A pulse oximetry test can give the saturation of oxygen in your blood by transmitting light through your tissues. It You may need to have your blood oxygen level tested prior to surgery or other medical procedures, or if you have certain conditions, such as:Sleep apnea
A heart attack or congestive heart failure
Chronic obstructive pulmonary disease (COPD)
Anemia
Lung cancer
Asthma
Pneumonia
Cystic fibrosis
A current or possible need for mechanical ventilation to support your breathing

, The pulse oximetry method of measuring blood oxygen level is non-invasive, so there is usually little you need to do to prepare for the test.However, your doctor will still discuss the test with you and answer any questions you may have.


You may be asked to remove fingernail polish, if applicable.
Your doctor may give you other specific instructions for preparation, based on your medical condition and history.
 There are very few risks associated with pulse oximetry.These are minimal, but include:


Skin irritation at the application site. This may occur with prolonged or repeated application of the probe sensor.
Inaccurate readings in cases of smoke or carbon monoxide inhalation.
Your doctor can let you know if there are any additional risks, based on your specific medical condition.
 The sensor used to measure the oxygen level of blood by pulse oximetry is a clip-like device called a probe.The probe sensor contains a light source, a light detector, and a microprocessor. The light emitted from the source on one side of the clip passes through your skin and reaches the detector on the other side of the clip. The microprocessor does calculations based on the information received from the detector in order to calculate the oxygen level of your blood with a very small margin of error.
 Usually, a finger, ear, or nose is chosen as the site to attach the sensor.The sensor will then use light to measure the oxygen level of your blood.


This method has the advantage of being painless and noninvasive, since no needles are involved.However, it is not as accurate as an arterial blood gas test, so in some cases, both tests may need to be performed.Your health professional cannot attach the sensor to an area with excessive movement or tremor, or with bruising.For example, if you have a dark bruise under your fingernail, your health professional may place the sensor on your ear instead.
 The sensor’s microprocessor will compare the transmission of two wavelengths of light, red and infrared, as they pass through the relatively thin skin of your finger, ear or other site.Hemoglobin in your blood that has absorbed oxygen absorbs more infrared light, while hemoglobin lacking oxygen absorbs more red light. The sensor calculates the difference between these two values to provide information for deriving your blood oxygen level., If you are having your blood oxygen level measured for a one-time reading, then once the sensor has taken the necessary measurements and completed its calculations, the probe can be removed.In some cases (such as for certain congenital heart conditions), however, your doctor may require you to wear the probe for continuous monitoring.If you are asked to do this, remove the probe sensor only when your doctor tells you to.
 Most of the time, there are no special restrictions following the pulse oximetry test, and you can immediately return to normal activities. Depending on your individual medical condition, however, your doctor may give you special post-procedure instructions.
 Once your doctor has the results of your pulse oximetry test, he or she will review them with you.An oxygen saturation level of about 95% is described as normal.Your doctor will discuss the implications of your test results with you, including how certain factors may alter the results of the test, including:


Decreased peripheral blood flow
Light shining on the oximetry probe
Movement of the test site area
Anemia
Abnormal warmth or coolness at the test site area
Sweating at the test site area
Recent injection of contrast dye
Smoking tobacco
Contact a health professional to receive a pulse oximetry test.
Prepare for the procedure.
Know the risks.
Have your health professional prepare the sensor.
Have your health professional attach the sensor to your body.
Let the sensor perform a reading.
Remove the probe.
Follow post-procedure instructions.
Interpret the results.
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