Systems and methods for detecting incorrect flow conditions in a respiratory humidification system

Abstract

A detector of a low or no flow condition of a respiratory humidification system has an inspiratory conduit with an inspiratory conduit heating element. An inspiratory temperature sensor is located downstream of at least a portion of the inspiratory conduit heating element. A controller is configured to be in electrical connection with the inspiratory temperature sensor and the inspiratory conduit heating element, and to detect a low or no flow condition. The detection operates by the application of a low or no flow characteristic energisation signal to the inspiratory conduit heating element. Subsequently, a signal from the inspiratory temperature sensor is captured and processed to obtain a processed signal output. Where the processed signal output satisfies a criterion the low or no flow condition is detected.

Description

SYSTEMS AND METHODS FOR DETECTING INCORRECT FLOW CONDITIONS IN A RESPIRATORY HUMIDIFICATION SYSTEMFIELD OF TECHNOLOGY

[0001] The present invention relates to systems and methods for the detection of incorrect flow conditions within a respiratory humidification system, and more particularly but not solely to detectors and methods for detecting one or both of low or no flow conditions and reverse flow conditions in a respiratory humidification system.BACKGROUND

[0002] Various methods may be used to supply heated and / or humidified gases to a user or a patient. Respiratory assistance humidification systems generally include a source of pressurized gases (for example, air, oxygen, or other mixtures of gases) such as a ventilator, a humidifier including a source of water and a heat source to heat and / or humidify the gases from the gases source, and an inspiratory conduit to convey the heated and / or humidified gases to a patient interface, such as a mask, a nasal cannula, and the like. Humidification systems can be single-limb or dual-limb. In a single-limb system, exhaled gases from the patient can be released into the ambient air via vent holes on the patient interface or some other venting device. In a dual-limb system, exhaled gases can be conveyed from the patient back to the gases source via an expiratory conduit.SUMMARY

[0003] For proper functioning of a respiratory humidification system (also herein "humidification system") the gases should flow from the gases source through the humidifier to the patient. Under various conditions of the operation of a respiratory humidification system, this desired flow of gases may not occur, and instead an incorrect gases flow may be present. It may be desirable to detect one or more types of incorrect gases flows within a respiratory humidification system.

[0004] In some circumstances, the desired flow of gases may be prevented by a partial or full obstruction of one or more portions of the gases pathway, such as a conduit of a breathing circuit of the respiratory humidification system. Such an obstruction may result in a lower than desired flow rate being delivered, or even no flow being delivered. These conditions may be referred to collectively as a low or no flow condition.

[0005] A low or no flow condition may occur where in use an inspiratory conduit for conveying heated and / or humidified gases to a patient is being obstructed. For example, the conduit may be flattened such that gases flow is restricted or prevented. Particularly where the respiratory humidification system is used by a patient in bed, movement of the patient or the weight of bedding such as pillows may crush a conduit of the breathing circuit and restrict or preventgases flow through it, causing a low or no flow condition to occur. A low or no flow condition may occur when there is a leak in the system, which may be when a connection between respiratory humidification system components has become loose or disconnected, for instance if the dryline conduit has become loose or disconnected from either the gases source or the humidifier chamber. A low or no flow condition may occur when the gases source has been turned off or set to a very low flow. Humidification systems of the present disclosure can automatically detect a low or no flow condition and optionally alert a user. The low or no flow condition is a flow condition which is below a desired predetermined flow condition associated with the provision of the desired therapy. For instance, the low or no flow condition may have a lower flow than the operating range of one or more components of the respiratory humidification system, such as the breathing circuit. The detection of a low or no flow condition may alter the operation of a subsequent detection action. The detection of a low or no flow condition may limit or halt the application of a heating energisation signal to a heating element of the inspiratory conduit. The detection of a low or no flow condition may alter the operation of a humidifier of the humidification system.

[0006] In other circumstances, the desired flow of gases may be prevented by an incorrect connection of one or more components of the humidification system. For proper functioning of a humidification system the gases flow should flow in a normal (that is, correct or operative or therapeutic) direction from the gases source through the humidifier to the patient, and the components of the humidification system should be connected correctly in order to facilitate gases flow in the normal direction. The correct or normal direction can be termed as a forward flow direction. The correct connections and normal flow direction can ensure that the gases are delivered to the patient at a desired humidity and a desired temperature. The desired humidity is a therapeutic humidity level. Incorrect connections in the humidification system can occur between various components, for example, between two or more of the patient interface, conduits that transport gases, humidifier and / or to / from the gases source.

[0007] Incorrect connections in the humidification system (which can include at least a gases source, a dry line, a humidifier, an inspiratory conduit, a patient interface, an expiratory conduit, and any connectors therebetween) can be due to a set up error. The gases source can include one or more sources of respiratory gases, which will be shortened to "gases source" throughout this disclosure. Caregivers can incorrectly couple conduits that have the corresponding end connectors of the same type, such as the 22 mm male and female medical taper connectors or other standard connectors. The caregiver can connect the humidifier and gases source incorrectly (for example, such that the gas does not flow from the gases source to the humidifier). Nonstandard connections may help ameliorate this issue, such as, for example, at the humidifier outlet, on the inlet and outlet of the gases source or on a conduit. However, this can cause manufacturing complexities and increase costs, and / or may be confusing for the caregiver or user. Moreover,some connections may be standardized connectors required by regulations and / or by commercial necessity, which may not be feasibly changed to a non-standard connector. Other components of the humidification system can also be incorrectly connected to each other.

[0008] The incorrect connections can result in reverse flow conditions. A reverse flow condition can be a condition when the gases flow in the wrong (that is, incorrect or reverse) direction as compared to a forward flow direction (that is, desired or therapeutic or normal direction).

[0009] Incorrect connections of the components can result in the gases being delivered to the patient outside therapeutic humidity ranges and / or outside desired temperature or therapeutic temperature ranges. This can lead to unsatisfactory treatments, discomfort, and / or adverse reactions in the patient. For example, dry air can be delivered from the gases source directly to the patient, whereas heated and / or humidified gases can be delivered to the gases source. In this regard, such incorrect configuration can result in the humidifier being bypassed, resulting in dry gas being delivered to the patient. Dry gases can cause discomfort and / or may also cause damage to the patient's airways. In some examples, incorrect connections can cause exhaled air from the patient to be delivered to the humidifier. In a reverse flow condition, damage can also occur to the gases source (for example, the ventilator or other gases source) due to provision of humidity to the gases source. The humidity provided to the gases source can cause condensate formation that can damage the gases source.

[0010] A reverse flow condition can be indicative of incorrect connections or an incorrect set up by a clinician or nurse. Humidification systems of the present disclosure can automatically detect incorrect connections and optionally alert a user. The system can detect errors in the connections between components such as for between patient interface, humidifier, and / or gases source, in the system. Humidification systems of the present disclosure can detect incorrect conduit connection within the system. Humidification systems of the present disclosure can detect the existence of a reverse flow condition (that is, a condition where gases are flowing in the wrong direction) where a patient is receiving sub-optimal humidity and / or temperature. The methods disclosed herein can detect if the gases are flowing in the wrong direction. The wrong direction is a reverse flow direction. A reverse flow condition detected by the methods described herein likely indicates errors in the connections between two or more components of the humidification system. The incorrect connection can include improper connection and / or disconnection of the expiratory conduit. The reverse flow condition detection can include warning a user. The detection may include adjusting the controller of the humidifier. The disclosed methods may also determine a fault or an incorrect operation parameter detected in the system, which is indicative of incorrect connections in the system (that is, incorrect connections between components in the system).

[0011] The present disclosure also relates to detection of low or no flow conditions and reverse flow conditions of the expiratory conduit of dual-limb systems, such as systems used for providing invasive mechanical ventilation therapies, non-invasive mechanical ventilation therapies, neonatal invasive or non-invasive therapies and / or other therapies.

[0012] It is an object of the disclosure to provide improved systems and methods for detecting incorrect flow conditions in a respiratory humidification system that address or ameliorate one or more disadvantages or limitations associated with the prior art, or at least provide the public with a useful choice.

[0013] In a first aspect, the disclosure provides a detector of a low or no flow condition of a respiratory humidification system, the detector comprising: an inspiratory conduit configured to deliver gases to a patient, the inspiratory conduit comprising an inspiratory conduit heating element, an inspiratory temperature sensor located downstream, under a normal flow direction, of at least a portion of the inspiratory conduit heating element, and a controller configured to be in electrical connection with the inspiratory temperature sensor and the inspiratory conduit heating element, and to detect a low or no flow condition by being configured to: apply a low or no flow characteristic energisation signal to the inspiratory conduit heating element, capture, subsequently to the application of the low or no flow characteristic energisation signal to the inspiratory conduit heating element, a signal from the inspiratory temperature sensor, process the captured signal to obtain a processed signal output, and determine whether the processed signal output satisfies a criterion, wherein the low or no flow condition is detected when the processed signal output satisfies the criterion.

[0014] The detector further comprises a flow sensor configured to detect gases flow within the respiratory humidification system.

[0015] The flow sensor is located at an outlet of a humidifier and / or of a humidification chamber of a humidifier of the respiratory humidification system.

[0016] The controller is configured to be in electrical connection with the flow sensor and is configured to detect a low or no flow condition when a sensed flow rate is less than a flow threshold.

[0017] The flow threshold is a minimum acceptable reading of the flow sensor.

[0018] The controller captures the signal from the inspiratory temperature sensor a first predetermined time period after applying the low or no flow characteristic energisation signal to the inspiratory conduit heating element.

[0019] The controller is configured to process the captured signal and obtain the processed signal output by an application of a Fourier T ransformation to the captured signal.

[0020] The Fourier T ransformation may involve a discrete Fourier T ransformation such as Goertzel algorithm or a Fast Fourier T ransformation.

[0021] A chamber outlet temperature of a humidifier of the respiratory humidification system is configured to be maintained substantially constant while the controller detects a low or no flow condition.

[0022] Maintaining the chamber outlet temperature comprises keeping the chamber outlet temperature constant for a predetermined period and / or maintaining it within a tolerance range.

[0023] Maintaining the chamber outlet temperature comprises maintaining a constant chamber outlet temperature set point for a predetermined period and / or maintaining it within a tolerance range.

[0024] The controller is configured to apply a heating energisation signal to the inspiratory conduit heating element, and where the heating energisation signal is applied during detecting a low or no flow condition, the low or no flow characteristic energisation signal is superimposed on the heating energisation signal.

[0025] Upon detecting a low or no flow condition the controller is configured to limit the heating energisation signal applied to the heating element.

[0026] Upon detecting a low or no flow condition the controller is configured to reduce and / or limit the heating energisation signal applied to the inspiratory conduit heating element by applying a duty cycle limit.

[0027] The duty cycle limit is a fixed duty cycle limit, and the fixed duty cycle limit is applied for a given range of gases flow rates of the respiratory humidification system.

[0028] The fixed duty cycle limit is applied, following the detection of a low or no flow condition, when a sensed flow rate is about 0 to about 0.3 L / min.

[0029] The controller is further configured, independent of the detection of a low or no flow condition, to apply a variable duty cycle limit to reduce and / or limit, as a function of a gases flow rate of the respiratory humidification system, the heating energisation signal applied to the inspiratory conduit heating element.

[0030] Upon detecting a low or no flow condition the controller is configured to halt applying the heating energisation signal to the inspiratory conduit heating element.

[0031] Upon detecting a low or no flow condition the controller is configured to delay further detection of a low or no flow condition for a second predetermined time period.

[0032] A normal flow condition is detected when the processed signal output does not satisfy the criterion, and the controller is configured upon detecting a normal flow condition toapply or continue the application of the heating energisation signal to the inspiratory conduit heating element until a subsequent detection of a low or no flow condition.

[0033] Upon detecting a low or no flow condition the controller is configured to one or more of: a) generate an alarm, b) generate an alert to a user to check for obstruction of a gases flow path of one or more of the inspiratory conduit, other gases conduits, and a patient interface of the respiratory humidification system, and c) send a or the alert to a ventilator of the respiratory humidification system.

[0034] The inspiratory temperature sensor is located downstream of the inspiratory conduit heating element.

[0035] The inspiratory conduit comprises the inspiratory temperature sensor, and the inspiratory temperature sensor is located at or near a patient end of the inspiratory conduit.

[0036] The low or no flow characteristic energisation signal comprises at least one period of a varying energisation signal.

[0037] The low or no flow characteristic energisation signal is defined by a frequency and / or period.

[0038] The low or no flow characteristic energisation signal is distinct from a or the heating energisation signal.

[0039] The captured signal comprises at least one period of the low or no flow characteristic energisation signal.

[0040] The controller is configured to perform one or more of the following preliminary steps before detecting a low or no flow condition: instructing a ventilator of the respiratory humidification system to conduct a test, ensuring that a chamber outlet temperature of a humidifier sensed by a chamber outlet temperature sensor and a sensed temperature of the inspiratory temperature sensor are below a threshold temperature, such as optionally about 42 degrees Celsius, ensuring that an energisation signal provided to a humidifier heat source of the respiratory humidification system has been maintained within a predetermined range for a predetermined preceding period and / or will be maintained substantially constant for a subsequent period corresponding to the time required to operate the detection of a low or no flow condition, and checking that a chamber outlet temperature of a humidifier sensed by a chamber outlet temperature sensor has been substantially constant for a predetermined preceding period.

[0041] The controller is configured to perform one or more of the following preliminary steps before detecting a low or no flow condition: instructing a ventilator of the respiratory humidification system to conduct a test,ensuring that a chamber outlet temperature of a humidifier sensed by a chamber outlet temperature sensor and a sensed temperature of the inspiratory temperature sensor are below a threshold temperature, such as optionally about 42 degrees Celsius, ensuring that an energisation signal provided to a humidifier heat source of the respiratory humidification system has i) been maintained within a predetermined range for a predetermined preceding period and / or ii) will be maintained substantially constant for a subsequent period corresponding to a time required to operate the detection of a low or no flow condition, and / or iii) has maintained the humidifier heat source to an at least substantially constant temperature for a predetermined preceding period, controlling the humidifier heat source to a constant temperature, controlling the energisation signal provided to the humidifier heat source to provide a constant power delivery to the humidifier heat source, and checking that a chamber outlet temperature of a humidifier sensed by a chamber outlet temperature sensor has been substantially constant for a predetermined preceding period.

[0042] The controller is configured to check that a humidifier heat source set point has been substantially constant for a predetermined preceding period.

[0043] The controller is configured to check that a chamber outlet temperature set point of a humidifier has been substantially constant for a predetermined preceding period.

[0044] The step of ensuring the chamber outlet temperature and the sensed temperature of the inspiratory temperature sensor are below a threshold temperature comprises comparing both of the chamber outlet temperature and sensed temperature of the inspiratory temperature sensor to the threshold temperature.

[0045] The step of ensuring the chamber outlet temperature and the sensed temperature of the inspiratory temperature sensor are below a threshold temperature comprises respectively controlling the energisation signal provided to the humidifier heat source and the heating energisation signal applied to the inspiratory conduit heating element until the chamber outlet temperature and sensed temperature of the inspiratory temperature sensor are below the threshold temperature.

[0046] Where if one or more of the preliminary steps are not satisfied, the controller does not conduct the detection of a low or no flow condition.

[0047] The controller is further configured to filter out frequencies within one or more predetermined ranges from the signal from the inspiratory temperature sensor before capturing the signal from the inspiratory temperature sensor.

[0048] The controller is configured to conduct the filtering before applying the low or no flow characteristic energisation signal to the inspiratory conduit heating element.

[0049] The controller is configured to apply a delay between applying the low or no flow characteristic energisation signal to the heating element and capturing the signal from the inspiratory temperature sensor.

[0050] The processed signal output is a value.

[0051] The criterion is a threshold of the processed signal output.

[0052] The processed signal output is a series of values.

[0053] The criterion is a series of thresholds of the processed signal output.

[0054] The criterion is a pattern.

[0055] The detector is a detector of a low or no flow condition of an inspiratory portion of a respiratory humidification system.

[0056] The detector is a detector of a low or no flow condition of the inspiratory conduit or a patient interface of a respiratory humidification system.

[0057] In a further aspect, the disclosure provides a method of detecting a low or no flow condition of a respiratory humidification system and detecting a low water or water-out condition in a humidifier of the respiratory humidification system, the method comprising the steps of: detecting using a controller a low or no flow condition of the respiratory humidification system by: applying a low or no flow characteristic energisation signal to an inspiratory conduit heating element, capturing a signal from an inspiratory temperature sensor located downstream of at least a portion of the inspiratory conduit heating element, processing the captured signal to obtain a processed signal output, and determining, when the processed signal output satisfies a criterion, the existence of a low or no flow condition of the inspiratory conduit, and detecting a low water or water-out condition in the humidifier, wherein the step of detecting a low or no flow condition is executed before the step of detecting a low water or water-out condition in the humidifier.

[0058] The method further comprises the step of detecting the flow direction of gases flow within the inspiratory conduit and / or patient interface by: applying a low or no flow characteristic energisation signal to the inspiratory conduit heating element, capturing, subsequently to the application of the low or no flow characteristic energisation signal to the inspiratory conduit heating element, a signal from the inspiratory temperature sensor, processing the captured signal to obtain a processed signal output, and detecting a reverse flow direction of gases within the inspiratory conduit when the processed signal output satisfies a criterion,wherein the detection of the flow direction of gases flow within the inspiratory conduit and / or patient interface is conducted before the detection of a low water or water-out condition but after the detection of a low or no flow condition of the inspiratory conduit.

[0059] The processed signal output is a value.

[0060] The criterion is a threshold of the processed signal output.

[0061] The processed signal output is a series of values.

[0062] The criterion is a series of thresholds of the processed signal output.

[0063] The criterion is a pattern.

[0064] The method is a method of detecting a low or no flow condition of an inspiratory portion of a respiratory humidification system.

[0065] The method is a method of detecting a low or no flow condition of the inspiratory conduit or a patient interface of a respiratory humidification system.

