon for measuring the person's PPG signal at multiple wavelengths of light, and (b) an EKG signal from a plurality of electrodes coupled to a person;
identify cardiac cycles in the EKG signal;
segment the PPG signal into a series of PPG signal segments based upon features in the identified cardiac cycles,
sort the PPG signal segments into a plurality of bins based upon a similarity in durations of prior R-to-R cardiac cycles and a similarity in durations of current R-to-R cardiac cycles,
generate a composite signal for each of the plurality of bins,
generate a composite Signal Prime Over Signal (SPOS) for each of the composite signals by calculating a derivative of the composite signal and normalizing the derivative of the composite signal by the composite signal itself, and
measure venous oxygen saturation of the person by:
(a) calculating arterial oxygen saturation by comparing the composite SPOS signals measured at different wavelengths of light,
(b) sub-sampling composite signals at two consecutive signal maxima measured at different wavelengths of light, and
(c) comparing the sub-sampled composite SPOS signals measured at different wavelengths of light to the calculated arterial oxygen saturation to determine venous oxygen saturation.

### Claim 2 (depends on 1)

The system of claim 1, wherein to measure venous oxygen saturation of the person, the computer logic system is configured to select preferred bins from which the composite signals are used when determining the venous oxygen saturation.

### Claim 3 (depends on 2)

The system of claim 2, wherein the preferred bins correspond to the bins having the largest number of PPG signal segments therein.

### Claim 4 (depends on 3)

The system of claim 3, wherein the preferred bins correspond to the bins having the largest difference between current and prior R-to-R values.

### Claim 5 (depends on 1)

The system of claim 1, wherein to generate a composite signal for each bin, the computer logic system is configured to sum or average the PPG signal segments in the bin.

### Claim 6 (depends on 1)

The system of claim 1, wherein to generate a composite signal for each of the plurality of bins, the computer logic system is configured to remove aberrant PPG signal segments from the calculation of the composite signal.

### Claim 7 (depends on 6)

The system of claim 6, wherein to remove aberrant PPG signal segments from the calculation of the composite signal, the computer logic system is configured to iteratively recalculate the composite signal, by:
comparing a SPOS of each of the PPG signal segments used to calculate a composite signal against the SPOS of the calculated composite signal,
removing outlier PPG signal segments,
re-calculating the composite signal with the outlier PPG signal segments removed, and
repeating the iteration until there are no more outlier PPG signal segments.

### Claim 8 (depends on 1)

The system of claim 1, wherein the at least one PPG sensor is mounted to a handheld device that includes a plurality of electrode wires extending therefrom.

### Claim 9 (depends on 8)

The system of claim 8, wherein the device is a hand-held device with the at least one PPG sensor mounted thereon and at least one of the plurality of electrodes mounted thereon.

### Claim 10 (depends on 8)

The system of claim 8, wherein an optical waveguide is interposed between the at least one PPG sensor and the skin of the person.

### Claim 11 (depends on 1)

The system of claim 1, wherein the at least one PPG sensor and the plurality of electrodes are disposed within a strap or band disposed around the chest or limb of the person.

### Claim 12 (depends on 1)

The system of claim 1, wherein the at least one PPG sensor and at least one of the plurality of electrodes are positioned within a patch.

### Claim 13 (depends on 1)

The system of claim 1, wherein the computer logic system is positioned within a device that includes the at least one PPG sensor and the plurality of electrodes, and wherein the device comprises:
a data transmission system for transmitting one or both of:
the composite signals to a remote computer system for analysis, or
measured PPG and EKG signals to a remote computer system for analysis.

### Claim 14

A method for determining venous oxygen saturation comprising:
obtaining, via a computer logic system, (a) a PPG signal from a device that includes at least one PPG sensor mounted thereon for measuring the person's PPG signal at multiple wavelengths of light, and (b) an EKG signal from a plurality of electrodes coupled to a person;
identifying, via the computer logic system, cardiac cycles in the EKG signal;
segmenting, via the computer logic system, the PPG signal into a series of PPG signal segments based upon features in the identified cardiac cycles,
sorting, via the computer logic system, the PPG signal segments into a plurality of bins based upon a similarity in durations of prior R-to-R cardiac cycles and a similarity in durations of current R-to-R cardiac cycles,
generating, via the computer logic system, a composite signal for each of the plurality of bins,
generating, via the computer logic system, a composite Signal Prime Over Signal (SPOS) for each of the composite signals by calculating a derivative of the composite signal and normalizing the derivative of the composite signal by the composite signal itself, and
measuring, via the computer logic system, venous oxygen saturation of the person by:
(a) calculating arterial oxygen saturation by comparing the composite SPOS signals measured at different wavelengths of light,
(b) sub-sampling composite signals at two consecutive signal maxima measured at different wavelengths of light, and
(c) comparing the sub-sampled composite SPOS signals measured at different wavelengths of light to the calculated arterial oxygen saturation to determine venous oxygen saturation.