What is respiratory acidosis?

Respiratory acidosis is a condition that occurs when the lungs can’t remove enough of the carbon dioxide (CO2) produced by the body. Excess CO2 causes the pH of blood and other bodily fluids to decrease, making them too acidic. Normally, the body is able to balance the ions that control acidity. This balance is measured on a pH scale from 0 to 14. Acidosis occurs when the pH of the blood falls below 7.35 (normal blood pH is between 7.35 and 7.45).

Respiratory acidosis is typically caused by an underlying disease or condition. This is also called respiratory failure or ventilatory failure.

Normally, the lungs take in oxygen and exhale CO2. Oxygen passes from the lungs into the blood. CO2 passes from the blood into the lungs. However, sometimes the lungs can’t remove enough CO2. This may be due to a decrease in respiratory rate or decrease in air movement due to an underlying condition such as:

There are two forms of respiratory acidosis: acute and chronic.

Acute respiratory acidosis occurs quickly. It’s a medical emergency. Left untreated, symptoms will get progressively worse. It can become life-threatening.

Chronic respiratory acidosis develops over time. It doesn’t cause symptoms. Instead, the body adapts to the increased acidity. For example, the kidneys produce more bicarbonate to help maintain balance.

Chronic respiratory acidosis may not cause symptoms. Developing another illness may cause chronic respiratory acidosis to worsen and become acute respiratory acidosis.

Initial signs of acute respiratory acidosis include:

  • headache
  • anxiety
  • blurred vision
  • restlessness
  • confusion

Without treatment, other symptoms may occur. These include:

  • sleepiness or fatigue
  • lethargy
  • delirium or confusion
  • shortness of breath
  • coma

The chronic form of respiratory acidosis doesn’t typically cause any noticeable symptoms. Signs are subtle and nonspecific and may include:

  • memory loss
  • sleep disturbances
  • personality changes

The lungs and the kidneys are the major organs that help regulate your blood’s pH. The lungs remove acid by exhaling CO2, and the kidneys excrete acids through the urine. The kidneys also regulate your blood’s concentration of bicarbonate (a base).

Respiratory acidosis is usually caused by a lung disease or condition that affects normal breathing or impairs the lungs’ ability to remove CO2. Some common causes of the chronic form are:

Some common causes of the acute form are:

  • lung disorders (COPD, emphysema, asthma, pneumonia)
  • conditions that affect the rate of breathing
  • muscle weakness that affects breathing or taking a deep breath
  • obstructed airways (due to choking or other causes)
  • sedative overdose
  • cardiac arrest

The goal of diagnostic tests for respiratory acidosis is to look for any pH imbalance, to determine the severity of the imbalance, and to determine the condition causing the imbalance. Several tools can help doctors diagnose respiratory acidosis.

Blood gas measurement

Blood gas is a series of tests used to measure oxygen and CO2 in the blood. A healthcare provider will take a sample of blood from your artery. High levels of CO2 can indicate acidosis.


Electrolyte testing is a group of tests that measure levels of Na+ (sodium), K+ (potassium), Cl- (chloride), and bicarbonate. One or more of the electrolytes will be increased or decreased in people with acid-base disorders such as respiratory acidosis.

Lung function tests

Many people with this condition have reduced lung function.

Chest X-ray

X-rays can help doctors see injuries or other problems likely to cause acidosis.

Other tests

Based on these tests, your doctor may also perform other tests to help diagnose the underlying condition that’s causing the acidosis. (Another condition, known as metabolic acidosis, may cause similar symptoms, and the doctor may order tests to be sure the problem is solely respiratory. These tests measure the amount of acid in your body, which may be caused by kidney failure, diabetes, or other conditions, and include glucose, lactate, and ketones.) Other tests include drug testing, a complete blood count (CBC), and a urinalysis (urine test).

There are several different treatments for respiratory acidosis.

Acute form

Treating acute acidosis usually means addressing the underlying cause. For example, your airway may need to be cleared. This must be done as soon as possible. Artificial ventilation may also be needed.

Chronic form

If you have the chronic form of this disease, your treatment will focus on managing any underlying conditions. The goal is to improve airway function. Some strategies include:

  • antibiotics (to treat infection)
  • diuretics (to reduce excess fluid affecting the heart and lungs)
  • bronchodilators (to expand the airways)
  • corticosteroids (to reduce inflammation)
  • mechanical ventilation (in severe cases)

Respiratory acidosis has many causes, so it’s difficult to generalize about a long-term outlook. Your outlook largely depends on what’s causing your disease, and your doctor should be able to give you an idea of what to expect.

The acute form of respiratory acidosis can be fatal. Be sure to seek emergency medical help if you experience a sudden difficulty in breathing or if your airway is obstructed. This is especially important if you already have chronic respiratory acidosis or any of the underlying lung diseases.

The best way to prevent acidosis is to avoid causes of the disease.

Choosing to live a smoke-free lifestyle may help. Smokers are at higher risk for chronic respiratory acidosis. Smoking is bad for lung function. It increases the risk of respiratory diseases and can have an adverse impact on overall quality of life.

Maintaining a healthy weight can reduce your risk of this condition.

Use caution when taking sedatives. They can interfere with your ability to breathe. Sedatives depress the central nervous system. Always read and follow the label. Never take more than is recommended. Mixing sedatives with alcohol can be fatal.