WO2016198478A1 - Détermination de l'écoulement d'un humidificateur - Google Patents

Détermination de l'écoulement d'un humidificateur Download PDF

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Publication number
WO2016198478A1
WO2016198478A1 PCT/EP2016/063075 EP2016063075W WO2016198478A1 WO 2016198478 A1 WO2016198478 A1 WO 2016198478A1 EP 2016063075 W EP2016063075 W EP 2016063075W WO 2016198478 A1 WO2016198478 A1 WO 2016198478A1
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WO
WIPO (PCT)
Prior art keywords
fluid conduit
temperature
flow
insufficient
humidification
Prior art date
Application number
PCT/EP2016/063075
Other languages
English (en)
Inventor
Phillip William DIXON
Original Assignee
Intersurgical Ag
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Filing date
Publication date
Application filed by Intersurgical Ag filed Critical Intersurgical Ag
Publication of WO2016198478A1 publication Critical patent/WO2016198478A1/fr

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
    • A61M16/10—Preparation of respiratory gases or vapours
    • A61M16/14—Preparation of respiratory gases or vapours by mixing different fluids, one of them being in a liquid phase
    • A61M16/16—Devices to humidify the respiration air
    • A61M16/161—Devices to humidify the respiration air with means for measuring the humidity
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
    • A61M16/0051—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes with alarm devices
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
    • A61M16/021—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes operated by electrical means
    • A61M16/022—Control means therefor
    • A61M16/024—Control means therefor including calculation means, e.g. using a processor
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
    • A61M16/10—Preparation of respiratory gases or vapours
    • A61M16/1075—Preparation of respiratory gases or vapours by influencing the temperature
    • A61M16/109—Preparation of respiratory gases or vapours by influencing the temperature the humidifying liquid or the beneficial agent
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
    • A61M16/10—Preparation of respiratory gases or vapours
    • A61M16/1075—Preparation of respiratory gases or vapours by influencing the temperature
    • A61M16/1095—Preparation of respiratory gases or vapours by influencing the temperature in the connecting tubes
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
    • A61M16/10—Preparation of respiratory gases or vapours
    • A61M16/14—Preparation of respiratory gases or vapours by mixing different fluids, one of them being in a liquid phase
    • A61M16/16—Devices to humidify the respiration air
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M2205/00—General characteristics of the apparatus
    • A61M2205/15—Detection of leaks
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M2205/00—General characteristics of the apparatus
    • A61M2205/18—General characteristics of the apparatus with alarm
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M2205/00—General characteristics of the apparatus
    • A61M2205/33—Controlling, regulating or measuring
    • A61M2205/3331—Pressure; Flow
    • A61M2205/3334—Measuring or controlling the flow rate
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M2205/00—General characteristics of the apparatus
    • A61M2205/33—Controlling, regulating or measuring
    • A61M2205/3368—Temperature
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M2205/00—General characteristics of the apparatus
    • A61M2205/50—General characteristics of the apparatus with microprocessors or computers
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M2205/00—General characteristics of the apparatus
    • A61M2205/58—Means for facilitating use, e.g. by people with impaired vision
    • A61M2205/581—Means for facilitating use, e.g. by people with impaired vision by audible feedback
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M2205/00—General characteristics of the apparatus
    • A61M2205/58—Means for facilitating use, e.g. by people with impaired vision
    • A61M2205/583—Means for facilitating use, e.g. by people with impaired vision by visual feedback

