Respiratory acidosis occurs when the lungs can’t remove enough of the carbon dioxide (CO2) that the body produces. Excess CO2 causes the pH of your blood and other bodily fluids to decrease, making them too acidic.

Usually, the body is able to balance the ions that control acidity. Doctors measure this balance on a pH scale from 0 to 14. A safe blood pH sits between 7.35 and 7.45, and acidosis occurs when the pH of the blood falls below 7.35.

Respiratory acidosis typically occurs due to 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, and CO2 passes the other way for removal as waste. However, sometimes the lungs can’t remove enough CO2. This may be due to a decrease in respiratory rate or air movement due to an underlying condition like:

We look at the different types of respiratory acidosis, the symptoms they cause, and the conditions that can contribute to their development.

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

Acute respiratory acidosis

This occurs after a sudden spike in CO2 levels once your body becomes less effective at getting rid of CO2. This type comes on quickly and qualifies as a medical emergency. Without treatment, symptoms will get progressively worse, and they may become life threatening.

Chronic respiratory acidosis

Certain chemoreceptors in your brain alert it to states of elevated CO2 and control your body’s ventilation, or how it disposes of waste gases in your blood. When these receptors become less sensitive, they might not pick up on elevated levels, leading to chronic respiratory acidosis.

This type develops over time and doesn’t cause symptoms. Instead, your body adapts to the increased acidity. For example, the kidneys produce more bicarbonate to help maintain your acid balance.

Chronic respiratory acidosis may not cause symptoms.

Acute and chronic respiratory acidosis

Some people have chronic respiratory acidosis and develop a co-occurring illness that affects ventilation. This can make your chronic presentation worse, even if you’d never noted symptoms before.

Doctors classify this as a combined type.

Initial signs of acute respiratory acidosis include:

Without treatment or in people with severe presentations of respiratory acidosis, other symptoms may occur. These include:

The chronic form of respiratory acidosis doesn’t typically cause any noticeable symptoms. When signs occur, they may include:

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, which is on the other end of the spectrum from an acid).

Respiratory acidosis usually occurs due to a lung disease or condition that affects typical breathing or impairs the lungs’ ability to remove CO2.

Causes of acute respiratory acidosis

Some common causes of the acute form are:

  • COPD
  • emphysema
  • asthma
  • pneumonia
  • conditions that affect your rate of breathing
  • muscle weakness that affects breathing or taking a deep breath
  • obstructed airways (due to choking or other causes)
  • overuse of drugs like opioids that affect the central nervous system

Causes of chronic respiratory acidosis

The following commonly cause chronic respiratory acidosis:

The goals of diagnostic tests for respiratory acidosis are:

  • to test for any pH imbalance
  • to determine the severity of the imbalance
  • to identify 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 professional will take a sample of blood from your artery. High levels of CO2 can indicate acidosis.


Electrolyte testing refers to a group of tests that measure levels of certain minerals and salts in your body, including:

One or more of the electrolytes will be higher or lower than usual in people with acid-base disorders like respiratory acidosis.

Lung function tests

Many people with this condition have reduced lung function. Several tests can help a doctor measure the effectiveness of your lungs when they’re fulfilling the following functions:

  • moving air into and away from the lungs
  • transferring oxygen into your bloodstream
  • holding enough air

These tests include:

  • Spirometry. A healthcare professional will have you breathe in and out of a specialized device called a spirometer. This measures how much air you move in and out of your lungs and how much air you move when you do it.
  • Lung volume test. Seated in an airtight booth, you’ll take deep breaths in and out. The amount of air your lungs breathe in will affect air pressure, which allows the healthcare professional to measure how much air your lungs can hold.
  • Gas diffusion test. You’ll breathe a safe amount of carbon monoxide through a mouthpiece that’s attached to a machine. From this, your doctor will be able to measure how effective your lungs are at passing gases into the bloodstream.
  • Exercise test. This involves running on a treadmill or using an exercise bike while monitors keep track of your blood pressure, blood oxygen, and heart rate. The exercise shows how your lungs function when you’re physically exerting yourself.

Chest X-ray

X-rays can help doctors see injuries, muscular issues, or skeletal problems that can cause acidosis.

Other tests

Based on the outcomes of these tests, your doctor may also perform other examinations to help diagnose the condition that’s causing the acidosis.

Another condition, known as metabolic acidosis, may cause similar symptoms. The doctor may order tests to be sure the problem is only down to respiratory problems. 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:

There are several treatments for respiratory acidosis.

Treatment for acute respiratory acidosis

Treating acute respiratory acidosis usually involves addressing the underlying cause. You should receive treatment ASAP, as acute respiratory is a medical emergency.

For example, your doctor may need to provide interventions that clear your airway, such as bronchodilator medications.

You might also require artificial ventilation through a machine like BiPAP, which assists your breathing and gas transfer without the need for invasive tubing.

Treatment for chronic respiratory acidosis

If you have chronic respiratory acidosis, your healthcare professional will focus on managing any underlying conditions to avoid an acute presentation of the condition.

The goal is to improve airway function. Some medications for treating respiratory acidosis include:

Respiratory acidosis has many underlying 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 after examining your physical symptoms and carrying out tests.

When to seek emergency care for acute respiratory acidosis

Acute respiratory acidosis can be fatal. Be sure to seek emergency treatment if you:

  • experience a sudden difficulty in breathing
  • have an obstruction in your airway

This is especially important if you already have chronic respiratory acidosis or any of the underlying lung diseases.

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

Don’t smoke

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.

Manage your weight

Some people with obesity can develop obesity hypoventilation syndrome (OHS) (also known as Pickwickian syndrome), which can be an underlying cause of respiratory acidosis.

Exercise caution when taking sedatives

They can interfere with your ability to breathe. Your nervous system plays a key role in breathing mechanisms, and sedatives depress the central nervous system. When you’re taking sedatives, the following measures can help you protect your respiratory health:

  • Always read and follow the label.
  • Never take more than the prescribed dose.
  • Avoiding mixing sedatives with alcohol, as this can be fatal.

It’s not possible to prevent some causes of respiratory acidosis, such as MS. However, the measures above may help you reduce your risk for an acute emergency.