Method and system for oxygen sensor prediction in medical gas flow devices

Abstract

The present invention is entitled "Method and system for oxygen sensor prediction in medical gas flow devices." The present invention provides methods and systems for oxygen sensors included in medical gas flow devices, such as an anesthetizing machine. In one embodiment, a method for a medical gas flow device includes tracking an output voltage of an oxygen sensor over time during calibration, and in response to the output voltage decreasing from an initial calibration output voltage by at least a threshold amount, estimating an end-of-life date for the oxygen sensor and outputting a replacement notification.

Description

Technical Field

[0001] The embodiments of the subject matter disclosed herein relate to systems and methods for oxygen sensors used in medical devices. Background Technology

[0002] Some types of medical devices, such as ventilators and anesthesia machines, may include advanced respiratory systems for delivering breathable gases into and out of a patient's lungs. Advanced respiratory systems may include sensors for monitoring the oxygen concentration in the breathable gas delivered to the patient. In some examples, the sensor may be an electrochemical oxygen sensor that generates a voltage proportional to the oxygen concentration in the breathable gas until the sensor's working electrodes are depleted. In other medical devices, including incubators, an environment providing an oxygen concentration greater than 21% (air) around the patient is provided, and electrochemical oxygen sensors may be used to monitor and control the oxygen concentration in the patient's surrounding environment. Summary of the Invention

[0003] In one embodiment, a method for a medical gas flow device includes tracking the output of an oxygen sensor over time during calibration, and estimating the end-of-life date of the oxygen sensor and outputting a replacement notification in response to a decrease in the output from an initial calibration output by at least a threshold amount. This allows for timely replacement of the oxygen sensor, thereby reducing the incidence of premature replacement and also reducing the incidence of unintended replacement.

[0004] It should be understood that the above brief description is provided to introduce selected concepts further described in the detailed embodiments in a simplified form. This is not intended to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims following the detailed embodiments. Furthermore, the claimed subject matter is not limited to embodiments that address any shortcomings mentioned above or in any part of this disclosure. Attached Figure Description

[0005] This disclosure will be better understood by referring to the following description of non-limiting embodiments, in which:

[0006] Figure 1 An anesthesia machine according to one embodiment is illustrated schematically;

[0007] Figure 2 The illustration schematically shows that, according to one embodiment, it may include... Figure 1 The advanced respiratory system in an anesthesia machine;

[0008] Figure 3 The illustration schematically shows that, according to one embodiment, it may include... Figure 2 Oxygen sensors in advanced respiratory systems;

[0009] Figure 4A flowchart illustrating an exemplary method for monitoring an oxygen sensor in a medical device and estimating its end-of-life date, according to one embodiment, is shown; and

[0010] Figure 5 An exemplary graph is shown that tracks calibration measurements of an oxygen sensor over time according to one embodiment to estimate the end-of-life date. Detailed Implementation

[0011] The following describes various embodiments relating to an oxygen sensor in a medical gas flow device, which may be an anesthesia machine, such as... Figure 1 An exemplary anesthesia machine is shown. An anesthesia machine may include an advanced respiratory system, such as... Figure 2 An exemplary advanced respiratory system is shown for delivering medical gases to a patient. The advanced respiratory system may include various sensors, including an oxygen sensor, to monitor the composition of the medical gases delivered to the patient. Figure 3 The illustration shows that it may include in Figure 2 A cross-sectional view of an exemplary oxygen sensor in an advanced respiratory system. Specifically, Figure 3 The oxygen sensor shown is an electrochemical fuel cell type oxygen sensor, which has an anode that is oxidized over time when the oxygen sensor is exposed to oxygen. Oxidation of the anode causes the output voltage of the oxygen sensor to change over time until the anode is completely oxidized and the oxygen sensor ceases to function. Therefore, Figure 4 Exemplary methods for estimating the end-of-life date of an oxygen sensor are provided. For example, a controller can use an oxygen sensor calibration method to track changes in the output voltage and correlate these changes with an estimated end-of-life date, as exemplified in [example provided]. Figure 5 As shown in the diagram, the estimated end-of-life date can be the date on which the oxygen sensor is recommended for replacement, and can be communicated, for example, to the operator of the medical gas flow device. This allows for replacement before the oxygen sensor ceases operation.

[0012] The advantages achievable in practice of some embodiments of the described system and technology include the ability of oxygen sensors to be used in medical gas flow devices until substantially depleted by prompting the ordering of oxygen sensor replacements based on estimated end-of-life dates, without the risk of downtime due to unexpected oxygen sensor depletion. Furthermore, shelf-storage time for oxygen sensor replacements can be reduced because the timing of replacement orders can be more accurate relative to, for example, averaging the number of oxygen replacements. For instance, an average oxygen sensor replacement time may not accurately reflect the duration before an oxygen sensor depletes due to the unique oxygen exposure conditions of each sensor. Since oxygen sensors are sensitive to storage conditions such as temperature, reducing shelf-storage reduces oxygen sensor degradation. By accurately estimating the end-of-life dates of oxygen sensors and prompting replacement ordering accordingly, oxygen sensor costs can be reduced. Overall, user satisfaction can be improved.

[0013] Now turn to the attached image. Figure 1 An embodiment of a medical gas flow device is schematically illustrated. In the illustrated embodiment, the medical gas flow device is an anesthesia machine 100. The anesthesia machine 100 includes a frame (or housing) 102. In some embodiments, the frame 102 may be supported by casters, wherein the movement of the casters may be controlled by one or more locks (e.g., stop). In some examples, the frame 102 may be formed of a plastic material (e.g., polypropylene). In other examples, the frame 102 may be formed of a different type of material (e.g., metal, such as steel).

[0014] The anesthesia machine 100 also includes an anesthesia display device 104, a patient monitoring display device 106, a breathing gas module 108, one or more patient monitoring modules such as a patient monitoring module 110, an advanced respiratory system (ABS) 112 (explained in more detail below), an anesthetic vaporizer 114, and an anesthetic reservoir 116. The anesthesia machine 100 may also include a main power indicator 124, a system activation switch 126 (in one example, the system activation switch allows gas flow when activated), an oxygen flushing button 128, and an oxygen control 130. The anesthetic vaporizer 114 vaporizes the anesthetic and combines the vaporized anesthetic with one or more medical-grade gases (e.g., oxygen, air, nitrous oxide, or combinations thereof) for delivery to the patient.

[0015] The anesthesia machine 100 may additionally include an integrated suction device, an auxiliary oxygen flow controller, and various other components for providing and / or controlling the flow of one or more medical-grade gases to the patient. For example, the anesthesia machine 100 includes one or more tubing connections 146 for coupling the anesthesia machine to a tubular gas source. Additionally, the anesthesia machine 100 includes a cylindrical bracket 144 through which one or more gas holding cylinders 148 can be coupled to the anesthesia machine. Thus, gases, including but not limited to air, oxygen, nitrogen, and nitrous oxide, can be supplied to the anesthesia machine via tubing and / or cylindrical connections. As described above, the gas entering the anesthesia machine can be mixed with vaporized anesthetic at the anesthetic vaporizer 114 and supplied to the patient via the ABS 112. The anesthesia machine may also include a serial port, a collection bottle connection, a cylindrical wrench storage area, and an anesthetic gas purging system.

[0016] In some embodiments, the ABS 112 may include an expiratory check valve at expiratory port 120, an expiratory flow sensor at expiratory port 120, an inspiratory check valve at inspiratory port 118, an inspiratory flow sensor at inspiratory port 118, an absorption canister, a manual cuff port, a ventilator release device, an adjustable pressure relief valve, a cuff / explosion switch, and a bellows assembly. When the patient's breathing circuit is coupled to the ABS 112, respiratory gases (e.g., air, oxygen, and / or nitrous oxide mixed with a vaporized anesthetic) exit the anesthesia machine from inspiratory port 118 and proceed to the patient. Exhaled gases from the patient re-enter the anesthesia machine via expiratory port 120, wherein carbon dioxide may be removed from the exhaled gases via the absorption canister. Reference will be made below. Figure 2 An exemplary implementation of an advanced respiratory system is described.

