Humidification of breathing gases

Abstract

The present disclosure relates to humidification of respiratory gas. A humidifier for a respiratory device is provided for delivering a humidified flow of breathable gas to a patient, comprising: a humidifier chamber configured to store a supply of water for humidifying the flow of breathable gas, the humidifier chamber comprising a first heating element configured to heat the supply of water; a relative humidity sensor for detecting the relative humidity of ambient air and generating a signal indicating the relative humidity of the environment; a first temperature sensor for detecting the temperature of the ambient air and generating a signal indicating the temperature of the environment; and a controller configured to determine the absolute humidity of the ambient air based on the signals generated by the relative humidity sensor and the first temperature sensor and control the first heating element to provide a predetermined relative humidity to the flow of breathable gas.

Description

[0001] This application is a divisional application of the invention patent application with application number 2021107098087, application date March 6, 2009, and invention name “Humidification of breathing gas”. The patent application with application number 2021107098087 is a divisional application of the invention patent application with application number 2017111136672, application date March 6, 2009, and invention name “Humidification of breathing gas”. Patent application No. 1136672 is a divisional application of invention patent application No. 2014105431009, filed on March 6, 2009, with the title of “Humidification of breathing gas”, and patent application No. 2014105431009 is a divisional application of invention patent application No. 200910138707.8, filed on March 6, 2009, with the title of “Humidification of breathing gas”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of priority to U.S. patent applications No. 61 / 034,318, filed March 6, 2008, No. 61 / 042,112, filed April 3, 2008, and No. 084,366, filed July 29, 2008, the entire contents of each of which are incorporated herein by reference. Technical Field

[0004] The present invention relates to systems and methods for controlling the humidity of breathable gases for use in ventilation systems of various forms of respiratory apparatus, including invasive or non-invasive ventilation, continuous positive airway pressure (CPAP), bi-level therapy and treatment for sleep disordered breathing (SDB) conditions such as obstructive sleep apnea (OSA) and various other respiratory disorders and diseases. Background Art

[0005] Respiratory devices typically have the ability to change the humidity of the breathable gas in order to reduce patient airway drying and patient discomfort and related complications caused by airway drying. The use of a humidifier placed between the airflow generator and the patient's mask can produce humidified gas that minimizes drying of the nasal mucosa and increases patient airway comfort. In addition, in colder environments, it is usually more comfortable to apply warm air to the facial area in and around the mask rather than cold air.

[0006] There are many types of humidifiers available, although the most convenient form is that which is integrated with or configured to be connected to an associated respiratory device. While passive humidifiers can provide some relief, heated humidifiers are usually required to provide sufficient humidity and temperature to the air so that the patient will feel comfortable. A humidifier typically includes a water bucket having a capacity of several hundred milliliters, a heating element for heating the water in the bucket, a controller to enable the humidity level to be varied, a gas inlet to receive gas from a gas flow generator, and a gas outlet adapted to be connected to a patient conduit that transmits humidified gas to a patient mask.

[0007] Typically, the heating element is integrated into a heating plate that is located beneath the tub and in thermal contact with the tub.

[0008] The humidified air may cool along the path of the conduit from the humidifier to the patient, resulting in a "rain-out" phenomenon, or condensation forming on the inner wall of the conduit. To overcome the above problems, a known solution is to additionally heat the gas supplied to the patient by a heating wire circuit inserted into the patient's conduit, wherein the patient conduit supplies the humidified gas from the humidifier to the patient's mask. Such a system is described on page 97 of Mosby's Respiratory Care Equipment (Seventh Edition). Alternatively, the heating wire circuit can be positioned on the wall of the patient's conduit. Such a system is described in U.S. Patent 6,918,389.

[0009] In a hospital environment, the ambient temperature in the hospital is controlled by air conditioning to be typically maintained at, for example, about 23° C. Therefore, the required temperature of the humidified gas provided by the respiratory device can be controlled within fixed temperature parameters. The controlled temperature parameters ensure that the humidified gases are maintained at a temperature above their dew point to prevent condensation in the respiratory tube.

[0010] Humidifiers are also often used in home care settings, for example in the treatment of respiratory and sleep apnea disorders. Humidification systems used with home CPAP devices are subject to many limitations due to cost constraints and the need to make the system small and lightweight, with a comfortable hose and mask, and to have low complexity for untrained users. In systems used in clinical or hospital settings, this limitation is generally not a problem, and temperature and humidity sensors can be placed in the airway and adjacent to the patient's nose to provide direct feedback to the control system, thereby ensuring good results. The cost, size, weight and discomfort of the above systems are not suitable for home use. Home users can therefore only rely on experience gained through trial and error to obtain acceptable results.

[0011] In a home care environment, the range of ambient temperature and gas temperature may far exceed that of a hospital environment. In home care, the ambient temperature may be as low as 10°C at night, while the temperature during the day may exceed 20°C. Such temperature variations cause the above-mentioned commonly used control techniques to encounter disadvantages. With a humidifier of the above-mentioned type, condensation (or rain wash) on the breathing tube will occur at least to some extent. The degree of condensation depends greatly on the ambient temperature, and the greater the difference between the ambient temperature and the gas temperature, the greater the condensation. The formation of a large amount of water in the breathing tube causes considerable inconvenience to the patient and may accelerate the cooling of the gas and eventually block the tube, produce water flowing sounds in the tube, or water may be sprayed into the patient's body. In addition, the patient may also feel uncomfortable when the temperature of the transmitted breathing gas differs greatly from the ambient temperature. Excessive condensation can also lead to ineffective use of the water in the humidifier chamber of the humidifier.

[0012] Attempts to address these issues associated with home breathing systems have been made by monitoring ambient temperature and air flow as inputs to a control algorithm that predicts a corrected heating input to track the user's initial setting. However, this approach still relies on the user to determine an appropriate setting for each use case. Summary of the invention

[0013] One approach is a respiratory device that addresses patient complaints of insufficient warmth of breathable gas delivered to a patient interface, symptoms of nasal dryness, and / or excessive condensation within an air delivery hose.

[0014] Another aspect is a respiratory device that allows a patient to select the temperature and / or relative humidity and / or absolute humidity of the breathable gas delivered to the patient interface. In an alternative and / or additional aspect, the absolute humidity of the humidifier outlet is controlled to adjust to a predetermined relative humidity delivered to the patient.

[0015] Yet another aspect is a respiratory device that provides a flow of humidified gas at a predetermined temperature and / or humidity to a patient interface while taking into account changes in ambient temperature and / or humidity.

[0016] Yet another aspect is a respiratory device that provides a flow of humidified breathable gas at a predetermined temperature and / or humidity to a patient interface while taking into account varying the flow rate of the humidified flow of breathable gas.

[0017] Yet another aspect relates to a respiratory device including a flow generator and a humidifier connectable together to allow communication between the flow generator and the humidifier and / or indicate connection and / or removal.

[0018] Yet another aspect relates to a respiratory device comprising a humidifier and a heated air delivery tube, hose or conduit. The duty cycle of the heating element of the humidifier and the duty cycle of the heating tube can be controlled so that the combined duty cycle of the two duty cycles does not exceed 100%, and / or so that the heating element and the heating tube of the humidifier do not receive power at the same time. In an alternative and / or additional aspect, the heating element and / or the heating tube of the humidifier adjust the temperature rather than applying a fixed duty cycle. In another alternative and / or additional aspect, the temperature of the humidified flow of breathable gas in the air delivery tube is measured downstream of the humidifier so as to be adjusted to a predetermined relative humidity for delivery to the patient.

[0019] Another aspect relates to an air flow generator that detects the connection of a conduit, such as a heating conduit, and / or the size of the connected conduit, and / or the separation of the conduit from a humidifier.

[0020] Yet another aspect relates to an air flow generator including constants such as control parameters, for example stored in a table, which can be trilinearly interpolated to control a humidifier and / or a heated tube.

[0021] Still another aspect relates to a respiratory device and a controller thereof, the device comprising a humidifier and a non-heated tube connectable to the humidifier.

[0022] Yet another aspect relates to a humidifier controller that converts a voltage measured, for example, across a thermistor, into a temperature.

[0023] Another embodiment relates to a breathing apparatus, which includes an airflow generator and a humidifier, wherein the airflow generator and the humidifier are connectable to each other and can transmit data and / or instructions via a serial communication link.

[0024] According to an exemplary embodiment, a humidifier of a respiratory device for delivering a humidified flow of breathable gas to a patient includes a humidifier chamber configured to store a supply of water to humidify the flow of breathable gas, the humidifier chamber including a first heating element configured to heat the supply of water; a relative humidity sensor that detects relative humidity of ambient air and generates a signal indicative of the ambient relative humidity; a first temperature sensor that detects temperature of the ambient air and generates a signal indicative of the ambient temperature; and a controller configured to determine absolute humidity of the ambient air from signals generated by the relative humidity sensor and the first temperature sensor to control the first heating element to provide a predetermined absolute humidity to the flow of breathable gas.

[0025] According to another exemplary embodiment, a humidifier of a respiratory apparatus for delivering a humidified flow of breathable gas to a patient includes a humidifier chamber configured to store a supply of water for humidifying the flow of breathable gas, the humidifier chamber including a first heating element configured to heat the supply of water; an absolute humidity sensor that detects absolute humidity of the humidified flow of gas and generates a signal indicative of the absolute humidity; and a controller configured to receive the signal generated by the absolute humidity sensor and to control the first heating element to provide a predetermined absolute humidity to the flow of breathable gas.

[0026] According to another exemplary embodiment, a humidifier of a respiratory apparatus for delivering a humidified flow of breathable gas to a patient includes a humidifier chamber configured to store a supply of water for humidifying the flow of breathable gas, the humidifier chamber including a first heating element configured to heat the supply of water; a relative humidity sensor that detects relative humidity of ambient air and generates a signal indicative of the ambient relative humidity; a first temperature sensor that detects temperature of the ambient air and generates a signal indicative of the ambient temperature; and a controller configured to determine absolute humidity of the ambient air from the signals generated by the relative humidity sensor and the first temperature sensor and to control the first heating element to provide a predetermined absolute humidity, a predetermined temperature, and / or a predetermined relative humidity to the flow of breathable gas.

[0027] According to another exemplary embodiment, a humidifier of a respiratory apparatus for delivering a humidified flow of breathable gas to a patient includes a humidifier chamber configured to store a supply of water for humidifying the flow of breathable gas, the humidifier chamber including a first heating element configured to heat the supply of water; an absolute humidity sensor that detects absolute humidity of ambient air and generates a signal indicative of the ambient absolute humidity; a first temperature sensor that detects a temperature of the ambient air and generates a signal indicative of the ambient temperature; and a controller configured to control the first heating element to provide a predetermined absolute humidity, a predetermined temperature, and / or a predetermined relative humidity to the flow of breathable gas.

[0028] According to yet another exemplary embodiment, a respiratory apparatus for providing a humidified flow of breathable gas to a patient includes a flow generator that generates a flow of breathable gas and a humidifier as described above.

[0029] According to yet another exemplary embodiment, a method of humidifying a flow of breathable gas provided to a patient includes determining an absolute humidity of ambient air used to form the flow of breathable gas; and controlling a temperature of supplied water used to humidify the flow of breathable gas to provide a predetermined absolute humidity corresponding to a predetermined temperature and a predetermined relative humidity of the gas flow delivered to the patient.

