Respiratory humidification system

The present invention relates to a gas supply system, and more particularly to, a respiratory humidifier system that humidifies the gas breathed by a patient or other human in need of the gas.

Existing respiratory humidifier systems that supply a humidified body (eg, oxygen gas or anesthetic gas) to a patient or other person in need of a humidified gas are often, if not all, temperature regulated. Operates as a device. That is, in order to obtain a desired temperature for the humidified body exiting the humidifier, the temperature of the gas exiting the humidifier in the breathing circuit is detected, and the heat source responds to the change in the temperature of the gas. Is controlled. An example of this type of humidifier control system is disclosed in Applicant's earlier US Pat. No. 5,558,084. This control method has various drawbacks including the following drawbacks.

If the temperature of the gas entering the humidifier is high (close to the desired temperature for the gas leaving the humidifier), it is fed to the gas by a humidification process to obtain that desired temperature. Only a small amount of heat is needed to do so. Therefore, only a small amount of gas humidification can be obtained. The reliance on temperature sensors in this control method means that improper placement or connection of temperature sensors can result in poor performance of the entire humidification and breathing system.

There is a lack of flow sensors that allow easy detection of specific breathing circuit conditions and allow the humidifier (and / or gas supply) to operate properly. Conventionally, the flow rate sensor has not been used in the humidification system due to the lack of mechanical strength and the problem of condensation on the flow rate sensor that causes improper flow detection.

The gas is supplied to the patient with an inappropriate pressure / humidity combination. It is known that the gas to be administered to a patient requires a certain level of humidity. Suitable humidity values differ between the intact airway (eg, face mask), which is an untouched airway, and the bypassed airway (bypassed airway), which is a bypass-formed airway. There is. It is not possible to ensure that such required temperature / humidity values are obtained by temperature detection alone.

Some existing respiratory humidifiers require the user to adjust a dial that has little or no intuitive relationship to the actual physical parameters that the user seeks to adjust. This dial provided the required gas outlet temperature and / or in the conduit connecting the humidifier to the patient (and, in some cases, the conduit connecting the patient to the gas supply device in reverse). Often regulates the heat supplied by the heater wire. The most important parameter in supplying a humidified body to a patient is the humidity of the gas, as the patient's airways can dry very quickly if the humidity of the gas is inadequate. Therefore, the user has little or no knowledge of where the dial should be set to produce the desired result of obtaining the optimum humidity of the gas supplied at the current flow rate. .. An automated system in which the user only needs to inform the humidifier of whether the patient receiving the humidified body has an intact airway or a bypass airway will bring great advantages.

Many conventional respiratory humidifiers display the temperature of the gas being supplied to the patient. As mentioned above, the most important parameter in the respiratory humidification system is the humidity of the gas. In many cases, the indicated temperature is independent of the actual humidity of the gas supplied to the patient because it is heating in the supply circuit and can therefore mislead the average healthcare professional. Therefore, it would be beneficial if the indicated temperature was somehow related to the humidity of the gas being supplied to the patient, or if the indicated temperature indicated the temperature of such supplied gas. Let's go.

<p> Therefore, it is an object of the present invention to provide a respiratory humidifier system that overcomes the drawbacks, at least in some respect, or at least gives those skilled in the art a beneficial option.</p>

<p> A first aspect of the invention is a humidifier for humidifying a gas stream to be supplied to a patient or other human in need of gas, which retains a certain amount of water. A humidifying chamber means having an inlet and an outlet allowing the gas flow to pass through, and the humidifying chamber to supply water vapor to the gas flow passing through the humidifying chamber means. The gas is configured to heat the constant amount of water within the means, and the heating means provided adjacent to the humidifying chamber means and the gas to a patient or other person in need of the gas. A gas transport path means connected to the outlet of the humidifying chamber means for transporting a stream and having a patient-side end on the terminal side of the end connected to the outlet of the humidifying chamber means, and the said. After a humidity detector that detects the humidity of the gas stream being supplied to the patient, a timer means that can be used to time a particular humidifier event, and a predetermined alarm wait time. An alarm means that can be activated to supply an alarm signal, and a storage means that stores said alarm wait time for a plurality of associated detected humidity values. It is a control means, and the control means is made to (i) receive the input of the detected humidity value from the humidity detecting means, and (ii) acquire the alarm waiting time associated with the detected humidity value from the storage means. (Iii) start the timer means, (iv) wait until the elapsed time by the timer means is approximately equal to the alarm standby time, and (v) activate the alarm means to supply the alarm signal. It is provided with a control means for storing a program to be operated.</p><p> A second aspect of the invention is a humidifier for humidifying a gas stream to be supplied to a patient or other human in need of gas, which retains a certain amount of water. A humidifying chamber means having an inlet and an outlet allowing the gas stream to pass through, and the humidifying chamber to supply water vapor to the gas stream passing through the humidifying chamber means. A heating means configured to heat the constant amount of water in the means, adjacent to the humidifying chamber means, and a heating means power to monitor the power level used by the heating means. For a usage amount detecting means, a heating means temperature detecting means for detecting the temperature of the heating means, a gas flow temperature detecting means for detecting the temperature of the gas flow, and a patient or another person who needs the gas. A gas transport path means connected to the outlet of the humidifying chamber means for transporting the gas flow and having a patient-side end on the terminal side of the end connected to the outlet of the humidifying chamber means. , An alarm means that can be activated to supply an alarm signal after a predetermined alarm standby time, and a control means, the control means, (i). The difference temperature is determined by subtracting the gas temperature measured by the gas flow temperature detecting means from the heating means temperature detected by the heating means temperature detecting means, and (ii) the heating means power consumption detecting means. The required power value for the heating means is determined, (iii) the heat conductivity value is calculated by dividing the required power value by the difference temperature, and (iv) the calculated heat conductivity value is a predetermined minimum permissible value. It is provided with a control means for storing a program for activating the alarm means when the value is smaller than the thermal conductivity value.</p><p> It is relevant to the present invention that various modifications can be made to the configuration and various embodiments and applications of the invention without departing from the scope of the invention as defined in the accompanying claims. It will be understood by those skilled in the art. The disclosures and explanations herein are for illustration purposes only and are not intended to be limiting.</p>

