Outline four causes for the capnograph trace (shown below) obtained from a critically ill patient.

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College Answer

1. Ventilator disconnection
2. Esophageal intubation
3. Cardiac/respiratory arrest
4. Apnoea test in a brain dead patient
5. Capnograph obstruction

Discussion

Reasons for a flat or nearly flat CO2 trace include the following:

  • The patient is dead
  • Cardiac / respiratory arrest
  • Apnoea test in a brain dead patient
  • Oesophageal intubation has occurred
  • Ventilator disconnection
  • Airway obstruction (eg. patient suddenly bit down on the tube)
  • ETT perforation (the end tidal gas is escaping via the hole before it gets to the capnograph)
  • Capnograph disconnection or obstruction
  • Water droplet contamination of capnography module