[0030] According to another exemplary embodiment, a humidifier of a respiratory device for delivering a humidified flow of breathable gas to a patient includes a humidifier chamber configured to store a supply of water for humidifying the flow of breathable gas. The humidifier further includes an inlet configured to receive the flow of breathable gas, a first heating element configured to heat the supply of water, and an outlet configured to deliver the humidified flow of breathable gas to a conduit. A controller is configured to control power supplied to the heating element to provide a predetermined absolute humidity to the humidified flow of breathable gas. The controller continuously adjusts the power supplied to the first heating element in response to changes in environmental conditions and / or the flow of breathable gas to continuously provide the predetermined absolute humidity.

[0031] According to another exemplary embodiment, a method of humidifying a flow of breathable gas provided to a patient includes determining an absolute humidity of ambient air used to form the flow of breathable gas; and controlling a temperature of supplied water used to humidify the flow of breathable gas to provide a predetermined absolute humidity to the humidified flow of gas. Controlling the temperature of the supplied water includes adjusting the temperature of the supplied water to continuously provide the predetermined absolute humidity in response to changes in the temperature of the ambient air, the relative humidity of the ambient air, the absolute humidity of the ambient air, and / or the flow of breathable gas.

[0032] According to yet another exemplary embodiment, a method of humidifying a flow of breathable gas provided to a patient includes detecting a temperature of a humidified gas flow at an end of a transmission hose configured to be connected to a patient interface; generating a signal indicative of the temperature of the humidified gas flow at the end of the transmission hose; and controlling a transmission hose heating element in response to the signal.

[0033] According to yet another exemplary embodiment, a humidifier of a respiratory device for delivering a humidified flow of breathable gas to a patient includes a humidifier chamber configured to store a supply of water for humidifying the flow of breathable gas, the humidifier chamber including a first heating element configured to heat the supply of water; an absolute humidity sensor that detects absolute humidity of ambient air and generates a signal indicative of the absolute humidity; and a controller configured to receive the signal generated by the absolute humidity sensor and control the first heating element to provide a predetermined absolute humidity to the flow of breathable gas. The predetermined absolute humidity corresponds to a predetermined temperature and a predetermined relative humidity.

[0034] According to some exemplary embodiments, the present invention provides the scheme described in the following items:

[0035] 1. A humidifier for a respiratory apparatus for delivering a humidified flow of breathable gas to a patient, the humidifier comprising:

[0036] a humidifier chamber configured to store a supply of water for humidifying the flow of breathable gas, the humidifier chamber comprising a first heating element configured to heat the supply of water;

[0037] a relative humidity sensor for detecting the relative humidity of ambient air and generating a signal indicative of the ambient relative humidity;

[0038] a first temperature sensor for detecting the temperature of ambient air and generating a signal indicative of the ambient temperature; and

[0039] A controller is configured to determine an absolute humidity of ambient air based on signals generated by the relative humidity sensor and the first temperature sensor and to control the first heating element to provide a predetermined relative humidity to the flow of breathable air.

[0040] 2. A humidifier according to clause 1, wherein the controller is further configured to control the first heating element to provide a flow of breathable gas at a predetermined temperature.

[0041] 3. A humidifier according to clause 2, wherein the controller determines a predetermined absolute humidity corresponding to a predetermined relative humidity and a predetermined temperature.

[0042] 4. A humidifier according to item 3, wherein the predetermined absolute humidity is approximately 11-44 mg / L.

[0043] 5. A humidifier according to item 2, wherein the predetermined temperature is approximately 15°C-37°C.

[0044] 6. A humidifier according to clause 2, wherein the predetermined temperature is approximately 26°C-28°C.

[0045] 7. A humidifier according to any one of clauses 1 to 6, wherein the predetermined relative humidity is approximately 50%-100%.

[0046] 8. A humidifier according to any one of clauses 1 to 6, wherein the predetermined relative humidity is approximately 70%-90%.

[0047] 9. A humidifier according to any of clauses 1 to 8, further comprising a user input configured to allow a patient or clinician to select the predetermined temperature and / or the predetermined relative humidity and / or the predetermined absolute humidity.

[0048] 10. A humidifier according to clause 9, wherein the user input comprises a control knob.

[0049] 11. The humidifier according to any one of items 1 to 10 further comprises a second temperature sensor, which detects the temperature of the supply water or the temperature of the first heating element and generates a signal indicating the temperature of the supply water or the temperature of the first heating element, respectively, wherein the controller is configured to control the first heating element with a feedback loop of the signal generated by the second temperature sensor.

[0050] 12. A humidifier according to clause 3, wherein the controller calculates an evaporation rate of the supplied water to provide the predetermined absolute humidity.

[0051] 13. A humidifier according to clause 12, wherein the evaporation rate is determined by multiplying the flow rate of breathable gas flow by the difference between the predetermined absolute humidity and the ambient absolute humidity.

[0052] 14. A humidifier according to any one of clauses 3 to 13, wherein the controller is configured according to the formula AHa=RHa·(K1-K2·Ta+K3·Ta 2 ) calculates the ambient absolute humidity, where AHa is the ambient absolute humidity, RHa is the ambient relative humidity and Ta is the ambient temperature, and according to the formula AHp = RHp (K1-K2 Tp + K3 Tp 2 ) calculates the predetermined absolute humidity, where AHp is the predetermined absolute humidity, RHp is the predetermined relative humidity, Tp is the predetermined temperature, and K1, K2 and K3 are coefficients.

[0053] 15. A humidifier according to clause 13 or 14, further comprising a flow sensor configured to determine the flow rate and generate a signal indicative of the flow rate.

[0054] 16. A humidifier according to clause 13 or 14, wherein the flow rate corresponds to a ventilation flow rate from a patient interface at a pressure of the breathable gas flow.

[0055] 17. A humidifier according to any one of clauses 1 to 16, wherein the controller is configured to control the first heating element to increase the temperature of the supply water as the flow rate increases, and to decrease the temperature of the supply water as the flow rate decreases.

[0056] 18. A humidifier according to any one of clauses 1 to 17, wherein the controller is configured to control the first heating element to reduce the temperature of the supply water as the ambient absolute humidity increases, and to increase the temperature of the supply water as the ambient absolute humidity decreases.

[0057] 19. A humidifier according to any one of clauses 1 to 18, wherein the controller is configured to control the first heating element to increase the temperature of the supply water as the predetermined temperature increases, and to decrease the temperature of the supply water as the predetermined temperature decreases.

[0058] 20. A humidifier according to any one of clauses 1 to 19, wherein a plurality of predetermined temperatures, a plurality of predetermined relative humidities and a plurality of corresponding predetermined absolute humidities are stored in a memory operatively associated with the controller.

[0059] 21. A humidifier for a respiratory apparatus for delivering a humidified flow of breathable gas to a patient, the humidifier comprising:

[0060] a humidifier chamber configured to store a supply of water for humidifying the flow of breathable gas, the humidifier chamber comprising a first heating element configured to heat the supply of water;

[0061] a relative humidity sensor for detecting the relative humidity of ambient air and generating a signal indicative of the ambient relative humidity;

[0062] a first temperature sensor for detecting the temperature of ambient air and generating a signal indicative of the ambient temperature; and

[0063] A controller is configured to determine an absolute humidity of the ambient air based on signals generated by the relative humidity sensor and the first temperature sensor and to control the first heating element to provide a predetermined absolute humidity, a predetermined temperature and / or a predetermined relative humidity to the flow of breathable air.

[0064] 22. A humidifier for a respiratory apparatus for delivering a humidified flow of breathable gas to a patient, the humidifier comprising:

[0065] a humidifier chamber configured to store a supply of water for humidifying the flow of breathable gas, the humidifier chamber comprising a first heating element configured to heat the supply of water;

[0066] an absolute humidity sensor that detects the absolute humidity of the humidified airflow and generates a signal indicative of the absolute humidity; and

[0067] A controller is configured to receive the signal from the absolute humidity sensor and control the first heating element to provide a predetermined absolute humidity, a predetermined temperature, and / or a predetermined relative humidity to the flow of breathable gas.

[0068] 23. A humidifier according to any one of items 1-22, further comprising a transmission hose and a second heating element configured to heat the humidified airflow within the transmission hose, the transmission hose comprising a first end configured to be connected to the humidifier outlet and a second end configured to be connected to the patient interface.

[0069] 24. The humidifier according to item 23 further comprises a third temperature sensor at the second end of the transmission hose, the third temperature sensor being configured to detect the temperature of the humidified air flow at the second end of the transmission hose and to generate a signal indicating the detected temperature.

[0070] 25. A humidifier according to clause 24, wherein the controller is configured to control the second heating element in response to a signal from the third temperature sensor to provide a humidified gas flow of a predetermined temperature and a predetermined relative humidity at the second end of the transfer hose.

[0071] 26. A humidifier according to any of clauses 23 to 25, wherein the predetermined absolute humidity corresponds to a predetermined temperature and a predetermined relative humidity at the second end of the transfer hose.

[0072] 27. A humidifier according to clause 26, wherein the predetermined temperature at the second end of the transfer hose is equal to or greater than the ambient air temperature.

[0073] 28. A humidifier according to any of clauses 24 to 27, wherein the controller is configured to determine a change in flow of the flow of breathable gas and to control the second heating element to adjust the predetermined temperature when the change in flow exceeds a predetermined change in flow.

[0074] 29. A humidifier according to clause 28, wherein the controller is configured to control the second heating element to increase the predetermined temperature when the change in the flow rate exceeds a predetermined decrease in the flow rate.

[0075] 30. A humidifier according to clause 29, wherein the controller is configured to control the second heating element to increase the predetermined temperature to above a saturation temperature.

[0076] 31. A humidifier according to clause 30, wherein the controller is configured to control the first heating element to reduce the temperature of the supply water when the change in the flow rate exceeds a predetermined decrease in the flow rate.

[0077] 32. A humidifier according to clause 31, wherein the controller is configured to control the second heating element to lower the predetermined temperature a predetermined time after the first heating element is controlled to lower the temperature of the supply water.

[0078] 33. A humidifier according to clause 28, wherein the controller is configured to control the second heating element to reduce the predetermined temperature when the change in the flow rate exceeds a predetermined increase in the flow rate.

[0079] 34. A humidifier according to any of clauses 1 to 33, wherein the controller is configured to control a duty cycle of the first heating element.

[0080] 35. A humidifier according to any of clauses 23 to 33, wherein the controller is configured to control a duty cycle of each of the first heating element and the second heating element.

[0081] 36. A respiratory apparatus for providing a humidified flow of breathable gas to a patient, comprising:

[0082] an airflow generator for generating a flow of breathable air; and

[0083] A humidifier according to any of items 1-35.

[0084] 37. A method of humidifying a flow of breathable gas provided to a patient, the method comprising:

[0085] determining the absolute humidity of the ambient air used to form the breathable airflow; and

[0086] The temperature of the supply of water humidifying the flow of breathable gas is controlled to provide a predetermined absolute humidity corresponding to a predetermined temperature and a predetermined relative humidity of the gas flow delivered to the patient.

[0087] 38. The method according to item 37, wherein the predetermined absolute humidity is approximately 11-44 mg / L, such as approximately 14 mg / L.

[0088] 39. The method according to item 37 or 38, wherein the predetermined temperature is about 15°C-37°C, such as about 26°C-28°C, preferably about 27°C.

[0089] 40. The method according to any of clauses 37-39, wherein the predetermined relative humidity is approximately 50%-100%, such as approximately 70%-90%, preferably approximately 80%.

[0090] 41. The method according to any of clauses 37-40, further comprising selecting a predetermined absolute humidity, a predetermined temperature and / or a predetermined relative humidity.

