Patent Description:
Nitrous oxide (N<NUM>O) and oxygen (O<NUM>) are used for anxiety relief, pain relief and anesthesia in a variety of dental and medical procedures. These gases are commonly delivered by a gas flow meter ("flowmeter" or "mixer") which accepts O<NUM> and N<NUM>O gas from outside sources, mixes the gases according to the direction of the anesthesia operator, and then delivers the mixed gases to the patient.

One risk to patients with this form of anesthesia occurs if the oxygen flow is too low, or the flow of nitrous oxide is too high, as either can lead to oxygen deprivation. The primary cause of oxygen deprivation in nitrous oxide anesthesia settings occurs due to an improper crossover/cross-connection of supply lines, where the flowmeter receives nitrous oxide or some other non-oxygen gas into its oxygen intake. The flowmeter treats this gas as if it was oxygen, which may lead an anesthesia operator to deliver <NUM>% nitrous oxide even though the operator may intend to deliver <NUM>% O<NUM>. Unfortunately, this outcome has not been eliminated by current types of safety precautions and devices, leading to serious injuries and sometimes deaths of patients.

This dangerous outcome may be caused by building gas supply pipes not being installed correctly and not verified by a safety inspector, improper fittings being installed on the gas supply hoses, or other erroneous events. For instance, different and incompatible gas fittings are designed for use with oxygen and nitrous oxide supply lines and inlets to identify (and restrict) the different sources of gas. However, this measure fails if a user mistakenly installs an oxygen fitting onto a nitrous oxide supply hose, which can cause the nitrous oxide line to be connected into an oxygen inlet of a flowmeter. Likewise, many anesthesia flowmeters that are designed for use with nitrous oxide include an oxygen "failsafe" component usable with the flowmeter to stop the flow of nitrous oxide if oxygen gas is not flowing. However, this failsafe component simply measures the presence of gas pressure or flow in the oxygen line, and the failsafe component cannot tell if the gas that is being measured is actually oxygen. Thus, if the lines are crossed prior to entering the failsafe, the flowmeter will operate as if it is delivering pure oxygen, when the flowmeter is actually delivering nitrous oxide or another non-oxygen gas. <CIT>, <CIT>, <CIT> and <CIT> disclose known verifying and control systems for supplying anesthesia gases.

The document <CIT> Al discloses a safety device against the inversion of branchings in gasmixing apparatuses used in anaesthesia and assisted breathing. For each gas supplied, the device contains a unit for delayed switching which is sensitive to the density of the gas actually supplied. The set of switching units control, in decreasing order of the said densities, the order in which a variation of the pressure is produced in the various connecting pipes linking the switching units to a switching valve. This valve is open in order to provide communication between all the pipes of the mixing apparatus between the supply and the end-use when and only when the connecting pipe corresponding to the theoretically lightest gas is subjected first to the said pressure variation. The opening of the valve interrupts the supply from at least one of the gas supply pipes of the mixing apparatus, and sends it to a pressure detector controlling an alarm.

The document <CIT> discloses a system for verifying the supply of gases to surgery appliances, in particular to anaesthetizing apparatus comprising two inlet pipelines in receipt of two gases under pressure. The pressure of one of the two gases is reduced upstream of the inlet lines to a predetermined value different from that of the other gas. The apparatus comprises pressure sensing means associated at least with the inlet line in receipt of gas at the reduced pressure, designed to inhibit the operation of the apparatus and/or to activate error detection means on sensing a pressure value different to the predetermined value produced by the reduction upstream of the inlet lines.

The document <CIT> discloses a gas supply system comprising: a first gas source regulated at a pressure P1; a second gas source regulated at a pressure P2; an apparatus having a first inlet intended for connection to the first gas source and a second inlet intended for connection to the second gas source, means for mixing the two gases in selected proportions, and an outlet for the gas mixture; there being provided between the mixing means and outlet of said apparatus a cut-out valve sensitive to the gas pressure supplied to the first inlet and adapted to prevent the supply of the gas mixture to the outlet when the gas pressure supplied to said first inlet is below a predetermined value P3; and demountable means for connecting said sources to respective inlets of the apparatus; all wherein P1 is substantially greater than P2 and P3 is intermediate P1 and P2.

The present invention provides apparatus for verifying input gases used in anesthesia gas control equipment as claimed in claim <NUM>.

