Thermistor based respiration measurement

Abstract

Various examples of methods and systems related to thermistor sensing for measurement of respiration are shown. In one example, a breath sensing system includes a self-heating temperature sensor that can be positioned in respiratory air of a subject and processing circuitry that can monitor operation of the self-heating temperature sensor. Respiratory information associated with physical or physiological properties of the subject can be communicated to a remotely located computing device. Electronic switching circuitry can be included to change operation of the self-heating temperature sensor between a temperature sensing mode and a heated power dissipation sensing mode. The processing circuitry can control switching between the modes. In another example, a method includes monitoring operational conditions of a self-heating temperature sensor positioned in respired air and determining, e.g., breath velocity, breath period, breath volume, breath carbon dioxide level, and heart rate based at least in part upon the operational conditions.

1 - 20 . (canceled) 
     
     
         21 . A gas sensing system, comprising:
 a self-heating temperature sensor configured to be positioned in a gas;   electronic switching circuitry operably connected to the self-heating temperature sensor, the electronic switching circuitry configured to change operation of the self-heating temperature sensor between a temperature sensing mode and a heated power dissipation sensing mode; and   processing circuitry configured to monitor operation of the self-heating temperature sensor and control switching between the temperature sensing mode and the heated power dissipation sensing mode, where the processing circuitry is configured to communicate gas compositional information to a remotely located computing device.   
     
     
         22 . The gas sensing system of  claim 21 , wherein the gas comprises water vapor, carbon dioxide, or a combination of water vapor and carbon dioxide. 
     
     
         23 . The gas sensing system of  claim 21 , wherein the self-heating temperature sensor is a thermistor. 
     
     
         24 . The gas sensing system of  claim 21 , wherein the self-heating temperature sensor is configured to be positioned in a gas. 
     
     
         25 . The gas sensing system of  claim 21 , wherein the self-heating temperature sensor is configured to be positioned in a static or flowing gas. 
     
     
         26 . The gas sensing system of  claim 21 , wherein the self-heating temperature sensor is heated to a defined temperature when the electronic switching circuitry is switched to the heated power dissipation sensing mode. 
     
     
         27 . The gas sensing system of  claim 21 , wherein the processing circuitry monitors, while in the heated power dissipation sensing mode, power demand of the self-heating temperature sensor. 
     
     
         28 . The gas sensing system of  claim 21 , wherein the processing circuitry is configured to determine gas compositional information based at least in part upon the monitored power demand. 
     
     
         29 . The gas sensing system of  claim 21 , comprising a power source electrically coupled to the electronic switching circuitry. 
     
     
         30 . The gas sensing system of  claim 21 , wherein the electronic switching circuitry comprises a startup circuit configured to initiate self-heating of the self-heating temperature sensor by energizing the self-heating temperature sensor at an increased voltage level for a predefined heating period. 
     
     
         31 . A method of detecting a gas or determining a property of a gas, the method comprising:
 contacting a gas sensing system with a gas, the gas sensing system comprising:
 a self-heating temperature sensor; 
 electronic switching circuitry operably connected to the self-heating temperature sensor, the electronic switching circuitry configured to change operation of the self-heating temperature sensor between a temperature sensing mode and a heated power dissipation sensing mode; and 
 processing circuitry configured to monitor operation of the self-heating temperature sensor and control switching between the temperature sensing mode and the heated power dissipation sensing mode, where the processing circuitry is configured to communicate information associated with compositional information of the gas to a remotely located computing device; 
   monitoring operational conditions of the self-heating temperature sensor positioned in the gas; and   determining at least one of the level of the gas or a property of the gas based at least in part upon the operational conditions of the self-heating temperature sensor.   
     
     
         32 . The method of  claim 31 , comprising determining the relative quantity of at least one of carbon dioxide or water vapor in the gas. 
     
     
         33 . The method of  claim 31 , wherein at least a portion of the operational conditions are monitored during operation of the self-heating temperature sensor in a heated power dissipation sensing mode. 
     
     
         34 . The method of  claim 31 , wherein the gas is static or flowing relative to the gas sensing system. 
     
     
         35 . The method of  claim 31 , wherein at least a portion of the operational conditions are monitored during operation of the self-heating temperature sensor in a temperature sensing mode. 
     
     
         36 . The method of  claim 31 , wherein the self-heating temperature sensor is switched between a temperature sensing mode and a heated power dissipation sensing mode during monitoring of the operational conditions. 
     
     
         37 . The method of  claim 31 , wherein compositional information of the gas is determined based at least in part upon the operational conditions of the self-heating temperature sensor. 
     
     
         38 . The method of  claim 31 , comprising communicating the compositional information of the gas for display on a user device. 
     
     
         39 . The method of  claim 31 , comprising transmitting the operational conditions of the self-heating temperature sensor to a remotely located computing device, where the compositional information of the gas is determined by the remotely located computing device. 
     
     
         40 . The method of  claim 31 , wherein the self-heating temperature sensor is a thermistor.