The present invention envisions an embodiment having the following structure, which comprises the above-mentioned one and merely shows a specific example. In the following, one of the preferred embodiments of the present invention will be described with reference to the accompanying drawings.

With reference to the accompanying drawings, in particular FIG. 5, these figures show an example of a humidifier or respiratory air humidification system that includes a preferred embodiment of the present invention. In this breathing air humidification system, a ventilator, a gas, having an outlet 2 for supplying a gas (eg, oxygen, anesthetic gas, or air) to the inlet 3 of the humidifying chamber means 4 via a conduit 6. Includes supply means or blower 1. The humidifying chamber means 4 includes, for example, a plastic molding chamber having a metal base 7, and the metal base 7 is in contact with the plastic molding chamber and is hermetically sealed. The humidifying chamber means 4 is configured to hold a constant volume of water 8 heated by the heater plate means 9 under the control of the humidifier or the controller of the humidifier 10 or the control means 11.

When the water in the humidifying chamber 4 is heated, this water slowly evaporates, mixing the gas flow from the ventilator 1 through the humidifying chamber with water vapor. Thus, the humidified gas exits the humidifying chamber 4 via the outlet 12 and is delivered to the patient or other human 13 in need of such gas via the gas transport path or the intake conduit 14. A heating wire means 15 that can be energized under the control of the control means 11 is provided to reduce condensation in the intake conduit 14 and raise the temperature of the gas supplied to the patient 13. You may.

In Figure 1, a respiratory mask 16 is shown over the patient's nose and mouth (called the "Intact Airways" gas supply), but with a supply tube to bypass the patient's airways. It must be understood that there are various forms of gas supply such as intubation (known as "Intubated Airways" gas supply) in which the patient is placed in the patient's respiratory tract. It is also possible to provide a return route for returning the patient's exhaled air to the ventilator 1. In this case, a suitable fitting such as a "Y-shaped part" is connected to the patient 13, the intake conduit 14, and the inlet (not shown) of the ventilator 1 (not shown). It is possible to install it between (not) and.

The control means 11 can include, for example, a microprocessor or logic circuit having associated memory or storage means, which memory or storage means is in its software when its program is executed by the control means 11. It stores software programs that control the operation of the humidification system according to the instruction set of and in response to external inputs. For example, the control means 11 can be supplied with input from the heater plate 9 so that information about the temperature and / or power consumption of the heater plate 9 is given to the control means 11. In addition to this, the control means 11 can be supplied with an input of the temperature of the gas stream, for example, the temperature detecting means or the temperature probe 17 of the patient to indicate the temperature of the gas being received by the patient. It can be provided at or near the location, and yet another temperature probe 18 indicates to the control means 11 the temperature of the humidified body when the humidified body flow exits the outlet 12 of the humidifying chamber 4. It can also be provided for the purpose. Further, a flow rate detecting means or a flow probe 19 can be provided anywhere in the breathing circuit (the "breathing circuit" includes a humidifier portion through which the gas flow passes). Since both the flow probe 19 and the temperature probe 18 can be provided in the form of one probe as described below, the flow probe 19 is shown in the same position as the temperature probe 18 in FIG.

Yet another input to the control means 11 is for the user (eg, the medical professional or the patient himself) to set the desired gas temperature of the gas to be fed, or the desired humidity level of the gas to be fed. It can be a user input means or switch 20 that can be used to make this possible, or the control of heating performed by the heater wire 15 and the selection of some automatic gas supply modes (discussed below). Other functions such as can be controlled by the switch 20.

Some preferred embodiments of the respiratory humidification system (or a portion thereof) will be described in more detail below.<u style="single">Flow probe</u> With reference to FIGS. 1 and 2, these figures show the preferred form of the flow probe 19. The flow probe 19 is formed by molding a plastic material such as polycarbonate and holds a wire conductor (reference number 48 in FIGS. 3 and 4) that exchanges electrical signals with the control means 11. It is preferable to include the base portion 30 configured in. A shaft 31 protrudes from the base 30, which has at least one sensor housing means 32, 33 protruding from an end distant from the base 30. The sensor housing means 32 and 33 have a circular cross section, a substantially tapered or conical vertical cross section, and a rounded tip at an end far from the base 30 (detection end 36). It is preferable to have.

