Cpap respiratory apparatus

Abstract

The present invention discloses both a method of operating CPAP apparatus, and the apparatus itself in which a breathable gas delivery device, or mask ( 1 ), is connected to a gas supply pump ( 14 ) via a conduit which includes a restriction to gas flow such as a small bore portion ( 3 ). A pressure transducer ( 11 ) is used to sense the gas pressure at the patient's nose and the transducer output is used to servo-control the pump ( 14 ) to maintian the sensed pressure substantially constant.

1 . A CPAP respiratory apparatus comprising a breathable gas delivery device adapted to deliver breathable gas to inlet the of a patient's respiratory system, a breathable gas supply means having an outlet and arranged to supply breathable gas to said outlet at a pressure above atmospheric pressure, and a flexible conduit having an internal bore and being connected between outlet and said gas delivery device wherein a pressure transducer is connected to said device to sense the pressure at said respiratory system inlet, and a servo-controller is connected to both said gas supply means and said pressure transducer to adjust the operation of said gas supply means to maintain the pressure at said respiratory system inlet substantially constant.  
     
     
         2 . Apparatus as  claim 1 , wherein said gas delivery device comprises a nose mask.  
     
     
         3 . Apparatus as claimed in  claim 1 , wherein said flexible conduit includes a pressure drop inducing means.  
     
     
         4 . Apparatus as claimed in  claim 3 , wherein said pressure drop inducing means comprises at least that portion of said conduit closest to said gas delivery device which has an internal bore which is relatively small compared with the remainder of said conduit.  
     
     
         5 . Apparatus as claimed in  claim 4 , wherein said small bore portion is joined to the remainder of said conduit by a swivel joint.  
     
     
         6 . Apparatus as claimed in  claim 4 , wherein said small bore portion has a flattened non-circular profile.  
     
     
         7 . Apparatus as claimed in  claim 4 , wherein said small bore portion is arranged to pass between the eyes of said patient.  
     
     
         8 . Apparatus as claimed in  claim 6 , wherein said small bore portion is bifurcated and includes two parts which each extend from behind the head of said patient past the corresponding cheek to said gas delivery device.  
     
     
         9 . Apparatus as claimed in  claim 4 , wherein said small bore portion includes a pressure port and/or a transducer cable.  
     
     
         10 . Apparatus as claimed in  claim 3 , wherein said pressure drop inducing means is selected from the class consisting of a bend in said conduit, a swivel joint in said conduit, a pressure transducer, a humidifier, a filter, baffle means, a flow measuring orifice and an adapter to connect portions of said conduit of different effective internal diameters.  
     
     
         11 . A method of operating a breathable gas supply means of a CPAP respiratory apparatus comprising a breathable gas delivery device adapted to deliver breathable gas to the inlet of a patient's respiratory system and connected by a flexible conduit to an outlet of said gas supply means to receive breathable gas therefrom at a pressure above atmospheric pressure, said method comprising the steps of sensing the pressure supplied to said respiratory system inlet by said gas delivery device, and using the sensed pressure to servo-control said gas supply means to maintain pressure at said respiratory system inlet substantially constant.  
     
     
         12 . A method as claimed in  claim 11 , wherein said gas delivery device comprises a nose mask having a nose receiving cavity, and said sensed pressure is the pressure within said cavity.  
     
     
         13 . A method as claimed in  claim 11 , including the step of locating a pressure drop inducing means in said conduit.