Blood gas analysis, performed by trained personnel, is usually done in a hospital, emergency room, surgical center, ambulance, or large laboratory setting because it should be performed immediately after sample collection and specialized equipment is required. Most doctors' offices do not have such capabilities.
2. I've had pneumonia before and currently have asthma. Why has my doctor never ordered this test for me?
Most cases of pneumonia or asthma can be diagnosed by symptoms and monitored by listening to your chest sounds or by examining the results of spirometry tests or chest x-rays. Most of the time, asthma will respond to prescribed medications and pneumonia will respond to rest and possibly antibiotics. Blood gas analysis may be necessary, however, if you have severe or acute breathing problems or prolonged, chronic ones. In these cases, blood gas analysis is usually done in an emergency room or hospital setting.
3. Is there any other way to measure my oxygen levels?
A pulse oximeter is a noninvasive way (no needlestick or blood sample required) of continuously monitoring O2 saturation. A small clip-like device (sensor) is attached to the end of the finger or earlobe. The sensor reads light that is transmitted through the skin. Pulse oximeters are useful for monitoring trends in O2 saturation, but their accuracy can be affected by the presence of abnormal forms of hemoglobin, like carboxyhemoglobin (see below), low blood pressure due to poor perfusion (pumping of blood into an organ or tissue), and very low levels of hemoglobin due to severe anemia.
4. Why does my lab report also list carbyoxyhemoglobin? What is it?
If your blood gases were measured using an instrument known as a co-oximeter, then your lab report may also list results for carboxyhemoglobin and other altered forms of hemoglobin. A co-oximeter is a blood gas analyzer that can measure concentrations of hemoglobin derivates (like carboxyhemoglobin) in addition to the usual blood gas measurements. A co-oximeter is not always used, so these values are not reported for all blood gas analyses.
Carboxyhemoglobin is an altered form or derivative of hemoglobin that forms when carbon monoxide binds to hemoglobin. Levels of carboxyhemoglobin are often elevated with carbon monoxide poisoning, and a co-oximeter is used to measure carboxyhemoglobin levels and to monitor oxygen therapy. Hemoglobin binds to carbon monoxide about 210 times more strongly than to oxygen. Binding to carbon dioxide significantly decreases hemoglobin's ability to carry oxygen through the body, which can lead to a serious, life-threatening condition.
Other hemoglobin derivates include sulfhemoglobin (or sulfmethemoglobin) and methemoglobin, which may result from the ingestion of certain medicines or exposure to chemicals. These altered forms of hemoglobin, like carboxyhemoglobin, cannot function properly to carry oxygen to tissues in the body and are commonly measured by a co-oximeter.
This article was last reviewed on October 24, 2013. | This article was last modified on December 29, 2014.
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