The symptoms of obstructive sleep apnea are not very specific. This means that many people who snore at night or who feel tired during the day probably do not have sleep apnea. Other medical reasons for daytime sleepiness should be considered by your doctor before referral to a sleep center for diagnostic sleep tests. They include:
Symptoms or findings that make the need for evaluation by a sleep specialist include:
If symptoms suggest obstructive sleep apnea or other sleep disorders, further diagnostic testing will be performed. A sleep specialist or sleep disorders center will perform an in-depth medical and sleep history and physical exam. Centers should be accredited by the American Academy of Sleep Medicine.
To help determine the presence of sleep apnea, the doctor will ask the following questions:
Keeping a Record of Sleep. To help answer these questions, the patient may need to keep a sleep diary. Every day for 2 weeks, the patient should record all sleep-related information, including responses to questions listed above described on a daily basis. Recording sleep behavior using an extended-play audio or videotape can be very helpful in diagnosing sleep apnea.
To diagnose sleep apnea, the doctor will check for physical indications of sleep apnea, including:
If sleep apnea is not obvious after a physical examination and history, the doctor will need to rule out any other problems. These include sleep disorders, (such as narcolepsy, insomnia, or restless legs disorder), or any medical or psychologic conditions (chronic fatigue syndrome, depression) that may be causing daytime sleepiness.
Polysomnography is the technical term for an overnight sleep study that involves recording brain waves and other sleep-related activity. Polysomnography involves many measurements and is typically performed at a sleep center.
The patient arrives about 2 hours before bedtime without having made any changes in daily habits. Polysomnography electronically monitors the patient as he or she passes, or fails to pass, through the various sleep stages.
Type 1 monitoring consists of full overnight polysomnography, with a minimum of two channels each for EEG to measure brain waves, chin electromyogram, electrooculogram to measure eye movements, as well as respiratory airflow (with thermistor or pressure-flow transducer), respiratory effort (thoracic and abdominal breathing movements), oximetry, and ECG or heart rate monitoring.
Changes in breathing and blood oxygen levels are also recorded. In patients with suspected sleep apnea, the sleep expert will track instances of apnea and hypopnea that last longer than 10 seconds. In general, if there are more than five episodes per hour, apnea is significant and if there are more than 15, the condition is serious.
Overnight polysomnography has been the gold standard for diagnosing obstructive sleep apnea in both adults and children. It is very labor-intensive and expensive, however, and also misses snoring-induced arousals. After the diagnosis of sleep apnea is made, the patient must come back to the sleep center for another night in order to have CPAP started (CPAP titration).
Split night polysomnography. Because of the extra cost involved for a night at a sleep center, as well as limited resources available to diagnose and treat the many patients with obstructive sleep apnea, other methods have been developed in order to make diagnosis and initiation of treatment more efficient and less expensive. Split night polysomnography is one such technique. Based on criteria involving risk factors the patient may have, the severity of sleep apnea and whether it has been diagnosed in the first part of the evening, some patients may be progressed to titration for CPAP during the second part of the night. While this type of protocol is not fully accepted by all sleep centers, studies have demonstrated it to be effective when patients are chosen correctly and protocols are followed correctly.
Many doctors are suggesting moving towards home studies. One option is performing home studies first on patients considered to be at high probability for obstructive sleep apnea. Patients receive home sleep testing followed by auto titration of CPAP if necessary Patients who have a negative test or one that is not clear should have a follow-up in a sleep center for polysomnography. High quality studies have shown this to be effective.
A number of portable devices are available, or being developed, so that patients have the convenience of being monitored at home. Devices that can accurately diagnose sleep apnea and titrate CPAP may eventually replace the need for many overnight sleep studies or the need for attended monitoring at home. These home devices can be very different from each other. Some are able to measure all the different factors that a sleep study performed at a sleep center is able to measure. Others are only able to measure some of them and may not get the full picture or accurate diagnosis.
Another concern is that there is no observation of the patient while asleep. As a result, the volume of the snoring, the position of the patient while sleeping, and any other unusual behaviors are not observed. While these data are not essential for the diagnosis of sleep apnea, they may be important in order to provide a complete picture.
Studies have shown that home sleep studies, especially those that measure most or all of the factors measured in a sleep center, are considered accurate for patients who are considered likely to have sleep apnea after history and physical exam. It is important that these patients not have any complicating issues present.
A percentage of patients, however, will need to undergo polysomnography in the sleep center due to findings from a home study that cannot be interpreted clearly.
Unattended Monitoring with Auto-CPAP. This home monitoring method is a recent and simple technique for detecting impaired breathing. It uses an auto-CPAP machine, which is programmed to apply pressure through the airways via a tube that attaches to a mask that fits the nose. A monitor is attached that digitizes and records on a computer all the information on any apnea episodes during sleep.
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