Disclosed herein is an apparatus and associated methods for analyzing the characteristics of a gas being delivered via a gas line, configured for distinguishing between oxygen and nitrous gas lines or other situations where delivery of multiple gases is involved. The analysis of the gas may include the use of a sampling technique to perform a measurement of a controlled leak under pressure from a designated chamber. The technique can include the observation and comparison of leak times for a first gas (e.g., nitrous oxide) and a second gas (e.g., oxygen) from this chamber. Because the density of oxygen gas (~<NUM>/ℓ) and the density of nitrous oxide gas (~<NUM>/ℓ) cause different leak rates, the sampling technique can be used to confirm that the first gas has a density that is different than the second gas, and thus identify a difference between the first gas and the second gas. Based on the identification of this difference, a comparison of oxygen gas versus nitrous oxide gas can be performed, such as to verify that oxygen gas is being received from an intake designated to receive the oxygen gas, and to verify that nitrous oxide gas is being received from an intake designated to receive the nitrous oxide gas.

In an example, this sampling technique may be integrated as a safety component or function, and embodied within a standalone gas analysis device, a flowmeter component, an oxygen failsafe component, a manifold component, or other form of sensing or control apparatus used with gas mixing, delivery, or supply. The identification of an abnormal or unexpected (unsafe) condition may be used to cause a system shutdown, a change in gas mixture, a disconnection, an output alert or indication, or other precautionary or evasive action. Likewise, the identification of a normal or expected (safe) condition may be required as a precondition for the operation of a flowmeter, or used before the mixing or output of one or both gases or for other gas control operations.

In an example, an apparatus for verifying input gases may include a configuration including: a chamber (or separate chambers) adapted to receive a gas, the chamber including an inlet to receive the gas and a vent to exhaust the gas; a pressure sensor arranged to measure pressure within the chamber(s); a gas control coupled to the inlet, which fills a first gas and a second gas into the chamber(s) at respective times (or at the same time with separate chambers); and microprocessor circuitry to operate logic to measure and respond to the measurement of leak times. For instance, this logic may include observing pressure in the chamber at a first time period to identify a first elapsed time to exhaust the first gas from the chamber and reach a defined end pressure; observing pressure in the chamber at a second time period to identify a second elapsed time to exhaust the second gas from the chamber and reach the defined end pressure; and identifying a difference between the first gas and the second gas, based on a time difference between the first elapsed time and the second elapsed time. Various controls, signals, or identifications may be caused based on a difference between the elapsed time to reach the defined end pressure from gas received at an intake designated to receive nitrous oxide gas, and the elapsed time to reach the defined end pressure from gas received at an intake designated to receive oxygen gas.

In an example, a gas flow control system, including components for verifying input gases, may include a configuration including: a first intake adapted to receive a first gas and a second intake adapted to receive a second gas, where one of the first and second intake is designated to receive oxygen gas, and the other of the first and second intake is designated to receive nitrous oxide gas; a chamber (or multiple chambers) including an inlet to receive gas and a vent to exhaust the gas; and a gas control operable to respectively fill the chamber with the first gas and fill the chamber with the second gas to a determined begin pressure; and a microprocessor configured to measure respective times to exhaust the first gas and the second gas from the chamber, via the vent, and reach a determined end pressure. In this configuration, the microprocessor operates the gas control to enable gas flow for the first gas and the second gas, for output with mechanical or digital a gas flow meter, if a time to exhaust a gas received from the intake designated to receive the nitrous oxide gas exceeds the time to exhaust a gas received from the intake designated to receive the oxygen gas.

In an example, a method of verifying input gases may be performed by an apparatus, component, system, or other entities described herein. The method of verifying the input gases may include: filling a chamber with a first gas to a defined begin pressure (e.g., <NUM> and <NUM> kPa gauge (<NUM> to <NUM> psi gauge)); monitoring pressure in the chamber during the first time period, using a pressure sensor, to measure a first time to exhaust the first gas from the chamber, via a vent (e.g., a fixed orifice, such as a pinhole), to reach a defined end pressure (e.g., <NUM> and <NUM> kPa gauge (<NUM> to <NUM> psi gauge)); filling the chamber with a second gas to the defined begin pressure; monitoring pressure in the chamber during the second time period, using the pressure sensor, to measure a second time to exhaust the second gas from the chamber, via the vent, to reach the defined end pressure; and identifying a difference between the first and second gas, based on a difference between the first time and the second time. For instance, this method may verify one of the first and second gases as oxygen, and the other of the first and second gases as nitrous oxide, if the time to reach the defined end pressure by exhaust of the nitrous oxide gas exceeds the time to reach the defined end pressure by exhaust of the oxygen gas.

