Controlling flow of exhaled breath during analysis

Abstract

The flow rate of a gaseous sample of exhaled breath through an analytical device is controlled by a pump, and in certain embodiments two pumps. Placement of the analyte sensor in a secondary stream branching off of the primary stream through the device offers further control over the manner, duration, and quantity of the breath that is placed in contact with the sensor.

1 - 14 . (canceled) 
     
     
         15 . An apparatus for detecting an analyte in exhaled breath, said apparatus comprising a housing having a flow-through passage and adapted to receive exhaled breath from a subject, an analyte sensing element responsive to said analyte retained in said flow-through passage, and pump means for drawing said exhaled breath from a subject and through said flow-through passage at a controlled rate. 
     
     
         16 . The apparatus of  claim 15  wherein said pump means is downstream of said analyte sensing element in said flow-through passage. 
     
     
         17 . The apparatus of  claim 15  further comprising a pressure sensor arranged to detect the pressure of exhaled breath entering said flow-through passage. 
     
     
         18 . The apparatus of  claim 15  further comprising flow resistance means in said conduit. 
     
     
         19 . The apparatus of  claim 15  wherein said flow-through passage comprises a primary passage and a secondary passage branched off from said primary passage. 
     
     
         20 . The apparatus of  claim 19  wherein said analyte sensing element is in said secondary passage. 
     
     
         21 . The apparatus of  claim 19  wherein said flow-through passage divides into said primary passage and said secondary passage at an upstream junction in said flow-through passage and said secondary passage recombines with said primary passage at a downstream junction in said flow-through passage. 
     
     
         22 . The apparatus of  claim 19  wherein said flow-through passage divides into said primary passage and said secondary passage at an upstream junction in said flow-through passage and said primary and secondary passages are vented separately. 
     
     
         23 . The apparatus of  claim 21  wherein said pump means comprises a single pump downstream of said downstream junction. 
     
     
         24 . The apparatus of  claim 19  wherein said pump means comprises a first pump in said primary passage and a second pump in said secondary passage. 
     
     
         25 . The apparatus of  claim 21  wherein said pump means comprises a first pump in said primary passage and a second pump in said secondary passage. 
     
     
         26 . The apparatus of  claim 19  further comprising a shut-off valve arranged to allow or prevent flow through said secondary passage. 
     
     
         27 . The apparatus of  claim 19  further comprising a check valve in said side passage. 
     
     
         28 . The apparatus of  claim 18  wherein said flow resistance means is an orifice. 
     
     
         29 . The apparatus of  claim 18  wherein said flow resistance means is a variable flow resistor. 
     
     
         30 . The apparatus of  claim 19  further comprising a first flow resistor in said primary passage and a second flow-resistor in said secondary passage. 
     
     
         31 . The apparatus of  claim 30  wherein said first flow resistor is a variable flow resistor. 
     
     
         32 . A method for determining the amount of an analyte in exhaled breath from a subject, said method comprising drawing exhaled breath from said subject through a flow-through device at a constant flow rate by use of a pump integrated with said flow-through device, said flow-through device comprising a sensing element responsive to said analyte. 
     
     
         33 . The method of  claim 32  further comprising detecting the pressure of exhaled breath thus drawn into said flow-through device. 
     
     
         34 . The method of  claim 32  wherein said flow-through device comprises a primary passage and a secondary passage with said sensing element in said secondary passage, and said method further comprises dividing exhaled breath thus drawn into said flow-through device into a primary stream through said primary passage and a secondary stream through said secondary passage. 
     
     
         35 . The method of  claim 34  comprising drawing said exhaled breath through said primary passage and said secondary passage by a single pump. 
     
     
         36 . The method of  claim 34  comprising drawing said exhaled breath through said primary passage and said secondary passage by a separate pump in each of said passages. 
     
     
         37 . The method of  claim 34  wherein said flow-through device comprises a shut-off valve in said secondary stream, and said method further comprises retaining a sample of said exhaled breath in contact with said sensing element in said secondary stream for a selected period of time. 
     
     
         38 . The method of  claim 34  comprising drawing said exhaled breath through said secondary stream at a flow rate of 5 cm 3 /s to 11 cm 3 /s. 
     
     
         39 . The method of  claim 34  comprising drawing said exhaled breath through said primary stream at a flow rate of 40 cm 3 /s to 45 cm 3 /s. 
     
     
         40 . The method of  claim 37  further comprising opening said shut-off valve to allow flow through said secondary passage at an interval of between 5 seconds and 9 seconds after the start of flow of exhaled breath through said device. 
     
     
         41 . The method of  claim 40  further comprising maintaining said flow through said secondary passage for a duration of between 1 second and 10 seconds.