Sensor characterization through forward voltage measurement

Abstract

This invention discloses an apparatus for measuring oxygen saturation. The apparatus includes a circuit system configured to: measure a first diode voltage at a light-emitting diode (LED) when a first current is applied through the LED; measure a second diode voltage at the LED when a second current is applied through the LED; and measure a third diode voltage at the LED when a third current is applied through the LED. The circuit system is further configured to: determine a series resistance based on the first, second, and third diode voltages; and determine the intensity of a received photon signal corresponding to an output photon signal generated using the LED. The circuit system is further configured to determine the oxygen saturation level based on the intensity of the received photon signal and the series resistance.

Description

[0001] This application claims priority to U.S. Patent Application No. 16 / 857,849, filed April 24, 2020, entitled “Sensor Characterization Through Forward Voltage Measurements,” and U.S. Patent Application No. 17 / 082,958, filed October 28, 2020, entitled “Sensor Characterization Through Forward Voltage Measurements,” the entire contents of each of these patent applications are incorporated herein by reference. Technical Field

[0002] This disclosure relates to determining blood oxygen saturation using a physiological monitor, and more specifically, to determining regional blood oxygen saturation using a regional pulse oximeter or other medical device. Background Technology

[0003] A pulse oximeter outputs a small beam of light through the blood and measures the absorption of that beam to estimate the oxygen saturation level in the blood. For example, blood with relatively high oxygen saturation absorbs more light at a specific wavelength than blood with relatively low oxygen saturation. Therefore, a pulse oximeter can determine that the oxygen saturation level in the blood increases as less light at a specific wavelength is received after passing through the blood. Summary of the Invention

[0004] Generally, this disclosure relates to apparatus, systems, and techniques for determining the properties of a sensor device in a pulse oximeter by measuring a forward voltage. For example, an apparatus can measure the diode voltage at a light-emitting diode (LED) when different currents are applied. The apparatus can use this diode voltage to determine the resistance of the LED. In this example, the apparatus can compensate for resistive effects (e.g., from cables, connectors, circuit board traces, etc.) to determine the “true” forward voltage at the LED to help ensure the correct construction and / or accuracy of the sensor device. For example, the apparatus can verify whether the LED corresponds to the LED used during calibration based on series resistance, forward voltage, etc. In this way, the apparatus can be verified with calibration values ​​to help ensure the correct construction and / or accuracy of the sensor device. In some examples, the apparatus can verify whether the LED is operating within a temperature range, take into account wavelength shifts in the light emitted by the LED, and / or use the forward voltage at the LED to improve other characteristics of the apparatus.

[0005] In one example, an apparatus for measuring oxygen saturation includes a circuit system configured to: measure a first diode voltage at the light-emitting diode when a first current is applied through the light-emitting diode; measure a second diode voltage at the light-emitting diode when a second current is applied through the light-emitting diode; measure a third diode voltage at the light-emitting diode when a third current is applied through the light-emitting diode; determine a series resistance of the light-emitting diode based on the first diode voltage, the second diode voltage, and the third diode voltage; determine the intensity of a received photon signal corresponding to an output photon signal output using the light-emitting diode; determine an oxygen saturation level based on the intensity of the received photon signal and the series resistance; and output an indication of the oxygen saturation level.

[0006] In another example, a method for measuring oxygen saturation includes: measuring a first diode voltage at the light-emitting diode by a circuit system when a first current is applied through the light-emitting diode; measuring a second diode voltage at the light-emitting diode by the circuit system when a second current is applied through the light-emitting diode; measuring a third diode voltage at the light-emitting diode by the circuit system when a third current is applied through the light-emitting diode; determining a series resistance of the light-emitting diode by the circuit system based on the first diode voltage, the second diode voltage, and the third diode voltage; determining an intensity of a received photon signal corresponding to an output photon signal output using the light-emitting diode by the circuit system; determining an oxygen saturation level by the circuit system based on the intensity of the received photon signal and the series resistance; and outputting an indication of the oxygen saturation level by the circuit system.

[0007] In one example, a system for measuring oxygen saturation includes: a sensor device including a light-emitting diode (LED); a blood oxygen measuring device including a circuit system configured to: measure a first diode voltage at the LED when a first current is applied through the LED; measure a second diode voltage at the LED when a second current is applied through the LED; measure a third diode voltage at the LED when a third current is applied through the LED; determine a series resistance of the LED based on the first, second, and third diode voltages; determine the intensity of a received photon signal corresponding to an output photon signal output using the LED; determine an oxygen saturation level based on the intensity of the received photon signal and the series resistance; and output an indication of the oxygen saturation level. Attached Figure Description

[0008] Figure 1 This is a conceptual block diagram illustrating an exemplary regional blood oxygen measurement device.

[0009] Figure 2 This is a conceptual block diagram illustrating an exemplary regional blood oxygenation measuring device configured to monitor a patient's self-regulating state.

[0010] Figure 3 This is a conceptual diagram illustrating an exemplary graphical user interface that includes self-adjusting information presented on a display.

[0011] Figure 4 This is a conceptual diagram illustrating an exemplary resistor of a light-emitting diode of a first sensor device according to the technology described herein.

[0012] Figure 5 This is a conceptual diagram illustrating an exemplary second sensor device according to the technology described herein.

[0013] Figure 6 This is a flowchart illustrating an exemplary technique for measuring oxygen saturation, based on the techniques described herein. Detailed Implementation

[0014] A pulse oximeter can refer to a medical device configured to determine the oxygen saturation of an analyzed tissue. For the purposes of this disclosure, a pulse oximeter can be defined as a device that measures elements other than oxygen content. For example, a pulse oximeter may measure other properties and chemical compositions of blood, such as carbon monoxide. In other cases, a pulse oximeter may be used solely to measure a subject's photoplethysmography to determine pulse rate. Examples of pulse oximeters may include, for example, a pulse oximeter, a zone oximeter, a CO oximeter, or another type of oximeter. A pulse oximeter may be configured to estimate the oxygen saturation of blood. A zone oximeter may be configured to estimate the oxygen saturation of a region of tissue in a subject (e.g., a human patient). For example, a zone oximeter may be configured to estimate the regional oxygen saturation of hemoglobin in a region of the subject's tissue by determining the differential absorption value of each of two or more wavelengths of light received at two different locations on the subject's body. For each wavelength of light, the zone oximeter may compare the amount of light absorbed by the subject's tissue in a first region with the amount of light absorbed by the subject's tissue in a second region to obtain a differential absorption value. Sensor devices may include regional pulse oximeters and pulse oximeters.

[0015] Pulse oximeters (e.g., pulse oximeters, zone oximeters, CO oximeters, etc.) may include sensor devices placed on a part of the patient's body, such as on the fingertips, toes, forehead, or earlobe, or, in the case of newborns, on the foot, hand, or another location. Pulse oximeters may use a light source to pass light through blood-perfused tissue and photoelectrically sense the absorption of light in that tissue. Other suitable sensor locations may include, for example, the neck for monitoring carotid artery pulsation flow, the wrist for monitoring radial artery pulsation flow, the inner thigh for monitoring femoral artery pulsation flow, the ankle for monitoring tibial artery pulsation flow, around or in front of the ear, the cerebral cortex, locations with strong pulsating arterial flow, or other locations.

[0016] A pulse oximeter can be configured to output a photon signal that interacts with tissue at one or more wavelengths, attenuated by blood in an amount representing the concentration of blood components. The pulse oximeter can be configured to generate photon signals at red and infrared (IR) wavelengths. The pulse oximeter can estimate the oxygen saturation of hemoglobin in arterial blood based on the intensity of the photon signals at red wavelengths and infrared wavelengths. While the various examples described herein refer to LEDs that can output relatively low-intensity light, in some examples, the LED may include a device that outputs a relatively strong beam of infrared radiation (e.g., a laser diode), a vertical-cavity surface-emitting laser, or another device that uses at least one p-junction and at least one n-junction to emit light. Furthermore, while the examples described herein may refer to devices that emit light (e.g., LEDs, laser diodes, etc.), similar techniques can be used with devices that receive light (e.g., photodiodes).

[0017] A pulse oximeter's light-emitting diode (LED) may have characteristics that affect the wavelength of the emitted light. For example, a pulse oximeter may estimate the wavelength of light emitted by the LED based on the diode voltage measured at the LED. The diode voltage may include the "true" forward voltage at the LED and other voltages as a result of the current flowing through the series resistance of the LED. This series resistance may include resistance from cables, external cables, connectors, traces, and other resistors in series with the LED. For example, a pulse oximeter may measure the diode voltage across the positive and negative terminals of the pulse oximeter, where current flows from the positive terminal through one or more cables (e.g., cables, extension cables, etc.) to the LED and from the LED through one or more cables to the negative terminal. However, the "true" forward voltage at the LED may be difficult to measure accurately. For example, changing the cable used to connect the pulse oximeter device to the sensor device (e.g., from a 6-foot cable to a 10-foot cable) can significantly change the measured diode voltage, which may cause errors in the estimated forward voltage. Furthermore, the forward voltage can vary with different currents (see Equation 4), which may lead to inaccurate methods that use Ohm's law and assume a constant true forward voltage. Therefore, characteristics of the light-emitting diode (such as, for example, but not limited to, the temperature at the light-emitting diode, the wavelength of the light emitted by the light-emitting diode, and other characteristics that can be used to verify that the LED used by the device is correct and compatible with the device and / or to improve the performance of the pulse oximeter) may not be applicable to the pulse oximeter.

[0018] According to the technology of this disclosure, an apparatus (e.g., a pulse oximeter) can be configured to take into account the series resistance of a light-emitting diode (LED). For example, the apparatus can measure a first diode voltage at the LED in response to a first current used to measure oxygen saturation. In this example, the apparatus can measure a second diode voltage at the LED in response to a second current with an amplitude twice that of the first current. Additionally, the apparatus can measure a third diode voltage at the LED in response to a third current with an amplitude twice that of the second current. The apparatus can use the first diode voltage, the second diode voltage, and the third diode voltage to estimate the resistance of the LED (e.g., using Equation 17). In some examples, the apparatus can determine a forward voltage based on the series resistance of the LED, the first current, and the first diode voltage measured at the LED in response to the first current (e.g., using Equations 24 and / or 25).

[0019] A device (e.g., a pulse oximeter) may be configured to verify (e.g., validate) that an LED used by the device to determine blood oxygen saturation values ​​is correctly constructed to conform to stored calibration information (e.g., within the range defined by the calibration information). Verifying that the LED conforms to the calibration information indicates that the LED is certified and / or verified to have the correct construction for determining oxygen levels (e.g., the measurement should be accurate). In some examples, a valid sensor device may refer to a sensor device determined to have the correct construction and / or accuracy. In some examples, a valid sensor device may refer to a sensor device having a range of values ​​matching or characteristics within that range of calibration information determined during the calibration of the sensor device. That is, rather than always using calibration information to determine blood oxygen saturation values, the device (e.g., a pulse oximeter) may use the characteristics of a light-emitting diode (e.g., series resistance, forward voltage, etc.) and / or a photodiode to verify that the sensor device used by the device corresponds to the calibration information (e.g., meeting the conditions that confirm the LED and / or photodiode will provide accurate measurements).

[0020] For example, the device may determine (e.g., receive, estimate, etc.) the forward voltage across an LED during calibration in response to a single current or to each of a plurality of currents. In this example, the device may measure a first forward voltage of a first current, a second forward voltage of a second current that is different from the first current (e.g., greater than, less than, etc.), and so on, during calibration. In this example, the device may store one or more calibrated forward voltages in memory along with calibration information for the LED. After calibration, the device may use the techniques described herein to determine the forward voltage. If the measured forward voltage and the calibrated forward voltage are within a tolerance, the device may determine that the LED in service with the device (e.g., a pulse oximeter) is consistent with the calibration information and is therefore validated. In response to determining that the LED in service with the device is valid, the device may use the LED to determine an oxygen saturation level based on the calibration information. If the measured forward voltage and the calibrated forward voltage are not within a tolerance, the device may determine that the LED in service with the device is inconsistent with the calibration information and therefore may determine that the LED in service with the device is not validated. In response to the determination that the LED in service has not been verified, the device will not determine the oxygen saturation level. In this way, the device can be verified to be consistent with calibration values, which helps ensure the correct construction and accuracy of the device.

[0021] Alternatively or additionally, the device may determine (e.g., receive, estimate, etc.) the series resistance of the LED during calibration. In this example, the device may store the calibrated series resistance along with calibration information for the LED in memory. After calibration, the device may use the techniques described herein to determine the series resistance of the LED in service. If the measured series resistance and the calibrated series resistance are within a tolerance, the device may determine that the LED in service with the device (e.g., a pulse oximeter) is consistent with the calibration information and is therefore verified. In response to determining that the LED in service with the device is valid, the device may use the LED to determine the oxygen saturation level based on the calibration information. If the measured series resistance and the calibrated series resistance are not within a tolerance, the device may determine that the LED in service with the device is inconsistent with the calibration information and therefore may determine that the LED in service with the device is not verified. In response to determining that the LED in service with the device is not verified, the device will not determine the oxygen saturation level. In this way, the device can be verified to be consistent with the calibration value to help ensure the correct construction and accuracy of the device.

[0022] The device can use the resistance of the light-emitting diode (LED) to estimate the temperature of the LED die, which can be used to help ensure that the sensor device is operating within a target temperature range. In some examples, the device can apply wavelength compensation to account for the temperature at the LED die, which can improve the accuracy of measurements performed by the blood oxygenation device (e.g., oxygen saturation level, blood oxygen saturation (SpO2), etc.).