The present disclosure describes devices and methods for identifying properties of and differentiating between gases used in anesthesia gas control equipment. In particular, the following describes a detection system and method used to distinguish between oxygen and nitrous oxide gases with use of a measured exhaust procedure. This procedure can involve, among other operations, the observation of gas pressure within a chamber, and the measurement of time for a first and a second gas to leak from the chamber. Gases with lower density-such as oxygen-will leak faster than heavier gases such as nitrous oxide. Based on the difference in time for the first and the second gas to be exhausted from the chamber (e.g., with a consistent exhaust vent and a chamber pressure measurement(s)), differences in density between the first gas and the second gas can be identified. In a similar procedure, based on a comparison of the time to exhaust a particular gas to an expected time, ratio of times, or other measurement to exhaust the particular gas, the properties of a single gas can be identified as within-or outside of-an expected operational range.

The disclosed detection system and method can enable a verification of the gas provided from inlets associated with the first gas and the second gas, or the verification of properties of one gas or multiple gases, for a variety of safety and operational purposes. For instance, a verification procedure may identify that gas flowing through an inlet designated for oxygen is correctly oxygen gas, and gas flowing through an inlet designated for nitrous oxide is correctly nitrous oxide gas, due to the heavier density of nitrous oxide which causes it to take more time to exhaust from the vent relative to oxygen. The verification procedure may also identify scenarios in which an incorrect gas (or an unknown gas or gas mixture) is provided in contravention of expected gas properties.

In the context of existing anesthesia gas control equipment such as digital flowmeters, one function of the gas control equipment is to provide accurate controls that deliver combined gas (a mixture of O<NUM> and N<NUM>O) as an output at a fixed flow rate, allowing an output mixture to provide a precise percentage of a gas composition. Such gas control equipment can monitor for gas flow rate, to ensure that a connected gas source can provide gas, and specifically in the case of oxygen to ensure that a source of oxygen gas appears available for at least emergency purposes. However, within such gas control equipment, there is currently no way to know if the oxygen and nitrous oxide gas input lines are accidentally reversed, if the oxygen and nitrous oxide gas input lines are connected to the same type of gas, or if oxygen gas is missing entirely. In any of these scenarios, the flow of gas may appear normal even as the wrong gas is selected to be delivered, leading to unforeseen consequences.

Although oxygen sensors which use chemical reagents can detect the presence of oxygen gas, the use of such sensors has not been widely implemented in anesthesia gas control settings to identify or prevent reversed gas lines and other dangerous operational faults. Existing failsafe and safety devices cannot ensure that a source of oxygen, needed for emergency settings, is actually available for patient use. These and other safety and technical limitations are addressed by the following systems and methods.

<FIG> illustrates an operational scenario <NUM> using gas flow control equipment for delivery of anesthesia gases. The operational scenario <NUM> specifically focuses on the delivery of anesthesia gases from a gas supply location to a gas delivery location, as mixed and controlled via a flow metering device <NUM>. Although this operational scenario <NUM> is suggestive of a gas supply and delivery scenario via built-in (e.g., centralized, permanently installed) components of a medical facility, it will be understood that the gas supply and delivery scenario may also apply to portable or movable components. For instance, the flow metering device <NUM> may be integrated with gas supply equipment on a cart, to enable movement among different patient rooms or locations. It will be understood that the arrangement and components in the operational scenario <NUM> is provided for purposes of illustration and not necessarily limitation. Also, as discussed herein, usage of the term "anesthesia" is intended to be interchangeable with the terms "analgesia" and "conscious sedation", to encompass multiple forms of medically-induced pain control using nitrous oxide.

Within the operational scenario <NUM>, anesthesia gases such as nitrous oxide gas and oxygen gas are sourced from a nitrous oxide supply <NUM> and an oxygen supply <NUM> at a gas supply location. For example, the gas supply location may supply one or multiple delivery locations in a medical facility with the anesthesia gases, from among one or multiple supply tanks. In an example, the nitrous oxide supply <NUM> and the oxygen supply <NUM> are connected to a gas manifold <NUM> which enables distribution of gases within the medical facility. The manifold <NUM> may include various gas flow control and monitoring capabilities to enable uninterrupted or monitored distribution of the respective gases to one or multiple delivery locations, such as with automatic gas cylinder changeover, verification of line pressure, and the like.

