Gas identification system and volumetrically corrected gas delivery system

Abstract

A gas delivery system, having a gas identification, by which a gas supplied to the gas delivery system is identified, a blender, blending oxygen and the gas to provide a gas mixture with an oxygen flow rate set up by an operator, and at least one flow sensor, to measure a flow rate of the gas mixture. The blender is driven by an actuator motor to various blender positions with the blender positions being calibrated based on the specific heat ratio and the gas constant of the gas. The flow sensor can be installed at the inspiratory circuit, the proximal circuit and the expiratory circuit of the gas delivery system. The flow sensor output is corrected based on the actual conditions, including the temperature, pressure and humidity, and characteristics of the gas mixture.

What is claimed is: 
     
         1 . A method of calibrating a blender applied to a gas delivery system, comprising:
 calculating an oxygen flow rate in air as a multiplication factor of air for a blender position based on a calculated oxygen flow rate in air;   deriving a volumetric flow ratio of a gas supplied to the blender to the air;   substituting the multiplication factor of air for a blender position with a multiplication factor of the gas derived from the volumetric flow ratio, a volume fraction of oxygen in the gas, and an oxygen flow rate of the gas; and   driving the blender to various positions according to an oxygen flow rate of a mixture of the gas and oxygen.   
     
     
         2 . The method according to  claim 1 , wherein the volumetric flow ratio is determined by gas constants and specific heat ratios for air and the gas. 
     
     
         3 . The method according to  claim 1 , wherein the gas comprises a heliox. 
     
     
         4 . The method according to  claim 1 , further comprising identifying the gas supplied to the blender using an electrical circuit comprising a voltage divider, wherein the gas is identified via a voltage drop. 
     
     
         5 . The method according to  claim 4 , further comprising referencing a lookup table comprising voltage drop values corresponding to various gasses. 
     
     
         6 . The method according to  claim 4 , further comprising detecting a flow rate of the mixture of the gas and oxygen after the blender using a flow sensor. 
     
     
         7 . The method of  claim 6 , wherein the flow sensor is separated from the voltage divider by the blender. 
     
     
         8 . The method according to  claim 6 , further comprising calibrating the flow sensor according to temperature, humidity, pressure, and composition of the gas. 
     
     
         9 . The method according to  claim 8 , further comprising calibrating the flow sensor according to viscosity of the gas when the flow rate is lower than a predetermined magnitude. 
     
     
         10 . The method according to  claim 6 , further comprising calibrating the flow sensor, comprising:
 deriving a standard volumetric flow for air with 21% of oxygen at ambient pressure and temperature;   converting the standard volumetric flow for air into a reference volumetric flow for air under body temperature and absolute pressure; and   multiplying the standard volumetric flow by a correction factor derived according to actual temperature, humidity, pressure, and a gas constant of the gas applied to the flow sensor.   
     
     
         11 . A method of calibrating a blender applied to a gas delivery system, comprising:
 calculating an oxygen flow rate in air as a multiplication factor of air for a blender position based on a calculated oxygen flow rate in air, wherein the blender is disposed between a gas identifier and a flow sensor;   deriving a volumetric flow ratio of a gas supplied to the blender to the air;   substituting the multiplication factor of air for a blender position with a multiplication factor of the gas derived from the volumetric flow ratio, a volume fraction of oxygen in the gas, and an oxygen flow rate of the gas; and   driving the blender to various positions according to an oxygen flow rate of a mixture of the gas and oxygen.   
     
     
         12 . The method according to  claim 11 , wherein the gas identifier comprises an electrical circuit having a voltage divider such that the gas is identified via a voltage drop. 
     
     
         13 . The method according to  claim 12 , further comprising referencing a lookup table comprising voltage drop values corresponding to various gasses. 
     
     
         14 . The method according to  claim 12 , further comprising detecting a flow rate of the mixture of the gas and oxygen after the blender using the flow sensor. 
     
     
         15 . The method according to  claim 14 , further comprising calibrating the flow sensor according to temperature, humidity, pressure, and composition of the gas. 
     
     
         16 . The method according to  claim 15 , further comprising calibrating the flow sensor according to viscosity of the gas when the flow rate is lower than a predetermined magnitude. 
     
     
         17 . The method according to  claim 14 , further comprising calibrating the flow sensor by deriving a standard volumetric flow for air with 21% of oxygen at ambient pressure and temperature; converting the standard volumetric flow for air into a reference volumetric flow for air under body temperature and absolute pressure; and multiplying the standard volumetric flow by a correction factor derived according to actual temperature, humidity, pressure, and a gas constant of the gas applied to the flow sensor. 
     
     
         18 . The method according to  claim 11 , further comprising determining the volumetric flow ratio by gas constants and specific heat ratios for air and the gas. 
     
     
         19 . The method according to  claim 11 , wherein the gas comprises a heliox.