[0091] 42. The method according to any one of items 37 to 41, further comprising:

[0092] detecting a temperature of a water supply or detecting a temperature of a heating element configured to heat the water supply;

[0093] generating a signal indicative of the temperature of the supply water or the temperature of the heating element, respectively; and

[0094] The heating element is controlled within a feedback loop of the signal to control the temperature of the supply water.

[0095] 43. A method according to any one of items 37-42, wherein according to the formula AHa=RHa·(K1-K2·Ta+K3·Ta 2) Determine the ambient absolute humidity, where AHa is the ambient absolute humidity, RHa is the ambient relative humidity, Ta is the ambient temperature, and K1, K2 and K3 are coefficients.

[0096] 44. The method according to item 43, wherein according to the formula AHp=RHp·(K1-K2·Tp+K3·Tp 2 ) determines a predetermined absolute humidity, wherein AHp is the predetermined absolute humidity, RHp is the predetermined relative humidity and Tp is the predetermined temperature.

[0097] 45. A method according to any of clauses 37 to 44, wherein controlling the temperature of the supply water comprises determining an evaporation rate of the supply water.

[0098] 46. ​​A method according to clause 45, wherein the evaporation rate is determined by multiplying the flow rate of breathable gas flow by the difference between the predetermined absolute humidity and the ambient absolute humidity.

[0099] 47. The method according to item 46 further comprises detecting the flow rate of the breathable gas flow.

[0100] 48. A method according to item 46, wherein the flow rate corresponds to the ventilation flow rate of a patient interface connected to the transmission hose at the pressure of the breathable gas flow.

[0101] 49. The method according to any of clauses 46-48, wherein controlling the temperature of the supply water comprises increasing the temperature of the supply water as the flow rate increases, and decreasing the temperature of the supply water as the flow rate decreases.

[0102] 50. The method according to any one of clauses 37 to 49, wherein controlling the temperature of the supply water comprises decreasing the temperature of the supply water as the ambient absolute humidity increases, and increasing the temperature of the supply water as the ambient absolute humidity decreases.

[0103] 51. The method according to any one of clauses 37 to 49, wherein controlling the temperature of the supply water comprises increasing the temperature of the supply water as the predetermined temperature increases, and decreasing the temperature of the supply water as the predetermined temperature decreases.

[0104] 52. The method according to any one of items 37 to 51, further comprising:

[0105] detecting a temperature of a humidified gas flow at one end of a delivery hose configured to be connected to a patient interface;

[0106] generating a signal indicative of a temperature of the humidified gas stream at one end of the transfer hose; and

[0107] The transfer hose heating element is controlled in response to the signal to provide a humidified gas flow at a predetermined temperature at the second end of the transfer hose.

[0108] 53. The method according to clause 52, wherein the predetermined temperature at the end of the transfer hose is equal to or greater than the ambient air temperature.

[0109] 54. The method according to item 52 or 53, further comprising:

[0110] determining a change in the flow rate of breathable gas; and

[0111] The transfer hose heating element is controlled to adjust the predetermined temperature when the change in flow rate exceeds a predetermined change in flow rate.

[0112] 55. A method according to item 54, wherein when the change in flow rate exceeds a predetermined decrease in flow rate, the transfer hose heating element is controlled to increase a predetermined temperature.

[0113] 56. A method according to item 55, wherein the transfer hose heating element is controlled to increase the predetermined temperature to above the saturation temperature.

[0114] 57. The method according to item 56, further comprising:

[0115] The temperature of the supply water is reduced when the change in the flow rate exceeds a predetermined decrease in the flow rate.

[0116] 58. The method according to item 57, further comprising:

[0117] A predetermined time after lowering the temperature of the supply water, the transfer hose heating element is controlled to lower the predetermined temperature.

[0118] 59. The method according to item 54, further comprising:

[0119] When the change in the flow rate exceeds a predetermined increase in the flow rate, the transfer hose heating element is controlled to reduce the predetermined temperature.

[0120] 60. A method according to clause 37, wherein determining the absolute humidity of the ambient air comprises detecting the absolute humidity using a sensor.

[0121] 61. The method according to any one of items 42 to 60, further comprising:

[0122] A duty cycle of the heating element is controlled.

[0123] 62. The method according to any one of items 52 to 60, further comprising:

[0124] The duty cycle of the heating element and the transfer hose heating element is controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0125] Exemplary embodiments will now be described with reference to the accompanying drawings, in which:

[0126] Figure 1 schematically illustrates an airflow generator and a humidifier according to an exemplary embodiment;

[0127] Figure 2 Schematically illustrates Figure 1 The airflow generator in the

[0128] Figure 3 Schematically illustrates Figure 1 Humidifier in;

[0129] Figure 4 schematically illustrates an air delivery hose and a patient interface according to an exemplary embodiment;

[0130] Figure 5 Schematically illustrates the opposite end of the air delivery hose. Figure 4 an air delivery hose in the apparatus, and an electronic connector connectable thereto;

[0131] Figure 6 schematically illustrates a breathing apparatus according to an exemplary embodiment;

[0132] Figure 7 Schematically illustrates the relationship between the absolute humidity of ambient air and the temperature of ambient air in the case of water vapor saturation;

[0133] Figure 8 schematically illustrates the relationship between the water temperature in a humidifier barrel and the ambient air temperature when the ambient absolute humidity does not change according to one example;

[0134] Fig. 9 schematically illustrates the relationship between the water temperature in the humidifier barrel and the temperature of the airflow delivered to the patient interface and the ambient temperature when the absolute humidity of the environment does not change according to a comparative example;

[0135] Fig.10 schematically illustrates changes in water temperature in response to changes in the temperature of a transport gas according to another example;

[0136] Fig.11 schematically illustrates the change in water temperature in response to a change in ambient humidity without a change in ambient temperature according to another example;

[0137] Fig.12schematically illustrates changes in water temperature in response to changes in average gas flow through a humidifier according to one example;

[0138] Fig.13 schematically illustrates a humidifier according to another exemplary embodiment;

[0139] Fig.14 schematically illustrates an exemplary arrangement for compensating a humidifier by controlling a heating element of the humidifier in response to changes in ambient and / or average flow during use of a respiratory apparatus according to an exemplary embodiment;

[0140] Fig.15 schematically illustrates the control of a breathing apparatus according to an exemplary embodiment;

[0141] Fig.16 schematically illustrates control of a breathing apparatus according to another exemplary embodiment;

[0142] Fig.17 schematically illustrates control of a breathing apparatus according to another exemplary embodiment; and

[0143] Fig.18 The control of a breathing apparatus according to a further exemplary embodiment is schematically illustrated. DETAILED DESCRIPTION

[0144] Humidification theory

[0145] Humidity represents the amount of water vapor in the air. Humidity is usually measured in two ways: absolute humidity (AH) and relative humidity (RH). Absolute humidity is the actual amount of water recorded based on weight per volume. Absolute humidity is usually measured in grams per cubic meter (g / cm 3 ) or milligrams per liter (mg / L).

[0146] Relative humidity is the actual water vapor content of a gas relative to its capacity to carry water at any given temperature. The ability of air to carry water vapor increases as the air temperature increases. For air with a constant absolute humidity, relative humidity will decrease as the air temperature increases. Conversely, for water-saturated air (i.e. 100% RH), if the temperature drops, excess water will condense from the air.

[0147] The air that people breathe is heated and humidified by the airway to a temperature of 37°C and 100% RH. At this temperature, the absolute humidity is about 44 mg / L.

[0148] Humidification for CPAP

[0149] ISO8185 requires that medical humidifiers provide a minimum of 10 mg / L AH, and a minimum of 33 mg / L when the patient's upper airway is bypassed. These minimum requirements are calculated when dry air is input. These minimum requirements are also only for short-term use. These minimum requirements are generally not enough to minimize the symptoms of nasal and upper airway dryness. Under normal operating conditions, the patient or clinician should be able to set the temperature of the air delivered from the environment to the patient interface to approximately 37°C. If the respiratory device is not provided with an alarm system or indicator, according to parts 51.61-51.8 of ISO8185, the temperature of the air delivered to the patient interface should not exceed 41°C under normal and single fault conditions.

[0150] For CPAP, the upper limit level of 44 mg / L may be inappropriate because the patient's upper airway is not bypassed. On the other hand, the lower limit level of 10 mg / L may be too low for CPAP, especially for patients with oral leaks.

[0151] Although no studies have been conducted to determine the minimum level of humidity required for CPAP, Wiest et al. Sleep , Vol. 24, No. 4, pp. 435-440, 2001) found that for North American and European patients, an average absolute humidity of 10 mg / L was too low when CPAP therapy was performed without a humidifier system. This study tested two humidifiers, both of which provided at least 23 mg / L absolute humidity. Wiest et al. concluded that levels exceeding ISO 8185's 10 mg / L AH are required for CPAP, but may be lower than the 23 mg / L AH used in the study. Applicants have determined that an absolute humidity of approximately 20-30 mg / L provides adequate patient comfort.

[0152] Humidifiers and air flow generators

[0153] refer to Figure 1 The breathing device 1 may include an airflow generator 2 and a humidifier 4, which are configured to be connected to each other. Such an airflow generator and humidifier combination is disclosed, for example, in WO 2004 / 112873 A1, the entire contents of which are incorporated herein by reference. The humidifier may also be a humidifier as disclosed in U.S. Pat. No. 6,935,337, the entire contents of which are incorporated herein by reference.

[0154] The airflow generator 2 may include an ON / OFF switch 6 and a display 8, such as an LCD, to display the operating status of the airflow generator and other parameters described in detail below. The airflow generator 2 may also include a button 14 for controlling the operation of the airflow generator 2, such as to select various programs stored in the memory of a controller configured to control the operation of the airflow generator. The button 14 may also be used to set various parameters, such as the flow rate of the airflow generator 2.

[0155] The humidifier 4 may include a control knob 10 for controlling power to a heating element (not shown) and setting a temperature at the patient interface, as will be described in detail below. Alternatively, the controls for the humidifier 4 may be combined with the flow generator 2. The humidifier 4 may also include an outlet 12 configured to be connected to an air delivery hose or conduit for delivering a humidified flow of breathable gas to the patient via the patient interface.

[0156] refer to Figure 2 , the airflow generator 2 can be formed of, for example, a hard plastic material molded into two parts of a top shell 16 and a bottom shell 18. The top shell 16 and the bottom shell 18 define an engagement surface 20 of the airflow generator 2, and the engagement surface 20 is configured to engage the humidifier 4 when the humidifier 4 is connected to the airflow generator 2. The engagement surface 20 includes a pair of grooves 22 configured to engage with corresponding tongues (not shown) provided on the humidifier 4, and the airflow generator 2 and the humidifier 4 are connected together by means of the engagement of the above-mentioned grooves and tongues. An electrical connector 24 can be provided for providing power to the humidifier 4 when the airflow generator 2 is connected to the humidifier 4. The airflow generator 2 can further include an outlet 26, which is configured to transmit the breathable gas flow to the humidifier 4 when the airflow generator 2 is connected to the humidifier 4.

[0157] like Figure 3 As shown, the humidifier 4 may include a hinged lid 28. The humidifier 4 may also include a barrel, as disclosed in U.S. Patent Application Publication 2008 / 0302361A1, the entire contents of which are incorporated herein by reference. The humidifier 4 may also include a heating element controllable by the control knob 10. Such heating elements are disclosed, for example, in WO 2008 / 148154A1, the entire contents of which are incorporated herein by reference. The humidifier may also be heated, as disclosed in WO 2004 / 112873A1.

[0158] Although the airflow generator and humidifier have been disclosed as separate devices that can be connected to form an integral device, it should be recognized that the airflow generator and humidifier can be provided as separate components that cannot be connected together to present a unified appearance, as disclosed in U.S. Patent 6,338,473, the entire contents of which are incorporated herein by reference.