[0017] During operation of the anesthetic vaporizer 114, the operator (e.g., an anesthesiologist) can regulate the amount of vaporized anesthetic supplied to the patient by adjusting the flow rate of gas from a gas source (e.g., a tubing supply) to the vaporizer. The operator can regulate the gas flow rate from the gas source to the vaporizer by adjusting one or more flow control devices. For example, the flow control device may include an analog and / or digital control dial and / or other user input device configured to actuate one or more flow control valves of the anesthesia machine 100. In some embodiments, a first flow control valve may be positioned between the gas source and the anesthetic vaporizer 114 and may be actuated via the flow control device to a fully open position, a fully closed position, and multiple positions between the fully open and fully closed positions.

[0018] The anesthesia machine 100 may additionally include one or more valves configured to allow gas from a gas source to bypass the anesthetic vaporizer 114. The valves allow a first portion of gas to flow directly from the gas source to the inhalation port 118, and a second portion of gas to flow from the gas source through the anesthetic vaporizer 114 to mix with the vaporized anesthetic before flowing to the inhalation port 118. By adjusting the ratio of the first portion of gas to the second portion of gas, the operator can control the concentration of the vaporized anesthetic administered to the patient via the inhalation port 118.

[0019] Additionally, the aforementioned regulation can be facilitated at least in part based on the output from the respiratory gas module 108. The respiratory gas module 108 can be configured to measure various parameters of the gas leaving the vaporizer and / or supplied to the patient. For example, the respiratory gas module 108 can measure the concentrations of carbon dioxide, nitrous oxide, and anesthetic supplied to the patient. Furthermore, the respiratory gas module 108 can measure respiratory rate, minimum alveolar concentration, patient oxygen, and / or other parameters. The output of the respiratory gas module 108 can be displayed on a display device (e.g., anesthesia display device 104 and / or patient monitoring display device 106) via a graphical user interface and / or used by a controller to provide closed-loop feedback control of the amount of anesthetic supplied to the patient.

[0020] ABS 112 may optionally be coupled to a breathing circuit (not shown) via one or more tubes (e.g., gas channels) 122. The breathing circuit may be coupled between the patient's airway (e.g., via a breathing mask or endotracheal tube positioned to cover the patient's mouth and / or nose) and an inspiratory port 118 and an expiratory port 120. A gas (e.g., one or more medical gases or a mixture of one or more medical gases and a vaporized anesthetic from an anesthetic vaporizer 114) may flow from the inspiratory port 118 through the breathing circuit and into the patient's airway, where it is absorbed by the patient's lungs. By adjusting the concentration of the vaporized anesthetic in the gas as described above, the operator can adjust the degree of anesthesia in the patient.

[0021] While the breathing circuit is coupled to the airway, anesthetic and / or fresh gas (without anesthetic) may flow into the patient's airway (e.g., by inhalation) via the inspiratory port 118 and the inspiratory check valve. For example, the inspiratory check valve may automatically open in response to the patient's inhalation (e.g., without operator input or adjustment) and automatically close in response to the patient's exhalation. Similarly, the expiratory check valve may automatically open in response to the patient's exhalation and automatically close in response to the patient's inhalation.

[0022] In some embodiments, an operator may additionally or alternatively control one or more operating parameters of the anesthesia machine 100 via an electronic controller 140 of the anesthesia machine 100. The controller 140 includes a processor operatively connected to a memory. The memory may be a non-transitory computer-readable medium and may be configured to store computer-executable code (e.g., instructions) that will be processed by the processor to execute one or more routines (such as those described herein). The memory may also be configured to store data received by the processor. Although the controller 140 is shown as being positioned in... Figure 1 The controller 140 may be located at a single location within the anesthesia machine 100, but it should be understood that the controller 140 may be located at various locations within, around, and / or away from the anesthesia machine 100. For example, the controller 140 may include multiple devices / modules that may be distributed throughout the anesthesia machine 100. Thus, the controller 140 may include multiple controllers at various locations within the anesthesia machine 100. Alternatively, the controller 140 may include one or more devices / modules located outside the anesthesia machine 100, near the anesthesia machine 100 (e.g., in the same room), or away from the anesthesia machine 100 (e.g., a remote server). In each example, the multiple devices / modules may be communicatively coupled via wired and / or wireless connections.

[0023] Furthermore, the controller 140 may also be communicatively coupled (e.g., via a wired or wireless connection) to one or more external or remote computing devices 142. For example, the remote computing device 142 may include a hospital computing system, and the controller 140 may be configured to share (e.g., send and receive) various information with the remote computing device 142, such as electronic medical record information, surgical information, etc. As another example, the remote computing device 142 may, in addition to or as an alternative, include a remote monitoring server that records status information about the anesthesia machine 100. For example, the manufacturer or other service provider (e.g., a supplier) may remotely view the status information to anticipate maintenance requests and / or pre-order replacement parts, as will be referred to below. Figure 4 As detailed above. Therefore, in some examples, the remote computing device 142 may not be located in the same place as the anesthesia machine 100. The controller 140 may also be electronically coupled to various other components of the anesthesia machine 100, such as the anesthetic vaporizer 114, ABS 112, breathing gas module 108, anesthesia display device 104, and patient monitoring display device 106.

[0024] The controller 140 receives signals from various sensors of the anesthesia machine 100 and employs various actuators of the anesthesia machine 100 to regulate the operation of the anesthesia machine 100 based on the received signals and instructions stored in the controller's memory. For example, the flow of gas to the inspiratory port 118 may be controlled at least in part based on input received from a human-machine interface (HMI) 143, which is communicatively coupled to the electronic controller 140 of the anesthesia machine 100. For example, the HMI 143 may include a keyboard, a touchscreen, a mouse, and / or another type of input device that enables the operator to input commands or control parameters. The HMI 143 may also include one or more output devices, including a display screen, a speaker, etc., for transmitting messages or other information to the operator. The controller 140 may display the operating parameters of the anesthesia machine 100 via an anesthesia display device 104 and / or a patient monitoring display device 106. The controller may receive signals (e.g., electrical signals) via the HMI 143 and may adjust the operating parameters of the anesthesia machine 100 in response to the received signals.

[0025] For example, the operator can input the desired concentration of the anesthetic to be delivered to the patient via HMI 143. The corresponding valve positions of one or more valves of the anesthesia machine (e.g., the positions of one or more bypass valves, as described above) can be determined empirically and stored in a predetermined lookup table or function in the controller's memory. For example, the controller can receive the desired anesthetic concentration via an input device and can determine the opening amount of the one or more valves corresponding to the desired anesthetic concentration based on a lookup table, where the input is the anesthetic concentration and the output is the valve position of the one or more valves. The controller can transmit electrical signals to the actuators of the one or more valves to adjust each of the one or more valves to its corresponding output valve position. In some examples, for instance, the controller can compare the desired gas flow rate with the measured gas flow rate, such as via an inspiratory flow sensor.

[0026] Next, Figure 2 An exemplary embodiment of an advanced respiratory system (ABS) 200 is shown. As an example, the ABS 200 may include... Figure 1 The ABS 112 is included in the anesthesia machine 100. In other examples, the ABS 200 may be included in another medical gas flow system such as an incubator. Furthermore, the ABS 200 is an exemplary configuration of an advanced respiratory system, and other configurations including at least one oxygen sensor are also possible, as will be detailed below.

