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Designed, Produced, and maintained (Edition 10, March 2019) by 

Bhavani Shankar Kodali MD

expiratory valves.

Expiratory Unidirectional valve

 

 Expiratory valve - Normal
 /images/Clinicalapplication/inspvalvemech.gif
/images/Clinicalapplication/valveexpnormal.gif

 

  Incompetent expiratory valve
 /images/Clinicalapplication/expvalvemech1.gif
 /images/Clinicalapplication/valveexp.gif

 

The capnogram shows prolonged phase II as well as slanting of descending limb of inspiratory segement. The expiratory unidirectional valve was noted to be fixed in the open position and thus allowing previously exhaled gases, high in CO2, to be rebreathed with each inspiration. The CO2 waveform returned to normal soon after the valve was removed, cleaned, dried, and replaced.

Reference:

Pyles, ST, Berman LS, Modell JH. Expiratory valve dysfunction in a semiclosed circle anesthesia circuit-verification by analysis of carbon dioxide waveform. Anesthesia Analgesia 1984;63:536-7.