Hypocapnia

• No ETCO2
Timing? Never or suddenly absent
Concurrent events? Surgical, anaesthetic or change in position
• Low ETCO2
Timing? Always low, suddenly low or falling
Concurrent events?

No ETCO2

• Oesophageal intubation
• Accidental extubation
• Disconnection
• Equipment failure ­ has the machine and monitor been checked prior to induction?
• Cardiac arrest

Low ETCO2

• Airway
• Circuit
• Ventilation
• Gas exchange
• Decreased production

Airway

• Oesophageal intubation
• Accidental extubation

Circuit

• Air entrainment (leak)
• Dilution with circuit gases (sampling problem)

Ventilation

• Ventilation settings
• Overenthusiastic hand ventilation
• Metabolic acidosis ­ spontaneously ventilating patient

Gas Exchange

• Pulmonary embolism
Air
Clot
Fat
Other
• Decreased cardiac output/arrest
• Severe hypotension

Decreased Production

• Hypothermia
• Hypothyroidism
• Decreased Metabolism