[0159] Air transfer hose

[0160] refer to Figure 4 , an air delivery conduit or hose 30 is connected to a patient interface 32, such as a mask, to deliver a humidified flow of breathable gas from the humidifier outlet to the patient. It should be appreciated that the patient interface 32 may be a nasal mask, a full face mask, a nasal cannula, nasal pillows or nasal prongs, or a combination of a cushion and nasal prongs or nasal pillows configured to surround the patient's mouth.

[0161] The air delivery hose 30 may be a heating hose, as disclosed in U.S. Patent Application Publication 2008 / 0105257A1, the entire contents of which are incorporated herein by reference. The air delivery hose 30 may be formed by a tube 30a made of, for example, a thermoplastic elastomer (TPE) and a spiral rib 30b made of, for example, very low density polyethylene. The wires 30c, 30d, 30e may be supported by the spiral rib 30b so as to be in contact with the outer surface of the tube 30a. The wires 30c, 30d, 30e may be used to heat the tube 30a and to send or receive signals to or from the controller in the airflow generator 2 and / or the humidifier 4. It should be appreciated that the air delivery hose 30 may include two wires, and the signal may be multiplexed through the two wires. It should also be appreciated that the air delivery hose 30 may include a heating element, for example in the form of a heating strip or wire, as disclosed in WO2009 / 015410A1, the entire contents of which are incorporated herein by reference.

[0162] The air delivery hose 30 includes a connector or cuff 34 configured to connect the air delivery hose 30 to the patient interface 32. The patient interface cuff 34 may include a temperature sensor, such as a thermistor as disclosed in U.S. Patent Application Publication 2008 / 0105257A1, the entire contents of which are incorporated herein by reference, to detect the temperature of the humidified flow of breathable gas delivered to the patient interface 32.

[0163] refer to Figure 5 , the air delivery hose 30 includes a connector or sleeve 36 configured to be connected to the outlet 12 of the humidifier. The humidifier sleeve 36 includes an end 36a configured to be connected to the outlet 12, and a grip 36b to provide a better grip for connecting and disconnecting the air delivery hose 30 from the outlet 12.

[0164] The humidifier cuff 36 may be connected to the controller of the humidifier 4 via an electrical connection 38. The electrical connection 38 provides power to the wires 30c, 30d, 30e of the air delivery hose 30 to heat the air delivery hose 30 along its length from the humidifier 4 to the patient interface 32.

[0165] Respiratory system

[0166] refer to Figure 6The breathing system according to an exemplary embodiment of the present invention may include an airflow generator 2, a humidifier 4 and an air transmission hose 30. A patient interface 32 may be connected to the air transmission hose 30.

[0167] The airflow generator 2 may include a controller 40. The airflow generator controller 40 may include, for example, a programmable logic controller or an application specific integrated circuit (ASIC). The airflow generator 2 may further include a flow sensor 42 to detect the volume (e.g., liters per minute) of the breathable gas flow generated by the airflow generator 2 and delivered to the inlet of the humidifier 4. It should be appreciated that the flow rate may be estimated from the motor speed of the airflow generator rather than being directly provided by the flow sensor.

[0168] The humidifier 4 may include a controller 44. The humidifier controller 44 may be, for example, a programmable logic controller or an ASIC. It should be appreciated that in the case where the airflow generator and the humidifier can be connected together to form an integral device, the airflow generator controller and the humidifier controller may be a single controller configured to control both devices. Alternatively, the airflow generator controller 40 may include all of the functionality of the controller 44, and when the humidifier is connected, the functionality related to humidification may be obtained from the controller 40.

[0169] The humidifier 4 further comprises a heating element 46 configured to heat the supply water stored in the humidifier 4. The heating element 46 may be, for example, a plate disposed below the humidifier barrel. It should also be appreciated that the heating element 46 may comprise a heating element as disclosed in WO2009 / 015410 A1, the entire contents of which are incorporated herein by reference. A temperature sensor 48 may be provided to detect the temperature of the water heated by the heating element 46. It should be appreciated that the water temperature may be determined by detecting or measuring the temperature of the heating element 46, for example by directly detecting the temperature of the heating element using a temperature sensor.

[0170] The humidifier 4 may further include a temperature sensor 50 for detecting the temperature of the ambient air and a relative humidity sensor 52 for detecting the relative humidity of the ambient air. The humidifier may also optionally include an ambient pressure sensor 53. It should be appreciated that the sensors 50, 52, 53 need not be provided on the humidifier, but may be provided separately, for example from a location that includes the sensors and is connectable to the humidifier 4. It should also be appreciated that the sensors 50, 52, 53 may be provided to the airflow generator 2 instead of the humidifier 4, or that the ambient temperature, relative humidity and ambient pressure may be provided to the airflow generator 2 from a location other than the humidifier 4. It should further be appreciated that the flow sensor 42 may be provided to the humidifier 4 instead of the airflow generator 2, or that the flow sensor 42 may be provided to the humidifier 4 in addition to the airflow generator 2. It should still further be appreciated that the ambient temperature, relative humidity and ambient pressure sensors 50, 52, 53 may be replaced by an absolute humidity sensor configured to detect the absolute humidity of the humidified airflow, for example at the outlet of the humidifier, and to generate a signal indicative of the absolute humidity.

[0171] The air delivery hose 30 includes a temperature sensor 54, such as a thermistor, within the patient interface cuff 34. It should be appreciated that the temperature sensor 54 may be disposed within the patient interface 32 rather than within the cuff 34. The temperature detected by the temperature sensor 54 may be transmitted as a signal through the air delivery hose 30 to the humidifier controller 44.

[0172] Figure 6 The system may be configured to allow a patient to select and set the temperature of the humidified flow of breathable gas delivered to the patient interface 32. For example, the system may be configured to allow a user to use the control knob 10 on the humidifier 4 or the control button 14 of the airflow generator 2 to set the temperature of the humidified flow of gas at the patient interface 32. For example, the system may be configured to allow a patient or clinician to select a temperature of the humidified flow of gas at the patient interface in a range of approximately 10°C-37°C, such as approximately 26°C-28°C. The system may be configured to prevent a patient or clinician from selecting and / or setting a temperature value below the ambient temperature. The ambient temperature may be displayed on the display 8 of the airflow generator, or a message may be displayed when the selected temperature is below the ambient temperature to remind the patient or clinician that the temperature is invalid. Alternatively, the system may allow selection of an automatic or default temperature setting, such as 27°C.

[0173] Figure 6The system may also be configured to provide an absolute humidity of, for example, between about 10-44 mg / L to the patient interface 32. The relative humidity of the airflow of the patient interface may be controlled to be less than 100% RH, such as about 70-90% RH, such as about 80% RH as a default value. Keeping the relative humidity of the airflow in the air delivery hose 30 below 100% RH helps prevent rain out in the air delivery hose between the humidifier 4 and the patient interface 32. The system may also be configured to provide an automatic or default relative humidity, such as 80%, at the patient interface 32. The system may also be configured to allow the patient or clinician to set the relative humidity of the airflow of the patient interface 32. Although the relative humidity of the airflow of the patient interface 32 can be directly detected by a humidity sensor disposed in the patient interface, because the humidity sensor is prone to misreading or failure due to condensation, a more reliable method may be to detect the relative humidity and temperature of the ambient air or the incoming airflow and calculate the absolute humidity.

[0174] Figure 6 The system can compensate for a wide range of ambient temperature and humidity variations. The temperature of the airflow at the patient interface 32 can be directly detected, for example, by the temperature sensor 54. The relative humidity of the airflow at the patient interface can be calculated based on the following data: 1) the moisture content of the ambient air (from its ambient temperature and relative humidity); 2) the temperature of the water in the humidifier barrel (e.g., detected by the temperature sensor 48); and / or 3) the flow rate through the humidifier barrel (e.g., detected by the flow sensor 42 of the airflow generator). It should be appreciated that the relative humidity can also be directly detected, for example, by a relative humidity sensor at the end of the tube 30 or in the patient interface 32.

[0175] The temperature of the airflow to the patient interface 32 can be controlled by controlling the power supplied to the air delivery hose 30, such as by controlling the current of the wires of the hose 30. The relative humidity of the airflow to the patient interface 32 can be controlled by the temperature of the water in the humidifier barrel, with the ambient temperature, ambient relative humidity and flow rate as input parameters.

[0176] Humidity Control

[0177] refer to Figure 7 , the saturated absolute humidity of the ambient air can be calculated from the humidity properties of water vapor. See, for example, Y. Changel, McGraw-Hill Heat transfer ( Heat Transfer , Y. Cengel, McGraw-Hill), 1998 (pages 958-59, Table A9). Or see, for example, IAPWS, a formula for calculating the thermodynamic properties of industrial water and steam, was published in 1997 ( Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam), The International Association for the Properties of Water and Steam, September 1997, Erlangen, Germany. Figure 7 As shown, absolute humidity is expressed in mg / L, which is the mass of water vapor per unit volume of air, where the conditions are ambient temperature and standard (sea level) pressure, or ATPS. The absolute humidity of ambient air, AHa, can be defined by any equation or lookup table corresponding to the humidity characteristics of water vapor. For example, the following quadratic equation:

[0178] AHa=RHa·(K1-K2·Ta+K3·Ta 2 ) (1),

[0179] Where RHa is the relative humidity of the ambient air, Ta is the temperature of the ambient air, and K1, K2, and K3 are coefficients. For example, the coefficients K1, K2, and K3 can be determined empirically, such as by curve fitting to obtain data. For example, K1 can be equal to 7.264, K2 can be equal to 0.09276, and K3 can be equal to 0.02931.

[0180] The target temperature Tm of the airflow at the mask and the target relative humidity RHm at the mask also define the absolute humidity AHm at the mask, as defined by the following equation:

[0181] AHm=RHm·(K1-K2·Tm+K3·Tm 2 ) (2),

[0182] Among them, for example, K1 = 7.264, K2 = 0.09276, and K3 = 0.02931.

[0183] The difference ΔAH between the ambient absolute humidity AHa determined by equation (1) and the absolute humidity AHm at the mask determined by equation (2) is equal to the absolute humidity added to the airflow by the humidifier 4. Of course, if AHm < AHa, no humidification is required. Given a flow rate F (L / min) through the humidifier barrel, the evaporation rate E of water can be determined using a derived equation describing the humidifier response. For example, in one embodiment, the evaporation rate can be determined from the change in flow rate and absolute humidity using the following equation:

[0184] E(g / hr)=ΔAH(mg / L)·F(L / min)·(60min / hr)·0.001g / mg (3).

[0185] As an example, for using Figure 6CPAP therapy performed by the system in the embodiment of the present invention supplies a pressure of 10 cm H2O to treat patients with OSA. At 10 cm H2O, the flow rate F is approximately 35 L / min, which is equal to the mask ventilation flow rate at a predetermined pressure. When the ambient temperature Ta is 20°C and the ambient relative humidity RHa is 50%, according to equation (1), the absolute humidity AHa of the air entering the humidifier is equal to 0.5·17.3=10.4 mg / L. Assuming that the patient selects a mask temperature Tm of 25°C and the relative humidity is selected or automatically set to 90%, according to equation (2), the absolute humidity AHm at the mask is equal to 0.9·23.3=20.9 mg / L. The absolute humidity ΔAH added by the humidifier is equal to 20.9-10.4=10.5 mg / L. According to equation (3), the evaporation rate E of the humidifier is therefore determined to be E = (10.5 mg / L)·(35 L / min)·(60 min / hr)·(0.001 g / mg) = 22 g / hr.