[0066] In a further aspect, the disclosure provides a detector of a flow direction of gases flow within a respiratory humidification system, the system comprising: an inspiratory conduit configured to deliver gases to a patient, the inspiratory conduit comprising a heating element, a first temperature sensor located upstream of the heating element, and a controller configured to be in electrical connection with the first temperature sensor and the heating element, and to detect a flow direction of gases flow within the inspiratory conduit by being configured to: apply a low or no flow detection energisation signal to the heating element, capture, subsequently to the application of the low or no flow detection energisation signal to the heating element, a signal from the first temperature sensor, process the captured signal to obtain a processed signal output, and detect a reverse flow direction of gases within the respiratory humidification system when the processed signal output satisfies a criterion.

[0067] In a further aspect, the disclosure provides a detector of a flow direction of gases flow within a respiratory humidification system, the detector comprising: an inspiratory conduit configured to deliver gases to a patient, the inspiratory conduit comprising an inspiratory conduit heating element, a first temperature sensor located upstream of the inspiratory conduit heating element, and a controller configured to be in electrical connection with the first temperature sensor and the heating element, and to detect a flow direction of gases flow within the inspiratory conduit by being configured to: apply a reverse flow characteristic energisation signal to the inspiratory conduit heating element,capture, subsequently to the application of the reverse flow characteristic energisation signal to the inspiratory conduit heating element, a signal from the first temperature sensor, process the captured signal to obtain a processed signal output, and detect a reverse flow direction of gases within the respiratory humidification system when the processed signal output satisfies a criterion.

[0068] The controller is configured to detect the existence of a forward flow direction of gases within respiratory humidification system when the processed signal output does not satisfy the criterion.

[0069] The controller captures the signal from the first temperature sensor a first predetermined time period after applying the reverse flow characteristic energisation signal to the inspiratory conduit heating element.

[0070] The controller is configured to process the captured signal and obtain the processed signal output by the application of a Fourier T ransformation to the captured signal.

[0071] The Fourier Transformation involves an application of a discrete Fourier T ransformation such as a Goertzel algorithm or a Fast Fourier T ransformation.

[0072] Upon detecting a reverse flow direction the controller is configured to reduce and / or limit the heating energisation signal applied to the inspiratory conduit heating element by applying a duty cycle limit. The duty cycle limit is a fixed duty cycle limit, and the fixed duty cycle limit is applied for a given range of gases flow rates of the respiratory humidification system.

[0073] The fixed duty cycle limit is applied, following the detection of a low or no flow condition, when a sensed flow rate is about 0 to about 0.3 L / min.

[0074] The controller is further configured, independent of the detection of a reverse flow condition, to apply a variable duty cycle limit to reduce and / or limit, as a function of a gases flow rate of the respiratory humidification system, the heating energisation signal applied to the inspiratory conduit heating element.

[0075] Upon detecting a reverse flow direction the controller is configured to stop applying the heating energisation signal to the inspiratory conduit heating element.

[0076] Upon detecting a reverse flow condition the controller is configured to one or more of: a) generate an alarm, b) generate an alert to a user to check the connection of the inspiratory conduit and / or other gases conduits of the respiratory humidification system, and c) send a signal to a ventilator of the respiratory humidification system.

[0077] The detector further comprises a second temperature sensor located downstream of at least a portion of the inspiratory conduit heating element, and the controller is configured to: capture, subsequently to the application of the reverse flow characteristic energisation signal to the inspiratory conduit heating element, a signal from the second temperature sensor,process the captured signal from the second temperature sensor to obtain a second processed signal output, and detect a forward flow condition of gases within respiratory humidification system when the second processed signal output satisfies a second criterion.

[0078] The processed signal output is a value.

[0079] The criterion is a threshold of the processed signal output.

[0080] The processed signal output is a series of values.

[0081] The criterion is a series of thresholds of the processed signal output.

[0082] The criterion is a pattern.

[0083] The detector is a detector of flow direction of gases flow within an inspiratory portion of a respiratory humidification system.

[0084] The detector is a detector of flow direction of gases flow within an inspiratory conduit and / or patient interface of a respiratory humidification system.

[0085] In a further aspect, the disclosure provides a method of detecting a flow direction of gases flow within a respiratory humidification system and detecting a low or no flow condition of a respiratory humidification system, the method comprising the steps of: detecting a flow direction of gases flow within an inspiratory conduit of a respiratory humidification system, and detecting a low or no flow condition of the respiratory humidification system by: applying by a controller a characteristic energisation signal to an inspiratory conduit heating element, capturing by the controller a signal from a second temperature sensor located downstream of at least a portion of the inspiratory conduit heating element, processing the captured signal to obtain a processed signal output, and determining, when the processed signal output satisfies a criterion, the existence of a low or no flow condition of the respiratory humidification system, and wherein the step of detecting a flow direction of gases flow within the respiratory humidification system is executed before the step of detecting a low or no flow condition of the respiratory humidification system.

[0086] The method further comprises the step of detecting a low water or water-out condition in the humidifier, wherein the detection of a low water or water-out condition in a humidifier is conducted after the step of detecting a low or no flow condition of the respiratory humidification system.

[0087] The processed signal output is a value.

[0088] The criterion is a threshold of the processed signal output.

[0089] The processed signal output is a series of values.

[0090] The criterion is a series of thresholds of the processed signal output.

[0091] The criterion is a pattern.

[0092] The method is a method of detecting a low or no flow condition of and detecting a flow direction of gases flow within an inspiratory portion of a respiratory humidification system.

[0093] The method is a method of detecting a low or no flow condition of and detecting a flow direction of gases flow within an inspiratory conduit and / or patient interface of a respiratory humidification system.

[0094] In a further aspect, the disclosure provides a method of operating a respiratory humidification system, the method comprising: as preliminary step, detecting using a controller at least one of a low or no flow condition of the respiratory humidification system, and a flow direction of gases flow within the respiratory humidification system, and as a subsequent step, detecting a low water or water-out condition in a humidifier of the respiratory humidification system, wherein during the preliminary step the controller operates a humidifier heat source heating element to maintain a humidifier chamber outlet temperature within an acceptable range, and wherein the subsequent step of detecting a low water or water-out condition comprises energising the humidifier heat source heating element.

[0095] The subsequent step of detecting a low water or water-out condition comprises energising the humidifier heat source heating element such that the humidifier chamber outlet temperature exceeds the acceptable range.

[0096] The preliminary step comprises both detecting using a controller a low or no flow condition of the respiratory humidification system and detecting using the controller a flow direction of gases flow within the respiratory humidification system.

[0097] The detecting of a low or no flow condition and the detecting of a flow direction of gases flow are performed concurrently by the controller.

[0098] The detecting of a low or no flow condition and the detecting of a flow direction of gases flow are performed sequentially by the controller.

[0099] In a further aspect, the disclosure provides a detector of a flow condition of gases flow within a respiratory humidification system, the system comprising: a heating element, a temperature sensor, and a controller configured to be in electrical connection with the temperature sensor and the heating element, and to detect a flow condition of gases flow within the respiratory humidification system by being configured to: apply a characteristic energisation signal to the heating element,capture, subsequently to the application of the characteristic energisation signal to the heating element, a signal from the temperature sensor, process the captured signal to obtain a processed signal output, and detect the flow condition of gases flow within the respiratory humidification system when the processed signal output satisfies a criterion.

[0100] The system further comprises an inspiratory conduit configured to deliver gases to a patient, the heating element comprises an inspiratory conduit heating element, the application of the characteristic energisation signal is to the inspiratory conduit heating element, the temperature sensor comprises a first temperature sensor located upstream of the inspiratory conduit heating element, the temperature signal comprises a first captured temperature signal captured from the first temperature sensor, the processing comprises processing the first temperature signal, the processed signal output of the first temperature signal comprises a first processed signal output, the flow condition comprises a direction of gases flow, and the detected direction of gases flow is a detected direction of gases flow within the inspiratory conduit.

[0101] The system further comprises an inspiratory conduit configured to deliver gases to a patient, the heating element comprises a heating element of a humidifier heat source, the characteristic energisation signal is applied to the heating element of the humidifier heat source, the temperature sensor comprises a second temperature sensor located downstream of at least a portion of the heating element of the humidifier heat source, the temperature signal comprises a second temperature signal captured from the second temperature sensor, the processing comprises processing the second temperature signal, the processed signal output of the second temperature sensor comprises a second processed signal output, the flow condition is a low or no flow condition, and the detection of a low or no flow condition is a detection of whether gases are flowing in the inspiratory conduit.

[0102] In a further aspect, the disclosure provides a detector of a low or no flow condition of a respiratory humidification system, the detector comprising:a controller configured to be in electrical connection with a) an inspiratory temperature sensor in a downstream portion of an inspiratory conduit and b) a heating element of the inspiratory conduit, and to detect a low or no flow condition of the inspiratory conduit by being configured to: apply a characteristic energisation signal to the inspiratory conduit heating element, capture, subsequently to the application of the low or no flow characteristic energisation signal to the inspiratory conduit heating element, a signal from the inspiratory temperature sensor, process the captured signal to obtain a processed signal output, and determine whether the processed signal output satisfies a criterion, wherein the low or no flow condition is detected when the processed signal output satisfies the criterion.

[0103] The controller is further configured to be in electrical connection with a flow sensor located at an outlet of a humidifier and / or of a humidification chamber of a humidifier of the respiratory humidification system, wherein the controller is configured to detect a low or no flow condition when a sensed flow rate is less than a flow threshold.

[0104] A chamber outlet temperature of a humidifier of the respiratory humidification system is configured to be maintained substantially constant while the controller detects a low or no flow condition, and wherein maintaining the chamber outlet temperature comprises keeping the chamber outlet temperature constant for a predetermined period and / or maintaining it within a tolerance range.

[0105] The controller is configured to maintain a constant chamber outlet temperature set point and / or to maintain the chamber outlet temperature set point within a tolerance range while the controller detects a low or no flow condition.

[0106] The controller is configured to apply a heating energisation signal to the inspiratory conduit heating element, and where the heating energisation signal is applied during detecting a low or no flow condition, the low or no flow characteristic energisation signal is superimposed on the heating energisation signal.

[0107] Upon detecting a low or no flow condition the controller is configured to reduce and / or limit the heating energisation signal applied to the inspiratory conduit heating element by applying a duty cycle limit.

[0108] The duty cycle limit is a fixed duty cycle limit, and the fixed duty cycle limit is applied for a given range of gases flow rates of the respiratory humidification system.

[0109] The fixed duty cycle limit is applied, following the detection of a low or no flow condition, when a sensed flow rate is about 0 to about 0.3 L / min.

[0110] The controller is further configured, independent of the detection of a low or no flow condition, to apply a variable duty cycle limit to reduce and / or limit, as a function of a gasesflow rate of the respiratory humidification system, the heating energisation signal applied to the inspiratory conduit heating element.

[0111] In a further aspect, the disclosure provides a detector of a flow direction of gases flow within a respiratory humidification system having an inspiratory conduit configured to deliver gases to a patient, the inspiratory conduit comprising an inspiratory conduit heating element, the detector comprising: a first temperature sensor located upstream of the inspiratory conduit heating element, and a controller configured to be in electrical connection with the first temperature sensor and the heating element, and to detect a flow direction of gases flow within the inspiratory conduit by being configured to: apply a characteristic energisation signal to the inspiratory conduit heating element, capture, subsequently to the application of the characteristic energisation signal to the inspiratory conduit heating element, a signal from the first temperature sensor, process the captured signal to obtain a processed signal output, and detect a reverse flow direction of gases within the respiratory humidification system when the processed signal output satisfies a criterion.

[0112] The detector is configured to detect the existence of a forward flow direction of gases within respiratory humidification system when the processed signal output does not satisfy the criterion.

[0113] The detector further comprises a second temperature sensor located downstream of at least a portion of the inspiratory conduit heating element, and the controller is configured to: capture, subsequently to the application of the characteristic energisation signal to the inspiratory conduit heating element, a signal from the second temperature sensor, process the captured signal from the second temperature sensor to obtain a second processed signal output, and detect a forward flow direction of gases within respiratory humidification system when the second processed signal output satisfies a second criterion.

[0114] Upon detecting a reverse flow direction the controller is configured to limit the heating energisation signal applied to the inspiratory conduit heating element.

[0115] In a further aspect, the disclosure provides a method of operating a respiratory humidification system comprising a gases source and a humidifier, the method comprising the step of: operating, by a controller of the respiratory humidification system, at least one of the following tests: a breathing circuit test, an inspiratory and / or expiratory tube compliance test, a test for resistance to flow,a barometric pressure test, a gas supply test, an internal leakage test, a test of a safety valve, a test of sensors connected to the controller, a test of an alarm state of the respiratory humidification system, and a test of an alarm output connection.

[0116] The controller operates at least one of the tests upon the activation of the respiratory humidification system.

[0117] The controller operates at least one of the tests during the operation of the respiratory humidification in response to a change within the respiratory humidification system.

[0118] The change within the respiratory humidification system includes a disconnection or connection of a gases conduit at an inlet or outlet of the respiratory humidification system.

[0119] The tests are only performed where the sensed water level in a chamber of the humidifier is at or above an acceptable level.

[0120] As used herein the term "and / or" means "and" or "or", or both.

[0121] As used herein "(s)" following a noun means the plural and / or singular forms of the noun.

[0122] For the purpose of this specification, where method steps are described in sequence, the sequence does not necessarily mean that the steps are to be chronologically ordered in that sequence, unless there is no other logical manner of interpreting the sequence.

[0123] The term "comprising" as used in the specification and claims means "consisting at least in part of." When interpreting each statement in this specification that includes the term "comprising," features other than that or those prefaced by the term may also be present. Related terms "comprise" and "comprises" are to be interpreted in the same manner.

[0124] Throughout this disclosure, the term "circuit" or "breathing circuit" may refer to a gases pathway that is configured to transport gases and generally includes one or more conduits that are interconnected to define a gases path. The circuit may also include a humidification chamber, which also forms part of the gases pathway.

[0125] Throughout this disclosure, the term "conduit" may refer to an individual component of a gases pathway or circuit, and may be a tube with connectors on both ends of the tube.

[0126] Throughout this disclosure, the terms "inlet," "outlet," "inspiratory conduit,""expiratory conduit," "dryline" or "dryline conduit," "patient end," "upstream," "downstream" and the like refer to the intended gases pathway coupling and normal flow direction, regardless of the actual coupling and flow direction.

[0127] Throughout this disclosure, a controller can be one or more hardware processors executing software instructions that cause the one or more hardware processors to perform tasks specified by the software programming.

[0128] This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

[0129] To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting.

[0130] Other aspects of the invention may become apparent from the following description which is given by way of example only and with reference to the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0131] Preferred embodiments of the invention will be described byway of example only and with reference to the drawings, in which:

[0132] Figure 1 shows a schematic representation of a respiratory humidification system.

[0133] Figure 2 shows a schematic representation of a further configuration of a respiratory humidification system.

[0134] Figure 3 shows a schematic representation of a further configuration of a respiratory humidification system.

[0135] Figure 4 shows a schematic representation of a further configuration of a respiratory humidification system.

[0136] Figure 5 shows a schematic representation of a further configuration of a respiratory humidification system.

[0137] Figure 6 shows a schematic representation of a further configuration of a respiratory humidification system.

[0138] Figure 7 shows a low or no flow detection process.

[0139] Figure 8 shows another low or no flow detection process.

[0140] Figure 9 shows a further configuration of a low or no flow detection process.

[0141] Figure 10 shows a process for detecting low or no flow and / or reverse or forward flow.

[0142] Figure 11 shows a process for combining multiple detection processes.

[0143] Figure 12 shows another a process for combining multiple detection processes.

[0144] Figure 13 shows an example characteristic energisation signal.

[0145] Figure 14 shows another example characteristic energisation signal.

[0146] Figure 15 shows another example characteristic energisation signal.

[0147] Figure 16 shows a process for applying a characteristic energisation signal and making one or more determinations based on it.

[0148] Figure 17 shows a schematic of an example surgical apparatus.DETAILED DESCRIPTION

[0149] Figures 1 and 2 illustrate schematic representations of an example dual-limb humidification system 1 .

[0150] Referring to Figure 1 , an example respiratory humidification system 1 for providing respiratory therapy to a patient is shown in partial cutaway. The respiratory humidification system 1 has a gases source 10, a dryline conduit 30, a humidifier 20, an inspiratory conduit 40, a wye-piece 60, a patient interface 70 and an expiratory conduit 50.

[0151] The respiratory humidification system 1 may be for use by one or more different patient types. Patient types may include, for example, infant or neonatal patients, paediatric patients, adult patients, or the like. One or more different forms of breathing circuits may be associated with one or more different patient types. For example, a neonatal circuit may be associated with an infant or neonatal patient, or a paediatric circuit may be associated with a paediatric patient, or an adult circuit may be associated with an adult patient.

[0152] The respiratory humidification system 1 may be operable in one or more therapy modes. The respiratory humidification system 1 may query a user of the system as to a desired therapy mode (based on, e.g., patient type and breathing circuit type, or both) or system parameter settings (such as set points for temperature or flow sensors and the like). This querying may be accomplished via any suitable user interface, display, and / or input device as are known in the art and as described herein.

[0153] Therapy modes may include, for example, high flow therapy modes (as will be subsequently described in further detail), non-invasive ventilation modes (generally through a sealed interface, such as a mask), and invasive ventilation modes (where the patient's upper airway is bypassed), or the like. One or more of the therapy modes may be suitable for anaesthesia (generally for an apnoeic patient under general anaesthesia via an unsealed interface at gas flows above 30 L / min).

[0154] In this disclosure the example of a gases source is a ventilator, for example, a ventilator configured to entrain ambient air. Other gases sources may also be used, for example, a wall gases source or a compressed gas tank. Supply of gases can be, for example, ambient air and / or from a wall / bottle source (such as oxygen).

[0155] The gases source 10 may include a pressure generator 11 , such as a blower. The pressure generator 11 draws ambient air into the gases source 10 through a gas inlet and pressurizes it above ambient pressure to generate a supply of respiratory gases. The ambient air may be supplemented with other gases, such as supplementary oxygen, nitric oxide, or the like (not shown).

