Detection of disconnection of the patient circuit of a medical ventilator

Abstract

Title of the invention: Detection of patient circuit disconnection of a medical ventilator. The invention relates to a medical ventilator (10) comprising compliance selection means configured to allow a user to choose a given compliance threshold value based on a patient category to be treated, namely adult, child, and infant, and a ventilation mode to be implemented, namely barometric and volumetric ventilation modes. Abstract figure: Fig. 1

Description

Title of the invention: Detection of disconnection of the patient circuit of a medical ventilator

[0001] The invention relates to a detection of the disconnection of the patient circuit of a medical ventilator supplying a patient with respiratory gas.

[0002] A medical ventilator is a respiratory support device used to deliver respiratory assistance, that is, artificial ventilation, to a patient suffering from respiratory disorders or insufficiency of varying severity, which may result from different pathologies or similar conditions. Some patients with severe pathologies may remain ventilated in a hospital setting for several days, or even several months.

[0003] During its operation, the medical ventilator delivers a respiratory gas to the patient, for example air or oxygen-enriched air, via a patient circuit comprising one or more conduits for conveying the gas, and also operates a monitoring of ventilatory parameters such as gas pressure, patient esophageal pressure, gas volumes exchanged, gas flow rate... and can trigger an audible or visual alarm to alert healthcare personnel in the event of ventilator malfunction or a problem related to patient ventilation, in particular in the event of accidental disconnection of the patient circuit.

[0004] Indeed, during the use of the ventilator, an accidental disconnection or unplugging of the patient circuit may occur, for example at the connection between the ventilator and the patient circuit, between the patient circuit and the patient breathing interface supplying the patient with breathing gas, typically a nasal, oral or face (i.e. oronasal) breathing mask or a tracheal intubation tube, or even in the inspiratory and / or expiratory branches and the Y-junction piece of a double-branch patient circuit, as illustrated on [Fig.1] and detailed below.

[0005] To this end, the ventilator generally includes circuit disconnection detection means and alarm means for detecting any disconnection of the patient circuit and then for alerting the nursing staff or the patient by triggering a dedicated audible and / or visual alarm so that they can take appropriate action, namely reconnecting the disconnected elements.

[0006] However, in practice, false alarms sometimes occur, meaning that the fan mistakenly detects a disconnection when all the elements are correctly connected.

[0007] Furthermore, patient compliance is the ability of their lungs to expand with each inspiration. When the circuit is disconnected, the measured compliance is no longer representative of the patient's compliance and increases indefinitely. One method for detecting disconnection is to compare the compliance measured by the ventilator to a given threshold. As soon as this exceeds the threshold, the ventilator considers a disconnection and triggers an alarm to alert the healthcare staff.

[0008] However, the resistance generated by the respiratory interface, particularly by a tracheal tube, limits flow rates in the event of disconnection, especially for smaller / younger patients, such as children, and consequently limits the measured compliance, given that these patients generally have low compliance. This leads to undetected disconnections in some cases.

[0009] The problem is therefore to enable improved, i.e. more effective, detection of untimely circuit disconnections while minimizing false detections in order to reduce or eliminate the number of false alarm triggers, including in the smallest / youngest patients with low compliances.

[0010] The solution of the invention then relates to a medical ventilator, that is to say a respiratory assistance device, comprising: - an internal gas circuit for conveying gas, including a gas outlet, - at least one flow sensor and at least one pressure sensor arranged on the internal gas circuit to perform flow and pressure measurements within said internal gas circuit, - microprocessor-based control systems configured to process flow and pressure measurements taken by said flow and pressure sensors, - a patient circuit fluidly connected to the gas outlet of the internal gas circuit, and - a respiratory interface fluidically connected to the patient circuit,

[0011] and in which the control means are configured to: a. Determine patient compliance based on pressure and flow measurements. b. compare the patient's compliance, as determined, to a given compliance threshold, and c. trigger an alarm when a disconnection of the patient circuit or the breathing interface is determined during the comparison performed in step b).

[0012] Furthermore, the fan further includes compliance selection means configured to allow a user to choose a compliance threshold value data based on a category of patient to be treated and a mode of ventilation to be implemented.

[0013] Depending on the embodiment considered, the medical ventilator of the invention may comprise one or more of the following features: - The compliance selection methods are configured to allow selection of a patient category chosen from adult, child and infant. - The compliance selection means are configured to allow selection of a ventilation mode chosen from among the barometric and volumetric ventilation modes. - the patient circuit is a dual-branch circuit. - the means of compliance selection include a manual selection device and / or a display screen, typically an HMI. - the patient circuit includes two gas lines arranged in parallel, i.e. an inspiratory branch and an expiratory branch, like flexible hoses. - the patient circuit is connected to a respiratory interface via a junction or connecting piece, typically a Y-piece. - the gas source is a motorized micro-blower, i.e. comprising an electric motor, also called a blower, turbine or compressor. - the motorized micro-blower is configured to deliver a breathing gas of the air type or oxygen-enriched air (i.e. air / O2 mixture). - the control means are configured to control the motorized micro-blower, in particular the acceleration and braking / deceleration phases of said motor. - the control means include one or more microprocessors, typically a microcontroller, implementing at least one algorithm. - it also includes means of power supplying electrical current to the component(s) requiring electricity to operate, in particular control means, i.e. means of connection to the mains (110 / 220V), such as electrical cable(s) and / or mains socket. - it also includes a rigid outer casing or shell, for example made of polymer or metal. - it also includes means of memorization, for example computer memory or similar, for memorizing, i.e. storing, data, values, information or other things. - the respiratory interface is a mask, a tracheal tube or similar.

