Polysomnography

After reviewing data from the clinical evaluation, the sleep specialist may recommend further diagnostic testing and order a sleep study. A sleep study is a noninvasive, painless test in which sleep patterns and behaviors associated with sleep are observed and recorded. Overnight sleep studies conducted at the sleep center and administered by a sleep technologist are referred to as polysomnography.

Diagnostic Polysomnography

Polysomnography is considered the “gold standard” in diagnostic testing for most sleep disorders. The technology involves recording various physiological variables simultaneously during sleep through the use of a polygraph.

Sleep is divided into several stages beginning with non-rapid eye movement (NREM) sleep. During this stage, brain waves slow down and eyes move back and forth more slowly than in later stages of sleep. After an hour or two of NREM sleep, brain activity picks up and rapid eye movement (REM) sleep begins.

Most people normally go through four to six sleep cycles during the night, cycling between NREM and REM sleep approximately every 90 minutes. The REM stage usually lengthens with each cycle as the night progresses. The purpose of polysomnography is to trace the events that occur during each sleep cycle so as to detect any abnormalities that may be impeding the normal sleep process.

In a typical polysomnography, information is gathered in much the same way as a polygraph is used for a lie detector test. Various electrodes and sensors are pasted or taped to the patient’s body. As the patient sleeps, data from these electrodes, sensors, and leads are collected, transmitted, and plotted as a series of waveform tracings on a computer located in a nearby room where sleep technologists monitor both the patient and computer screen throughout the night.

The physiological functions monitored during polysomnography generally include brain wave activity, oxygen level in the blood, heart rate, breathing, eye movements, and leg movements. The electrodes that are placed on the scalp, face, chin, chest, and legs monitor brain waves, heart activity, and body movements. The elastic belt that is placed around the abdomen records respirations. The two thin wires that are placed near the nose and mouth record air flow during breathing. The clip placed on the index finger measures the oxygen content of the blood. In addition, audiovisual recordings are also made of the patient as he or she sleeps.

Once the polysomnography is concluded, the test results are scored and forwarded to a board-certified physician for review and interpretation. During the follow-up appointment, the sleep specialist reviews the test results with the patient, discusses the diagnosis, and presents various treatment options.


Titration Polysomnography

If obstructive sleep apnea is diagnosed and either positive airway pressure (PAP) therapy or oral appliance therapy (OAT) is prescribed, a second polysomnography, termed a titration polysomnography, is then conducted to determine the optimal settings on the PAP device or oral appliance to alleviate the sleep apnea.

Titration polysomnography is similar to diagnostic polysomnography in that the same physiological functions are observed and recorded. However, in the titration study, the patient uses a PAP device or oral appliance while sleeping.

During the titration polysomnography, the sleep technologist monitors the patient for signs of sleep apnea and, through a process of trial-and- error, tests various settings on the PAP device or oral appliance to alleviate the sleep apnea. Proper titration of the devices requires identification of the minimum level of air pressure, in the case of the PAP device, or minimum lower jaw protrusion, in the case of the oral appliance, to abolish obstructive apneas and/or hypopneas, oxyhemoglobin desaturation, respiratory effort–related arousals, and snoring in all sleep stages.

Split-Night Study

Generally, the diagnostic polysomnography and titration polysomnography are conducted on separate nights. However, if certain circumstances prevail, the two sleep studies may be combined into one split-night study. For the sleep technologist to convert the diagnostic polysomnography into a titration polysomnography on the same night, obvious signs of sleep apnea must be observed during the first fewhours of the sleep study so that there is enough time during the night to effectively titrate the device. At the end of the study, the device must be sufficiently titrated to alleviate the sleep apnea.

FREQUENTLY ASKED QUESTIONS

What happens during the overnight sleep study?

The sleep study usually begins in the late evening and ends at about 6:00 AM the next morning. Once you arrive at the sleep center for your scheduled study, a sleep technologist will welcome you and show you to your private bedroom.

You may bring items you use for your bedtime routine, and you can sleep in your own nightclothes. The room where the sleep study is conducted is similar to a hotel room; it is dark and quiet during the sleep study. You don't share the room with anyone else. The room has a video camera, so that the sleep technologist can see what's happening in the room when the lights are out, and an audio system, so that he or she can talk to you and hear you from the monitoring area outside your room.

After you change into your sleepwear, the sleep technologist will explain the procedure and what to expect during the night. The technician will prepare you for the study by placing electrodes and sensors on your head, chest, and legs. The areas where the sensors will be attached are cleaned and the electrodes are attached with special gels and paste. Elastic belts with sensors will be placed around your chest and abdomen. Airflow sensors will be placed under your nose and a finger clip will be applied to monitor your oxygen levels. All of the sensors are connected to a small portable box that transmits signals to the sleep monitoring and recording equipment that is in the nearby control room.

If the sleep study is a titration polysomnography, the technician will fit you with a PAP mask and explain how the PAP device works or, alternatively, deliver an oral appliance to you with instruction on its use.

During the sleep study, every attempt is made to allow for a normal night’s sleep. You wear your own sleepwear and can bring your favorite pillow, book or magazine. Showers and basic toiletries are available for your use in the morning. A trained sleep technologist is available to explain the procedure, operate the diagnostic equipment and is stationed all night in an adjacent control room to both monitor the sleep recording and ensure your comfort and well-being.

If you need assistance, you can talk to him or her through the monitoring equipment. The technologist can come into the room to detach the wires if you need to get up during the night.

In the morning when the sleep study is completed, the sensors are removed, and you may leave the sleep center. You're given an appointment for a follow-up visit with your doctor or the sleep specialist.



How should I prepare for my sleep study?

You should eat dinner before coming in for the sleep study. There will be no snacks allowed during the procedure. Avoid caffeinated products, including coffee, colas and chocolate after 12:00 noon on the day of the sleep study. Also avoid napping on the day of the study. You may find that a shower before arriving at the sleep center will make you feel more relaxed. Please remove braids, hair weaves, and hair accessories such as clips and rubber bands. Wash and dry your hair and do not apply any sprays, oils, gels, or make-up.

One adult is required to stay with any patient under the age of 18. If the patient appears ill, he or she may be asked to reschedule. Once the sleep study is started, all books and toys must be put away and cell phones turned off.



How will I be able to sleep with so many things attached to me?

You may find it strange at first, but most people do not find the attached electrodes and sensors uncomfortable or an obstacle to falling asleep. We will make every effort to ensure that you are as comfortable as possible. If a problem arises, your sleep technologist will make adjustments. The bedroom has an open intercom that will enable you to communicate with your technologist at any time.


Can I take my usual medications?

All medications being taken should first be discussed with a physician before making an appointment for a sleep study. Certain medications, such as sleeping pills, stimulants, anti-histamines and drugs for anxiety and depression can interfere with the test results, and may need to be discontinued prior to the evaluation. However, unless instructed otherwise by a physician, you should continue to take all your medications on the day and night of the sleep study.


What happens after the sleep study?

Once your sleep study is performed, a board-certified physician will interpret the results of your study usually within 48 hours. A detailed report of the sleep study will be compiled with treatment recommendations. At the follow-up appointment the findings of your sleep study will be reviewed with you and a treatment plan discussed. Your doctor will continue to meet with you as needed to ensure that your sleep disorder is resolved.


What if I am running late?

Please contact the sleep center directly and let us know of your approximate time of arrival.

Contact Us

Sleep Centers of Texas
7839 Interstate 10 West
San Antonio,TX 78230-4779

Phone: 210.520.8333
Fax: 210.520.8335


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