Definitions

  • the present invention relates to the field of active humidification, and more particularly to the determination of fluid flow in an active humidification system.
  • Continuous Positive Airway Pressure is one such example that provides a continuous airflow to the respiratory passage of a patient, typically through a patient interface such as a respiratory mask, such that the airway of the patient is kept open and a sufficient flow of oxygen is delivered so as to assist the patient in breathing at a normal rate.
  • Other conventional forms of ventilation may include invasive or non-invasive patient interfaces that may be used as part of a ventilation system for a patient undergoing critical care.
  • Such active control of the temperature of inspiratory gas may be effective in maintaining the desired humidity of the gas flow and reducing discomfort felt by a patient, yet the temperature of the inspiratory gas needs to be closely controlled. For example, if a disruption to the airflow occurs, such that there is a variation in the volume of gas flowing through the system, then there is a risk that the inspiratory gas may be heated to an uncomfortable or dangerous temperature.
  • a method of monitoring fluid flow in humidification apparatus for supplying humidified gas to a patient, the apparatus comprising a humidification chamber for humidifying gases to be inhaled by a patient, a patient interface for delivery of humidified gases to a patient's airway, a fluid conduit extending between the humidification chamber and the patient interface such that humidified gas may flow from the humidification chamber to the patient interface in use, the fluid conduit having a heat source to supply heat to gas flowing therethrough, wherein the method comprises: measuring the temperature of humidified gas at a first location between the humidification chamber and patient interface;
  • the method of the first aspect of the present invention may be advantageous, principally as insufficient fluid flow may be determined based on a direct comparison of relative temperatures of humidified gas flowing through the fluid conduit at two separate locations.
  • the method may eliminate the need for flow sensors to determine insufficient fluid flow conditions through the fluid conduit, and thus the method may be simpler, and less expensive, than methods known in the prior art.
  • the method of the first aspect of the present invention may not require measurement of the actual level of power supplied to the heated humidification chamber and/or accurate determination of the heat supplied to the humidified gas by the fluid conduit, and may thus be simply performed without the need to monitor or receive readings for additional operational parameters of the humidification apparatus.
  • insufficient fluid flow refers to a situation where the fluid flow to the patient and/or through the fluid conduit is unacceptably low for normal operation of the respiratory system, eg a zero or nearly zero flow rate. There may be a normal operating range which can accommodate high and/or low fluid flow compared to a normal rate of fluid flow through the fluid conduit, and the apparatus may be able to function normally when fluid flow is within this normal operating range. However, insufficient fluid flow is flow which is lower than that
  • the normal operating range and hence also the insufficient fluid flow rate, may vary depending on, for example, the
  • Insufficient flow may be determined when the temperature difference is equal to or below a threshold value, which may be zero value, a negative value or a positive value less than the temperature difference during normal operation, e.g. less than 70%, 60%, 50%, 40%, 30%, 20%, or 10% of the normal positive temperature difference. Insufficient flow may be determined when the temperature difference is equal to or below a threshold value significantly less than the temperature difference during normal operation, e.g. 40% or less of the normal positive temperature difference. Such a difference may beneficially reduce the likelihood of false positive readings that need to be accommodated by the system.
  • Insufficient fluid flow through the fluid conduit may be determined when there is no, or no change in, temperature gradient between the relative temperatures sensed at the first and second locations, eg over a pre-determined period of time. Insufficient fluid flow through the fluid conduit may be determined when there is a negative temperature gradient between the relative temperatures sensed at the first and second location. The absence of a temperature gradient, or the presence of a negative temperature gradient, between the relative temperatures sensed at the first and second locations may be readily determined, and thus the method of the first aspect of the present invention may provide for simple and quick determination of insufficient fluid flow through the fluid conduit.
  • one or more of the indicators of insufficient flow defined herein may comprise a primary insufficient flow condition.
  • One or more secondary condition may be defined within the monitoring logic/algorithms, which, when present, overrides the primary insufficient flow condition. This is particularly useful for defining scenarios, such as during start-up of the apparatus or during warming up of the flow after a period of insufficient flow or inactivity, in which the flow regime may be acceptable, despite being outside of a normal operation range.
  • a negative temperature gradient between the first and second location may be permissible if it is rising at a predetermined rate, e.g. towards a target temperature.