[0156] The gases source can also include a high flow gases source configured to deliver high flow of air or gases in a high flow therapy mode, for example, in excess of 30 L / min and / or up to 120 L / min. The gases source can be configured to deliver gases flow rates in other ranges e.g. for neonatal or paediatric applications the flow rates can often be less than 8 L / min. Gases supplied by the gases source can include either dry air, ambient air, oxygen, and / or a mixture of those or other gases (for example, therapeutic gases or breathing gases). The gases from a gases source outlet 12 can optionally include dry gases.

[0157] A desired therapy to be delivered by the respiratory humidification system 1 may be associated with flow rates lower than about 2 L / min. For example, a desired therapy to be delivered to an adult may involve flow rates of about 2 L / min to about 120 L / min. A desired therapy to be delivered to a child may involve flow rates of about 1 L / min to about 60 L / min. A desired therapy to be delivered to neonate may involve flow rates of about 0.5 L / min to about 40 L / min. The detection of low or no flow conditions may involve the detection of flow rates which are less than a minimum expected flow rate associated with the desired therapy that is to be delivered. The detection of low or flow conditions may additionally or alternatively involve the detection of flow rates which are less than an expected or target flow rate associated with a current portion of the desired therapy.

[0158] The gases source 10 may have one or more processors, such as hardware and / or software processors. The gases source 10 can include a gases source controller 81 which controls operation of the pressure generator 11. Control may be based on inputs received from one or more of the user interface 141 and one or more sensors (not shown). The gases source controller 81 or another controller of the system may operate to control the gases source 10 to generate a gases flow at a desired flow rate, pressure, and / or temperature.

[0159] The humidifier 20 can also optionally include one or more processors, such as hardware and / or software processors. The humidifier 20 can include a humidifier controller 82 that can include one or more processors and memory. The controller can control operation of the humidifier 20, for example, the steady state operation of the humidifier 20.

[0160] The gases source 10 supplies respiratory gases to the humidifier 20 via gases source outlet 12 and dryline conduit 30. The dryline conduit 30 can be a tube that is shaped and configured to transfer gases from a gases source to the humidifier 20. The "dryline conduit" refers to a conduit (for example, a tube or a corrugated tube) that is used to transport un-heated and / orun-humidified (for example, dry or ambient) gases from the gases source to a humidifier inlet 22 of the humidifier 20. When correctly connected (that is, in an operational configuration) the dry line conduit pneumatically connects between the gases source and the humidifier.

[0161] In the illustrated example, the humidifier 20 may be an active (heated) pass-overtype humidifier. A humidification chamber 26 may be associated with a humidifier heat source, for example it may sit atop a heater base 90 otherwise be in thermal contact with the heater base 90. The heater base 90 may include a heating element. The heater base 90 also heats and / or humidifies the gases passing through the humidification chamber 26 to a desired temperature (for example, a therapeutic temperature). The humidification chamber 26 may be removably engaged with the heater base 90. A volume of water within the humidification chamber 26 is heated to heat and / or humidify gases in the headspace of the humidification chamber 26. The respiratory gases are received from the dryline conduit 30 at an inlet to the humidification chamber 26. The respiratory gases may pass through the headspace of the humidification chamber 26, picking up the water vapor, to an outlet of the humidification chamber 26 and then to the inspiratory conduit 40.

[0162] The heater base 90 may be controlled by the humidifier controller 82 based on inputs from one or more of a user interface 142 and one or more sensors to achieve a desired level of one or more of heating and humidification of the respiratory gases.

[0163] The humidifier controller 82 of the humidifier 20 may control the temperature of the heater base 90. The heater base 90 may be controlled so that the humidified respiratory gases are received by the patient at, or near, a predetermined temperature and humidity.

[0164] One or more of the desired temperature and humidity of the respiratory gases may be adjustable using the user interface 142. Alternatively, or additionally, the humidifier 20 and the gases source 10 may be in electronic communication with each other whereby settings of the humidifier 20 may be viewed and / or adjusted from the gases source 10, or vice versa. The humidifier controller 82 may receive signals from one or more sensors to provide open- or closed- loop control of one or more of the temperature and humidity of the respiratory gases.

[0165] The respiratory humidification system 1 of Figure 1 illustrates the gases source 10 and humidifier 20 as separate devices. In other examples, the gases source 10 and humidifier 20 may be integrated with each other. In such examples, the dryline conduit 30 may be, or may include, internal ducting within the housing of the integrated device. The functions of the gases source controller 81 and humidifier controller 82 may be performed by a single controller or a distributed control system. Similarly, the user interface 141 and the user interface 142 may be replaced by a single user interface which may receive inputs for control of both the pressure generator 11 and the heater base 90.

[0166] Referring still to the example respiratory humidification system 1 of Figure 1 , the respiratory gases are conveyed from the humidifier 20 towards the patient by an inspiratoryconduit 40. The inspiratory conduit 40 can be a gas delivery conduit that carries gases from the humidifier to a patient interface 70. The inspiratory conduit 40 can pneumatically couple the patient interface 70 and the humidifier 20. The inspiratory conduit 40 can be coupled to a patient interface 70 (i.e. optionally omitting the wye-piece 60, especially for therapies in which an expiratory conduit is not needed).

[0167] Although the patient 2 is illustrated as wearing a nasal mask in Figures 1 and 2, a person of ordinary skill in the art would appreciate from the disclosure herein that the patient 2 can be wearing other types of patient interfaces 70 disclosed herein, such as a sealed or unsealed nasal cannula, an oronasal (or full-face) mask, an endotracheal tube, or a combination thereof. The patient interface 70 can also include an interface tube, which is a short section of tube, which may be heated or unheated, and the inspiratory conduit 40 can be coupled or connected to the interface tube. The short section of tube may be a breathable tube. The short section of tube can decouple the patient interface from the weight of the inspiratory conduit to prevent the patient interface from being dislodged. Alternatively, the inspiratory conduit 40 can be coupled to a wye-piece 60 at an inspiratory conduit connection port. The wye-piece 60 can be connected to the patient interface 70 at a patient interface connection portion.

[0168] The patient interface for use in a high flow therapy can be a non-sealing interface to prevent barotrauma, which can include tissue damage to the lungs or other organs of the patient's respiratory system due to difference in pressure relative to the atmosphere. The patient interface can be a nasal cannula with a manifold and nasal prongs, and / or a face mask, and / or a nasal pillows mask, and / or a nasal mask, and / or a tracheostomy interface, or any other suitable type of patient interface.

[0169] The inspiratory conduit 40 can have a heating element 41 to reduce or prevent condensate formation. Examples of the inspiratory conduit heating element can include a heater wire, heating tape, and / or water jacket heating. Condensate can be formed when a temperature of the heated and / or humidified gases leaving the humidifier 20 drops below the dew point temperature due to heat loss when the gases travel through an unheated inspiratory conduit 40. The heating element 41 may be powered by the humidifier 20. The heating element 41 may be controlled by the humidifier controller 82 to mitigate heat loss of the respiratory gases as they pass along the length of the inspiratory conduit 40. In some examples, the heating element 41 may maintain, or in some cases increase, the temperature of the respiratory gases as they pass along the length of the inspiratory conduit 40. The heating element may be spirally wound along the lumen of the conduit, loosely laid along the length of the conduit, spirally wound embedded in the wall of the conduit, otherwise embedded in the wall of the conduit, or disposed around the outer surface of the conduit.

[0170] Sensors can be placed in various locations in the humidification system. For example, the sensors can include flow rate, pressure, temperature, and / or humidity sensors. The sensors can comprise a thermistor. The thermistor can act as a temperature sensor and can be switched to act as a flow sensor by applying a voltage to the thermistor to heat the thermistor. Output of the sensors can be received by the controllers to assist the controllers to operate the humidification system 1 in a manner that can provide optimal therapy. Other sensors that may be used include thermocouples, thermostats, semiconductor sensors, infrared sensors, and resistive temperature devices. Types of humidity sensors that may be used can include capacitive humidity sensor, chilled mirror hygrometer, dry bulb humidity sensor, wet bulb humidity sensor, and the like. Types of flow sensors that may be used include differential pressure sensors, mass flow sensors, a heated bead thermistor as described above, and the like.

[0171] A chamber outlet flow sensor 27 may be provided to sense a flow of gases at or proximate to the chamber outlet. A chamber outlet temperature sensor 28 may be provided to sense temperature of gases at or proximate to the chamber outlet. The chamber outlet flow sensor 27 and chamber outlet temperature sensor 28 may be associated with the chamber outlet. The chamber outlet flow sensor 27 and chamber outlet temperature sensor 28 may be associated with the inspiratory conduit 40, either with the conduit itself or with a connector of the conduit which is for association to the chamber outlet.

[0172] A patient interface end of the inspiratory conduit 40 can include an inspiratory temperature sensor 29, humidity sensor, and / or flow rate sensor.

[0173] Sensor probes 136 may be removably inserted in apertures at the patient end and the humidifier end of the inspiratory conduit 40. The sensor probes 136 may include one or more of temperature, humidity and flow sensors, for example. Sensor leads 138 may connect the sensor probes 136 to the humidifier 20, so that signals from the sensor probes 136 may be used as inputs in the control algorithms for one or more of the pressure generator 11 , heater base 90 and heating element 41. In other examples, the sensors may be integrated in one or more of the humidifier 20 and the inspiratory conduit 40. In some examples, one or more of the sensor leads 138 may be embedded in the tube wall or located in the lumen. In some examples, one or more sensors may be integrated in the inspiratory conduit 40.

[0174] The inspiratory conduit 40 may be provided with connectors at opposing ends to establish and maintain respective pneumatic connections with an outlet of the humidification chamber 26 and an inlet of the wye-piece 60.

[0175] In some examples, the connector at the humidifier end of the inspiratory conduit 40 may have a socket for receiving the sensor probe 136. In some examples, the connector at the humidifier end of the inspiratory conduit 40 may have a socket for establishing an electrical connection between the humidifier 20 and the heating element 41 . In other examples, the humidifier20 and the connector may have corresponding integrated electrical contacts whereby both pneumatic and electrical connections may be established in a single action upon physically connecting the inspiratory conduit 40 to the humidifier 20.

[0176] The respiratory gases are delivered by the inspiratory conduit 40 to the wye-piece 60 adjacent, or near, the patient. The wye-piece 60 fluidly couples the inspiratory conduit 40 (via the inlet of the Y-piece), the patient interface 70 (via a patient in let / outlet of the Y-piece) and the expiratory conduit 50 (via an outlet of the Y-piece). It is to be appreciated that while the three limbs (inlet, outlet and patient i n let / outlet) of the wye-piece 60 in this example form a Y-shape, the term is not intended as being limited to this particular configuration.

[0177] The humidification system 1 can include an expiratory conduit 50 (that is, a gases transport conduit or expired gases transport conduit). The expiratory conduit 50 can be a gas transport conduit that directs gases away from the patient. The expiratory conduit 50 can direct expired gases away from the patient and transport the expired gases to the gases source or to some other device (for example, a vent) that may release the gases to atmosphere. The expiratory conduit 50 can direct gases expired from the patient 2 back to a gases source inlet 14. The expiratory conduit 50 can include an expiratory conduit heating element, such as a heater wire, heating tape, and / or water jacket heating. The heating element may be spirally wound along the lumen of the conduit, loosely laid along the length of the conduit, spirally wound embedded in the wall of the conduit, otherwise embedded in the wall of the conduit, or disposed around the outer surface of the conduit.

[0178] An expiratory conduit of breathable material may be heated or unheated. In this regard, gases can be dried while travelling through the expiratory conduit 50.

[0179] Optionally, the expiratory conduit 50 can be formed of a breathable material such that moisture within the expired gases are transferred from the expired gas to the atmosphere. Further disclosure of components for medical circuits and in particular conduits of breathable materials are disclosed in the applications US 09 / 850,797 published as US 2001 / 0054422 on 27 December 2001 , PCT / IB2010 / 003454, published as WO / 2011 / 077250 on 30 June 2011, and PCT / NZ2023 / 050040, published as WO / 2023 / 195865 on 12 October 2023, each of which are incorporated by reference herein in their entireties.

[0180] The dryline conduit 30, humidification chamber 26, inspiratory conduit 40, Wye- piece 60 and expiratory conduit 50 together form a breathing circuit. More specifically, this particular configuration forms a dual limb breathing circuit.

[0181] Figure 2 illustrates a further example respiratory humidification system 1 providing respiratory therapy. Like the respiratory humidification system of Figure 1 , respiratory humidification system 1 of Figure 1 has a gases source 10, a dryline conduit 30, a humidifier 20, an inspiratory conduit 40, a wye-piece 60, a patient interface 70 and an expiratory conduit 50. Exceptas described below or otherwise apparent from the drawings, respiratory humidification system 1 of Figure 2 is similar to the respiratory humidification system 1 of Figure 1 and the description of the respiratory humidification system 1 of Figure 1 is intended to apply equally to the respiratory humidification system 1 of Figure 2.

[0182] In some examples, a heating element 41 and heating element 51 may be provided in each of, respectively, the inspiratory conduit 40 and the expiratory conduit 50. But in some examples, at least the heating element 51 in the expiratory conduit 50 may be omitted.

[0183] The heating element 51 in the expiratory conduit 50 may be wrapped around the outside of the tube wall, embedded within the tube wall, or located in the lumen of the expiratory conduit 50, for example.

[0184] The heating element 51 may be powered by the humidifier 20. The heating element 51 may be controlled by the humidifier controller 82 to mitigate heat loss of the respiratory gases as they pass along the length of the expiratory conduit 50. In some examples, the heating element 51 may be controlled to increase, maintain, or in some cases decrease, the temperature of the respiratory gases as they pass along the length of the expiratory conduit 50.

[0185] A sensor 135 (e.g., one or more of a temperature, humidity, and flow sensor) may be integrated within the inspiratory conduit 40, in a connector of the inspiratory conduit 40. One or more of the sensors 135 may be electrically connected with the humidifier 20 by sensor wires embedded within the tube wall or provided within the lumen of the inspiratory conduit 40.

[0186] The inspiratory conduit 40 may have an electropneumatic connector 43 with integrated electrical contacts. The electropneumatic connector 43 may be configured to establish both pneumatic and electrical connections with the humidifier 20 in a single action upon physically connecting the connector to the humidifier 20. This may avoid the need for the removable sensor probes 136 and sensor leads 138 of the respiratory humidification system 1 shown in Figure 1.

[0187] The humidification system 1 can include a wireless data transmitter and / or receiver, or a transceiver to enable the controller 80 to receive data signals in a wireless manner from the sensors and / or to control the various components of the humidification system 1. Additionally, or alternatively, a data transmitter and / or receiver can deliver data to a remote server or enable remote control of the humidification system 1 . The system 1 can include a wired connection, for example, using cables or wires, to enable the controller 80 to receive data signals from the sensors and / or to control the various components of the humidification system 1 .

[0188] Figure 3 illustrates a schematic of an example respiratory humidification system 1 , showing componentry associated with the detection of incorrect flow conditions according to the disclosure. It will be appreciated that lines connecting elements in the schematic of Figure 3 are intended to show general relationships, and may or may not define electrical connections or direct or indirect physical proximity between elements. A controller 80 is operable to control a heatingelement of a heater base 90. The heating element of the heater base 90 operates under the control of the controller 80 to heat water within a humidification chamber 26 of a humidifier. A chamber outlet temperature sensor 28 is provided to sense the temperature associated with an outlet of the humidification chamber 26 and is in electrical communication with the controller 80. The chamber outlet temperature sensor 28 may be located at an outlet of the humidification chamber 26. The chamber outlet temperature sensor 28 may in other arrangements be located the inspiratory conduit, for example in a connector of the inspiratory conduit. Where the chamber outlet temperature sensor 28 is located in the inspiratory conduit it may be located so that it is proximate to the humidifier and more particularly the chamber outlet of the humidification chamber 26.

[0189] A chamber outlet flow sensor 27 may also be provided in electrical communication with the controller, to sense a gases flow at the outlet of the humidification chamber 26.

[0190] An inspiratory conduit 40 has a heating element 41 , which is operated by the controller 80 to heat the inspiratory conduit and a gases flow therethrough. An inspiratory temperature sensor 29 is provided at a patient end of the respiratory humidification system 1 and is in electrical communication with the controller 80. For example, the inspiratory temperature sensor 29 may be located at a patient end of the inspiratory conduit 40 or a connector of the inspiratory conduit 40. In other examples, the patient end temperature sensor may be located at the patient interface 70.

[0191] According to the schematic of Figure 3, the controller 80 may operate the heating element of a heater base 90, which heats and / or humidifies air passing through the humidification chamber 26. The temperature and optionally flow rate of heated and / or humidified gases exiting the chamber may be sensed by, respectively, the chamber outlet temperature sensor 28 and chamber outlet flow sensor 27. The controller may also operate to energise the heating element 41 , to heat the inspiratory conduit 40 and the heated and / or humidified gases passing through it. The temperature of the gases at the patient end of the respiratory humidification system 1 are sensed by the inspiratory temperature sensor 29. The controller 80 is configured to receive information from each of the sensors in order to control the operation of the humidification system.

[0192] Example methods of detecting incorrect flow conditions in a humidification system, such as the humidification system 1 , will now be described. These are examples only, and it should be appreciated that other incorrect flow conditions may occur and may be detected according to the disclosure.

[0193] In Figures 1, 2, and 4-6 the arrows of each of the dryline conduit 30, inspiratory conduit 40, and expiratory conduit 50 indicate the direction of gases flow within the respective conduits for the shown connection configurations of the conduits to the gases source 10, humidifier 20, and patient interface 70. As seen in Figures 1 and 2 the arrows indicating thedirection of gases flow within the respective conduits is the normal or correct direction of flow that is associated with the delivery of the desired therapy.

[0194] The individual conduits may or may not be connected in a particular orientation relative to a respective two of the gases source 10, humidifier 20, or patient interface 70.

