Respiratory humidification system

• US 6,349,722 B1
• Filed: 06/16/1998
• Issued: 02/26/2002
• Est. Priority Date: 06/17/1997
• Status: Expired due to Term

• Current Assignee: Fisher & Paykel Healthcare Limited
• Original Assignee: Fisher & Paykel Limited
• Inventors: Gradon, Lewis George, McPhee, Stephen William, Leonard, Peter John, Seakins, Paul John
• Primary Examiner(s): Weiss, John G.
• Assistant Examiner(s): WEISS JR, JOSEPH
• Application Number:
  US09/097,832
• Time in Patent Office: 1,351 Days
• Field of Search: 128/203.12, 128/203.16, 128/203.17, 128/203.26, 128/204.17, 128/204.22, 261/129, 261/130, 261/131, 261/142, 261/DIG.65, 219/490, 219/494, 165/222, 165/223, 165/229, 165/230, 165/253, 165/281, 165/287-290, 165/295, 236/44.R, 236/20.E, 236/912, 236/DIG.13, 392/460-466
• US Class Current: 128/203.17
• CPC Class Codes: A61M 16/0051 with alarm devices
• CPC Class Codes: A61M 16/0066 Blowers or centrifugal pumps
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 16/0841 for sampling
• CPC Class Codes: A61M 16/1075 by influencing the temperature A61M16/1045 takes precedence
• CPC Class Codes: A61M 16/109 the humidifying liquid or the beneficial agent
• CPC Class Codes: A61M 16/1095 in the connecting tubes
• CPC Class Codes: A61M 16/16 Devices to humidify the respiration air A61M16/1045 takes precedence
• CPC Class Codes: A61M 16/161 with means for measuring the humidity
• CPC Class Codes: A61M 16/162 Water-reservoir filling system, e.g. automatic
• CPC Class Codes: A61M 2016/0039 in the inspiratory circuit
• CPC Class Codes: A61M 2205/18 with alarm
• CPC Class Codes: A61M 2205/3331 Pressure; Flow
• CPC Class Codes: A61M 2205/3368 Temperature
• CPC Class Codes: G01F 1/684 Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
• CPC Class Codes: G01F 1/6842 with means for influencing the fluid flow
• CPC Class Codes: G01F 1/6888 Thermoelectric elements, e.g. thermocouples, thermopiles
• CPC Class Codes: G08B 21/16 Combustible gas alarms
• CPC Class Codes: Y10S 261/65 Vaporizers

Abstract

A flow probe for use in a humidification system is disclosed. The flow probe is adapted to be positioned in a humidified gases flow (for example oxygen or anaesthetic gases) such as that which is provided to a patient in a hospital environment. The flow probe is designed to provide both temperature and flow rate sensing of the gases flow by incorporating two sensors (preferably thermistors) and the shape and alignment of the probe enables accurate readings by reducing the occurrence of condensation on the sensors. A number of possible applications are disclosed wherein the flow sensor is, included in humidification control systems which provide a patient with a desired humidity level or simplify the amount of user input required or wherein the flow sensor provides a controller with flow information which may then be used to determine certain, possibly dangerous, conditions (such as incorrect flow sensor placement, breathing circuit disconnected, no water in the humidification chamber or humidity out of required limits).

Claims

1. Humidification apparatus for humidifying a gaseous flow to be supplied to a patient or other person in need of such gaseous flow comprising:

humidificaion chamber means adapted to hold a quantity of water and having an inlet and an outlet to allow said gaseous flow to pass through said humidification chamber means,

heating means provided adjacent said humidification chamber means and adapted to provide heat to said quantity of water in said humidification chamber means in order to provide water vapor to said gaseous flow passing through said humidification chamber means,

gaseous flow transportation pathway means connected to said outlet of said humidification chamber means to convey said gaseous flow to said patient or other person in need of such gaseous flow,

flow probe means adapted to sense the flow rate of said gaseous flow,

probe heating means adapted to heat at least a portion of said flow probe means,

temperature sensing means adapted to sense the temperature of said gaseous flow,

user input means to allow a user to set a required temperature of said gaseous flow,

control means which receives input from said flow probe means, said temperature sensing means and said user input means and controls said heating means in response to said inputs to maintain said gaseous flow at said required temperature.