As shown in FIG. 1, two sensor housing means 32, 33 are provided. In the embodiment shown in the figure, one sensor housing means 32 is provided as a temperature detecting means, while the other sensor housing means functions as a flow rate detecting means. Detection means 34, 35, such as a thermistor (temperature-dependent resistor), provided to detect the separate characteristics of the temperature and flow rate of the gas flowing through the humidification system, are inside the sensor housing means 32, 33. It is located in. In the case of the temperature detecting means 34, the control device 11 can apply a voltage across the thermistor and receive a temperature signal in the form of an electric current passing through the thermistor, which depends on the temperature of the gas. To protect the thermistor 34, the sensor housing 32 completely covers or encapsulates the thermistor, but gains because there is only a thin layer of plastic material between the thermistor and the gas stream. The temperature readings made are still accurate.

In the case of the flow rate detecting means 35, if necessary, the control device 11 supplies the thermistor with a current for a duration sufficient to heat the thermistor to a first known temperature, and then supplies the current. It is possible to cut and detect the temperature change of the thermistor (by detecting the change in the resistance of the thermistor). The control device 11 can then activate the timekeeping means to measure the length of time it takes for the thermistor temperature to drop to a second predetermined temperature. As the gas removes heat from the heated thermistor 35, the time it takes for the thermistor 35 to change from a first known temperature to a second known temperature and a known cross-sectional area of the gas flow (eg 12 mm in diameter). A display of gas flow rate is given to the controller 11. It can be seen that the thermistor 35, unlike the thermistor 34, is neither covered by the sensor housing nor encapsulated. This is because any material layer between the thermistor 35 and the gas stream affects the thermal conductivity from the thermistor to the gas, thus reducing the accuracy of the flow measurement.

In one of the more preferred embodiments, the gas flow is supplied by supplying an electric current to raise the temperature of the thermistor 35 to a temperature higher than the temperature of the gas flow by a preselected differential temperature (eg, 60 ° C). Flow rate is measured. In this case, the control device 11 measures the power required by the thermistor 35 to maintain the fixed temperature difference. The power usage associated with the cross-sectional area of the gas flow (eg, a conduit with a diameter of 12 mm within the area of the flow probe) gives the controller 11 an indication of the flow rate and the controller quantifies the actual flow rate of the gas. to enable. In order for the thermistor 35 to be able to maintain the differential temperature, it is necessary to measure the actual temperature of the thermistor 35 from time to time while heating the thermistor 35. This can be done by temporarily removing the heating current from the thermistor, applying a low detection voltage across the thermistor 35, and detecting the current passing through the thermistor 35. In this way, the resistance of the thermistor 35 can be measured quickly and the temperature value can be derived from the pre-stored unique "temperature" vs. "resistance" data for the thermistor 35. After that, the detection voltage can be removed and the heating current can be reapplied if a predetermined temperature difference has not been obtained, or if a predetermined temperature difference has not been obtained or the temperature. If the difference is too large, the controller 11 can delay the reheating to the thermistor 35.

Since the exposed surface of the flow probe 19 is generally lower than the temperature of the humidified body flow passing over this surface, condensation can occur on this exposed surface. The liquid water that collects on the surface of the flow rate thermistor 35 absorbs some of the heat generated by the thermistor, which can adversely affect the flow rate measurement. In order to reduce or eliminate the accumulation of liquid water on this sensor, the flow probe according to the preferred embodiment of the present invention is provided with at least one "winged portion" or protruding tab means, FIGS. 1 and 1. In the embodiment shown in 2, two tabbed means (37, 38, 39, and 40) are shown per sensor housing means (but one protruding tab means per sensor housing means). It is also possible to use). It is preferred that each tab means have a rectangular cross section and extend from the shaft 31 to the detection end of the sensor housing means along the length of the sensor housing means (although this protruding tab means of the sensor housing means). It will not necessarily be necessary to extend over the entire length). In this preferred embodiment, the outer edge of the protruding tab means is separated from the centerline of the sensor housing means by a substantially constant distance along the overall length of the sensor housing means. Since the sensor housing means is tapered, the vertical cross section of the protruding tab means is triangular, preferably extending vertically from the surface of the sensor housing means. It is preferred that the protruding tab means be integrally molded with the flow probe 19, but it is also possible to manufacture the protruding tab means separately and then attach it to the surface of the sensor housing means.

With reference to FIGS. 3 and 4, as shown in these figures, the flow probe 19 is inserted into the sensor inlet 41 within the conduit connector 42 during use. The sensor inlet 41 consists of a substantially cylindrical wall extending vertically from the conduit connector 42. The conduit connector 42 can connect the two conduits 43, 44 of the breathing circuit, or the conduit connector 42 can be formed as part of the conduit, for example as part of the intake conduit 14. is there. As most clearly understandable by FIG. 4, the flow probe 19 is used to ensure that each of the protruding tab means 37, 38, 39, 40 is aligned parallel to the gas flow. Positioned relative to gas flow (indicated by arrow). As condensation forms on the sensor housing means, the action of the gas stream flowing over the surface of the sensor housing means is coupled with a local low surface tension near the contact line between the protruding tab means and the surface of the sensor housing means. The condensate is allowed to flow away from the end 36 of the sensor. Thus, in the desired form, the condensate tends to flow away from the sensor end 36 towards the axis 31 along the crossing line (eg, line 45).