[0023] More specifically, the light-emitting diodes (LEDs) of the sensor device can be manufactured to output photonic signals at a specific wavelength within a certain manufacturing tolerance. For example, a first LED can output a first photonic signal (e.g., red light) within a first wavelength range (e.g., 630 nm to 700 nm) within a first manufacturing tolerance of 5%. In this example, a second LED can output a second photonic signal (e.g., infrared light) within a second wavelength range (e.g., 700 nm to 1200 nm) within a second manufacturing tolerance of 5%.

[0024] To account for manufacturing tolerances, some pulse oximeters may use calibration information established for each sensor. For example, some pulse oximeters may be configured to store calibration information about the pulse oximeter's LEDs in a memory (e.g., EEPROM). Calibration information can help account for manufacturing tolerances of the LEDs, which may shift the wavelength of the light emitted by the LED. However, changes in temperature can significantly affect the wavelength emitted by light-emitting diodes, particularly those emitting red light, potentially shifting it by several nanometers within an operating range between 0°C and 40°C. According to the techniques disclosed herein, the device can estimate the temperature at the LED based on the forward voltage at the LED and determine the wavelength of the light emitted by the LED based on the temperature at the LED. In this way, the techniques described herein can account for the temperature at the LED, which can improve the accuracy of pulse oximetry in performing SpO2 measurements and / or other measurements.

[0025] Figure 1 This is a conceptual block diagram illustrating an exemplary regional blood oxygen measurement device 100. Although Figure 1 The examples described herein depict a regional pulse oximetry device; however, the techniques described herein for taking into account the resistance of light-emitting diodes can be used in other devices, such as, for example, pulse oximetry devices, CO pulse oximeter devices, or another type of pulse oximeter device. Regional pulse oximetry device 100 includes a processing circuitry system 110, a memory 120, a user interface 130, a display 132, sensing circuitry systems 140, 141, and 142, and is coupled to sensing devices 150, 151, and 152. In some examples, regional pulse oximetry device 100 may be configured to, for example, determine and display a patient's brain autoregulation state during medical procedures or for longer-term monitoring (such as monitoring of prenatal infants, children, or adults). Clinicians can receive information about a patient's brain autoregulation state via display 132 and adjust treatments or therapies to suit the patient based on this information. Although regional pulse oximetry device 100 is described as an exemplary device herein, other devices may calculate blood pressure and / or use blood pressure for other physiological monitoring and perform similar compensation processes for blood pressure experiencing abrupt changes in the measured blood pressure value.

[0026] The processing circuitry system 110 described herein, along with other processors, processing circuits, controllers, control circuitry systems, etc., may include one or more processors. The processing circuitry system 110 may include any combination of integrated circuits, discrete logic circuitry systems, analog circuitry systems (such as one or more microprocessors), digital signal processors (DSPs), application-specific integrated circuits (ASICs), or field-programmable gate arrays (FPGAs). In some examples, the processing circuitry system 110 may include multiple components, such as one or more microprocessors, one or more DSPs, one or more ASICs, or one or more FPGAs, and any combination of other discrete or integrated logic circuitry systems and / or analog circuitry systems.

[0027] For example, memory 120 may be configured to store measurements of blood pressure, oxygen saturation, blood volume, other physiological parameters, the relationship between blood pressure and physiological parameters, MAP value, rSO2 value, COx value, BVS value, HVx value, and / or lower limit of self-regulation (LLA) and / or upper limit of self-regulation (ULA) values. Memory 120 may also be configured to store data such as thresholds for detecting sudden changes in blood pressure, previous LLA and ULA values ​​and / or other physiological parameters, and expected values ​​for physiological parameters. Memory 120 may also be configured to store data such as threshold levels for physiological parameters, thresholds for blood pressure, and / or thresholds for signal quality metrics. Thresholds or other data may remain constant throughout the use of device 100 and across multiple patients, or these values ​​may change over time. Memory 120 may store calibration values ​​used to validate sensing device 150. Examples of calibration values ​​may include, but are not limited to, one or more forward voltages of light-emitting diodes used during calibration, the series resistance of light-emitting diodes used during calibration, and / or another value.

[0028] Memory 120 may store program instructions, which may include one or more program modules executable by processing circuitry system 110. When executed by processing circuitry system 110, such program instructions enable processing circuitry system 110 to provide the functionality given to it herein. For example, memory 120 may store instructions on how to determine mutations in measured blood pressure, calculate ULA and LLA values, and present information to a user via user interface 130. Program instructions may be embodied in software, firmware, and / or RAMware. Memory 120 and other memory devices described herein (e.g., Figure 2 The memory 220 shown may include any volatile, non-volatile, magnetic, optical, circuit system or dielectric, such as random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory or any other digital medium.

[0029] User interface 130 and / or display 132 may be configured to present information to a user (e.g., a clinician). User interface 130 and / or display 132 may be configured to present a graphical user interface to the user, wherein each graphical user interface may include indications of values ​​for one or more physiological parameters of the subject. For example, processing circuitry system 110 may be configured to present blood pressure values, other physiological parameter values ​​(e.g., heart rate), and indications of the patient's brain autoregulation state via display 132. In some examples, if processing circuitry system 110 determines that the patient's brain autoregulation state is impaired, processing circuitry system 110 may present a notification (e.g., a warning) indicating the impaired brain autoregulation state via display 132. As another example, processing circuitry system 110 may present via display 132 an estimate of the patient's regional oxygen saturation (rSO2), an estimate of blood oxygen saturation (SpO2) determined by processing circuitry system 110, pulse rate information, respiratory rate information, blood pressure, any other patient parameters, or any combination thereof.

[0030] User interface 130 and / or display 132 may include a monitor, cathode ray tube display, flat panel display (such as a liquid crystal (LCD) display), plasma display or light-emitting diode (LED) display, personal digital assistant, mobile phone, tablet computer, laptop computer, any other suitable display device, or any combination thereof. User interface 130 may also include means for projecting audio to the user, such as a speaker. Processing circuitry system 110 may be configured to present visual, auditory, or somatosensory notifications (e.g., alarm signals) indicative of the patient's self-regulating state via user interface 130. User interface 130 may include or be part of any suitable means for conveying such information, including computer workstations, servers, desktop computers, laptops, handheld computers, mobile devices, etc. In some examples, processing circuitry system 110 and user interface 130 may be part of the same device or housed within a casing (e.g., a computer or monitor).

[0031] Sensing circuit systems 140, 141, and 142 may be configured to receive physiological signals sensed by corresponding sensing devices 150, 151, and 152, and to transmit these physiological signals to processing circuit system 110. Sensing devices 150, 151, and 152 may include any sensing hardware configured to sense a patient's physiological parameters, such as, but not limited to, one or more electrodes, optical receivers, blood pressure cuffs, etc. Sensing circuit systems 140, 141, and 142 may convert the physiological signals into signals usable for processing circuit system 110, such that processing circuit system 110 is configured to receive signals generated by sensing circuit systems 140, 141, and 142. Sensing circuit systems 140, 141, and 142 may receive signals indicative of physiological parameters from the patient, such as, but not limited to, blood pressure, regional oxygen saturation, heart rate, and respiration. Sensing circuit systems 140, 141, and 142 may include, but are not limited to, blood pressure sensing circuit systems, oxygen saturation sensing circuit systems, heart rate sensing circuit systems, temperature sensing circuit systems, electrocardiogram (ECG) sensing circuit systems, electroencephalogram (EEG) sensing circuit systems, or any combination thereof. In some examples, sensing circuit systems 140, 141, and 142 and / or processing circuit system 110 may include signal processing circuit systems, such as analog-to-digital converters.

[0032] Oxygen saturation sensing device 150 is a regional oxygen saturation sensor configured to generate an oxygen saturation signal indicating blood oxygen saturation within a region of the patient's veins, arteries, and / or capillaries. For example, oxygen saturation sensing device 150 may be configured to be placed on the patient's forehead and used to determine the oxygen saturation of the patient's blood within a region of the patient's veins, arteries, and / or capillaries located below the patient's forehead (e.g., in the cerebral cortex).

[0033] Oxygen saturation sensing device 150 may include an emitter 160 and a detector 162. The emitter 160 may include at least two light-emitting diodes (LEDs), each configured to emit light of a different wavelength, such as red or near-infrared light. In some examples, a light-driving circuitry system (e.g., within sensing device 150, sensing circuitry system 140, and / or processing circuitry system 110) may provide a light-driving signal to drive the emitter 160 and cause it to emit light. In some examples, the LEDs of the emitter 160 emit light in a wavelength range from about 600 nanometers (nm) to about 1000 nm. In a particular example, one LED of the emitter 160 is configured to emit light at a wavelength of about 730 nm, and the other LED of the emitter 160 is configured to emit light at a wavelength of about 810 nm. In other examples, other wavelengths of light may also be used.

[0034] Detector 162 may include a first detection element positioned relatively "close to" (e.g., on its proximal side) to transmitter 160 and a second detection element positioned relatively "far from" (e.g., on its distal side) to transmitter 160. Figure 1 In the example, these multiple detectors are shown as a single detector. Multiple wavelengths of light intensity can be received at both the "near" and "far" detectors 162. For example, if two wavelengths are used, the two wavelengths can be compared at each location, and the resulting signals can be compared to achieve a regional saturation value, which is related to other tissues (such as brain tissue) through which the light received at the "far" detector passes, as light is transmitted through a region of the patient (e.g., the patient's skull). Surface data from the skin and skull can be subtracted to generate a regional oxygen saturation signal of the target tissue over time. The oxygen saturation sensing device 150 can provide the regional oxygen saturation signal to the processing circuitry system 110 or any other suitable processing device to enable estimation of the patient's self-regulation status.

[0035] Blood pressure sensing device 151 and oxygen saturation sensing device 150 may be placed on the same or different parts of the patient's body. For example, blood pressure sensing device 151 and oxygen saturation sensing device 150 may be physically separate from each other and placed separately on the patient. As another example, blood pressure sensing device 151 and oxygen saturation sensing device 150 may, in some cases, be part of the same sensor or supported by a single sensor housing. For example, blood pressure sensing device 151 and oxygen saturation sensing device 150 may be part of an integrated blood pressure measurement system configured to non-invasively measure blood pressure (e.g., based on time delay in a PPG signal) and regional oxygen saturation. One or both of blood pressure sensing device 151 or oxygen saturation sensing device 150 may be further configured to measure other parameters, such as hemoglobin, respiratory rate, respiratory effort, heart rate, saturation pattern detection, response to stimuli (such as bispectral index (BIS)), or electromyographic (EMG) response to electrical stimulation. Although Figure 1 An exemplary regional blood oxygen measurement device 100 is shown, but... Figure 1 The components shown are not intended to be limiting. Additional or alternative components and / or specific implementations may be used in other examples.

[0036] The blood pressure sensing device 151 can be any sensor or device configured to obtain a patient's blood pressure (e.g., arterial blood pressure). In one example, the blood pressure sensing device 151 may include or be connected to a probe configured to be inserted into a patient's blood pressure. In another example, the blood pressure sensing device 151 may include a blood pressure cuff for non-invasive monitoring of blood pressure or an arterial line (e.g., a pressure probe configured to be placed within an artery or vein) for invasive monitoring of blood pressure. In some examples, the blood pressure sensing device 151 may include one or more pulse oximetry sensors. In some such cases, the patient's blood pressure can be obtained by processing the time delay between two or more feature points within a single volumetric plethysmography (PPG) signal obtained from a single pulse oximetry sensor.

[0037] Processing circuitry system 110 may be configured to receive one or more physiological signals generated by sensing devices 150, 151, and 152 and sensing circuitry systems 140, 141, and 142. Physiological signals may include signals indicating blood pressure, signals indicating oxygen saturation, and / or signals indicating a patient's blood volume. Processing circuitry system 110 may be configured to determine the relationship between a patient's blood pressure value and the patient's physiological parameters, such as correlation indices (e.g., COx, hemoglobin volume index (HVx)), oxygen saturation, blood volume, gradient-based measures of two or more physiological parameters, and / or another physiological parameter. Processing circuitry system 110 may determine the gradient-based measure by determining the corresponding gradient of the physiological parameter signal and determining whether the corresponding gradient tends to be consistent.

[0038] The processing circuitry system 110 can be configured to determine blood pressure values ​​at which physiological parameters are less than or greater than one or more thresholds. As an example, the processing circuitry system 110 can determine an estimate of the lower limit of brain self-regulation (LLA) based on a lowest blood pressure value at which the expected value of COx is less than a threshold, such as 0.5, 0.4, 0.3, 0.2, 0.1, or 0.0 (e.g., where 1.0 represents full correlation and 0.0 represents no correlation between blood pressure and rSO2). Therefore, the processing circuitry system 110 can determine estimates of the limits of brain self-regulation (e.g., LLA and ULA) based on blood pressure and rSO2.

[0039] The forward voltage at a diode (e.g., a light-emitting diode) can vary non-linearly with respect to different currents (e.g., see Equation 4), which can introduce errors into techniques that rely on a constant forward voltage or a forward voltage that depends linearly on the current flowing through the diode. For example, the second diode voltage measured when a second current is applied through the diode may not be twice the first diode voltage when a first current (half the magnitude of the second current) is applied through the diode. As further described below, a diode can generate a forward voltage in response to current based on multiple factors, such as, for example, the temperature at the light-emitting diode, one or more device-related constants, and the current flowing through the diode. Furthermore, the forward voltage at a diode may not be linearly proportional to the current flowing through the diode. For example, the forward voltage at a diode may have a rate of change proportional to the natural logarithm of the current flowing through the diode.