[0027] ABS 200 includes two ventilation systems for delivering gases (e.g., air, medical gases, and / or anesthetics) to a patient: an electrically operated ventilator 201 and a manually operated ventilator 203. The electrically operated ventilator 201 includes a bellows assembly 202 and a ventilator drive 204. The manually operated ventilator 203 includes a cuff 206 and an adjustable pressure limiting (APL) valve 212. A cuff / ventilator switch 208 controls the selection between the two ventilation systems. For example, when manually operated ventilator 203 (e.g., cuff ventilation) is selected at the cuff / ventilator switch 208, the cuff 206 and APL valve 212 are connected to the recirculatory system 210 via a bidirectional gas passage 216, while the bellows assembly 202 and ventilator drive 204 are disconnected. The cuff 206 can be manually compressed by the operator of ABS 200 to pump gas through the recirculatory system 210. In addition, waste gas exhaled by the patient can leave the recirculatory system 210 via APL valve 212 and can be guided to the purging system via purging channel 214.

[0028] When the electronically operated ventilator 201 is selected at the bag / ventilator switch 208, the bag 206 and APL valve 212 are disconnected from the bidirectional gas channel 216 and the recirculatory system 210, and the electronically operated ventilator 201 provides the patient with inhalation and exhalation. For example, the ventilator drive 204 may be controlled by a controller 240 (which may be, for example...) Figure 1 The controller 140 (a part of the controller) is electronically controlled to pneumatically compress the bellows within the bellows assembly 202 at a predetermined adjustable rate. Furthermore, exhaust gases can exit the recirculatory system 210 via the bellows assembly 202 and the ventilator drive 204, and can be guided to the scavenging system via the same scavenging channel 214. The scavenging system removes anesthetic agents, preventing their release into treatment rooms (such as operating rooms, wards, etc.).

[0029] The recirculatory breathing system 210 includes multiple gas channels coupled to a bidirectional gas passage 216, including an inspiratory passage 218 with an inspiratory check valve 220 coupled therein, an expiratory passage 222 with an expiratory check valve 224 coupled therein, and a patient delivery passage 226 with an airflow sensor 230 and a filter 232 coupled therein. The patient delivery passage 226 can deliver gases (e.g., air, medical gases, and / or anesthetics) from a selected ventilation system to a patient during inhalation (e.g., via the inspiratory passage 218 and the inspiratory check valve 220) and can deliver waste gases from the patient to a scavenging system during exhalation (e.g., via the expiratory passage 222 and the expiratory check valve 224). The airflow sensor 230 can measure the flow rate through the patient delivery passage 226 during inhalation and exhalation. However, in other examples, separate inhalation flow sensors and separate exhalation flow sensors may be included, such as one air flow sensor coupled to inhalation channel 218 and another air flow sensor coupled to exhalation channel 222.

[0030] exist Figure 2 In the example shown, gas passage 234 couples inhalation passage 218 to exhalation passage 222 and includes an absorption canister 236 coupled therein. Specifically, gas passage 234 is coupled upstream of inhalation check valve 220 to inhalation passage 218 and downstream of exhalation check valve 224 to exhalation passage 222. Inhalation check valve 220 is a one-way valve that automatically opens in response to patient inhalation and automatically closes in response to patient exhalation. Inhalation check valve 220 allows gas to flow (e.g., via gas passage 234 and inhalation passage 218) from bidirectional gas passage 216 to patient delivery passage 226 and blocks (e.g., prevents) gas from flowing from patient delivery passage 226 to gas passage 234. Similarly, exhalation-inhalation check valve 224 is a one-way valve that automatically opens in response to patient exhalation and automatically closes in response to patient inhalation. The expiratory check valve 224 allows gas to flow from the patient delivery channel 226 to the bidirectional gas channel 216 and blocks gas from flowing from the bidirectional gas channel 216 through the expiratory channel 222 back to the patient delivery channel 226. Therefore, all gas flowing to the patient flows through the inspiratory channel 218, and all gas flowing out of the patient flows through the expiratory channel 222. Exhaled waste gas from the patient can flow back (via the patient delivery channel 226 and the expiratory channel 222) to the selected ventilation system, where it can be recirculated.

[0031] Oxygen sensor 242 is coupled to inhalation channel 218 and configured to measure the amount (e.g., concentration or percentage) of oxygen in the gas flowing to the patient. According to the embodiments described herein, oxygen sensor 242 is an electroplated zinc oxygen sensor that generates an electrical output (e.g., output voltage) in the presence of oxygen, as will be referenced herein. Figure 3As detailed above. Therefore, the controller 240 can determine the oxygen concentration in the gas flowing to the patient via the patient delivery channel 226 based on the output voltage of the oxygen sensor 242. Although Figure 2 Oxygen sensor 242 is shown positioned downstream of inspiratory check valve 220, but in other examples, oxygen sensor 242 is positioned upstream of inspiratory check valve 220, such as between fresh gas inlet 228 and inspiratory check valve 220. Other locations of oxygen sensor 242 within ABS 200 are also possible without departing from the scope of this disclosure. For example, oxygen sensor 242 may be positioned at any location that allows monitoring of the concentration of oxygen delivered to the patient.

[0032] A fresh gas inlet 228 is positioned between the absorption canister 236 and the inspiratory check valve 220, such that the gas flow supplied to the inspiratory patient may include enriched fresh gas (e.g., from an anesthetic vaporizer, such as...). Figure 1 The mixture consists of an anesthetic vaporizer 114 and a wash gas (depending on the position of the cuff / ventilator switch 208) returned from the cuff 206 or bellows assembly 202 via an absorption canister 236. For example, the absorption canister 236 removes carbon dioxide from the patient's exhaled waste gas. The fresh gas inlet 228 may include one or more flow control valves, such as valve 238, for regulating the amount (e.g., flow rate or concentration) of enriched fresh gas supplied to the ABS 200 and thus to the patient. It should be understood that the enriched fresh gas may include one or more medical gases (e.g., oxygen, nitrogen, air, and nitrous oxide) with or without an anesthetic (e.g., depending on whether the patient is anesthetized). For example, valve 238 may be an electronically controlled continuously variable valve that can be actuated to multiple positions between fully open and fully closed in response to a command signal received from the controller 240. When valve 238 is actuated to a further open position, the enriched fresh gas flow through fresh gas inlet 228 increases, and when valve 238 is actuated to a further closed position, the enriched fresh gas flow through fresh gas inlet 228 decreases. In some examples, controller 240 may adjust the position of valve 238 based on feedback received from air flow sensor 230 and / or oxygen sensor 242.

[0033] Without departing from the scope of this disclosure, ABS 200 may include Figure 2 Additional valves, sensors, and gas inlets not shown, such as various pressure relief valves and / or regulating valves, pressure sensors, concentration sensors, and optional fresh gas inlets and / or oxygen inlets, are also included. Therefore, Figure 2 This can be understood as illustrating one implementation of an exemplary advanced respiratory system that can provide mechanical ventilation to a patient.

[0034] Figure 3A schematic cross-sectional view of an oxygen sensor 300 is shown, which may be, for example... Figure 2 Oxygen sensor 242. Oxygen sensor 300 includes a sensor body 302, an electrolyte 304, an anode (or working electrode) 306 surrounding a central portion of the sensor body 302, a cathode (or sensing electrode) 308 positioned at the top of the central portion of the sensor body 302, and a membrane 310. For example, the anode 306 may be made of a base metal (e.g., lead or zinc), while the cathode 308 may be made of a noble metal (e.g., gold or platinum). The electrolyte 304 may be an alkaline electrolyte solution or gel immersing the anode 306 and cathode 308. As an example, the electrolyte 304 may be a potassium hydroxide solution. Furthermore, in some examples, the electrolyte 304 may be buffered to make it resistant to pH changes.