The output from the manifold <NUM> includes two gas lines, specifically a nitrous oxide gas line <NUM> and an oxygen gas line <NUM>, which deliver gas to the flow metering device <NUM>. The flow metering device <NUM> enables mixing of the anesthesia gases delivered from the gas lines <NUM>, <NUM>, according to gas mixtures being specified by input controls of the flow metering device <NUM>. In an example, the flow metering device <NUM> includes a user control <NUM> with various input controls (e.g., buttons, knobs, input screens, etc.) and output indicators (e.g., LED / LCD display components, digital indicators, output screens, etc.) relating to the mixture and delivery of the anesthesia gas. In other examples, the flow metering device <NUM> is operably connected to other electronic or computing devices (e.g., personal computers, workstations, mobile devices, etc.) for control, monitoring, or logging purposes. In other examples, the flow controls of the flow metering device <NUM> are strictly mechanical and the flow indicators are ball and tubes.

In an example, the flow metering device <NUM> can include an output indication <NUM> for an output status of the nitrous oxide gas and an output indication <NUM> for an output status of the oxygen gas, which are mixed into a gas mixture provided via a mixed gas line <NUM>. This mixed gas line <NUM> may provide delivery of the gas to a gas delivery location <NUM> (such as a dentist office chair or medical facility procedure location), including from a chairside terminal <NUM>. Further delivery of the gases from the mixed gas line <NUM> and the chairside terminal <NUM> to a patient are not shown in <FIG>. However, it will be understood that additional gas delivery hoses, vacuum hoses, a gas delivery masks, and other features or components may be involved for safe administration of the mixed anesthesia gases to a particular patient.

<FIG> illustrates a schematic diagram of an anesthesia gas verification arrangement <NUM>, based on a configuration of a gas verification apparatus <NUM>. In various examples, the gas verification apparatus <NUM> may be a standalone device or integrated into a gas control system such as a flowmeter apparatus or system. For purposes of illustration, the gas verification apparatus <NUM> is illustrated as separate from the control components of the flow metering device <NUM> but connected to a same gas supply line. In other configurations, the gas verification apparatus <NUM> can be integrated with the flow metering device <NUM>.

In an example, the gas verification apparatus <NUM> may be integrated within a flow mixing or metering system, including being located within a housing for a flowmeter. In a varying example, the gas verification apparatus <NUM> may be external to the housing of a flowmeter. For instance, the gas verification apparatus <NUM> may be integrated with an oxygen failsafe device (not shown), which operates to supply oxygen or restrict non-oxygen gases in the case of a low pressure or flow of oxygen. In a varying example, the gas verification apparatus <NUM> may be integrated into a gas switching, mixing, or control apparatus, such as the manifold <NUM>, or other centralized or installed equipment. In the following example, the gas verification apparatus <NUM> is referenced as being located within or operably coupled to a flow metering device <NUM>, such as being controlled by a safety control <NUM> within the flow metering device.

The gas verification apparatus <NUM> is illustrated as including a pressure chamber <NUM>, which includes an inlet <NUM> to receive gas, and a vent <NUM> to exhaust gas. The gas verification apparatus <NUM> further includes a pressure sensor <NUM> adapted to measure the pressure of gas within the chamber <NUM>. A sequence of chamber pressure and time measurements for each measured gas may be performed as discussed below. In an example, the gas verification apparatus <NUM> may include a microprocessor (not shown) used to control the chamber pressure and perform the time measurements; in other examples, the safety control <NUM> or other components of the flow metering device <NUM> may include a microprocessor to control the chamber pressure and perform the time measurements.

The gas supply arrangement depicted in <FIG> provides a further use of the oxygen and nitrous oxide gas supply depicted in operational scenario <NUM>; however, it will be understood that the gas supply arrangement depicted in <FIG> may be arranged for other operational scenarios. The gas supply arrangement in <FIG> specifically includes the supply of an oxygen gas <NUM> controlled by a reducing valve <NUM>, and the supply of a nitrous oxide gas <NUM> controlled by a reducing valve <NUM>. The supplies of these gases <NUM>, <NUM> is provided to the flow metering device <NUM> with additional gas connections, valves, actuators, and sensors not shown in detail in <FIG>. The operation of the reducing valves <NUM>, <NUM> are respectively controlled by a mixer control <NUM> of the flow metering device <NUM>, which operates as a gas mixer.