When inserting the flow probe 19 into the sensor inlet 41, the protruding tab means with respect to the gas flow (because the desired effect of removing the liquid from the sensor tip cannot be obtained if the alignment is inaccurate). To ensure accurate alignment, this preferred embodiment of the present invention is a generally "V" shaped locating tooth means 46 adjacent to a shaft 31 projecting from a base portion 30. Also includes. Complementary schematic "V" -shaped notches or fixed positioning recesses 47 are provided in the wall of the sensor entrance 41. Therefore, the user who inserts the flow probe 19 can easily allow the condensate to flow off the sensor tip as described above in order to insert the flow probe completely and reliably into the conduit (or conduit connector). You will recognize that it is necessary to rotate the flow probe until the positioning tooth means 46 and the positioning recess 47 are combined to ensure that the flow probe is accurately aligned.

Further, in order to ensure that the heat generated by the operation of the flow rate detection thermistor 35 does not substantially adversely affect the temperature detection thermistor 34, when aligning the positioning tooth means 46 and the positioning recess 47, The temperature and flow detection thermistors are arranged across the gas stream so that each of the temperature and flow detection thermistors is substantially unaffected by the presence of each other (ie, these thermistors are of the flow). It is possible to understand from Fig. 4 that they are not aligned in the direction). Further, the flow rate detection thermistor 35 for generating heat is arranged downstream of the temperature detection thermistor so that the heat generated by the flow rate detection thermistor 35 is removed from the temperature sensor by the gas flow.

The advantage obtained by providing the humidifier according to the preferred embodiment of the present invention with a reliable flow probe is that the humidifier detects the flow rate and / or temperature with respect to the automatic display condition of the humidifier. It is possible to identify conditions that may impair performance (eg, suction occurrence, circuit disconnection, and atomization treatment). As soon as it is determined that a particular identified condition has occurred, appropriate action can be taken (eg, the generation of an alarm or the removal of heat from the heater plate 9). For example, a humidifier determines if the temperature probe is improperly placed or removed from the breathing circuit, for example by not detecting any flow rate at the associated low (ambient) temperature. Is possible.

Some preferred applications or application examples of the flow probe according to the preferred embodiment of the present invention will be described below.

<u style="single">Humidifier control system-minimum power method</u> An important parameter of the gas flow supplied to a patient or other human 13 in need of gas is humidity. Excessively dry gas (having a low relative humidity of about 60% to about 70%) can dehydrate the patient's airways very rapidly, causing patient discomfort. Well known. It is preferred that the control device 11 of the humidifier according to the preferred embodiment of the present invention includes a control system that attempts to maintain the relative humidity of the gas stream at a desired level (relative humidity greater than about 90%). One of the situations where this type of control is desirable is when the temperature of the inlet gas relative to the humidifying chamber 4 has risen to the same temperature as the outlet gas temperature. In this situation, supplying enough energy to the water 8 in the humidifying chamber is not possible, as only very little energy should be supplied to this inlet gas (to raise the temperature of this inlet gas). It is not possible, and therefore insufficient water vapor is obtained to humidify the gas, and therefore the temperature of the gas supplied to patient 13 is reasonable, but its relative humidity is inadequate. When the temperature of the inflow gas is significantly lower than the required outlet gas temperature, a large amount of energy is supplied in the humidification chamber 4 in raising the gas temperature to the required required temperature value. It is possible to assume that the water in the gas has been evaporated and therefore the relative humidity of the gas will be high.

To control the humidity of the gas stream reaching the patient, the humidifier according to the invention requires information about the gas flow rate. This can preferably be achieved by inserting the flow probe into the gas stream, as described above. Next, this control system will be described with reference to the flow chart of FIG.

This control system begins at block 49, where the heater plate 9 is energized to supply heat to the water in the humidification chamber 4. At block 50, controller 11 has a required humidity already preset in memory by the manufacturer, or a requirement already entered by the user via user input such as user input 20 shown in FIG. Read the humidity. At block 51, the controller 11 receives information from the flow detection thermistor 35 to measure the flow rate of the gas flow (this measurement can be made as described above). At block 52, the controller 11 determines the minimum power required to produce the required humidity level in the gas flow at the detected flow rate. This can be achieved by performing the calculation using a calculation formula stored in the memory, or the data storage means or memory element associated with the control device 11 can be used with the detected flow rate. Having a data lookup table of the flow rate queried by the control means using the required humidity value and the minimum required power value associated with the flow rate at the various required humidity levels stored therein. preferable. The control means 11 detects the gas flow rate, receives the required humidity level input by the user, and calculates the evaporation rate required to obtain the required humidity level at the required flow rate (or was derived experimentally). It is possible to determine the required power level of the heater plate 9 by (obtaining the evaporation rate from a lookup table of values or pre-calculated values). The controller 11 then calculates (or experimentally derives) the power required to be supplied by the heater plate 9 to generate its determined evaporation rate and ensure the required humidity level is achieved. It is possible to get it from a lookup table of the calculated or precomputed values).

In block 53 (which is not an essential step in this method), the control means 11 uses the gas outlet temperature feedback supplied to the controller via the temperature sensor 18 (or the temperature sensing portion of the flow probe). By varying the temperature or power of the heater plate 9, the temperature of the gas exiting the outlet of the humidification chamber is preset in a known manner (by the manufacturer or user) (eg, 37 ° C). Adjust to.

