Animation of oxy and deoxy forms of hemoglobin (from: Molecule of the Month by www.pdb.org, Courtesy: US Federal Government )
A pulse oxymeter can measure if the blood of a patient is oxygen saturated or not, giving evidence about the content of oxygen in the carrier molecule hemoglobin in the red blood cells, the erythrocytes. This optical checking device tests the amount of infrared light, swallowed by oxygen loaded hemoglobin cells. The more oxygen the blood tested contains, the more infrared light can be detected. Hemoglobin loaded with carbon dioxide is absorbing most of the infrared light, telling the physician that he deals with deoxygenated blood of the veins which normally contain the blood returning from the body with low oxygen and high carbon dioxide which is transported by hemoglobin. The color of hemoglobin normally changes when unloading oxygen and uploading carbon dioxide.


Until now it was assumed that diagnosis of low oxygen in usually oygen-rich areas of the blood vessels are evidence for a cardiac insufficiency . Now scientists from the university of Bonn, Germany found (more coincidentally) out that a new type of hemoglobin could have caused mock diagnosis of heart diseases in the past: when examining two patients (father and 4-year old son) with seemingly low oxygen saturation in the blood they diagnosed a cardiac insufficiency, although neither father nor the son showed symptoms.
Taking a closer look to the hemoglobin of both patients Dr. Berndt Zur (workgroup of Prof. Birgit Stoffel-Wagner, pediatric clinic, University of Bonn) found that father and son had an unknow type of hemoglobin which does not change color when un-or uploading oxygen as it has been known, being the background for the optical checking device-method of the pulse oxymeter.
In the future doctors will have to take an ever closer look to their measurements when dealing with cardiac insufficiency.



- A Novel Hemoglobin, Bonn, Causes Falsely Decreased Oxygen Saturation Measurements...Zur et al. Clin Chem.2008; 54: 594-596


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