# What are normal COHb levels?

Jul 27, 2021

## What are normal COHb levels?

Carboxyhemoglobin (COHb) is hemoglobin combined with carbon monoxide. A normal COHb level for non-smokers is <1.5%. Cigarette smokers can have COHb levels between 3-15%.

## What level of carboxyhemoglobin is fatal?

The mean lethal COHb level was 51 ± 12% with a majority range between 40% and 59% and the highest single frequency range at 45-59%. A report on CO exposure from exhaust fumes in the state of Maryland during 1966-1971 showed COHb levels in the 40-79% range for 98% of lethal cases (Nelson 2006a).

What is a critical carboxyhemoglobin level?

COHb levels of at least 3–4% in nonsmokers and at least 10% in smokers can be considered outside the expected physiological range (25). The COHb level in smokers is generally in the 3–5% range (25).

What is an abnormal carboxyhemoglobin?

Carboxyhemoglobin: An abnormal form of hemoglobin that has attached to carbon monoxide instead of oxygen or carbon dioxide. High amounts of this type of abnormal hemoglobin prevent the normal movement of oxygen by the blood. Sulfhemoglobin: A rare abnormal form of hemoglobin that can’t carry oxygen.

### How is COHb calculated?

A mathematical equation was developed to more accurately determine the constants A and B used in the equation COHB% = 100[(C – B)/(A – B)], where B = 0% COHB peak ratio at 540 nm and 579 nm; A = 100% COHB peak ratio at 540 nm and 579 nm; and C = the peak ratio at 540 nm and 579 nm for the blood being analyzed.

### What level of CO is toxic to humans?

As CO levels increase and remain above 70 ppm, symptoms become more noticeable and can include headache, fatigue and nausea. At sustained CO concentrations above 150 to 200 ppm, disorientation, unconsciousness, and death are possible.

What level of CO is fatal?

Is CO binding to hemoglobin reversible?

As the binding of carbon monoxide with hemoglobin is reversible, it is estimated that 20% of the carbon monoxide carried as carboxyhemoglobin may dissociate in remote tissues. Prolonged exposure to carbon monoxide and elevated carboxyhemoglobin, such as in smoking, results in erythremia.

## How is high carboxyhemoglobin treated?

Hyperbaric oxygen therapy (HBO) involves exposing patients to 100 percent oxygen under supra-atmospheric conditions. This results in a decrease in the half-life of carboxyhemoglobin (COHb), from approximately 90 minutes on 100 percent normobaric oxygen to approximately 30 minutes during HBO.

## Why would my carboxyhemoglobin be high?

Unequivocal increase in COHb indicates either a hemolytic process or more commonly carbon-monoxide poisoning. Increased COHb reduces tissue oxygenation but this is not the only mechanism of CO toxicity. Laboratory measurement of COHb is the only routinely available blood test for diagnosis of CO poisoning.

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Which is the most significant cause of increased COHb?

Breathing air polluted with high CO content – carbon-monoxide poisoning. This is clinically the most significant cause of increased COHb for two reasons. First it is a more common cause of increased COHb than endogenous production of CO, and secondly it can result in a much more severe increase in COHb.

### What are the potential associations between COHb and headache?

Potential associations between COHb levels and clinical findings include: COHb 10% – asymptomatic or headache COHb 20% – atypical dyspnea, throbbing headache, dizziness, nausea COHb 30% – severe headache, impaired thinking, disturbed vision

### What should the carboxyhaemoglobin level be for carbon monoxide poisoning?

Although there is no clear consensus on this issue, most studies examining carbon monoxide poisoning and its management use a carboxyhaemoglobin level of 10% or more, or the presence of clinical signs and symptoms after known exposure to carbon monoxide, to be indicative of acute carbon monoxide poisoning.

What should the carboxyhemoglobin level be in a smoker?

Heavy smokers (>2 packs/day): 8% – 9% (0.08 – 0.09); other sources suggest: 5% – 10% Suspected carbon monoxide poisoning – Carboxyhemoglobin (COHb) levels higher than 5% in a nonsmoker and 10% in a smoker confirm the diagnosis, but correlate poorly with severity of carbon monoxide poisoning.