The overnight pulse oximetry test is a commonly used screening method to assess blood oxygen levels. If you are suspected of having a sleep disorder such as obstructive sleep apnea, your healthcare provider may recommend this test. It is also used to determine eligibility for home oxygen use. 

    This article will provide an overview of the overnight pulse oximetry test, what happens during the test, and how the information obtained is utilized. 

    What Is an Overnight Pulse Oximetry Test?

    Overnight oximetry is a straightforward test that can be easily conducted at home, providing essential information for the initial evaluation of common sleep disorders like sleep apnea. 

    During the test, a plastic clip known as an oximeter is gently placed over the tip of your finger. Think of it as a large clothespin or plastic sleeve that encloses your fingertip. It may be secured with tape, but it does not cause any discomfort and can be easily removed. 

    Typically, the oximeter is connected to a small recording device with a cable, which collects data throughout the night. If you use a continuous positive airway pressure (CPAP) device, the oximeter can be connected to it to record data. 

    Alternatively, newer devices may adhere directly to your skin and provide similar measurements. Inside the overnight oximeter sensor, there is a red light that shines through your finger or skin surface. 

    On the opposite side, or sometimes alongside the emitting light, there is a sensor that measures your pulse (heart rate) and the oxygen content in your blood. The oxygen content is determined by the color of your blood, which varies depending on the amount of oxygen it carries. Well-oxygenated blood appears redder, while oxygen-poor blood appears bluer. This alters the frequency of the reflected light wavelength detected by the sensor.

    During the Test

    Pulse oximetry data is continuously recorded throughout the night, resulting in a graph. Your healthcare provider will review the data to identify any abnormal drops in oxygen levels, known as desaturations. These desaturations can occur repeatedly in individuals with sleep apnea.

    Additionally, oxygen levels may remain consistently low, particularly in individuals with underlying lung conditions such as chronic obstructive pulmonary disease (COPD) or emphysema. Desaturations in oxygen levels can be accompanied by an increase in heart rate.

    These events may indicate the presence of sleep apnea, as the periodic pauses in breathing and subsequent drops in blood oxygen levels trigger a surge of cortisol (a stress hormone) that affects the heart.

    Interpreting Results

    Typically, oxygen levels below the following thresholds are considered abnormal: 

    • 88% in adults 
    • 90% in children 

    Levels lower than 88 percent indicate a condition known as hypoxemia. When hypoxemia occurs, oxygen levels can be significantly reduced. Desaturations below 80% are generally classified as severe. 

    These decreases in blood oxygen levels may necessitate treatment. If sleep apnea is the underlying cause, CPAP or bilevel therapy can be effective. 

    However, in the absence of sleep apnea, supplemental oxygen may be required to correct the abnormality. This involves delivering oxygen through tubing to a nasal cannula from an oxygen concentrator or tank.

    Overnight Oximetry – Pros and Cons

    Overnight oximeter devices are increasingly available to consumers, with the option to purchase them online or at pharmacies. While overnight oximetry is a convenient and affordable option, it does have limitations. 

    Oximeters can only provide a limited amount of information and may not be able to detect certain subtleties related to sleep disorders. Factors such as sleep position and sleep stages, such as sleeping on your back or during REM sleep, can affect oxygen levels, which simple devices may not be able to identify. 

    Despite these limitations, overnight oximetry can still be useful in identifying individuals who may require further testing, such as polysomnography or more extensive home sleep apnea testing. It can also be helpful in monitoring the effectiveness of sleep apnea treatment and ensuring that any prior oxygen desaturations have been resolved. 

    However, it’s important to note that overnight pulse oximetry alone may not be sufficient for a diagnosis. Additional tests, like polysomnography, may be necessary before your healthcare provider can provide a definitive diagnosis.

    A Word from Apurva Advanced Medical Care

    Overnight pulse oximetry is a diagnostic examination that allows you and your healthcare professional to assess your respiratory patterns during sleep. This examination can provide indications of specific sleep disorders such as sleep apnea, as well as more severe pulmonary conditions like emphysema.

    Oxygen supplementation may be beneficial for improving sleep and overall well-being in cases where oxygen levels are low without sleep apnea. These oximeter devices collect data, and it is your responsibility to communicate any concerns to your healthcare provider.

    If you have concerns about abnormal oxygen levels during sleep, it is important to discuss the need for further testing and treatment with your healthcare provider at Apurva Advanced Medical Care. Monitor your oxygen level while you sleep using overnight pulse oximetry.