Dräger Atlan Quick Reference Manual page 40

Principles of operation
9.2.2 Optimization of the sample gas quality
In the case of an unusual waveform shape or if distortion of the measured etCO
suspected, changing the sampling site and using a heat and moisture exchanger (HME) can
be helpful.
Use only pure HMEs with a small volume for this which are listed in the list of accessories.
Do not use fine-pored filters or HME filters, as undesired blockages (e.g., caused by
sputum) occur more abruptly with these than with pure HMEs. These blockages would
immediately cause negative pressure in the lungs.
No
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Taking the gas sample as close to the patient as possible and using an HME if necessary
has the following advantages (among others):
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A blockage or soiling of the HME (e.g., caused by sputum) can have the following effects in
the previously described configuration:
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Designation
Inspiration
Expiration
HME
Gas sampling
Optimization of the sample gas quality due to reduction of ventilation influences, e.g.,
turbulence at the Y-piece
Less distortion of the CO
Less distortion of the measured etCO
The undesired influence of the dead space between the Y-piece and the sampling site is
reduced. At the end of the expiration, the dead space already contains fresh inspiratory
gas for the next breath.
Increase of the HME resistance
Negative pressure in the patient's lungs
Increasing air trapping (detectable in the flow waveform as an incomplete expiration
before the start of the next inspiration)
waveform
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values
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Quick reference guide
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values is
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Atlan SW 2.0n