Oral end tidal carbon dioxide probe for diagnosing pulmonary arterial hypertension

Abstract

This disclosure concerns improved capabilities for evaluating pulmonary arterial hypertension (PAH). A system and method of evaluating PAH in a subject may include measuring end tidal partial pressure of exhaled carbon dioxide in the subject, wherein the measurement is made orally using described systems or devices. Integrated sensors enable the measurement and characterization of other respiratory gas components, some of which may be indicative of disease. The system and method can be used to monitor a course of treatment for PAH.

What is claimed is: 
     
         1 . A system for determining whether additional medical tests need to be conducted for a diagnosis of a pulmonary arterial hypertension condition in a patient, comprising:
 i) a housing;   ii) a carbon dioxide analyzer located at least partially within the housing and adapted to measure the partial pressure of carbon dioxide in a composite gas;   iii) a conduit adapted to transfer an expiration from the patient's mouth to the carbon dioxide analyzer;   iv) a data transmitter adapted to transmit data from the carbon dioxide analyzer to a processor, the processor being located remotely from the housing and having a memory operably associated therewith;   v) a range of carbon dioxide partial pressure values stored in the memory;   vi) an indicator adapted to respond to a signal from the processor to provide an output in a human cognizable format, wherein the system:
 a) measures end tidal carbon dioxide (EtCO2) of each of a plurality of oral expirations from the patient at rest; 
 b) calculates a composite EtCO2 value for the plurality of oral expirations at rest; 
 c) compares the composite EtCO2 value to a range of carbon dioxide partial pressure values stored in the memory of the system; 
 d) generates a first signal based upon the comparison in step (c), the first signal indicative of whether additional medical tests need to be conducted for the diagnosis of pulmonary arterial hypertension; and 
 e) transmits the first signal to the indicator of the system. 
   
     
     
         2 . The system of  claim 1 , wherein the system further generates the first signal based upon the comparison in step (c) by determining that additional medical tests are needed in response to the composite EtCO2 value being lower than a first predetermined threshold value. 
     
     
         3 . The system of  claim 2 , wherein the first predetermined threshold value comprises 36 mmHg. 
     
     
         4 . The system of  claim 2 , wherein the first predetermined threshold value comprises a value between 28 mmHg and 38 mmHg, inclusive. 
     
     
         5 . The system of  claim 2 , wherein the system further generates the first signal based upon the comparison in step (c) by determining that additional medical tests are not needed in response to the composite EtCO2 value being greater than a second predetermined threshold value. 
     
     
         6 . The system of  claim 5 , wherein the second predetermined threshold value comprises 38 mmHg. 
     
     
         7 . The system of  claim 1 , wherein the carbon dioxide analyzer is calibrated for a precision of ±2 mm Hg up to 38 mm Hg for a partial pressure of carbon dioxide. 
     
     
         8 . The system of  claim 1 , wherein the carbon dioxide analyzer is calibrated for a precision of ±0.08% for every 1 mm Hg over 40 mm Hg for a partial pressure of carbon dioxide. 
     
     
         9 . The system of  claim 1 , wherein a lower range of the composite EtCO2 value is indicative of pulmonary arterial hypertension. 
     
     
         10 . The system of  claim 1 , wherein a lower range of the composite EtCO2 value is indicative of pulmonary arterial hypertension and a higher range of the composite EtCO2 value is indicative of pulmonary venous hypertension. 
     
     
         11 . A system for determining whether additional medical tests need to be conducted for a diagnosis of a pulmonary arterial hypertension condition in a patient, comprising the steps of:
 i) a housing;   ii) a carbon dioxide analyzer located at least partially within the housing and adapted to measure the partial pressure of carbon dioxide in a composite gas;   iii) a conduit adapted to transfer an expiration from the patient's mouth to the carbon dioxide analyzer;   iv) a first processor located within the housing and having a memory operably associated therewith;   v) a range of carbon dioxide partial pressure values stored in the memory; and   vi) an indicator adapted to respond to a signal from the processor to provide an output in a human cognizable format, wherein the system:
 a) measures end tidal carbon dioxide (EtCO2) of each of a plurality of oral expirations from the patient at rest with a device comprising: 
 b) calculates a composite EtCO2 value for the plurality of oral expirations at rest; 
 c) compares the composite EtCO2 value to a range of carbon dioxide partial pressure values stored in the memory of the device; 
 d) generates a first signal based upon the comparison in step (c), the first signal indicative of whether additional medical tests needs to be conducted for the diagnosis of pulmonary arterial hypertension; and 
 e) transmits the first signal to the indicator of the device. 
   
     
     
         12 . The system of  claim 11 , wherein the system further generates the first signal based upon the comparison in step (c) by determining that additional medical tests are needed in response to the composite EtCO2 value being lower than a first predetermined threshold value. 
     
     
         13 . The system of  claim 13 , wherein the first predetermined threshold value comprises 36 mmHg. 
     
     
         14 . The system of  claim 13 , wherein the first predetermined threshold value comprises a value between 28 mmHg and 38 mmHg, inclusive. 
     
     
         15 . The system of  claim 13 , wherein the system further generates the first signal based upon the comparison in step (c) by determining that additional medical tests are not needed in response to the composite EtCO2 value being greater than a second predetermined threshold value. 
     
     
         16 . The system of  claim 15 , wherein the second predetermined threshold value comprises 38 mmHg. 
     
     
         17 . The system of  claim 11 , wherein the carbon dioxide analyzer is calibrated for a precision of ±2 mm Hg up to 38 mm Hg for a partial pressure of carbon dioxide. 
     
     
         18 . The system of  claim 11 , wherein the carbon dioxide analyzer is calibrated for a precision of ±0.08% for every 1 mm Hg over 40 mm Hg for a partial pressure of carbon dioxide. 
     
     
         19 . The system of  claim 11 , wherein a lower range of the composite EtCO2 value is indicative of pulmonary arterial hypertension. 
     
     
         20 . The system of  claim 11 , wherein a lower range of the composite EtCO2 value is indicative of pulmonary arterial hypertension and a higher range of the composite EtCO2 value is indicative of pulmonary venous hypertension.