  • a negative temperature gradient between the first and second location may be permissible if the
  • temperature at the first location is higher than desirable, i.e. to purposely allow the flow to cool between the first and second locations.
  • Insufficient flow may be determined if the temperature at the second location tends/drops towards a static/ambient temperature, e.g. at a predetermined rate or else if it comes within a predetermined threshold of the static/ambient temperature Additionally or alternatively, insufficient flow may be determined when the temperature at the second location departs from an acceptable temperature or temperature range at, or greater than, a predetermined rate.
  • the method may comprise outputting a signal indicative of insufficient fluid flow.
  • the signal may take the form of at least one audible and/or visual indicia that is provided to a user.
  • a user may be able to alter the set-up of the apparatus to combat the insufficient fluid flow through the fluid conduit, and/or any negative effects associated with such insufficient fluid flow.
  • the signal may take the form of an electronic signal, which may be used as a control signal, e.g. in controlling the humidification apparatus and/or conduit heat source.
  • the humidification apparatus/heat source may be automatically adjusted, e.g. by a controller, dependent on the electronic signal indicative of insufficient fluid flow through the fluid conduit.
  • the humidification apparatus and/or heat source may be self-regulating, and may require little or no input from a user during operation in response to an insufficient flow of respiratory gases.
  • the method may comprise reducing heat supplied to the heated humidification chamber when insufficient fluid flow is determined. No heat, or a reduced, lower level of heat, may be supplied to the heated humidification chamber when insufficient fluid flow is detected, e.g. by adjusting the power supplied thereto. Heat supplied to the heated humidification chamber may be manually reduced in response to the determination of insufficient fluid flow upon user interaction with the heated humidification chamber. Alternatively, heat supplied to the heated humidification chamber may be automatically reduced in response to the determination of insufficient fluid flow.
  • the method may comprise reducing heat supplied by the fluid conduit heat source to gas flowing therethrough when insufficient fluid flow is determined. No heat, or a reduced lower level of heat, may be supplied by the heat source to the fluid conduit or gas flowing therethrough when insufficient fluid flow is detected, e.g. by adjusting the power supplied thereto. Heat supplied by the heat source to gas flowing through the fluid conduit may be manually reduced in response to the determination of insufficient fluid flow upon user interaction with the fluid conduit. Alternatively, heat supplied by the fluid conduit to gas flowing therethrough may be automatically reduced in response to the determination of insufficient flow.
  • the first location may be proximate or within the humidification chamber, e.g. at or adjacent an outlet of the humidification chamber.
  • the temperature measured at the first location may be indicative of the temperature of humidified gas outputted by the heated humidification chamber.
  • the temperature measured at the first location may typically be in the region of 35-39°C, e.g. for normal use, although the system may be capable of measuring temperatures in the range 25- 45°C.
  • the second location may be proximate an inlet of the patient interface.
  • the temperature measured at the second location may be indicative of the temperature of humidified gas that is to be inhaled by a patient.
  • the temperature measured at the second location may typically be in the region of 38-42°C, e.g. during normal use.
  • the first and/or second location may be between the humidification chamber and patient interface provided the locations are spaced by a sufficient flow length to allow sensing of a change in temperature of the flow along the conduit in use between said locations.
  • the heat source may be adapted/located to heat the conduit and/or flow between the first and second locations. Where the first location is proximate an outlet of the heated humidification chamber and the second location is proximate an inlet of the patient interface, the heat source may be adapted to supply heat to gas flowing through the fluid conduit along substantially the entirety of the length of the fluid conduit.
  • the determination of insufficient fluid flow through the fluid conduit may be based on one or more constraint on the temperature of humidified gas measured at the second location. For example, insufficient fluid flow may be determined where the temperature measured at the second location drops, or fails to rise, at a predetermined threshold rate, e.g. by a pre-determined amount over a pre-determined period of time. The pre-determined temperature drop and/or the pre-determined period of time may be determined based on the humidification apparatus and/or heat source that is being used.
  • the determination of insufficient fluid flow through the fluid conduit may be based on one or more constraint on a pre-determined target temperature of humidified gas that is to be inhaled by a patient. For example, insufficient fluid flow may not be determined where the temperature of humidified gas to be inhaled by a patient is within a specified range of the pre-determined target temperature, e.g.
  • the specified range may be determined by the humidification apparatus being used and/or the patient to which humidified gas is to be supplied.
