What Is Carbon Dioxide Narcosis and How Is It Treated?

Carbon dioxide narcosis is a dulling of the mind, anywhere from sleepiness to coma, caused by carbon dioxide piling up in the blood because breathing can no longer clear it. It usually builds in people whose lungs or breathing muscles are already failing, rather than coming from something they breathed in. In the most common hospital version, the drowsiness is a sign the person needs help breathing out, not just more oxygen, which is why treatment focuses on breathing support.1PubMed Central. A clinical guide to non-invasive respiratory support in acute respiratory failure: ventilation settings, technical optimization and clinical indications

What Happens in the Body During CO2 Narcosis

Every cell in the body makes carbon dioxide as waste, and the blood carries it to the lungs to be breathed out. When breathing is too weak or shallow, CO2 stays in the blood, a state doctors call hypercapnia. The extra CO2 makes the blood more acidic, which can depress breathing and circulation.2PubMed Central. Carbon dioxide poisoning: a literature review of an often forgotten cause of intoxication in the emergency department

The brain effects follow how high CO2 climbs. When CO2 in arterial blood rises quickly above about 70 to 75 mmHg, roughly double normal, awareness drops. Above about 100 to 120 mmHg, a person stops responding.3Global Underwater Explorers. Carbon Dioxide, Narcosis, and Diving High CO2 also widens the blood vessels in the brain, which can cause brain swelling and raised pressure inside the skull.4PubMed Central. The role of carbon dioxide in acute brain injury

The name comes from “narcosis,” a drug-like stupor. At high levels, CO2 acts on the brain much like a sedative, so the person may look deeply asleep rather than distressed.

In many patients it builds gradually. The body can adapt to slowly rising CO2 for a while, with the kidneys holding onto bicarbonate to buffer the acid. A sudden extra push, such as an infection, can tip that balance, and the fall into drowsiness can then be quick.

Relatives sometimes let a drowsy person “rest” when the sleepiness is actually a warning sign. The key check is whether they can be woken fully, stay awake, and make sense. Someone who drifts off mid-sentence or can’t be roused needs urgent help. Snoring-like or unusually slow, shallow breathing during this sleep is a further reason to call for help rather than wait.

Who Gets CO2 Narcosis and Why

COPD, a long-term lung disease that narrows airways, is the most common cause of hospital cases of CO2 build-up.5PubMed Central. Acute Hypercapnic Respiratory Failure in COPD In severe COPD, people can’t breathe harder to blow off extra CO2, so a flare-up that would be a nuisance for someone else can leave them retaining it.6PubMed Central. Oxygen-induced hypercapnia in COPD: myths and facts

Many people at risk go about daily life with CO2 somewhat above normal and no obvious distress, so the danger is easy to overlook. Their reserve is small, which is why a cold can become an emergency for them.

Weak breathing muscles cause a slower, nightly build-up. People with neuromuscular diseases are especially prone to breathing too little during sleep.7MEDICINA (Buenos Aires). When Should and When Should Not Use Oxygen in Neuromuscular Diseases? Night-time under-breathing makes the body retain bicarbonate, which further dampens breathing and raises daytime CO2.8MEDICINA (Buenos Aires). When Should and When Should Not Use Oxygen in Neuromuscular Diseases? Some people live for years with very high CO2 before developing heart strain and narcosis symptoms.9PubMed Central. Noninvasive Respiratory Management of Patients With Neuromuscular Disease Adding a sedative to this cycle can push the person into a coma.10MEDICINA (Buenos Aires). When Should and When Should Not Use Oxygen in Neuromuscular Diseases?

Several triggers tip a stable patient over. A chest infection or flu raises the body’s CO2 production and the work of breathing at the same time, which a weakened system can’t match. Sedatives, sleeping pills and opioids blunt the brain’s urge to breathe, so breathing slows further. Uncontrolled oxygen can worsen CO2 retention, as the next section explains. Tired breathing muscles can simply give out after days of extra effort, leaving breathing shallow.

Slow breathing after anesthesia or from opioids is one reason people wake slowly after surgery.11PubMed Central. Delayed emergence after general anesthesia: working through the differential diagnosis Anyone with weak breathing should tell doctors before taking sleeping pills or strong painkillers.

Why Too Much Oxygen Can Make It Worse

Normally, blood flow is steered away from poorly aired parts of the lung, toward the parts that are working. High oxygen switches off that steering, so blood flows to areas that can’t clear CO2.12PubMed Central. Oxygen-induced hypercapnia in COPD: myths and facts More breaths are wasted, and the share of wasted breathing rose from 77% to 82% in severe COPD on high oxygen.13PubMed Central. Oxygen-induced hypercapnia in COPD: myths and facts Oxygen also makes blood release CO2 it was carrying, accounting for about a quarter of the rise.14PubMed Central. Oxygen-induced hypercapnia in COPD: myths and facts Reduced breathing drive and collapse of tiny air sacs add to the effect.15Monaldi Archives for Chest Disease. Oxygen-induced hypercapnia: physiological mechanisms and clinical implications

The old explanation was that people with COPD rely on low oxygen to drive their breathing, so extra oxygen removes the urge to breathe. That turns out to be a minor part of the story. Most of the rise comes from wasted breaths and CO2 released from the blood. Oxygen is still life-saving and shouldn’t be withheld from someone who needs it; the aim is the right amount, not none. Stopping it abruptly is dangerous, because oxygen levels can drop fast.

That is why hospitals use targets. In COPD flare-ups, UK and European guidelines aim for oxygen saturation of 88% to 92%.16PubMed. Oxygen therapy and inpatient mortality in COPD exacerbation Deaths were lowest in that range and rose even at 93% to 96%.17PubMed. Oxygen therapy and inpatient mortality in COPD exacerbation So a reading around 90% on a COPD patient’s monitor is often intended, not a failure.