2. Humidification apparatus as claimed in claim 1 said control means is adapted to determine if the humidification apparatus is in a normal operating condition or if abnormal operation has occurred based on said temperature and/or said flow rate, wherein said normal condition in use relating to whether said temperature and/or said flow rate falling with a predetermined range.

3. Humidification apparatus for humidifying a gaseous flow to be supplied to a patient or other person in need of such gaseous flow comprising:

humidification chamber means adapted to hold a quantity of water and having an inlet and an outlet to allow said gaseous flow to pass through said humidification chamber means,

gaseous flow transportation pathway means connected to said outlet of said humidification chamber means to convey said gaseous flow to said patient or other person in need of such gaseous flow,

flow probe means adapted to sense the flow rate of said gaseous flow including sensor housing means adapted for positioning in said gaseous flow, said sensor housing means having a longitudinal axis substantially perpendicular to said humidified gaseous flow and a sensing end, sensing means housed within said sensor housing means at or near said sensing end, and at least two projecting tab means extending laterally from said sensor housing means, oppositely positioned around said sensor housing means and aligned parallel to said gaseous flow, wherein liquid condensate is dispersed along the lines of intersection between said sensor housing means and said at least two tab means away from said sensing end of said sensor housing means, there existing a localized area of low surface tension along said lines of intersection,

temperature sensing means adapted to sense the temperature of said gaseous flow,

user input means to allow a user to set a required temperature of said gaseous flow,

control means which receives input from said flow probe means, said temperature sensing means and said user input means and controls said heating means in response to said inputs to maintain said gaseous flow at said required temperature.

4. Humidification apparatus as claimed in claim 3 wherein said flow probe means comprise two sensor housing means, a temperature sensor housing means and a flow rate sensor housing means, each comprising a temperature dependent resistance,

and wherein said sensing means of said flow rate sensor housing means is occasionally heated to a predetermined difference temperature above the temperature of said gaseous flow, the power required by said sensor means of said flow rate sensor housing means to maintain said predetermined difference temperature providing an indication of the flow rate of said gaseous flow,

and wherein said sensing means of said flow rate sensor housing means is exposed at or near the sensing end of the flow rate sensor housing means up stream of and spaced across said gaseous flow from the sensing means of said temperature sensor housing means is encapsulated at or near the sensing end of the temperature sensor housing means, in order that heat produced by the sensing means of said flow rate sensor housing means does not effect the sensing means of said temperature sensor housing means.

5. Humidification apparatus as claimed in claim 3 wherein said gaseous flow transportation pathway means has a known cross-sectional area, at least in the region adjacent said flow probe means, and is provided with a sensor entry port adapted to receive said flow probe means, said sensor entry port being provided with a fixed locating depression and said flow probe means being provided with a complimentary fixed locating tooth, the positioning of said temperature and flow rate sensor housing means relative to said gaseous flow being controlled by the interconnection of said locating depression and tooth.

6. Humidification apparatus for humidifying a gaseous flow to be supplied to a patient or other person in need of such gaseous flow comprising:

humidification chamber means adapted to hold a quantity of water and having an inlet and an outlet to allow said gaseous flow to pass through said humidification chamber means,

heating means provided adjacent said humidification chamber means and adapted to provide heat to said quantity of water in said humidification chamber means in order to provide water vapor to said gaseous flow passing through said humidification chamber means, said heating means utilizing a measurable quantity of power,

gaseous flow transportation pathway means connected to said outlet of said humidification chamber means to convey said gaseous flow to said patient or other person in need of such gaseous flow,

flow probe means adapted to sense the flow rate of said gaseous flow,

control means which receives input from said flow probe means and including storage means which is programmed to;

i.) calculate the power usage required of said heating means in order to humidify said gaseous flow to a predetermined level at the gaseous flow rate sensed by said flow probe means,

ii.) determine the power presently being utilized by said heating means, and

iii.) supply said predetermined level of power to said heating means if the determined present power utilization of said heating means is less than said required power usage.

7. Humidification apparatus as claimed in claim 6 wherein said step of calculating the power usage required of said heating means in order to humidify said gaseous flow comprises sensing the present gaseous flow by said flow probe means and searching in a data storage means for a previously stored power value associated with said sensed gaseous flow rate, said data storage means being previously supplied with flow rate and associated power usage values.