At block 54, the current power usage of the heater plate 9 is quantified and a determination is made as to whether the current power usage of the heater plate is less than the value calculated in block 52. The current power consumption can be calculated by the controller 11 by, for example, detecting the current supplied to the heater plate and multiplying the detected current value by the heater plate supply voltage. Alternatively, the average power of the heater plate can be quantified by calculating the percentage of time the heater plate is energized and multiplying that percentage by the rated power value of the heater plate. .. For example, if the heater plate is energized for 40% of the time and the rated power of the heater plate is 150W, the average power used by the heater plate will be 60W. .. In this case, it is possible to assume that the heater plate voltage is constant and invariant. If the currently quantified power usage is greater than the minimum determined to be required to provide the required humidity level, control returns to block 50, in which block 50 is at block 54. The above steps were repeated until the judgment showed that the heater plate power consumption was reduced to a value lower than the level required to supply the properly humidified gas, and the patient was given the properly humidified gas. Will receive.

At this point, control proceeds to block 55, where the power supplied to the heater plate 9 (eg, pulses to the heater plate) to ensure that the gas is properly humidified. It can be increased to the power level determined in block 52 by varying the width-modulated feed voltage or simply by increasing the variable voltage supply. This raises the outlet gas temperature to a temperature higher than the set temperature, but this temperature rise is necessary to supply the appropriate humidity. An inspection is then performed at block 56 (not an essential step in the method) to see if the outlet gas temperature has dropped below a predetermined temperature (eg 37 ° C). Be told. When the outlet gas temperature drops below a predetermined temperature, the outlet gas is at a temperature sufficiently higher than the assumed gas inlet temperature, and the outlet gas has a required level of humidity. It can be considered that you are getting. If the outlet gas temperature has not dropped below a predetermined temperature, the calculated minimum voltage level will continue to be supplied to the gas. Therefore, (1) In the absence of a temperature sensor, the control system can continuously supply the minimum computational power required to obtain proper humidification to the heater plate, or (2) temperature sensor. If provided, the outlet temperature is required in a known manner until the control system operates in two modes, i.e., the power usage of the heater plate drops to a level that indicates inadequate humidification. The outlet gas temperature drops to a temperature lower than the preset temperature when the first "normal" operating mode is adjusted to temperature and the power usage of the heater plate drops to a level that indicates inadequate humidification. The power consumption of the heater plate to the calculated minimum level until it is shown that the inlet gas temperature has dropped enough to allow the humidification chamber to supply sufficient heat and humidity to the gas stream. It can be understood that it operates in a second control mode that serves to maintain the temperature.

<u style="single">Humidifier Control System-Desired Humidification Method</u> Next, a humidifier control system different from the above humidifier control system will be described with reference to FIG. 7. In this other preferred control system, it is possible to adjust the humidity of the gas exiting the humidification chamber 4 to any required level at any gas flow rate. This is achieved by quantifying the gas flow rate, preferably using the flow rate probe, in addition to information on "humidification chamber output" vs. "flow rate" and / or respiratory circuit characteristics.

An example of the humidification chamber output characteristics is shown in FIG. 7, which shows that at a particular required gas humidity level, after the temperature of the gas at the humidification chamber outlet drops very rapidly as the gas flow rate increases. It can be understood that the temperature settles down to a constant constant temperature. This information is experimentally derived for various gas outlet temperatures and humidity levels and recorded in a memory storage device searchable by control means 11 (eg, in the form of a single look-up table or multiple look-up tables). It is possible to be done.

With this control system, the user inputs a required humidity level to the control device 11 by a user input device, such as a user input means 20, which in this case can include a dial or an electronic keypad. The heater plate 9 is energized to heat the water in the humidification chamber 4, and the temperature probe 18 (or the temperature detection portion of the flow probe 19) supplies the control means 11 with a detection outlet gas temperature signal. Used for. Using the current flow rate and the detected temperature detected by the flow probe 19, controller 11 stores it in order to determine the target outlet gas temperature required to obtain the required humidity level at the current outlet gas flow rate. Examine the device.

At this point, the control means 11 controls the energization of the heater plate 9 to obtain a determined target outlet gas temperature that gives the required humidity level at the current gas flow rate. The energization of the heater plate 9 can take the form of pulse width modulation of a voltage power supply, for example to change the power delivered to the heater plate, or a variable voltage power supply on the heater plate. It can be supplied. When a change is made to the gas flow rate or the user-configured required humidity level, the controller 11 automatically determines the updated target outlet gas temperature from the storage device and gives it the target outlet gas temperature. Control the heater plate 9 appropriately.

For example, the user-set desired humidity level is H per liter of gas.₂ O 44 mg and the detected flow rate is F₁ If so, the controller 11 examines the table in the storage device and determines that a target outlet gas temperature of 37 ° C. is required. The controller 11 then energizes the heater plate 9 (eg, by PWM control of the supply voltage or supply current) so that the outlet gas temperature detected by the temperature sensor 34 is approximately equal to the target temperature of 37 ° C. And as a result H per liter of gas₂ The required absolute humidity of O 44 mg can be obtained.

In addition to this control system, the storage device associated with this control system 11 can also be given information related to the dew condensation characteristics of the inspiratory conduit. As the gas passes through the intake conduit, the heater wire 15 can be energized by the control means 11 to control additional heating to the gas and reduce condensation in the intake conduit. .. This also reduces changes in the humidity level of the gas along its conduit (because less water condenses from the gas in the form of condensation). In this control system, the control device 11 can adjust the heating supplied by the heater wire 15 so that it can control the temperature as well as the humidity of the gas stream (but in practice). The heater wire can only bring about a slight increase in temperature). However, if the gas is supplied at an excessive level (to produce a gas at a sufficiently high temperature) by causing a drop of water, the controller 11 will reduce the humidity of the gas. It may also be possible to use a heating wire setting. In this case, the control means 11 appropriately adjusts the heater plate setting and the heater wire setting to provide the patient with the required gaseous humidity and temperature (set by the user) for its maximum capacity. Will be done.

