Nursing care
Carbon Monoxide Poisoning nursing care: what to assess and what to do first
Written and reviewed by Dana Whitfield, RN, MSN · 5 min read · Updated September 2026
Short answer
Carbon monoxide poisoning occurs when CO binds haemoglobin far more readily than oxygen does, displacing it and starving tissues of oxygen despite a normal-looking pulse oximetry reading. The oximeter cannot distinguish oxyhaemoglobin from carboxyhaemoglobin, so it reports a falsely reassuring saturation. High-flow oxygen and a carboxyhaemoglobin level, not the SpO2, confirm and treat the exposure.
The clinical picture
Early carbon monoxide poisoning presents with symptoms easy to dismiss: headache, dizziness, nausea, and fatigue that resemble a viral illness or a hangover. This vagueness is part of why exposures are missed, particularly when multiple household members present with similar symptoms that clear when they leave the house — a pattern worth asking about directly.
As exposure worsens, confusion, chest pain, tachycardia, and syncope appear, and severe poisoning can progress to seizures, coma, and cardiac arrhythmia. The cherry-red skin colour described in textbooks is a late and unreliable sign, rarely seen clinically; most patients simply look unwell rather than obviously discoloured. Sources include faulty furnaces, generators run in enclosed spaces, car exhaust in a closed garage, and structure fires.
Assessment: what to look for and in what order
Start with a targeted exposure history: source of heat or fuel in the home, generator use, time spent in an enclosed space, and whether symptoms improve away from the suspected source. This history often does more diagnostic work than the physical exam in early poisoning.
Assess neurological status carefully, since CO's effect on the brain — confusion, impaired judgement, ataxia — can appear before more dramatic findings and is easy to attribute to something else in an older adult or a patient with existing cognitive issues. Check for tachycardia and tachypnoea as the body compensates for reduced oxygen delivery. Critically, do not rely on pulse oximetry or skin colour to gauge severity; order a carboxyhaemoglobin level via co-oximetry as soon as exposure is suspected, because standard oximetry reads carboxyhaemoglobin as if it were oxyhaemoglobin and will show a falsely normal or near-normal number.
Immediate interventions
Remove the patient from the source of exposure immediately if not already done, and administer 100% oxygen via non-rebreather mask regardless of what the pulse oximeter shows. Oxygen at high concentration accelerates the dissociation of CO from haemoglobin and shortens its half-life considerably compared with room air.
Continuous cardiac monitoring is warranted given the arrhythmia risk, along with neurological checks at frequent intervals since deterioration can be rapid. For severe poisoning — loss of consciousness, significant metabolic acidosis, pregnancy with elevated levels, or very high carboxyhaemoglobin — hyperbaric oxygen therapy may be indicated and should be arranged promptly through the appropriate facility. Treat co-occurring cyanide toxicity as a possibility in fire-related exposures, since the two often coexist.
Ongoing nursing management
Trend carboxyhaemoglobin levels rather than a single value, since the level at presentation may not reflect peak exposure if time has passed or oxygen has already been started en route. Continue to monitor mental status closely, as neurological symptoms can persist or even recur days to weeks after apparent recovery, a phenomenon known as delayed neurological sequelae.
Watch for signs of myocardial injury, since CO poisoning can cause ischaemia even in patients without prior cardiac disease, and obtain an ECG and cardiac markers when exposure is moderate to severe. Reassess for headache, memory difficulty, or personality change before discharge, and document baseline cognitive status so any delayed decline is easier to identify at follow-up.
Patient and family education
Teach the specific mechanism in plain terms: CO binds haemoglobin far more strongly than oxygen does, which is why a normal pulse oximeter reading during or after exposure does not mean oxygen delivery to tissues was adequate. Patients often assume a normal number at the hospital means they are fine, and that assumption needs correcting directly.
Teach practical prevention — install and test CO detectors on every level of the home, never run a generator, grill, or vehicle in an enclosed or attached space, and have fuel-burning appliances serviced annually. Advise that anyone in the household with unexplained headache, dizziness, or nausea that improves outside the home should be evaluated, since CO poisoning frequently affects multiple people at once. Warn specifically about delayed neurological symptoms — new memory problems, mood change, or difficulty concentrating in the weeks after exposure warrant follow-up rather than being dismissed.
How this appears on the NCLEX
Expect questions that present a patient with headache, nausea, and a normal SpO2 after a plausible CO exposure — a faulty furnace, a generator, a closed garage — and ask for the priority action. The correct answer is typically administering high-flow oxygen and obtaining a carboxyhaemoglobin level, not reassurance based on the oximeter reading.
Questions may also test recognition that the cherry-red skin finding is unreliable and should not be relied upon to rule poisoning in or out, and that hyperbaric oxygen is reserved for more severe presentations rather than being the automatic first step. Multiple-victim household scenarios are a common cue the exam uses to signal CO exposure over a single unrelated illness.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our respiratory practice questions are the closest set to what this page covers.
Common questions
Why does a pulse oximeter read normal in carbon monoxide poisoning?
Standard pulse oximetry works by distinguishing light absorption between oxyhaemoglobin and deoxyhaemoglobin, but it cannot tell carboxyhaemoglobin apart from oxyhaemoglobin. It reads carboxyhaemoglobin as if it were normally oxygenated blood, producing a falsely reassuring saturation even when significant CO poisoning is present. A carboxyhaemoglobin level via co-oximetry is needed for an accurate picture.
Is the cherry-red skin sign reliable for diagnosing CO poisoning?
No. Cherry-red skin is a classic textbook finding but is rarely seen in practice and appears late, if at all. Most patients with carbon monoxide poisoning simply look unwell, pale, or cyanotic, so absence of cherry-red discolouration should never be used to rule out exposure.
What is the first treatment for suspected carbon monoxide poisoning?
Remove the patient from the source and start 100% oxygen via non-rebreather mask immediately, without waiting for a carboxyhaemoglobin result. High-concentration oxygen speeds the removal of CO from haemoglobin and should not be delayed for confirmatory testing.
When is hyperbaric oxygen used for CO poisoning?
Hyperbaric oxygen is generally reserved for severe cases — loss of consciousness, significant metabolic acidosis, pregnancy with elevated carboxyhaemoglobin, or very high carboxyhaemoglobin levels. It is not the routine first-line treatment; high-flow normobaric oxygen is started first in nearly all cases while hyperbaric therapy is arranged if criteria are met.
Can carbon monoxide poisoning cause problems weeks after exposure?
Yes, delayed neurological sequelae can appear days to weeks after apparent recovery, including memory difficulty, personality change, and cognitive impairment. Patients and families should be told to seek evaluation for new neurological or mood symptoms in the weeks following exposure rather than assuming recovery is complete at discharge.