Hypercapnia: What is it? Symptoms, Causes, Risk Factors, Diagnosis and Treatment

Also known as CO2 retention, it is a condition in which carbon dioxide is found at abnormally high levels in the blood.

Carbon dioxide is a gaseous product of the body’s metabolism and is usually expelled through the lungs.

It usually causes a reflex that increases breathing and access to oxygen. A failure of this reflex can be fatal, for example, contributing to the syndrome of sudden infant death.

Hypercapnia is the opposite of hypocapnia, the state of having abnormally reduced levels of carbon dioxide in the blood. The word comes from the Greek hyper = “up” or “too” and kapos = “smoke.”

Symptoms of hypercapnia

  • Reddened skin
  • Tachycardia
  • Dyspnoea,
  • Extrasystoles,
  • Muscle spasms,
  • Reduction of neuronal activity,
  • High blood pressure.

However, symptoms of mild hypercapnia may include: headache, confusion, and lethargy, as well as increased cardiac output, elevated arterial blood pressure, and a propensity for arrhythmias.

In cases of severe hypercapnia, there is disorientation, panic, hyperventilation, seizures, loss of consciousness, and eventually death.


There are many causes of hypercapnia, including the following:


Chronic obstructive pulmonary disease or COPD

COPD is a generic term for several conditions that affect breathing. Typical forms of COPD include chronic bronchitis and emphysema.

Chronic bronchitis causes inflammation and mucus in the airways, while emphysema involves damage to the lungs’ alveoli.

Both conditions can cause higher levels of carbon dioxide in the bloodstream.

The leading cause of COPD is prolonged exposure to lung irritants. According to the National Heart, Lung, and Blood Institute, cigarette smoke is the most common lung irritant that causes COPD in the United States.

Air pollution and exposure to chemicals or dust can also cause COPD.

Although not all people with COPD will develop hypercapnia, a person’s risk increases as their COPD progresses.

Sleep apnea

The National Sleep Foundation reports that between 5 and 20 percent of adults have sleep apnea.

This common condition is characterized by shallow breathing or pauses in breathing during sleep. It can interfere with the level of oxygen in the bloodstream and discard the balance of carbon dioxide and oxygen in the body.

Sleep apnea symptoms include daytime drowsiness, headaches upon awakening, and difficulty concentrating.


Rarely, a genetic condition in which the liver does not produce enough alpha-1-antitrypsin (AAT) can cause hypercapnia. Alpha-1 antitrypsin is a protein necessary for lung health, so AAT deficiency is a risk factor for the development of COPD.

Nervous disorders and muscle problems

The nerves and muscles needed for proper lung function may not work correctly in some people. For example, muscular dystrophy can cause muscles to weaken and eventually cause breathing problems.

Other disorders of the nervous or muscular systems that may contribute to hypercapnia include:

  • Encephalitis or when a person has inflammation of the brain.
  • An abnormal immune response can cause Guillain-Barré syndrome.
  • Myasthenia gravis a chronic disease that can weaken the skeletal muscles responsible for breathing.
Other causes

Other causes of high blood levels of carbon dioxide include:

  • Activities that affect breathing.
  • A brain stroke can affect breathing.
  • Hypothermia is a medical emergency caused by rapid loss of body heat.
  • Hypoventilation syndromes of obesity, when overweight people can not breathe profoundly or fast enough.
  • An overdose of certain medications, such as opioids or benzodiazepines.

Which are the risk factors

Some people are more at risk than others of developing hypercapnia, especially if:

  • Smoking: People who smoke, hefty smokers, have an increased risk of COPD, hypercapnia, respiratory difficulties, and lung diseases.
  • Asthma: As asthma causes the airways to become inflamed and constricted, it can affect breathing and carbon dioxide levels in the body when it is not well controlled.
  • Working with lung irritants: those who work with chemicals, dust, smoke, or other lung irritants have an increased risk of hypercapnia.
  • Having COPD: having COPD, especially if diagnosed at a later stage of disease progression, increases the likelihood of having hypercapnia.


Some tests used to diagnose hypercapnia include:

  • Blood gas test: checks the blood levels of carbon dioxide and oxygen.
  • Spirometer test: This test involves blowing into a tube to assess how much air a person can get out of their lungs and how fast they can do it.
  • X-ray or computed tomography: these imaging tests can verify the presence of lung damage and lung conditions.


Treatment for hypercapnia will depend on the severity of the condition and the underlying cause.

The options include:


There are two types of ventilation used for hypercapnia:

  • Non-invasive ventilation: breathing is assisted by a flow of air that comes through a mouthpiece or a nasal mask. This is useful for people with sleep apnea to keep the airway open at night, also known as CPAP or continuous positive pressure in the airways.
  • Mechanical ventilation: the person will have a tube inserted through the mouth into the airway. This is called intubation.

People with symptoms of severe hypercapnia can be placed in a ventilation device to help with breathing.


Certain medications can help to breathe, such as:

  • Antibiotics to treat pneumonia or other respiratory infections.
  • Bronchodilators to open the airways.
  • Corticosteroids reduce inflammation in the respiratory tract.
Oxygen therapy

People who undergo oxygen therapy regularly use a device to deliver oxygen to the lungs. This can help balance the levels of carbon dioxide in your blood.

Changes in lifestyle

To reduce symptoms and avoid complications, a doctor may recommend diet and physical activity changes. They will also encourage people with hypercapnia to avoid lung irritants by quitting and limiting their exposure to chemicals, dust, and fumes.


If the lungs or airways are damaged, surgery may be required. Options include lung volume reduction surgery to remove damaged tissue or a lung transplant in which a healthy lung replaces a damaged lung.