CO2 Buildup in Lungs: Symptoms, causes, and treatment

Carbon dioxide (CO2) buildup in the lungs can make you very sick and may require hospitalization for life-saving treatment. I have personally treated several patients hospitalized with significant CO2 buildup in the lungs. In this article, I will review the symptoms, causes, and treatment of CO2 buildup in the lungs based on my personal experience, expertise, and the review of current medical literature.

What causes CO2 buildup in your lungs?

A diagram showing how oxygen and CO2 move inside air sacs in the lungs alongside blood.
A diagram showing how oxygen and CO2 move inside the lungs

Carbon dioxide accumulation occurs when your lungs don’t ventilate enough. Your lungs have two important functions: they take oxygen in, and they throw CO2 out. CO2 is the byproduct of all basic chemical reactions inside your body. It is like the exhaust gas produced by your car’s engine. The gas has to go out. Just like a car, your body burns fuel for energy. You need oxygen to burn it. All energy sources in your body turn into carbon dioxide after combining with oxygen.

Your lungs handle oxygen and carbon dioxide somewhat differently. Oxygen doesn’t dissolve in the blood, so it needs red blood cells to carry it around the body. Unlike oxygen, CO2 flows freely in your body and your blood. It also passes freely from the blood to the air and vice versa. Carbon dioxide in the blood simply goes out from your blood into the air inside your lungs as long as the carbon dioxide level in your blood is higher than the carbon dioxide level inside your lungs.

Here are several diseases and conditions that cause CO2 buildup inside your lungs:

  1. COPD: High CO2 levels are very common in COPD patients. I will discuss CO2 accumulation in COPD patients down below.
  2. Obesity Hypoventilation syndrome: This is another common condition that leads to carbon dioxide buildup in the lungs. There is a related article called “Shortness of breath from being overweight” that could help you understand how obesity hypoventilation leads to shortness of breath. When you gain too much weight, the excess fat makes it harder to take a deep breath. Eventually, part of your lungs collapse and your ventilation suffers, leading to CO2 buildup in the lungs.
  3. Opioid overdose: All opioids slow down your breathing. They act on the respiratory centers in your brain and lower the drive to breathe. When your breathing gets too slow to get rid of the carbon dioxide inside your lungs, you have CO2 buildup.
  4. Muscle weakness: People with diseases that affect muscle strength are at risk of getting CO2 buildup in their lungs. As diseases like myasthenia or muscular dystrophy progress, it starts to affect the chest and belly muscles that move your lungs. When they can’t move enough air, CO2 starts to build up inside the lungs.

Symptoms of CO2 buildup in the lungs

CO2 accumulation in the lungs leads to high CO2 levels in the blood. High levels of CO2 affects multiple organs and may lead to life-threatening symptoms. The severity of these symptoms not only depends on how high the carbon dioxide levels in the blood are, but also on how fast they developed. Someone with very high carbon dioxide levels in the blood may only have mild symptoms if the rise of CO2 levels in the blood was very gradual.

Here are the common symptoms of CO2 buildup in the lungs, ordered from mild to severe:

  1. Increased sleepiness and lethargy
  2. Persistent headaches
  3. Increased heart rate
  4. Shortness of breath
  5. Flushed skin
  6. Problems with memory and concentration
  7. Confusion
  8. Muscle twitching
  9. Unresponsiveness
  10. Very slow breathing
  11. Seizures
  12. Entering a coma

When considering symptoms of CO2 buildup in the lungs, it is important to note if there are also signs or symptoms of low oxygen. Although CO2 accumulation can happen without low oxygen, they frequently occur together. Low oxygen makes you short of breath. People usually seek help right away when they feel short of breath.

When CO2 buildup in the lungs happens without low oxygen, people may not pay attention to the symptoms until they are too severe. I have admitted patients to the hospital with unresponsiveness who were nearing a coma. When those patients were bought down to the hospital ER by their family, we did not know why they were in an almost coma-like state. We knew they had CO2 buildup in their lungs after we ordered a blood test called an arterial blood gas analysis.