[0186] The rate of evaporation of water is related to its vapor pressure, which is driven by the temperature of the liquid water. In general, the saturated vapor pressure nearly doubles for every 10°C increase in water temperature. See, e.g., Y. Changel, McGraw-Hill Heat transfer , 1998 (pp. 958-59, Table A9). Or see, for example, 1997 Published formulas for calculating the thermodynamic properties of industrial water and steam IAPWS , International Association for the Properties of Water and Water Vapour, September 1997, Erlangen, Germany. In addition, the water content of the ambient air, i.e. the vapour pressure of the water already present in the ambient air, determined by the ambient air temperature and the ambient air relative humidity, reduces the evaporation rate. The atmospheric pressure of the ambient air also affects the evaporation rate, but not as much as the increase in water temperature and the ambient air water content. The lower the atmospheric pressure, the faster the water vapour evaporates, e.g. the higher the altitude, the faster the water vapour evaporates.

[0187] The water temperature in the humidifier barrel can be closed-loop controlled. Alternatively, the temperature of the underwater heating element can also be closed-loop controlled. Other parameters can be used for the set point of the closed-loop control. For example, the evaporation rate E is limited by the saturation of water vapor in the humidifier barrel. The water vapor saturation in the barrel depends on the temperature of the air flowing into the humidifier from the airflow generator. The airflow generator can increase the temperature of the air flowing into the humidifier, for example, by heat generated from the airflow generator motor.

[0188] The theoretical relationship between evaporation rate and water temperature also assumes that the water vapor in the humidifier barrel is efficiently removed from the barrel. However, the airflow pattern through the barrel may bypass some of the container that produces the water vapor. In addition, the agitation effect of the airflow can evenly transfer heat through the water in the barrel.

[0189] The theoretical relationship also assumes that the evaporation rate is largely unaffected by the temperature of the air in the bucket until saturation is reached. In practice, for example, cooling the water surface by lowering the ambient air temperature can reduce the evaporation rate. There are temperature gradients from the heated bucket through the water and the inner wall of the bucket to the outside of the humidifier. These temperature gradients may cause inconsistencies between the detected temperature and the actual water surface temperature. Even without using a temperature sensor, temperature gradients may still cause inconsistencies between the water body temperature and the water surface temperature. The evaporation rate is related to the temperature of the water surface.

[0190] Example 1 - Controlling the temperature of the mask to adjust to changes in ambient temperature

[0191] In this example, Figure 6 The system in is set to deliver saturated air to the mask at 30°C. The patient or clinician can set the temperature using the control button 14 of the flow generator 2 and / or the control knob 10 of the humidifier 4. For example, in the patient's bedroom when the patient is sleeping, the absolute humidity of the ambient air is 10 mg / L, which does not change with the temperature of the ambient air. As shown in Table 1, the water temperature in the humidifier barrel is adjusted to obtain 100% RH air at the patient interface.

[0192]

[0193] Table 1

[0194] like Figure 8 As shown, the result of closed loop control is that the water temperature in the bucket must be controlled at approximately the same set point regardless of the ambient temperature of the room air. Therefore, if the temperature at the mask is adjusted, the system does not need to respond to changes in the temperature of the ambient air.

[0195] Comparative Example 1 - Adjusting for changes in ambient temperature without controlling mask temperature

[0196] In this comparative example, the air temperature delivered to the patient interface is not under a feedback control loop. Instead, the system is controlled so that the water temperature in the humidifier barrel is controlled to track the ambient air temperature, as shown in Tables 2 and Fig. 9 shown.

[0197]

[0198]

[0199] Table 2

[0200] In this comparative example, although the relative humidity of the air delivered to the patient interface is 100% RH for all temperatures, the absolute humidity of the air delivered to the patient interface varies greatly, for example, from 12.5 mg / L to 30.7 mg / L. The temperature of the airflow delivered to the patient interface also varies according to the ambient air temperature. Therefore, the patient cannot increase the temperature of the airflow delivered to the patient interface.

[0201] Example 2 - Adjustment of set temperature changes at the patient interface

[0202] Refer to Table 3 and Fig.10 , in this example, Figure 6 The system is controlled to deliver saturated air and the temperature of the patient interface is changed.

[0203]

[0204]

[0205] Table 3

[0206] Assume that the ambient air is 22.5°C, the absolute humidity is 10 mg / L, and the relative humidity is 50%. Assume that the ambient air conditions do not change. Adjust the water temperature in the humidifier barrel to obtain 100% RH at the patient interface, as shown in Table 3. As the required temperature at the patient interface increases, the water temperature in the humidifier barrel is also increased to maintain the saturation of the delivered air. Fig.10 As shown, the relationship between the water temperature in the humidifier barrel and the temperature of the delivered air is approximately linear, for example, for every 1°C increase in the temperature of the air delivered to the patient interface, the water temperature increases by approximately 1.55°C. The temperature at the mask can be automatically and independently controlled by controlling the power applied to the heating tube.

[0207] In this example, the temperature of the air delivered to the patient interface can be selected by the patient or clinician using, for example, the control button 14 of the airflow generator 2. The patient can select an operating mode that allows the air temperature at the patient interface to be adjusted. The heating element of the humidifier is then automatically controlled to increase the water temperature in the humidifier barrel as the desired air temperature at the patient interface increases, and correspondingly decrease the water temperature as the desired air temperature decreases.

[0208] Example 3 - Adjustment to changes in ambient humidity

[0209] Figure 6 The system can also be configured to adjust to changes in ambient humidity. For example, signals from sensors 50, 52 can be provided to controller 40 and / or 44 to periodically or continuously calculate the absolute humidity of the ambient air. Fig.11As shown, the temperature of the ambient air remains relatively constant, for example 22.5°C, but the absolute humidity varies throughout the patient's sleep cycle.

[0210]

[0211]

[0212] Table 4

[0213] The water temperature in the humidifier barrel is adjusted to obtain 100% RH at the patient interface. The temperature at the patient interface is kept constant, for example, 30°C. Therefore, the water temperature in the humidifier barrel decreases as the absolute humidity and relative humidity of the ambient air increase. The system allows the temperature of the saturated air delivered to the patient interface to remain relatively constant through this control method, as shown in Table 4.

[0214] Example 4 - Adjustment for air flow changes

[0215] Refer to Table 5 and Fig.12 , the ambient temperature and relative humidity as well as the temperature of the air delivered to the patient interface are constant.

[0216]

[0217]

[0218] Table 5

[0219] The flow through the humidifier can be, for example, via the ResMed The flow rate can also be adjusted, for example, in response to a leak at the patient interface. Fig.12 As shown, the water temperature in the humidifier barrel increases as the air flow increases to maintain saturation at the patient interface.

[0220] The breathing system can be controlled according to each or a combination of Examples 1-4. Tables 1 and 3-5 and Figure 8 and 10 The data provided by -12 can be stored in a memory of, for example, controllers 40 and / or 44. Controllers 40, 44 can be programmed to access the data in the stored information. Controllers 40, 44 can also be programmed to interpolate and / or extrapolate the data in the stored information. The set point of the heating element that provides the appropriate evaporation rate for each combination of ambient temperature and humidity, flow rate, and predetermined output humidity can be determined empirically to represent the design and then introduced into the controller, for example, stored in memory as a table or stored as a set of equations.

[0221] Although the relative humidity of air delivered to the patient interface is described as 100% in each of Examples 1-4, it should be appreciated that the relative humidity of air delivered to the patient interface can be approximately 50%-100%, for example approximately 70%-90%, or as another example approximately 80%, or other value selected by the patient or clinician.

[0222] Humidifier control

[0223] The humidifier 4 may provide a user selectable setting that will provide automatic delivery of a predetermined moisture content at the mask 32. An example value for the moisture content of the air delivered is determined to take into account conditions that may cause undesirable condensation in the tube 30. For a user with a normal upper airway, the desired physiological result is to condition the air to approximately normal nasal inhalation conditions. For example, ambient air may be 20°C and 25% RH (4 mg / L AH). The air may be heated and humidified to conditions equivalent to approximately 20°C and 80% RH (14 mg / L AH). Therefore, a moisture content of 14 mg / L corresponding to an absolute humidity of 80% RH at 20°C may be selected as an example value. The humidifier will be set to have an output of 14 mg / L. The difference of 10 mg / L will be added by the humidifier. It should be appreciated that while this value may be selected as an example value and the humidifier may be configured to include a user setting that automatically provides this value, the example value may be determined or modified based on clinical recommendations, and the humidifier may be configured, or reconfigured, to include a user setting that automatically provides a clinically determined moisture content. For example, the patient or clinician may select an absolute humidity within the range of approximately 10 mg / L-25 mg / L, such as 20 mg / L, which generally corresponds to a relative humidity between 70%-80% at a temperature of approximately 27°C-28°C.

[0224] In the case of a breathing apparatus with a heated tube, the actual temperature of the air delivered in a CPAP system can be above room temperature, typically about 29°C. Therefore, the RH value at the nose will be 50% lower than the same absolute humidity value. In the case of a breathing apparatus without a heated tube, the humidified air in the tube is cooled to one or two degrees above the ambient temperature. Without a heated tube, the air will be delivered at about 22°C and 70% RH (14 mg / L AH).

[0225] At the optimum setting, e.g. 10 mg / L, condensation in the breathing tube will not occur unless the room temperature drops enough to cause the delivered air temperature to drop below its dew point (about 16°C for 29°C air typically delivered to a mask with a CPAP device operating in a 22°C environment). The continued drop in room temperature causes the delivered air temperature to drop as well, and the heater temperature is then automatically reduced to reduce the delivered moisture content below the optimum level, thereby avoiding condensation, but still achieving as close to the optimum level as possible.

[0226] refer to Fig.13 According to another exemplary embodiment of the present invention, a humidifier 4 includes a control knob 10, and the control knob 10 includes a setting indicator 10a. The humidifier 4 includes an indicator 11 indicating a plurality of setting values. The indicator 11a may represent an automatic setting, which provides a default water content. For example, Fig.13 As shown, the automatic setting indicator 11a may include, for example, ▼. It should be appreciated that any other indicator may be used, for example, the indicator 11a may include the text "optimal" or "automatic". The remaining indicators 11 may include numbers, such as 1-4 and 6-9, which allow the user to increase and decrease the humidity transmitted. The indicator may also be configured to display values ​​of relative humidity or absolute humidity and temperature, such as percentage RH. In order to select the default setting, the user aligns the setting indicator 10a of the control knob 10 with the automatic setting indicator 11a. In order to adjust the humidity setting, the user aligns the setting indicator 10a with any other indicator 11, or any position between any other indicators 11. For example, in order to reduce the humidity setting, the user may align the setting indicator 10a with any one of the numbers 1-4, or any setting therebetween. Similarly, in order to increase the humidity setting, the user may align the setting indicator 10a with any one of the numbers 6-9, or any setting therebetween. It should also be appreciated that the controller may not be a knob, for example, the controller may include a display such as an LCD to display the setting, and one or more buttons to allow the setting to be selected or the displayed setting to be changed.

[0227] like Fig.14 As shown, when the automatic default moisture content is selected, i.e., setting indicator 10a to indicator 11a, humidifier 4 can be controlled so that heating element 46 of humidifier 4 is continuously adjusted to maintain the moisture content of the breathable gas flow at a predetermined default level, such as 14 mg / L. As discussed in more detail below, heating element 46 is continuously adjusted to maintain the moisture content of the gas flow as close to the default level as possible while still preventing condensation or rain-out in tube 30.

