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Dual Plateau capnogram caused by cracked sample filter
A dual plateau capnogram was observed by Body et al during anesthesia and IPPV. They found that the cause of the abnormality was due a microscopic crack in the filter membrane separator cartridge of the Ohmeda RGM 5250 gas analyzer. The authors hypothesized that, during the initial phase of expiration, aspiration of the gas sample by the analyzer produced a negative pressure at the cracked sample filter that aspirated room air. With the commencement of inspiration, positive pressure in the anesthesia circuit reduced the negative pressure at the sample filter and eliminated or reduced the aspiration of the ambient air, thus allowing, a second plateau more accurately reflected alveolar PCO2.
(Provided by Simon Body and James Philips)
Body et al. Dual Plateau capnogram caused by cracked sample filter. Anesth Analg 2000;Jan:233-34 (with permission).
Zuspan J, Martin M, Benumof JL. End-tidal CO2 excretion waveform and error with gas sampling line leak. Anesth Analg 1988;67:81.