[0040] According to the technology disclosed herein, devices such as regional blood oxygenation measuring devices 100 may include a voltage measurement circuit system (e.g., within sensing device 150, sensing circuit system 140, and / or processing circuit system 110) configured to measure a first diode voltage at a light-emitting diode (e.g., a red diode, an infrared diode, etc.) of emitter 160 when a first current is applied through the light-emitting diode. Similarly, the voltage measurement circuit system may measure a second diode voltage at the light-emitting diode when a second current is applied through the light-emitting diode, and a third diode voltage at the light-emitting diode when a third current is applied through the light-emitting diode. For example, the voltage measurement circuit system may apply a first current with a first current amplitude, a second current with a second current amplitude corresponding to the first current amplitude multiplied by a multiplication factor (e.g., 2, 3, 4, etc.), and a third current with a third current amplitude corresponding to the second current amplitude multiplied by a multiplication factor. In this way, because the forward voltage at the diode changes in response to the current at the light-emitting diode increasing by two, three, four, etc., the difference between the first current and the second current and / or the difference between the second current and the third current can create a “constant” forward voltage at the light-emitting diode (see, for example, Equation 8).

[0041] The processing circuit system 110 can determine the series resistance of the light-emitting diode (LED) based on the voltages of a first diode, a second diode, and a third diode. In some examples, the processing circuit system 110 can determine the series resistance based on at least one of the voltages of the first diode, the second diode, the third diode, and the amplitudes of a first current, a second current, and a third current. For example, the processing circuit system 110 can subtract the second diode voltage from the first diode voltage to determine the first diode difference, subtract the third diode voltage from the second diode voltage to determine the second diode difference, and divide the result of subtracting the first diode difference from the second diode difference by the amplitude of the first current to generate the series resistance of the LED. In this way, the techniques described herein can determine the forward voltage at the LED by taking into account device-specific parameters of the LED and / or a nonlinear forward voltage relationship between the forward voltage and current at the LED.

[0042] Processing circuitry 110 can be configured to verify (e.g., validate) that an LED used by the device to determine blood oxygen saturation values ​​conforms to stored calibration information (e.g., within the range defined by the calibration information). Verifying that the LED conforms to the calibration information can indicate that the LED has been verified for use in determining oxygen levels (e.g., the measurement should be accurate). For example, processing circuitry 110 can determine that the LED is valid in response to determining that the estimated series resistance of the LED corresponds to (e.g., matches) the calibration series resistance determined (e.g., measured or calculated) during calibration.

[0043] Processing circuitry 110 can determine that the LED is valid in response to determining that the forward voltage of the LED corresponds to (e.g., matching) a calibration forward voltage determined (e.g., measured or calculated) during calibration. For example, processing circuitry 110 can determine the forward voltage based on the LED's series resistance, a first current, and a first diode voltage measured at the LED in response to the first current (e.g., using Equations 24 and / or 25). In this example, processing circuitry 110 can determine that the LED is valid when the forward voltage of the LED corresponds to (e.g., matching) a calibration forward voltage determined (e.g., measured or calculated) during calibration.

[0044] The processing circuitry 110 can determine the intensity of a received photon signal corresponding to an output photon signal using the output of the light-emitting diodes in response to determining that one or more light-emitting diodes and / or one or more photodiodes are valid. For example, the processing circuitry 110 can drive the light-emitting diodes to output an output photon signal to the tissue of a subject and receive a received photon signal from a detector (e.g., one or more photodiodes) after the output photon signal has been transmitted through the tissue of the subject.

[0045] The processing circuit system 110 can determine the oxygen saturation level based on the intensity of the received photon signal and the series resistance. For example, the processing circuit system 110 can determine the temperature at the light-emitting diode based on the series resistance, the voltage of the first diode, and the voltage of the second diode. More specifically, the processing circuit system 110 can subtract the voltage of the second diode from the voltage of the first diode to determine the first diode difference, subtract the result of multiplying the amplitude of the first current by the series resistance from the first diode difference to generate the voltage value of the light-emitting diode, and multiply the voltage value of the light-emitting diode by the factor parameter value of the light-emitting diode to determine the temperature at the light-emitting diode.

[0046] The processing circuit system 110 can estimate the wavelength of the output photon signal based on the temperature at the light-emitting diode. For example, the processing circuit system 110 can determine the oxygen saturation level based on the estimated wavelength of the output photon signal, the intensity of the received photon signal, and the series resistance.

[0047] In the above examples, the processing circuit system 110, the light-driving circuit system, and the voltage measurement circuit system are described as performing exemplary techniques, wherein the light-driving circuit system and the voltage measurement circuit system may be part of the processing circuit system 110, the sensing device 150, and / or the sensing circuit system 140. However, any or a combination of the processing circuit system 110, the sensing circuit system 140, and / or the sensing device 150 may be configured to perform exemplary techniques. For example, exemplary techniques may be performed by circuit systems, and examples of circuit systems include any or any combination of the processing circuit system 110, the sensing circuit system 140, and / or the sensing device 150.

[0048] Figure 2 This is a conceptual block diagram illustrating an exemplary regional oxygenation device 200 configured to monitor a patient's self-regulating state. Although Figure 2 The examples described herein depict a regional pulse oximetry device, but the techniques used to validate light-emitting diodes described herein can be applied to other devices, such as, for example, pulse oximetry devices. Figure 2 In the illustrated example, the regional pulse oximetry device 200 is coupled to the sensing device 250, and the regional pulse oximetry device and the sensing device can be collectively referred to as a regional pulse oximetry system, each generating and processing the subject's physiological signals. In some examples, the sensing device 250 and the regional pulse oximetry device 200 may be part of a pulse oximeter. The regional pulse oximetry device 200 and the sensing device 250 may each be... Figure 1 Examples of regional blood oxygen measurement devices 100 and sensing devices 150. For example... Figure 2As shown, the regional pulse oximetry device 200 includes a back-end processing circuit system 214, a user interface 230, a light-driven circuit system 240, a front-end processing circuit system 216, a control circuit system 245, and a communication interface 290. The regional pulse oximetry device 200 is communicatively coupled to a sensing device 250. The regional pulse oximetry device 200 is... Figure 1 An example of a regional pulse oximetry device 100 is shown. In some examples, the regional pulse oximetry device 200 may also include a blood pressure sensor and / or a blood volume sensor (e.g., Figure 1 (Sensing devices 151 and 152).

[0049] exist Figure 2 In the example shown, the sensing device 250 includes a light source 260, a detector 262, and a detector 263. The light source 260 may be... Figure 1 Example of transmitter 160. Detectors 262 and 263 can be... Figure 1 Examples of detector 162. In some examples, sensing device 250 may include more than two detectors. Light source 260 may be configured to emit photonic signals of light having two or more wavelengths (e.g., up to four or more wavelengths, more than four wavelengths, etc.) (e.g., red and infrared (IR), or light of another wavelength) into the tissue of a subject. For example, light source 260 may include a red light emitting source and an IR light emitting source (e.g., red and IR LEDs) for emitting light into the tissue of a subject to generate physiological signals. In some examples, the red wavelength may be between about 600 nm and about 700 nm, and the IR wavelength may be between about 800 nm and about 1000 nm. Other wavelengths of light may be used in other instances. Light source 260 may include any number of light sources with any suitable characteristics. In examples where a sensor array is used instead of sensing device 250, each sensing device may be configured to emit a single wavelength. For example, a first sensing device may emit only red light, while a second sensing device may emit only IR light. In some examples, light source 260 may be configured to emit near-infrared light of two or more wavelengths (e.g., wavelengths between 600 nm and 1000 nm) into the tissue of a subject. In some examples, light source 260 may be configured to emit light of four wavelengths (e.g., 724 nm, 770 nm, 810 nm, and 850 nm) into the tissue of a subject. In some examples, the subject may be a medical patient.

[0050] As used herein, the term "light" can refer to energy produced by a radiation source and can include one or more of electromagnetic radiation such as ultrasound, radio waves, microwaves, millimeter waves, infrared, visible light, ultraviolet light, gamma rays, or X-rays. Light can also include any wavelength within the radio, microwave, infrared, visible, ultraviolet, or X-ray spectrum, and any suitable wavelength of electromagnetic radiation may be adapted for use with this technique. Detectors 262 and 263 may be selected to be sensitive specifically to a selected target energy spectrum of the light source 260.

[0051] Detectors 262 and 263 can be configured to detect the intensity of near-infrared light at multiple wavelengths. In some examples, detectors 262 and 263 can be configured to detect the intensity of light at red and IR wavelengths. In some examples, a detector array can be used, and each detector in the array can be configured to detect the intensity of a single wavelength. In operation, light may enter detector 262 after passing through the subject's tissues, including skin, bone, and other superficial tissues (e.g., non-brain tissue and superficial brain tissue). Light may enter detector 263 after passing through the subject's tissues, including skin, bone, other superficial tissues (e.g., non-brain tissue and superficial brain tissue), and deep tissues (e.g., deep brain tissue). Detectors 262 and 263 can convert the intensity of the received light into an electrical signal. The light intensity can be directly related to the absorption and / or reflection of light in the tissue. That is, when more light at a certain wavelength is absorbed or reflected, less light of that wavelength is received from the tissue by detectors 262 and 263.

[0052] Detectors 262 and / or 263 can determine a first intensity of a first received photon signal corresponding to a first output photon signal (e.g., red light) output by a light-emitting diode using light source 260. More specifically, a processing circuitry (e.g., light-driving circuitry 240) can be configured to drive the light-emitting diode of light source 260 to output an output photon signal to the tissue of the subject and to receive the first received photon signal from detectors 262 and / or 263 after the output photon signal has been transmitted through the tissue of the subject.

[0053] After converting the received light into an electrical signal, detectors 262 and 263 can send a detection signal to a regional oximetry device 200, which processes the detection signal and determines physiological parameters (e.g., based on the absorption of red and IR wavelengths in the subject's tissue at the two detectors). For example, the regional oximetry device 200 can determine the oxygen saturation level based on the intensity of the received photon signal. More specifically, the processing circuitry system 210 can estimate the wavelength of the output photon signal based on the temperature at the light-emitting diode (e.g., a red light-emitting diode, an infrared light-emitting diode, etc.). For example, the processing circuitry system 210 can estimate the wavelength of the output photon signal to be equal to the wavelength identified in the calibration information stored in the memory 220, which corresponds to the temperature at the light-emitting diode.

[0054] The processing circuit system 210 can determine the oxygen saturation level based on the wavelength of the output photon signal and the intensity of the received photon signal. For example, the processing circuit system 210 can determine the oxygen saturation level by matching the amount of light absorbed at a specific wavelength (e.g., the amplitude difference between emitted and received light) with table entries stored in memory 220 and outputting the corresponding oxygen saturation level for the light absorption at that specific wavelength. For example, the processing circuit system 210 can determine the oxygen saturation level by matching a first absorption of light at a first wavelength (e.g., red light) and a second absorption of light at a second wavelength (e.g., infrared light) with table entries stored in memory 220 and outputting the corresponding oxygen saturation level.

[0055] One or more of the detection signals may be preprocessed by the sensing device 250 before being transmitted to the regional blood oxygenation measuring device 200. Further exemplary details of determining oxygen saturation based on optical signals can be found in commonly assigned U.S. Patent No. 9,861,317, published January 9, 2018, entitled “Methods and Systems for Determining Regional Blood Oxygen Saturation,” the entire contents of which are incorporated herein by reference.

[0056] Control circuitry system 245 may be coupled to optical drive circuitry system 240, front-end processing circuitry system 216, and back-end processing circuitry system 214, and may be configured to control the operation of these components. In some examples, control circuitry system 245 may be configured to provide timing control signals to coordinate their operation. For example, optical drive circuitry system 240 may generate one or more optical drive signals based on the timing control signals provided by control circuitry system 245, which may be used to turn light source 260 on and off. Front-end processing circuitry system 216 may use timing control signals to operate synchronously with optical drive circuitry system 240. For example, front-end processing circuitry system 216 may use timing control signals to synchronize the operation of analog-to-digital converter and demultiplexer with the optical drive signals. Additionally, back-end processing circuitry system 214 may use timing control signals to coordinate its operation with front-end processing circuitry system 216.

[0057] As discussed above, the light driving circuitry 240 can be configured to generate light driving signals provided to the light source 260 of the sensing device 250. The light driving signals can, for example, control the intensity of the light source 260 and control the timing of when the light source 260 is turned on and off. In some examples, the light driving circuitry 240 provides one or more light driving signals to the light source 260. When the light source 260 is configured to emit light of two or more wavelengths, the light driving signals can be configured to control the operation of each wavelength of light. The light driving signals may include a single signal or may include multiple signals (e.g., one signal for each wavelength of light).

[0058] The front-end processing circuitry system 216 can perform any suitable analog conditioning of the detector signal. The conditioning performed can include any type of filtering (e.g., low-pass, high-pass, band-pass, notch filtering, or any other suitable filtering), amplification, operations on the received signal (e.g., derivative taking, averaging), any other suitable signal conditioning (e.g., converting a current signal to a voltage signal), or any combination thereof. The conditioned analog signal can be processed by an analog-to-digital converter of circuitry 216, which can convert the conditioned analog signal into a digital signal. The front-end processing circuitry system 216 can operate on the analog or digital form of the detector signal to separate the different components of the signal. The front-end processing circuitry system 216 can also perform any suitable digital conditioning of the detector signal, such as low-pass, high-pass, band-pass, notch filtering, averaging, or any other suitable filtering, amplification, operations on the signal, any other suitable digital conditioning, or any combination thereof. The front-end processing circuitry system 216 can reduce the number of samples in the digital detector signal. In some examples, the front-end processing circuitry system 216 can also remove dark or ambient effects on the received signal.