[0228] During the user's sleep, in response to changes in indoor conditions, such as ambient temperature, ambient relative humidity, and / or ambient pressure, and / or in response to changes in airflow, the heating element 46 is controlled to maintain a default moisture content, such as 14 mg / L. For example, at the beginning of the patient's sleep (state 1), the indoor conditions may be a first temperature, a first relative humidity, and a first pressure. The airflow generator can generate a first airflow Q1 at the beginning of the patient's sleep. When the patient selects automatic setting by aligning the setting indicator 10a with the indicator 11a, the heating element 46 of the humidifier 4 is controlled to provide a default moisture content, such as 14 mg / L.

[0229] Although State 1 is described above as corresponding to the onset of patient sleep, it will be appreciated that State 1 may correspond to the time from start-up of the respiratory system, such as a warm-up time to account for the effect of delivered air temperature above ambient temperature.

[0230] During the patient's sleep process, the indoor state, including the ambient temperature, ambient relative humidity, and / or pressure, may change to a second state (state 2). The airflow Q2 generated by the airflow generator may also change during the patient's sleep process. The heating element 46 of the humidifier 4 is controlled so that in state 2, no matter how the indoor state changes, the water content of the airflow is a default value, for example, 14 mg / L.

[0231] Likewise, if the patient selects a different setting at startup (state 1), for example by aligning the setting indicator 10a to indicator "9" (increase moisture content from the default) or indicator "1" (decrease moisture content from the default), the heating element 46 is controlled so that the moisture content delivered to the mask in state 2 is the same as the moisture content delivered to the mask in state 1. The entire range of moisture content settings centered around the default setting is continuously and automatically readjusted in response to monitored values ​​of ambient temperature, ambient relative humidity, ambient pressure, and delivered airflow so that the selected setting is always adjusted to deliver the selected moisture content.

[0232] First Embodiment of Humidity Control

[0233] refer to Fig.15 , illustrates a control system and method for a respiratory device. At S1, a temperature Tm of an airflow delivered to a mask is determined. At S2, a relative humidity RHm of the airflow delivered to the mask is determined. It should be appreciated that the user can set the temperature Tm and the relative humidity RHm by, for example, using a button 14 on the airflow generator 2. Alternatively, the user can select the moisture content, i.e., the absolute humidity of the airflow delivered to the mask, by adjusting the control knob 10 of the humidifier. For example, the user can align the setting indicator 10a with the default setting indicator 11a. The default moisture content can be a nominal moisture content, such as 14 mg / L, or a clinically determined moisture content. The user can also select other non-default moisture content values ​​by aligning the setting indicator 10a with another indicator 11. In the case where the humidifier is integrally connected to the airflow generator, the respiratory device can be configured to allow the user to select the moisture content using the button 14 on the airflow generator 2 or the control knob 10 of the humidifier 4. In the event that the user selects a hydration level, the temperature Tm and relative humidity RHm transmitted to the mask correspond to the selected hydration level setting.

[0234] The heating element of the air delivery tube 30 is controlled to provide a predetermined temperature Tm to the air flow delivered to the mask. The temperature sensor 54 at the end of the air delivery hose 30 detects the actual temperature of the air flow at the end of the air delivery hose 30. The difference ΔTm between the predetermined temperature Tm and the detected temperature is determined by the controller 40 and / or 44 in S11, and the controller 40 and / or 44 adjusts the power supplied to the heating element of the air delivery tube 30 until the difference between the predetermined temperature and the detected temperature is substantially zero.

[0235] At S3, the temperature sensed by sensor 54 and the predetermined relative humidity RHm delivered to the mask are input to equation (2) to provide the absolute humidity AHm, i.e., the moisture content, to the mask. At S5, the ambient temperature Ta from sensor 50 and the ambient relative humidity RHa from sensor 5 are input to equation (1) to provide the ambient absolute humidity AHa at S6. At S7, the difference ΔAH between the absolute humidity AHm delivered to the mask and the ambient absolute humidity AHa is determined. The difference ΔAH is the absolute humidity that the humidifier 4 must add to the airflow to deliver the selected moisture content.

[0236] At S8, the flow rate F detected or estimated by the flow sensor 42 and the difference ΔAH are input into equation (3) for determining the required evaporation rate E of the humidifier supply water. At S9, the water temperature or the equivalent temperature of the humidifier heating element 46 required to produce the evaporation rate E is determined, for example, by the closed-loop control discussed above.

[0237] At S10, the difference ΔT between the water temperature detected by the sensor 48 and the desired water temperature determined at S9 is calculated. The controller 40 and / or 44 controls the heating element 46 of the humidifier 4 until the difference between the desired water temperature and the detected water temperature is substantially zero. Alternatively, the heating element 46 is controlled until the difference between the desired heating element temperature and the detected heating element temperature is substantially zero.

[0238] Second Embodiment of Humidity Control

[0239] refer to Fig.16 , illustrates a control system and method of a breathing apparatus according to another exemplary embodiment. During use of the breathing system, the flow rate can be, for example, The effect of the control algorithm is changed, which can provide a relatively slow flow change, or due to the occurrence of leaks, such as leaks around the mask cushion or around the mouth when using a nasal mask, which can provide a relatively fast flow change. If the flow changes quickly, the control of the heated tube or hose and / or humidifier may not respond quickly enough to prevent condensation in the tube because the humidifier takes a relatively long time to change the temperature of the supply water, making the response slower.

[0240] like Fig.16As shown, at S12, a change or difference ΔF in the flow rate detected by the flow sensor 42 or estimated, for example, from the blower speed is determined. The difference ΔF can be determined by comparing the flow rates detected or estimated at periodic intervals. At S13, the difference ΔF is compared with a predetermined difference ΔF. ptd If the difference ΔF between the periodic flows exceeds a predetermined amount ΔF ptd , the process proceeds to S14 and adjusts the temperature Tm of the gas delivered to the patient interface, for example by controlling the heating tube 30 using the controller 40 and / or 44. If the difference ΔF does not exceed the predetermined amount ΔF ptd The processing progress is the same as described above with respect to the first embodiment, and the required evaporation rate is calculated in S8 based on the absolute humidity difference ΔAH and the detected or estimated flow rate.

[0241] If the difference ΔF is a negative value, that is, the flow rate changes to decrease, the temperature Tm increases in S14. The temperature Tm can be increased in S14 to a sufficient temperature to maintain the temperature Tm of the air delivered to the patient interface above the saturation point. The decrease in flow also causes the water temperature or the temperature of the heating element to decrease in S9, the difference ΔT is calculated in S10, and the heating element is controlled by the controller 40 and / or 44 to reduce the temperature set point of the humidifier. As the temperature of the humidifier supply water decreases, the absolute humidity AHm has a margin for overshoot and does not reach the saturation point.

[0242] In S11, the difference ΔTm between the temperature detected by the temperature sensor 54 and the adjusted temperature Tm is determined, and the heating tube 30 is controlled until the difference ΔTm is substantially zero. After a predetermined time period, the adjusted temperature Tm is gradually reduced in S12 until the temperature of the supply water in the humidifier is reduced to a new set point of the humidifier.

[0243] If the flow difference ΔF determined in S11 is a positive value, that is, the change in flow is an increase, and the flow difference is greater than the predetermined difference ΔF ptd , then the adjustment in S14 may be to reduce the temperature Tm so as to keep the absolute humidity AHm close to saturation. However, the patient may find that reducing the temperature Tm is uncomfortable. In this case, the controller 40 and / or 44 may be configured to ignore the flow difference ΔF indicating an increase in flow.

[0244] The humidifier and respiratory apparatus discussed herein with respect to the exemplary embodiments provide an automatic or default setting for inexperienced or new users of heated humidifiers, which is designed to provide a default moisture content (nominal 14 mg / L) to the delivered air under any given use conditions. During the patient's sleep, if necessary, an automatic compensation is triggered to reduce the default moisture content target value to avoid condensation in the air tubes.

[0245] Proper operation of a humidifier according to exemplary embodiments disclosed herein does not require any user knowledge or intervention in order to properly set up and operate the device. This is helpful for users who find it difficult to establish proper humidifier settings. Proper operation is automatically maintained during patient sleep in response to changes in factors that affect the moisture content of the delivered air and the potential for condensation, including ambient absolute humidity, ambient temperature, relative humidity and pressure, and delivered air flow rate.

[0246] If desired, additional settings may be provided to the user to fine tune the automatic or default settings, depending on their preference. The full scale range of available settings is constantly re-adjusted to keep the centered value calibrated at the default moisture content to prevent condensation in the air delivery hose as described above. This means that, unlike prior art humidifiers, the default settings and the available full scale range of the settings are always calibrated to the actual environmental conditions. Climatic differences in one region, such as a cold and humid climate, do not compromise the achievable humidification performance or achievable settings in another region as would be the case in a device with fixed heater settings.

[0247] For example, the user may determine that a setting lower than the default or automatic setting, such as "3" marked by indicator 11, or a setting higher than the default or automatic setting, such as "7" marked by indicator 11, provides the most comfortable humidified airflow. The user can thus select the desired setting and the absolute humidity of the airflow delivered to the patient interface will be the most comfortable, as determined by the patient, regardless of ambient conditions and / or flow rate.

[0248] Third embodiment of humidifier control

[0249] refer to Fig.17 , illustrates a control system and process for a respiratory apparatus according to another exemplary embodiment. Fig.17 The system and process of the exemplary embodiment of the present invention, the operations of S1-S8 and S11 are the same as those described above. Fig.15 The corresponding steps of the exemplary embodiment operate similarly.

[0250] After calculating the evaporation rate required to deliver a predetermined humidity at a predetermined temperature in S8, in S15, a heating element temperature threshold is determined, a fixed duty cycle is applied when the temperature is above the threshold, and the duty cycle for driving the humidifier is determined in S16. After determining the heating element temperature threshold in S15, it is determined in S17 whether the temperature of the heating element is above the threshold. If the temperature of the heating element is above the threshold (S17: Yes), a fixed duty cycle is applied to the heating element in S21. If the temperature of the heating element is not above the threshold (S17: No), a 100% duty cycle is applied to the heating element in S18.

[0251] In S19, it is determined whether the heating element temperature detected by the heating element temperature sensor 48 is higher than the safe operating temperature. If the detected heating element temperature is lower than the safe operating temperature (S19: No), the heating element temperature is checked again in S17 to determine whether the heating element temperature is higher than the threshold value. If the detected heating element temperature is higher than the safe operating temperature (S19: Yes), the duty cycle of the heating element is set to 0% in S20, that is, the heating element is turned off.

[0252] The humidifier can be configured to operate using different types of containers or barrels for holding a supply of water. One such humidifier is disclosed, for example, in U.S. application 61 / 097,765, filed on September 17, 2008, the entire contents of which are incorporated herein by reference. There are two types of humidifier barrels that can be used, a "reusable" barrel having, for example, a stainless steel base, and a "disposable" barrel having, for example, an aluminum base. The heat exchange characteristics of the two bases are different. When the heating element is adjusted to room temperature, the two barrels can provide different humidity outputs. However, it is desired that the humidity output is predictable regardless of which barrel is fixed to the device. It is also preferred when there is a tool to detect what type of barrel is fixed to the humidifier.

[0253] The humidity output is related to the duty cycle of providing power to the heating element, not the temperature maintained by the heating element, as referenced above. Fig.17 This is because at a constant duty cycle, power is delivered to the heating element at a constant rate, and the main consumption of power in the system is through the evaporation of water in the bucket. In fact, when operating at the same duty cycle, the "disposable" and "reusable" buckets have the same evaporation rate.

