The basics of PSG:
One of the diagnostic tools used in sleep medicine is
polysomography (PSG), a type of sleep study. It is used to diagnose or rule out
sleep disorders. It records several physiological variables, such as eye
movements, brain functions, muscle activity, heart rate, respiratory effort,
and oxygen saturation.
Typically, about 12 channels are recorded through PSG. Depending
on the condition of the patient, more channels may be added. Patients with sleep-related
breathing disorders may be studied using more measurements, such as esophageal
pressure and expired air carbon dioxide, which provide clarification on the
respiratory status. Patients with movement disorders may have electrodes put on
multiple muscles and so on.
The procedure:
The examination normally takes place at night, but can
happen during the day for day shift workers. The patient needs to report to the
laboratory about 1.5 hours before his normal bedtime to ensure there is enough
time to apply the electrodes. Then, the lights are turned off and the patient is
allowed to sleep overnight. The recording times normally last about 7.5-8
hours.
Components of a PSG:
- Electroencephalogram (EEG): measures electrical activity of the brain
- Electrooculogram (EOG): measure activity of the eyes
- Electromyogram (EMG): monitors leg movement during sleep
- Electrocardiogram (ECG or EKG): measure electrical activity of the heart
The results of a PSG:
The technician uses the information from the test to chart
the patient’s sleep stages and cycles. This report is analyzed by the
physician.
One of the components of the report includes the
Apnea-Hypoapnea Index (AHI). This number is the number of apneas and hypoapneas
in one hour during the sleep study. An apnea is the cessation of breathing for
at least 10 seconds, while a hypoapnea is a decrease of airflow that lasts at
least 10 seconds. Based on the AHI, we can tell how severe OSA is:
Some patients have an abnormally high AHI, sometimes
even above 100. This shows the seriousness of the obstructive sleep apnea and
how necessary it is to seek treatment before it causes problems in other parts
of the body. - · AHI<5: minimal OSA
- · 5≤AHI<15: mild OSA
- · 15≤AHI<30: moderate OSA
- · AHI≥30: severe OSA
Until next time!
Source: Reite, Martin, Michael P. Weissberg, and John Ruddy. Clinical manual for the evaluation and treatment of sleep disorders. Washington, DC: American Psychiatric Pub., 2009. Print.
Source: Reite, Martin, Michael P. Weissberg, and John Ruddy. Clinical manual for the evaluation and treatment of sleep disorders. Washington, DC: American Psychiatric Pub., 2009. Print.
Are there multiple trials conducted to determine a patient's sleep cycle? Or is only one examination necessary?
ReplyDeleteYou can use one examination because you can attach multiple electrodes based on the kinds of problems the patient exhibits. For instance, if a patient has a possible sleep disorder and possible restless syndrome, the electrodes are going to be connected to different areas of head to monitor the waves as well as muscles in the leg.
DeleteKind of continuing off Victoria's question, how do you know one night of sleep will be representative of how they always sleep? Would sleeping at a lab knowing you are under observation change anything, and do some sleep conditions only happen some of the time or very inconsistently so they might not be observed on the night of study?
ReplyDeletePolysomnography is a method to possibly eliminate certain disorders. The results of an EEG and other tests either show that activity is either normal or abnormal. Yes, it is possible that one night of sleep is not representative of how the patient always sleeps. For this reason, many times neurologists ask for three-day EEGs which are sometimes done at home.
DeleteAre there different treatment plans for the various degrees of severity of sleep apnea based on the Apnea-Hypoapnea Index?
ReplyDelete- Ms. Holtzman
Treatment for sleep apnea are directed at improving breathing during sleep and reducing sleep fragmentation. the types of treatment fall under three different categories: behavioral, medical, and surgical. Behavioral techniques include avoiding sleep deprivation and losing weight. Medical techniques include CPAP Therapy. Surgical techniques include tracheostomy. Depending on the severity of sleep apnea, different combinations of this options may be used. I will talk more about treatment in later posts.
DeleteHi Shubhangi!
ReplyDeleteWith an abnormally high AHI, what would be some of the more common resulting complications and treatments?
An abnormally high AHI, which can be caused by things such as lying on the back and having more REM sleep, indicates severe sleep apnea. This can cause many problems with the heart as we already know. Some of the complications it causes includes excessive daytime sleepiness, higher blood pressure, and liver problems. It can also cause insulin resistance in the patient, thus leading to diabetes.
DeleteAs far as treatment for sleep apnea goes, there are a couple of options: behavioral changes such as avoiding sleep deprivation, medical options like CPAP Therapy, and surgical techniques. None of these guarantee getting rid of apneic episodes during sleep altogether, but they can help lower the AHI. Normally, treatment options are aimed at helping symptoms. So, a combination of these options can be used to provide the patient relief.