In an example, the supplies of the nitrous oxide gas <NUM> and the oxygen gas <NUM> are provided to the gas verification apparatus <NUM> through the use of a three-way valve <NUM>. In an example, the control of the three-way valve <NUM> is provided from a safety control <NUM> integrated within the flow metering device <NUM>. For instance, the safety control <NUM> may control the dispensing of the respective gases into the chamber <NUM>, based on monitoring of the pressure in the chamber <NUM> as indicated by the pressure sensor <NUM>. The safety control <NUM> may include a microprocessor or other processing circuitry used to measure the chamber pressure, and perform an evaluation of a time for the respective gases to exhaust from a begin pressure to an end pressure (e.g., the amount of time for the gas to exhaust from <NUM> kPa to <NUM> kPa (<NUM> psi to <NUM> psi (pounds-per-square-inch)) gauge (relative to atmospheric pressure)). With this measurement, the safety control <NUM> may verify that a gas, provided from a supply line designated (e.g., labeled, fitted) to provide oxygen, exhausts from the vent <NUM> of the chamber <NUM> more quickly than a gas provided from a supply line designated to provide nitrous oxide. The safety control <NUM> may perform other types of comparisons or measurements.

In various examples, a microprocessor or other processing circuitry (not shown) may be integrated within the gas verification apparatus <NUM> to perform pressure readings of the chamber from the pressure sensor <NUM> and associated time measurements or comparisons. For example, the safety control <NUM> may be operably coupled to such circuitry and receive an indication that a time comparison between the first gas and second gas exceeds a defined threshold, is within a defined range, matches a particular ratio or ratio range, etc..

The gas verification apparatus <NUM> can perform a sequence to fill the pressure chamber <NUM> with each gas to at least a defined or calculated begin pressure and exhaust the pressure chamber <NUM> with each gas to at least a defined or calculated end pressure. A microprocessor may operate a timer that starts and stops based on pressure sensor measurements of the begin and end pressure, respectively. The amount of time needed to fill a gas in the pressure chamber <NUM> to the defined begin pressure and exhaust the gas in the pressure chamber <NUM> to the defined end pressure may be on the manner of tenths of seconds or seconds; for instance, each fill and exhaust cycle may be designed to take from about <NUM> seconds to about <NUM> seconds, depending on the size of the pressure chamber <NUM> and the vent <NUM>. Thus, the operation of the gas verification apparatus <NUM> may be quickly performed during startup or verification of the flow metering device <NUM>.

The exhaust from the pressure chamber <NUM> may occur from the vent automatically or under control. In an example, the vent may be a size-restricted but uncontrolled orifice (e.g., an always-open pin-hole, of a fixed diameter) which allows venting from the gas verification apparatus <NUM> to an outside location such as the mixed gas line <NUM>, a vacuum scavenging system, an open area of a housing or enclosure, ambient atmosphere, etc. To enable the measurement, one side of the exhaust provides a known pressure or, has predictable pressure. Here, use of outside pressure (e.g., outside of the chamber), can be easily utilized, since this provides consistent atmospheric pressure. In a varying example, the vent <NUM> may be a restricted and controlled orifice, which is actuated between an open state (e.g., openable to a consistent diameter or known size) or a closed state. The actuation of the vent <NUM> may occur based on the pressure sensor <NUM>, the safety control <NUM>, or other circuitry or components of the gas verification apparatus <NUM>, flow metering device <NUM>, or other control systems discussed herein.

In an example, the verification operations can be performed by the gas verification apparatus <NUM> upon startup of the flow metering device <NUM>, prior to dispensing of gas to a patient. In other examples, verification operations by the gas verification apparatus <NUM> are performed as part of a testing or verification phase which may be automatically or manually initiated (e.g., by a user in a testing scenario, on a scheduled basis, etc.). The timing and number of the verification operations, involving pressure testing of the gases, may vary depending on implementations or type of uses, the type of gases, the usage of the flow metering device, or other factors.

In a further example, separate pressure chambers (e.g., two chambers) may be used for conducing the gas measurements and comparisons discussed herein. For instance, a separate chamber may be used for receiving and measuring the leak rate of each gas, provided that the chambers are include the same characteristics (e.g., if the volume of each chamber and the exhaust port of each chamber are identical or within some tolerance).

<FIG> provides a graphical illustration of pressure readings over time for anesthesia gases, performed with a controlled leak sequence in a gas verification apparatus. The y-axis <NUM> depicts gas pressure of the chamber in psi gauge, and the x-axis <NUM> depicts time in seconds. The graph depicted in <FIG> indicates example measurements of chamber gas pressure over time, for a first gas <NUM>, and a second gas <NUM>, based on controlled exhaust from a pressure chamber (e.g., exhaust from the chamber <NUM> via the vent <NUM>). In this illustrated example, the first gas <NUM> is pure nitrous oxide gas, and the second gas <NUM> is pure oxygen gas.