8. Humidification apparatus as claimed in claim 6 or claim 7 wherein said step of calculating the power usage required of said heating means in order to humidify said gaseous flow also comprises the steps of calculating the rate of evaporation required in order to attain said predetermined level at the sensed gaseous flow rate and then determining the power required of said heating means to produce the required said rate of evaporation.

9. Humidification apparatus as claimed in claim 6 or claim 7 wherein said humidification apparatus also comprises a temperature sensing means adapted to sense the temperature of said gaseous flow leaving said humidification chamber means and to supply a temperature signal to said control means and said program stored by said control means includes, between said steps (ii) and (iii), the step of:

a) controlling the energization of said heating means in order to maintain said gaseous flow rate exciting said humidification chamber means at a predetermined temperature.

10. Humidification apparatus as claimed in claim 6 or claim 7 wherein said program stored by said control means also comprise the subsequent step of:

i.) sensing the temperature of the gaseous flow leaving the humidification chamber means and returning to step (c) when the sensed temperature is less than said predetermined temperature.

11. Humidification apparatus as claimed in claim 6 or claim 7 wherein said flow probe means comprises:

sensor housing means adapted for positioning in said gaseous flow, said sensor housing means having a longitudinal axis substantially perpendicular to said humidified gaseous flow and a sensing end,

sensing means housed within said sensor housing means at or near said sensing end, and

at least two projecting tab means extending laterally from said sensor housing means, oppositely positioned around said sensor housing means and aligned parallel to said gaseous flow, wherein liquid condensate is dispersed along the lines of intersection between said sensor housing means and said at least two tab means away from said sensing end of said sensor housing means, there existing a localized area of low surface tension along said lines of intersection.

12. Humidification apparatus as claimed in claim 11 wherein said flow probe means comprise two sensor housing means, a temperature sensor housing means and a flow rate sensor housing means, each comprising a temperature dependent resistance,

and wherein said sensing means of said flow rate sensor housing means is occasionally heated to a predetermined difference temperature above the temperature of said gaseous flow, the power required by said sensor means of said flow rate sensor housing means to maintain said predetermined difference temperature providing an indication of the flow rate of said gaseous flow,

and wherein said sensing means of said flow rate sensor housing means is exposed at or near the sensing end of the flow rate sensor housing means up stream of and spaced across said gaseous flow from the sensing means of said temperature sensor housing means is encapsulated at or near the sensing end of the temperature sensor housing means, in order that heat produced by the sensing means of said flow rate sensor housing means does not effect the sensing means of said temperature sensor housing means.

13. Humidification apparatus as claimed in claim 11 wherein said gaseous flow transportation pathway means has a known cross-sectional area, at least in the region adjacent said flow probe means, and is provided with a sensor entry port adapted to receive said flow probe means, said sensor entry port being provided with a fixed locating depression and said flow probe means being provided with a fixed locating depression and said flow probe means being provided with a complimentary fixed locating tooth, the positioning of said temperature and flow rate sensor housing means relative to said gaseous flow being controlled by the interconnection of said locating depression and tooth.

14. Humidification apparatus for humiditying a gaseous flow to be supplied to a patient or other person in need of such gaseous flow comprising:

humidification chamber means adapted to hold a quantity of water and having an inlet and an outlet to allow said gaseous flow to pass through said humidification chamber means,

heating means provided adjacent said humidification chamber means and adapted to provide heat to said quantity of water in said humidification chamber means in order to provide water vapor to said gaseous flow passing through said humidification chamber means,

gaseous flow transportation pathway means connected to said outlet of said humidification chamber means to convey said gaseous flow to said patient or other person in need of such gaseous flow,

flow probe means adapted to sense the flow rate of said gaseous flow,

temperature sensing means adapted to sense the temperature of said gaseous flow in or adjacent said humidification chamber means,

user input means to allow a user to select a desired gaseous flow humidity level of said gaseous flow configured such that in use said desired gaseous flow humidity level is substantially on delivery to said patient,

data storage means containing information on target gaseous flow temperatures for various gaseous flow rates for a number of humidification chamber outlet means temperatures,

control means configured to receive input from said temperature sensing means and said user input means and configured to repeatedly obtain corresponding target temperature information from said data storage means corresponding to the desired gaseous flow humidity level in relation to said flow rate and configured to vary the heat provided by said heating means until the sensed temperature is substantially equivalent to said target temperature in order to substantially obtain said desired gaseous flow humidity level on delivery to said patient.