[0195] Referring to Figure 17 an example of a surgical apparatus 600 is shown. The surgical apparatus 600 may be configured to supply an insufflation gas to a body cavity of a patient, e.g., for laparoscopic, robotic or open surgery procedures.

[0196] The surgical apparatus 600 may comprise one or more components. The one or more components may be part of a conduit system. The one or more components may be for example any combination of: one or more conduits 602, 606, 616, 622, insufflation gas filters (for example discharge filter 618), or a patient interface 608 (for example as a patient interface component).

[0197] In some examples, the insufflation gas may be carbon dioxide. In some examples, the insufflation gas may be air. In some examples, the insufflation gas may be a mixture of gases. In some examples, a medicament may be added to the insufflation gas.

[0198] The insufflation gas may be pressurized to a pressure above atmospheric pressure. The insufflation gas may create a working space within the body of the patient, e.g., the abdominal or peritoneal cavity, for a surgeon or surgical team to carry out a surgical procedure. The surgical procedure may involve cauterization creating surgical smoke in the working space.

[0199] The surgical apparatus 600 may include one or more of a gases source (for example, 612 and / or 614), an insufflator supply conduit 602, an insufflator 604, an insufflation gas filter (not shown), a humidifier supply conduit 104, a surgical apparatus 106 (in this example a humidifier), a delivery conduit 606, a patient interface 608 and a smoke evacuation system 610. In other examples, the surgical apparatus may include a recirculation system (not shown), e.g., in place of the smoke evacuation system 610.

[0200] In some examples, the surgical apparatus comprises insufflator 604 and humidifier 106. In other examples, the surgical apparatus comprises only the surgical apparatus 106, or only the insufflator 604.

[0201] The gases source 102 may be a wall source 612 or a compressed gas cylinder 614, for example. In other examples, the insufflator may be configured to pressurize ambient air.

[0202] The patient interface 608 may be a surgical cannula or other surgical access device.

[0203] One or more insufflation gas filters may be provided between the insufflator 604 and the patient interface 608. An insufflation gas filter may be provided between the insufflator 604 and the surgical apparatus 106, e.g., between an outlet of the insufflator 604 and an inlet end of the humidifier supply conduit. An insufflation gas filter may alternatively, or additionally, be providedbetween the surgical apparatus 106 and the patient interface 608, e.g., between an outlet of the surgical apparatus 106 and an inlet end of the delivery conduit 606.

[0204] An adapter (not shown) may be provided at the outlet of the insufflator 604, e.g., between the insufflator 604 and the insufflation gas filter or humidifier supply conduit 104.

[0205] In other examples, e.g., a surgical insufflation system configured for open surgery, the insufflation gas filter or humidifier supply conduit 104 may be connected directly to a CO2 gas supply stand gas outlet port. The patient interface 608 may be a surgical diffuser or other surgical access device.

[0206] The surgical apparatus 106 may be a humidifier. The surgical apparatus 106 may include one or more of a humidification chamber, a chamber heater, a humidifier controller and a user interface as described elsewhere herein with respect to the example respiratory humidification system 1 of Figure 1 or Figure 2.

[0207] A funnel may be provided to assist in filling a humidification chamber 126 with a liquid, e.g., sterile water, through the inlet or outlet of the humidification chamber 126.

[0208] A connector at one end of the delivery conduit 606 may be a luer lock connector. The luer lock connector may be configured to connect directly to the patient interface 608. In other examples, e.g., a surgical apparatus configured for open surgery, the delivery conduit 606 may instead be configured to be connected to a diffuser.

[0209] The delivery conduit 606 may otherwise be similar to the inspiratory conduit 40 of the respiratory humidification system 1, such as is illustrated and described in relation to Figure 1 or 2. For example, the delivery conduit 606 may have a heater, e.g., a heating element 41 as shown in Figures 1 and 2. In some examples, the delivery conduit 606 may be corrugated. In other examples, the delivery conduit may formed by at least one member which is spirally-wound about a lumen of the delivery conduit.

[0210] The smoke evacuation system 610 may include a discharge conduit 616 and a discharge filter 618.

[0211] In some examples, the discharge conduit 616 may be between about 0.8 m and 1.2 m, e.g., about 1 .0 m, in length.

[0212] The smoke evacuation system 610 may be configured to be coupled with a vacuum source 620, e.g., a wall source. In some examples, the smoke evacuation system 610 may include a further discharge conduit 622. The further discharge conduit 622 may be configured to be coupled between the discharge filter 618 and the vacuum source 620. In some examples, the further discharge conduit 622 may have generally the same construction as the discharge conduit 616. In some examples, the further discharge conduit 622 may have the same length as the discharge conduit 616. In other examples, the further discharge conduit 622 may have a differentconstruction to the discharge conduit 616. In some examples, the further discharge conduit 622 may differ from the discharge conduit 616 in one or more of length, diameter, and materials.

[0213] The recirculation system (not shown) may include the discharge conduit 616, the discharge filter 618 and a further discharge conduit that is coupled to a further surgical cannula. This may enable exhausted insufflation gas to be filtered and then recirculated back into the body cavity of the patient.

[0214] In the illustrated example surgical apparatus 600, the humidifier supply conduit 104, a humidification chamber 126, delivery conduit 606, discharge conduit 616, discharge filter 618 and further discharge conduit 622 form an insufflation circuit. More specifically, this particular configuration forms a dual-limb insufflation circuit 624. The humidifier supply conduit 104, a humidification chamber 126 and delivery conduit 606 may be said to form an inlet branch of the dual-limb insufflation circuit 624. The smoke evacuation system 610 (e.g., discharge conduit 616, discharge filter 618 and further discharge conduit 622) may be said to form an outlet branch of the dual-limb insufflation circuit 624.

[0215] Also shown in Figure 17 are a scope 626 and a laparoscopic monitor 628.

[0216] In use, insufflation gas is supplied by the gases source 102, being either or both of the wall source 612 and / or the compressed gas cylinder 614, through the insufflator supply conduit 602, to the insufflator 604. The insufflator 604 may control the pressure of the insufflation gas. The insufflator 604 supplies the insufflation gas, through the humidifier supply conduit 104, to an inlet of the surgical apparatus 106. The insufflation gas is heated and humidified by the surgical apparatus 106. The heated and humidified insufflation gas is then supplied, through the delivery conduit 606, to the patient interface 608 and then into the patient's body cavity.

[0217] In some examples, the insufflator 604 pressure may be set between about 5 mm / Hg and 20 mm / Hg, depending on the size of the patient and the amount of inflation required. The flow rate of the insufflator 604 may be set to between about 1 L / min and 12 L / min, depending on the requirements of the specific operation. In some cases, the flow rate of the insufflator 604 may be set to between about 1 L / min and 60 L / min.

[0218] The insufflation gas and surgical smoke, if any, may flow from the patient's body cavity into the patient interface 608 and through the discharge conduit 616 to the discharge filter 618. In some examples, the insufflation gas and surgical smoke, if any, may flow from the patient's body cavity into a dedicated venting cannula (not shown) and through the discharge conduit 616 to the discharge filter 618. That is, the patient interface 608 is not necessarily connected to the discharge conduit 616.

[0219] The discharge filter 618 may include a filter medium. The filter medium may trap contaminant material in the insufflation gas or the surgical smoke. The contaminant material may include one or more of particulate matter, odours, and gaseous hydrocarbons. In some examples,the filtered gas downstream from the discharge filter 618 may be almost 100% carbon dioxide. In some examples, the discharge filter removes 99.999% of all particles, cells and viruses. In some examples, the discharge filter may have retention up to 0.02 microns. The filtered gas may be vented to ambient air. It may be vented remotely from the patient and surgical team.

[0220] In some examples, the surgical apparatus 600 may be configured to humidify the insufflation gases to, or near, saturation, i.e., 100% relative humidity. As the patient's body cavity is already moist and humid, the insufflation gas may not lose much, if any, moisture in the body, and can become fully saturated if it is not already at saturation point.

[0221] In other examples, a surgical insufflation system may omit the humidifier 106, and may supply relatively dry insufflation gas to the patient, e.g., at a relative humidity of below about 90%, below about 80%, or below about 70%. The relatively dry insufflation gas may be humidified as it passes through the patient's body cavity, picking up moisture from the relatively warm and humid environment in the body cavity above the internal organs.

[0222] In some examples, the smoke evacuation system 610 does not have one or more of a heater wire and a water trap. But in some examples, one or more of the discharge conduit 616 and the further discharge conduit 622 may have a heater wire.

[0223] The smoke evacuation system 610 of the example surgical apparatus 600 may be sold individually or as part of an insufflation circuit kit. The insufflation circuit kit may include the discharge conduit 616 and one or more other components, for example:• insufflator supply conduit 602;• adapter;• insufflation gas filter;• humidifier supply conduit 104;• humidification chamber 126;• funnel;• delivery conduit 606;• patient interface 608;• diffuser;• discharge filter 618;• further discharge conduit 622.

[0224] In one example, the insufflation circuit kit may include the discharge conduit 616 and the discharge filter 618.

[0225] In another example, the insufflation circuit kit may include the adapter, insufflation gas filter, humidifier supply conduit 104, humidification chamber 126, funnel, delivery conduit 606, discharge conduit 616 and discharge filter 618.

[0226] In another example, the insufflation circuit kit may include the insufflation gas filter, humidifier supply conduit 104, humidification chamber 126, delivery conduit 606 and discharge conduit 616 and discharge filter 618.

[0227] In some examples, the insufflation circuit kit, or one or more components of the kit, may be packaged, e.g., in a sealed plastic bag. A number of insufflation circuit kits, e.g., 10 insufflation circuit kits, may be packaged together, e.g., in a cardboard box.

[0228] In some examples, the insufflation circuit kit may be partially, or wholly, preassembled. Preassembly may facilitate quicker setup of the insufflation circuit. Preassembly may reduce the risk of misconnections.

[0229] In one example, the insufflation gas filter, humidifier supply conduit 104 and humidification chamber 126 may be preassembled with each other. The delivery conduit 606 in this example is not preassembled with any other components of the insufflation circuit. The insufflation gas filter, humidifier supply conduit 104 and humidification chamber 126 may be non-sterile. The delivery conduit 606 may be sterile. The delivery conduit 606 may be packaged individually, e.g., within a sealed plastic bag. The individually packaged delivery conduit 606 may be packaged along with the insufflation gas filter, humidifier supply conduit 104 and humidification chamber 126, e.g., in another plastic bag.

[0230] Where reference is made to a humidification system it will be understood that it may be either or both of a respiratory humidification system such as the respiratory humidification system 1 or a surgical apparatus such as the surgical apparatus 600.

[0231] The humidification system may include a detector to detect one or more conditions of the humidification system. The conditions of the humidification system may be or include error conditions. The conditions of the humidification system may be or include flow conditions. The conditions of the humidification system may be detected by a controller of the humidification system.

[0232] Where the controller of a humidification system is configured to detect one or more flow conditions, the flow conditions may include incorrect flow conditions, where flow within the humidification system is not as intended for the provision of the desired therapy. Such incorrect flow conditions may be associated with error conditions of the humidification system.

[0233] The flow conditions may include one or more normal flow conditions, where the flow within the humidification system is as intended for the provision of the desired therapy.

[0234] Incorrect flow conditions may include, for example, a reverse flow condition where one or more conduits are connected backwards and / or in different locations to where they should normally be connected. Incorrect flow conditions may include, for example, a low or no flow condition where the actual flow rate is less than a desired flow rate associated with the therapy or a current portion of the therapy.

[0235] The humidification system may include a low or no flow detector, which is operable to detect when the flow within the humidification system is less than a desired flow rate associated with the therapy or a current portion of the therapy. In the no flow condition there may be no or at least substantially no flow through the inspiratory conduit.

[0236] The humidification system may include a flow direction detector, which is operable to detect a direction of gases flow within the humidification system or at least a portion thereof. More particularly, the humidification system may include a reverse flow detector, which is operable to detect a reverse flow condition where gases flow within the humidification system or at least a portion thereof is not in an intended direction.

[0237] The humidification system may include a water-out detector to detect a water-out condition of the humidification chamber of the humidification system.

[0238] A detector to detect one or more conditions of the humidification system may operate according to one or more associated detection processes, as will be described in more detail.

[0239] The operation of the controller of the humidification system as a detector to detect one or more conditions of the humidification system may allow for one or more of increased functionalities of the humidification system, improvements in patient safety, improvements in the efficacy of the humidification system in providing a desired therapy, and improvements in patient comfort.

[0240] For example, the operation of the controller to detect one or more incorrect flow conditions of the humidification system, such as a reverse flow condition and / or a no flow condition, may allow the presence of an error condition impeding the desired therapy to be identified. This may be utilised to increase the efficacy of the humidification system. Where the incorrect flow condition could result in an increased temperature of a component of the humidification system, such as a conduit in the case of a no flow condition, identification of the incorrect flow condition may allow for improvements in one or both of patient safety and comfort.

[0241] Similarly, the operation of the controller to detect a water-out condition of the humidification chamber may increase the efficacy of therapy that the humidification system can provide, by identifying and potentially alerting when the humidification chamber is no longer providing a desired humidification of the respiratory gases. The identification of the water-out condition may also provide for improvements in power consumption and safety, as power to the heater plate of the humidification chamber may be reduced or stopped on the detection of a water- out condition.

[0242] The detectors of the disclosure utilise a characteristic energisation signal that is applied to a heating element. The subsequent detection, or absence of detection, of features of the characteristic energisation signal in a signal of a temperature sensor of the humidification systemmay be used to determine one or more conditions of the humidification system. The heating element may for example be the heating element of a conduit such as the inspiratory conduit. The heating element may for example be the heating element of a humidification chamber.

[0243] The characteristic energisation signal may be applied to a heating element in the absence of any other energisation signal. In other configurations, the characteristic energisation signal may be a supplementary signal that is applied in addition to a heating element energisation signal that is concurrently applied to the heating element as part of the operation of the humidification system.

[0244] As previously described, the characteristic energisation signal for a detector, such as for example the water-out detector, no or low flow detector, or flow direction detector, may vary in frequency. An example of such a characteristic energisation signal that varies in frequency is shown in Figure 15 and is subsequently described in further detail.

[0245] By processing a signal received from a temperature sensor, and in particular but not solely frequency information from such a signal, the controller may determine whether the relevant condition of the humidification system has been detected. The determination may be based on an identification of the frequency characteristics of the characteristic energisation signal in the information received from the temperature sensor. Such detectors may be said to operate according to frequency-based detection processes.

[0246] The processing of the signal received from the temperature sensor may be such as to allow the frequency variation or variations of the characteristic energisation signal to be identified in the processed signal. The identification may require some criterion to be met, for example a degree of similarity. In other examples, such as where the processed signal output is a single value, the criterion may be a threshold of that value.

[0247] Some conventional systems may operate according to temperature-based detection processes, where the characteristic energisation signal varies in amplitude and the controller determines whether a relevant condition of the humidification system has been detected based on sensed variations in temperature of a temperature sensor. Such detectors may be said to operate according to temperature-based detection processes.

[0248] Where a detector operates by frequency-based detection, one or more advantages may be provided over temperature-based detection. First, the application of a characteristic energisation signal which varies in frequency may result in comparatively less impact on the temperature of the associated conduit and / or of the temperature of gases flowing in the conduit. Because the downstream detection is based on frequency information rather than temperature information, less variation in the energy supplied by the characteristic energisation signal may be required to perform the desired detection with a comparable degree of accuracy. In some configurations, as elsewhere herein described, the characteristic energisation signal may beconfigured so that over time a desired heating element energisation signal duty cycle may be maintained. Reducing the impact on the conduit and gases temperature may provide for increased safety and comfort. For example, reduced variation of the surface temperature of the conduit may increase its suitability for use in some applications. Reductions in the conduit and gases temperature may provide for other performance improvements such as reducing the potential for triggering temperature-based cutoffs which would otherwise impede therapy.

[0249] Secondly, the application of a characteristic energisation signal that varies in frequency may allow the detection to be performed with reduced sensitivity to external temperature changes which act on the components of the respiratory humidification system. For example, such external temperature changes may include changes in ambient temperature, changes in the temperature within an incubator where the respiratory humidification system is for providing therapy to a patient in an incubator, or changes in the humidifier heat source temperature.

[0250] Thirdly, the application of a characteristic energisation signal that varies in frequency may provide for improved patient comfort as a result of reduced disturbance to the therapy gases temperature as would be achievable using detection based on temperature fluctuations of the conduit or gases.

[0251] The low or no flow detector and the associated low or no flow detection process disclosed herein may detect when the desired gases flow through the inspiratory conduit 40 of a humidification system is not being delivered.

[0252] The reverse flow detector and the associated reverse flow detection processes disclosed herein may detect or suggest one or more types of potential incorrect connections, such as where one or more conduits are connected backwards and / or in different locations in the circuit to where they should normally be connected.

[0253] The water out detector and the associated water out detection processes disclosed herein may detect when the humidification chamber becomes empty of water or sufficiently low on water as to no longer provide the desired humidification to the respiratory gases.

[0254] A controller of the humidification system can generate an alarm or an indication that a condition of the humidification system has been detected. The alarm or indication may be presented to a user via sounds, buttons, lights, icons, and / or the user interface. The user interface may include a touchscreen or a combination of screen and buttons. The user interface may be a user interface of the humidifier, a user interface of the gases source, and / or a user interface of a patient monitoring station. The alarm may be communicated from the humidifier to the gases source and / or the patient monitoring station.

[0255] For example, a controller of the humidification system can generate an alarm or indication that an incorrect flow condition exists in the humidification system.

