Does Mouth Breathing Affect My Oxygen Levels?

Pulse Oximetry
Does Mouth Breathing Affect Oxygen Saturation?. Photo courtesy of Getty Images, User David Becker

Question: Does Mouth Breathing Affect My Oxygen Levels?

Answer: Supplemental oxygen is generally prescribed to people whose partial pressure of oxygen (PaO2) as measured by arterial blood gases (ABGs) is less than or equal to 55 mg Hg and a documented oxygen saturation level of 88% or less while awake (or that drops to this level during sleep for at least 5 minutes).

Many patients receive in-home oxygen through an oxygen delivery device known as a nasal cannula.

This thin, plastic tube has two small prongs at one end that rest in the nostrils. The nasal cannula can comfortably deliver oxygen to a patient at 1 to 6 liters per minute (LPM), in concentrations ranging from 24% to 40 percent, depending upon how many LPM are being delivered. In comparison, room air contains about 21% oxygen, which is generally not enough for people with lung disease.

The Benefits of Supplemental Oxygen: Do Mouth Breathers Obtain Them?

By far, the greatest benefit of long-term oxygen therapy (LTOT) is that, when used at least 15 hours a day, it increases survival. But, are patients who use oxygen and breathe through their mouths able to derive the full benefit of oxygen therapy? Or, does mouth breathing result in low levels of oxygen in the blood, cells, and tissues?

Research involving this topic is contradictory as demonstrated by the following examples:

  • In a study involving 323 mouth-breathing subjects, researchers set out to determine the effect of mouth breathing on oxygen saturation. For the purpose of the study, mouth breathing was assessed by physical examination and questionnaires filled out by subjects or their partners. Oxygen saturation was measured by pulse oximetry. Results of the study found that 34.6% of the cases had normal oxygen saturation levels (95% or greater), 22.6% had an oxygen saturation level of 95% and 42.8% were considered hypoxic, with oxygen saturation levels below the set study limit of 95 percent. Researchers concluded that, while mouth breathing doesn't always result in hypoxia, it can contribute to it. 
  • Another study involving 10 healthy subjects compared aspirated gas samples of both open and closed-mouth breathers from the tip of a nasal cannula resting in the nasopharynx. The study concluded that not only did the delivered fraction of inspired oxygen (FIO2) increase with increasing oxygen flow rates but, compared to closed-mouth breathers, open-mouth breathers realized a significantly greater FIO2. However, in an editorial disputing the validity of the aforementioned study, Dr. Thomas Poulton, Chief Resident of the Bowman Gray School of Medicine's Department of Anesthesia, explains that gas samples taken from this area are not likely to be accurate because they contain only oxygen-enriched gas - not gas mixed with room air. Gas Samples taken from the trachea, which is further down the throat, would yield a more accurate gas concentration.

    Much ADO About Mouth Breathing: What Can You Do About It?

    The solution to mouth breathing is often dependent upon the underlying cause. Once accurately diagnosed, you can address treatment options which may include the following:

    • Clear your nasal passages - Some people have no choice but to breathe through their mouths because their nasal passages are blocked. A stuffy nose may be caused by allergies, illness, prior trauma or even weather changes. Over-the-counter antihistamines are available to keep allergy symptoms at bay and open up clogged nasal passages. Saline nasal spray is a natural alternative to medication and helps lubricate the nasal passages, often relieving congestion. If over-the-counter antihistamines and/or saline nasal sprays don't work for you, talk to your health care provider about using a prescription nasal spray such as Flonase.
    • Make an appointment with your dentist - Dentists are sometimes more knowledgeable than doctors when it comes to understanding mouth breathing. If your dentist determines that a facial or dental abnormality is the root of your mouth breathing, she may fit you with a functional device to help correct the problem.
    • Switch to a simple face mask - The easiest solution to mouth breathing, if medically appropriate, is to switch to a simple face mask. Generally, this is not very practical for many patients and must first be approved by your oxygen-prescribing health care provider. One alternative is to consider using the nasal cannula during the day, and switching to a simple face mask at night, so at least you'll be getting the full benefit of oxygen therapy during the hours in which you are asleep. Talk to your healthcare provider for more information about alternatives to the nasal cannula.
    • Nasal surgery - If your nasal passages are blocked because of a deviated septum, talking to an Ear, Nose and Throat (ENT) Specialist about surgery may help correct the problem allowing you to breathe better. Remember, people with COPD should be especially cautious when undergoing surgery, because of the potential post-operative complications associated with anesthesia.
    • Transtracheal oxygen therapy - Transtracheal oxygen therapy (TTOT) is a method of administering supplemental oxygen directly into the trachea (windpipe). As an alternative to the nasal cannula, it delivers up to 6 liters of oxygen per minute through a small, plastic tube called a catheter. TTOT is generally reserved for patients who have low blood oxygen levels that don't respond well to traditional methods of oxygen delivery.

      The Importance of Pulse Oximetry

      Whether you breathe through your mouth or nose, a pulse oximetry monitor is a must-have for any patient who receives in-home oxygen therapy. Pulse oximeters detect rapid changes in oxygen saturation levels providing you with a warning that you're low on oxygen. Compare prices on pulse oximetry monitors and never be in the dark about your oxygen saturation levels again.


      Chowanetz W., et. al. Efficacy of nasal O2 administration during mouth breathing. Dtsch Med Wochenschr. 1987 May 8;112(19):752-7.

      Naiki, EA., et. al. Evaluation of oxygen saturation by pulse-oximetry in mouth-breathing patients. Acta Med Iran. 2010 Jan-Feb;48(1):9-11.

      Poulton, Thomas J., MD. Assessing the Dose of Supplemental Oxygen: Let Us Compare Methodologies. Respiratory Care. Vol 50 No 5. May 2005.

      Wettstein, RB, et. al.  Delivered oxygen concentrations using low-flow and high-flow nasal cannulas. Respir Care. 2005 May;50(5):604-9.

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