15. Humidification apparatus as claimed in claim 14 wherein said gaseous flow transportation pathway means includes a heating wire means adapted to, upon energization to a setting determined by said control means, supply heat to said gaseous flow between said humidification means outlet and said patient or other person in need to such gaseous flow and wherein said control means thereby controls temperature changes in said gaseous flow along said gaseous flow transportation pathway, said control means adjusting said setting of said heating wire to control the temperature of said gaseous flow delivered to said patient or other person in need of such gaseous flow to a user set desired temperature.

16. Humidification apparatus for humidifying a gaseous flow to be supplied to a patient or other person in need of such gaseous flow comprising:

humidification chamber means adapted to hold a quantity of water and having an inlet and an outlet to allow said gaseous flow to pass through said humidification chamber means,

heating means provided adjacent said humidification chamber means and adapted to provide heat to said quantity of water in said humidification chamber means in order to provide water vapor to said gaseous flow passing through said humidification chamber means,

gaseous flow transportation pathway means connected to said outlet of said humidification chamber means to convey said gaseous flow to said patient or other person in need of such gaseous flow,

flow probe means adapted to sense the flow rate of said gaseous flow,

temperature sensing means adapted to sense the temperature of said gaseous flow,

user input means to allow a user to select a desired gaseous flow humidity level of said gaseous flow,

data storage means containing information on target gaseous flow temperatures at various gaseous flow rates for a number of humidification chamber outlet means temperatures,

control means which receives input from said temperature sensing means and said user input means and using said flow information from said flow probe means repeatedly obtains corresponding target temperature information from said data storage means corresponding to the desired gaseous flow humidity level and varies the heat provided by said heating means until the sensed temperature is substantially equivalent to said target temperature in order to obtain said desired gaseous flow humidity level,

wherein said flow probe means comprising;

sensor housing means adapted for positioning in said gaseous flow, said sensor housing means having a longitudinal axis substantially perpendicular to said humidified gaseous flow and a sensing end,

sensing means housed within said sensor housing means at or near said sensing end, and

at least two projecting tab means extending laterally from said sensor housing means, oppositely positioned around said sensor housing means and aligned parallel to said gaseous flow, wherein liquid condensate is dispersed along the lines of intersection between said sensor housing means and said at least two tab means away from said sensing end of said sensor housing means, there existing a localized area of low surface tension along said lines.

17. Humidification apparatus as claimed in claim 16 wherein said gaseous flow transportation pathway means includes a heating wire means adapted to, upon energization to a setting determined by said control means, supply heat to said gaseous flow between said humidification means outlet and said patient or other person in need to such gaseous flow and wherein said control means thereby controls temperature changes in said gaseous flow along said gaseous flow transportation pathway, said control means adjusting said setting of said heating wire to control the temperature of said gaseous flow delivered to said patient or other person in need of such gaseous flow to a user set desired temperature.

18. Humidification apparatus as claimed in claims 16 or 17 wherein said flow probe means comprise two sensor housing means, a temperature sensor housing means and a flow rate sensor housing means, each comprising a temperature dependent resistance,

and wherein said sensing means of said flow rate sensor housing means is occasionally heated to a predetermined difference temperature above the temperature of said gaseous flow, the power required by said sensor means of said flow rate sensor housing means to maintain said predetermined difference temperature providing an indication of the flow rate of said gaseous flow,

and wherein said sensing means of said flow rate sensor housing means is exposed at or near the sensing end of the flow rate sensor housing means up stream of and spaced across said gaseous flow from the sensing means of said temperature sensor housing means is encapsulated at or near the sensing end of the temperature sensor housing means, in order that heat produced by the sensing means of said flow rate sensor housing means does not effect the sensing means of said temperature sensor housing means.

19. Humidification apparatus as claimed in claims 16 or 17 wherein said gaseous flow transportation pathway means has a known cross-sectional area, at least in the region adjacent said flow probe means, and is provided with a sensor entry port adapted to receive said flow probe means, said sensor entry port being provided with a fixed locating depression and said flow probe means being provided with a complimentary fixed locating tooth, the positioning of said temperature and flow rate sensor housing means relative to said gaseous flow being controlled by the interconnection of said locating depression and tooth.

