]> 2026-07-31T09:40:52+00:00 WBR0867 0 en A This curve refers to the oxygen dissociation trend of myoglobin, typically exponential not sigmoid in shape due to the lack of allosteric interactions. B This curve typically depicts a left shift of the normal oxygen dissociation curve seen in situations of hypothermia, alkalosis, and low CO₂ concentrations. C This curve represents the normal oxygen dissociation curve with typical P50 (50% of Hemoglobin saturated) at approximately 26 mmHg of PO₂. D This curve typically depicts a right shift of the normal oxygen dissociation curve seen in situations of hyperthermia, acidosis, exercise and high CO₂ concentrations. E This curve depicts both a left shift and a decrease in hemoglobin saturation usually seen in patients with CO poisoning. Carbon monoxide (CO) is an odorless toxic gas released in the process of incomplete combustion. Hemoglobin binding sites have 250 times better affinity to CO than to oxygen. This would typically cause rapid binding of CO as well as cause conformational changes in the hemoglobin molecule leading to increased affinity to oxygen. While CO occupies oxygen binding sites, it decreases the oxygen saturation of hemoglobin. In addition, as it increases affinity of hemoglobin to oxygen it causes a left shift leading to a decrease in oxygen dissociation at the peripheral tissues. Both of those phenomena combined would lead to the red curve seen in the graph above.<br/> '''Educational Objective:''' Carbon monoxide poisoning causes 2 distinct effects on the oxygen dissociation curve: a left shift and a decrease in hemoglobin oxygen saturation.<br/> '''References:''' Ernst A, Zibrak JD. Carbon monoxide poisoning. N Engl J Med. 1998;339(22):1603-8. Pathophysiology E Pulmonology 2020-10-28T01:55:48Z 2459150.5804167 WBR0867