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What Is Overnight Oximetry?

Mary McMahon
Mary McMahon
Mary McMahon
Mary McMahon

Overnight oximetry is a medical test that involves monitoring the level of oxygen in a patient's blood over the course of a night. This test is noninvasive and can be done at home with specialized monitoring equipment. A doctor may recommend it to a patient with disordered sleep to determine if apnea is contributing to the patient's poor sleep patterns. It is an inexpensive test that can provide some important baseline information to determine if a patient needs additional screening, like a sleep study in a hospital or clinic.

In the process of overnight oximetry, the patient puts a small clip on one of the fingers. The clip shines a light through the finger, collecting data about the level of oxygen in the blood by recording the absorption rate of the light as it passes through the finger. It feeds this information to a small recording box via a thin cord. Many patients tape the cord to the hand to keep it from becoming tangled during the night. At the end of the night, the patient can take the clip off, and the overnight oximetry study is complete.

Supplemental oxygen may be used if a patient struggles to maintain adequate overnight oximetry levels.
Supplemental oxygen may be used if a patient struggles to maintain adequate overnight oximetry levels.

If oxygen levels change during the night, as would be expected if the patient has sleep apnea, the change in readings would show on the data. A doctor can analyze the data from the study to determine if there are any changes. The patient needs to keep a diary that the doctor can compare with the results; if the patient had to move the clip to a different finger, get up to use the bathroom, answer the phone, or engage in other activities, these could skew the results and might create a spike or dip in the oxygen level.

Overnight oximetry testing may be ordered if a patient has trouble remaining awake at work.
Overnight oximetry testing may be ordered if a patient has trouble remaining awake at work.

The test results may suggest that the patient's oxygen levels remain stable through the night. In this case, the overnight oximetry indicates that the patient's trouble sleeping is not the result of apnea, and that something else, such as stress, may be causing the problem. If the results show changes in oxygenation levels, the patient may need more testing to address the possibility of apnea and to develop a treatment plan that may help.

In many instances, sleep apnea is diagnosed following a sleep study.
In many instances, sleep apnea is diagnosed following a sleep study.

Diagnosis of sleep apnea can be a complex process. Overnight oximetry provides a middle point that allows a doctor to collect information at low cost to determine whether a patient appears to have problems with oxygenation during the night. Full sleep studies can be very expensive, and the provision of an alternative test can help cut costs for diagnosis and treatment. Patients may also find the test more pleasant than a sleep study. It is often difficult to sleep in a hospital or clinic, even in rooms designed for sleep studies, and the testing is more intrusive.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a TheHealthBoard researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Learn more...
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a TheHealthBoard researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Learn more...

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    • Supplemental oxygen may be used if a patient struggles to maintain adequate overnight oximetry levels.
      By: Leah-Anne Thompson
      Supplemental oxygen may be used if a patient struggles to maintain adequate overnight oximetry levels.
    • Overnight oximetry testing may be ordered if a patient has trouble remaining awake at work.
      By: Halfpoint
      Overnight oximetry testing may be ordered if a patient has trouble remaining awake at work.
    • In many instances, sleep apnea is diagnosed following a sleep study.
      By: WavebreakMediaMicro
      In many instances, sleep apnea is diagnosed following a sleep study.
    • Overnight oximetry may be measured using an infrared probe clipped to a fingertip.
      By: Africa Studio
      Overnight oximetry may be measured using an infrared probe clipped to a fingertip.
    • Some research has shown that sleep apnea can be hereditary.
      By: Konstantin Yuganov
      Some research has shown that sleep apnea can be hereditary.
    • An overnight oximetry may be given to a person with disordered sleep.
      By: Karen Winton
      An overnight oximetry may be given to a person with disordered sleep.
    • A CPAP machine may be helpful to individuals who suffer from sleep apnea.
      By: Amy Walters
      A CPAP machine may be helpful to individuals who suffer from sleep apnea.
    • A doctor analyzes the data gathered during overnight oximetry in order to determine a diagnosis and course of treatment.
      By: Monkey Business
      A doctor analyzes the data gathered during overnight oximetry in order to determine a diagnosis and course of treatment.