  • the pre-determined target temperature may vary from patient to patient, and may typically be, for example, in the region of 40°C.
  • the method may monitor or sense the power supplied to the humidification apparatus and/or heat source.
  • the determination of insufficient flow may be dependent on the power supplied to the heat source and/or the humidification apparatus.
  • the determination of insufficient fluid flow through the fluid conduit may be based on constraints on the heat supplied to the gas flowing through the fluid conduit. For example, where a large amount of heat has been supplied to the gas flowing through the fluid conduit for an extended period of time, and the temperature of the humidified gas that is to be inhaled by a patient is below a pre-determined target temperature, then insufficient flow may be indicated.
  • the determination of insufficient fluid flow through the fluid conduit may be based on one or more constraint on heat supplied by the humidification chamber heating means (e.g. a water heater). For example, where the temperature of humidified gas in the humidification chamber is greater than the temperature of the humidified gas to be inhaled by a patient by a pre-determined amount, then insufficient flow may be indicated.
  • the determination of insufficient fluid flow through the fluid conduit may be based on the relative temperatures measured at the first and second locations over a pre-determined period of time. For example, insufficient flow may be indicated only where the temperature at the second location is equal to, or less than, the temperature at the first location, for example over a pre-determined period of time. This may prevent false determination of insufficient fluid flow based on minor fluctuations in temperature.
  • the pre-determined period of time may be determined according to the humidification apparatus and/or the heat source being used, e.g. including operation thereof and/or power supplied thereto.
  • the determination of insufficient fluid flow may be based on a multiple clause decision making process, e.g. according to a hierarchical or sequential decision making process.
  • the multiple clause decision making process may use a single input parameter.
  • the multiple clause decision making process may use a plurality of input parameters.
  • Each clause may assess a different combination of operational parameters and/or may apply a different threshold to one or more operational parameter. This may inhibit false determination of insufficient fluid flow.
  • insufficient fluid flow may be determined by use of one, or a combination of input parameters, and normal flow may be reset by use of a different, or different combination of input parameters.
  • the multiple clause decision making process may provide multiple parameter hysteresis, and may thereby prevent oscillation in flow detection.
  • the multiple clause decision making process may be an iterative process, and, for example, may be repeated until a clear outcome is obtained. The frequency of iteration may depend on the output of each loop of the decision making process.
  • the plurality of input parameters may be any, or any combination, of: the temperature sensed at the first location; the temperature sensed at the second location; the difference between the temperatures sensed at the first location and the second location; variation in the temperature sensed at the first and/or second location over a pre-determined period of time; the temperature of respiratory gas in the humidification chamber; the temperature of respiratory gas at the patient interface, or a rise or fall thereof over a pre-determined period of time; a pre- determined target temperature of respiratory gas at the patient interface; the difference between the temperature of respiratory gas at the patient interface and a pre-determined target temperature of respiratory gas at the patient interface, e.g. over a pre-determined period of time.
  • the multiple clause decision making process may comprise a first, or first set of, clause(s), which, when met, are indicative of insufficient fluid flow through the fluid conduit.
  • the multiple clause decision making process may comprise a second, or second set of, clause(s), which, when met, are indicative of sufficient fluid flow through the fluid conduit. Where neither the first, or first set of, clause(s), nor the second, or second set of, clause(s) are met, the multiple clause decision making process may be restarted, eg for another iteration.
  • the multiple clause decision making process may comprise a plurality of clause(s), which, when met, are indicative of insufficient fluid flow through the fluid conduit, wherein a first clause assesses a drop in patient temperature and at least one further clause assesses whether an increase in patient temperature is below a predetermined positive threshold.
  • the apparatus for supplying humidified respiratory gas to a patient, the apparatus comprising a humidification chamber having a first heat source for humidifying gas to be inhaled by a patient, a patient interface for allowing inhalation of humidified gas by the patient, a fluid conduit extending between the heated humidification chamber and the patient interface such that humidified gas may flow from the heated humidification chamber to the patient interface in use, the fluid conduit comprising a second heat source to supply heat to gas flowing therethrough at least in a region extending between first and second locations, the second location being downstream of the first location, a first temperature sensor for measuring temperature in the fluid conduit at the first location, and a second temperature sensor for measuring temperature in the fluid conduit at the second location, wherein the apparatus is configured to output a signal indicative of insufficient fluid flow through the fluid conduit dependent on relative temperatures sensed by the first and second temperature sensors.
