Fluidic volume-cycled respirator

Abstract

A fluidic, volume-cycled respirator circuit comprising a fluidic flowmeter, a tidal volume selection controller and an inlet valve. The flowmeter is connected to the controller through a transmitting means which transmits gas flow frequency signals. Said controller is then connected to the inlet valve, which is connected back to the flowmeter; hence, the respirator circuit is complete. The tidal volume selection controller may operate by either fluidics, electronics, or the combination of the two. The flowmeter facilitates supply of air to the patient. The amount of air supplied is controlled by the tidal volume selection controller which senses inspiration and gas flow frequency. The controller is equipped with a timer back-up system in the event that either the system or the patient fail to respond. The valve is operated at the direction of the tidal volume selection controller. The valve is open during the inspiratory phase and closed during the exhalation phase. The respirator herein overcomes the use of burdensome piston-bellows assemblies, has few moving parts and is relatively small in size. The use of piston-bellows assemblies is avoided by the use of a fluidic oscillator flowmeter.

We claim: 
     
       1. A fluidic volume-cycled respirator circuit which contains no piston-bellows assembly, said fluidic volume-cycled respirator comprising a breathing gas source;   an input valve connected to said breathing gas source;   a property independent fluidic oscillator flowmeter which is connected to said input valve and directly to a patient;   a means which transmits gas flow frequency signals from the flowmeter to a tidal volume selection controller;   a tidal volume selection controller which is connected to said means and to said input valve; and   a return transmitting line equipped with a pressure sensor running from the patient to said tidal volume selection controller.   
     
     
       2. A fluidic volume-cycled respirator circuit in accordance with claim 1, wherein said tidal volume selection controller is electronic. 
     
     
       3. A fluidic volume-cycled respirator circuit in accordance with claim 1, wherein said tidal volume selection controller comprises a frequency counter, a pressure switch, and a time-cycle timer. 
     
     
       4. A fluidic volume-cycled respirator circuit in accordance with claim 1, wherein said fluidic oscillator flowmeter is a true volume flowmeter. 
     
     
       5. A fluidic volume-cycled respirator circuit in accordance with claim 1, wherein said flowmeter has no moving parts. 
     
     
       6. A method for accommodating the complete respiratory needs of a patient wherein said method comprises providing a breathing gas source connected to a breathing gas inlet valve;   opening said gas inlet valve so as to allow breathing gas to be forced therethrough and subsequently through a property independent, fluidic oscillator flowmeter;   delivering said breathing gas exiting from said fluidic oscillator flowmeter directly to said patient;   monitoring the flow of said breathing gas by a transmitting means which transmits the oscillator frequency count of said breathing gas to a tidal volume controller;   closing said valve once a preset oscillator frequency count is reached;   sensing negative pressure produced by an inspiratory effort from said patient using a pressure sensor;   communicating said negative pressure to said total volume controller which instructs aid breathing gas inlet valve to open; and   repeating the breathing cycle; wherein said flowmeter converts the breathing gas flow rate to a frequency signal which is converted into said frequency counts by the use of said transmitting means; and wherein said tidal volume controller operates said breathing gas inlet valve causing said valve to close once said preset oscillator frequency count is reached.