Capnography

Measurement of exhaled carbon dioxide can be used to confirm ETT placement, for safer procedural sedation, to guide resuscitation, and to monitor cardiac & pulmonary physiology.

 • PETCO2 - End-tidal CO2 (what's measured by capnography)

 • PACO2 - Alveolar CO2

 • PvCO2 - Mixed venous CO2

 • PaCO2 - Arterial CO2 (what's measured on an ABG)

The Capnograph waveform is composed of 4 phases

 • Phase I — anatomical dead space ventilation

 • Phase II — dead space mixed with alveolar ventilation

 • Phase Ill — alveolar ventilation (where ETC02 measured)

 • Phase IV — end of exhalation

Specific capnograph patterns:

 • Downsloping phase III: copd

 • Curare cleft - patient dysynchrony during mechanical ventilation breath

 • Prolonged phase II/III: bronchospasm, airway obstruction, copd

 • Dimorphic phase II/III: right mainstem intubation, single lung transplant

 • Cardiac oscillations: hypovolemia, hypoventilation

 • Prominent phase IV: obesity

 • Sudden drop in ETCO2: arrythmia, pe



Nick Mark MD @nickmmark



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