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Polysomnogram - PSG Sleep Study
Neurodiagnostic/Sleep Lab, 319-398-6097
What is a Sleep Study?
Formally known as a Polysomnogram, it is a diagnostic test that looks for sleep related breathing disorders as well as parasomnias, like sleep walking and nocturnal seizures. Electrodes and other devices record the body’s electro-physiology while the patient sleeps. Data is displayed as waveforms and stored digitally on a computer for a neurologist to review and interpret.
Why should I have a Sleep Study?
Sleep studies are performed for various reasons:
- Sleep apnea or Narcolepsy
- Nocturnal seizures
- Sleep walking
- Restless leg syndrome
Procedure:
There is no pain involved with a sleep study. Patients are shown to their motel-like room and instructed to get ready for bed. Hospital scrubs are provided for sleep attire. Once the patient is dressed for bed, the preparation begins.
Eight surface electrodes are attached to the scalp with special glue. These determine your level of sleep by recording brain waves and eye movements. Pairs of electrodes are attached to the underside of the chin to record muscle tone. This determines REM sleep as muscle tone disappears in REM.
Electrodes are applied to the lower portion of each leg to monitor leg movements. Two elastic-like bands are placed around the chest and abdomen to record breathing effort. A probe is placed on a finger to record oxygen levels and patches are applied to the chest to record the heartbeat. The technologist is located in an adjacent room with the recording equipment.
Instructions are given over an intercom to the patient to perform some simple tasks in order to confirm all equipment is functioning properly. The study is officially started with a verbal “Good Night” and continues for a minimum of six hours.
If the patient is a child or is having additional testing the following day the recording time may be as long as 7 – 8 hours. If it is felt that enough respiratory events have been documented during the first half of the study, the technologist will fit you with a CPAP interface device.
CPAP stands for Continuous Positive Air Pressure and is the first line of treatment in cases of sleep apnea. CPAP uses room-filtered air to splint your airway and keep it open and supported. It is extremely successful in treating obstructive sleep apnea. Quite often, due to time constraints, patients are required to return for second study to initiate CPAP treatment.
Criteria for applying CPAP/BiPAP during a routine or diagnostic sleep study (all must be met):
- A minimum 120 minutes of sleep must be obtained in the first 3 hours of the study.
- A minimum of 60 respiratory events must be captured in that 120 minutes of sleep to equate to a respiratory disturbance index (RDI) of 20. That is 20 respiratory events per hour of sleep minimum.
- Minimum 2% drop in oxygen saturation with respiratory events (Medicare requires a 4% drop)
Things that make it necessary for patients to return for a CPAP titration study:
- A patient only has apnea when sleeping on their back. (positional apnea)
- A patient only has apnea during a specific stage of sleep. (some apnea only occurs in REM sleep)
- Not enough sleep was captured in the first half of the test.
- Not enough definite respiratory events. If tech is uncertain that criteria has been met, CPAP titration will not be carried out.
- If other conditions exist such as restless leg syndrome.
- It is not uncommon for a patient to return for an additional study with CPAP titration even if CPAP was applied during their first study. Time is limited and if a patient does not sleep well with CPAP on, an adequate pressure setting may not be achieved on the first test. Some patients are required to return for a BiPAP titration study if not responsive to CPAP or tolerant of it.
Upon completion of your study electrodes are removed with a solvent and the majority of glue residue is cleaned out of the hair. Any remaining glue will wash out after several shampoos. Our rooms are equipped with full bathrooms with showers and we encourage you to make use of it before leaving as your testing will be done at approximately 4:30 to 5:00 am and we want you wide awake for your drive home.
We will provide soap, shampoo, deodorant, toothbrush and toothpaste and shaving supplies. A neurologist will interpret your study and dictate a report. This is sent to the referring physician who will discuss any findings and follow up care with you.
Preparation:
ALL PATIENTS: Avoid caffeine and naps the day of testing. Please arrive with clean dry hair and scalp. Refrain from use of products such as hairspray, gel, oil, lotion or mousse. Take medications as you normally would unless instructed differently by your physician.
Outpatient Registration:
Call 319-398-6515 before 2:30 pm M – F to pre-register. Please park in the lot at the corner of 8th Ave and 10th Street. If not pre-registered, register at the Trauma Center Registration Desk on ground floor.
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