Carbon monoxide poisoning is currently and has been for many years the leading cause of death by accidental poisoning in the United States. Sublethal exposure is difficult to quantify due to the frequent misdiagnosis of acute poisoning as something other than CO intoxication. The principal sources of this gas are internal combustion engines and appliances burn­ing fossil fuels. Carbon monoxide poisoning exerts its effects by binding to hemoglobin, leading to tissue hypoxia. Diagnosis is often difficult due to the non­specific nature of presenting signs and symptoms, but a COHb level is often definitive. The severity of exposure can be graded by CO levels found in blood, with different treatment regimens recommended for each; however, hyperbaric oxygen is the best treat­ment for all cases if it is readily available. buy female viagra