If you suspect a sleep disorder , such as obstructive sleep apnea, your doctor may recommend that you undergo nocturnal pulse oximetry, a widely used screening test that measures the level of oxygen in your blood. This test is also used to determine eligibility for home oxygen use.
What about this test? How is the information used? Learn about oximetry and how to measure your breathing while you sleep.
What is pulse oximetry?
Night oximetry is a simple test that can be easily performed at home. Provides basic information that may be helpful in initially evaluating whether you have one of the most common sleep disorders, sleep apnea .
The test usually involves placing a plastic clip on the tip of the finger. Imagine a large clothespin or plastic sleeve covering the tip of your finger. This clip can be held in place with a piece of tape, but it is painless to apply and easy to remove.
It is usually connected by a cable to a small box that records data overnight. If you are using continuous positive airway pressure (CPAP) , you can connect it to this device to record data. Newer devices can adhere directly to the skin and provide similar measurements.
There is a red light on inside the night oximetry sensor. This red light travels through your finger or the surface of your skin.
Often on the other side, and sometimes in parallel with the emitting light, there is a sensor that can measure your pulse (or heart rate) and the oxygen content in your blood. The latter is determined by the color of your blood, which will depend on the amount of oxygen it contains.
High-oxygen blood is redder, while low-oxygen blood is bluer. This changes the frequency of the light wave that is reflected off the sensor.
During the exam
Pulse oximetry data is continuously recorded overnight and displayed as a graph. Your doctor will be able to examine you and determine if there are abnormal drops in oxygen levels called desaturation. This can happen intermittently with sleep apnea .
Decreased oxygen saturation may be associated with an increased heart rate. These events can indicate the presence of sleep apnea because it includes intermittent pauses in breathing and a decrease in blood oxygen levels, leading to an increase in cortisol (a stress hormone) that affects the heart.
interpretation of results
It is generally considered abnormal if oxygen levels drop below 88% in adults or below 90% in children. If the levels are below 88 percent, a condition called hypoxemia can be diagnosed. These levels can be very low and, in general, a decrease in saturation to less than 80% is considered serious.
Such a decrease in blood oxygen levels may require treatment. If the underlying cause is sleep apnea, then CPAP or bi-level therapy may be effective.
However, in the absence of sleep apnea, the use of supplemental oxygen through a tube to the nasal cannula from an oxygen concentrator or oxygen cylinder may be necessary to correct the abnormality.
Pros and cons of nocturnal oximetry
This screening test is simple and inexpensive, but it is not ideal. The devices are becoming more affordable for consumers. They can be purchased online or even at a pharmacy. What value can these measures offer?
Oximeters provide only a limited amount of information. Additionally, there are subtleties associated with sleep disorders that cannot be detected. For example, sleeping position (especially sleeping on your back) and stages of sleep (especially REM sleep) can affect the rate of oxygen change. Simple devices cannot determine this contribution.
Nighttime oximetry alone is not sufficient to diagnose sleep apnea and cannot be used for insurance purposes to qualify for treatment such as CPAP.
However, nocturnal oximetry can be helpful in identifying some people who need additional tests, such as polysomnography or more extensive tests for sleep apnea at home . It may also be helpful to ensure that sleep apnea treatment is effective and that the oxygen desaturation seen in previous diagnostic tests is gone .
Get the word of drug information
If you are concerned that your oxygen levels may be abnormal while you sleep, speak with your doctor about the need for further testing and treatment. When oxygen levels are low but sleep apnea does not occur, supplementation with oxygen can also help you fall asleep and feel better. These oximeters collect data, but you should take action and report any concerns to your healthcare professional.