The time and pressure measurements indicated in <FIG> may reach thresholds (such as maximum and minimum values) to trigger the start and end of the pressure measurement. Gas that is typically supplied in anesthesia settings is provided from about <NUM> kPa (<NUM> psi) to about <NUM> kPa (<NUM> psi gauge). As a result, the verification process may be configured to start time measurements for the leak rate from a defined start ("begin") pressure at a value less than the gas line pressure, such as at about <NUM> kPa (<NUM> psi), or defined within the range of about <NUM> kPa (<NUM> psi) to about <NUM> kPa (<NUM> psi) gauge. Likewise, the end of the time measurements may coincide to reaching a defined concluding ("end") pressure that is at <NUM> kPa (<NUM> psi) or some greater value, such as defined with the range of about <NUM> kPa (<NUM> psi) to about <NUM> kPa (<NUM> psi) gauge. Other pressure values may be selected or calculated; further, the use of sensitive sensors may enable the use of smaller exhaust ranges in a shorter period of time.

A comparison of the amount of time needed to exhaust each gas from the begin pressure to the end pressure may indicate a variety of conditions. For example, an amount of time to exhaust a gas received from an input line expected to be oxygen, which is shorter than an amount of time to exhaust a gas received from an input line expected to be nitrous oxide, can indicate that no crossover is present. Conversely, a longer amount of time to exhaust a gas received from an input line expected to provide oxygen, than from an input line expected to provide nitrous oxide, may indicate that crossover is present. A same amount of time to exhaust gases from different input channels may indicate that the same type of gas is present in both input channels.

In other examples, a comparison of other pressure or time-based values or derivatives may be performed. For example, a microprocessor may compare the exhaust times between the begin and end pressures for two gases based on an expected (e.g., predetermined) ratio between the gases. In an example that uses an orifice to leak gas, the volumetric gas flow is proportional to the reciprocal of the square root of the gas mass density, and thus each of the gases will leak through the orifice at a different rate. Sizing the orifice sufficiently to keep complicating factors out of consideration, the ratio of leak rates between nitrous oxide and oxygen may be expected to be at or near a fixed value as shown by Equation (<NUM>) below: <MAT> Other types of comparisons, verifications, and actions may occur as part of gas line monitoring scenarios which involve time and pressure measurements from a controlled leak or exhaust.

<FIG> provides a flowchart <NUM> depicting a method of verifying and controlling gas delivery for anesthesia gases. The flowchart <NUM> provides a more detailed breakout of operations for measuring and verifying gas composition, such as with a sequential gas leak measurement performed with use of the chamber <NUM>, vent <NUM>, and pressure sensor <NUM>, discussed above. However, it will be understood that the operations of <NUM> may also be modified for concurrent or simultaneous use of the gas measurements using dual chambers, vents, and sensors.

The operations of the flowchart <NUM> may be implemented based on electronically or electromechanically controlled actions, performed by the flow metering device <NUM>, gas verification apparatus <NUM>, or other devices or components discussed herein. However, it will be understood that external control from users or other external systems or entities may cause or control the operations of the flowchart <NUM>.

The flowchart <NUM> includes a first cycle, involving the filling of a measurement chamber with a first gas to a determined chamber pressure (operation <NUM>), followed by a measuring of the release (exhaust) of the first gas via a vent (operation <NUM>, e.g., with vent <NUM>). The measuring of the release of the first gas is based on chamber pressure readings from a pressure sensor (e.g., pressure sensor <NUM>). One or more time measurements may be obtained based on the release, such as a total elapsed time to exhaust the first gas.

The flowchart <NUM> continues with a second cycle, similarly involving the filling of the measurement chamber with a second gas to the determined chamber pressure (operation <NUM>, e.g., with the same chamber pressure used during the first cycle), followed by the measuring of the release (exhaust) of the first gas via the vent (operation <NUM>, e.g., with vent <NUM>). Again, the measuring of the release of the first gas is based on chamber pressure readings from the pressure sensor (e.g., pressure sensor <NUM>), although a different or alternative pressure sensor or measurement technique may be used. One or more time measurements may be obtained based on the release, such as a total elapsed time to exhaust the second gas.

The flowchart <NUM> continues with an analysis cycle. This may include comparison of time measurements (operation <NUM>), to compare the amount of time needed to release the first gas versus to the second gas, such as based on a total elapsed time reach an exhausted (end) pressure from a filled (begin) pressure in the chamber. This comparison is analyzed to identify one or more conditions of the input gases or equipment configurations (operation <NUM>), based on the time measurement condition.