<u style="single">Automatic Humidifier-"Single Button Humidifier"</u> As a result of using either of the above control systems in the humidifier of FIG. 5, it will be possible to provide a humidifier that is extremely easy to use and requires only minimal input from the user. One specific example of an easy-to-use humidifier is as shown in FIG. 5, in which case the only user input is switch 20. The switch 20 preferably has several states or positions corresponding to a predetermined number of gas supply modes. It is possible to use one gas supply form as an intubation airway and another gas supply form as an intact airway. The corresponding optimum required humidity value and required temperature value for each position or state of the switch 20 are stored in the memory associated with the control device 11. For example, in the case of the intubation airway form, the optimum temperature is about 37 ° C and the optimum humidity value is H per liter of gas.₂ O can be about 44 mg, while in the case of the intact airway form, the optimum temperature is about 32 ° C and the optimum humidity value is H per liter of gas.₂ O can be about 30 mg.

By using either of the above control systems, it will be possible to control the operation of the humidifier as soon as the gas supply mode is known, without the need for further user involvement. The control device 11 repeatedly detects the outlet gas temperature and the outlet gas flow rate, and gives the patient 13 the optimum (or as close to the optimum) gas temperature and gas humidity as possible regardless of the change in the flow rate or the inlet gas temperature. The heater plate power and (if necessary) heater wire settings will be adjusted to provide automatically.

<u style="single">User output-Temperature display</u> Yet another feature of the humidifier according to yet another aspect of the present invention is the incorporation of a display means 60 (FIG. 5) for displaying the temperature of the gas supplied to the patient 13 to the user. Note that this feature does not depend on the presence of a flow probe in the respiratory circuit. The display means 60 is controlled by the control means 11. It is known that other respiratory humidifiers incorporate display means, but the temperature displayed by these display means is the patient-side end of the inspiratory conduit 14 (as detected by the temperature sensor 17). It is always fixed to either the temperature of the gas at or the temperature of the gas at the outlet of the humidification chamber (as detected by the temperature sensor 18).

Many medical professionals equate the amount of water contained in a gas with the indicated temperature. The temperature of the gas supplied to the patient as long as the gas supplied to the patient has a relative humidity of 100% (ie, the gas contains the maximum amount of water vapor that the gas can hold at its current temperature). Would be clinically accurate. However, if the supplied gas contains less water than the maximum possible amount of water at the current temperature of the gas, a humidifier that simply displays the temperature of the supplied gas will be available to medical professionals. It can be misleading and convince medical professionals that the patient is receiving a humidified body with a higher humidity than the actual humidity.

In a preferred embodiment of the present invention, the temperature displayed on the display means 60 is the lower of the temperature detected by the sensor 14 and the temperature detected by the sensor 18. For example, a temperature of 37 ° C at the gas outlet and H per liter of gas.₂ O 44 mg absolute humidity (approximately 100% relative humidity) has a temperature of 35 ° C at the patient-side end of the inspiratory conduit and H per liter of gas.₂ It would correspond to an absolute humidity of O 35 mg. Therefore, H per liter of gas₂ O 9 mg is condensed in the inspiratory conduit, but due to the temperature drop, the gas remains about 100% relative humidity along the inspiratory conduit. In this situation, a gas with 100% relative humidity at this temperature contains the amount of water displayed by the temperature 35 ° C, so the appropriate temperature to display to the user is 35 ° C.

However, at the gas outlet, the temperature is 37 ° C and the absolute humidity is H per liter of gas.₂ O 44 mg (100% relative humidity), temperature 39 ° C at the patient side end of the inspiratory conduit, and absolute humidity H per liter of gas₂ For O 44 mg, the most clinically appropriate temperature to display would be 37 ° C. This is because even if the temperature of the gas has already risen, the gas reaching the patient is no longer 100% relative humidity because there is no excess water already supplied to the gas along the inspiratory conduit. Since the gas temperature of 37 ° C corresponds to the amount of water in the humidified body, the absolute humidity of the gas reaching the patient is actually associated with the gas temperature of 37 ° C. In any case, since the patient-side end temperature is often measured at a distance of 30 cm or less from the patient, the temperature of the gas is often already low by the time the gas reaches the patient, and therefore more. The lower temperature of 37 ° C is a more appropriate temperature for medical professionals.

<u style="single">Automatic standby mode during gas-free flow</u> As mentioned above, in many existing humidification systems, the controller simply detects the temperature to control the power supplied by the humidifier heater plate 9 and / or the conduit heater wire 15. In situations where the gas supply means or blower 1 is separated from the breathing circuit, this type of controller will detect a lack of temperature because there is no gas flow through the temperature sensor. In this case, the controller increases the power supplied to the humidifier heater plate 9 and / or the heater wire 15 so that the controller considers the gas still flowing in the breathing circuit. Attempts to raise the temperature. Since the temperature sensor does not show any temperature rise in its "flow", the controller 11 may continue to increase the power supplied to heat the non-existent gas stream to dangerous levels. After this, if the gas supply is resumed, the gas supplied to the patient can reach dangerous temperatures.