[0256] The controller of the humidification system may be configured to transmit a control signal to the gases source to switch off the gases source, or reduce the gases source output, or change operation of the gases source to a safe mode if an incorrect flow condition is detected. The controller of the humidification system may be configured to reduce power to the humidifier heat source or conduit heating element or control the humidifier to reduce humidity output if an incorrect flow condition is detected. The controller of the humidification system may be configured to reduce and / or limit a heating energisation signal that is applied to the heating element of the inspiratory conduit if an incorrect flow condition is detected. The controller of the humidification system may be configured to apply a delay before operating a subsequent detection for an incorrect flow condition if an incorrect flow condition is detected. After operating a detection for an incorrect flow condition, the controller of the humidification system may be configured to apply a delay before operating a subsequent detection for an incorrect flow condition if an incorrect flow condition is not detected.

[0257] In a first error condition the gases flow rate delivered through the inspiratory conduit 40 to the patient 2 is lower than a desired therapy delivery flow rate, or no flow is delivered.

[0258] The first error condition may occur if the gases source 10 is generating an insufficient level of gases flow. For example, the gases source 10 may be operating incorrectly, may be experiencing a fault, or may be off (not shown).

[0259] The first error condition may also occur if the dryline conduit 30 is disconnected from its connection at either the gases source outlet 12 of the gases source 10 or humidifier inlet 22 of the humidifier 20. Figure 4 illustrates a respiratory humidification system 1 under the first error condition where the dryline conduit 30 has not been connected to or has been disconnected from the humidifier inlet 22.

[0260] The first error condition may also occur where the dryline conduit 30, inspiratory conduit 40, and expiratory conduit 50 are all connected correctly but the breathing circuit is partially or fully obstructed (not shown). Such an obstruction may be caused by a fault of a conduit or as the result of some external action on the conduit which results in its flattening, reducing or preventing flow through it. Such an obstruction or obstructions may be located at one or more portions of the breathing circuit such that they would restrict or prevent gases flow to the patient through the inspiratory conduit 40. Where the humidification system 1 is a dual-limb system not having a vent from the patient interface, it will be appreciated that the obstruction may be an obstruction of the expiratory conduit 50.

[0261] The first error condition may result in a low or now flow condition of an inspiratory conduit of the humidification system.

[0262] In a second error condition shown in Figure 5, connections of the dryline conduit 30 and the expiratory conduit 50 with the gases source 10 are reversed. Specifically, the drylineconduit 30 is incorrectly coupled to the gases source inlet 14 and the expiratory conduit 50 is incorrectly coupled to the gases source outlet 12. As a result, the dry gases can flow directly to the patient 2 in the expiratory conduit 50 without being heated and / or humidified or heated because the dry gases do not pass through the humidifier 20 until after having been delivered to the patient. The dry gases can be heated by a heating element 51 in the expiratory conduit 50, wherein the heating is not properly regulated by the controllers which are controlling the heating element based on expecting the expiratory conduit to be receiving expired gases from the patient 2. However, expired gases from the patient 2 are instead flowing to the humidifier 20 and can thus become heated and / or humidified before being returned to the gases source 10, resulting in condensation forming in the gases source 10.

[0263] In a third error condition shown in Figure 6, there are multiple setup errors. One of the errors is that the connections at the gases source inlet 14 and gases source outlet 12 are reversed. The other error is that the inspiratory and expiratory conduits have been installed in the opposite locations. Specifically, the dryline conduit 30 is incorrectly coupled to the gases source inlet 14 and the humidifier inlet 22, the expiratory conduit 50 is incorrectly coupled to the humidifier outlet 24, and the patient 2, and the inspiratory conduit 40 is incorrectly coupled to the patient 2 and the gases source outlet 12. As a result, the dry gases can flow directly to the patient 2 in the inspiratory conduit 40 without being heated and / or humidified because the dry gases do not pass through the humidifier 20. The expired gases from the patient 2 can become heated and / or humidified in the humidifier 20 before returning to the gases source 10. The excess moisture in the gases can potentially cause damage to the gases source due to condensation.

[0264] In respiratory therapy, the heating element of the inspiratory conduit may be energised to heat the gases flow through the inspiratory conduit. The respiratory therapy may have a flow rate of gases to the patient which is associated with the provision of the therapy or a particular portion of the therapy. As previously described, where the actual flow rate to the patient is less than the desired flow rate associated with the therapy or a current portion of the therapy, a low or no flow condition may exist in the respiratory humidification system.

[0265] The energisation of the heating element of the inspiratory conduit may be based on the desired flow rate associated with the therapy. Where a low or no flow condition exists, the energisation of the heating element may cause greater than intended heating of any gases that are still flowing through the inspiratory conduit. This could result in the delivery of overheated gases to the patient.

[0266] Where a low or no flow condition exists the heat energy of the heating element may not be transferred away to the gases at the intended rate. This could cause overheating of the inspiratory conduit, potentially damaging the heating element or causing deformation of or other damage to the conduit.

[0267] In any case where a low or no flow condition exists, the gases flow delivered to the patient will not match the gases flow intended for the therapy, and the patient may therefore not benefit from the therapy.

[0268] An example of a low or no flow detection process 700 is illustrated in Figure 7. The process 700 may be operated on a respiratory humidification system 1 as described herein. For example, the respiratory humidification system may include an inspiratory conduit which is configured to deliver gases to a patient. A heating element 41 may be provided in association with the inspiratory conduit, to in use heat the conduit and the gases flowing through it. The heat source may for example be the heating element 41 that is provided as part of the inspiratory conduit as elsewhere described herein. The respiratory humidification system may also include a controller to operate the process 700. The controller may be configured to operate the heating element of the inspiratory conduit, and to receive a signal from an inspiratory temperature sensor. The inspiratory temperature sensor may be located downstream of at least a portion of the heating element. The inspiratory temperature sensor may be located downstream of the heating element. The inspiratory temperature sensor may be located at or near the patient end of the inspiratory conduit.

[0269] At process step 701 the controller begins active detection for a low or no flow condition. The process 700 involves the application of a characteristic energisation signal to the heating element. The characteristic energisation signal may be a supplementary signal, applied over any heating element energisation signal.

[0270] Step 701 could involve determining whether one or more prerequisites have been satisfied. For example, such prerequisites may be or include one or more of the heater plate temperature being below a certain threshold, the heater plate temperature being stable, that the controller has the ability to control the heater wires and / or the heater plate as required for the active detection of the low or no flow condition, that one or more particular alarms have not been triggered, that the flow rate provided by the gases source is less than a threshold, or that the heater plate has been set to a particular temperature or energisation signal to reduce undesired frequencies in the sensed temperature at either or both of the chamber outlet or patient end of the inspiratory conduit which could otherwise interfere with the detection of the characteristic energisation signal.

[0271] Under normal flow conditions associated with the delivery of the desired therapy, because the heating element is operable to heat the gases flow through the inspiratory conduit, the temperature of the gases at the patient end of the conduit may be changed over time due to the energisation of the heating element 41 . Changes in the temperature of the gases at the patient end of the inspiratory conduit may be sensed by the inspiratory temperature sensor. By processing a signal received from one or both of the chamber outlet temperature sensor and the inspiratory temperature sensor, the controller may determine whether a predetermined low or no flowcondition has been satisfied. The determination may involve determining whether the processed signal or signals satisfy a criterion.

[0272] The low or no flow condition may be a no flow condition within the respiratory humidification system. The low or no flow condition may be a no flow condition within the inspiratory conduit and / or the patient interface.

[0273] The low or no flow condition may be a threshold of flow within the respiratory humidification system. The low or no flow condition may be a threshold of flow within the inspiratory conduit and / or the patient interface. The threshold of flow may be an acceptable range of flow rates.

[0274] The controller's first process step 702 involves the application of a characteristic energisation signal, being a low or no flow detection characteristic energisation signal, to the heating element associated with the inspiratory conduit. The low or no flow detection characteristic energisation signal may be applied alone to the heating element, or may be superimposed on a heating element energisation signal that is concurrently being applied to the heating element as part of the operation of the respiratory humidification system. For example, the low or no flow detection characteristic energisation signal may be superimposed on a heating element energisation signal by summating, modulating, interleaving, cycling, or using any other scheme for sending two signals over the same transmission line.

[0275] The characteristic energisation signal, in the example of the process 700 the low or no flow detection characteristic energisation signal, may be periodic or cyclic. Where the characteristic energisation signal is periodic or cyclic, it may include a continuously varying waveform. In other examples, it may include a discontinuously varying waveform, such as one having step changes between different amplitude values. The variation of the waveform may include variations of one or more of amplitude, phase, duty cycle, shape (being any periodic shape or shapes, such as sawtooth, sinusoid, or square wave), and frequency.

[0276] In some examples the characteristic energisation signal includes one of, or one or more combinations of, a square, triangular, sinusoidal, or sawtooth wave.

[0277] For example, Figure 13 illustrates a characteristic energisation signal 131 which is in the form of a square wave of substantially constant amplitude and frequency over each of a first period 131a and second 131 b period of the characteristic energisation signal 131.

[0278] The characteristic energisation signal may vary in one or more of amplitude, phase, duty cycle, shape (being any periodic shape or shapes, such as sawtooth, sinusoid, or square wave), and frequency.

[0279] In at least some preferred configurations, the characteristic energisation signal of the detectors of the disclosure may vary in at least frequency.

[0280] Figure 14 shows a characteristic energisation signal 132 which has a constant frequency over both of a first 132a and second 132b periods, but where the amplitude increases. In other arrangements the amplitude of the signal may decrease between successive periods. Such configurations of a characteristic energisation signal 132 may be utilised in temperature-based detection processes.

[0281] Figure 15 shows another example of a characteristic energisation signal 133 where the amplitude of the characteristic energisation signal 133 remains constant, but the frequency decreases between a first period 133a and a second period 133b. In other examples the frequency of successive periods of the signal may increase.

[0282] The period of a characteristic energisation signal, for example the first period 131a and second period 131 b of the characteristic energisation signal 131 may be about 20, about 30, about 40, about 50, or about 60 seconds. In other examples the period may be less than about 20 seconds, or greater than about 60 seconds.

[0283] The duty cycle of a characteristic energisation signal may be anywhere from 0% to 100%.

[0284] In other examples, the duty cycle of a characteristic energisation signal may range across one or more periods of the characteristic energisation signal from about 60% to about 100%.

[0285] Where the characteristic energisation signal is superimposed on a heating element energisation signal that is concurrently being applied to the heating element as part of the operation of the respiratory humidification system the waveform of the characteristic energisation signal may be configured so that normal control of the heating element is not biased. For example, where the heating element energisation signal operates at a 40% duty cycle, the characteristic energisation signal may include a portion at a 0% duty cycle, and a portion at an 80% duty cycle so that over a period of time the 40% duty cycle may be maintained.

[0286] The frequency of the characteristic energisation signal can be selected to be segregated, in the frequency domain, from frequencies introduced by the humidification system and / or factors external to the temperature signals, being for example the chamber outlet temperature signal and / or the patient end temperature signal.

[0287] The frequency of the characteristic energisation signal can be selected to be segregated, in the frequency domain, from the heating element energisation signal. In one example, the frequency of the supplementary signal can be or include a higher frequency range than the heating element energisation signal otherwise associated with the delivery of the desired therapy.

[0288] The frequency of the characteristic energisation signal can be selected to be segregated, in the frequency domain, from a breathing frequency of gases flow delivered by the gases source. During a conventional ventilation therapy for an adult the gases source may forexample deliver gases at a frequency of about 6 to about 60 breaths per minute (about 0.1 Hz to about 1 Hz). During a conventional ventilation therapy for an adult the gases source may for example deliver gases at a frequency of about 30 to about 60 breaths per minute (about 0.5 Hz to about 1 Hz). During a conventional paediatric therapy the gases source may for example deliver gases at a frequency of about 15 to about 30 breaths per minute. During a high frequency ventilation the gases source may for example deliver gases at a frequency of up to about 20 Hz. In some examples, during a high frequency ventilation the gases source may for example deliver gases at a frequency of up to about 10 Hz.

[0289] Before commencing a low or no flow detection process 700 and particularly before applying the characteristic energisation signal at step 702, the heating element energisation signal may be controlled. For example, if the heating element energisation signal is configured to vary throughout a breathing cycle, the heating element energisation signal may be operated to be only a constant signal and / or to maintain the heating element at a constant temperature. The constant temperature may be a constant set point temperature or a constant sensed temperature. The constant signal may be a zero or non-zero constant signal. A delay may be operated between the controlling of the heating element energisation signal and the application of the characteristic energisation signal at step 702, to allow the effect of the heating element energisation signal on the temperature of the gases, particularly where the heating element energisation signal was varying, to no longer be present at the inspiratory temperature sensor 29. This control over the heating element energisation signal may be maintained for the duration of the detection process.

[0290] Where the characteristic energisation signal is segregated in the frequency domain from other fluctuating signals in the system which result in changes to the inspiratory gases temperature, such as the heating element energisation signal and / or the frequency of delivery of gases from the gases source, the detection of the effects of the heating element at the inspiratory temperature sensor may more easily be discriminated and the low or no flow condition more readily identified.

[0291] In some examples, the characteristic energisation signal may be segregated to a lower frequency range than the gases delivery frequency of the gases source. This configuration may allow a relatively lower degree of filtering and / or processing of the signal from the inspiratory temperature sensor to identify the effects of the characteristic energisation signal in the temperature of the gases which have propagated down the inspiratory conduit.

[0292] In other examples, the characteristic energisation signal may be segregated to a higher frequency range than the gases delivery frequency of the gases source. This configuration may require a relatively higher degree of filtering and / or processing of the signal from the inspiratory temperature sensor to identify the effects of the characteristic energisation signal in the temperature of the gases which have propagated down the inspiratory conduit.

[0293] In one example, the characteristic energisation signal may include a square wave signal which pulses on to a 100% duty cycle for about 30 seconds, then off for about 30 seconds. In such an example the characteristic energisation signal corresponds to a 60 second period, or 1 / 60Hz.

[0294] In other examples it will be appreciated that the characteristic energisation signal may include components at any duty cycle above 0% and up to 100%.

[0295] The characteristic energisation signal may be applied for only one period. In other examples, the characteristic energisation signal may be applied for two or more periods. Where gases are delivered by the gases source during the detection and their minimum frequency is about 15 breaths per minute, this example characteristic energisation signal having a frequency of 1 period per minute is segregated to a lower frequency range than the gases source frequency.

[0296] In another example where gases are delivered by the gases source during the detection and the minimum frequency of the delivered gases is about 6 breaths per minute, this example characteristic energisation signal having a frequency of 1 period per minute (1 / 60 Hz) is segregated to a lower frequency range than the gases source frequency.

[0297] In other examples the characteristic energisation signal may be segregated to higher frequencies than the maximum gases source frequency associated with the desired therapy.

[0298] Before capturing the signal at step 703 the signal from the inspiratory temperature sensor may optionally be conditioned. Such conditioning may be to filter and / or extract values from the signal. The purpose of such conditioning may be to exclude heating frequency oscillations from the humidifier heat source and / or frequency oscillations from the operation of the gases source.

[0299] Where the signal is segregated in the frequency domain from other fluctuating signals in the system, the conditioning may involve filtering out frequencies that are outside of the segregated frequency range of the characteristic energisation signal.

[0300] In addition or alternatively to frequency methods, the optional conditioning of the signal may involve the application of time domain methods such as zero-crossing detection, peak detection, and / or slope detection.

[0301] In other configurations, a filter, such a frequency filter, may additionally or alternatively be applied to the signal from the inspiratory temperature sensor before applying the low or no flow detection characteristic energisation signal to the heating element at step 702.

[0302] The characteristic energisation signal may be applied for a predetermined duration before proceeding to step 703 and capturing the inspiratory temperature sensor signal.

[0303] The duration for which the signal is applied may be selected based on the characteristics of the respiratory humidification system and in particular the breathing circuit and more particularly the inspiratory conduit of the respiratory humidification system. The duration may be based on the time required for the heating of gases at the heating element to propagate to theinspiratory temperature sensor under normal flow conditions associated with the provision of a therapy. This duration may for example be influenced by the size of the flow path of the inspiratory conduit, the flow rate delivered by the gases source, and the location of the inspiratory temperature sensor relative to the heating element.

[0304] In some examples, the duration for which the characteristic energisation signal is applied to the heating element before the controller proceeds to step 703 may be from about 10 seconds to about 2 minutes. More particularly, the duration may be from about 40 seconds to about 500 seconds. More particularly, the duration may be about 60 seconds.

[0305] While previously described as a square wave characteristic energisation signal having a period of 1 minute is applied, it may be applied for a duration of 1 minute to provide one full period of the signal. In other examples, the square wave characteristic energisation signal with a period of 1 minute may be applied for a duration of 2 minutes, or longer.

[0306] It will be appreciated that instead of delaying the capturing of the inspiratory temperature sensor signal until after the duration of the characteristic energisation signal to allow thermal propagation down the conduit, the controller may be instead configured to continuously capture the inspiratory temperature signal but to discard an initial portion during processing, the initial portion corresponding to the predetermined duration for applying the low or no flow energisation signal.

[0307] After the application of the low or no flow detection characteristic energisation signal to the heating element and any optional conditioning of the signal, the controller may proceed at step 703 to capture the signal from the inspiratory temperature sensor.

[0308] The captured signal at step 703 may include one or more periods of the low or no flow detection characteristic energisation signal.

[0309] At step 703 the controller captures the signal from the inspiratory temperature sensor. After capturing the signal, at step 704 the signal is processed to isolate the response from the low or no flow energisation signal. The processing may include the transformation of the signal to a different domain. For example, the captured signal may be transformed to the same domain as the low or no flow energisation signal. The processing may involve the extraction of magnitude and / or phase information from the captured signal. The processing may include the use of a finite impulse response (FIR) filter, cross-correlation, performing a homodyne detection or quadrature demodulation, and / or the use of a Fourier T ransform. Such a Fourier T ransformation may be a discrete Fourier T ransformation. Where a Fourier T ransform is used, it may include the use of a Goertzel algorithm or a Fast Fourier T ransformation. Autocorrelation and / or other statistical analysis may additionally or alternatively be conducted.

[0310] At step 704 the captured signal is processed to obtain a processed signal output.The controller then operates to determine if the processed signal output satisfies a criterion at step705.