20. Humidification apparatus for humidifying a gaseous flow to be supplied to a patient or other person in need of such gaseous flow comprising:

humidification chamber means adapted to hold a quantity of water and having an inlet and an outlet to allow said gaseous flow to pass through said humidification chamber means,

heating means provided adjacent said humidification chamber means and adapted to provide heat to said quantity of water in said humidification chamber means in order to provide water vapor to said gaseous flow passing through said humidification chamber means,

gaseous flow transportation pathway means connected to said outlet of said humidification chamber means to convey said gaseous flow to said patient or other person in need of such gaseous flow,

flow probe means adapted to sense the flow rate of said gaseous flow, and

control means configured to receive input from said flow probe means and configured to compare the sensed flow rate of said gaseous flow with a predetermined minimum required gaseous flow rate and configured to place the humidification apparatus into a safe mode of operation if the sensed rate is less than said predetermined minimum rate, said safe mode including conditional logic which is configured to choose between a predetermined set of actions at least relating to the energization of said heating means.

21. Humidificaion apparatus as claimed in claim 20 wherein said predetermined minimum requried gaseous flow rate is about 1.5 liters per minute.

22. Humidification apparatus as claimed in claim 20 or claim 21 wherein heating plate temperature sensing means are also provided and said set of actions includes said control means energizing said heating means in such a way as to ensure that the temperature of said heating means does not exceed a predetermined maximum temperature.

23. Humidification apparatus as claimed in claim 20 or claim 21 wherein said set of actions includes said control means limiting the power supplied to said heating means to a predetermined maximum level.

24. Humidification apparatus for humidifying a gaseous flow to be supplied to a patient or other person in need of such gaseous flow comprising:

humidification chamber means adapted to hold a quantity of water and having an inlet and an outlet to allow said gaseous flow to pass through said humidification chamber means,

heating means provided adjacent said humidification chamber means and adapted to provide heat to said quantity of water in said humidification chamber means in order to provide water vapor to said gaseous flow passing through said humidification chamber means,

gaseous flow transportation pathway means connected to said outlet of said humidification chamber means to convey said gaseous flow to said patient or other person in need of such gaseous flow,

flow probe means adapted to sense the flow rate of said gaseous flow, and

control means which receives input from said flow probe means and compares the sensed flow rate of said gaseous flow with a predetermined minimum required gaseous flow rate and places the humidification apparatus into a safe mode of operation if the sensed rate is less than said predetermined minimum rate

wherein said flow probe means comprises;

sensor housing means adapted for positioning in said gaseous flow, said sensor housing means having a longitudinal axis substantially perpendicular to said humidified gaseous flow and a sensing end,

sensing means housed within said sensor housing means at or near said sensing end, and

at least two projecting tab means extending laterally from said sensor housing means, oppositely positioned around said sensor housing means and aligned parallel to said gaseous flow, wherein liquid condensate is dispersed along the lines of intersection between said sensor housing means and said at least two tab means away from said sensing end of said sensor housing means, there existing a localized area of low surface tension along said lines of intersection.

25. Humidification apparatus as claimed in claim 24 wherein said predetermined minimum required gaseous flow rate is about 1.5 liters per minute.

26. Humidification apparatus as claimed in claim 24 or 25 wherein said flow probe means comprise two sensor housing means, a temperature sensor housing means and a flow rate sensor housing means, each comprising a temperature dependent resistance,

and wherein said sensing means of said flow rate sensor housing means is occasionally heated to a predetermined difference temperature above the temperature of said gaseous flow, the power required by said sensor means of said flow rate sensor housing means to maintain said predetermined difference temperature providing an indication of the flow rate of said gaseous flow,

and wherein said sensing means of said flow rate sensor housing means is exposed at or near the sensing end of the flow rate sensor housing means up stream of and spaced across said gaseous flow from the sensing means of said temperature sensor housing means is encapsulated at or near the sensing end of the temperature sensor housing means, in order that heat produced by the sensing means of said flow rate sensor housing means does not effect the sensing means of said temperature sensor housing means.

27. Humidification apparatus as claimed in claims 24 or 25 wherein said gaseous flow transportation pathway means has a known cross-sectional area, at least in the region adjacent said flow probe means, and is provided with a sensor entry port adapted to receive said flow probe means, said sensor entry port being provided with a fixed locating depression and said flow probe means being provided with a complimentary fixed locating tooth, the positioning of said temperature and flow rate sensor housing means relative to said gaseous flow being controlled by the interconnection of said locating depression and tooth.