If you or your doctor suspect you may have sleep apnea, you will need to undergo testing to verify the diagnosis. There are multiple types of sleep apnea, including obstructive, central, and complex sleep apnea. Sometimes multiple studies are needed to determine which type of sleep apnea a patient has and what the best form of treatment for that patient would be. The first step is to go over your clinical symptoms, such as snoring, excessive daytime sleepiness, morning headaches, and so on. A form to assess your level of sleepiness or likeliness of having obstructive sleep apnea (OSA) is usually completed as well. Two common questionnaires that are used for this are called the Epworth Sleepiness Scale (ESS) and the STOP-BANG questionnaire.
Next, a sleep study will need to be done. A home sleep test (HST) is usually ordered first and then, if necessary, a more advanced sleep study will be ordered. A lot of the time, you can get the results you need with just an HST. When an HST is ordered, the patient must first attend a class on how to properly use the HST kit. The kit consists of a band that wraps around the chest, a nasal cannula, and a pulse oximeter that is used on a finger. The patient then brings the kit home and performs the sleep test. The data is wirelessly transmitted to the sleep lab. The HST kit should be returned the next day. The sleep technologists and physician will review and interpret the data to provide the results.
There are also in-lab sleep studies, also known as a polysomnograms (PSG). Most insurance companies will only approve an in-lab sleep study if one or two HSTs have been performed and did not show OSA or if there is a reason a patient is not able to perform the test on their own, such as a physical or mental disability. This test is similar to an HST, but more extensive and accurate. In addition to what is worn during an HST, you will also have electrodes attached to your head, face, and extremities. This test also monitors periodic limb movements. The patient stays overnight in the hospital and is monitored all night via a camera in the room and the electrodes. Sleep technologists stay the night, monitoring patients and assisting with temporary electrode removal for bathroom breaks. To obtain accurate and qualifying results, a minimum of 5 hours of sleep needs to be documented.
Further sleep testing can be done using a CPAP and/or BiPAP titration study. These types of sleep studies are usually performed after OSA is diagnosed, to determine the best treatment option or pressure settings. A split-night sleep study is another type of sleep study that where an in-lab baseline sleep study is performed and then transitions to a titration study later in the night, where a CPAP or BiPAP machine is applied and the pressure settings are titrated appropriately for the patient throughout the night. For more complex sleep apnea and hypoxemia cases, titration studies can also be done with other positive airway pressure (PAP) therapies, such as BiPAP-ST and ASV machines.
Two less common sleep studies are the Multiple Sleep Latency Test (MSLT) and the Maintenance of Wakefulness Test (MWT). An MSLT is used to assess the extent of daytime sleepiness to diagnose narcolepsy. This test must be performed the morning/day after a full night PSG has been completed. After waking from the PSG you will get up and change and perform normal morning activities. Then you must go back to bed to try and nap. These naps will be attempted 4-5 times throughout the day at 2-hour intervals. Between naps you can read, watch TV, perform hobbies, or any other normal daily activities. However, strenuous exercise, sleeping when not permitted to nap, or leaving the premises is not allowed.
The Maintenance of Wakefulness Test (MWT) is similar to an MSLT. It is performed to test the ability to remain awake during permissive situations. This is, again, performed the morning/day after a full night PSG has been completed. You must sit or lie comfortably in a room with the lights on and sounds and try to stay awake and alert for 40 minutes. This is done every 2 hours throughout the day. Falling asleep during these periods is abnormal.
Understanding your sleep study results:
The full results will consist of raw data, also known as score sheets, and the interpretation of that data, called the report. The score sheets are created by the sleep technologist and show the actual and analyzed numerical values. The interpretation or report is written by the physician based off of the data from the score sheets. The most important value to look for on your sleep study is your apnea-hypopnea index (AHI). Apnea is breathing cessation and hypopnea is partially obstructed, shallow breathing, or brief breathing cessation. The AHI is the number of times per hour that your breathing is partially or completely obstructed. To be diagnosed with OSA the AHI must be 5 or greater. In certain cases, the respiratory disturbance index (RDI) can be used if the AHI is not high enough, so long as there is a secondary diagnosis or co-morbidity, such as severe oxygen desaturation. If you had an in-lab sleep study you can also look to see if you have occurrences of simple, repetitive, and uncontrolled limb movements. This can be called period limb movement (PLM), periodic limb movement disorder (PLMD), or restless leg syndrome (RLS). These events often disrupt sleep, causing you to wake feeling unrested.
Another value to be aware of is the oxygen desaturation index (ODI). The ODI is the number of times per hour of sleep that the blood oxygen level drops by a certain degree from the patient’s baseline blood oxygen level. When moderate to severe, a nocturnal pulse oximetry test is often done to better assess the severity and treatment needs.
As you can see, sleep apnea can be easy to diagnose and treat, but depending on the severity and complexity, it can also take some time to properly diagnosis and find the appropriate treatment. It is important to discuss your symptoms and diagnosis and treatment plan with a qualified physician.
– Page Maryyanek
*This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.