[0254] Also as reference Fig.17 As described, the exemplary embodiment applies power to the heating element at a constant duty cycle, rather than varying the duty cycle to adjust the temperature of the hot plate. The heating element is a resistive load R, such as 9.6 ohms, which is turned on and off at a timing defined by the duty cycle for a constant potential V, such as 24V. This is equivalent to a constant duty cycle with P = V 2 The electrical power defined by / R, for example 60W of electrical power at 100% duty cycle drives the heating element.

[0255] Can be used with Fig.15 and 16 The duty cycle is determined in the same manner as the temperature set point for the heating element in the illustrated embodiment - through the characteristics of the device, whose performance takes into account three variables: the absolute humidity of the environment, the temperature of the gas delivered to the patient, and the flow rate of the gas delivered.

[0256] Two disadvantages of constant duty cycle operation are also overcome by this exemplary embodiment. The first disadvantage is that the body of water in the humidifier takes longer to warm up from a cold original state. This disadvantage is overcome by estimating a temperature threshold in S15 and driving the heating element at 100% duty cycle in S18 until it reaches the temperature threshold, and then switching to a constant or fixed duty cycle level required for the desired evaporation rate in S21.

[0257] The second disadvantage is that once the water in the humidifier barrel is empty, for example when all the water therein has evaporated, the heating element may reach an extremely high temperature. This disadvantage is overcome by applying the operation of the maximum safe temperature in S19 and setting the duty cycle to 0% in S20 to disable the heating element if the maximum safe temperature is exceeded.

[0258] Fig.17 The exemplary embodiment of can also be used to control a humidifier without a heated tube. In this case, the patient directly controls the adjusted temperature of the heating element through the user interface (e.g., knob or dial 10 and / or control button 14) and can adjust it for comfort, so that patients using a reusable barrel can tend to set a slightly higher temperature than patients using a disposable barrel. Without controlling the duty cycle of the power provided to the heating element, a humidifier using a reusable barrel will deliver less humidity than a humidifier using a disposable barrel and provide less comfort to the patient that is conducive to humidification.

[0259] Fig.17 The exemplary embodiment also provides equal humidification therapy to all patients while maintaining ease of operation.

[0260] Fourth embodiment of humidifier control

[0261] In addition to controlling the duty cycle of the heating element 46 of the humidifier, the controller 40 and / or 44 can also be configured to control the duty cycle of the heating element of the air delivery hose or tube 30. This allows the humidifier to reduce the total capacity of its power supply. The humidifier heating element and the heating tube can share the power load, so that when the humidifier heating element or heating tube may obtain its full current, such as an instantaneous current of 2.5A under 24V, they are never actuated at the same time. The controller 40 and / or 44 calculates the duty cycle to be distributed to each of the humidifier and the heating tube, so that the composite duty cycle does not exceed 100%. The controller 40 and / or 44 also synchronizes the heating cycles of the humidifier and the heating tube so that they do not overlap. The controller 40 and / or 44 can be configured to regularly turn on and off each heating element according to the duty cycle provided by the airflow generator, so that only one device is turned on at the same time. Such power management controls are disclosed, for example, in U.S. Application No. 61 / 095,714, filed September 10, 2008, the entire contents of which are incorporated herein by reference.

[0262] According to this exemplary embodiment, the input values ​​include: 1) the temperature set point of the heating tube, such as set through a user interface or a climate control algorithm; 2) the temperature detected by the heating tube, such as converted by a potential difference of a thermistor; 3) the type of heating tube (e.g., 15mm or 19mm); 4) the temperature set point of the humidifier, such as set through a user interface or a climate control algorithm; and 5) the temperature detected by the humidifier, such as converted by a potential difference of a thermistor.

[0263] The output values ​​of the exemplary embodiment include: 1) heating power applied to the humidifier, for example, with a duty cycle from 0% to 100%; and 2) heating power applied to the heating tube, for example, with a duty cycle from 0% to 100%.

[0264] The control also includes the use of constants for the heating tube, including: 1) proportional factor Pf; 2) integer factor If; and 3) derivative factor Df. Similarly, the control also includes the use of constants for the humidifier, including: 1) proportional factor Pf; 2) integer factor If; and 3) derivative factor Df.

[0265] Internal variables include: 1) the detected humidifier temperature relative to the previous reading, Told; 2) the cumulative sum of the humidifier temperature differences, sumTd; 3) the detected heater tube temperature relative to the previous reading, Told; and 4) the cumulative sum of the heater tube temperature differences, sumTd.

[0266] The controller 40 and / or 44 may include a simplified proportional-integral control function:

[0267] 1. Calculate the temperature difference Td = this temperature reading minus the previous reading Told.

[0268] 2. If the measured temperature is close to the set point (|Td| is less than 1 / Pf),

[0269] a. Then multiply Td by the integer factor If and add the result to the cumulative sum of the temperature differences sumTd,

[0270] b. Otherwise reset sumTd to zero.

[0271] 3. Calculate duty cycle = Pf*Td+If*sumTd.

[0272] 4. The trim duty cycle is between 0 and 1.

[0273] The duty cycle of each of the humidifier and the heater tube is then compared.

[0274] 1. If the sum of the duty cycles of the humidifier and the heater tube exceeds 1.0, reduce one or both duty cycles. For example, reduce the heater tube duty cycle to 0.5, and then reduce the humidifier duty cycle to the necessary extent.

[0275] 2. Both duty cycles are multiplied by 100 for output to the humidifier controller as integer values ​​from 0 to 100 (indicating 100%).

[0276] Fifth embodiment of humidifier control

[0277] According to another exemplary embodiment, the controller 40 and / or 44 may be configured to control the humidifier heating element and the heating tube using the following input values, the input values ​​including: 1) the air flow detected by the airflow generator, such as the average flow over one minute; 2) the ambient relative humidity, such as determined or detected by the humidifier; 3) the ambient temperature, such as detected by the humidifier; 4) if a heating tube is connected, the temperature detected by the heating tube, such as expressed in ° C; 5) the heating tube setting from the user interface, such as expressed in ° C, or an automatic setting; 6) the humidifier setting from the user interface, such as an automatic setting or a setting that is "wetter" or "drier" than the standard automatic setting; 7) a time stamp.

[0278] The output values ​​of the control may include: 1) the temperature set point of the humidifier; and 2) the temperature set point of the heating tube.

[0279] Constants used for control may include: 1) a conversion factor from relative humidity to absolute humidity comprising a) three coefficients applied to a quadratic equation; and 2) a table that determines the temperature set point from the desired humidifier humidity output.

[0280] The table can be a matrix of points from which set points can be interpolated three-dimensionally, comprising: a) an axis for average air flow, for example at intervals of 12 L / min corresponding to 10 to 70 L / min, which provides six points; b) an axis for desired absolute humidity output, for example at intervals of 8 mg / L corresponding to 0 to 40 mg / L, which provides six points; and c) an axis for ambient absolute humidity, for example at intervals of 5 mg / L corresponding to 0 to 35 mg / L, which provides eight points.

[0281] The total matrix size provides 6x6x8 = 288 data points. Each data point is a temperature from 5 to 95° C. in increments of 0.1° C. The matrix can be, for example, as shown in Table 6 below.

[0282]

[0283]

[0284]

[0285]

[0286]

[0287]

[0288]

[0289]

[0290]

[0291]

[0292]

[0293] Table 6

[0294] Internal variables may include: 1) ambient absolute humidity; 2) absolute humidity arriving at the mask target; 3) absolute humidity added by the humidifier; and 4) measured prior flow.

[0295] To generate a temperature set point for the humidifier, controllers 40 and / or 44:

[0296] 1. According to the formula: absolute humidity = relative humidity (ratio of 1) x (a + b x temperature + c x temperature x temperature), the ambient absolute humidity is calculated using the ambient relative humidity and temperature, where the given constant coefficients are a = 7.264, b = 0.0928, and c = 0.0293.

[0297] 2. Calculate the target absolute humidity based on the temperature detected by the heater. If heaters are not available, the ambient temperature can be used instead. The function is the same quadratic equation used in step 1, but now the relative humidity is set through the user interface.

[0298] 3. Calculate the absolute humidity to be added by the humidifier by subtracting the ambient absolute humidity from the target.

[0299] 4. Calculate the temperature set point for the humidifier based on the added absolute humidity, flow rate, and ambient temperature. The calculation is a trilinear interpolation of Table 6.

[0300] To generate the temperature set point for the heating tube:

[0301] 1. The default temperature set point corresponds to the setting on the user interface.

[0302] 2. If the flow rate suddenly drops, the temperature set point can be adjusted slightly (eg, a few degrees Celsius) above the set point for a limited time (eg, 15 minutes).

[0303] Airflow Generator Design Considerations

[0304] When the humidifier is mounted on or removed from the airflow generator, the user interface of the airflow generator may indicate, for example, within one second that the humidifier is detected or removed. When the heating tube is mounted on or removed from the humidifier, the user interface of the airflow generator may indicate, for example, within one second that the heating tube is detected or removed.

[0305] As described above, the airflow generator controller can control the humidifier and the heated tube. The airflow generator controller can use constants stored in the humidifier controller, which include, for example, six control parameters, each with a value between 0 and 1 and a precision of 0.01 and a matrix with 6x6x8=288 data points. Each data point can be a temperature from 5 to 95°C with a precision of 0.1°C.

[0306] During treatment, the airflow generator may poll the humidifier to read the temperature of the heating element and the heating tube of the humidifier, for example, at least once every 10 seconds. During treatment, the airflow generator may poll the humidifier to read the ambient temperature and relative humidity, for example, at least once every 60 seconds.

[0307] Temperature can be passed as a numeric value from 5 to 95°C with a precision of 0.1°C. Relative humidity can be passed as an integer value from 0 to 100. Values ​​outside this range should be clamped to this range.

[0308] The airflow generator may calculate the duty cycle applied by the humidifier as an integer value between 0 and 100 (where 100 represents a 100% duty cycle). The airflow generator may also calculate the duty cycle applied to the heater tube as an integer value between 0 and 100 (where 100 represents a 100% duty cycle). The airflow generator may ensure that the sum of the duty cycles for the humidifier and the heater tube does not exceed 100 (representing 100%).

[0309] During treatment, a request from the flow generator to set a humidifier duty cycle may be transmitted, for example, at least once every 3 seconds, and a request from the flow generator to set a heater tube duty cycle may be transmitted, for example, at least once every 1 second.

[0310] Humidifier Design Considerations

[0311] When both the heating tube and the humidifier require heating, the controller 40 and / or 44 can ensure that power is distributed so that the two items do not draw power at the same time. For this reason, the heating tube and the humidifier can be controlled by the same controller.

[0312] A suitable communication protocol can be developed to enable the airflow generator to communicate with the humidifier, power supply, and any other devices that may be added. The communication protocol can utilize, for example, a 16-bit CRC to detect communication errors. The communication between the airflow generator and the humidifier can be half-duplex to minimize the number of pins on the wiring connector.

[0313] The humidifier can transmit the following information to FG according to the instructions: 1) humidifier status (normal or error); 2) relative humidity reading; 3) temperature at which the relative humidity reading is obtained; 4) temperature of the heating element in the humidifier; 5) humidifier heating duty cycle.

[0314] The humidifier may respond to the following instructions from the flow generator: 1) humidifier status is requested; 2) humidity reading is requested; 3) temperature of humidity reading is requested; 4) temperature of heating element in the humidifier is requested; 5) heating duty cycle in the humidifier is set.

[0315] The humidifier may stop heating the humidifier barrel unless a request for the set heating duty cycle is received at least every 10 seconds.