In order to avoid the above series of events from occurring, the flow rate sensor according to the preferred embodiment of the present invention can be incorporated in the humidification system. In this case, the controller can determine if the humidifier has sufficient gas flow (eg, 1.5 liters per minute) for normal safe operation. If it is discovered that the gas flow is inadequate, the humidifier can be put into a safe operating mode. This safe operating mode limits the temperature of the heater plate 9 and / or the load cycle of the voltage supplied to the humidifier heater plate 9 and / or the heater wire 15 (ie, power level control). Can be included.

<u style="single">Humidity alarm device</u> Alarms (auditory alarms and /) to alert the patient (or medical professional) when the gas supplied to the patient is below (or above) the required humidity level for a certain amount of time. Or a visual alarm device) should be provided in the humidification system. The alarm device should be configured to issue an alarm after a length of time determined according to the difference between the required humidity and the actual humidity level being supplied to the patient. It has become clear. The greater this difference, the sooner the alarm must be issued.

FIG. 8 shows an example of a conceivable graph of how the time delay can be set based on the patient's physiological humidity needs. Several different "humidity profiles", each based on a predetermined required humidity value (the above example shows a required humidity value of 37 ° C), can be stored in the storage element. It is possible. Control so that the control means can measure the humidity difference and examine it in a table (a table selected based on the required humidity value) that gives an appropriate waiting time before the alarm is generated. The relationship between the temperature difference and the alarm standby time can be adequately expressed in the form of a table stored, for example, in ROM (read-only storage) to be read by means 11. Another method of measuring the humidity of the feed gas is to detect the actual dew point of the gas (the temperature at which condensation begins to occur) and determine the difference between the actual dew point and the required or optimum dew point (eg, 37 ° C). It is to quantify. The actual dew point can be regarded as, for example, the lower temperature of the temperature of the humidifying chamber 4 and the temperature of the conduit 14.

<u style="single">Drainage alarm</u> In a breathing air humidification system that includes a humidification chamber 4, it is essential that a particular minimum water level be maintained so that the humidifier has the ability to supply water vapor to the gas supply. Therefore, medical professionals who administer a humidified body to a patient should occasionally check the water level and replenish water as needed. This work is sometimes overlooked.

It is possible to use the flow probe 19 in a humidification system that automatically determines when the water level drops to an inadequate level and raises an alarm. The temperature of the heater plate 9, the temperature of the humidification chamber 4 (or the temperature at the outlet of the humidification chamber), and the power requirement of the heater plate 9 (the amount of power currently supplied to the heater plate) are all detected and heat is detected. It is used in the following equation that gives the value of conductivity. Thermal conductivity = heating plate power requirement / (humidator plate temperature-humidifying chamber temperature) The controller 11 has a predetermined threshold (itself, the flow rate) that can be determined experimentally at various gas flow rates. Compare the calculated thermal conductivity values to (depending on the gas flow rate measured by probe 19). This calculated thermal conductivity value can be updated, for example, every 5 minutes, for example, 5 minutes or 10 minutes have passed since the calculated thermal conductivity value dropped to a value lower than the above threshold value. An alarm can be issued (or an alarm can be issued immediately). Examples of experimentally determined thermal conductivity and preferred thresholds at various flow rates are shown below. Flow rate = 10 liters / minute Thermal conductivity = 1.26W / ° C (when there is sufficient water in the humidification chamber 4) Thermal conductivity = 0.26W / ° C (when there is no water in the humidification chamber 4) Predetermined threshold = 0.5W / ° C Flow rate = 40 liters / minute Thermal conductivity = 1.81 W / ° C (when there is sufficient water in the humidification chamber 4) Thermal conductivity = 0.42 W / ° C (when there is no water in the humidification chamber 4) ) Predetermined threshold = 0.8W / ° C

Predetermined thresholds at several flow rates can be stored in ROM accessible by controller 11, which allows the controller to simply measure the current flow rate of the gas and conduct thermal conductivity. It is possible to calculate the rate value, access the table in ROM based on the current flow rate, and read the associated predetermined threshold. If the calculated threshold is greater than the calculated thermal conductivity value, controller 11 alerts the patient after waiting for a predetermined time (eg, 5 or 10 minutes). It is possible to restore the proper water level without loss of humidity of the supplied gas.

<u style="single">Humidification room target value tracking</u> In a respiratory humidification system that includes a conduit heater wire, it is common to adjust the temperature and humidity so that the gas supplied to the patient arrives at the required temperature and humidity level. In some situations, the conduit heater wire 15 provides sufficient energy to raise the temperature of the gas in the breathing circuit to obtain the required temperature in the patient. In some cases, the limited power obtained from the conduit heater wire (even at 100% load cycle) may be insufficient to raise the gas temperature to the required temperature of the gas for the patient. More specifically, the inability of such a humidification system to maintain the required gas temperature at the patient-side end of the conduit 14 is generally due to the humidified body giving too much heat to the vessel wall. Condensation or "dripping of water droplets" may occur inside. A control device according to a preferred embodiment of the present invention includes a system for minimizing or alleviating the above problems.