The flowchart <NUM>, in some examples, may also include operations to control the gas delivery based on the one or more identified conditions (operation <NUM>). For example, this may include the output of an alarm or status indicator, via an audible or visible indication. In further examples, the control operations may coordinate with other alarms or controls provided by failsafe devices (such as failsafe devices which activate when oxygen pressure falls below a defined psi or flow rate). In other examples, a failsafe device utilizing the gas flow principles previously described may be added onto a mechanical system in which case this failsafe device could have valves that would shut if the gases were mixed. In addition, this failsafe device could send out an alarm from its own speaker to alert the user that a problem was encountered. This would allow a failsafe device to control gases in a mechanical flowmeter.

<FIG> provides a flowchart <NUM> depicting a further method of identifying anesthesia gases and controlling operational conditions based on time measurements of exhausting the anesthesia gases. This flowchart <NUM> may provide further verification operations that are implemented as part of or in substitute for operations <NUM>-<NUM>, discussed above, or as standalone analysis operations (e.g., by a flowmeter safety control).

The flowchart <NUM> includes an operation to perform exhaust time measurements on one or more gases using a measurement chamber (operation <NUM>), such as with the gas verification apparatus <NUM> discussed above. The results of these exhaust time measurements may provide values similar to those depicted in <FIG> above.

The flowchart <NUM> continues with the identification of a measurement(s) received from a source designated to provide oxygen gas (operation <NUM>), and the identification of the measurement(s) received from a source designated to provide another gas (operation <NUM>) such as nitrous oxide. The identification of these measurements may be based on time and pressure sensor data, for example, to produce a time measurement such as a total elapsed time for the respective gases.

The flowchart <NUM> continues with a comparison of the time measurements (operation <NUM>), relative to a programmed time difference such as an expected leak rate for one or both gases, a ratio of leak rates between the gases, a threshold or range of time differences, or similar value comparisons. A determination is then performed to identify whether the exhaust time measurement between the gases meets the comparison range or threshold (decision <NUM>). In the event that only one gas is being analyzed, operations <NUM>-<NUM> may be omitted or modified to perform a comparison of time and pressure values against a set of predetermined values (e.g., values which are specific to oxygen).

In response to a determination that the exhaust time satisfies the comparison range or threshold to identify oxygen (e.g., meets or exceeds the ratio, or has a different elapsed time for exhaust than the other gas), oxygen gas can be identified from the source designated to provide oxygen (operation <NUM>). This can be accompanied by a signal of an operational proceed condition (operation <NUM>, e.g., a "pass" for a gas verification test).

In response to a determination that the exhaust time does not satisfy the comparison range or threshold to identify oxygen (e.g., meets or exceeds the ratio, or does not have a different elapsed time for exhaust than the other gas), a non-oxygen gas can be identified from the source designated to provide oxygen (operation <NUM>). This can be accompanied by a signal of an operational fault condition (operation <NUM>, e.g., a "fail" for the gas verification test).

<FIG> provides a block diagram of a gas control system <NUM>, including the gas verification apparatus <NUM> and a gas flow control <NUM> configured for implementing techniques and methods discussed above. In various examples, the gas control system <NUM> may comprise a flowmeter, manifold, control system, or other gas control component.

The gas verification apparatus <NUM> may include the chamber <NUM> for receiving and measuring gas leak rates, through gas received via the inlet <NUM>, exhausted with the vent <NUM>, and measured with the pressure sensor <NUM>, as discussed for <FIG> above. The gas verification apparatus <NUM> may include or be operably coupled to microprocessor circuitry <NUM> to allow the execution of instructions, programmed logic, or other forms of programming to accomplish digital processing and operations. The microprocessor circuitry <NUM> may include a processor <NUM>, such as provided by a microprocessor, central processing unit (CPU), system-on-chip, or other processing circuitry, and a memory <NUM>, such as provided by read only memory, random access memory, non-volatile storage memory, among other types of memory units. Various values, measurements, and information associated with the verification process or the gas control system generally may be maintained in the memory <NUM> and computed with the processor <NUM>.

The gas flow control <NUM> may operate with the functionality or capabilities provided by the flow metering device <NUM>, as discussed in the figures above; in the example of <FIG>, the gas flow control <NUM> includes the safety control <NUM> and mixer control <NUM>, in addition to one or more actuators <NUM> and one or more sensors <NUM>. For instance, the one or more actuators <NUM> may control valves and outputs for mixing gas, based on signals from the mixer control <NUM>. The one or more sensors <NUM> may observe and sense system states and gas flow conditions, and be used in operation of the safety control <NUM> and the mixer control <NUM>.

