Advantages of Buffered End-Tidal Breath Sampling
Our Buffered End-Tidal sampling setup has many advantages for real-time breath analysis. The test subject applies one exhalation through the buffer tube and then recedes from the sampler to continue normal breathing. The end-tidal part of the breath remains buffered in the tube and is slowly drawn into the instrument. With a buffer volume of about 30 ml, the time to analyze the end-tidal breath can be extended 10-20 fold to several seconds. Without this buffering the time to analyze the end-tidal fraction is only a few hundred milliseconds. This increase is especially important for quadrupol based PTR-MS instruments, since it allows analyzing more compounds from a single exhalation, but is also advantageous for PTR-TOFMS instruments: With this extended integration time, it is possible to analyze all compounds in a TOF spectrum down to single digit pptv-levels – from a single exhalation.
With BET sampling, the subject can breathe normally throughout most of the measurement. This is a more comfortable and for the subject and prevents hyperventilation. Moreover, the patients subjects do not have to inhale through the setup.
Non re-breathing mouthpieces
The test subjects come only into contact with the detachable mouthpiece. These are commercially available, cheap and disposable. They have a saliva trap to avoid droplets entering the buffer tube and feature a non-rebreathing mechanism. This is in-line with the BET sampling principle and renders an additional bacterial filter unnecessary, avoiding loss of compounds.