[0035] Membrane 310 may form a diffusion barrier layer that limits or controls the amount of oxygen flowing from outside membrane 310 into oxygen sensor 300. Oxygen that permeates into membrane 310 and diffuses into oxygen sensor 300 dissociates and is reduced to hydroxyl ions at cathode 308. Membrane 310 provides a diffusion barrier layer that controls the amount of oxygen reaching the cathode to a level that can be completely reduced without significant delay. The hydroxyl ions generated at cathode 308 diffuse through electrolyte 304 and oxidize anode 306. This process generates a current flowing through a circuit formed between cathode 308, electrolyte 304, and anode 306, the amount of which is proportional to the amount of oxygen consumed at cathode 308, which is proportional to the amount of gas outside membrane 310 (e.g., partial pressure).

[0036] Therefore, the oxygen sensor 300 also includes a first wire 312 coupling the cathode 308 to the measurement circuit via a first port 316 and a second wire 314 coupling the anode 306 to the measurement circuit via a second port 318. The measurement circuit includes an instrument 320, which may be, for example, an ammeter configured to measure the current in the circuit or a voltmeter configured to measure the voltage across the cathode 308 and anode 306. The instrument 320 can transmit the voltage (or current) to a controller (e.g., Figure 2 The controller 240 can use its output voltage (or current) to determine the oxygen concentration in the gas outside the membrane 310 based on instructions stored in its memory. It should be noted that the oxygen sensor 300 may include fewer, alternative, or additional components such as a moisture barrier, filter, and circuit switch, and the example shown is an exemplary example of an electroplated zinc fuel cell type (e.g., electrochemical) oxygen sensor.

[0037] Because anode 306 is oxidized, it is consumed when the sensor (e.g., cathode 308) is exposed to oxygen-containing gas. Over time, the amount of unoxidized base metal at anode 306 decreases, and the amount of oxidized base metal increases accordingly. The amount of oxidized base metal increases until anode 306 is consumed (e.g., anode 306 is completely oxidized). When anode 306 is completely oxidized (e.g., all available surface area of ​​anode 306 is oxidized, with no remaining unoxidized surface area), the electrochemical reduction of oxygen at cathode 308 and the oxidation of anode 306 no longer occur. Therefore, the current (or voltage) output of oxygen sensor 300 decreases to zero, and oxygen sensor 300 no longer provides an output proportional to the amount of oxygen in the gas stream.

[0038] therefore, Figure 4 A sensor for monitoring oxygen, such as Figure 2 An exemplary method 400 for estimating the end-of-life (EOL) date of an oxygen sensor 242 based on its output. The oxygen sensor may be positioned in the gas flow channel of a medical gas flow device, such as... Figure 2 The inhalation channel 218 is shown. The medical gas flow device can be, for example, an anesthesia machine, a ventilator, or an incubator. Method 400 can be used to track the oxygen sensor output over time to identify changes in the output related to sensor aging (e.g., reduction) due to the consumption of the sensor anode, as described above. Method 400 can be controlled by a controller (such as...) Figure 1 Controller 140 and / or Figure 2 The controller 240) operates according to instructions stored in the controller's memory and in conjunction with one or more inputs such as from an oxygen sensor and / or a human-machine interface (e.g., Figure 1 The controller executes actions based on inputs received by the HMI 143. Additionally, the controller may employ actuators (e.g., Figure 2 The valve 238 is used to adjust the flow rate of medical gas according to the method described below.

[0039] At 402, method 400 includes calibrating an oxygen sensor. For example, the oxygen sensor may be periodically calibrated as part of the nominal maintenance procedure for a medical gas flow device. Calibrating the oxygen sensor includes obtaining an oxygen sensor reading (e.g., a measured value) at a first frequency with 21% oxygen (e.g., a first oxygen concentration), as indicated by 404, and obtaining an oxygen sensor reading at a second frequency with 100% oxygen (e.g., a second oxygen concentration), as indicated by 406. For example, a controller may perform a calibration routine to obtain oxygen sensor readings at 21% oxygen and at 100% oxygen. Because ambient air has approximately 21% oxygen, obtaining an oxygen sensor reading at 21% oxygen includes flowing air (e.g., medical air) through a gas flow passage and measuring the corresponding sensor voltage (or current) output, while obtaining an oxygen sensor reading at 100% oxygen includes flowing substantially pure oxygen (e.g., from a cylinder, supplied through a pipe, or generated via an oxygen compressor) through the gas flow passage and measuring the corresponding sensor voltage (or current) output. As an example, the controller may adjust the flow control valve and / or gas selector to allow air (e.g., the first gas) or pure oxygen (e.g., the second gas) to flow through the gas flow channel and thus to the oxygen sensor being calibrated during the calibration routine. In an alternative example, different gases and / or gas mixtures may be used for the first and second gases with different oxygen concentrations.

[0040] In at least some examples, during the calibration routine, 21% oxygen calibration may be performed more frequently than 100% oxygen calibration, making the first frequency greater than the second frequency. As an example, the first frequency could be weekly (e.g., every 7 days), and the second frequency could be monthly (e.g., every 30 days). For example, the second frequency could be lower than the first frequency to reduce the likelihood of exposing the oxygen sensor to pure oxygen. Therefore, in some examples, performing the calibration routine at 402 and calibrating the oxygen sensor results in two measurements at two different oxygen concentrations (e.g., one at 21% oxygen and the other at 100% oxygen), and in other examples, only one measurement is obtained at one oxygen concentration (e.g., 21% oxygen or 100% oxygen).

[0041] Furthermore, the calibration routine may include obtaining high-frequency oxygen sensor readings after initiating the flow of a gas of appropriate oxygen concentration (e.g., air or pure oxygen) through a gas flow channel, and may record oxygen sensor readings in response to the oxygen sensor output stabilizing. For example, the oxygen sensor output can be considered stable when the sensor output remains within a threshold range across multiple readings (e.g., 5-15 readings). The threshold range corresponds to a percentage deviation of the oxygen sensor output within which the oxygen sensor output remains substantially constant. As an example, obtaining high-frequency oxygen sensor readings may include obtaining multiple oxygen sensor readings per second, such as every 100-300 milliseconds. This reduces the amount of time spent calibrating the oxygen sensor, which in turn reduces the oxygen sensor's exposure to the gas used for calibration. Specifically, by reducing the oxygen sensor's exposure to pure oxygen, the oxygen sensor's lifespan can be extended.

[0042] At 408, method 400 includes determining whether at least one of the calibration readings (e.g., obtained at 404 and / or 406) is less than or equal to a degradation threshold. The degradation threshold is the calibrated oxygen sensor output voltage, below which the oxygen sensor can be assumed to be inoperable. Furthermore, the degradation threshold can be different for two different oxygen concentrations and can be manufacturer-specific. For example, the degradation threshold for the sensor reading at 100% oxygen can be higher than the degradation threshold for the sensor reading at 21% oxygen. As a non-limiting example, the degradation threshold for the sensor reading at 21% oxygen (e.g., a first degradation threshold) can be in the range of 1 mV–5 mV (e.g., 3 mV), and the degradation threshold for the sensor reading at 100% oxygen (e.g., a second degradation threshold) can be in the range of 8 mV–12 mV (e.g., 10 mV).

[0043] If at least one reading is less than or equal to the corresponding degradation threshold for the corresponding oxygen concentration, method 400 proceeds to 410 and includes outputting an oxygen cell degradation alarm. For example, the oxygen cell degradation alarm may be output via an HMI. For example, the oxygen cell degradation alarm may include one or more of a visual (e.g., text-based) message and an auditory message. The degradation alarm may indicate that the oxygen sensor is not functioning and recommend, for example, immediate replacement. Method 400 then terminates.

