Polysomnography is a test used to diagnose sleep disorders. For this purpose, an electrical recording is made of brain waves during wakefulness and sleep. Its most frequent use is to diagnose Obstructive Sleep Apnea Syndrome (OSAS), in which there are decreases in the percentage of oxygen in the blood repeatedly throughout the night due to airway obstruction.
What is analyzed?
During a polysomnography, several types of sensors are used that record different biological parameters such as:
- Brain electrical waves (EEG).
- Blood oxygen level (PsO2)
- Heart rate (HR)
- Respiratory rate (Fr)
- Eye movements (EOG)
- Leg movements (MPP)
- Body position (POS)
- Snoring
With these elements the physician is able to identify the different parts of sleep and its two main components, REM and non-REM sleep.
For which cases is it indicated?
The sleep study is recommended in cases of:
- Patients with excessive daytime sleepiness.
- Snoring
- Uncontrolled hypertension
- Suspected Sleep Apnea Syndrome
- Suspected Restless Legs Syndrome
- Parasomnias or sleepwalking
- Suspected epileptic seizures
- Study of insomnia in some cases
Preparation for the test
It does not require any specific preparation except to wear freshly washed hair and without having applied body creams. It is also necessary to be willing to sleep. Electrodes will be attached to the patient’s head, as well as various types of sensors on the face, around the abdomen and thorax, on the legs and on the finger.
Polysomnography is a difficult to interpret test that must be performed by accredited sleep experts with specific training such as Clinical Neurophysiologists.
They are performed in specific sleep units in hospitals and clinics. These units resemble hotel rooms where the person undergoing the test will spend the whole night sleeping while their sleep activity is studied.
There is also a type of home polysomnography. Although it has the advantage that it is performed from home it is much less reliable.