End-Tidal Capnography Periprocedural Care

Updated: Dec 15, 2015
  • Author: Christopher D Press, MD; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Periprocedural Care

Patient Education & Consent

Patient Instructions

Describe to the patient that you monitor their breathing and that it should not have any effect on them. Ask them to breathe normally.



See the list below:

  • End-tidal capnometer (fixed or portable)
  • Mainstream or sidestream sampling (see End-Tidal CO2 Detectors)
  • Nasal cannula or mask adaptors (nonintubated patients)

Patient Preparation

The patient needs to be in a position that both facilitates airway patency and allows adequate exposure for procedure being performed. Often the anesthesia provider and surgeon discuss which technique and position will minimize risk to the patient prior to the procedure.


Ideally the patient will be placed in a supine position for induction of general anesthesia and endotracheal intubation (see image below).

Esophageal intubation. Esophageal intubation.

The end-tidal capnometer must be prepped, calibrated and tested prior to use.


Airway Assessment

During standard pulmonary gas exchange, the respiratory tract introduces atmospheric oxygen into the bloodstream while at the same time removing carbon dioxide from the circulation. During endotracheal intubation or with use of an extra-glottic device (laryngeal mask airway), presence of consistent cyclical exhaled carbon dioxide confirms appropriate device positioning in the respiratory tract. Continuous capnography enables clinicians to constantly assess airway patency and gas exchange in real time.

In patients under monitored anesthetic care who do not require endotracheal intubation, end-tidal capnography via nasal or oral cannula may still be valuable for airway assessment. An increase in the partial pressure of end-tidal carbon dioxide can be an early warning sign for hypoxia.

Causes of end-tidal carbon dioxide changes are as follows:


Cardiopulmonary Resuscitation

During spontaneous circulation and breathing, the balance between production and elimination of carbon dioxide can be monitored by end-tidal capnography. In the event of cardiopulmonary arrest when cardiac output equals zero, no transport of carbon dioxide in the circulation and no elimination of carbon dioxide occurs. In this event, end-tidal capnometry decreases to 0.

Once cardiopulmonary resuscitation (CPR) is initiated, rescue breathing allows for elimination of carbon dioxide via manual pulmonary blood flow. End-tidal carbon dioxide monitoring can be a useful piece of information for CPR assessment, where a measure of 20 mm Hg or more indicates a perfusing blood flow. [9]