[0044] Returning to 408, if no reading is less than or equal to the corresponding degradation threshold, method 400 proceeds to 412 and includes storing the oxygen sensor calibration readings by date. For example, each oxygen sensor calibration reading can be timestamped according to the date and time it was recorded and entered into a calibration log, which can be stored in the controller's memory. Thus, each calibration reading can be used as a calibration time point. In some examples, each calibration concentration uses a separate calibration log, such as 21% oxygen using a first calibration log and 100% oxygen using a second calibration log. In other examples, the timestamped oxygen sensor calibration readings for 21% oxygen and 100% oxygen are stored together with the oxygen concentration in a single calibration log. Furthermore, in some examples, the timestamped oxygen sensor calibration readings for 21% oxygen and 100% oxygen can be normalized to account for different output voltages at different oxygen concentrations, as will be discussed below (e.g., at 426) and referenced. Figure 5 As detailed above. In such examples, both raw data (e.g., measured sensor output voltage) and normalized data are stored in a calibration log. The calibration log may include one or more forms, such as tables and graphs.

[0045] At 414, method 400 includes determining whether the calibration is an initial calibration. If the calibration is the first calibration performed for the installed oxygen sensor (e.g., a first calibration routine performed for the installed oxygen sensor), then the calibration can be considered an initial calibration. As an example, if the reading is at least a threshold percentage greater than the last stored reading at a given oxygen concentration, the controller can determine that the calibration performed at 402 is an initial calibration. The threshold percentage is a non-zero percentage (e.g., 10%) that distinguishes the nominal fluctuation of the oxygen sensor output from the increase in output due to the increased electrochemical activity of the new sensor. Alternatively, the controller may receive input from the operator (e.g., via an HMI) confirming the installation of a new oxygen sensor.

[0046] If the calibration is an initial calibration, method 400 proceeds to 416 and includes storing the oxygen sensor calibration reading as the initial reading. Because the calibration is an initial calibration, the oxygen sensor calibration reading at a given oxygen concentration is the first and only recorded output voltage of the oxygen sensor. Therefore, the current calibration reading cannot be compared with the previously stored reading to track the sensor output over time, and method 400 ends. For example, method 400 can be repeated at a first frequency and a second frequency to perform subsequent oxygen sensor calibrations at two different oxygen concentrations.

[0047] If the calibration was not the initial calibration, method 400 proceeds to 420 and includes determining whether at least one of the readings is at least a threshold amount corresponding to the oxygen percentage from the initial calibration. The threshold amount is a predetermined value or percentage change from the initial calibration. When the oxygen sensor output has changed by at least a threshold amount from the initial calibration, it can be assumed that the oxygen sensor is beginning to approach the end of its lifespan. For example, the threshold amount can distinguish between nominal fluctuations in the sensor output and a decrease in output due to a reduction in the electrochemical activity of the oxygen sensor, which occurs as the available surface area of ​​the unoxidized anode decreases. As an example, the threshold amount is 20%.

[0048] If none of the readings are from at least a threshold amount of the initial calibration (e.g., the calibration reading obtained at 402 is within a threshold amount from the initial calibration), then method 400 proceeds to 422 and includes continuing to track the oxygen sensor calibration readings over time. Reference will be made below. Figure 5 As shown, the oxygen sensor output remains relatively stable for a period of time after installation, and therefore the end of the oxygen sensor's lifespan does not need to be estimated because there is no significant change in the oxygen sensor output. However, each calibration reading continues to be stored in the calibration log. Then, method 400 ends.

[0049] If at least one reading is at least a threshold amount from the initial calibration (e.g., the calibration reading obtained at 402 has been reduced by a threshold amount from the initial calibration), then method 400 proceeds to 424 and includes determining the rate of change of the sensor reading using the most recently previously recorded calibration for the corresponding oxygen percentage for each obtained calibration reading. The rate of change can be determined as the difference between the current oxygen sensor reading for a given oxygen percentage and the most recently previously obtained oxygen sensor calibration reading divided by the amount of time elapsed between the current reading and the previous reading (e.g., the frequency used for calibration). Thus, the rate of change is equal to the slope of the reduction in measurement between two consecutive calibration measurements (e.g., for a given oxygen concentration, the current calibration measurement and the previous calibration measurement immediately preceding the current calibration measurement).

[0050] Determining the rate of change also includes normalizing the rate of change for each oxygen percentage, as indicated at 426. Normalizing the rate of change for each oxygen percentage converts the data to the same scale, allowing data from a 21% oxygen calibration to be combined with data from a 100% oxygen calibration, as detailed below. For example, the controller can normalize the rate of change for the 21% oxygen calibration and the rate of change for the 100% oxygen calibration by scaling each value according to instructions stored in memory. For example, the controller can normalize sensor measurements according to a known normalization formula and then use the normalized measurements to determine the normalized rate of change.

[0051] At 428, method 400 includes estimating the end-of-life date of the oxygen sensor using the determined rate of change. The end-of-life date refers to a time quantity, such as days or weeks, until the expected sensor output decreases to zero due to the complete consumption of the anode at a given current rate of sensor output reduction. For example, the controller can extrapolate the end-of-life date using the current calibration reading and the corresponding rate of change. As mentioned above, in some examples, the controller can combine the normalized rate of change from the 21% oxygen calibration and the normalized rate of change from the 100% oxygen calibration, which can increase the accuracy of the determined end-of-life date. Furthermore, in some examples, the controller can use a weighted average to combine the rates of change from the 21% oxygen calibration and the 100% oxygen calibration. For example, the rate of change from the 21% oxygen calibration can be given a greater weight than the rate of change from the 100% oxygen calibration because the oxygen concentration in the air may be more consistent than in substantially pure oxygen, which may have a higher rate of contamination (especially when oxygen is generated via an oxygen compressor). In some examples, in addition to or alternatively, the controller may separately determine the end-of-life dates for the 21% oxygen calibration and the 100% oxygen calibration, and then combine the determined end-of-life dates by averaging these values ​​(e.g., a weighted average or an unweighted average). By combining the information given by the 21% oxygen calibration and the 100% oxygen calibration, a larger number of data points can be used, which increases the accuracy of the estimated end-of-life date.

[0052] At 430, method 400 optionally includes transmitting the estimated end-of-life date to a remote server. The remote server can be communicatively connected to the controller via wired or wireless communication. The remote server can be monitored by the administrator of the medical gas flow device (e.g., personnel or department that schedules the supply, ordering, and maintenance of the medical gas flow device) and / or the oxygen sensor supplier. Therefore, by transmitting the end-of-life date to the remote server, the administrator and / or the oxygen sensor supplier may be able to anticipate the oxygen sensor replacement time. Because oxygen sensors cannot be stored for extended periods, transmitting the oxygen sensor replacement time reduces both over-ordering (which can lead to increased costs) and under-ordering (which can lead to downtime of the medical gas flow device).

[0053] At 432, method 400 includes determining whether the estimated end-of-life date is less than a threshold duration. The threshold duration is a predetermined non-zero duration stored in the controller's memory that, if not ordered immediately, may prevent oxygen sensor replacement before the current oxygen sensor ceases operation. As a non-limiting example, the threshold duration is 15 days.

[0054] If the estimated end-of-life date is not less than a threshold duration, method 400 proceeds to 434 and includes outputting a lower-priority oxygen sensor replacement notification (e.g., a first oxygen sensor replacement notification). Because there is still a time buffer before the end-of-life date, the lower-priority notification can be a text-based (e.g., visual) message output to the HMI's display, for example, containing instructions to replace the oxygen sensor within 90 days. In some examples, the estimated end-of-life date may be displayed and decreased daily. Furthermore, the end-of-life date may be updated when a new calibration reading is obtained. Method 400 then terminates. For example, at least a portion of method 400 may be repeated daily to determine whether the estimated end-of-life date has decreased below the threshold duration.

