Carbon monoxide poisoning is treated with high-concentration oxygen, which flushes the gas from your bloodstream far faster than breathing normal air. The cornerstone of treatment at every stage, from the moment you suspect exposure to hospital care, is getting more oxygen into the body as quickly as possible. How aggressively that oxygen is delivered depends on how severe the poisoning is.
Why Carbon Monoxide Is So Dangerous
Carbon monoxide binds to hemoglobin, the molecule in red blood cells that carries oxygen, roughly 200 times more strongly than oxygen does. Once CO latches on, it prevents that hemoglobin from picking up and delivering oxygen to your brain, heart, and other organs. Even a relatively small amount of the gas can occupy a significant share of your blood’s oxygen-carrying capacity.
This is also why the poisoning is so easy to miss. Standard fingertip pulse oximeters cannot tell the difference between hemoglobin loaded with oxygen and hemoglobin loaded with carbon monoxide. Your oxygen saturation reading can look perfectly normal while your tissues are starving. The only reliable way to confirm poisoning is a blood test that directly measures the percentage of hemoglobin bound to CO (called carboxyhemoglobin, or COHb). Some newer pulse oximeters can distinguish the two, but a blood gas analysis remains the standard.
What to Do Immediately
If you suspect carbon monoxide exposure, the first step is always the same: get into fresh air right away and call 911. Don’t go back inside to grab belongings or investigate the source. Symptoms to watch for include headache, dizziness, nausea, shortness of breath, weakness, and confusion. Because everyone in the same space is breathing the same air, check on others in the household, especially children, elderly people, and pets, who may be affected more quickly.
Once you’re outside, stay calm and try to keep still. Physical exertion increases your body’s demand for oxygen, which makes the situation worse. If someone has lost consciousness or is unresponsive, move them outdoors if you can do so safely and begin CPR if they aren’t breathing. Emergency responders carry high-flow oxygen and can start treatment on the scene.
Standard Oxygen Therapy
At the hospital, the primary treatment is breathing pure (100%) oxygen through a tight-fitting mask. This dramatically speeds up the rate at which your body clears carbon monoxide. Breathing normal room air, the half-life of CO in your blood is about 320 minutes, meaning it takes over five hours just to cut the level in half. With 100% oxygen delivered through a mask, that half-life drops to roughly 74 minutes. Complete elimination takes about five half-lives, so you can expect to be on high-flow oxygen for around six hours in a straightforward case.
During this time, the medical team monitors your COHb levels through blood draws and watches for signs of heart involvement, since the heart is one of the first organs affected by oxygen deprivation. An ECG and blood tests for cardiac markers are standard parts of the workup.
When Hyperbaric Oxygen Is Used
For more severe cases, treatment may involve a hyperbaric oxygen chamber: a sealed room or tube pressurized to two to three times normal atmospheric pressure while you breathe pure oxygen. Under these conditions, the half-life of CO in the blood falls to about 20 minutes, clearing the gas far faster than a mask alone.
The CDC recommends considering hyperbaric oxygen therapy when any of the following are present:
- COHb levels above 25-30%
- Loss of consciousness, even briefly
- Evidence of heart involvement
- Severe acid buildup in the blood
- Neurological impairment, such as confusion, difficulty thinking, or abnormal neuropsychiatric testing
Hyperbaric treatment can also be used at lower COHb levels if the clinical picture warrants it, for example, if the exposure lasted many hours or symptoms are disproportionately severe. A session typically lasts one to two hours. Some patients need more than one session depending on their response.
Not every hospital has a hyperbaric chamber, so patients sometimes need to be transferred to a facility that does. Emergency teams make this call based on the severity of symptoms and how far away the nearest chamber is.
Treatment During Pregnancy
Pregnant women are treated more aggressively regardless of symptom severity. Hyperbaric oxygen is the preferred treatment for all pregnant patients, even those with mild poisoning, because fetal hemoglobin binds carbon monoxide even more tightly than adult hemoglobin. The fetus takes longer to clear CO from its blood than the mother does, meaning the baby remains at risk even after the mother feels better.
Research on pregnant patients treated with hyperbaric oxygen at 2.4 times normal atmospheric pressure for 120 minutes has shown no harmful effects on either mother or fetus. In cases where fetal distress was detected, continuing hyperbaric treatment proved beneficial. Some patients required more than one session when signs of fetal stress persisted.
How Severity Is Assessed
Doctors use your COHb percentage alongside your symptoms to gauge severity, though the two don’t always line up neatly. As a rough guide:
- COHb around 10%: No symptoms, or just a headache
- COHb around 20%: Throbbing headache, dizziness, nausea, shortness of breath
- COHb around 30%: Severe headache, impaired thinking, vision problems
- COHb around 40%: Fainting, significant confusion
- COHb around 50%: Seizures, extreme drowsiness, coma
- COHb 60% or higher: Heart and lung failure, high risk of death
These ranges are approximate. Some people experience serious symptoms at levels that look moderate on paper, particularly with prolonged low-level exposure. That’s partly why COHb numbers alone don’t determine treatment decisions.
Delayed Neurological Effects
One of the more concerning aspects of carbon monoxide poisoning is what can happen days or weeks after exposure. Some patients recover fully, feel fine for a stretch of 2 to 40 days, and then develop new neurological or psychiatric symptoms. This is known as delayed neurological sequelae, and estimates suggest it affects anywhere from 1% to 47% of poisoning survivors, a wide range that reflects how difficult it is to predict and track.
Symptoms can include memory problems, difficulty concentrating, personality changes, depression, anxiety, and movement disorders similar to Parkinson’s disease. Being older than 36 and having been exposed for longer than 24 hours are both risk factors for developing these delayed effects. Research has also linked CO poisoning to longer-term health consequences including dementia, diabetes, cardiovascular events, and higher overall mortality in the years that follow.
This delayed window is the reason follow-up care matters even when initial recovery seems complete. If new cognitive or mood symptoms appear in the weeks after poisoning, they should be evaluated promptly, as they may be directly related to the original exposure and not a separate issue.