[0059] The back-end processing circuitry system 214 may include processing circuitry system 210 and memory 220. Processing circuitry system 210 may include components of analog or digital electronics and may be configured to execute software, including an operating system and one or more application programs, as described herein with respect to, for example... Figure 1 The processing circuitry system 110 describes a portion of the functionality. The processing circuitry system 210 can receive and further process physiological signals received from the front-end processing circuitry system 216. For example, the processing circuitry system 210 can determine one or more physiological parameter values ​​based on the received physiological signals. For example, the processing circuitry system 210 can calculate one or more of the following: regional oxygen saturation, blood oxygen saturation (e.g., arterial, venous, or both), pulse rate, respiratory rate, respiratory effort, blood pressure, hemoglobin concentration (e.g., oxygenated, deoxygenated, and / or total), any other suitable physiological parameter, or any combination thereof.

[0060] The processing circuitry system 210 can perform any suitable signal processing on the signal, such as any suitable bandpass filtering, adaptive filtering, closed-loop filtering, any other suitable filtering, and / or any combination thereof. The processing circuitry system 210 can also receive input signals from additional sources not shown. For example, the processing circuitry system 210 can receive input signals containing information about the treatment provided to the subject from the user interface 230. The processing circuitry system 210 can use additional input signals in any determination or operation performed by it according to the back-end processing circuitry system 214 or the regional pulse oximetry device 200.

[0061] Processing circuit system 210 is an example of processing circuit system 110 and is configured to perform the techniques of this disclosure. For example, a voltage measurement circuit system (e.g., within sensing device 250, light driving circuit system 240, front-end processing circuit system 216, back-end processing circuit system 214, and / or processing circuit system 210) may be configured to measure a first diode voltage at a light-emitting diode (e.g., a red diode, an infrared diode, etc.) of light source 260 when a first current is applied through the light-emitting diode. Similarly, the voltage measurement circuit system may measure a second diode voltage at a light-emitting diode when a second current is applied through the light-emitting diode, and a third diode voltage at a light-emitting diode when a third current is applied through the light-emitting diode. For example, processing circuit system 210 may use light driving circuit system 240 to apply a first current with a first current amplitude, a second current with a second current amplitude corresponding to the first current amplitude multiplied by a multiplication factor (e.g., 2, 3, 4, etc.), and a third current with a third current amplitude corresponding to the second current amplitude multiplied by a multiplication factor.

[0062] The processing circuit system 210 can determine the series resistance of the light-emitting diode based on the voltages of the first diode, the second diode, and the third diode. In some examples, the processing circuit system 210 can determine the series resistance based on the voltages of the first diode, the second diode, the third diode, and the magnitude of the first current. For example, the processing circuit system 210 can subtract the second diode voltage from the first diode voltage to determine the first diode difference, subtract the third diode voltage from the second diode voltage to determine the second diode difference, and divide the result of subtracting the first diode difference from the second diode difference by the magnitude of the first current to generate the series resistance of the light-emitting diode.

[0063] Processing circuitry 210 may be configured to verify (e.g., validate) that sensing device 250 conforms to stored calibration information (e.g., within a range defined by the calibration information) stored in memory 220. For example, processing circuitry 210 may determine that an LED is valid in response to determining the calibration series resistance of the LED of light source 260, which corresponds to (e.g., matching, within a predetermined threshold, etc.) the calibration information of the LED determined during calibration (e.g., measured or calculated) and stored in memory 220. In some examples, processing circuitry 210 may determine that a photodiode is valid in response to determining the calibration series resistance of the photodiode of detector 262, which corresponds to (e.g., matching, within a predetermined threshold, etc.) the calibration information of the photodiode determined during calibration (e.g., measured or calculated) and stored in memory 220.

[0064] Processing circuitry 210 may determine that a light-emitting diode (LED) is valid in response to a calibration forward voltage that corresponds to (e.g., matching, within a predetermined threshold, etc.) the calibration information of the LED determined during calibration (e.g., measured or calculated) and stored in memory 220. In some examples, processing circuitry 210 may determine that a photodiode is valid in response to a calibration forward voltage that corresponds to (e.g., matching, within a predetermined threshold, etc.) the calibration information of the photodiode determined during calibration (e.g., measured or calculated) and stored in memory 220.

[0065] Processing circuitry 210 can determine whether light source 260 and / or detector 262 is valid based on a combination of forward voltage and series resistance. For example, processing circuitry 210 can determine whether a light-emitting diode (LED) is valid in response to determining that the forward voltage and series resistance of the LED of light source 260 correspond to calibration information of the LED determined during calibration (e.g., measured or calculated) and stored in memory 220, respectively, the calibration forward voltage and calibration series resistance. In some examples, processing circuitry 210 can determine whether a photodiode is valid in response to determining that the forward voltage and series resistance of the photodiode of detector 262 correspond to calibration information of the photodiode determined during calibration (e.g., measured or calculated) and stored in memory 220, respectively, the calibration forward voltage and calibration series resistance.

[0066] The processing circuitry 210 can decrypt the calibration information stored in the memory 220. For example, the processing circuitry 210 can use a forward voltage and / or a series resistance as an encryption key to encrypt the calibration information stored in the memory 220. Therefore, the processing circuitry 210 can use a forward voltage and / or a series resistance as a key to decrypt the encrypted calibration information. In this way, the processing circuitry 210 can help ensure that the calibration information stored in the memory 220 is used with sensor devices that conform to the calibration information.

[0067] The processing circuitry system 210 can be configured to determine the oxygen saturation level using the light-emitting diode of the light source 260 and / or the photodiode of the detector 262 in response to determining that the sensing device 250 is valid. For example, the processing circuitry system 210 can determine the intensity of a received photon signal corresponding to the output photon signal from the light-emitting diode of the light source 260 and the photodiode of the detector 262. For example, the processing circuitry system 210 can drive the light-emitting diode to output an output photon signal to the subject's tissue and receive a received photon signal from the photodiode after the output photon signal has traveled through the subject's tissue.

[0068] The processing circuit system 210 can determine the oxygen saturation level based on the intensity of the received photon signal and the series resistance. For example, the processing circuit system 210 can determine the temperature at the light-emitting diode based on the series resistance, the voltage of the first diode, and the voltage of the second diode. More specifically, the processing circuit system 210 can subtract the voltage of the second diode from the voltage of the first diode to determine the first diode difference, subtract the result of multiplying the amplitude of the first current by the series resistance from the first diode difference to generate the voltage value of the light-emitting diode, and multiply the voltage value of the light-emitting diode by the factor parameter value of the light-emitting diode to determine the temperature at the light-emitting diode.

[0069] The processing circuit system 210 can estimate the wavelength of the output photon signal based on the temperature at the light-emitting diode. For example, the processing circuit system 210 can determine the oxygen saturation level based on the estimated wavelength of the output photon signal, the intensity of the received photon signal, and the series resistance.

[0070] The processing circuitry system 210 can output an indication of oxygen saturation level. For example, the processing circuitry system 210 can store the indication of oxygen saturation level (e.g., a numerical value indicating the oxygen saturation level) for storage in memory 220. The processing circuitry system 210 can output the indication of oxygen saturation level (e.g., a numerical value indicating the oxygen saturation level) to user interface 230 for display on display 232. The processing circuitry system 210 can output the indication of oxygen saturation level (e.g., a numerical value indicating the oxygen saturation level) to communication interface 290 for storage and / or output at one or more external or implanted devices.

[0071] Memory 220 may include any suitable computer-readable medium capable of storing information interpretable by processing circuitry system 210. In some examples, memory 220 may store reference absorption curves, reference sets, determined values ​​(such as blood oxygen saturation, pulse rate, blood pressure, reference point location, or characteristics), initialization parameters, any other determined values, or any combination thereof, in a memory device for later retrieval. Memory 220 may also store thresholds for detecting abrupt changes in blood pressure, etc. Back-end processing circuitry system 214 may be communicatively coupled to user interface 230 and communication interface 290.

[0072] Memory 220 may store the calibration forward voltage and / or calibration series resistance of one or more light-emitting diodes of light source 260. For example, during the calibration of sensing device 250, area pulse oximetry device 200 (e.g., one or more of light-driven circuitry system 240, front-end processing circuitry system 216, back-end processing circuitry system 214, etc.) may generate the calibration forward voltage and / or calibration series resistance of light-emitting diodes of light source 260. For example, during the calibration of sensing device 250, area pulse oximetry device 200 may use the techniques described herein to determine the calibration forward voltage and / or calibration series resistance (e.g., using Equations 17 and 24).

[0073] Memory 220 may store the calibration forward voltage and / or calibration series resistance of one or more photodiodes of detectors 262 and / or detector 263. For example, during the calibration of sensing device 250, area pulse oximetry device 200 (e.g., one or more of light-driven circuitry system 240, front-end processing circuitry system 216, back-end processing circuitry system 214, etc.) may generate the calibration forward voltage and / or calibration series resistance of the photodiodes of detector 262. For example, during the calibration of sensing device 250, area pulse oximetry device 200 may use the techniques described herein to determine the calibration forward voltage and / or calibration series resistance (e.g., using Equations 17 and 24).

[0074] During the calibration of sensing device 250, area pulse oximetry device 200 or another device (e.g., calibration device) may generate calibration information. For example, area pulse oximetry device 200 or calibration device may generate an indication of a first wavelength output by a first light-emitting diode of light source 260 and an indication of a second wavelength output by a second light-emitting diode of light source 260. Memory 220 may store the calibration information based on the indication of the first wavelength output by the first light-emitting diode of light source 260 and the indication of the second wavelength output by the second light-emitting diode of light source 260. In some examples, area pulse oximetry device 200 may encrypt the calibration information. As used herein, the calibration information may include information taking into account manufacturing tolerances of light source 260, such as, but not limited to, the wavelength output by the light-emitting diodes of light source 260. For example, area pulse oximetry device 200 may encrypt the calibration information based on the difference in calibrated forward voltages. For example, area pulse oximetry device 200 may use the calibration forward voltage and / or calibration series resistance of the light-emitting diodes and / or photodiodes as encryption keys to encrypt the calibration information. In this way, the regional blood oxygen measurement device 200 can be configured to help ensure the correct construction and / or accuracy of the sensing device 250.

[0075] In some examples, user interface 230 may include input device 234, display 232, and speaker 236. User interface 230 is Figure 1 An example of user interface 130 is shown, and display 232 is... Figure 1An example of display 132 is shown. User interface 230 may include, for example, any suitable device, such as one or more medical devices (e.g., a medical monitor displaying various physiological parameters, a medical alarm, or any other suitable medical device that displays physiological parameters or uses the output of back-end processing circuitry system 214 as input), one or more display devices (e.g., a monitor, personal digital assistant (PDA), mobile phone, tablet computer, clinician workstation, any other suitable display device, or any combination thereof), one or more audio devices, one or more memory devices, one or more printing devices, any other suitable output devices, or any combination thereof.

[0076] Input device 234 may include one or more of any type of user input device, such as a keyboard, mouse, touchscreen, button, switch, microphone, joystick, touchpad, or any other suitable input device or combination of input devices. In other examples, input device 234 may be a pressure-sensitive or presence-sensitive display included as part of display 232. Input device 234 may also receive input for selecting the model of sensing device 250, blood pressure sensor, or blood pressure treatment equipment. In some examples, processing circuitry system 210 may determine the presentation type of display 232 based on user input received by input device 234.

[0077] In some examples, the subject may be a medical patient, and the display 232 may show a list of values ​​that are generally applicable to the subject, such as, for example, an oxygen saturation signal indicator, a blood pressure signal indicator, a COx signal indicator, a COx value indicator, and / or a self-regulation status indicator. The display 232 may also be configured to present additional physiological parameter information. Figure 3 The graphical user interface 300 shown can be accessed via the processing circuit system 210 under the control of the processing circuit system. Figure 2 Examples of interfaces presented by display 232. Additionally, display 232 may present, for example, one or more estimates of the subject's regional oxygen saturation (referred to as "rSO2" measurements) generated by regional oxygenation measuring device 200. Display 232 may also present indications of upper and lower limits of brain self-regulation. In some examples, user interface 230 includes speaker 236 configured to generate and provide audible sounds usable in various examples, such as when a patient's physiological parameters are outside a predetermined normal range and / or when processing circuitry system 210 determines that the sensed blood pressure value may be due to non-physiological reasons (such as due to blood pressure sensor device 151). Figure 1 (The movement of the blood pressure probe) and inaccurate results in the issuance of an audible notification.

[0078] Communication interface 290 enables the regional pulse oximeter 200 to exchange information with other external or implanted devices. Communication interface 290 may include any suitable hardware, software, or both, allowing the regional pulse oximeter 200 to communicate with electronic circuitry, devices, networks, servers or other workstations, displays, or any combination thereof. For example, the regional pulse oximeter 200 may receive MAP (or other blood pressure measurement) values ​​and / or oxygen saturation values ​​from an external device via communication interface 290.

[0079] The components of the regional pulse oximetry device 200 shown and described as individual parts are shown and described for illustrative purposes only. In some examples, the functionality of some of the components may be combined in a single part. For example, the functionality of the front-end processing circuitry system 216 and the back-end processing circuitry system 214 may be combined in a single processor system. Furthermore, in some examples, the functionality of some of the components of the regional pulse oximetry device 200 shown and described herein may be divided across multiple parts. For example, some or all of the functionality of the control circuitry system 245 may be performed in the front-end processing circuitry system 216, the back-end processing circuitry system 214, or both. In other examples, the functionality of one or more of the components may be performed in a different order or may not be required. In some examples, all the components of the regional pulse oximetry device 200 may be implemented in a processor circuitry system.

[0080] In the above examples, the processing circuit system 210, the optical driving circuit system 240, the front-end processing circuit system 216, and the voltage measurement circuit system are described as performing exemplary techniques, wherein the optical driving circuit system 240, the front-end processing circuit system 216, and the voltage measurement circuit system may be part of the processing circuit system 210. However, any or a combination of the processing circuit system 210, the optical driving circuit system 240, the front-end processing circuit system 216, and the voltage measurement circuit system may be configured to perform exemplary techniques. For example, exemplary techniques may be performed by circuit systems, and examples of circuit systems include any or any combination of the processing circuit system 210, the optical driving circuit system 240, the front-end processing circuit system 216, and the voltage measurement circuit system.