[0055] Returning to 432, if the estimated end-of-life date is less than a threshold duration, method 400 proceeds to 436 and includes outputting a higher-priority oxygen sensor replacement notification (e.g., a second oxygen sensor replacement notification). The higher-priority notification may include both a text-based visual message and an audible alarm and / or message output via the HMI. The higher-priority notification may suggest, for example, replacing the oxygen sensor within 15 days. Furthermore, the estimated end-of-life data may be displayed on the HMI's screen and decrease daily. Additionally, in some examples, the controller may communicate with a remote server to automatically submit an oxygen sensor replacement order and / or request an oxygen sensor replacement (e.g., if not already ordered) in response to the estimated end-of-life date decreasing below the threshold duration. Method 400 then terminates.

[0056] In this way, the end-of-life date of an oxygen sensor can be predicted based on changes in its output. Since the time spent consuming the anode of each oxygen sensor varies based on, for example, oxygen exposure conditions, determining the end-of-life date based on the sensor's own output allows for sensor replacement when the sensor is no longer needed. Replacing the sensor when it is no longer needed, rather than pre-replacing it (e.g., based on average consumption time), reduces the cost of oxygen sensors. Furthermore, predicting the end-of-life date of oxygen sensors makes replacement parts readily available, thereby reducing downtime in medical gas flow devices due to the absence of oxygen sensors.

[0057] Next, Figure 5 An exemplary graph 500 is shown, which tracks oxygen sensor calibration measurements over time and extrapolates the end-of-life date based on changes in these measurements. The oxygen sensor is included in the gas flow channel of a medical gas flow device, such as... Figure 2 The oxygen sensor 242 of the ABS 200 is shown. Furthermore, the oxygen sensor calibration measurements can be controlled by a controller (such as...). Figure 2The controller 240 tracks the oxygen levels. Curve 502, represented by a thinner solid line and a smaller solid circle, shows the calibration measurement for 21% oxygen (e.g., a first oxygen concentration), and curve 504, represented by a thicker dashed line and a larger solid circle, shows the calibration measurement for 100% oxygen. Each solid circle represents a measurement at a calibration time point at the corresponding oxygen concentration. Graph 500 includes time as the horizontal axis and normalized oxygen sensor output voltage on the vertical axis, allowing measurements from the 21% oxygen calibration (curve 502) and the 100% oxygen calibration (curve 504) to be displayed on graph 500. Therefore, in the example shown, the initial calibration measurement for each oxygen percentage obtained at time t0 is set to the same value.

[0058] In the example shown, 21% oxygen calibration measurements (curve 502) are obtained at a higher frequency than the 100% oxygen calibration measurement (curve 504). Specifically, a first duration Δt1 passes between each 21% oxygen (e.g., a first oxygen concentration) calibration measurement, and a second duration Δt2 passes between each 100% oxygen (e.g., a second oxygen concentration) calibration measurement. Therefore, a 21% oxygen calibration measurement is obtained every first duration Δt1, and a 100% oxygen calibration measurement is obtained every second duration Δt2. In this example, Δt2 is four times longer than Δt1. For example, Δt1 could be one week (e.g., 7 days), and Δt2 could be four weeks (e.g., 28 days).

[0059] Graph 500 also shows a threshold 506, which corresponds to the threshold value from the above relative to the threshold value. Figure 4 The initial calibration threshold amount described in 420. Therefore, the normalized oxygen sensor output voltage above threshold 506 is tracked without estimating the end-of-life date of the oxygen sensor, as the oxygen sensor output remains relatively high. In the example shown, the normalized oxygen sensor output remains substantially unchanged compared to the initial calibration readings obtained at t0 for the first thirteen measurements at 21% oxygen (curve 502) and the first four measurements at 100% oxygen (curve 504). At time t1, the 21% oxygen calibration measurement begins to decrease (curve 502) but remains above threshold 506. Therefore, the end-of-life date is not estimated at time t1.

[0060] However, the 21% oxygen calibration measurement obtained at time t2 (curve 502) is less than the threshold 506. In response, the controller estimates the end-of-life date of the oxygen sensor based on the rate of change of the oxygen sensor output between the most recently previously recorded 21% oxygen reading (e.g., obtained at time t1) and the current reading (e.g., obtained at time t2). The controller extrapolates this rate of change to the slope of line 508 to determine when the oxygen sensor output will decrease to zero. The resulting end-of-life date estimate, EOL1, is shown. 21％The line 508 intersects the horizontal axis.

[0061] Between time t2 and time t3, 21% oxygen calibration measurements are continuously acquired every Δt1. The controller updates the estimated end-of-life date based on the new rate of change calculated between each current measurement and the previously recorded 21% oxygen calibration measurement. However, between time t2 and time t3, the rate of change, and therefore the estimated end-of-life date, remains unchanged and remains at EOL1. 21％ .

[0062] At time t3, a first 100% oxygen calibration measurement (curve 504) is obtained that is less than the threshold 506. In response, the controller estimates the end-of-life date based on the rate of change between the current 100% oxygen calibration measurement (e.g., obtained at time t3) and the most recently previously obtained 100% oxygen calibration measurement (e.g., obtained shortly before time t1). The controller extrapolates this rate of change to the slope of line 510 to determine when the oxygen sensor output will decrease to zero. The resulting end-of-life date estimate, EOL1, is shown. 100％ Line 510 intersects the horizontal axis. EOL1 100％ Later than EOL1 21％ EOL1 21％ It is not based on the 21% oxygen calibration measurement obtained at t3. Therefore, in some examples, the controller is adjusted for EOL1. 21％ and EOL1 100％ Average the values ​​to increase the accuracy of end-of-life date estimates. Additionally, due to the potential increased accuracy of the 21% oxygen calibration measurements, the average can be averaged towards EOL1. 21％ Weighted.

[0063] At time t4, the rate of change between the current 21% oxygen calibration measurement (e.g., obtained at time t4) and the most recent previous 21% oxygen calibration measurement (e.g., obtained between time t3 and time t4) changes. For example, the rate of anode consumption of the oxygen sensor may change due to variations in the total amount of oxygen exposed to the oxygen sensor between the 21% oxygen calibration measurements. The controller estimates the updated end-of-life date EOL2 by extrapolating line 512 based on the new rate of change between the 21% oxygen calibration measurements. 21％ EOL2 21％ It is later than EOL1 21％ The date, and can be compared with EOL1 as described above. 100％ Take an average.

[0064] A new 100% oxygen calibration measurement is obtained after time t4. The rate of change between the current 21% oxygen calibration measurement (obtained just after time t4) and the previous 21% oxygen calibration measurement (obtained at time t3) differs, resulting in the updated estimated end-of-life date EOL2 from the intersection of the horizontal axis and line 514. 100％ The line includes an updated slope to reflect the new rate of change in the oxygen sensor output. EOL2 100％ Compared to EOL1 100％ Early, and compared to EOL1 100％ With EOL1 21％ Proximity, EOL2 100％ Closer to EOL2 21％ Therefore, in at least some examples, data from both the 21% oxygen calibration measurement (curve 502) and the 100% oxygen sensor calibration measurement (curve 504) can be converged when more data becomes available.

[0065] Therefore, the systems and methods described herein provide accurate estimation of the end-of-life date of oxygen sensors in medical devices. Specifically, because each oxygen sensor will deplete at a different rate depending on its specific oxygen exposure conditions, the systems and methods described herein enable the determination of the end-of-life date of each oxygen sensor based on its own output. This allows for timely ordering of oxygen sensor replacements, reducing downtime of medical devices due to oxygen sensor malfunction. Furthermore, premature replacement of oxygen sensors can be reduced, lowering maintenance costs for medical devices. Additionally, by transmitting oxygen sensor status information to a remote server that can be monitored by the oxygen sensor manufacturer / supplier, oxygen sensor manufacturing logistics can be coordinated more effectively, enabling oxygen sensor manufacturing to more closely meet demand and reducing sensor shelf time. Overall, this improves customer satisfaction.

