A 29 year-old man just came to the clinic complaining of strange bilateral headache, slight burning to the eyes, nausea and some dizziness.
He volunteers that his car leaks carbon dioxide, through the air-conditioning he thinks, an old van that has been doing this for at least a month. He complains of his lungs hurting (by which he referrs to lower bilateral pleuritic chest pain) associated with an unproductive cough. His eyes are watering and he feels he has swollen glands and sometimes a whistling sound to his cough. He has a history of mild asthma and smokes 20 cigarettes a day.
There is no family history of note.
The man is in good spirits, jovial and pleasant. His conjunctiva look mildly inflamed but tongue normal and throat ever so slightly injected. His lung fields move an adequate amount of air equally without added sounds.
I send him for venous carboxyhaemoglobin level as well as a standard battery of tests. A normal carboxyhemoglobin level is <5% in non-smokers and <10% in smokers.
If he has carbon monoxide posioning we would expect:
- carboxyhaemoglobin > 10%
- Metabolic acidosis due to build-up of lactate
What this man can smell are by-products of petrol combustion—such as sulfur dioxide, nitrogen oxides, benzene—other than carbon monoxide and carbon dioxide, both of which are odourless as well as colourless.
His skin is a normal colour. Compare the cherry-red skin of frank carbon monoxide poisoning.
Exhaust Fumes contain:
- Carbon monoxide and carbon dioxide
- Hydrocarbons (Benzene)
- Sulphur dioxide
- Nitrous oxides
- Soot
Note: Oxygen saturation recorded by pulse oximetry will be normal (the probe does not differentiate between carboxy- and oxy-haemoglobin).
Management
- Oxygen supplementation (occasionally hyperbaric oxygen)
References
Lab Test: Carboxyhemoglobin Level – Evidence-Based Medicine Consult
Carbon Dioxide, OSH Answers Fact Sheets – Canadian Centre for Occupational Health and Safety
Dangers of Exhaust Fumes, Mark Perry – Health Guidance for Better Health
Chapter 5. Environmental and Nutritional Pathology, The Big Picture Pathology, Lange
Carbon Monoxide Poisoning, Katie Auriemma – Med Bullets