[0081] Figure 3 An exemplary graphical user interface 300 is shown, which includes self-adjusting information presented on a display. Figure 3 It is processed by the circuit system 110 in Figure 1 The process shown on the display 132 or by the processing circuitry system 210 Figure 2 An example of rendering performed on display 232 is shown. Although Figures 3 to 5 It is relative to the regional blood oxygen measurement device 100 ( Figure 1The processing circuitry system 110 is described, but in other examples, processing circuitry systems 210, 214, and / or 216 (in combination with processing circuitry system 110) are used alone or in combination with processing circuitry system 110. Figure 2 Executable Figures 3 to 5 Any part of the technology.

[0082] The graphical user interface 300 can be configured to display various information related to blood pressure, oxygen saturation, COx index, brain self-regulation limits, and / or brain self-regulation state. As shown, the graphical user interface 300 may include an oxygen saturation signal indicator 310, a blood pressure signal indicator 320, and a COx signal indicator 330. The graphical user interface 300 may include a COx value indicator 340, a self-regulation state indicator 350, and limits for self-regulation indicators 360 and 370.

[0083] The blood pressure signal indicator 320 may display a set of MAP values ​​determined by the processing circuitry system 110 of the regional oxygenation measuring device 100. The MAP values ​​may be based on the measured blood pressure value, but in other examples, the raw measured blood pressure value may be displayed (e.g., showing changes in intracardiac circulation). In some examples, the blood pressure signal indicator 320 may display the MAP values ​​as discrete points over time or in a table. The blood pressure signal indicator 320 may also display the MAP values ​​as a moving average of discrete points or a waveform. The blood pressure signal indicator 320 may display the MAP values ​​as a single value (e.g., a number) representing the current MAP value. The oxygen saturation signal indicator 310 and the COx signal indicator 330 may also display the rSO2 and COx values ​​as discrete points, in a table, as a moving average, as a waveform, and / or as a single value, respectively. In other examples, data from two or more oxygen saturation signal indicators 310, blood pressure signal indicators 320, or COx signal indicators 330 may be combined on a single graph.

[0084] The COx signal indicator 330 may present a set of correlation coefficients determined by the processing circuitry system 110. The processing circuitry system 110 may determine the correlation coefficients as a function of the oxygen saturation value presented in the oxygen saturation signal indicator 310 and the MAP value presented in the blood pressure signal indicator 320. In some examples, a COx value equal to or close to one indicates that the patient's brain self-regulation is impaired, as shown in the self-regulation state indicator 350.

[0085] COx value indicator 340 displays the COx value determined by processing circuitry system 110, which is within... Figure 3The COx value is shown as 0.8 in the example and may change over time. A COx value of 0.8 can be used by the processing circuitry system 110 to determine that the patient's brain self-regulation state is impaired. The processing circuitry system 110 can be configured to present the most recently determined COx value as the COx value in the COx value indicator 340. To determine the patient's brain self-regulation state for presentation in the self-regulation state indicator 350, the processing circuitry system 110 can determine whether the most recent MAP value shown in the blood pressure signal indicator 320 is between the limits of brain self-regulation presented in the limits of the self-regulation indicators 360 and 370. The processing circuitry system 110 may present text such as "intact" or "impaired" in the self-regulation state indicator 350. The processing circuitry system 110 may also present colors such as green (e.g., for intact brain self-regulation) or red (e.g., for impaired brain self-regulation) to help the user understand the patient's self-regulation state.

[0086] In some examples, the processing circuitry 110 may present limits for self-regulation indicators 360 and / or 370 related to blood pressure, such as millimeters of mercury (mmHg). The processing circuitry 110 may determine brain self-regulation limits (LLA and ULA) based on the relationship between the patient's blood pressure and another physiological parameter of the patient for presentation in the self-regulation indicators 360 and 370. For example, self-regulation indicator 360 may highlight when LLA has been exceeded, or self-regulation indicator 360 may highlight when ULA has been exceeded. In other examples, a single indicator may present the type of limit that the MAP value has exceeded. If LLA or ULA changes, the processing circuitry 110 may control the user interface 300 to change the corresponding value according to any change in the value of LLA or ULA.

[0087] In some examples, the processing circuitry system 110 determines the state of brain self-regulation by comparing a recently determined MAP value with the limits of brain self-regulation for presentation in the self-regulation state indicator 350. For example, if the processing circuitry system 110 estimates an LLA of 50 mmHg and determines a MAP value of 40 mmHg, the processing circuitry system 110 may determine that the patient's brain self-regulation state is impaired or incomplete. In response to determining that an estimate of a MAP value less than or equal to the LLA exceeds a predetermined time period, the processing circuitry system 110 may output a notification in the self-regulation state indicator 350 as text, color, flashing, and / or any other suitable visible or audible method.

[0088] Figure 4 An example of a sensor device 450 according to the technology described herein is shown. The sensor device 450 may be... Figure 1 Sensor device 150 and / or Figure 2An example of a sensing device 250. Light-emitting diodes 460A and 460B (collectively referred to as "light-emitting diodes") can form an example of a light source 260. Although... Figure 4 It is relative to the regional blood oxygen measurement device 100 ( Figure 1 As described in the description, but in other examples, other devices are capable of performing the same action. Figure 4 Any part of the technology. For example, processing circuit systems 210, 214, and / or 216, alone or in combination with processing circuit system 110. Figure 2 Executable Figure 4 Any part of the technology. In some examples, the light-emitting diode 460 may include a laser diode, a vertical-cavity surface-emitting laser, or another means of emitting light. In some examples, the light-emitting diode 460 may additionally or alternatively include a photodiode or another means of detecting light (e.g., red light, infrared light, etc.).

[0089] exist Figure 4 In one example, LED 460A can be configured to emit red light, and LED 460B can be configured to emit infrared light. However, in some examples, LED 460A can be configured to emit infrared light, and LED 460B can be configured to emit red light. Furthermore, LED 460 can be configured to emit light at wavelengths other than red and infrared. Figure 4 In the example, LEDs 460 are arranged in an anti-parallel configuration. For example, the anode of LED 460B may be coupled to the cathode of LED 460A, and the cathode of LED 460B may be coupled to the anode of LED 460A.

[0090] Each of the light-emitting diodes (LEDs) in LED 460 may have a corresponding body resistance. For example, LED 460A may include a body resistance 486. LED 460B may include a body resistance 487. Body resistance 486 may correspond to (e.g., be equal to) body resistance 487. In some examples, body resistance 486 may be different from body resistance 487.

[0091] Processing circuitry 110 can apply a first current from a first terminal (e.g., VD+) through a first cable (e.g., external cable and cable, cable only, etc.) to the anode of LED 460A and from the cathode of LED 460A through a second cable (e.g., external cable and cable, cable only, etc.) to a second terminal (e.g., VD-). In this example, processing circuitry 110 can be configured to measure the voltage across the first terminal (e.g., VD+) and the second terminal (e.g., VD-) when the first current is applied. Similarly, processing circuitry 110 can apply a second current from the first terminal (e.g., VD+) through the first cable to the anode and from the cathode through the second cable to the second terminal (e.g., VD-). In this example, processing circuitry 110 can be configured to measure the voltage across the first terminal (e.g., VD+) and the second terminal (e.g., VD-) when the second current is applied. In some examples, the processing circuitry 110 may be configured to apply a third current from a first terminal (e.g., VD+) through a first cable to the anode and from the cathode through a second cable to the second terminal (e.g., VD-). In this example, the processing circuitry 110 may be configured to measure the voltage across the first terminal (e.g., VD+) and the second terminal (e.g., VD-) when the third current is applied. The first current, the second current, and the third current may be ratiometric. For example, the second current may have an amplitude that is a factor (e.g., 2, 3, 4, etc.) larger than the first current, and the third current may be a factor that is a factor larger than the second current. In this way, because the forward voltage at the diode changes in response to the current at the LED increasing by two, three, four, etc., the difference between the first current and the second current and / or the difference between the second current and the third current may result in a “constant” forward voltage at the LED (e.g., see Equation 8).

[0092] Figure 4Various examples of resistors that can be considered using the techniques described herein are shown for pulse oximeters. For example, the series resistors for connecting the LED 460A to terminals VD+ and VD- of a pulse oximeter (e.g., zone pulse oximeter 100, zone pulse oximeter 200, etc.) may include a trace resistor 481, an external cable resistor 483 (e.g., a DOC-10 cable), a cable resistor 485, a bulk resistor 486, a cable resistor 488, an external cable resistor 490, and a trace resistor 492. Additionally, each of connectors 482, 484, 489, and 491 may include a corresponding resistor. Similarly, the series resistors used to connect the LED 460B to terminals VD+ and VD- of a pulse oximeter (e.g., zone pulse oximeter 100, zone pulse oximeter 200, etc.) may include a trace resistor 492, an external cable resistor 490 (e.g., a DOC-10 cable), a cable resistor 488, a bulk resistor 487, a cable resistor 485, an external cable resistor 483, and a trace resistor 481. Although Figure 4 Examples include 2 light-emitting diodes, but examples may include more than 2 diodes (e.g., 4 diodes, 6 diodes, 8 diodes, 10 diodes, etc.).

[0093] The series resistance used to connect the light-emitting diode 460 between terminals VD+ and VD-, representing an ohmic resistance between the sensor device 450 and the device (e.g., zone pulse oximetry device 100, zone pulse oximetry device 200, etc.), may have several ohms and may bias the diode voltage reading of the light-emitting diode 460. For example, an equivalent circuit may represent a light-emitting diode 460A having a series resistance including trace resistance 481, external cable resistance 483 (e.g., DOC-10 cable), cable resistance 485, body resistance 486, cable resistance 488, external cable resistance 490, and trace resistance 492. Similarly, an equivalent circuit may represent a light-emitting diode 460B having a series resistance including trace resistance 492, external cable resistance 490 (e.g., DOC-10 cable), cable resistance 488, body resistance 487, cable resistance 485, external cable resistance 483, and trace resistance 481. The pulse oximeter can be configured to improve measurement accuracy by using a very small current to help reduce voltage errors caused by the resistance of the series cable.

[0094] According to the technology disclosed herein, devices (e.g., regional pulse oxygenation measuring device 100, regional pulse oxygenation measuring device 200, etc.) can be configured to effectively account for the forward voltage at the light-emitting diode 260 using the electrical properties of the light-emitting diode, which allows the device to determine the series resistance. Details of the electrical properties of the light-emitting diode are as follows. The device can use Equation 1 to define the current through the diode, which can also be referred to as the "Shockley diode equation".

[0095]

[0096] Equation 1

[0097] Where I is the current through the diode (e.g., LED 460), I s It is the diffusion current (e.g., device-related constant), V J It is the voltage applied across the diode, n is an ideal constant, and V T Defined by Equation 2.

[0098]

[0099] Equation 2

[0100] Where k is Boltzmann's constant (e.g., 1.38E-23 joules / Kelvin), T is the absolute temperature at the diode in Kelvin, and q is the electron charge (e.g., 1.6E-19 coulombs).

[0101] The Shockley diode equation shown in Equation 1 can be approximated as shown in Equation 3.

[0102]

[0103] Equation 3

[0104] Solve for the junction voltage (e.g., V) in Equation 3. J This leads to equation 4.

[0105]

[0106] Equation 4

[0107] Adding the series resistor to Equation 4 yields Equation 5.

[0108]

[0109] Equation 5

[0110] Where V D It is the diode voltage (e.g., at terminals VD+ and VD-). It is the junction voltage under the current flowing through the diode, where I is the current flowing through the diode, and R is the junction voltage. ser It is the series resistance of the diode.

[0111] Equation 4 can be used to represent the forward voltage of a diode (e.g., V). J The difference between two different (but proportional) current levels is shown in Equation 6.

[0112] -

[0113] Equation 6

[0114] Although the examples shown in Equations 6 to 24 use a 2:1 ratio, other ratios can be used. Equations 7 and 8 show that the difference in forward voltage at the diode is constant for the ratio current.

[0115] - ) = =

[0116] Equation 7

[0117] - ) = =

[0118] Equation 8

[0119] It can be assumed They are roughly equivalent under two different currents. It is temperature-dependent. Devices (e.g., zone pulse oximetry device 100, zone pulse oximetry device 200, etc.) can be configured to use pulsation measurement and rapid back-to-back measurement to help eliminate temperature variability at the diode.

[0120] Combining equations 7 and 8, we get equation 9.

[0121]

[0122] Equation 9

[0123] In other words, Equation 9 shows that the forward voltage at the diode can remain relatively constant relative to the ratio current when the temperature is kept constant. The technique described herein can effectively “remove” the forward voltage at the diode using the difference in diode voltage. Therefore, devices (e.g., zone pulse oximetry device 100, zone pulse oximetry device 200, etc.) can be configured to determine the series resistance when the forward voltage at the diode is unknown, as described in further detail below.

[0124] The diode voltage (e.g., at terminals VD+ and VD-) can be represented by equations 10 and 12.

[0125]

[0126] Equation 10

[0127] Equation 10 can be simplified to Equation 11.

[0128]

[0129] Equation 11

[0130]

[0131] Equation 12

[0132] Equation 12 can be simplified to Equation 13.

[0133]

[0134] Equation 13

[0135] Equation 14 is obtained by using Equations 9 and 13.

[0136]

[0137] =

[0138] Equation 14

[0139] Equations 11 and 13 are used to obtain Equation 15.

[0140]

[0141] Equation 15

[0142] Simplifying Equation 15 yields Equation 16.

