When you breathe, your lungs inhale oxygen and exhale carbon dioxide (CO2). Too much or too little CO2 in your breath at the end of an exhalation is a sign that you are not breathing adequately, or that your lungs are not getting enough blood flow.

Continuous end-tidal CO2 monitoring is almost always done in a hospital setting. During the treatment, a machine (capnometer) measures how much CO2 you exhale with each breath. The results are shown as a graph and a number. There are several types of end-tidal CO2 devices.

You may have end-tidal CO2 monitoring if:

  • You have a sudden (acute) or long-term (chronic) breathing problem and your health care provider needs more information about how well you are breathing.

  • You have surgery.

  • You have tubes placed in your nostrils to help you breathe (nasal cannula).

  • You have a tube placed in your windpipe to help you breathe (endotracheal tube).

  • You are given medicines to help you relax (sedatives), or medicines that can cause a slow breathing rate.

  • You are being treated for a serious illness, such as a heart attack, severe infection, lung problem, seizure, head injury, or overdose.

Tell a health care provider about:

  • Any allergies you have.

  • All medicines you are taking, including vitamins, herbs, eye drops, creams, and over-the-counter medicines.

  • Any problems you or family members have had with anesthetic medicines.

  • Any bleeding problems you have.

  • Any surgeries you have had.

  • Any medical conditions you have.

  • Any breathing problems you have had.

  • Any history of smoking you have.

What are the risks?

Generally, this is a safe procedure. However, problems may occur, including:

  • False readings from the monitor.

  • Moving your endotracheal tube or nasal cannula out of place, if applicable.

What happens before the procedure?

If you are awake and alert before your procedure, your health care provider will explain how the procedure works. If the procedure is done during an emergency or at a time when you are not alert and awake, your health care provider may explain the procedure to a family member.

What happens during the procedure?

  • Your health care provider will check the monitor to make sure it works properly.

  • If you are able to breathe on your own, your health care provider will attach a type of nasal cannula to the capnometer. This nasal cannula has prongs that sit just inside of your nostrils. You can breathe in oxygen through the cannula, and it will capture the CO2 you exhale through a special device that connects to the capnometer.

  • If you are breathing through an endotracheal tube, your health care provider will place an attachment (airway adapter) into the breathing tube that comes from the endotracheal tube. The airway adapter will capture CO2 and send it to the capnometer.

    • This type of monitoring is usually done for people who are not awake or alert, such as people under sedation.

  • You will continue to have CO2 monitoring until your health care provider feels that it is no longer necessary. If you have monitoring done during a procedure, it may be stopped after you recover.

These procedures may vary among health care providers and hospitals.

What happens after the procedure?

You and your health care provider will discuss what your results mean.

  • If your results show that you are not exhaling enough CO2 (you have elevated CO2 levels), you may receive more oxygen or more help with breathing and circulation. This may involve:

    • Having an endotracheal tube placed or replaced.

    • Being placed on different types of oxygen delivery devices, such as BIPAP (bi-level positive airway pressure) or CPAP (continuous positive airway pressure) devices. These devices blow air through the nose or mouth and into the air passages to help you breathe.

    • Taking medicines.

  • If your condition is normal, or has improved, you may no longer need CO2 monitoring.

Summary

  • When you breathe, your lungs inhale oxygen and exhale carbon dioxide (CO2). Too much CO2 in your breath at the end of an exhalation may be a sign of poor ventilation or poor circulation.

  • End-tidal CO2 monitoring is a way of continually measuring the amount of CO2 you are exhaling.

  • You may have end-tidal CO2 monitoring to help diagnose a breathing problem or to monitor ongoing treatments.

  • If this procedure shows that you are not exhaling enough CO2 (you have elevated CO2 levels), you may need more oxygen or more help with breathing, such as BIPAP or CPAP devices.

  • You and your health care provider will discuss what your results mean.

This information is not intended to replace advice given to you by your health care provider. Make sure you discuss any questions you have with your health care provider.