[0014] The invention will now be better understood with reference to the following detailed description, given by way of illustration but not limitation, with reference to:

[0015] [Fig-1] schematically shows the disconnection sites of a double-branch patient circuit connected to a medical ventilator.

[0016] [Fig. 1] schematically illustrates the locations of various possible branch connections 1-6 of a double-branch patient circuit 11, e.g., a flexible conduit or similar device, fluidly connecting a medical ventilator 10, i.e., a respiratory support device, to a respiratory interface 12, such as a breathing mask or a tracheal tube. The patient circuit 11 allows the respiratory gas, such as air or an air / O2 mixture, delivered by the medical ventilator 10 to be conveyed to patient P and then administered by inhalation to patient P during their inspiratory phases.

[0017] The patient circuit 11 is here double-branch, that is to say it comprises two flexible conduits arranged in parallel or similarly, fluidly connecting the medical ventilator 10 to the respiratory interface 12, such as a respiratory mask, a tracheal tube or other, via a Y-shaped junction piece 13, generally called a "Y-piece".

[0018] The inspiratory branch of the patient circuit 11 carries the gas from the ventilator 10 to be administered to patient P, while the expiratory branch carries to the ventilator 10 the gases exhaled by the patient which are enriched in CO2.

[0019] The various possible disconnection sites (1 to 5) of the patient circuit 2 are shown in [Fig.1], namely at the connections between ventilator 10 and the upstream ends of the inspiratory and expiratory branches of the patient circuit 11 (sites 1 and 2), and / or the connections between the downstream ends of the inspiratory and expiratory branches of the circuit 11 and the Y-piece 13 (sites 3 and 4), and / or at the connection between the Y-piece 13 itself and the respiratory interface 12.

[0020] Of course, the respiratory interface 12 can also be removed itself from the patient's face (site 6).

[0021] It is essential to be able to detect such disconnections of the patient circuit 11, in particular those of sites 1 to 5. To do this, the medical ventilator 10 is equipped with alarm means including an alarm for monitoring the disconnection status of circuit 11. When this detects a disconnection of circuit 11, it rises and alerts the patient and / or medical staff.

[0022] Conventionally, the medical ventilator 10 comprises an outer casing or shell in which a gas source is arranged, such as a motorized micro-blower, i.e., equipped with an electric motor driving a vane, delivering here an airflow (oxygen content 21% by volume) in a gas path, i.e., an internal gas circuit, in fluidic communication with the air outlet of the micro-blower. The internal gas circuit comprises one or more gas ducts or passages, or the like, configured to convey the gas within the ventilator 10 to a gas outlet, also called the ventilator outlet, to which the inspiratory branch of the patient circuit 11 is connected. According to another embodiment (not shown), the gas source can be an external source of the ventilator 1, such as a compressed air supply, for example a flexible conduit connected to a wall-mounted gas distribution outlet or to a pressurized gas container, such as a pressurized gas cylinder.

[0023] Patient circuit 11 can be single branch (not shown) or double branch, like that of [Fig. 1].

[0024] Flow and pressure sensors are usually arranged on the internal gas circuit, downstream of the micro-blower, to perform pressure and flow measurements of the gas flowing through it.

[0025] Control means, i.e. a processing and control unit, typically comprising an electronic board including a (or more) microprocessor, such as a microcontroller, implementing at least one algorithm, receives and processes the measurements (i.e. signals) operated by the pressure and flow sensors.

[0026] The control means control the gas supply, i.e. here the motorized micro-blower delivering the airflow so as to deliver a flow rate and / or a pressure of gas according to the modalities of the ventilation mode selected by the physician, for example by means of adjustment buttons and / or a touch screen of an HMI or human-machine interface of the ventilator 10.

[0027] The control means also process the pressure and flow measurements operated by the flow and pressure sensors in order to determine patient compliance, as explained below.

[0028] An oxygen source, such as an oxygen cylinder or an oxygen line, can be fluidically connected to the gas circuit of the fan 10, via one or more gas lines, so as to introduce oxygen into the airflow circulating in the gas circuit of the fan 10.

[0029] As already mentioned, the fan 10 also includes an HMI comprising, for example, touch-sensitive buttons, rotary or translational buttons, or similar devices, allowing the user to enter information or instructions into the fan 10, or to make choices, confirmations, or selections in menus, for example. The HMI's digital touchscreen not only displays various information, data, pictograms, graphics, etc., but also allows data entry for use, particularly by the control means, or enables choices, selections, and confirmations of parameters, operating modes, or other functions.