  • the relative ease of determination of insufficient fluid flow may allow the apparatus to be adjusted such that the likelihood of an overshoot in patient temperature is reduced when normal flow is re-established.
  • the apparatus may be configured to output a signal indicative of insufficient fluid flow through the fluid conduit when there is substantially no temperature gradient between the first and second temperature sensors or a negative temperature gradient between the first and second temperature sensors.
  • the signal indicative of insufficient fluid flow through the fluid conduit may take the form of at least one visual and/or audible indicia that is visible to a user, eg such that a user can manually adjust one or more operational setting in response thereto.
  • the signal may comprise an electronic signal, which may be used for control of the humidification apparatus, eg the first heat source and/or second heat source.
  • the signal may be communicated to a controller of the humidification apparatus and/or heat source.
  • the humidification apparatus may be configured to automatically adjust dependent on the electronic signal indicative of insufficient fluid flow through the fluid conduit.
  • the humidification apparatus may be self-regulating, and may require little or no input from a user during operation.
  • Heat supplied to the first and/or second heat source may be automatically reduced in response to the signal indicative of insufficient fluid flow, and thus the apparatus may be viewed as self-regulating.
  • the fluid conduit may comprise respiratory tubing or the like.
  • the fluid conduit may comprise a heated wire conduit, and may, for example, have a heated wire embedded in a wall of the fluid conduit, wound around the exterior wall of the fluid conduit, or located within the flow path of the conduit.
  • the patient interface may comprise a respiratory mask, eg a face or nasal mask, one or more nasal prong, or else an invasive interface.
  • a respiratory mask eg a face or nasal mask, one or more nasal prong, or else an invasive interface.
  • the humidification chamber may comprise a water reservoir.
  • the humidification chamber may have a gas inlet, a gas outlet, and means for heating gases within the heated humidification chamber, such as, for example, a conductive base arranged for thermal contact with a heater.
  • the first and/or second temperature sensors may be located in the interior of the fluid conduit or patient interface and/or mounted in or to a wall thereof.
  • the first and/or second temperature sensor may or may not be located at a connector formation of the fluid conduit or patient interface, e.g. at a connector end thereof.
  • the fluid conduit could comprise a plurality of conduit portions, e.g. for attachment in a co-axial arrangement.
  • the first and/or second sensor could be mounted to a connector formation that is releasably attachable to the conduit, e.g. part way along the conduit or at a connector between the conduit and humidification chamber or between the conduit and patient interface.
  • the connector formation may comprise a collar or cuff formation and may comprise a male connector formation.
  • the first and/or second temperature sensors may be located on the exterior of the fluid conduit. This may provide the benefit of allowing the first and/or second temperature sensors to be easily removed and/or replaced if necessary.
  • first and/or second temperature sensors on the exterior of the fluid conduit may allow for the method of the first aspect of the present invention to be performed on existing humidification apparatus.
  • the method and apparatus of the first and second aspects of the present invention are primarily intended to be used for mechanical ventilation of a patient, i.e. in conjunction with a ventilator for regulating respiratory flow to/from the patient, it is envisaged that the method and apparatus may be more widely utilised in any respiratory system which comprises a fluid conduit adapted to supply heat to respiratory gas flowing to a patient, e.g. including CPAP systems.
  • a data carrier comprising machine readable instructions for the operation of one or more processors of a controller for humidification apparatus to:
  • Figure 1 is a flow diagram of a method of detecting insufficient fluid flow in humidification apparatus for supplying humidified gas to a patient according to first aspect of the present invention
  • FIG 2 is a simplified block diagram of humidification apparatus according to a second aspect of the present invention, which may be used in conjunction with the method of Figure 1 ;
  • FIG 3 is a flow diagram of a multi-clause decision making process for use with the method of the first aspect of the present invention.
  • a method of detecting insufficient fluid flow in humidification apparatus for supplying humidified gas to a patient, according to a first aspect of the present invention, is described with reference to Figures 1 and 2.
  • Humidification apparatus generally designated 10, is provided, and comprises a humidification chamber 12 for humidifying gases to be inhaled by a patient, a patient interface 14 for allowing humidified gases to be inhaled by a patient, and a fluid conduit 16 extending between the heated humidification chamber 12 and the patient interface 14, such that gas may flow from the humidification chamber 12 to the patient interface 14 in use.
