Are COPD Patients at Risk for Hypercapnia?

copd, portable oxygen, hypercapnia, oxygen tips

Unfortunately, the answer is yes. Although not all people with COPD will develop hypercapnia, COPD is one of the major causes of hypercapnia. 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. The respiratory process is compromised when the alveoli are destroyed in those with COPD, damaging the alveoli’s ability to stretch and can potentially damage the walls between the alveoli. This damage affects the lung’s ability to take in oxygen, causing a reduction in the surface area required for oxygen to move from the lungs to the bloodstream, as well as for carbon dioxide to move from the bloodstream to the lungs for exhalation. Additionally, potential inflammation of the airways and trachea from COPD, combined with excess production of mucus, can further block airflow into and out of the lungs, which can also impact the body’s ability to get rid of carbon dioxide. Since 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 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]

For this reason, if you experience any of the conditions above, in addition to your COPD, talk to your doctor about the potential for increased risk of hypercapnia, as well as when to explore testing and treatment options.

Symptoms of Hypercapnia

People with mild hypercapnia may not even know they have it. It is common for people with a milder case of hypercapnia to experience a headache, dizziness, appear flushed and be warm to the touch. Left untreated, hypercapnia can progress to cause the following symptoms:[2]

  • Shortness of breath
  • Tachypnea (increased respiratory rate)
  • Increased blood pressure
  • Muscle tremor/twitching
  • Lethargy
  • Drowsiness
  • Seizure
  • Palpitations
  • Confusion
  • Paranoia
  • Depression or panic
  • Dilation of superficial veins in skin
  • Swelling in the area surrounding the optic nerves (visible on an eye exam and a sign of increased pressure in the brain)
  • Losing consciousness
  • Respiratory failure, coma and death (in severe cases)[3]

Diagnosis of Hypercapnia

Hypercapnia is usually diagnosed based on the results of an often in addition to a spirometer test. If a doctor suspects a patient has hypercapnia, they will test the patient’s breathing with a spirometer to ascertain how much air is in their lungs, as well as how forcefully the patient can blow into the device. The arterial blood gas test determines whether the patient’s oxygen pressure is within normal limits. A CO2 pressure of 45mm Hg or above is diagnostic of hypercapnia. Increased carbon dioxide in the blood will also lower the pH of the blood, causing acidosis, which could be an indication of hypercapnia as well. In addition, a doctor may also request a lung CT or an X-ray to check for emphysema and other lung conditions.

People with COPD should have a thorough medical history on file and should have regular physical exams to help diagnose hypercapnia early. If you have COPD and experience any of the symptoms associated with hypercapnia, contact your doctor right away for testing.

Treatment of Hypercapnia

Treatment of hypercapnia depends on its severity and, in the case of people with COPD, should be directed toward the underlying cause of the V/Q mismatch, as well as, increasing the amount of air moving into the alveoli (air sacs).[4] If the COPD was caused by exposure to chemicals, fumes or smoke, doctors will first recommend limiting exposure to the irritant. After that, hypercapnia treatment 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, as well as reducing 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.

People experiencing hypercapnia will need supportive care while the cause of the hypercapnia is determined. Once supportive care is established, doctors can determine which treatment option is necessary. Some supportive care treatments include prescribing medication like bronchodilators, corticosteroids or antibiotics to help patients breathe more easily in the interim before any ventilation begins. With early supportive care, it is possible to avoid the need for ventilation.

Additionally, since oxygen-induced hypercapnia can be a concern for those with COPD, a carefully monitored titrated oxygen therapy program is recommended to help reduce the risk. Talk to your doctor about how to establish the right oxygen therapy program for you to help reduce your symptoms and reduce the likelihood of complications.

When to Call the Doctor

If you have COPD, it is important to familiarize yourself with the symptoms of hypercapnia in order to help you recognize them should you ever experience them yourself. Early recognition of symptoms leads to earlier diagnosis and treatment, and can help you avoid respiratory failure. Early treatment of hypercapnia helps reduce the risk of intubation and mechanical ventilation, so call your doctor right away if you experience any of the hypercapnia symptoms listed above.

For more information about hypercapnia, or to seek diagnosis or treatment, 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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