Thus, the respiratory humidification system according to yet another preferred embodiment of the present invention maintains a "temperature gradient" along the length of the conduit 14 rather than attempting to maintain the patient gas temperature at the required level. Attempts to adjust the required patient temperature (or airway target). The airway target value is calculated as follows. Airway target value = humidification chamber outlet temperature + offset In the above equation, the "offset" value is, for example, 3 ° C, which is equal to the required temperature gradient along the conduit 14. Note that the "offset" value chosen depends on the physical properties and shape of the conduit.

For example, if the offset value is 3 ° C and the outlet gas temperature of the humidification chamber 4 is 37 ° C, then the heater wire 15 (to keep the temperature of the gas supplied to the patient at 40 ° C) Properly energized (for example, by adjusting the load cycle). Similarly, if the humidification chamber outlet temperature drops to 31 ° C, the temperature of the gas supplied to the patient will be adjusted to arrive at 34 ° C. In both cases, a temperature gradient or temperature difference of + 3 ° C is maintained along the conduit to minimize or mitigate condensation.

It is discovered that the required offset value cannot be maintained (ie, for example, the heater wire is a gas in the conduit by a temperature sensor located, for example, near the patient-side end of the conduit 14. In order to maintain the required offset temperature along the conduit 14, the controller 11 (eg, on the heater plate 9) if it is not possible to raise the temperature of the Decrease the humidification chamber outlet temperature (by reducing the load cycle of the supplied power). For example, if the offset temperature value cannot be maintained above 2 ° C for 15 minutes, the controller should be programmed to start lowering the humidification chamber outlet temperature by 0.5 ° C (eg to the lowest value of 35.5 ° C). Is possible. For example, if the offset value is 3 ° C and the initial humidification chamber outlet temperature is 37 ° C, the gas supplied to the patient must be adjusted to arrive at 40 ° C. However, if the gas arriving at the patient is 38.6 ° C (actual offset value or actual temperature difference is only 1.6 ° C), controller 11 reduces the humidification chamber outlet temperature to 36.5 ° C after 15 minutes. .. After that, if the above calculation is repeated and the temperature of the gas arriving at the patient cannot be maintained at 39.5 ° C, it is reconsidered that the control device 11 lowers the temperature of the humidifying chamber. The above process is repeated until the humidification chamber outlet temperature reaches a temperature at which the required conduit offset temperature can be maintained. In addition, the controller 11 reconstitutes the gas supplied to the patient with the required temperature (only if it is possible for the gas supplied to the patient to be brought back to the required temperature within the constraints of the offset temperature). It is possible to attempt to raise the temperature of the gas at the outlet of the humidification chamber so that it can be done. This will only be possible if the surroundings change.

Thus, at least in a preferred embodiment of the invention, the invention, including all or part of the above features, provides a respiratory air humidification system that enables the realization of humidity control and / or temperature control of the humidified body. The gas flow probe according to one of the embodiments of the present invention allows the realization of accurate flow measurement without the formation of condensation which adversely affects the sensor. This improvement in accuracy is partly based on a positioning system that ensures accurate alignment of the flow probe and / or temperature probe in the gas stream. Since the control system according to the present invention can accurately detect the flow rate by this flow rate sensor, it is possible to supply the patient with a gas flow adjusted to the required humidity. This flow sensor also allows for the realization of "automatic" control so that the user does not have to constantly monitor the output of the humidifier and change the input to achieve the desired change, and the patient. It is only necessary for the user to provide information on the gas supply status to the humidifier, and the humidifier can provide the required gas temperature and humidity without further user input. Further, the humidifier according to the present invention displays a gas temperature value that is clinically appropriate as a temperature value of the gas reaching the patient. In addition to this, respiratory humidification according to another preferred embodiment of the present invention provides various safety improvements as compared to the prior art.

<figref num="1">FIG. 5 is a front view of a flow probe configured by one of the preferred embodiments of the present invention.</figref><figref num="2">It is explanatory drawing which looked at the flow rate probe of FIG. 1 from the bottom.</figref><figref num="3">It is sectional drawing side view of the breathing circuit which shows the flow rate probe of FIG. 1 mounted in the conduit.</figref><figref num="4">It is a cross-sectional view of the breathing circuit of FIG. 3 seen from the bottom showing the flow probe of FIG. 1 mounted in the conduit.</figref><figref num="5">It is a schematic diagram of the respiratory air humidification system including the flow probe of FIG.</figref><figref num="6">FIG. 5 is a flow diagram of one preferred embodiment of a humidity and temperature control system used in the respiratory humidification system shown in FIG.</figref><figref num="7">"Target outlet temperature required (to obtain required humidity level)" exemplifying one of the preferred embodiments of the humidity and / or temperature control system used in the respiratory humidification system shown in FIG. It is a graph of "flow rate".</figref><figref num="8">It is a graph of "humidity (or dew point)" vs. "alarm standby time" in a specific example of a breathing air humidification system such as the breathing air humidification system shown in FIG.</figref>

Code description

3 ... Inlet 4 ... Humidifying chamber means 8 ... Water 9 ... Heating means 11 ... Control means 14 ... Gas transport path 17 ... Temperature detecting means 18 ... Temperature detecting means 19 ... Flow probe 20 ... User input means 32 ... Sensor housing means 33 ... Sensor housing means 34 ... Temperature detection means 35 ... Flow detection means 36 ... Detection end 37. .. Tab means 38 ... Tab means 39 ... Tab means 40 ... Tab means 60 ... Display means