Hypercapnia: symptoms, causes, diagnosis and treatment


Hypercapnia is an excessive accumulation of carbon dioxide (CO2) in the body. The condition, also described as hypercapnia, hypercapnia, or carbon dioxide retention, can lead to effects such as headaches, dizziness, and fatigue, as well as serious complications such as seizures or loss of consciousness.

Hypercapnia can develop as a complication of chronic lung diseases such as COPD , bronchiectasis , emphysema , interstitial lung disease, and cystic fibrosis , as well as certain neurological and muscle diseases.

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Your CO2 level can be measured with a blood sample, and you may also need other diagnostic tests to determine the cause of your hypercapnia. Usually this problem requires intervention with medications and / or respiratory assistance, such as a respiratory mask or a ventilator.


Hypercapnia often does not cause obvious effects, and most people do not notice or complain about symptoms.

Common symptoms of hypercapnia, if they occur, include:

  • Fatigue
  • Inability to concentrate or think clearly.
  • Headache
  • Redness
  • Dizziness
  • Difficulty breathing (shortness of breath)
  • Tachypnea (rapid breathing)
  • High blood pressure

Because these effects are so vague, you may not know they are caused by hypercapnia. Some people with lung disease measure their own oxygen levels at home with a pulse oximeter , but this device cannot detect hypercapnia.

Your CO2 level may be too high even if you have normal oxygen levels.

When you have a chronic respiratory disease, CO2 levels may rise slightly or they may rise gradually over the years as the disease progresses. There may also be sudden episodes of hypercapnia during an exacerbation of lung disease.

CO2 levels in your blood can rise dramatically if you develop a severe lung infection, especially if you already have a chronic lung disease such as chronic obstructive pulmonary disease (COPD).


Severe hypercapnia can cause noticeable and unpleasant consequences. You may experience sudden respiratory failure , which can lead to coma and even death.

Serious and urgent symptoms of hypercapnia can include :

  • Paranoia, depression and confusion.
  • Muscle spasms
  • Seizures
  • Palpitations (sensation of fast heartbeat)
  • Panic or feeling of impending doom
  • Dilation (dilation) of the superficial veins of the skin.
  • Swelling of the optic nerve (swelling of the optic nerve)

Seek emergency medical attention if you experience any of these.


CO2 is a gas that is produced as a normal byproduct of your body's energy production. This gas enters the bloodstream and can be exhaled from the lungs. In a healthy person, the typical breathing rate and depth exhale CO2 from the body.

The amount of CO2 in the blood is carefully regulated. When CO2 levels rise, special receptors in your brain detect the increased level in your blood. These receptors send messages to your lungs, forcing you to breathe more deeply and / or at a faster rate until your CO2 levels reach normal levels.

Due to the mechanisms that regulate the level of CO2 in the body, a healthy person rarely develops medically significant hypercapnia.

When hypercapnia occurs, it can usually be the result of excess CO2 production or decreased CO2 respiration from the lungs. This can be due to health problems, and several risk factors increase the likelihood of this happening.

Metabolic changes

Serious illness, infection, and injury can cause metabolic disorders in the body, resulting in excessive CO2 production. If your breathing cannot meet the need to exhale CO2 from your body, you can develop elevated levels of CO2 in your blood.

Reasons for excess CO2 production include:

  • Serious illness, infection, or injury
  • Hypothermia (too low body temperature)
  • Diving (due to pressure drops)
  • Incorrect fan setting

Lung disease

Lung disease can interfere with the diffusion of CO2. A situation called ventilation / perfusion (V / Q) mismatch occurs when you have severe lung damage that prevents blood and / or air from flowing into your lungs. This inhibits the diffusion of CO2 and causes gas to build up in your body.

Examples include:

  • COPD
  • Emphysema
  • Interstitial lung disease (including pulmonary fibrosis)
  • Cystic fibrosis
  • Bronchiectasis

COPD is the leading cause of hypercapnia, although not all people with COPD, even severe or terminal COPD, will develop this problem.

Muscular weakness

Neuromuscular diseases such as amyotrophic lateral sclerosis (ALS) and muscular dystrophy can make it difficult to breathe, resulting in increased CO2 levels in the blood. Myasthenia gravis is another neuromuscular cause of hypercapnia.

Central hypoventilation

Conditions that disrupt your brain's regulation of respiration can lead to a build-up of CO2 in your blood. Your respiratory control may be affected due to a drug overdose, stroke, or degenerative brain disease, for example:


The diagnosis of hypercapnia begins with a complete medical history and physical examination. Your healthcare team can monitor you closely for signs of sudden hypercapnia, such as if you have a serious illness or during surgery.

In other cases, your team may have periodically monitored your CO2 levels for months or even years (for example, if you have chronic pulmonary fibrosis).

If you are at risk and / or have signs of hypercapnia, you will probably need a blood test to measure your CO2 levels. An arterial blood gas (ABG) test measures blood oxygen, CO2, bicarbonate, and pH.

Samples of blood drawn from a vein are generally used for blood tests. The ABG test requires a blood sample from your artery.

Hypercapnia is usually diagnosed when the CO2 pressure is 45 mmHg. Art. Or higher .

You may need to check your CO2 levels regularly, for example every few hours during treatment in an intensive care unit or every few minutes during surgery.

Diagnostic tests

In addition to analyzing your arterial blood gases, your healthcare team will also try to determine the cause of your hypercapnia. You may need a series of tests to help diagnose your condition.

They may include:

  • Pulse Oximetry: Your oxygen levels may be normal even if you have hypercapnia, but pulse oximetry is a non-invasive test that can be used to track sudden changes.
  • Blood tests: an increase in carbon dioxide in the blood also causes blood acidosis (a decrease in the pH of the blood). You can develop respiratory acidosis due to lung problems or metabolic acidosis due to illness.
  • Pulmonary function tests (PFTs): Various measures of your respiratory function can help your healthcare team assess your lung function. These include your vital capacity (the maximum amount of air that can be inhaled or exhaled from your lungs) and the forced expiratory volume in one second (FEV1).
  • Imaging tests: Tests such as chest x-rays and chest computed tomography (CT) can help assess the severity of lung conditions such as emphysema and pneumonia. If your healthcare provider is concerned about central hypoventilation, you may need brain imaging, such as magnetic resonance imaging (MRI).

Watch out

Hypercapnia can lead to respiratory failure and coma if left untreated. Treatment for this condition includes improving ventilation so that you can remove excess CO2. The type of treatment you need depends on the severity of your condition.

Treatment options may include:

  • Non -invasive ventilation: Non-invasive ventilation provides ventilation through the upper respiratory tract. A tight-fitting mask is placed on the face or nose. The mask is connected to a machine that provides slight pressure of air and oxygen from a flow generator, although you can still breathe on your own.
  • Intubation : intubation is an invasive process. An endotracheal tube is inserted into the mouth and lowered into the airway. You cannot voluntarily breathe or speak during intubation. You may need this type of respiratory support temporarily while you are treating a serious illness.
  • Artificial ventilation : When you are intubated, a tube that is placed in your mouth is connected to a mechanical ventilator that takes your breath away.

In addition to monitoring CO2 levels, your healthcare team will also need to provide medical care to treat the underlying cause of your condition. This can include treatments such as bronchodilators for COPD or antibiotics for infections.

Get the word of drug information

You generally think about oxygen levels when you have lung disease. But breathing problems can also affect your CO2 levels. Hypercapnia can also develop due to muscle and neurological disorders.

If you are at risk for hypercapnia, it is important to know the signs of the condition so that you can get medical help if your blood CO2 levels start to rise.

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