The Stanford Center for Sleep Sciences and Medicine

Sleep Study Results

When Will Results from Sleep Study be Available?

Diagnostic Studies

For diagnostic sleep studies you can anticipate receiving a written report detailing the results of your sleep study within 2 weeks. This will allow time for our technologist to carefully score the stages of your sleep as well as the various events (e.g., abnormal breathing, leg movements, heart rate changes) recorded during your sleep study. A physician will also independently review your study and finalize the interpretation. If you received positive airway pressure treatment during your diagnostic study, please refer to the additional information in the next section.

Positive Airway Pressure (PAP) Studies (CPAP Titration Study, Bilevel Titration Study, etc.)

For a positive airway pressure (PAP) treatment study, you can anticipate receiving a written report detailing the results of your sleep study within 2 weeks. Your study will be scored by a technologist and interpreted by a physician from the center as described in the prior section. You may receive your prescription before your detailed PAP treatment study report. Your prescription will include specifics regarding the type of machine, the settings of your machine, the type of mask/interface, and the PAP accessories needed for your care. There will also be a list of durable medical equipment (DME) companies in the Bay area where you can obtain your equipment. We advise that you obtain your equipment and then follow-up with us.

Understanding Sleep Study Results

After your sleep study, a doctor will review the entire record and the study will be scored by a sleep technologist.  A comprehensive report will be generated to summarize the results.  This report is a very useful tool for your physician to assess your sleep, however it can be boiled down to a few key pieces of relevant information used to determine whether or not you have sleep apnea.  There are a few key terms you should know when reviewing your sleep study results. 

Apnea Hypopnea Index (AHI) or a Respiratory Disturbance Index (RDI)
Abnormal breathing is summarized by either an Apnea Hypopnea Index (AHI) or a Respiratory Disturbance Index (RDI).  The terms are very similar but have slightly different definitions. 
Your AHI is the average number of apneas and hypopneas per hour of sleep and is calculated by taking the total number of apneas and hypopneas and dividing it by the number of hours of sleep.   Your RDI is the average number of abnormal breathing events that occurred per hour of sleep, so it may include abnormal breathing events other than apneas and hypopneas such as Respiratory Effort-Related Arousals (RERAs).  The higher your RDI or AHI, the more severe the disorder.

Typically we recommend treating an AHI over 5 or 10, which is considered mild sleep apnea.  If you think about it, 10 breathing events per hour means that you are waking up every six minutes – it’s like sleeping with a snooze alarm all night.

Desaturation Index or Low Oxygen Level
During an overnight sleep study, your oxygen saturation is measured continuously using a sensor worn on the finger called a pulse oximeter.  During an breathing event, it is not uncommon for the oxygen level in the blood to decrease in response to the limitation in airflow.  The desaturation index reflects the average number of times your oxygen level dropped by 3 or 4% per hour of sleep.  The term for a having a low oxygen level is hypoxic and your doctor will be very interested in your lowest oxygen level during the night as well as the frequency of the desaturations.

Sleep Onset
If you have a sleep study in a lab, we are able to determine whether you are awake or asleep at any given moment during the sleep study.  How quickly you fall asleep is of interest because it can be a way to measure how sleepy you are.  Sleep onset is the number of minutes it takes you to fall asleep once the test is officially started.  It usually takes a healthy sleeper about 10 or 15 minutes to fall asleep at home, so in a sleep lab it may take 15-30 minutes.  It is not uncommon for someone with sleep apnea nod off in under 5 minutes at the sleep lab while it may take someone with difficulty initiating sleep over an hour to fall asleep. 

Will My Doctor Get the Results?

Your physician will be sent your sleep test results if you indicate a primary care physician when you register as a patient with the Stanford Hospital and Clinics. When you arrive for your scheduled appointment, please confirm and update your referring and primary care physician information.

Do I Need to Come Back to the Sleep Center?

Diagnostic Studies Follow Up (CPAP Titration Study, Bilevel Titration Study, etc.)

We would like you to return for a daytime appointment with us 2-3 weeks after your diagnostic sleep study. Patients referred to our center for a sleep study should follow-up with their physicians as instructed.

Positive Airway Pressure (PAP) Studies

We would like you to return for a daytime appointment with us 6-8 weeks after you obtain your equipment, since it may take 3-4 weeks to become used to the machine and an additional 3-4 weeks to start noticing effects of the treatment. Please bring your PAP machine including the mask and other accessories to your follow-up visit. Patients referred to our center for a sleep study should follow-up with their physicians as instructed.

 

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