The gas control system <NUM> may include input controls <NUM> used to operate the mixer control <NUM> and other features of the gas flow control <NUM>, and output indicators <NUM> used to indicate a status of the mixer control <NUM> and other features of the gas flow control <NUM>. For example, the input controls <NUM> may receive values for an input gas mixture, from a user, to mix multiple gases, which cause the actuators <NUM> and sensors <NUM> of the gas flow control <NUM> to mix and deliver gas via the mixer control <NUM> according to particular rates, ratios, or amounts. Likewise, the output indicators <NUM> may provide a user with a status of operation, based on the state of the actuators <NUM> and sensors of the gas flow control <NUM>, according to the operation of the mixer control <NUM>. The input controls <NUM> and output indicators <NUM> may also be involved with the use of the safety control <NUM>, including with operation of safety operations provided by the gas verification apparatus <NUM>.

The gas control system <NUM> may include a communication interface <NUM>, used in connection with monitoring, verification, logging, or other operations. The gas control system <NUM> may also be operably or communicatively coupled to other gas delivery or distribution equipment, causing a shutdown or change in other equipment as a result of detected or identified conditions.

Although many of the previous examples are provided with reference to the measurement and verification of a first gas relative to a second gas, it will be understood that many of these procedures may be accomplished with evaluation or verification of a single gas, more than two gases, or adapted to other types of gas verification settings. For instance, a comparison of an elapsed exhaust time for gas received from an oxygen gas line may be compared to a recorded range of values, based on pre-calibrated or pre-determined oxygen gas values. Further, although many of the previous examples are provided with reference to use of oxygen and nitrous oxide gases, the present techniques and configurations can be used to differentiate between any two gases as long as they are sufficiently apart in density such that a sensor configuration can detect a meaningful difference in flow rates over a controlled pressure drop.

Additionally, although many of the previous examples are provided with reference to the integration of the gas verification apparatus within a flowmeter, the gas verification apparatus may be hosted as a standalone, add-on unit that is attachable/couplable to an exterior of a flowmeter, manifold, or other gas distribution equipment. It will also be understood the various safety alarms, sensors, actuators, may be controlled or provided by a standalone or separate device, such as with the use of a valve actuator which restricts or shuts off a port or a gas source in response to detecting an unexpected condition. The gas verification apparatus may also provide remote control and monitoring features, such as to receive or send a restriction or shutoff command to connected gas distribution equipment in response to detecting an unexpected condition. Other use cases and variations may also be provided with use of the present verification systems and methods in a gas verification apparatus and flowmeter equipment.

Some examples can include a computer-readable medium or machine-readable medium encoded with instructions operable to configure an electronic device (including processing circuitry within such electronic device) to perform methods as described in the above examples.

Claim 1:
An apparatus for verifying input gases used in anesthesia gas control equipment, the apparatus comprising:
a chamber (<NUM>) adapted to receive a gas, the chamber including:
an inlet (<NUM>) to receive the gas; and
a vent (<NUM>) to exhaust the gas;
a pressure sensor (<NUM>) arranged to measure pressure within the chamber;
a gas control (<NUM>) coupled to the inlet, the gas control configured to fill a first gas and a second gas into the chamber at respective times, wherein one of the first and second gas is oxygen gas and wherein the other of the first and second gas is nitrous oxide gas, and wherein the inlet is connected to an intake designated to receive the oxygen gas and an intake designated to receive the nitrous oxide gas, the gas control (<NUM>) operable to:
fill the chamber (<NUM>) with the first gas to a defined begin pressure; and
fill the chamber (<NUM>) with the second gas to the defined begin pressure; and
microprocessor circuitry, coupled to the pressure sensor, the microprocessor circuitry operable to:
observe pressure in the chamber (<NUM>) at a first time period, measured with the pressure sensor (<NUM>), to identify a first elapsed time to exhaust the first gas from the chamber, via the vent (<NUM>), and reach a defined end pressure;
observe pressure in the chamber (<NUM>) at a second time period, measured with the pressure sensor (<NUM>), to identify a second elapsed time to exhaust the second gas from the chamber, via the vent (<NUM>), and reach the defined end pressure; and
identify a difference between the first gas and the second gas, based on a time difference between the first elapsed time and the second elapsed time.