[0030] Of course, the fan 10 may further include means for supplying electric current (not shown) such as a cord and plug for connection to the mains (110 / 220V), a current transformer and / or an internal battery, supplying the components requiring electric current to operate, in particular the micro-blower, in particular its electric motor, the control means, the sensors, the HMI screen or any other component.

[0031] Furthermore, the control means 12, in particular their processor, are configured to detect any disconnection of the patient circuit 11 (e.g. sites 1 to 5), by comparing the patient's compliance to a given threshold compliance value.

[0032] As already explained, patient compliance is the ability of his lungs to expand with each inspiration

[0033] According to the invention, the ventilator 10 further includes compliance selection means configured to allow a user, e.g. a doctor, to choose a given compliance threshold value according to a category of patient to be treated, i.e. adult, child or infant, and a ventilation mode to be implemented, i.e. barometric or volumetric.

[0034] The compliance threshold used to detect a circuit disconnection 11 can therefore be adapted according to the patient category selected by the practitioner on the ventilator 10, i.e., the ventilator. For example, for an adult patient, the threshold can be set at 300 mL / cmH2O, for a child, at 200 mL / cmH2O, and for an infant, at 100 mL / cmH2O, or other suitable values.

[0035] Since thresholds based solely on a patient category may not be reliable enough to effectively detect ventilated patients using different ventilation modes and settings, the invention also takes into account the ventilation mode to be implemented, namely a pressure-controlled mode, also called a barometric mode, or a volume-controlled mode, also called a volumetric mode. This is necessary to avoid false alarms.

[0036] Indeed, patient compliance (Cpatient) is generally calculated using the The following formula is used within the control system, i.e., the microprocessor:

[0037] Cpatient = ___________________Vti___________________ Pprox (Start InspiyPprox (End Inspi))

[0038] where:

[0039] - Vti is the volume delivered to the patient by the machine during the inspiratory phase, and

[0040] - Pprox is the pressure at the patient's mouth, measured at the beginning and end of the phase inspirational.

[0041] The Vti and the Pprox are themselves calculated from the flow and pressure measurements taken by sensors in the machine.

[0042] In volumetric ventilation mode, the machine delivers a constant volume, i.e., the Vti is the same whether the patient is disconnected or not. No attempt is made to compensate for leaks or disconnections. Therefore, the pressure drops sharply when the patient is disconnected. Consequently, the measured compliance increases very significantly.

[0043] In barometric ventilation mode, the machine aims to deliver a constant pressure. It will therefore do everything possible to reach this pressure, even if it means delivering a larger volume. Consequently, there is no drastic drop in pressure as in volumetric mode, and the measured compliance increases less significantly.

[0044] It is therefore advantageous to segregate the compliance thresholds representative of a disconnection according to the type of mode, barometric or volumetric.

[0045] Finally, optimizing the detection thresholds for barometric modes involves using different thresholds depending on the inspiratory pressure set by the practitioner on the ventilator. This inspiratory pressure is what the machine tries to reach and maintain at the end of inspiration. In a disconnected state, the higher the pressure, the more it tends to decrease the measured compliance (the increase in PProx(Finlnspi) is greater than that of Vti). It may therefore be necessary to adjust the disconnection detection threshold to the set Inspiratory Pressure.

[0046] In summary, according to the invention, the compliance disconnection detection algorithm implemented by the control means allows for more effective detection of any circuit disconnection if the thresholds are adapted to the patient type (category), the ventilation mode and, for barometric modes, to the set inspiratory pressure.

[0047] In general, a medical ventilator according to the invention makes it possible to deliver respiratory assistance, that is to say artificial ventilation, to a patient suffering from more or less severe respiratory disorders or insufficiencies, which may result from various pathologies or similar conditions, in particular to a patient ventilated in a hospital setting, for several days, even several weeks or several months.

Claims

Demands

1. A medical ventilator (10) comprising: - an internal gas circuit for delivering gas including a gas outlet, - at least one flow sensor and at least one pressure sensor arranged on the internal gas circuit for performing flow and pressure measurements within said internal gas circuit, - microprocessor-controlled control means configured to process the flow and pressure measurements performed by said flow and pressure sensors, - a patient circuit (11) fluidly connected to the gas outlet of the internal gas circuit, and - a breathing interface (12) fluidly connected to the patient circuit (11), and in which the control means are configured to: a) determine patient compliance from pressure and flow measurements, b) compare the patient compliance determined to a given compliance threshold,and c) trigger an alarm when a disconnection of the patient circuit (11) or the breathing interface (12) is determined during the comparison performed in step b), characterized in that it further comprises compliance selection means configured to allow a user to choose a given compliance threshold value based on a patient category to be treated and a ventilation mode to be implemented.

2. Ventilator according to claim 1, characterized in that the compliance selection means are configured to allow selection of a patient category chosen from adult, child and infant.

3. Fan according to claim 1, characterized in that the compliance selection means are configured to allow selection of a ventilation mode chosen from among the barometric and volumetric ventilation modes.

4. Ventilator according to claim 1, characterized in that the patient circuit (11) is a dual-branch circuit.

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