  • the humidification chamber 12 has an inlet 18 for receiving gas to be humidified, and an outlet 20 for attachment to a first end the fluid conduit 16.
  • the inlet 18 is supplied by a flow source 17, typically comprising a regulated pressurised gas source for driving a flow of gas to the patient.
  • the humidification apparatus thus provides a respiratory system, which may be referred to as a respiratory circuit or patient circuit for delivering respiratory gases to a patient in a controlled manner.
  • the system may be used for patient therapy.
  • the control mechanisms that may be put in place to regulate the flow to the patient the apparatus may form part of patient ventilation system, i.e. for mechanical ventilation and/or critical care.
  • the flow of gases to the patient is thus typically controlled by the operation of the flow source 17.
  • An open or closed flow circuit between the flow source and patient may be used depending on the the specific care requirements.
  • the humidification chamber 12 comprises a heater 19 for heating respiratory gases flowing through the chamber 12. This may be achieved by way of a heated base plate on which the humidification chamber 12 stands, or is otherwise placed in thermal contact, in use.
  • the patient interface 14 is any conventional patient interface, such as, for example, a respiratory mask or invasive interface, which has an inlet for attachment to a second, opposing end of the fluid conduit 16.
  • the fluid conduit 16 comprises a heat source 21 to supply heat to gases passing therethrough, and may be, for example, a fluid conduit having a heated wire embedded on its outer surface, or within its walls, for example being wound around the conduit. In some embodiments the heat source 21 supplies heat to the fluid conduit 16 wall and thereby to gases passing therethrough along substantially the entirety of the length of the fluid conduit 16.
  • the method of the first aspect of the present invention involves the steps of measuring the temperature, Ti of humidified gases at a first location along the fluid conduit 100, measuring the temperature T2 of humidified gases at a second location of the fluid conduit that is downstream from the first location 102, and comparing at 104 the measured temperatures Ti and T2 to determine at 106 whether there is insufficient fluid flow through the fluid conduit 16. In presently preferred embodiments of the method, insufficient flow is determined when T2 is less than, or equal to, Ti.
  • the measurement of temperatures at the first and second locations is achieved in the humidification apparatus 10 of Figure 2 by the provision of first 22 and second 24 temperature sensors.
  • the first temperature sensor 22 is located in a region of the fluid conduit 16 that is proximate the interface between the fluid conduit 16 and the outlet 20 of the heated humidification chamber 12.
  • the second temperature sensor 24 is located downstream of the first temperature sensor 22, in a region of the fluid conduit 16 that is proximate the interface between the fluid conduit 16 and the patient interface 14.
  • the first 22 and second 24 temperature sensors may be temperature sensors located either internally or externally of the fluid conduit.
  • the sensors could be mounted to detect the temperature of the flow itself or the temperature of a member heated/cooled by the flow of respiratory gas, i.e. a gas washed surface, such as the conduit wall.
  • the humidification apparatus 10 in this example comprises a controller 25, which may be used to control the heat output by the heater 19 of the humidification chamber 12 and/or the heat output by the heat source 21 of the fluid conduit 16. This may be achieved by controlling the electrical supply to the, or each, heater.
  • a suitable controller could be mounted in the heater base of the humidifier, mounted in any other system component, or else provided in another control unit. Whilst a single controller is shown for simplicity, it is possible that separate controllers could be provided for the different heaters, which may be in communication with each other and/or the relevant sensors.
  • the controller 25 may be used to decrease the heat supplied by the heater 19 and/or the heat supplied by the heat source 21 when insufficient fluid flow through the conduit 16 is detected.
  • the controller may operate according to a normal mode of operation in which electrical energy is supplied to the heat source 19 and/or 21 within normal temperature limits and an insufficient flow mode of operation in which energy supplied to the heat source 19 and/or 21 is reduced or inhibited.
  • a flow diagram of a multi-clause decision making process which may be used in addition to the method of the first aspect of the present invention is shown in Figure 3.
  • the multi-clause decision making process begins at step 200. The decision making process may iterate as a loop during use of the humidification apparatus.
  • the first step 202 in the multi-clause decision making process measures the patient temperature Tp (ie the temperature of the humidified gas that is to be inhaled by a patient) over time, and compares Tp to the patient target temperature TT (ie the target temperature of the humidified gas that is to be inhaled by a patient), when there is no overdrive from the heated humidification chamber 12.
  • Tp drops by a predetermined amount, such as 2°C in this example, or more over a predetermined period of time, such as two, three, four minutes or more (e.g. a specific time period of 256 seconds is used in this example)
  • insufficient flow may be determined by the controller.