[0143]

[0144] Equation 16

[0145] Solve for R in equation 16 Ser Equation 17 is obtained.

[0146]

[0147] Equation 17

[0148] Table I shows exemplary results of a technique for determining the series resistance of an infrared-emitting diode according to the technique described herein, which omits the extension cable (e.g., DOC 10).

[0149] I <![CDATA[V D ]]> 2.5mA 1.16757V 0.03566V 4.376Ω 5mA 1.20323V 0.0466V 10mA 1.24983V

[0150] Table I - Resistance values ​​of infrared LEDs in the case of sensor cable only

[0151] Specifically, Table I shows an example in which the device (e.g., regional pulse oximetry device 100, regional pulse oximetry device 200, etc.) is configured to measure a first diode voltage of 1.16757V at the infrared LED when a first current of 2.5mA is applied through the infrared LED, a second diode voltage of 1.20323V at the infrared LED when a second current of 5mA is applied through the infrared LED, and a third diode voltage of 1.24983V at the infrared LED when a third current of 10mA is applied through the infrared LED. In this example, the device determines the series resistance at the infrared LED of 4.376Ω.

[0152] Table II shows exemplary results of a technique for determining the series resistance of a red-emitting diode according to the technique described herein, which omits the extension cable (e.g., DOC 10).

[0153] I <![CDATA[V D ]]> 2.5mA 1.62241V 0.02993V 3.472Ω 5mA 1.65234V 0.03861V 10mA 1.69095V

[0154] Table II - Resistance values ​​of the red LED in the case of sensor cable only

[0155] Table III shows exemplary results of a technique for determining the series resistance of an infrared-emitting diode according to the technique described herein, which uses an extension cable (e.g., DOC 10).

[0156] I <![CDATA[V D ]]> 2.5mA 1.17254V 0.04114V 6.544Ω 5mA 1.21368V 0.0575V 10mA 1.27118V

[0157] Table III - Resistance values ​​of infrared LEDs in the case of sensor cables and extension cables

[0158] Table IV shows exemplary results of a technique for determining the series resistance of a red-emitting diode according to the technique described herein, which uses an extension cable (e.g., DOC 10).

[0159] I <![CDATA[V D ]]> 2.5mA 1.62738V 0.0354V 5.648Ω 5mA 1.66278V 0.04952V 10mA 1.7123V

[0160] Table IV – Resistance values ​​of the red LED in the case of sensor cable and extension cable

[0161] Retrieve R from Tables I and III and from Tables II and IV ser The difference in values ​​yields the estimated resistance value of the extended cable shown in Table V.

[0162] <![CDATA[Change amount R of the red LED Ser > <![CDATA[Change amount R of infrared LED Ser > 2.168Ω 2.176Ω

[0163] Table V - Resistance values ​​of extension cables

[0164] In this example, the resistance value obtained using the technique described herein for extending the cable is very close to the value measured with a calibrated ohmmeter of 2.2 ohms.

[0165] Apparatus (e.g., zone pulse oximetry device 100, zone pulse oximetry device 200, etc.) may be configured to validate sensor device 450 based on series resistance using the techniques described herein. For example, the device may validate sensor device 450 based on the total calibration series resistance that determines the total series resistance between VD+ and VD- (e.g., determined using Equation 17) corresponding to (e.g., matching, within a predetermined threshold, etc.) calibration information of LED 460A determined during calibration (e.g., measured or calculated). In some examples, the device may validate sensor device 450 based on the calibration body resistance that determines the calibration information of LED 460A determined during calibration (e.g., matched, within a predetermined threshold, etc.) corresponding to (e.g., measured or calculated) volume resistance 486 and / or calibration combinations of volume resistance 486 and cable resistances 485, 488.

[0166] Devices (e.g., area pulse oximetry device 100, area pulse oximetry device 200, etc.) may be configured to use measured series resistance to authenticate or verify that an extension cable is correctly constructed. For example, the extension cable (e.g., an external cable including external cable resistances 483, 490) may include an external cable memory chip (e.g., a memory disposed within the external cable) configured to store calibrated external cable resistance values. In this example, the device may be configured to use the calibrated external cable resistance values ​​stored in the cable memory. For example, the device may subtract one or more trace resistances of trace resistances 481, 492, connector resistances of one or more connectors of connectors 482, 484, 489, 491, cable resistances 485, 488, and bulk resistance 486 from the total series resistance determined using the techniques described herein (e.g., Equation 17) to estimate the external cable resistance value. In this example, the device may verify sensor device 450 based on determining that the estimated cable resistance corresponds to (e.g., matching, within a predetermined threshold, etc.) the calibrated external cable resistance value stored in the cable memory. The memory on the pulse oximetry device (e.g., Figure 2The memory 220 may store one or more trace resistors of trace resistors 481, 492, connector resistors of one or more connectors of connectors 482, 484, 489, 491, one or more body resistors of body resistors 486, 487, and / or other resistance values. In some examples, the cable (e.g., a cable including cable resistors 485, 488) may include a cable memory chip (e.g., a memory disposed within the cable) configured to store calibration cable resistance values. In this way, the device may determine that one or more of the pulse oximetry device (e.g., using one or more trace resistors of trace resistors 481, 492), external cable, sensor, and cable (e.g., LED 460) are effective (e.g., have correct construction and / or accuracy). While this example uses LED 460A, other examples may be applicable to other LEDs (e.g., LED 460B), photodiodes, or other devices or combinations thereof.

[0167] Using the series resistance value, the device (e.g., zone pulse oximetry device 100, zone pulse oximetry device 200, etc.) can be configured to calculate the temperature at the light-emitting diode using the diode voltage as follows. Equation 18 is obtained using Equations 7 and 13.

[0168]

[0169] Equation 18

[0170] Solve equation 18 Equation 19 is obtained.

[0171]

[0172] Equation 19

[0173] Using Equations 2 and 19, we obtain Equation 20.

[0174]

[0175] Equation 20

[0176] Solving for T in equation 20 yields equation 21.

[0177]

[0178] Equation 21

[0179] The ideal constant n can be assumed to be equal to a predetermined number (e.g., 1.0). In some examples, n can be measured at manufacturing time and stored in memory 220. For example, equation 22 can be used to measure n.

[0180]

[0181] Equation 22

[0182] In other words, the device (e.g., regional pulse oximetry device 100, regional pulse oximetry device 200, etc.) can be configured to generate factor parameter values ​​based on ideal constant values. For example, the device can calculate the factor parameter values ​​as follows: Similarly, in some cases, the ideal constant value can be a predetermined value (e.g., 1) and / or can be stored in memory 220.

[0183] Devices (e.g., regional pulse oximetry device 100, regional pulse oximetry device 200, etc.) can be configured to generate small corrections to the temperature equation to account for small temperature effects on the ideal factor or other variables. For example, the device can apply Equation 23.

[0184]

[0185] Equation 23

[0186] Where T is the corrected temperature, T o The temperature is measured using Equation 21, β is the temperature correction coefficient value, and T m It is the temperature used when measuring ideal constants during manufacturing.

[0187] The device (e.g., regional pulse oximetry device 100, regional pulse oximetry device 200, etc.) can be configured to calculate the forward voltage of a diode (e.g., an infrared LED, a red LED, etc.) based on the series resistance of the diode. For example, the device can calculate Equation 24.

[0188]

[0189] Equation 24

[0190] The device (e.g., regional pulse oximetry device 100, regional pulse oximetry device 200, etc.) can be configured to compensate I. S Temperature dependence. For example, the device can use the temperature coefficient to apply linear interpolation, as shown in Equation 25.

[0191] - ))

[0192] Equation 25

[0193] Where V C It is to correct the forward voltage (which will be at T) m (voltage under) V A At temperature T A The actual junction voltage of the diode measured below, T A It is the actual temperature of the diode, T.m It is the temperature used during manufacturing (e.g., measured when measuring junction voltage), T coeff This is the temperature coefficient of the diode (e.g., the average characterization of each type of LED used). The device can be configured to use V... C and V C Compare with the junction voltage measured during manufacturing.

[0194] For example, a device (e.g., regional pulse oximetry device 100, regional pulse oximetry device 200, etc.) may be configured to validate sensor device 450 using the techniques described herein. In some examples, the device may validate sensor device 450 based on a calibration positive voltage that corresponds to (e.g., matching, within a predetermined threshold, etc.) calibration information of the light-emitting diode 460A determined (e.g., measured or calculated) during calibration, based on a forward voltage at light-emitting diode 460 determined using Equations 24 and / or 25.

[0195] Using temperature, series resistance, and diode voltage, a device (e.g., zone pulse oximetry device 100, zone pulse oximetry device 200, etc.) can be configured to calculate the junction voltage (e.g., forward voltage) when measured at different temperatures. This can be used to verify the forward voltage at the temperature to be used during manufacturing, to verify that the LED is correct, especially when the sensor device is used at various temperatures in the field.

[0196] Additionally, the device (e.g., regional pulse oximetry device 100, regional pulse oximetry device 200, etc.) can be configured to use temperature to correct for any wavelength shift, especially for red light. For an operating temperature range of 0°C to 40°C, the wavelength of red light can shift by several nanometers, which can cause SpO2 errors. For example, the device can be configured to calculate Equation 26.

[0197] - ))

[0198] Equation 26

[0199] in It is to calculate / estimate the wavelength. It is the wavelength measured during manufacturing. It is the temperature coefficient of the diode (e.g., the average characterization of each type of LED used), T A The actual temperature of the diode, T, was measured on-site by a pulse oximeter. m It refers to the temperature of the diode during manufacturing when the wavelength is measured.

[0200] Devices (e.g., zone pulse oximetry device 100, zone pulse oximetry device 200, etc.) can be configured to apply SpO2 compensation. For example, the device can apply correction for SpO2 errors at extreme temperatures based on the compensation wavelength. This can be helpful for emergency medical services (EMS) typically performed in outdoor environments. For example, outdoor environments may be excessively hot or cold, which can cause SpO2 errors. Using this compensation, the device can mitigate or eliminate errors from environments that deviate from the nominal temperature or temperature range. The device can be configured to perform compensation using wavelength changes or simply calibration adjustments.

[0201] The device (e.g., regional pulse oximetry device 100, regional pulse oximetry device 200, etc.) can be configured to carefully measure the junction voltage to obtain the wavelength using the Planck-Einstein equation (Equation 27). For example, the device can use one or more doping characteristics of the diode (e.g., red LED, infrared LED, etc.) and other non-ideal issues to obtain the wavelength.

[0202]

[0203] Equation 27

[0204] Figure 5 This is a conceptual diagram illustrating an exemplary second sensor device according to the technology described herein. Sensor device 550 may be... Figure 1 Sensor device 150 and / or Figure 2 Examples of sensing devices 250. Examples of light-emitting diodes 560A and 560B (collectively referred to as "light-emitting diodes 560"), 580A and 580B (collectively referred to as "light-emitting diodes 580"), and 582A and 582B (collectively referred to as "light-emitting diodes 582") may each form a light source 260.

[0205] although Figure 5 It is relative to the regional blood oxygen measurement device 100 ( Figure 1 As described in the description, but in other examples, other devices are capable of performing the same action. Figure 5 Any part of the technology. For example, processing circuit systems 210, 214, and / or 216, alone or in combination with processing circuit system 110. Figure 2 Executable Figure 5 Any part of the technology. In some examples, LEDs 560, 580, 582 may include laser diodes, vertical-cavity surface-emitting lasers, or other means of emitting light. In some examples, LEDs 560, 580, 582 may additionally or alternatively include photodiodes or other means of detecting light (e.g., red light, infrared light, etc.) or any combination thereof. Although Figure 5Examples include 6 LEDs, but examples may include fewer LEDs (e.g., 1, 2, 3, 4 or 5 LEDs) or more LEDs (e.g., 7, 8, 9, 10 LEDs, etc.).

[0206] exist Figure 5 In the example, one LED in each pair of LEDs 560, 580, 582 can be configured to emit red light, and one LED in each pair of LEDs 560, 580, 582 can be configured to emit infrared light. Furthermore, one or more of LEDs 560, 580, 582 can be configured to emit light at wavelengths other than red and infrared. Figure 5 In the example, each pair of LEDs 560, 580, and 582 is arranged in an anti-parallel configuration. For example, the anode of LED 560B may be coupled to the cathode of LED 560A, and the cathode of LED 560B may be coupled to the anode of LED 560A.

[0207] First terminal 574, second terminal 575, and third terminal 576 may each represent a connection to a pulse oximeter (e.g., pulse oximeter 100) using one or more cables, extension cables, one or more connectors, one or more lead bonding pads, or other resistive components. Although not shown, sensor device 550 may include resistive losses due to, for example, cable resistance, one or more connectors, one or more lead bonding pads, one or more printed circuit board (PCB) traces, one or more extension cables and one or more sensor cables, and the bulk resistance and / or other resistive losses of light-emitting diodes 560, 580, 582.

[0208] According to the technology of this disclosure, a device (e.g., a regional pulse oximetry device 100, a regional pulse oximetry device 200, etc.) can be configured to measure a first diode voltage at a light-emitting diode (e.g., any one of diodes 560, 580, 582) when a first current is applied through the light-emitting diode. Similarly, a voltage measurement circuit system can measure a second diode voltage at a light-emitting diode when a second current is applied through the light-emitting diode, and a third diode voltage at a light-emitting diode when a third current is applied through the light-emitting diode. For example, the voltage measurement circuit system can apply a first current with a first current amplitude, apply a second current with a second current amplitude corresponding to the first current amplitude multiplied by a multiplication factor (e.g., 2, 3, 4, etc.), and apply a third current with a third current amplitude corresponding to the second current amplitude multiplied by a multiplication factor. In this way, because the forward voltage at the diode changes in response to the current at the light-emitting diode increasing to two, three, four, etc., the difference between the first current and the second current and / or the difference between the second current and the third current can result in a "constant" forward voltage at the light-emitting diode (e.g., see Equation 8).