[0316] Heating tube design considerations

[0317] The humidifier can transmit the following information to the airflow generator according to instructions: 1) the status of the heating tube, including a) the presence or absence of the heating tube, b) the diameter of the heating tube (15mm or 19mm), and c) normal or error; 2) the temperature inside the heating tube; and 3) the humidifier heating duty cycle.

[0318] The humidifier may respond to the following instructions from the flow generator: 1) a heating tube state is required; 2) a temperature in the heating tube is required; 3) a heating power level within the humidifier is set.

[0319] The humidifier may stop heating the heater tube unless a request for a set heating duty cycle is received, for example, at least every 1 second.

[0320] Temperature Conversion

[0321] The controller 40 and / or 44 may utilize a lookup table to convert the potential measured on the thermistor into a temperature, for example, expressed in ° C. Three tables are required: 1) and 2) temperature conversion tables for each type of heating tube (e.g., 15 mm and 19 mm) (each of the two tables has approximately 360 data points for a range of 5 to 40 ° C at an accuracy of 0.1 ° C); and 3) a temperature conversion table for the humidifier (approximately 960 data points for a range of 5 to 95 ° C at an accuracy of 0.1 ° C). Each may be a lookup table that is represented by being evenly spaced on the thermistor potential axis.

[0322] Climate control constant delivered to the airflow generator

[0323] The humidifier can carry a table, such as Table 6, as constants and transmit it to the airflow generator before climate control begins. In this way, the upgrade of the humidifier can be completed in the humidifier without upgrading the airflow generator software.

[0324] Indicator Lights

[0325] The humidifier can directly control a blue and an amber LED based on commands from the flow generator, such as using commands via a serial communication link. The humidifier can control the indicator lights based on commands received from the flow generator, each command can include the following information: 1) color - blue or amber; 2) brightness - bright, dim or off; and 3) gradient - yes or no.

[0326] If the fade is: 1) yes, the brightness should transition smoothly over three seconds; or 2) no, the brightness should switch to the new level. The two indicator lights of the humidifier can fade at the same time, for example, for a uniform fade, the airflow generator can send two commands at the same time - one command to fade one indicator light off, and another command to fade the other indicator light on.

[0327] Humidifier Control Sixth Embodiment

[0328] A patient who sleeps with a humidifier set to deliver below-saturation humidity in the tubes may experience condensation in the tubes under three circumstances: 1) a decrease in ambient temperature, so that the air cools below its dew point in the tubes; 2) an increase in ambient humidity, so that the air leaving the humidifier increases in humidity and then cools below its dew point in the tubes; and 3) a decrease in flow, such as when the automatic setting reduces the disposal pressure, the humidifier adds more humidity to the air, which then cools below its dew point in the tubes.

[0329] Current recommendations for patients to address condensation or rain wash issues in the tubes include extending the tubes below the bedding to reduce cooling in the tubes and / or setting the humidifier to a lower heat set point. These methods result in the patient receiving less humidity throughout the night due to being further from the dew point after accounting for nighttime variations.

[0330] As described above, exemplary embodiments provide for implementing climate control to deliver air of a predetermined temperature and humidity to the mask end of the tube. However, the climate control described with reference to the prior exemplary embodiments requires a temperature sensor within the tube to monitor the temperature of the air within the tube. A heated tube with temperature sensing adds cost, and therefore it is advantageous to provide condensation relief to the patient in a system with a conventional, i.e., non-heated tube.

[0331] refer to Fig.18According to another exemplary embodiment, climate control is provided in a duct which is not heated and the delivered air temperature is not measured, but the air temperature is estimated in S22 from the reading of the ambient temperature sensor. The estimation is based on the characteristics of the temperature difference between the reported ambient temperature and the delivered air temperature in different cases of ambient temperature, air flow and the heating source in the device, such as power, motor, electronic or humidifier heating element.

[0332] As described above, Comparative Example 1 (Table 2) shows the above reference Fig.15 and 16 Response to changes in ambient temperature without changes in ambient absolute humidity and without control of mask temperature Tm according to an exemplary embodiment. According to this exemplary embodiment, where the delivered air temperature Tm is not measured but estimated, an equivalent table for adjusting water temperature to change ambient humidity is shown in Table 7 below for three different choices of ambient air temperatures.

[0333]

[0334]

[0335] Table 7

[0336] A feature of this exemplary embodiment is that the temperature of the transported air is estimated so that the device does not detect whether the duct is insulated from the ambient temperature, for example by a bed cover or bedding. Insulation can increase the temperature of the transported air by reducing cooling in the duct. To reduce the possibility of condensation, it can be assumed that the duct is not insulated and therefore the transported air is cooler and closer to its dew point than if insulation is provided.

[0337] It will be appreciated that the system of this exemplary embodiment will respond appropriately to changes in ambient temperature and ambient humidity and air flow simultaneously. The system of this exemplary embodiment provides protection of the tubing from condensation throughout the night regardless of changes in ambient temperature, humidity and flow. The system of this exemplary embodiment also provides fully automatic control of the humidifier. With a default value of a predetermined relative humidity of the delivered gas, the patient never needs to adjust the humidifier. The system of this exemplary embodiment also provides a humidity setting through the user interface, which can be converted into a predetermined relative humidity of the delivered gas.

[0338] Unlike other exemplary embodiments that include heated tubing, this exemplary embodiment does not deliver warmer air or the higher humidity carried by warmer air. This exemplary embodiment also does not allow the patient to select the temperature of the delivered air. This exemplary embodiment also does not increase the delivered humidity if the tubing is insulated. Changing the humidity setting through the user interface can overcome this.

[0339] Humidifier control according to this exemplary embodiment allows the respiratory device to be provided with standard tubing rather than heated tubing, thereby reducing system cost.

[0340] The exemplary embodiments described above may also be implemented entirely in software or hardware (eg, an ASIC), such that a humidifier may be configured to operate as any of the three exemplary embodiments without increasing the bill of materials cost of the device.

[0341] Humidifiers according to exemplary embodiments disclosed herein improve user compliance due to increased comfort, reduced likelihood of dry / sore throat, and / or increased ease of use by providing automatic optimized humidification settings.

[0342] Humidifiers according to exemplary embodiments disclosed herein also provide a solution to the problem that prior art humidifiers only track room ambient temperature and flow, that is, such humidifiers can track inappropriate humidity output due to human error / confusion in establishing the initial settings. Users of such humidifiers do not know what setting is closest to the optimal humidification level for any given situation, especially when they experience significant changes from their usual environment / climate, for example, when traveling.

[0343] Humidifiers and breathing apparatus according to exemplary embodiments disclosed herein measure ambient relative humidity and pressure (altitude compensation), as well as ambient temperature to improve the accuracy of delivered humidity levels relative to prior art systems that do not detect ambient humidity and pressure. The availability of low-cost humidity and pressure sensors in recent years now makes it feasible and achievable to monitor the above additional parameters even on CPAP devices.

[0344] Humidifiers and respiratory devices according to exemplary embodiments disclosed herein will respond to a detected persistent mouth leak, but unlike prior art systems will modify the humidity output to optimize humidity density rather than simply arbitrarily setting a setting that is unlikely to be close to optimal.

[0345] Although the present invention has been described in conjunction with what are currently considered to be the most feasible and preferred embodiments, it is understood that the present invention is not limited to the disclosed embodiments, but rather, the present invention is intended to cover various changes and equivalent configurations included in the spirit and scope of the present invention. In addition, the various embodiments described above may also be performed in conjunction with other embodiments, for example, some schemes of one embodiment may be combined with some schemes of another embodiment to implement yet another embodiment. Further, each individual feature or component of any given assembly may constitute an additional embodiment. In addition, each individual component of any given assembly, one or more parts of a single component of any given assembly, and various combinations of components from one or more embodiments may include one or more decorative design features. In addition, although the present invention has particular applications to patients with OSA, it should be recognized that patients with other diseases (e.g., congestive heart disease, diabetes, morbid obesity, stroke, bariatric surgery, etc.) may benefit from the above teachings. In addition, the above teachings are applicable to both patients and non-patients for non-medical applications.

[0346] In this specification, the word "comprising" should be understood in its "open" sense, i.e., the meaning of "including", and is not limited to its "closed" sense, i.e., the meaning of "consisting only of..." The corresponding meaning also applies to the corresponding words "comprise", "comprised" and "comprises" where they appear.

[0347] It should be further understood that reference to any prior art herein, unless otherwise indicated, does not constitute an admission that such prior art is known to those skilled in the art relevant to the present invention.

Claims

1. A humidifier for a respiratory apparatus for delivering a humidified flow of breathable gas to a patient, the humidifier comprising: a humidifier chamber configured to store a supply of water for humidifying the flow of breathable gas, the humidifier chamber comprising a first heating element configured to heat the supply of water; a relative humidity sensor for detecting the relative humidity of ambient air and generating a signal indicative of the ambient relative humidity; a first temperature sensor for detecting the temperature of the ambient air and generating a signal indicative of the ambient temperature; as well as A controller is configured to determine an absolute humidity of ambient air based on signals generated by the relative humidity sensor and the first temperature sensor and to control the first heating element to provide a predetermined relative humidity to the flow of breathable air. 2 . The humidifier of claim 1 , wherein the controller is further configured to control the first heating element to provide a flow of breathable gas at a predetermined temperature. 3 . The humidifier according to claim 2 , wherein the controller determines a predetermined absolute humidity corresponding to a predetermined relative humidity and a predetermined temperature. The humidifier according to claim 3 , wherein the predetermined absolute humidity is approximately 11-44 mg / L.

5. The humidifier according to claim 2, wherein the predetermined temperature is approximately 15°C-37°C.

6. The humidifier according to claim 2, wherein the predetermined temperature is approximately 26°C-28°C.

7. A humidifier for a respiratory apparatus for delivering a humidified flow of breathable gas to a patient, the humidifier comprising: a humidifier chamber configured to store a supply of water for humidifying the flow of breathable gas, the humidifier chamber comprising a first heating element configured to heat the supply of water; a relative humidity sensor for detecting the relative humidity of ambient air and generating a signal indicative of the ambient relative humidity; a first temperature sensor for detecting the temperature of the ambient air and generating a signal indicative of the ambient temperature; as well as A controller is configured to determine an absolute humidity of the ambient air based on signals generated by the relative humidity sensor and the first temperature sensor and to control the first heating element to provide a predetermined absolute humidity, a predetermined temperature and / or a predetermined relative humidity to the flow of breathable air.

8. A humidifier for a respiratory apparatus for delivering a humidified flow of breathable gas to a patient, the humidifier comprising: a humidifier chamber configured to store a supply of water for humidifying the flow of breathable gas, the humidifier chamber comprising a first heating element configured to heat the supply of water; an absolute humidity sensor that detects the absolute humidity of the humidified airflow and generates a signal indicative of the absolute humidity; and A controller is configured to receive the signal from the absolute humidity sensor and control the first heating element to provide a predetermined absolute humidity, a predetermined temperature, and / or a predetermined relative humidity to the flow of breathable gas.

9. A respiratory apparatus for providing a humidified flow of breathable gas to a patient, comprising: an airflow generator for generating a breathable airflow; as well as A humidifier according to any one of claims 1 to 8.

10. A method of humidifying a flow of breathable gas provided to a patient, the method comprising: Determine the absolute humidity of the ambient air used to form the breathable airflow; as well as The temperature of the supply of water humidifying the flow of breathable gas is controlled to provide a predetermined absolute humidity corresponding to a predetermined temperature and a predetermined relative humidity of the gas flow delivered to the patient.

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