  • the multi-clause decision making process moves to the second step 204.
  • the multi clause decision process first assesses a most clear or severe indicator of insufficient flow, i.e. that Tp is dropping at least at a predetermined rate and/or that Tp is less that ⁇ by at least a predetermined temperature difference.
  • the second step 204 in the multi-clause decision making process measures Tp over time, and compares Tp to ⁇ , with further conditions placed upon the heat supplied to humidified gases by the fluid conduit 16 and the temperature of the heated humidification chamber 12, Tc.
  • Tp the heated wire of the fluid conduit 16 is on full power, and has been for an extended period of time, and Tp has risen by less than 0.5°C whilst Tp is more than 5°C below ⁇ , whilst Tc is more than 0.5°C higher than Tp (corrected for the target difference), then insufficient flow is determined 212. If these conditions are not met, then the multi-clause decision making process moves to the third step 206.
  • this clause 204 determines whether the difference between Tp and ⁇ is beyond a smaller threshold than in clause 202, but additionally uses a small positive threshold for the rate of temperature increase at Tp and/or a comparison between the humidification chamber temperature and the patient temperature to qualify an insufficient flow condition.
  • the third step 206 in the multi-clause decision making process measures Tp over time, and compares Tp to ⁇ , with further conditions placed upon the heat supplied to humidified gases by the fluid conduit 16 and the temperature of the heated humidification chamber 12 Tc.
  • Tp the heated wire of the fluid conduit 16 is on full power, and has been for an extended period of time, and Tp has risen by less than 0.5°C whilst Tp is more than 1 °C below ⁇ , whilst Tc is more than the value of (Tp + 1 °C), then insufficient flow is determined 212. If these conditions are not met, then the multi-clause decision making process moves to the next step 208.
  • the following steps 208 and 210 unlike the preceding steps are used to check for a positive indicator of normal flow rates. Thus, rather than simply assuming normal flow because the 'no flow' conditions of the previous steps are not satisfied, the controller applies criteria to confirm the existence of a normal, or
  • the fourth step 208 in the multi-clause decision making process simply measures Tp over time. In particular, if Tp rises by more than a predetermined amount (e.g. 2°C) over a preceding time period (e.g. the previous two, three, four or more minutes, such as 256 seconds in this example), then normal flow is determined 214. If this condition is not met, then the multi-clause decision making process moves to the fifth step 210.
  • the fifth/final step 210 in the multi-clause decision making process simply compares Tp to Tc corrected for the target difference. In particular, if Tp is higher than Tc corrected for the target difference, then normal flow is determined 214.
  • Tp must be higher than Tc by a predetermined static or dynamic threshold difference in order to establish a normal flow scenario. If this condition is not met, then the multi-clause decision making process returns to the beginning 200.
  • a static target temperature difference may be used for example in a normal, e.g. generally steady state, mode of operation.
  • a dynamic temperature difference may be used during start-up or else after a period of time in which flow had ceased.
  • the positive validation of normal flow may be logged by the controller and may allow a fresh iteration cycle to start, e.g. with a greater delay than in the event of neither determination of insufficient or normal flow in the previous cycle. If no positive verification of normal flow is made, then the process may iterate more quickly so as to reassess a potentially dubious flow regime.
  • the controller may automatically reduce or inhibit the heat output from either or both heater 19, 21 in order to prevent the buildup of excessive heat in the stagnant gas within the system.
  • the controller continues to monitor the sensor readings so as to identify when a positive determination of normal flow conditions is established at which point the controller resumes normal operation of the heater 19 and/or 21 . That is to say, upon a positive determination of flow at step 208 or 210, the controller increases the heat output of the heater 19 and/or 21 .
  • the clause 208 can establish the presence of a recovering flow and can thus resume normal heating with reduced duration of non- optimal heating of the respiratory gas flow to the patient.
  • a multi-clause decision making process in which at least one clause (and typically a plurality of clauses) is used to determine insufficient flow, at least one clause determines a recovering/increasing flow scenario and at least one clause determines a normal flow scenario.
  • This determination process is particularly useful since it allows a single iterative loop to cover all eventualities in a simple and effective manner without requiring the controller to switch between different loops for different scenarios, which could increase complexity and thereby increase the likelihood of potential control anomalies/failures.
  • the invention has been found to provide a simple and robust system for determining and reacting to a scenario in which there is insufficient flow, or no flow, of respiratory gas to a patient from a flow source.
  • the controller may control output of an alarm or other alert indicative of insufficient and/or normal flow conditions in addition to, or instead of, automated control of the heater(s).