How we diagnose CO2 buildup in the lungs

An arterial blood gas analysis is what we do to check for CO2 levels in the blood. Arteries are the blood vessels that carry blood out of the heart. They are the supply lines. Arteries supply blood to the different parts of your body, and veins drain the used-up blood. Used-up blood in the veins have higher CO2 levels than the arteries because they drain the excess CO2 from all organs. Veins ultimately dump that co2 in the lungs before returning the blood to the heart. The arterial blood gas analysis reflects true CO2 levels in the lungs because arteries carry blood that has already been through the lungs.

Arterial blood gas is obtained by taking a blood sample from a pulsating artery in your wrist. There are no other reliable ways to diagnose CO2 buildup in the lungs except an arterial blood gas analysis. We can directly measure the CO2 levels in the blood obtained from your artery, and it reflects the CO2 levels in your lungs.

Arterial blood gas levels are measured in partial pressure of the particular gas. For carbon dioxide, it is called PaCO2 and the unit is millimeters of Mercury (mmHg). Normal PaCO2 in the arterial blood is 35 to 45 mmHg. The difference between the CO2 levels in the blood and the lungs is only about 5 mmHg. It means that the normal CO2 levels in the lungs should be 30 to 35 mmHg. For reference, the partial pressure of CO2 at sea level is 0.3 mmHg. The inside of your lungs have about 100 times more CO2 than the air going into your lungs. Your lungs have to keep breathing out this excess CO2 to avoid CO2 buildup in the lungs.

COPD and CO2 buildup in the lungs

COPD is a common cause of CO2 buildup in the lungs. COPD is almost exclusively a disease of smokers. The lungs of people with COPD lose elasticity and end up trapping air inside. The narrowing of the small air tubes significantly obstructs and slows down the movement of air in and out of the lungs. People with COPD develop different levels of CO2 buildup in their lungs. However, their bigger problem is low oxygen. Most COPD patients with CO2 buildup in the lungs have their bodies adjusted to the higher levels of CO2 in their blood. Unless the PaCO2 is too high and the body hasn’t been able to adjust to it, separate treatment is not needed to lower the CO2 buildup. Treatment should focus on getting the oxygen levels back to normal instead.

Treatment of CO2 accumulation

Treatment of CO2 accumulation depends on the severity and urgency of the situation. Mild symptoms may not require any urgent intervention, but severe symptoms may become life-threatening if not treated urgently. It is not possible to tell exactly when you need urgent intervention because it depends on a lot of different factors. However, there are certain things that may indicate the need for an urgent removal of the excess CO2 built-up in your lungs.

Here are those high-risk features:

  1. Mental status changes: If high CO2 is making you confused or disoriented, you may need urgent intervention
  2. If your blood is too acidic: Rapid accumulation of carbon dioxide may change the acidity of your blood. When they check your arterial blood gases, they also check your pH. Low pH suggests increased acidity of your blood, and that requires quick intervention.
  3. Drug overdose: CO2 buildup in the lungs caused by opioid or other drug overdose
  4. Muscle weakness: CO2 buildup as a result of severe muscle weakness

There are two basic treatment options for removing the excess carbon dioxide from your lungs:

  1. A non-invasive treatment called Bipap
  2. An invasive treatment with intubation and mechanical ventilation

Bipap should be the first treatment choice when it can be done. Bipap treatment is done by putting a tight fitting mask around your mouth and nose. Air is forced in and out under pressure to remove the excess carbon dioxide. You have to be awake and conscious to safely perform Bipap.

If you are too sick, unconscious, or comatose, Bipap is not an option. They need to put an actual tube inside your air-pipe and hook you up to a ventilator. You need to be sedated and restrained for this kind of procedure, and it is only possible in a hospital ICU. The ventilator will move air in and out of your lungs to get rid of the excess CO2.

In conclusion, CO2 build up in the lungs can be life-threatening in certain instances. It is important to know the symptoms and understand the dangers. You may need hospitalization for urgent treatments in certain situations.