Are COPD Patients at Risk for Hypercapnia?

copd, portable oxygen, hypercapnia, oxygen tips Yes. Hypercapnia, also known as hypercarbia or CO2 retention, is a condition that occurs when there are elevated levels of carbon dioxide (CO2) in the blood.  CO2 is a by-product of metabolism and is usually removed from the body in sufficient amounts through the lungs when you exhale. Although it can be caused by a number of conditions including hypoventilation (breathing at an abnormally slow rate) and narcotic drug overdose, one of the most common causes of hypercapnia is chronic obstructive pulmonary disease (COPD).

Cause of Hypercapnia in COPD

Although some people attribute CO2 retention in COPD to hypoventilation, the most common cause of hypercapnia in COPD is a defect in the lungs called ventilation-perfusion (V/Q) mismatch. V/Q mismatch occurs when ventilation (the exchange of air between the lungs and the environment) and perfusion (the passage of blood through the lungs) are not evenly matched. When V/Q mismatch occurs, the transfer of all gases by the lungs – including anesthetic gases –is impaired.[1]

Other Causes of Hypercapnia

Besides hypoventilation and V/Q mismatch, there are a number of other conditions that can cause hypercapnia, including:[2]

Symptoms of Hypercapnia

People with mild hypercapnia may not even know they have it, or they may have a headache, appear flushed and be warm to the touch. Left untreated, hypercapnia can cause the following symptoms:[2]

  • Shortness of breath
  • Tachypnea (increased respiratory rate)
  • Muscle tremor/twitching
  • Lethargy
  • Drowsiness
  • Confusion
  • Paranoia
  • Respiratory failure, coma and death (in severe cases)[3]

Treatment of Hypercapnia

Treatment of hypercapnia depends on its severity and should be directed towards the underlying cause of the V/Q mismatch as well as increasing the amount of air moving into the alveoli (air sacs).[4] It most often involves either of the following:[5]

  • Non-invasive positive pressure ventilation (NIPPV): the application of positive pressure during the breathing cycle that keeps the airways open. The patient wears a tightly fitted facial or nasal mask that’s attached to a flow generator. Studies suggest that the application of NIPPV reduces the risk of intubation and premature death and the duration of intensive care unit or hospital stays.[6]
  • Intubation and mechanical ventilation: the process of inserting a special tube down the throat and into the airway. The tube then attaches to a mechanical ventilator that breathes for the patient until they’re able to breathe on their own.

When to Call the Doctor

If you have COPD, familiarizing yourself with the symptoms of hypercapnia will help you recognize them should you ever experience them yourself. Early recognition of symptoms leads to earlier diagnosis and treatment.  Early treatment of hypercapnia helps reduce the risk of intubation and mechanical ventilation.

For more information about hypercapnia, contact your primary care provider.

[1] West, JB. Causes of and compensations for hypoxemia and hypercapnia. Compr Physiol. 2011 Jul;1(3):1541-53. doi: 10.1002/cphy.c091007.
[2] Geiger-Bronsky, Michelle & Wilson, Donna J. eds. Respiratory Nursing: A Core Curriculum.New York, NY: Springer Publishing; 2008. ISBN: 798-082614444-7.
[3] Tran, Khoa MD. Carbon Dioxide Retention in Patients with Chronic Obstructive Pulmonary Disease. The Australian Lung Foundation.

[4] West JB. Causes of carbon dioxide retention in lung disease. N Engl J Med. 1971 Jun 3;284(22):1232-6. DOI: 10.1056/NEJM197106032842202.

[5] Feller-Kopman DJ, Schwartzstein RM. (2017). The evaluation, diagnosis, and treatment of the adult patient with acute hypercapnic respiratory failure. In: UpToDate, Stoller JK (Ed), UpToDate, Waltham, MA. 

[6] Budweiser, S., Jörres, R. A., & Pfeifer, M. (2008). Treatment of respiratory failure in COPD. International Journal of Chronic Obstructive Pulmonary Disease3(4), 605–618.

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