[0066] The advantage of using calibration readings of oxygen sensors to estimate the end-of-life date of oxygen sensors in medical devices is that oxygen sensors can be used until they are essentially depleted, while reducing downtime of medical devices due to unexpected oxygen sensor depletion.

[0067] In one embodiment, a method for a medical gas flow device includes: tracking the output of an oxygen sensor over time during calibration; and estimating the end-of-life date of the oxygen sensor and outputting a replacement notification in response to the output decreasing from an initial calibration output by at least a threshold amount. In examples, tracking the output of the oxygen sensor over time during calibration includes calibrating the oxygen sensor at a first oxygen concentration at a first frequency and at a second oxygen concentration at a second frequency less than the first frequency. In some examples, the first oxygen concentration is less than the second oxygen concentration, and tracking the output of the oxygen sensor over time during calibration further includes: obtaining a high-frequency sensor reading when a first gas having a first oxygen concentration is flowed through the medical gas flow device, and recording the output of the oxygen sensor as a first oxygen concentration calibration measurement in response to the output of the oxygen sensor stabilizing during the high-frequency sensor reading period; and obtaining a high-frequency sensor reading when a second gas having a second oxygen concentration is flowed through the medical gas flow device, and recording the output of the oxygen sensor as a second oxygen concentration calibration measurement in response to the output of the oxygen sensor stabilizing during the high-frequency sensor reading period. In one example, estimating the end-of-life date of an oxygen sensor involves averaging a first end-of-life date determined based on a first oxygen concentration calibration measurement and a second end-of-life date determined based on a second oxygen concentration calibration measurement.

[0068] In some examples, the end-of-life date is the date the oxygen sensor's output decreases to zero, and estimating the end-of-life date of the oxygen sensor includes: determining the rate of change of the oxygen sensor's output during calibration; and extrapolating the end-of-life date using the rate of change. In one example, determining the rate of change of the oxygen sensor's output during calibration includes: determining the difference between the oxygen sensor's output at the current calibration time point and the oxygen sensor's output at a previous calibration time point immediately preceding the current calibration time point; and dividing that difference by the amount of time between the previous calibration time point and the current calibration time point. In the example, output replacement notification includes: outputting a first notification with lower priority in response to the end-of-life date being greater than a threshold duration; and outputting a second notification with higher priority in response to the end-of-life date being less than a threshold duration. For example, the first notification may consist only of a visual message, and the second notification may include both a visual message and an auditory message.

[0069] In one example, the method also includes transmitting the end-of-life date to a remote monitoring server that is communicatively coupled to the medical gas flow device.

[0070] In another embodiment, the method for an anesthesia machine includes: calibrating an oxygen sensor, including obtaining oxygen sensor readings at one or more oxygen concentrations; estimating an end-of-life date of the oxygen sensor in response to the oxygen sensor reading being at least a threshold amount from an initial calibration reading; outputting a first replacement notification in response to the end-of-life date being greater than a threshold duration; and outputting a second replacement notification in response to the end-of-life date being less than a threshold duration. In examples, obtaining oxygen sensor readings at one or more oxygen concentrations includes obtaining a first oxygen sensor reading at a first oxygen concentration and obtaining a second oxygen sensor reading at a second oxygen concentration greater than the first oxygen concentration. In some examples, estimating the end-of-life date includes: estimating a first end-of-life date based on a first rate of change of the first oxygen sensor reading between a current calibration at the first oxygen concentration and a most recent previous calibration; estimating a second end-of-life date based on a second rate of change of the second oxygen sensor reading between a current calibration at the second oxygen concentration and a most recent previous calibration; and determining the end-of-life date based on at least one of the first end-of-life date and the second end-of-life date. In one example, determining the end-of-life date based on at least one of a first end-of-life date and a second end-of-life date includes one of the following: selecting a first end-of-life date, averaging the first end-of-life date and the second end-of-life date, and performing a weighted average of the first end-of-life date and the second end-of-life date.

[0071] In one example, the threshold amount is a predetermined percentage of the initial calibration reading. In one example, outputting a first replacement notification includes outputting a visual message to a display, and outputting a second replacement notification includes outputting a visual message to a display and outputting an audible alarm via a speaker.

[0072] In one example, the method also includes: submitting an oxygen sensor replacement order to a remote server in response to the end-of-life date being less than a threshold duration.

[0073] In another embodiment, the system for a medical gas flow device includes: an inspiratory flow channel configured to allow gas to flow from a gas source to a patient breathing circuit; an oxygen sensor located in the inspiratory flow channel; and a controller including instructions stored in a non-transitory memory that, when executed, cause the controller to: record the output voltage of the oxygen sensor during a calibration routine performed at a predetermined frequency; and monitor the depletion of the oxygen sensor by tracking the output voltage recorded during the calibration routine over time.

[0074] In one example, the oxygen sensor is an electroplated zinc oxygen sensor, which includes an anode and a cathode immersed in an electrolyte that electrically couples the anode to the cathode, and measurement circuitry electrically coupled to the anode and cathode.

[0075] In some examples, to monitor oxygen sensor depletion by tracking the output voltage recorded during a calibration routine over time, the controller also includes instructions stored in non-transitory memory that, when executed, cause the controller to extrapolate the end-of-life date of the oxygen sensor based on the change in output voltage between consecutive executions of the calibration routine, in response to a threshold decrease in output voltage from the initial output voltage of the oxygen sensor recorded during a first calibration routine. In one example, the system also includes a human-machine interface communicatively coupled to the controller, the interface including a display and a speaker, and the controller includes additional instructions stored in non-transitory memory that, when executed, cause the controller to: output a lower-priority oxygen sensor replacement notification via the human-machine interface in response to an extrapolated end-of-life date exceeding a threshold duration, the lower-priority oxygen sensor replacement notification including a text-based instruction displayed on the display; and output a higher-priority oxygen sensor replacement notification via the human-machine interface in response to an extrapolated end-of-life date less than a threshold duration, the higher-priority oxygen sensor replacement notification including both a text-based instruction displayed on the display and an auditory message transmitted via the speaker.

[0076] As used herein, elements or steps listed in the singular and beginning with the word "a" or "an" should be understood to not exclude multiple said elements or steps unless such exclusion is explicitly stated. Furthermore, references to "an embodiment" of the invention are not intended to be construed as excluding the existence of additional embodiments that also include the referenced features. Moreover, unless explicitly stated to the contrary, embodiments that "comprise," "include," or "have" elements or multiple elements having a particular characteristic may include additional such elements that do not have that characteristic. The terms "comprise" and "in..." are used as concise linguistic equivalents to the corresponding terms "comprising" and "wherein". Furthermore, the terms "first," "second," and "third," etc., are used merely as notations and are not intended to impose numerical requirements or a particular order of position on their objects.

[0077] This written description uses examples to disclose the invention, including the best mode, and also enables those skilled in the art to practice the invention, including making and using any device or system and performing any included methods. The scope of patentability of the invention is defined by the claims and may include other examples that would occur to those skilled in the art. Such other examples are intended to fall within the scope of the claims if they have structural elements that are not indistinguishable from the literal language of the claims, or if they include equivalent structural elements that differ only slightly from the literal language of the claims.

Claims

1. A method for a medical gas flow device, the method comprising: Track oxygen sensor readings over time during calibration; as well as In response to the reading decreasing by at least a threshold amount from the initial calibration output, the end-of-life date of the oxygen sensor is estimated and a replacement notification is output. The process of tracking the oxygen sensor readings over time during the calibration period includes calibrating a first reading of the oxygen sensor at a first oxygen concentration at a first frequency, and calibrating a second reading of the oxygen sensor at a second oxygen concentration at a second frequency less than the first frequency. The estimated end-of-life date of the oxygen sensor includes: The first lifespan end date is estimated based on the first rate of change of the first reading at the first oxygen concentration between the current calibration and the most recent previous calibration. The second lifetime end date is estimated based on the second rate of change of the second reading at the second oxygen concentration between the current calibration and the most recent previous calibration; and The lifespan end date is determined based on at least one of the first lifespan end date and the second lifespan end date.