[0311] The processed signal output may be a single value. In such examples, the criterion at step 705 may also be a single value and a threshold of the processed signal output. Satisfying the criterion may, depending on the configuration, involve the processed signal output being less than, less than or equal to, greater than, or greater than or equal to the criterion.

[0312] The processed signal output may be a series of values or a pattern. In such examples, the criterion at step 705 may be respectively a series of values or a pattern, and the determination of satisfaction of the criterion may include a match or degree of similarity between the processed signal output and the series of values or pattern of the criterion.

[0313] Where the controller determines that the processed signal output satisfies the criterion, the controller may determine at step 706 that a low or no flow condition has been detected in the respiratory humidification system.

[0314] When a low or no flow condition has been detected at step 706, the controller may at step 707 reduce and / or limit the heating energisation signal that may be applied to the heating element. Reducing and / or limiting the heating energisation signal amount to applying a limit to the duty cycle of the heating element. Applying such a duty cycle limit may occur only at particular flow rates. For example, the controller may at step 707 apply a duty cycle limit only where a gases flow rate in the respiratory humidification system is between about 0 L / min and about 0.3 L / min.

[0315] Application of a duty cycle limit by reducing and / or limiting the energisation signal of the heating element may function to prevent overheating of a portion of the breathing circuit, such as the inspiratory conduit, which could otherwise occur given continued heating at the level required by the therapy and the restriction or cessation of flow within the breathing circuit. For example, the energisation signal of the heating element may be limited to a 30% duty cycle, which may be sufficient to prevent overheating of certain configurations of an inspiratory conduit.

[0316] The reducing and / or limiting of the heating energisation signal may limit the duty cycle based on a gases flow rate in the respiratory humidification system. The application of the duty cycle limit may occur only within a range of gases flow rates in the respiratory humidification system. The application of the duty cycle limit may be a fixed limit on the duty cycle for a given flow rate range of gases flow in the respiratory humidification system. For example, the duty cycle limit may limit the heating energisation signal to a 30% duty cycle only when a gases flow rate in the respiratory humidification system is between about 0 L / min and about 0.3 L / min.

[0317] In other arrangements, instead of applying a duty cycle limit by reducing and / or limiting the heating energisation signal at step 707, the controller may be configured to halt the application of a heating energisation signal to the heating element.

[0318] Alternatively to a fixed duty cycle limit, the heating energisation signal may be limited by a variable duty cycle limit as a function of flow rate. In some examples, such a function may be a linear or a polynomial function. In some examples, the variable duty cycle limit may be applied in one or more therapy modes. In some examples, the variable duty cycle limit may additionally or alternatively be applied when a particular breathing circuit is detected. In some examples, the variable duty cycle limit may additionally or alternatively be applied in one or more particular therapy modes and in conjunction with the detection of a particular breathing circuit.

[0319] In some configurations, the variable duty cycle limit may be applied to the heating energisation signal of the inspiratory conduit in addition to any fixed duty cycle limit that is applied through the operation of a low or no flow detection process.

[0320] For example, the variable duty cycle limit may be applied where the respiratory humidification system is in either a high flow therapy mode or a non-invasive ventilation mode, and / or the breathing circuit is a neo-natal or paediatric circuit.

[0321] In another example, the variable duty cycle limit may be applied where the respiratory humidification system is in a non-invasive ventilation mode and the breathing circuit is a neonatal circuit for a neonatal patient.

[0322] In another example, the variable duty cycle limit may be applied where the respiratory humidification system is in an invasive ventilation mode and the breathing circuit is an adult circuit for an adult patient.

[0323] In another example, the variable duty cycle limit may be applied where the respiratory humidification system is in a non-invasive ventilation mode and the breathing circuit is a paediatric circuit for a paediatric patient.

[0324] In another example, the variable duty cycle limit may be applied where the respiratory humidification system is in a high flow therapy mode or non-invasive ventilation mode.

[0325] In one or more of the foregoing examples, the variable duty cycle limit may be applied only when a gases flow rate of the respiratory humidification system is between about 0 L / min and about 6 L / min. The flow rate may be between about 0 L / min and about 5 L / min. The flow rate may be between about 0 L / min and about 4 L / min. The flow rate may be between about 0 L / min and about 3 L / min. Within these conditions, the variable duty cycle limit may be a function of flow rate. In some examples, such a function may be a linear or polynomial function.

[0326] The controller may be configured to apply the variable duty cycle limit independently of the detection of a low or no flow condition. For example, the controller may apply the variable duty cycle limit based on gases flow rate of the respiratory humidification system is between about 0 L / min and about 6 L / min, irrespective of whether a low or no flow condition has been detected. Where the controller has applied the variable duty cycle limit and a low or no flowcondition is detected, the fixed duty cycle limit resulting from the low or no flow condition detection, such as at step 707, may be operated in combination with the variable duty cycle limit.

[0327] In some examples, where there are multiple limits applied across overlapping flow rate ranges, the lower of the limits may be applied.

[0328] After limiting or stopping heating of the heating element, the controller may return to step 701 to repeat the detection process. To prevent undesired heating of the breathing circuit due to the operation of the detection process, the controller may optionally execute a delay between step 707 and step 701 .

[0329] Where the controller at step 707 has limited the energisation signal of the heating element to a level at which overheating of the inspiratory conduit will not occur, the controller may return to step 701 without delay and continuously operate the low or no flow detection process 700.

[0330] Where the processed output signal does not satisfy the criterion, the controller may determine at step 708 that a normal flow condition, or at least the absence of a low or no flow condition, is present.

[0331] Where a low or no flow condition has not been detected, the controller may optionally apply a timer delay at step 709 before returning to step 701 and repeating the active detection process. Where the controller determines that a low or no flow condition is not present, the controller may apply or continue applying the heating energisation signal to the inspiratory conduit heating element until a subsequent detection is made of a low or no flow condition.

[0332] The detection of a low or no flow condition at step 706 may involve generating an alarm. The alarm or indication may be presented to a user via the user interface. The user interface may include a touchscreen or a combination of screen and buttons. The user interface may be a user interface of the humidifier, a user interface of the gases source, and / or a user interface of a patient monitoring station. The alarm may be communicated from the humidifier to the gases source and / or the patient monitoring station. The alarm may include, or the controller may additionally or alternatively generate, an alert to a user to check the setup and connections of a breathing circuit and / or for an obstruction of the breathing circuit.

[0333] The operation and particularly the varied operation of the humidifier heat source may act to change the temperature of gases flow through downstream portions of the respiratory humidification system, such as the inspiratory conduit. Accordingly, the controller may operate the humidifier heat source at a substantially constant energisation level while the controller operates a low or no flow detection process such as the process 700. Furthermore, to ensure that recent changes in the energisation level of the humidifier heat source do not adversely affect the detection, the controller may be configured to delay operating the detection until a predetermined time period after variation in the energisation level of the humidifier heat source has occurred.

[0334] A flow sensor configured to detect gases flow may be provided within the respiratory humidification system, and particularly at the outlet of the humidifier and / or the humidification chamber of the humidifier. In other arrangements, the flow sensor may be located in the inspiratory conduit proximate to the outlet of the humidifier. The flow sensor may be configured to pass a flow sensor signal to the controller. In such a configuration, the controller may be configured to operate the low or no flow detection process, for example the process 700, only when a sensed flow rate from the flow sensor is below a minimum acceptable reading of the flow sensor.

[0335] Another example of a low or no flow detection process 800 is illustrated in Figure 8. The steps 801 -809 mirror the steps 701 -709 of the process 700 of Figure 7, but an additional pretest step 810 is optionally applied before step 802, the application of the characteristic energisation signal to the heating element. The pre-test step 810 may include any one or more of the prerequisite satisfaction determinations described in relation to step 701 of the process 700.

[0336] The pre-test at step 810 may involve instructing the ventilator to conduct a system test. The pre-test step at 810 may additionally or alternatively involve ensuring that one or both of a chamber outlet temperature of the humidifier sensed by a chamber outlet temperature sensor and a sensed temperature of the inspiratory temperature sensor are below a threshold temperature. For example, the threshold temperature may be about 42 degrees Celsius. The pre-test at step 810 may additionally or alternatively involve ensuring that an energisation signal provided to the humidifier heat source is maintained within a predetermined range before commencing the detection. The pre-test at step 810 may additionally or alternatively involve limiting an energisation signal provided to the humidifier heat source to within a predetermined range for the duration of the detection process 800. The pre-test step 810 may additionally or alternatively involve checking that a sensed chamber outlet temperature of the humidifier by a chamber outlet temperature sensor has been maintained substantially constant for a predetermined preceding period. The pretest step 810 may additionally or alternatively involve checking that a set point of chamber outlet temperature has been maintained substantially constant for a predetermined preceding period. The pre-test step 810 may additionally or alternatively involve determining that the flow rate provided by the gases source is less than a threshold. For example, less than 3 L / min.

[0337] Where a low or no flow detection process includes a pre-test step such as the pretest step 810, the controller may not proceed to conduct the remaining steps of the process if and / or until one or each of the pre-tests are satisfied.

[0338] A humidification system disclosed herein may include a low or no flow detector by performing the low or no flow detection process. The humidifier and / or the gases source can include the low or no flow detector.

[0339] The low or no flow detector which performs the low or no flow detection process may be a detector of a low or no flow condition of an inspiratory portion of the respiratory humidification. More particularly, the detector may be a detector of a low or no flow condition of the inspiratory conduit or a patient interface of the respiratory humidification system.

[0340] A respiratory humidification system may operate one or more tests on the activation of the respiratory humidification system, and / or during the operation of the system upon some change in the system. These tests may include, for example, a breathing circuit test which may be operated by the gases source, an inspiratory and / or expiratory tube compliance check for resistance to flow, a barometric pressure test, a gas supply test, an internal leakage test, a test of a safety valve, tests of sensors connected to the controller, a test of an alarm state of the system, and a test of an alarm output connection.

[0341] These tests may be carried out if a component or connection of the breathing circuit changes. This may act to ensure that error conditions in the system do not arise without detection when the system is active but after a change in the breathing circuit.

[0342] The tests may additionally only be performed where the water level in a humidifier chamber is at or above an acceptable level. Information of the water level may be shared by a controller with the gases source.

[0343] One or more of these tests may in some configurations form part of the or the pretests of various processes disclosed herein, for example they may comprise part of step 810 of process 800 of Figure 8, or step 1002 of process 1000 of Figure 10.

[0344] In respiratory therapy, for example, in an invasive or high flow therapy mode, the patient end set point, that is, the temperature set point of the inspiratory conduit at the patient end, can be at about or higher than the normal human body temperature. For example, in the invasive therapy mode, the patient end set point can be about 40°C and the humidification chamber outlet set point can be about 37°C. In another example, in the high flow therapy mode, the patient end set point can be about 36-40°C and the humidification chamber outlet set point can be about 33-42°C. As the patient receiving the respiratory therapy can have a body temperature of about 37°C, the air exhaled by the patient can be at or slightly below 37°C. If a reverse flow condition is present, such as shown in Figure 5, the exhaled air can be received at the patient end of the inspiratory conduit, leading to the patient end temperature falling below the patient end set point. When the exhaled gases flow from the patient to the humidifier in a reverse flow condition, the inspiratory conduit heating element can be activated to heat the gases up to a first inspiratory conduit heating element duty cycle. This is because the controller is programmed to supply power to the inspiratory conduit heating element if the patient end temperature is less than the patient end set point. The controller may be configured to make the patient end temperature reach the set point even in reverse flow conditions, at least because the controller in some humidification systems may not be configuredto detect reverse flow conditions. Such heating of the inspiratory conduit could potentially result in failure of the inspiratory conduit, such as by its melting.

[0345] In such conditions it may be desirable to detect the direction of gases flow within the inspiratory conduit. A detector, operable as a flow direction detector, may be provided to detect the direction of gases flow in the respiratory humidification system or at least a portion thereof. More particularly, a reverse flow detector may be provided, the reverse flow detector operable to detect a reverse flow condition in the respiratory humidification system or at least a portion thereof.

[0346] The disclosure provides for a reverse flow detector which operates according to a frequency-based detection process rather than temperature-based detection process because of the described advantages of frequency-based detection processes over temperature-based detection processes.

[0347] A controller of the humidification system disclosed herein may include a reverse flow detector which is operable to perform the reverse flow detection process. The humidifier and / or the gases source can include the reverse flow detector.

[0348] An example of a reverse flow detection process 900 is illustrated in Figure 9. The controller begins active detection at step 901 . Before proceeding into the detection, one or more pre-test steps 910 may be operated. The pre-test step or steps 910 may be for example the same as those described in relation to the step 810 in the process 800. The pre-test step or steps 910 may be or may include one or more of the prerequisite satisfaction determinations described in relation to step 701 of the process 700. However, any pre-test step or steps at step 910 may not involve any pre-requisite threshold of flow from the gases source.

[0349] After any pre-tests, at step 902 the controller applies a characteristic energisation signal to the heating element. The characteristic energisation signal in relation to process 900 may be a reverse flow detection characteristic energisation signal.

[0350] The reverse flow detection signal may be the same as the low or no flow detection characteristic energisation signal.

[0351] The reverse flow detection characteristic energisation signal may be different from the low or no flow detection characteristic energisation signal. The reverse flow detection signal may be different from the low or no flow detection characteristic energisation signal in one or more of amplitude, phase, duty cycle, shape (being any periodic shape or shapes, such as sawtooth, sinusoid, or square wave), and frequency. In at least some preferred configurations, the characteristic energisation signal may vary in at least frequency.

[0352] After applying the reverse flow detection characteristic energisation signal, at step 903 the controller captures a chamber outlet temperature (COT) signal. The chamber outlet temperature signal may be provided by a chamber outlet temperature sensor 28. The chamberoutlet temperature sensor 28 may be associated with the humidifier and located in or near an outlet of the chamber of the humidifier. In other arrangements, the chamber outlet temperature sensor may be associated with the inspiratory conduit or a connector of an inspiratory conduit. It may be embedded in the inspiratory conduit, inspiratory conduit connector, or humidifier chamber, or it may be located in a port therein. If located in a port, it may sense the gases flow through a barrier, for example as disclosed in the PCT application PCT / NZ2013 / 000042, published as WO / 2013 / 137753 on 19 September 2013, which is incorporated herein in its entirety. In any case, the chamber outlet temperature sensor is to be located upstream, during normal gases flow, of the heating element of the inspiratory conduit.

[0353] Once captured, the chamber outlet temperature signal may be processed by the controller as illustrated at step 904. The signal is processed to generate a processed signal output. The processing may be conducted as previously described in relation to step 704 of the process 700 for low or no flow detection. The processed signal output may be a value, or a series of values or a pattern as previously described in relation to the process 700.

[0354] At step 905 the processed signal output is compared to a criterion, and the controller determines if the criterion has been satisfied. If the criterion has been satisfied, at step 906 the controller may determine that a reverse flow condition exists in the respiratory humidification system. The controller may proceed to step 908 and execute one or more corrective actions. The corrective actions may include alarms or alerts to a patient, as previously described. The corrective actions may include reducing, limiting, and / or fully stopping the application of a heating energisation signal to the heating element, for at least a predetermined period of time. The corrective actions may include an alert to a user to check the setup and / or connections of the inspiratory conduit and / or other gases conduits of the respiratory humidification system. The corrective actions may include sending a signal to a ventilator, such as notifying of the reverse flow condition and optionally instructing the generation of an alert or alarm.

[0355] The controller may operate a delay between the step 902 of injecting the reverse flow detection characteristic energisation signal and the step 903 of capturing the chamber outlet temperature signal. The delay may be determined by the properties and configuration of the respiratory humidification system, as previously described in relation to the process 700.

[0356] The controller may optionally filter the chamber outlet temperature signal from the chamber outlet temperature sensor before the step 902.

[0357] The controller may optionally apply a delay to the step 903 of capturing the chamber outlet temperature signal where the signal is filtered before step 902.

[0358] Where the criterion is not satisfied at step 905, the controller may determine at step 908 that a reverse flow condition does not exist. More particularly, the controller may determine that a forward flow condition exists.

[0359] After determining that a forward flow condition exists, the controller may optionally operate a timer delay at step 909 before returning to step 901 and restarting the detection of a reverse flow condition. The optional timer delay at step 909 may operate to limit an undesired heating of the inspiratory gases conduit by the heating element due to the application of the characteristic energisation signal.

[0360] The respiratory humidification system may optionally include a second temperature sensor that is located downstream of at least a portion of the heating element, for example an inspiratory temperature sensor as previously described. Where there is a second temperature sensor downstream of the heating element, the controller may be configured as part of a reverse flow detection process to positively detect a forward flow condition. To do so, the controller may capture, after the application of the reverse flow detection characteristic energisation signal, a signal from the second temperature sensor. The captured signal may be processed as elsewhere disclosed herein, to obtain a second processed signal output. If the second processed signal output satisfies a second criterion, the controller may determine that a forward flow condition of gases within the respiratory humidification system exists.

[0361] The detection of a forward flow condition may be executed subsequently to a determination that a reverse flow condition does not exist.

[0362] The detection of a forward flow condition may be executed simultaneously to the detection of a reverse flow condition, and the determinations compared to provide validation.

[0363] The detector may be a detector of the flow direction of gases flow within an inspiratory portion of the respiratory humidification system.

[0364] The detector may be a detector of the flow direction of gases flow within an inspiratory conduit and / or a patient interface of a respiratory humidification system.

[0365] While previously described as separate processes, the low or no flow detection process may be combined with the reverse flow detection process. Figure 10 illustrates an example process 1000 for combined low or no flow detection and reverse flow detection. Active detection in the process 1000 begins at step 1001 . One or more pre-test steps 1002 may optionally be conducted before entering the body of the process. The pre-test step or steps 1002 may reflect the pre-test step or steps 810 or 910 described in relation to the low or no flow detection process 800 and / or the reverse flow detection process 900. The pre-test step or steps 1002 may additionally or alternatively be or include one or more of the prerequisite satisfaction determinations described in relation to step 701 of the process 700.