Landscapes

  • Health & Medical Sciences (AREA)
  • Emergency Medicine (AREA)
  • Pulmonology (AREA)
  • Engineering & Computer Science (AREA)
  • Anesthesiology (AREA)
  • Biomedical Technology (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Hematology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Air Humidification (AREA)

Abstract

L'invention concerne un procédé permettant de surveiller un écoulement de fluide dans un appareil d'humidification (10) destiné à alimenter en gaz humidifié un patient, comprenant la mesure de la température du gaz humidifié en un premier emplacement entre une chambre d'humidification (12) et une interface patient (14), la mesure de la température du gaz humidifié en un second emplacement entre la chambre d'humidification (12) et l'interface patient (14), et la comparaison des températures relatives mesurées aux premier et second emplacements de façon à déterminer si l'écoulement de fluide est insuffisant à travers un conduit de fluide (16) s'étendant entre la chambre d'humidification (12) et l'interface patient (14). Le second emplacement est en aval du premier emplacement dans un sens d'écoulement menant à l'interface patient (14) le long du conduit de fluide (16).
PCT/EP2016/063075 2015-06-09 2016-06-08 Détermination de l'écoulement d'un humidificateur WO2016198478A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB1510028.2 2015-06-09
GB1510028.2A GB2539222B (en) 2015-06-09 2015-06-09 Humidifier flow determination

Publications (1)

Publication Number Publication Date
WO2016198478A1 true WO2016198478A1 (fr) 2016-12-15

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0885623A2 (fr) * 1997-06-17 1998-12-23 FISHER & PAYKEL LIMITED Système d'humidification pour un respirateur
WO2001013981A1 (fr) * 1999-08-23 2001-03-01 Fisher & Paykel Healthcare Limited Controleur d'humidite
US20090110379A1 (en) * 2007-10-29 2009-04-30 Smiths Medical Asd, Inc. Pid coefficient adjustment for respiratory heater closed loop control
WO2009145646A1 (fr) * 2008-05-27 2009-12-03 Fisher & Paykel Healthcare Limited Régulation de la température de chambre d’un humidificateur pour une régulation précise de l’humidité
WO2012065999A2 (fr) * 2010-11-15 2012-05-24 GRÜNDLER GmbH Procédés et dispositifs dans le domaine de traitement au moyen de gaz médicaux
WO2015038014A1 (fr) * 2013-09-13 2015-03-19 Fisher And Paykel Healthcare Limited Système d'humidification

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5529060A (en) * 1991-05-22 1996-06-25 Fisher & Paykel Limited Humidifiers with control systems to prevent condensation
AU2015203636B2 (en) * 2008-05-27 2017-08-31 Fisher & Paykel Healthcare Limited Control of humidifier chamber temperature for accurate humidity control

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0885623A2 (fr) * 1997-06-17 1998-12-23 FISHER & PAYKEL LIMITED Système d'humidification pour un respirateur
WO2001013981A1 (fr) * 1999-08-23 2001-03-01 Fisher & Paykel Healthcare Limited Controleur d'humidite
US20090110379A1 (en) * 2007-10-29 2009-04-30 Smiths Medical Asd, Inc. Pid coefficient adjustment for respiratory heater closed loop control
WO2009145646A1 (fr) * 2008-05-27 2009-12-03 Fisher & Paykel Healthcare Limited Régulation de la température de chambre d’un humidificateur pour une régulation précise de l’humidité
WO2012065999A2 (fr) * 2010-11-15 2012-05-24 GRÜNDLER GmbH Procédés et dispositifs dans le domaine de traitement au moyen de gaz médicaux
WO2015038014A1 (fr) * 2013-09-13 2015-03-19 Fisher And Paykel Healthcare Limited Système d'humidification

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GB201510028D0 (en) 2015-07-22
GB2539222A (en) 2016-12-14

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