At home or in transport, families can use the oxygen flow rate that was prescribed, not higher. It helps to ask whether the person has an oxygen alert card, and to tell paramedics that the person retains CO2.

Signs That CO2 Is Building Up

Symptoms progress as CO2 rises:

Families often notice unusual daytime sleepiness first, such as dozing during a conversation or a meal. In people with weak breathing muscles, headaches on waking are a typical clue, because CO2 climbs overnight. Muddled speech, or saying things that don’t make sense, suggests the brain is being affected. Flushed skin and twitching or shaky hands can also appear, though not everyone has them.

A blood gas test, usually from a wrist artery, measures CO2 and acidity directly. How acidic the blood is predicts how drowsy patients are better than the CO2 number itself.21PubMed. Noninvasive positive pressure ventilation in patients with acute exacerbations of COPD and varying levels of consciousness

A normal oxygen reading doesn’t rule this out. Finger monitors measure oxygen only, and CO2 can be high while oxygen looks fine, especially when the person is on oxygen. Only a blood gas test or a CO2 monitor shows CO2.

How CO2 Narcosis Is Treated

BiPAP is a tight face mask that pushes air in and helps the person breathe out. It is strongly recommended for CO2 build-up with acidic blood, because it prevents the need for a breathing tube and reduces deaths.22PubMed Central. A clinical guide to non-invasive respiratory support in acute respiratory failure: ventilation settings, technical optimization and clinical indications

Unconscious patients, or those with very weak breathing, usually need intubation, a tube in the windpipe connected to a ventilator.23MD Searchlight. Carbon Dioxide Narcosis Deep drowsiness raises the risk of breathing stomach contents into the lungs, which is part of why the tube is used.24MD Searchlight. Carbon Dioxide Narcosis These patients are watched in intensive care with repeated blood gas tests.25MD Searchlight. Carbon Dioxide Narcosis If consciousness keeps falling despite the mask, doctors switch to a breathing tube.26PubMed Central. Post-Hypercapnic Alkalosis: A Brief Review

On a mask breathing machine, the mask fits tightly over the nose and mouth and the air pushes in firmly, which can feel strange or suffocating at first. Talking, drinking and eating are hard while it’s on, so staff arrange breaks or other ways to take fluids and medicines once the person is stable enough. Doctors usually recheck blood gases within an hour or two to see whether CO2 and acidity are improving. Families can help by staying calm, speaking reassuringly, and encouraging the person to breathe with the machine rather than fight it.

The underlying problem is treated at the same time. Medicines usually include inhaled airway-opening drugs, steroids, and antibiotics for infection.27PubMed Central. Acute Hypercapnic Respiratory Failure in COPD Nebulizers may be driven by air instead of oxygen to avoid overshooting oxygen targets.28PubMed Central. Supporting patients with hypercapnia Steroids by mouth work as well as by drip.29PubMed Central. Supporting patients with hypercapnia

Sedatives deepen the drowsiness, so staff review all medications and often stop them. Families should report any sleeping pills or painkillers the person takes at home.

Recovery and Preventing Another Episode

As CO2 falls with breathing support, alertness usually returns. Improvements in blood acidity after one to two hours of mask ventilation track improving alertness.30PubMed. Noninvasive positive pressure ventilation in patients with acute exacerbations of COPD and varying levels of consciousness The underlying lung or muscle disease remains, so recovery means returning to the earlier baseline rather than being cured. Some people feel weak or tired for a while afterwards, particularly after time in intensive care.

Night-time under-breathing drives daytime build-up in weak-muscle conditions,31MEDICINA (Buenos Aires). When Should and When Should Not Use Oxygen in Neuromuscular Diseases? so home night-time mask ventilation is often used to break the cycle. A mask machine like the one used in hospital is worn during sleep, when breathing is weakest. Giving the muscles a rest overnight can lower daytime CO2 and may ease morning headaches and sleepiness. A specialist team sets it up and monitors it, adjusting the mask fit and settings over time. Vaccines reduce flare-ups, rescue plans should start early in an infection, and unusual drowsiness is a reason to seek care at the first sign.

Before discharge, it helps to ask whether home ventilation is needed, what the right oxygen flow and target range are, which medicines to avoid, and which warning signs mean calling for help.

CO2 Narcosis From Breathing CO2-Rich Air

It can also happen from CO2 in the environment. Low CO2 in air does little harm, but above 5% it raises blood CO2 and acidity.32PubMed Central. Carbon dioxide poisoning: a literature review of an often forgotten cause of intoxication in the emergency department Above 10% it can cause seizures, coma and death.33PubMed Central. Carbon dioxide poisoning: a literature review of an often forgotten cause of intoxication in the emergency department Above 30% people lose consciousness within seconds, which is why victims often can’t escape.34PubMed Central. Carbon dioxide poisoning: a literature review of an often forgotten cause of intoxication in the emergency department

Enclosed spaces become dangerous because CO2 is heavier than air, so it can pool in low places like cellars, wells, silos, and fermentation or brewing areas. Dry ice turning into gas in a small closed space such as a car or storeroom can raise levels quickly. With no smell or visible warning, people may not notice anything is wrong before they feel dizzy.

With fast rescue, outcomes can be good. In one mass exposure, people had breathlessness, cough, dizziness, chest pain and headache, and some had heart rhythm changes or fluid in the lungs. No one died when evacuated quickly and given supportive care.35PubMed. Exposure to extremely high concentrations of carbon dioxide: a clinical description of a mass casualty incident

Nobody should enter after a collapsed person without protection. Ventilate the space if it can be done safely, and call emergency services.