[0366] After the satisfaction of any pre-test step or steps 1002, the controller at step 1003 applies a characteristic energisation signal to the heating element of the inspiratory conduit.

[0367] The controller is configured to receive a patient end temperature signal, for example from a patient end temperature sensor (elsewhere a second temperature sensor) that mayfor example be associated with the inspiratory conduit as described previously herein, and which is located, under normal flow conditions, downstream of the inspiratory conduit heating element. The controller is also configured to receive a chamber outlet temperature signal, for example from a first temperature sensor located, under normal flow conditions, upstream of the heating element of the inspiratory conduit.

[0368] After the application of the signal the controller may delay a predetermined time to allow propagation of heated gases through the respiratory humidification system. After any such delay, the controller captures at step 1004 the patient end temperature signal and at step 1011 the chamber outlet temperature signal. The capturing of these signals may be conducted simultaneously or one subsequently to the other.

[0369] The controller may optionally filter one or both of the patient end temperature signal and the chamber outlet temperature signal. Where one or both of the signals are filtered, the controller may apply a delay before capturing of the signals at steps 1004 and 1011 , the delay being equivalent to a time taken to filter the signal or signals. This may ensure that the output of the filter, if used, corresponds to when heating is actually applied to the heating element.

[0370] When captured, the controller processes the respective signals at steps 1005 and 1012 to obtain a respective first processed signal output and processed second signal output.

[0371] At step 1006 the controller compares the first processed signal output to a criterion. If the criterion is satisfied, at step 1007 the controller determines that a low or no flow condition has been detected. The detection of a low or no flow condition may result in the controller limiting or reducing the maximum heating element energisation signal at step 1008, or taking other corrective action as elsewhere described herein.

[0372] If the criterion is not satisfied, at step 1009 the controller determines that a low or no flow condition has not been detected, or potentially that a normal flow condition has been detected.

[0373] At step 1013 the controller compares the second processed signal output to a second criterion. If the criterion is satisfied at step 1014 the controller determines that a reverse flow condition has been detected. Corrective action may then be taken at step 1015, such as previously described in relation to step 907 of process 900. If the criterion is not satisfied at step 1016 the controller may determine that no reverse flow condition is present. Alternatively, the controller may determine that a forward flow condition is present.

[0374] The respective criterions for the steps 1006 and 1013 may be as described elsewhere herein in relation to the separate low or no flow detection process and reverse flow detection process.

[0375] After any of the steps 1008, 1009, 1015, or 1016 the controller may optionally operate a delay at step 1010 before returning to step 1001 and repeating the process 1000 for combined detection of a low or no flow condition and a reverse flow condition.

[0376] The low or no flow detection processes and / or reverse flow detection processes may be operated in association with one or more other detection processes in a respiratory humidification system. For example, they may be operated in association with a water-out or low water detection process, as is described in further detail below.

[0377] A controller or respective controllers of the humidification system disclosed herein may be configured to operate the detection regimes of one or more of a) a low or no flow detector, by performing the low or no flow detection process, b) a reverse flow detector, by performing the reverse flow detection process, and c) a water-out detector by performing the water-out detection process. The humidifier and / or the gases source can include one or each of the low or no flow detector, the reverse flow detector, and the water-out detector.

[0378] A water-out or low water condition may exist when water within the humidification chamber of the humidification system is exhausted, or at least reaches a level such that the desired humidification of the respiratory gases can no longer be provided.

[0379] Water-out and low water conditions and associated detection processes are generally described herein simply water-out conditions and water-out detection processes.

[0380] A water-out detection process may involve applying a characteristic energisation signal or supplementary signal to the heating element of a humidifier. Such a characteristic energisation signal may be a water-out characteristic energisation signal. Under normal flow conditions, the humidifier chamber including the heating element is upstream of each of the chamber outlet where a chamber outlet temperature sensor may be located, the inspiratory conduit and its heating element, and a patient end temperature sensor. Accordingly, varying the heating applied by the heating element of the humidifier may induce downstream temperature changes in the gases of the respiratory humidification system. Where reverse flow detection processes or low or no flow detection processes are to be operated in combination with a water-out detection process, it may be desirable to operate the water-out detection process after either or both of the other detection processes. Doing so may reduce the potential for noise in the captured temperature signals and increase the accuracy of making the desired respective low or no flow condition determination or reverse flow condition determination.

[0381] Figure 11 shows a process 1100 for operating different detection processes in association with each other. At step 1101 a reverse flow detection process, such as for example the process 900, is conducted. Subsequently to the reverse flow detection process 1101 , a low or no flow detection process 1102 may optionally be conducted. Lastly, at step 1103, a water-out detection process is conducted.

[0382] Figure 12 shows another process 1200 for operating different detection processes in association with each other. At step 1201 a low or no flow detection process is operated. Subsequently, at step 1202 a reverse flow detection process may optionally be conducted. Lastly, at step 1203, a water-out detection process is conducted.

[0383] The process combinations illustrated in Figure 11 and 12 both operate to avoid the aforementioned potential undesirable signal variance that could be induced by the operation of a water-out detection process before either a reverse flow detection process or low or no flow detection process.

[0384] In some configurations, the reverse flow condition may be determined after it is determined that the system is not experiencing a low / no flow condition.

[0385] When the low or no flow condition and reverse flow conditions are both determined the detector may output one or more conditions. The one or more conditions may be: normal flow, reverse flow, or low or no flow.

[0386] The controller may be configured to perform the low or no flow condition detection and reverse flow detection during therapy operation of the system.

[0387] The controller may be configured to perform the low or no flow condition detection and reverse flow conditions during startup of a system or after startup once the system has reached a steady state condition.

[0388] The controller may further be configured to disable electrical power or reduce and / or limit electrical power to a humidifier heat source in response to detection of the reverse flow condition and / or detection of the low or no flow condition.

[0389] For instance, the controller may be configured to reduce and / or limit electrical power to a humidifier heat source to at or below 20%. The controller may be configured to control power to the humidifier heat source to control the heat source to a particular temperature. In one embodiment, the electrical power to the humidifier heat source may be disabled or reduced and / or limited in response to detection of reverse flow as described above.

[0390] The electrical power to the humidifier heat source may be disabled or reduced and / or limited in response to detection of the low or no flow condition. For instance, the controller may reduce a duty cycle to a humidifier heat source to at or below 20% of a duty cycle.

[0391] The indication of low or no flow condition may comprise a low or no flow alarm.

[0392] The alarm or indication may be presented to a user via the user interface. The user interface may include a touchscreen or a combination of screen and buttons. The user interface may be a user interface of the humidifier, a user interface of the gases source, and / or a user interface of a patient monitoring station. The alarm may be communicated from the humidifier to the gases source and / or the patient monitoring station. The alarm may include, or the controllermay additionally or alternatively generate, an alert to a user to check the setup and connections of a breathing circuit and / or for an obstruction of the breathing circuit.

[0393] The alarm can be visual and / or audible.

[0394] In various configurations, a respiratory humidification system may operate one or more of the disclosed flow detection regimes. These regimes may apply to the heating element a characteristic energisation signal which changes in frequency. The type of flow condition present in the system, including the presence and type of an incorrect flow condition, may then be determined by a location within the respiratory humidification system where the processed temperature signal meets the specified criteria, indicating that the frequency characteristic of the characteristic energisation signal has been detected in the temperature signal.

[0395] Figure 16 shows a process for discrimination between different flow conditions. At block 201 the characteristic energisation signal is applied to the inspiratory conduit heating element.

[0396] A determination at block 202 that a normal flow condition exists may be made where the frequency characteristic of the characteristic energisation signal is detected in the signal of a temperature sensor associated with the patient end of the inspiratory conduit, and not also in the signal of a temperature sensor associated with the chamber outlet of the humidification chamber.

[0397] A determination at block 203 that a reverse flow condition exists may be made where the frequency characteristic of the characteristic energisation signal is detected in the signal of a temperature sensor associated with the chamber outlet of the humidification chamber.

[0398] A determination at block 204 that a low or no flow condition exists may be made where the frequency characteristic of the characteristic energisation signal is not detected in the signal of either of a temperature sensor associated with the chamber outlet of the humidification chamber or a temperature sensor associated with the patient end of the inspiratory conduit.

[0399] In a respiratory or surgical humidifier system incorporating a humidifier chamber for humidifying gases for supply to the patient or user, it is important that a certain minimum level of water is maintained for the humidifier system to have the ability to supply water vapor to the gases flow to humidify the gases. Accordingly, it is important for a healthcare professional administering the heated and / or humidified gases to a patient or user, or the patients or users themselves in the case of home-based administration, to check the water level and add more water to the humidifier chamber when needed. This task may be overlooked, which can pose danger to the patient or user due to prolonged exposure of the airway to dry gases, cause discomfort to patients or users, and / or result in a break in operation of the humidification of the gases, or, in some cases, damage to the respiratory humidifier system. Lack of water and the chamber being dry, such as due to thechamber being out of water also compromises the therapy as the amount of humidification delivered is reduced.

[0400] Low water and / or water-out detection processes are described in the PCT application with application number PCT / NZ2019 / 050095, published as WO / 2020 / 032808 on 13 February 2020, which is incorporated by reference herein in its entirety.

[0401] The water-out detection and / or alarm methods can be based on the determination of the specific heat capacity of the humidifier chamber (including its content, such as water), by application of a supplementary power input waveform (also may be referred to as a supplementary signal or a characteristic energisation signal in the disclosure herein), and the determination of the magnitude and / or phase of a humidifier heat source temperature signal and / or the temperature reading from a temperature signal on or adjacent the humidifier heat source, filtered at a predetermined frequency.

[0402] A controller or respective controllers of the humidification system disclosed herein may be configured to operate the water out detection process of a water-out detector. The humidifier and / or gases source can include the water-out detector.

[0403] Where a respiratory humidification system includes multiple of the disclosed detectors, such as two or more of a water-out detector, no or low flow detector, or flow direction detector or more particularly a reverse flow detector, discrete characteristic energisation signals may be applied in relation to the operation of each detection. For example, where a respiratory humidification system includes a low or no flow detector and a flow direction detector, the detectors may respectively operate a low or no flow detection characteristic energisation signal and a flow direction detection characteristic energisation signal. In another example, where a respiratory humidification system includes a low or no flow detector and a reverse flow detector, the detectors may respectively operate a low or no flow detection characteristic energisation signal and a reverse flow detection characteristic energisation signal.

[0404] In other configurations where a respiratory humidification system includes multiple of the disclosed detectors, such as two or more of a water-out detector, a no or low flow detector, or a flow direction detector or more particularly a reverse flow detector, a single characteristic energisation signal may be applied for the operation of each of the detectors. For example, where a respiratory humidification system includes a low or no flow detector and a flow direction detector, the same characteristic energisation signal may be associated with each of the detectors. In another example, where a respiratory humidification system includes a water-out detector, a low or no flow detector, and a flow direction detector, the same characteristic energisation signal may be associated with each of the detectors.

[0405] The characteristic energisation signal may be applied separately in relation to the operation of each of the detectors. Or, in other configurations, the same application of the characteristic energisation signal may be utilised within both or each of the detectors.

[0406] A surgical apparatus such as the surgical apparatus 600 may include one or more detectors as described herein to detect one or more conditions of the surgical apparatus. For example, a surgical apparatus 600 may include one or more of a low or no flow detector, a water- out detector, or a flow direction detector.

[0407] All the methods and tasks described herein may be performed and fully automated by a computer system. The computer system may, in some cases, include multiple distinct computers or computing devices (e.g., physical servers, workstations, storage arrays, cloud computing resources, etc.) that communicate and interoperate over a network to perform the described functions. Each such computing device typically includes a processor (or multiple processors) that executes program instructions or modules stored in a memory or other non- transitory computer-readable storage medium or device (e.g., solid state storage devices, disk drives, etc.). The various functions disclosed herein may be embodied in such program instructions, and / or may be implemented in application-specific circuitry (e.g., ASICs or FPGAs) of the computer system. Where the computer system includes multiple computing devices, these devices may, but need not, be co-located. The results of the disclosed methods and tasks may be persistently stored by transforming physical storage devices, such as solid-state memory chips and / or magnetic disks, into a different state. In some embodiments, the computer system may be a cloudbased computing system whose processing resources are shared by multiple distinct business entities or other users.

[0408] Depending on the embodiment, certain acts, events, or functions of any of the processes or algorithms described herein can be performed in a different sequence, can be added, merged, or left out altogether (e.g., not all described operations or events are necessary for the practice of the algorithm). Moreover, in certain embodiments, operations or events can be performed concurrently, e.g., through multi-threaded processing, interrupt processing, or multiple processors or processor cores or on other parallel architectures, rather than sequentially.

[0409] The various illustrative logical blocks, modules, routines, and algorithm steps described in connection with the embodiments disclosed herein can be implemented as electronic hardware (e.g., ASICs or FPGA devices), computer software that runs on general purpose computer hardware, or combinations of both. Various illustrative components, blocks, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as specialized hardware versus software running on general-purpose hardware depends upon the particular application and design constraints imposed on the overall system. The described functionality can be implemented in varying ways for each particular application, but suchimplementation decisions should not be interpreted as causing a departure from the scope of the disclosure.

[0410] Moreover, the various illustrative logical blocks and modules described in connection with the embodiments disclosed herein can be implemented or performed by a machine, such as a general purpose processor device, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor device can be a microprocessor, but in the alternative, the processor device can be a controller, microcontroller, or state machine, combinations of the same, or the like. A processor device can include electrical circuitry configured to process computer-executable instructions. In another embodiment, a processor device includes an FPGA or other programmable device that performs logic operations without processing computer-executable instructions. A processor device can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Although described herein primarily with respect to digital technology, a processor device may also include primarily analog components. For example, some or all of the rendering techniques described herein may be implemented in analog circuitry or mixed analog and digital circuitry. A computing environment can include any type of computer system, including, but not limited to, a computer system based on a microprocessor, a mainframe computer, a digital signal processor, a portable computing device, a device controller, or a computational engine within an appliance, to name a few.

[0411] The elements of a method, process, routine, or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor device, or in a combination of the two. A software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of a non-transitory computer-readable storage medium. An exemplary storage medium can be coupled to the processor device such that the processor device can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor device. The processor device and the storage medium can reside in an ASIC. The ASIC can reside in a user terminal. In the alternative, the processor device and the storage medium can reside as discrete components in a user terminal.

[0412] Where in the foregoing description reference has been made to elements or integers having known equivalents, then such equivalents are included as if they were individually set forth.

[0413] Although embodiments have been described with reference to a number of illustrative embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the preferred embodiments should be considered in a descriptive sense only and not for purposes of limitation, and also the technical scope of the invention is not limited to the embodiments. Furthermore, the present invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being comprised in the present disclosure.

[0414] Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention as herein described with reference to the accompanying drawings.

Claims

CLAIMS1 . A detector of a low or no flow condition of a respiratory humidification system, the detector comprising: an inspiratory conduit configured to deliver gases to a patient, the inspiratory conduit comprising an inspiratory conduit heating element, an inspiratory temperature sensor located downstream, under a normal flow direction, of at least a portion of the inspiratory conduit heating element, and a controller configured to be in electrical connection with the inspiratory temperature sensor and the inspiratory conduit heating element, and to detect a low or no flow condition by being configured to: apply a low or no flow characteristic energisation signal to the inspiratory conduit heating element, capture, subsequently to the application of the low or no flow characteristic energisation signal to the inspiratory conduit heating element, a signal from the inspiratory temperature sensor, process the captured signal to obtain a processed signal output, and determine whether the processed signal output satisfies a criterion, wherein the low or no flow condition is detected when the processed signal output satisfies the criterion.

2. The detector of claim 1 , wherein the detector further comprises a flow sensor configured to detect gases flow within the respiratory humidification system.

3. The detector of claim 2, wherein the flow sensor is located at an outlet of a humidifier and / or of a humidification chamber of a humidifier of the respiratory humidification system.

4. The detector of claim 3, wherein the controller is configured to be in electrical connection with the flow sensor and is configured to detect a low or no flow condition when a sensed flow rate is less than a flow threshold.

5. The detector of claim 4, wherein the flow threshold is a minimum acceptable reading of the flow sensor.

6. The detector of any one of claims 1 -5, wherein the controller captures the signal from the inspiratory temperature sensor a first predetermined time period after applying the low or no flow characteristic energisation signal to the inspiratory conduit heating element.

7. The detector of any one of claims 1 -6, wherein the controller is configured to process the captured signal and obtain the processed signal output by an application of a Fourier Transformation to the captured signal.

8. The detector of claim 7, wherein the Fourier T ransformation involves a discrete Fourier T ransformation, such as a Goertzel algorithm or a Fast Fourier T ransformation.

9. The detector of any one of claims 1 -8, wherein a chamber outlet temperature of a humidifier of the respiratory humidification system is configured to be maintained substantially constant while the controller detects a low or no flow condition.

10. The detector of claim 9, wherein maintaining the chamber outlet temperature comprises keeping the chamber outlet temperature constant for a predetermined period and / or maintaining it within a tolerance range.

11. The detector of claim 9, wherein maintaining the chamber outlet temperature comprises maintaining a constant chamber outlet temperature set point for a predetermined period and / or maintaining it within a tolerance range.

12. The detector of any one of claims 1 -11 , wherein the controller is configured to apply a heating energisation signal to the inspiratory conduit heating element, and where the heating energisation signal is applied during detecting a low or no flow condition, the low or no flow characteristic energisation signal is superimposed on the heating energisation signal.

13. The detector of claim 12, wherein upon detecting a low or no flow condition the controller is configured to reduce and / or limit the heating energisation signal applied to the inspiratory conduit heating element by applying a duty cycle limit.

14. The detector of claim 13, wherein the duty cycle limit is a fixed duty cycle limit, and the fixed duty cycle limit is applied for a given range of gases flow rates of the respiratory humidification system.

15. The detector of claim 14, wherein the fixed duty cycle limit is applied, following the detection of a low or no flow condition, when a sensed flow rate is about 0 to about 0.3 L / min.