2. The method of claim 1, wherein the first oxygen concentration is less than the second oxygen concentration, and wherein tracking the readings of the oxygen sensor over time during the calibration period further comprises: When a first gas having the first oxygen concentration is flowed through the medical gas flow device, a high-frequency sensor reading is obtained, and in response to the oxygen sensor reading stabilizing during the high-frequency sensor reading, the oxygen sensor reading is recorded as a first oxygen concentration calibration measurement. as well as When a second gas having the second oxygen concentration is flowed through the medical gas flow device, a high-frequency sensor reading is obtained, and in response to the oxygen sensor reading stabilizing during the high-frequency sensor reading period, the oxygen sensor reading is recorded as a second oxygen concentration calibration measurement.

3. The method of claim 2, wherein estimating the end-of-life date of the oxygen sensor comprises averaging a first end-of-life date determined based on the first oxygen concentration calibration measurement and a second end-of-life date determined based on the second oxygen concentration calibration measurement.

4. The method of claim 1, wherein the end-of-life date is the date on which the reading of the oxygen sensor decreases to zero. And estimating the first end-of-life date of the oxygen sensor includes: Determine a first rate of change of the first reading of the oxygen sensor during the calibration period; as well as Extrapolate the first lifespan end date using the first rate of change. And estimating the second end-of-life date of the oxygen sensor includes: Determine a second rate of change of the second reading of the oxygen sensor during the calibration period; as well as The second rate of change is used to extrapolate the second lifespan end date.

5. The method of claim 4, wherein determining the first rate of change of the first reading of the oxygen sensor during the calibration period comprises: Determine the difference between the first reading of the oxygen sensor at the current calibration time point and the first reading of the oxygen sensor at a previous calibration time point immediately preceding the current calibration time point; as well as Divide the difference by the amount of time between the previous calibration time point and the current calibration time point. The determination of the second rate of change of the second reading of the oxygen sensor during the calibration period includes: Determine the difference between the second reading of the oxygen sensor at the current calibration time point and the second reading of the oxygen sensor at a previous calibration time point immediately preceding the current calibration time point; as well as Divide the difference by the amount of time between the previous calibration time point and the current calibration time point.

6. The method of claim 1, wherein outputting the replacement notification comprises: A first notification with lower priority is output in response to the end-of-life date being greater than a threshold duration. as well as A second notification with higher priority is output in response to the end-of-life date being less than the threshold duration.

7. The method of claim 6, wherein the first notification comprises only visual messages, and the second notification comprises both visual and auditory messages.

8. The method of claim 1 further includes transmitting the end-of-life date to a remote monitoring server communicatively coupled to the medical gas flow device.

9. A method for an anesthesia machine, the method comprising: Calibrate the oxygen sensor, including oxygen sensor readings obtained at one or more oxygen concentrations; In response to the oxygen sensor reading being at least a threshold amount from the initial calibration reading, the end-of-life date of the oxygen sensor is estimated; A first replacement notification is output in response to the end-of-life date being greater than a threshold duration; and A second replacement notification is output in response to the end-of-life date being less than the threshold duration. Obtaining the oxygen sensor reading at one or more oxygen concentrations includes obtaining a first oxygen sensor reading at a first oxygen concentration at a first frequency and obtaining a second oxygen sensor reading at a second oxygen concentration greater than the first oxygen concentration at a second frequency less than the first frequency. The estimated end-of-life date includes: The first end-of-life date is estimated based on the first rate of change of the first oxygen sensor reading at the first oxygen concentration between the current calibration and the most recent previous calibration. The second lifespan end date is estimated based on a second rate of change of the second oxygen sensor reading at the second oxygen concentration between the current calibration and the most recent previous calibration; and The lifespan end date is determined based on at least one of the first lifespan end date and the second lifespan end date.

10. The method of claim 9, wherein determining the end-of-life date based on at least one of the first end-of-life date and the second end-of-life date comprises one of: selecting the first end-of-life date, averaging the first end-of-life date and the second end-of-life date, and performing a weighted average of the first end-of-life date and the second end-of-life date.

11. The method of claim 9, wherein the threshold amount is a predetermined percentage of the initial calibration reading.

12. The method of claim 9, wherein outputting the first replacement notification includes outputting a visual message to a display, and outputting the second replacement notification includes outputting the visual message to the display and outputting an auditory alarm via a speaker.

13. The method of claim 9, further comprising: In response to the end-of-life date being less than the threshold duration, an oxygen sensor replacement order is submitted to the remote server.

14. A system for a medical gas flow device, the system comprising: An inspiratory flow channel, the inspiratory flow channel being configured to allow gas to flow from a gas source into the patient's breathing circuit; An oxygen sensor is positioned in the inspiratory flow channel; and The controller includes instructions stored in non-transitory memory, which, when executed, cause the controller to: The output voltage of the oxygen sensor is recorded during a calibration routine performed at a predetermined frequency; as well as The oxygen sensor's depletion is monitored by estimating its end-of-life date by tracking the output voltage recorded during the calibration routine over time. The process of tracking the output of the oxygen sensor over time during the calibration routine includes calibrating a first output voltage of the oxygen sensor at a first oxygen concentration at a first frequency, and calibrating a second output voltage of the oxygen sensor at a second oxygen concentration at a second frequency less than the first frequency. Monitoring the depletion of the oxygen sensor includes: The first end-of-life date is estimated based on the first change in the first output voltage at the first oxygen concentration between the current calibration and the most recent previous calibration. The second lifetime end date is estimated based on the second rate of change of the second output voltage at the second oxygen concentration between the current calibration and the most recent previous calibration; and The lifespan end date is determined based on at least one of the first lifespan end date and the second lifespan end date.

15. The system of claim 14, wherein the oxygen sensor is an electroplated zinc oxygen sensor, the electroplated zinc oxygen sensor comprising an anode and a cathode immersed in an electrolyte, the electrolyte electrically coupling the anode to the cathode, and a measuring circuit electrically coupled to the anode and the cathode.

16. The system of claim 14, wherein, in order to monitor the depletion of the oxygen sensor by tracking the output voltage recorded during the calibration routine over time, the controller includes additional instructions stored in a non-transitory memory, which, when executed, cause the controller to: In response to the first output voltage decreasing by a threshold from the initial output voltage of the oxygen sensor recorded during the first calibration routine, a first end-of-life date of the oxygen sensor is extrapolated based on the change in the first output voltage between consecutive executions of the calibration routine; and In response to the second output voltage decreasing by a threshold from the initial output voltage of the oxygen sensor recorded during the first calibration routine, a second end-of-life date of the oxygen sensor is extrapolated based on the change in the second output voltage between consecutive executions of the calibration routine.

17. The system of claim 14, further comprising a human-machine interface communicatively coupled to the controller, the human-machine interface including a display and a speaker, and wherein the controller includes additional instructions stored in a non-transitory memory, the instructions causing the controller, when executed, to: In response to the determined end-of-life date being greater than a threshold duration, a low-priority oxygen sensor replacement notification is output via the human-machine interface, the low-priority oxygen sensor replacement notification including a text-based instruction displayed on the display; and In response to the determined end-of-life date being less than the threshold duration, a higher-priority oxygen sensor replacement notification is output via the human-machine interface. The higher-priority oxygen sensor replacement notification includes both a text-based instruction displayed on the display and an auditory message transmitted via the speaker.

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