[0209] Devices (e.g., zone pulse oximetry device 100, zone pulse oximetry device 200, etc.) can be configured to determine the series resistance of a light-emitting diode (LED) based on a first diode voltage, a second diode voltage, and a third diode voltage. In some examples, the processing circuitry 110 can determine the series resistance based on at least one of the first diode voltage, the second diode voltage, the third diode voltage, and the amplitudes of a first current, a second current, and a third current. For example, the device can apply Equation 17. In this way, the techniques described herein can determine the forward voltage at the LED by taking into account device-specific parameters of the LED and / or a nonlinear forward voltage relationship between the forward voltage and current at the LED.

[0210] Devices (e.g., regional pulse oximetry device 100, regional pulse oximetry device 200, etc.) may be configured to determine whether sensor device 550 is effective (e.g., based on series resistance, forward voltage, etc.) and, in response to determining that sensor device 550 is effective (e.g., has proper construction and / or accuracy), determine the oxygen saturation level based on the intensity of the received photon signal and the series resistance. For example, processing circuit system 110 may determine the temperature at the light-emitting diode based on the series resistance, the voltage of the first diode, and the voltage of the second diode. For example, the device may apply Equation 21. The device may be configured to estimate the wavelength of the output photon signal based on the temperature at the light-emitting diode. For example, the device may determine the oxygen saturation level based on the estimated wavelength of the output photon signal and the intensity and series resistance of the received photon signal.

[0211] Figure 6This is a flowchart illustrating an exemplary technique for measuring oxygen saturation, based on the technology described herein. Although Figure 6 This description is relative to a circuit system, but such a circuit system may include a processing circuit system 110, a voltage measurement circuit system (e.g., within a sensing device 150, a sensing circuit system 140, and / or a processing circuit system 110), a sensing device 150, a sensing circuit system 140, and processing circuit systems 210, 214, and / or 216. Figure 2 One or more of them. Although Figure 6 It is described using sensor device 450, but Figure 6 The technology can be applied to other sensor devices, such as, for example Figure 5 The sensor device 550. In some examples, the first light-emitting diode and / or the second light-emitting diode may include a laser diode, a vertical-cavity surface-emitting laser, or another means of emitting light. In some examples, the first light-emitting diode and / or the second light-emitting diode may additionally or alternatively include a photodiode or another means of detecting light (e.g., red light, infrared light, etc.).

[0212] exist Figure 6 In the example, the circuit system can measure a first diode voltage at the LED when a first current is applied through the LED (602). The circuit system can measure a second diode voltage at the LED when a second current is applied through the LED (604). The circuit system can measure a third diode voltage at the LED when a third current is applied through the LED (606).

[0213] The circuit system can determine the series resistance of the light-emitting diode (LED) based on the first diode voltage, the second diode voltage, and the third diode voltage (608). For example, the circuit system can calculate Equation 17. The circuit system can determine the intensity of the received photon signal corresponding to the output photon signal using the LED in response to determining that the LED is valid (610). For example, the circuit system can determine that the LED is valid based on the series resistance. For example, the circuit system can determine that the LED is valid based on determining that the difference between the series resistance and the calibrated series resistance is less than a first predetermined threshold (e.g., having correct construction and / or accuracy). In some examples, the circuit system can determine the forward voltage of the LED based on the series resistance (e.g., using Equations 24 and / or Equation 25). In this example, the circuit system can determine that the LED is valid based on determining that the difference between the forward voltage and the calibrated forward voltage is less than a second predetermined threshold. In this example, in response to determining that the LED is valid, the circuit system can drive the LED to output an output photon signal to the subject's tissue and receive a received photon signal from the detector after the output photon signal has transmitted through the subject's tissue.

[0214] The circuit system can determine the oxygen saturation level (612) based on the intensity of the received photon signal and the series resistance. For example, the circuit system can use Equation 21 to determine the temperature at the light-emitting diode. The processing circuit system 110 can be configured to use Equation 27 to correct any shift in the wavelength using temperature. The circuit system can output an indication of the oxygen saturation level (614). For example, the circuit system can store the indication of the oxygen saturation level (e.g., a numerical value indicating the oxygen saturation level) for storage in memory 220 and / or output the indication of the oxygen saturation level to user interface 230 for display on display 232.

[0215] The following are examples described in this document.

[0216] Example 1. An apparatus for measuring oxygen saturation, the apparatus comprising a circuit system configured to: measure a first diode voltage at the light-emitting diode when a first current is applied through the light-emitting diode; measure a second diode voltage at the light-emitting diode when a second current is applied through the light-emitting diode; measure a third diode voltage at the light-emitting diode when a third current is applied through the light-emitting diode; determine a series resistance of the light-emitting diode based on the first diode voltage, the second diode voltage, and the third diode voltage; determine the intensity of a received photon signal corresponding to an output photon signal output using the light-emitting diode; determine an oxygen saturation level based on the intensity of the received photon signal and the series resistance; and output an indication of the oxygen saturation level.

[0217] Example 2. The apparatus according to Example 1, wherein the circuit system is configured to determine that the light-emitting diode is effective based on the series resistance, wherein the determination of the intensity of the received photon signal is in response to the determination that the light-emitting diode is effective.

[0218] Example 3. The apparatus according to Example 2, wherein the circuit system is configured to determine the forward voltage of the light-emitting diode based on the series resistance, wherein the determination of the light-emitting diode is valid is also based on the forward voltage of the light-emitting diode.

[0219] Example 4. An apparatus according to any one of Examples 1 to 3, wherein the circuit system is configured to: apply the first current with a first current amplitude; apply the second current with a second current amplitude corresponding to the first current amplitude multiplied by a multiplication factor; and apply the third current with a third current amplitude corresponding to the second current amplitude multiplied by the multiplication factor.

[0220] Example 5. The apparatus according to any one of Examples 1 to 4, wherein the determination of the oxygen saturation level is further based on at least one of the amplitude of the first current, the amplitude of the second current, or the amplitude of the third current.

[0221] Example 6. An apparatus according to any one of Examples 1 to 5, wherein, in order to determine the series resistance, the circuit system is configured to: subtract the second diode voltage from the first diode voltage to determine a first diode difference; subtract the third diode voltage from the second diode voltage to determine a second diode difference; and divide the result of subtracting the first diode difference from the second diode difference by the amplitude of the first current.

[0222] Example 7. An apparatus according to any one of Examples 1 to 6, wherein the circuit system is configured to: apply a first current from a first terminal through a first cable to the anode of the light-emitting diode and from the cathode of the light-emitting diode through a second cable to a second terminal, wherein, in order to measure the voltage of the first diode, the circuit system is configured to measure the voltage across the first terminal and the second terminal when the first current is applied; apply a second current from the first terminal through the first cable to the anode and from the cathode through the second cable to the second terminal, wherein, in order to measure the voltage of the second diode, the circuit system is configured to measure the voltage across the first terminal and the second terminal when the second current is applied; and apply a third current from the first terminal through the first cable to the anode and from the cathode through the second cable to the second terminal, wherein, in order to measure the voltage of the third diode, the circuit system is configured to measure the voltage across the first terminal and the second terminal when the third current is applied.

[0223] Example 8. An apparatus according to any one of Examples 1 to 7, wherein the circuit system is configured to determine the temperature at the light-emitting diode based on the series resistance, the first diode voltage, and the second diode voltage, wherein the determination of the oxygen saturation level is further based on the temperature at the light-emitting diode.

[0224] Example 9. According to the apparatus of Example 8, in order to determine the temperature at the light-emitting diode, the circuit system is configured to: subtract the second diode voltage from the first diode voltage to determine a first diode difference; subtract the result of multiplying the amplitude of the first current by the series resistance from the first diode difference to generate the voltage value of the light-emitting diode; and multiply the voltage value of the light-emitting diode by the factor parameter value of the light-emitting diode.

[0225] Example 10. The apparatus according to Example 9 further includes a memory configured to store an ideal constant value of the light-emitting diode, wherein the circuitry is configured to generate the factor parameter value based on the ideal constant value.

[0226] Example 11. According to the apparatus of Example 10, in order to generate the factor parameter value, the circuit system is configured to calculate the factor parameter value as: q / nk ln(2), where q is the charge amplitude of the electron, n is the ideal constant value, k is the Boltzmann constant, and ln(2) is the natural logarithm of 2.

[0227] Example 12. An apparatus according to any one of Examples 9 to 11, wherein the circuit system is configured to estimate the wavelength of the output photon signal based on the temperature at the light-emitting diode, wherein the determination of the oxygen saturation level is further based on the estimated wavelength of the output photon signal.

[0228] Example 13. The apparatus according to any one of Examples 1 to 12, wherein the circuit system is configured to: drive the light-emitting diode to output the output photon signal to the tissue of the subject; and receive the received photon signal from the detector after the output photon signal has been transmitted through the tissue of the subject.

[0229] Example 14. The apparatus according to any one of Examples 1 to 13, wherein the light-emitting diode is configured to emit red light or infrared light.

[0230] Example 15. The apparatus according to Examples 1 to 14, wherein the light-emitting diode is a first light-emitting diode, and wherein the anode of the second light-emitting diode is coupled to the cathode of the first light-emitting diode, and the cathode of the second light-emitting diode is coupled to the anode of the first light-emitting diode.

[0231] Example 16. A method for measuring oxygen saturation, the method comprising: measuring a first diode voltage at a light-emitting diode by a circuit system when a first current is applied through the light-emitting diode; measuring a second diode voltage at the light-emitting diode by the circuit system when a second current is applied through the light-emitting diode; measuring a third diode voltage at the light-emitting diode by the circuit system when a third current is applied through the light-emitting diode; determining a series resistance of the light-emitting diode by the circuit system based on the first diode voltage, the second diode voltage, and the third diode voltage; determining an intensity of a received photon signal corresponding to an output photon signal output using the light-emitting diode by the circuit system; determining an oxygen saturation level by the circuit system based on the intensity of the received photon signal and the series resistance; and outputting an indication of the oxygen saturation level by the circuit system.

[0232] Example 17. The method according to Example 16, the method comprising: determining by the circuit system that the light-emitting diode is effective based on the series resistance, wherein the intensity of the received photon signal is determined in response to the determination that the light-emitting diode is effective.

[0233] Example 18. The method according to Example 17, the method comprising: determining the forward voltage of the light-emitting diode by the circuit system based on the series resistance, wherein determining that the light-emitting diode is valid is also based on the forward voltage of the light-emitting diode.

[0234] Example 19. A method according to any one of Examples 16 to 18, the method comprising: applying a first current by the circuit system with a first current amplitude; applying a second current by the circuit system with a second current amplitude, the second current amplitude corresponding to the first current amplitude multiplied by a multiplication factor; and applying a third current by the circuit system with a third current amplitude, the third current amplitude corresponding to the second current amplitude multiplied by the multiplication factor.

[0235] Example 20. A system for measuring oxygen saturation, the system comprising: a sensor device including a light-emitting diode (LED); a blood oxygen measuring device including a circuit system configured to: measure a first diode voltage at the LED when a first current is applied through the LED; measure a second diode voltage at the LED when a second current is applied through the LED; determine a series resistance of the LED based on the first diode voltage and the second diode voltage; determine the intensity of a received photon signal corresponding to an output photon signal output using the LED; determine an oxygen saturation level based on the intensity of the received photon signal and the series resistance; and output an indication of the oxygen saturation level.

[0236] Example 21. An apparatus for measuring oxygen saturation, the apparatus comprising a circuit system configured to: determine a series resistance of a light-emitting diode based on a first diode voltage at a first current, a second diode voltage at a second current, and a third diode voltage at a third current; determine the intensity of a received photon signal corresponding to an output photon signal output using the light-emitting diode; determine an oxygen saturation level based on the intensity of the received photon signal and the series resistance; and output an indication of the oxygen saturation level.

[0237] Example 22. The apparatus according to Example 21, wherein the circuit system is configured to determine that the light-emitting diode is effective based on the series resistance, wherein the determination of the intensity of the received photon signal is in response to the determination that the light-emitting diode is effective.

[0238] Example 23. The apparatus according to Example 22, wherein the circuit system is configured to determine the forward voltage of the light-emitting diode based on the series resistance, wherein the determination is valid and is also based on the forward voltage of the light-emitting diode.

[0239] Example 24. An apparatus according to any combination of Examples 21 to 23, wherein, in order to determine the series resistance, the circuit system is configured to: apply a first current with a first current amplitude; apply a second current with a second current amplitude corresponding to the first current amplitude multiplied by a multiplication factor; and apply the third current with a third current amplitude corresponding to the second current amplitude multiplied by the multiplication factor.

[0240] Example 25. An apparatus according to any combination of Examples 21 to 24, wherein, in order to determine the oxygen saturation level, the circuit system is configured to determine the oxygen saturation level based on the intensity of the received photon signal and the series resistance, and also based on at least one of the amplitude of the first current, the amplitude of the second current, or the amplitude of the third current.

[0241] Example 26. An apparatus according to any combination of Examples 21 to 25, wherein, in order to determine the series resistance, the circuit system is configured to: subtract the second diode voltage from the first diode voltage to determine a first diode difference; subtract the third diode voltage from the second diode voltage to determine a second diode difference; and divide the result of subtracting the first diode difference from the second diode difference by the magnitude of the first current.