16. The detector of claim 14 or 15, wherein the controller is further configured, independent of the detection of a low or no flow condition, to apply a variable duty cycle limit to reduce and / or limit, as a function of a gases flow rate of the respiratory humidification system, the heating energisation signal applied to the inspiratory conduit heating element.

17. The detector of claim 12, wherein upon detecting a low or no flow condition the controller is configured to halt applying the heating energisation signal to the inspiratory conduit heating element.

18. The detector of any one of claims 12-17, wherein upon detecting a low or no flow condition the controller is configured to delay further detection of a low or no flow condition for a second predetermined time period.

19. The detector of any one of claims 1 -18, wherein a normal flow condition is detected when the processed signal output does not satisfy the criterion, and the controller is configured upon detecting a normal flow condition to apply or continue the application of the heatingenergisation signal to the inspiratory conduit heating element until a subsequent detection of a low or no flow condition.

20. The detector of any one of claims 1 -19, wherein upon detecting a low or no flow condition the controller is configured to one or more of: a) generate an alarm, b) generate an alert to a user to check for obstruction of a gases flow path of one or more of the inspiratory conduit, other gases conduits, and a patient interface of the respiratory humidification system, and c) send a or the alert to a ventilator of the respiratory humidification system.21 . The detector of any one of claims 1 -20, wherein the inspiratory temperature sensor is located downstream of the inspiratory conduit heating element.

22. The detector of any one of claims 1 -21 , wherein the inspiratory conduit comprises the inspiratory temperature sensor , and the inspiratory temperature sensor is located at or near a patient end of the inspiratory conduit.

23. The detector of any one of claims 1 -22, wherein the low or no flow characteristic energisation signal comprises at least one period of a varying energisation signal.

24. The detector of any one of claims 1 -23, wherein the low or no flow characteristic energisation signal is defined by a frequency and / or period.

25. The detector of any one of claims 1 -24, wherein the low or no flow characteristic energisation signal is distinct from a or the heating energisation signal.

26. The detector of any one of claims 1 -25, wherein the captured signal comprises at least one period of the low or no flow characteristic energisation signal.

27. The detector of any one of claims 1 -26, wherein the controller is configured to perform one or more of the following preliminary steps before detecting a low or no flow condition: a) instructing a ventilator of the respiratory humidification system to conduct a test, b) ensuring that a chamber outlet temperature of a humidifier sensed by a chamber outlet temperature sensor and a sensed temperature of the inspiratory temperature sensor are below a threshold temperature, c) ensuring that an energisation signal provided to a humidifier heat source of the respiratory humidification system has i) been maintained within a predetermined range for a predetermined preceding period and / or ii) will be maintained substantially constant for a subsequent period corresponding to a time required to operate the detection of a low or no flow condition, and / or iii) has maintained the humidifier heat source to an at least substantially constant temperature for a predetermined preceding period, d) controlling the humidifier heat source to a constant temperature, e) controlling the energisation signal provided to the humidifier heat source to provide a constant power delivery to the humidifier heat source, andf) checking that a chamber outlet temperature of a humidifier sensed by a chamber outlet temperature sensor has been substantially constant for a predetermined preceding period.

28. The detector of any one of claims 1 -26, wherein the controller is configured to check that a humidifier heat source set point has been substantially constant for a predetermined preceding period.

29. The detector of any one of claims 1 -26, wherein the controller is configured to check that a chamber outlet temperature set point of a humidifier has been substantially constant fora predetermined preceding period.

30. The detector of claim 27, wherein the step of ensuring the chamber outlet temperature and the sensed temperature of the inspiratory temperature sensor are below a threshold temperature comprises comparing both of the chamber outlet temperature and sensed temperature of the inspiratory temperature sensor to the threshold temperature.31 . The detector of claim 27 or 30, wherein the step of ensuring the chamber outlet temperature and the sensed temperature of the inspiratory temperature sensor are below a threshold temperature comprises respectively controlling the energisation signal provided to the humidifier heat source and the heating energisation signal applied to the inspiratory conduit heating element until the chamber outlet temperature and sensed temperature of the inspiratory temperature sensor are below the threshold temperature.

32. The detector of any one of claims 27, 30, or 31 , wherein if one or more of the preliminary steps are not satisfied, the controller does not conduct the detection of a low or no flow condition.

33. The detector of any one of claims 1 -32, wherein the controller is further configured to filter out frequencies within one or more predetermined ranges from the signal from the inspiratory temperature sensor before capturing the signal from the inspiratory temperature sensor.

34. The detector of claim 33, wherein the controller is configured conduct the filtering before applying the low or no flow characteristic energisation signal to the inspiratory conduit heating element.

35. The detector of any one of claims 1 -34, wherein the controller is configured to apply a delay between applying the low or no flow characteristic energisation signal to the inspiratory conduit heating element and capturing the signal from the inspiratory temperature sensor.

36. The detector of any one of claims 1 -35, wherein the processed signal output is a value.

37. The detector of any one of claims 1 -36, wherein the criterion is a threshold of the processed signal output.

38. The detector of any one of claims 1 -37, wherein the processed signal output is a series of values.

39. The detector of any one of claims 1 -38, wherein the criterion is a series of thresholds of the processed signal output.

40. The detector of claim 38 or 39, wherein the criterion is a pattern.41 . The detector of any one of claims 1 -40, wherein the detector is a detector of a low or no flow condition of an inspiratory portion of a respiratory humidification system.

42. The detector of any one of claims 1 -41 , wherein the detector is a detector of a low or no flow condition of the inspiratory conduit or a patient interface of a respiratory humidification system.

43. A method of detecting a low or no flow condition of a respiratory humidification system and detecting a low water or water-out condition in a humidifier of the respiratory humidification system, the method comprising the steps of: detecting using a controller a low or no flow condition of the respiratory humidification system by: applying a low or no flow characteristic energisation signal to an inspiratory conduit heating element, capturing a signal from an inspiratory temperature sensor located downstream of at least a portion of the inspiratory conduit heating element, processing the captured signal to obtain a processed signal output, and determining, when the processed signal output satisfies a criterion, the existence of a low or no flow condition of the inspiratory conduit, and detecting a low water or water-out condition in the humidifier, wherein the step of detecting a low or no flow condition is executed before the step of detecting a low water or water-out condition in the humidifier.

44. The method of claim 44, wherein the method further comprises the step of detecting a flow direction of gases flow within the inspiratory conduit and / or patient interface by: applying a low or no flow characteristic energisation signal to the inspiratory conduit heating element, capturing, subsequently to the application of the low or no flow characteristic energisation signal to the inspiratory conduit heating element, a signal from the inspiratory temperature sensor, processing the captured signal to obtain a processed signal output, anddetecting a reverse flow direction of gases within the inspiratory conduit when the processed signal output satisfies a criterion, wherein the detection of the flow direction of gases flow within the inspiratory conduit and / or patient interface is conducted before the detection of a low water or water-out condition but after the detection of a low or no flow condition of the inspiratory conduit.

45. A detector of a flow direction of gases flow within a respiratory humidification system, the detector comprising: an inspiratory conduit configured to deliver gases to a patient, the inspiratory conduit comprising an inspiratory conduit heating element, a first temperature sensor located upstream of the inspiratory conduit heating element, and a controller configured to be in electrical connection with the first temperature sensor and the heating element, and to detect a flow direction of gases flow within the inspiratory conduit by being configured to: apply a reverse flow characteristic energisation signal to the inspiratory conduit heating element, capture, subsequently to the application of the reverse flow characteristic energisation signal to the inspiratory conduit heating element, a signal from the first temperature sensor, process the captured signal to obtain a processed signal output, and detect a reverse flow direction of gases within the respiratory humidification system when the processed signal output satisfies a criterion.

46. The detector of claim 45, wherein the controller is configured to detect the existence of a forward flow direction of gases within respiratory humidification system when the processed signal output does not satisfy the criterion.

47. The detector of claim 45 or 46, wherein the controller captures the signal from the first temperature sensor a first predetermined time period after applying the reverse flow characteristic energisation signal to the inspiratory conduit heating element.

48. The detector of any one of claims 45-47, wherein the controller is configured to process the captured signal and obtain the processed signal output by the application of a Fourier Transformation to the captured signal.

49. The detector of claim 48, wherein the Fourier T ransformation involves an application of a discrete Fourier T ransformation, such as Goertzel algorithm or a Fast Fourier Transformation.

50. The detector of any one of claims 45-49, wherein upon detecting a reverse flow direction the controller is configured to reduce and / or limit the heating energisation signal applied to the inspiratory conduit heating element by applying a duty cycle limit.

51. The detector of claim 50, wherein the duty cycle limit is a fixed duty cycle limit, and the fixed duty cycle limit is applied for a given range of gases flow rates of the respiratory humidification system.

52. The detector of claim 51 , wherein the fixed duty cycle limit is applied, following the detection of a low or no flow condition, when a sensed flow rate is about 0 to about 0.3 L / min.

53. The detector of claim 51 or 52, wherein the controller is further configured, independent of the detection of a reverse flow condition, to apply a variable duty cycle limit to reduce and / or limit, as a function of a gases flow rate of the respiratory humidification system, the heating energisation signal applied to the inspiratory conduit heating element.

54. The detector of any one of claims 45-53, wherein upon detecting a reverse flow direction the controller is configured to stop applying the heating energisation signal to the inspiratory conduit heating element.

55. The detector of any one of claims 45-54, wherein upon detecting a reverse flow condition the controller is configured to one or more of: a) generate an alarm, b) generate an alert to a user to check the connection of the inspiratory conduit and / or other gases conduits of the respiratory humidification system, and c) send a signal to a ventilator of the respiratory humidification system.

56. The detector of any one of claims 45 to 55, wherein the detector further comprises a second temperature sensor located downstream of at least a portion of the inspiratory conduit heating element, and the controller is configured to: capture, subsequently to the application of the reverse flow characteristic energisation signal to the inspiratory conduit heating element, a signal from the second temperature sensor, process the captured signal from the second temperature sensor to obtain a second processed signal output, and detect a forward flow condition of gases within respiratory humidification system when the second processed signal output satisfies a second criterion.

57. A method of detecting a flow direction of gases flow within a respiratory humidification system and detecting a low or no flow condition of a respiratory humidification system, the method comprising the steps of: detecting a flow direction of gases flow within an inspiratory conduit of a respiratory humidification system, and detecting a low or no flow condition of the respiratory humidification system by: applying by a controller a characteristic energisation signal to an inspiratory conduit heating element,capturing by the controller a signal from a second temperature sensor located downstream of at least a portion of the inspiratory conduit heating element, processing the captured signal to obtain a processed signal output, and determining, when the processed signal output satisfies a criterion, the existence of a low or no flow condition of the respiratory humidification system, and wherein the step of detecting a flow direction of gases flow within the respiratory humidification system is executed before the step of detecting a low or no flow condition of the respiratory humidification system.

58. The method of claim 57, wherein the method further comprises the step of detecting a low water or water-out condition in a humidifier, wherein the detection of a low water or water-out condition in the humidifier is conducted after the step of detecting a low or no flow condition of the respiratory humidification system.

59. A method of operating a respiratory humidification system, the method comprising: as preliminary step, detecting using a controller at least one of: a) a low or no flow condition of the respiratory humidification system, and b) a flow direction of gases flow within the respiratory humidification system, and as a subsequent step, detecting a low water or water-out condition in a humidifier of the respiratory humidification system, wherein during the preliminary step the controller operates a humidifier heat source heating element to maintain a humidifier chamber outlet temperature within an acceptable range, and wherein the subsequent step of detecting a low water or water-out condition comprises energising the humidifier heat source heating element.

60. The method of claim 59, wherein the subsequent step of detecting a low water or water-out condition comprises energising the humidifier heat source heating element such that the humidifier chamber outlet temperature exceeds the acceptable range.61 . The method of claim 59 or 60, wherein the preliminary step comprises both detecting using a controller a low or no flow condition of the respiratory humidification system and detecting using the controller a flow direction of gases flow within the respiratory humidification system.

62. The method of any one of claims 59-61 , wherein the detecting of a low or no flow condition and the detecting of a flow direction of gases flow are performed concurrently by the controller.

63. The method of any one of claims 59-62, wherein the detecting of a low or no flow condition and the detecting of a flow direction of gases flow are performed sequentially by the controller.

64. A detector of a flow condition of gases flow within a respiratory humidification system, the system comprising: a heating element, a temperature sensor, and a controller configured to be in electrical connection with the temperature sensor and the heating element, and to detect a flow condition of gases flow within the respiratory humidification system by being configured to: apply a characteristic energisation signal to the heating element, capture, subsequently to the application of the characteristic energisation signal to the heating element, a signal from the temperature sensor, process the captured signal to obtain a processed signal output, and detect the flow condition of gases flow within the respiratory humidification system when the processed signal output satisfies a criterion.

65. The detector of claim 66, wherein: the system further comprises an inspiratory conduit configured to deliver gases to a patient, the heating element comprises an inspiratory conduit heating element, the application of the characteristic energisation signal is to the inspiratory conduit heating element, the temperature sensor comprises a first temperature sensor located upstream of the inspiratory conduit heating element, the temperature signal comprises a first captured temperature signal captured from the first temperature sensor, the processing comprises processing the first temperature signal, the processed signal output of the first temperature signal comprises a first processed signal output, the flow condition comprises a direction of gases flow, and the detected direction of gases flow is a detected direction of gases flow within the inspiratory conduit.

66. The detector of claim 64 or 65, wherein: the system further comprises an inspiratory conduit configured to deliver gases to a patient, the heating element comprises a heating element of a humidifier heat source, the characteristic energisation signal is applied to the heating element of the humidifier heat source, the temperature sensor comprises a second temperature sensor located downstream of at least a portion of the heating element of the humidifier heat source,the temperature signal comprises a second temperature signal captured from the second temperature sensor, the processing comprises processing the second temperature signal, the processed signal output of the second temperature sensor comprises a second processed signal output, the flow condition is a low or no flow condition, and the detection of a low or no flow condition is a detection of whether gases are flowing in the inspiratory conduit.

67. A detector of a low or no flow condition of a respiratory humidification system, the detector comprising: a controller configured to be in electrical connection with a) an inspiratory temperature sensor in a downstream portion of an inspiratory conduit and b) a heating element of the inspiratory conduit, and to detect a low or no flow condition of the inspiratory conduit by being configured to: apply a characteristic energisation signal to the inspiratory conduit heating element, capture, subsequently to the application of the low or no flow characteristic energisation signal to the inspiratory conduit heating element, a signal from the inspiratory temperature sensor, process the captured signal to obtain a processed signal output, and determine whether the processed signal output satisfies a criterion, wherein the low or no flow condition is detected when the processed signal output satisfies the criterion.

68. The detector of claim 67, wherein the controller is further configured to be in electrical connection with a flow sensor located at an outlet of a humidifier and / or of a humidification chamber of a humidifier of the respiratory humidification system, wherein the controller is configured to detect a low or no flow condition when a sensed flow rate is less than a flow threshold.

69. The detector of claim 67 or 68, wherein a chamber outlet temperature of a humidifier of the respiratory humidification system is configured to be maintained substantially constant while the controller detects a low or no flow condition, and wherein maintaining the chamber outlet temperature comprises keeping the chamber outlet temperature constant for a predetermined period and / or maintaining it within a tolerance range.

70. The detector of claim 68 or 69, wherein the controller is configured to maintain a constant chamber outlet temperature set point and / or to maintain the chamber outlet temperature set point within a tolerance range while the controller detects a low or no flow condition.71 . The detector of any one of claims 67-70, wherein the controller is configured to apply a heating energisation signal to the inspiratory conduit heating element, and where theheating energisation signal is applied during detecting a low or no flow condition, the low or no flow characteristic energisation signal is superimposed on the heating energisation signal.

72. The detector of any one of claims 67-71, wherein upon detecting a low or no flow condition the controller is configured to reduce and / or limit the heating energisation signal applied to the inspiratory conduit heating element by applying a duty cycle limit.

73. The detector of claim 72, wherein the duty cycle limit is a fixed duty cycle limit, and the fixed duty cycle limit is applied for a given range of gases flow rates of the respiratory humidification system.

74. The detector of claim 73, wherein the fixed duty cycle limit is applied, following the detection of a low or no flow condition, when a sensed flow rate is about 0 to about 0.3 L / min.

75. The detector of any one of claims 72-74, wherein the controller is further configured, independent of the detection of a low or no flow condition, to apply a variable duty cycle limit to reduce and / or limit, as a function of a gases flow rate of the respiratory humidification system, the heating energisation signal applied to the inspiratory conduit heating element.

76. A detector of a flow direction of gases flow within a respiratory humidification system having an inspiratory conduit configured to deliver gases to a patient, the inspiratory conduit comprising an inspiratory conduit heating element, the detector comprising: a first temperature sensor located upstream of the inspiratory conduit heating element, and a controller configured to be in electrical connection with the first temperature sensor and the heating element, and to detect a flow direction of gases flow within the inspiratory conduit by being configured to: apply a characteristic energisation signal to the inspiratory conduit heating element, capture, subsequently to the application of the characteristic energisation signal to the inspiratory conduit heating element, a signal from the first temperature sensor, process the captured signal to obtain a processed signal output, and detect a reverse flow direction of gases within the respiratory humidification system when the processed signal output satisfies a criterion.

77. The detector of claim 76, wherein the detector is configured to detect the existence of a forward flow direction of gases within respiratory humidification system when the processed signal output does not satisfy the criterion.

78. The detector of claim 76 or 79, wherein the detector further comprises a second temperature sensor located downstream of at least a portion of the inspiratory conduit heating element, and the controller is configured to: capture, subsequently to the application of the characteristic energisation signal to the inspiratory conduit heating element, a signal from the second temperature sensor,process the captured signal from the second temperature sensor to obtain a second processed signal output, and detect a forward flow direction of gases within respiratory humidification system when the second processed signal output satisfies a second criterion.

79. The detector of any one of claims 76-78, wherein upon detecting a reverse flow direction the controller is configured to limit the heating energisation signal applied to the inspiratory conduit heating element.

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