Carbon monoxide poisoning
A patient with unexplained headache, fatigue (disturbed consciousness), nausea and vomiting may have carbon monoxide poisoning. Because the symptoms of are so unspecific, exposure to carbon monoxide is an under-diagnosed problem. Hyperbaric oxygen therapy may be considered in severe carbon monoxide poisoning (COHb > 40%) or if the patient has symptoms . Regular pulse oximetry does not distinguish between carboxyhaemoglobin (COHb) and oxyhaemoglobin (OHb) and thus gives false normal results for a severely anoxic patient.