[0242] Example 27. An apparatus according to any combination of Examples 21 to 26, wherein, in order to determine the series resistance, the circuit system is configured to: apply a first current from a first terminal through a first cable to the anode of the light-emitting diode and from the cathode of the light-emitting diode through a second cable to a second terminal and measure the voltage of the first diode, wherein, in order to measure the voltage of the first diode, the circuit system is configured to measure the voltage across the first terminal and the second terminal when the first current is applied to the circuit system; apply a second current from the first terminal through the first cable to the anode and from the cathode through the second cable to the second terminal and measure the voltage of the second diode, wherein, in order to measure the voltage of the second diode, the circuit system is configured to measure the voltage across the first terminal and the second terminal when the second current is applied to the circuit system; and apply a third current from the first terminal through the first cable to the anode and from the cathode through the second cable to the second terminal and measure the voltage of the third diode, wherein, in order to measure the voltage of the third diode, the circuit system is configured to measure the voltage across the first terminal and the second terminal when the third current is applied to the circuit system.

[0243] Example 28. An apparatus according to any combination of Examples 21 to 27, wherein the circuit system is configured to determine the temperature at the light-emitting diode based on the series resistance, the first diode voltage, and the second diode voltage, wherein, in order to determine the oxygen saturation level, the circuit system is configured to determine the oxygen saturation level based on the intensity of the received photon signal and the series resistance, and also based on the temperature at the light-emitting diode.

[0244] Example 29. According to the apparatus of Example 28, in order to determine the temperature at the light-emitting diode, the circuit system is configured to: subtract the second diode voltage from the first diode voltage to determine a first diode difference; subtract the result of multiplying the amplitude of the first current by the series resistance from the first diode difference to generate the voltage value of the light-emitting diode; and multiply the voltage value of the light-emitting diode by a factor parameter value of the light-emitting diode.

[0245] Example 30. The apparatus according to Example 29 further includes a memory configured to store an ideal constant value of the light-emitting diode, wherein the circuitry is configured to generate the factor parameter value based on the ideal constant value.

[0246] Example 31. According to the apparatus of Example 30, in order to generate the factor parameter value, the circuit system is configured to calculate the factor parameter value as: q / nk ln(2), where q is the charge amplitude of the electron, n is the ideal constant value, k is the Boltzmann constant, and ln(2) is the natural logarithm of 2.

[0247] Example 32. An apparatus according to any combination of Examples 28 to 31, wherein the circuit system is configured to estimate the wavelength of the output photon signal based on the temperature at the light-emitting diode, wherein, in order to determine the oxygen saturation level, the circuit system is configured to determine the oxygen saturation level based on the intensity of the received photon signal and the series resistance and also based on the estimated wavelength of the output photon signal.

[0248] Example 33. An apparatus according to any combination of Examples 21 to 32, wherein the circuitry is configured to: drive the light-emitting diode to output the output photon signal to the tissue of the subject; and receive the received photon signal from a detector after the output photon signal has been transmitted through the tissue of the subject.

[0249] Example 34. The apparatus according to any combination of Examples 21 to 33, wherein the light-emitting diode is configured to emit red light or infrared light.

[0250] Example 35. An apparatus according to any combination of Examples 21 to 34, wherein the light-emitting diode is a first light-emitting diode, and wherein the anode of the second light-emitting diode is coupled to the cathode of the first light-emitting diode, and the cathode of the second light-emitting diode is coupled to the anode of the first light-emitting diode.

[0251] Example 36. A method for measuring oxygen saturation, the method comprising: determining, by a circuit system, a series resistance of a light-emitting diode (LED) based on a first diode voltage at a first current, a second diode voltage at a second current, and a third diode voltage at a third current; determining, by the circuit system, the intensity of a received photon signal corresponding to an output photon signal output using the LED; determining, by the circuit system, an oxygen saturation level based on the intensity of the received photon signal and the series resistance; and outputting an indication of the oxygen saturation level by the circuit system.

[0252] Example 37. The method according to Example 36, the method comprising: determining by the circuit system that the light-emitting diode is effective based on the series resistance, wherein the intensity of the received photon signal is determined in response to the determination that the light-emitting diode is effective.

[0253] Example 38. The method according to Example 37, the method comprising: determining the forward voltage of the light-emitting diode by the circuit system based on the series resistance, wherein determining that the light-emitting diode is valid is also based on the forward voltage of the light-emitting diode.

[0254] Example 39. The method according to any combination of Examples 36 to 38, wherein determining the series resistance comprises: applying a first current by the circuit system with a first current amplitude; applying a second current by the circuit system with a second current amplitude corresponding to the first current amplitude multiplied by a multiplication factor; and applying the third current by the circuit system with a third current amplitude corresponding to the second current amplitude multiplied by the multiplication factor.

[0255] Example 40. A system for measuring oxygen saturation, the system comprising: a sensor device including a light-emitting diode (LED); and a blood oxygen measuring device including a circuit system configured to: determine a series resistance of the LED based on a first diode voltage at a first current, a second diode voltage at a second current, and a third diode voltage at a third current; determine the intensity of a received photon signal corresponding to an output photon signal output using the LED; determine an oxygen saturation level based on the intensity of the received photon signal and the series resistance; and output an indication of the oxygen saturation level.

[0256] This disclosure contemplates a computer-readable storage medium comprising instructions that cause a processor to perform any of the functions and techniques described herein. The computer-readable storage medium may take any exemplary form of volatile, non-volatile, magnetic, optical, or electrical media, such as RAM, ROM, NVRAM, EEPROM, or flash memory. The computer-readable storage medium may be referred to as non-transitory. Programmers (such as patient programmers or clinician programmers) or other computing devices may also contain more portable, removable memory types to enable easy data transfer or offline data analysis.

[0257] The technologies described in this disclosure (including those attributed to regional pulse oximetry devices 100 and 200, processing circuitry systems 110, 210, 214 and 216, memory 120 and 220, display 132 and 232, sensing circuitry systems 140 to 142, circuitry systems 240 and 245, sensing devices 150, 151, 152 and 250, and various constituent components) can be implemented at least in part in hardware, software, firmware, or any combination thereof. For example, various aspects of the technology can be implemented within one or more processors embodied in a patient monitor (such as a multi-parameter patient monitor (MPM) or other device), a remote server, or other device, the one or more processors including one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuitry systems, and any combination of such components. The terms “processor” or “processing circuitry system” can generally refer to any of the aforementioned logic circuitry systems, alone or in combination with other logic circuitry systems, or any other equivalent circuitry system.

[0258] As used herein, the term "circuit system" refers to an ASIC, electronic circuit, processor (shared, dedicated, or grouped), and memory, combinational logic circuit, and / or other suitable components that provide the described functionality and execute one or more software or firmware programs. The term "processing circuit system" refers to one or more processors distributed across one or more devices. For example, a "processing circuit system" may include a single processor or multiple processors on a single device. A "processing circuit system" may also include processors on multiple devices, wherein the operations described herein may be distributed across processors and devices.

[0259] Such hardware, software, and firmware may be implemented within the same device or in separate devices to support the various operations and functions described herein. For example, any technique or process described herein may be performed within a single device or at least partially distributed between two or more devices, such as between regional pulse oximetry devices 100 and 200, processing circuitry systems 110, 210, 214, and 216, memory 120 and 220, sensing circuitry systems 140 to 142, and / or circuitry systems 240 and 245. Additionally, any of the described units, modules, or components may be implemented together or individually as discrete but interoperable logic devices. Describing different features as modules or units is intended to highlight different functional aspects and does not necessarily imply that such modules or units must be implemented by separate hardware or software components. Rather, the functionality associated with one or more modules or units may be performed by separate hardware or software components or integrated within common or separate hardware or software components.

[0260] The techniques described in this disclosure can also be embodied or encoded in an article of manufacture comprising a non-transitory computer-readable storage medium encoded with instructions. Instructions embedded or encoded in an article of manufacture comprising the encoded non-transitory computer-readable storage medium may cause one or more programmable processors or other processors to implement one or more techniques described herein, such as when the instructions included or encoded in the non-transitory computer-readable storage medium are executed by one or more processors. Exemplary non-transitory computer-readable storage media may include RAM, ROM, programmable ROM (PROM), erasable programmable ROM (EPROM), electronically erasable programmable ROM (EEPROM), flash memory, hard disk, optical disk ROM (CD-ROM), floppy disk, magnetic tape, magnetic media, optical media, or any other computer-readable storage device or tangible computer-readable medium.

[0261] In some examples, computer-readable storage media include non-transitory media. The term "non-transitory" may indicate that the storage medium is not embodied in a carrier or propagating signal. In some examples, non-transitory storage media may store data that may change over time (e.g., in RAM or cache). Elements of the devices and circuit systems described herein (including, but not limited to, regional pulse oximetry devices 100 and 200, processing circuit systems 110, 210, 214 and 216, memories 120 and 220, displays 132 and 232, sensing circuit systems 140 to 142, circuit systems 240 and 245, and sensing devices 150 to 152 and 250) can be programmed with various forms of software. For example, one or more processors may be implemented at least partially as or include one or more executable applications, application modules, libraries, classes, methods, objects, routines, subroutines, firmware, and / or embedded code.

[0262] Various examples of this disclosure have been described. Any combination of the described systems, operations, or functions is contemplated. These and other examples are within the scope of the following claims.

Claims

1. An apparatus for measuring oxygen saturation, the apparatus comprising a circuit system configured to: Measure the first diode voltage at the light-emitting diode when a first current is applied through the light-emitting diode; The second diode voltage at the light-emitting diode is measured when a second current is applied through the light-emitting diode; The third diode voltage at the light-emitting diode is measured when a third current is applied through the light-emitting diode; The series resistance of the light-emitting diode is determined based on the voltage of the first diode, the voltage of the second diode, and the voltage of the third diode. Determine the intensity of the received photon signal corresponding to the output photon signal using the light-emitting diode; The oxygen saturation level is determined based on the intensity of the received photon signal and the series resistance; and Output an indication of the oxygen saturation level. The circuit system is configured to determine whether the light-emitting diode is active based on the series resistance, and The determination of the intensity of the received photon signal is in response to the determination that the light-emitting diode is valid.

2. The apparatus of claim 1, wherein the circuit system is configured as follows: The forward voltage of the light-emitting diode is determined based on the series resistance, wherein the determination that the light-emitting diode is valid is also based on the forward voltage of the light-emitting diode.

3. The apparatus according to claim 1 or 2, wherein the circuit system is configured as follows: The first current is applied with a first current amplitude; The second current is applied with a second current amplitude, which corresponds to the first current amplitude multiplied by a multiplication factor; as well as The third current is applied with a third current amplitude, which corresponds to the second current amplitude multiplied by the multiplication factor.

4. The apparatus of claim 1 or 2, wherein the determination of the oxygen saturation level is further based on at least one of the amplitude of the first current, the amplitude of the second current, or the amplitude of the third current.

5. The apparatus according to claim 1 or 2, wherein, To determine the series resistance, the circuit system is configured as follows: The difference in the first diode voltage is determined by subtracting the second diode voltage from the first diode voltage. The difference in the second diode is determined by subtracting the voltage of the third diode from the voltage of the second diode. as well as The result of subtracting the difference between the second diode and the first diode is divided by the amplitude of the first current.

6. The apparatus according to claim 1 or 2, wherein the circuit system is configured as follows: The first current is applied from the first terminal through the first cable to the anode of the light-emitting diode and from the cathode of the light-emitting diode through the second cable to the second terminal, wherein... In order to measure the voltage of the first diode, the circuit system is configured to measure the voltage across the first terminal and the second terminal when the first current is applied; The second current is applied from the first terminal through the first cable to the anode and from the cathode through the second cable to the second terminal, wherein, in order to measure the voltage of the second diode, the circuit system is configured to measure the voltage across the first terminal and the second terminal when the second current is applied; and The third current is applied from the first terminal through the first cable to the anode and from the cathode through the second cable to the second terminal, wherein, in order to measure the voltage of the third diode, the circuit system is configured to measure the voltage across the first terminal and the second terminal when the third current is applied.

7. The apparatus of claim 1 or 2, wherein the circuit system is configured to determine the temperature at the light-emitting diode based on the series resistance, the first diode voltage, and the second diode voltage, wherein the determination of the oxygen saturation level is further based on the temperature at the light-emitting diode.

8. The apparatus according to claim 7, wherein, To determine the temperature at the light-emitting diode, the circuit system is configured as follows: The difference in the first diode voltage is determined by subtracting the second diode voltage from the first diode voltage. The voltage value of the light-emitting diode is generated by subtracting the result of multiplying the amplitude of the first current by the series resistance from the first diode difference. as well as Multiply the voltage value of the light-emitting diode by the factor parameter value of the light-emitting diode.

9. The apparatus of claim 8, further comprising a memory configured to store an ideal constant value for the light-emitting diode, wherein the circuitry is configured to generate the factor parameter value based on the ideal constant value.

10. The apparatus according to claim 9, wherein, In order to generate the factor parameter values, the circuit system is configured to calculate the factor parameter values ​​as follows: Where q is the charge amplitude of the electron, n is the ideal constant value, k is the Boltzmann constant, and ln (2) is the natural logarithm of 2.

11. The apparatus of claim 7, wherein the circuit system is configured as follows: The wavelength of the output photon signal is estimated based on the temperature at the light-emitting diode, wherein the determination of the oxygen saturation level is also based on the estimated wavelength of the output photon signal.

12. The apparatus according to claim 1 or 2, wherein the circuit system is configured as follows: Drive the light-emitting diode to output the output photon signal to the tissue of the subject; and The received photon signal is received from the detector after the output photon signal has passed through the subject's tissue.

13. The apparatus of claim 1 or 2, wherein the light-emitting diode is configured to emit red light or infrared light.

14. The apparatus according to claim 1 or 2, wherein the light-emitting diode is a first light-emitting diode, and wherein the anode of the second light-emitting diode is coupled to the cathode of the first light-emitting diode, and the cathode of the second light-emitting diode is coupled to the anode of the first light-emitting diode.

Images