Carbon dioxide-sensing airway products and technique for using the same

Abstract

An airway device is provided that may track the flow of respiratory gases through the device with sensing elements at a plurality of locations along the gas flow path of the device. Such a device may be useful for assessing a variety of clinical states, for adjusting patient ventilator settings, or for determining whether or not an airway device has been properly inserted into a patient airway.

What is claimed is: 
     
         1 . A method comprising:
 receiving signals from a first carbon dioxide sensor disposed at a first location on a patient breathing circuit and a second carbon dioxide sensor disposed at a second location on the patient breathing circuit;   determining a concentration of carbon dioxide gas over time at the first location;   determining a concentration of carbon dioxide gas over time at the second location;   determining a velocity of the carbon dioxide gas between the first location and the second location; and   determining a change in physiological dead space, wherein the change in physiological dead space is determined based on a volume of the breathing circuit between the first location and the second location, the concentration of carbon dioxide gas at the first location and the second location, and the velocity of the carbon dioxide gas between the first location and the second location.   
     
     
         2 . The method of  claim 1 , comprising determining from the change in the non-gas-exchanging physiologic volume that the patient has experienced a respiratory event. 
     
     
         3 . The method of  claim 1 , comprising determining from the change in the non-gas-exchanging physiologic volume that the patient has experienced a pulmonary embolism. 
     
     
         4 . The method of  claim 1 , comprising triggering an indicator if the change in the non-gas-exchanging physiologic volume is beyond a critical threshold. 
     
     
         5 . The method of  claim 4 , wherein the indicator comprises an alarm. 
     
     
         6 . The method of  claim 4 , wherein the indicator comprises instructions related to a treatment protocol. 
     
     
         7 . A medical device comprising:
 a conduit adapted to transfer a gas to or from a patient; and   a carbon dioxide sensor disposed along the conduit from a proximal end portion to a distal end portion, the proximal end portion being configured to extend out of the patient such that the carbon dioxide sensor extends out of the patient, wherein the carbon dioxide sensor is adapted to provide an indication of a carbon dioxide gas in the conduit at any given point between the proximal end portion and the distal end portion.   
     
     
         8 . The medical device of  claim 7 , wherein the conduit comprises a tracheal tube. 
     
     
         9 . The medical device of  claim 7 , comprising a ventilator to which the conduit is operatively connected. 
     
     
         10 . The medical device of  claim 7 , comprising a selective barrier disposed on the sensor that is substantially impermeable to water. 
     
     
         11 . The medical device of  claim 7 , comprising a temperature sensor adapted to provide signal related to a gas temperature, a humidity sensor, or an ambient pressure sensor. 
     
     
         12 . The medical device of  claim 7 , wherein the sensor comprises a chemical indicator. 
     
     
         13 . The medical device of  claim 7 , wherein the sensor comprises an electrochemical transducer. 
     
     
         14 . The medical device of  claim 7 , wherein the sensor comprises a non-optical transducer or an optical transducer. 
     
     
         15 . The medical device of  claim 7 , wherein the sensor comprises a quantum-restricted element. 
     
     
         16 . The medical device of  claim 7 , wherein the sensor comprises an elongate borosilicate substrate having an acrylic binder; and a carbon dioxide responsive indicator. 
     
     
         17 . The medical device of  claim 7 , wherein the sensor is disposed on an inside passage of the conduit. 
     
     
         18 . The medical device of  claim 7 , comprising a processor configured to:
 receive a first signal from the carbon dioxide sensor associated with a first location on the sensor and a second signal from the carbon dioxide sensor associated with a second location on the sensor;   determine a concentration of carbon dioxide gas over time at the first location;   determine a concentration of carbon dioxide gas over time at the second location;   determine a velocity of the carbon dioxide gas between the first location and the second location; and   determine a change in physiological dead space, wherein the change in physiological dead space is determined based on a volume of a breathing circuit between the first location and the second location, the concentration of carbon dioxide gas at the first location and the second location, and the velocity of the carbon dioxide gas between the first location and the second location.   
     
     
         19 . The medical device of  claim 7 , comprising a processor configured to:
 receiving a signal from the carbon dioxide sensor; and   determine if the device if the signal is associated with esophageal or tracheal carbon dioxide concentrations.   
     
     
         20 . The medical device of  claim 7 , wherein the sensor comprises a continuous strip from the proximal end portion to the distal end portion.