Respiratory humidification system

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 anesthetic 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).

1. Sensor probe means adapted for positioning in a flow of humidified gases comprising:
 sensor housing means adapted for positioning in said gases flow, said sensor housing means having a longitudinal axis substantially perpendicular to said humidified gases flow and a sensing end,  
 sensing means housed within said sensor housing means at or near said sensing end, and  
 at least one projecting tab means extending laterally from said sensor housing means, said at least one projecting tab means providing surfaces which enable liquid condensate to disperse away from said sensing end of said sensor housing means.  
 
     
     
       2. Sensor probe means as claimed in  claim 1  wherein said sensor probe means comprise two said projecting tab means. 
     
     
       3. Sensor probe means as claimed in  claim 1  or  claim 2  wherein said two projecting tab means are oppositely positioned around said sensor housing means. 
     
     
       4. Sensor probe means as claimed in  claim 1  or  claim 2  wherein each said at least one projecting tab means is aligned parallel to said gases flow. 
     
     
       5. Sensor probe means as claimed in  claim 1  or  claim 2  wherein liquid condensate is dispersed along the lines of intersection between said sensor housing means and said at least one tab means, there existing a localised area of low surface tension along said lines of intersection. 
     
     
       6. Sensor probe means as claimed in  claim 1  or  claim 2  wherein said sensor probe means comprise two sensor housing means, a temperature sensor housing means and a flow rate sensor housing means. 
     
     
       7. Sensor probe means as claimed in  claim 6  wherein said sensing means of said temperature sensor housing means and said flow rate sensor housing means each comprise a temperature dependent resistance. 
     
     
       8. Sensor probe means as claimed in  claim 6  wherein said sensing means of said flow rate sensor housing means is occasionally heated to a predetermined difference temperature above the temperature of said gases flow, and 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 gases. 
     
     
       9. Sensor probe means as claimed in  claim 6  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 while the sensing means of said temperature sensor housing means is encapsulated at or near the sending end of the temperature sensor housing means. 
     
     
       10. Sensor probe means as claimed in  claim 6  wherein said temperature and flow rate sensor housing means are spaced across said gases flow in order that heat produced by the sensing means of said flow rate sensor housing means has substantially minimal effect on the sensing means of said temperature sensor housing means. 
     
     
       11. Sensor probe means as claimed in  claim 6  wherein said flow rate sensor housing means is positioned up  down stream of said temperature senor 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. 
     
     
       12. Sensor probe means as claimed in  claim 1  or  claim 2    claim 6  wherein said gases flow is channelled within a conduit of known cross-sectional area, at least in the region adjacent said sensor probe means, and is provided with a sensor entry port adapted to receive said sensor probe means, said sensor entry port being provided with a fixed locating depression and said sensor probe means being provided with a complimentary fixed locating tooth, the positioning of said temperature and flow rate sensor housing means relative to said gases flow being controlled by the interconnection of said locating depression and tooth.