Generality
Polysomnography is a diagnostic test that individuals with sleep disorders undergo.
During the night, while the patient sleeps, a particular instrumentation detects and records some fundamental physiological parameters, such as brain activity, breathing, oxygen levels, etc.
The polysomnography takes place in a hospital center equipped with the procedure: the examination, in fact, must take place in a very special room, equipped with certain options.
The risks of the test are minimal and the preparation for the exam is extremely simple, as it does not require any special precaution.
Sleep and its phases
Before describing polysomnography, it is appropriate to make a brief reference to the main characteristics of sleep . When one falls asleep, a transient loss of consciousness occurs, some biological functions are reduced and others are strengthened. For example, while the production of corticoid hormones is reduced, that of growth factors increases.
Sleep is characterized by two main phases, which follow one another for several times (4-5 cycles of approximately 90 minutes each):
- NON-REM phase, or orthodox sleep
- REM phase, or paradoxical sleep
Only the correct alternation between these two phases guarantees a restful rest.
THE NON-REM PHASE
It is characterized by 4 stages, during which sleep gradually becomes deeper. The first two stages are, respectively, sleep and light sleep. At the third stage, the deep sleep phase begins, reaching its climax in the fourth stage. It is in this last moment that the organism regenerates itself.
With each new cycle, the NON-REM phase lasts less and less, leaving more space for the REM phase.
THE REM PHASE
During this phase, the sleeping person makes sharp eye movements. The term REM, in fact, is the English acronym of Rapid Eye Movement, that is its own "rapid eye movement".
The REM phase is an "agitated" phase, in which the heart rate and respiratory rate increase and one dreams. However, it is a phase also characterized by a state, induced by hormones, paralysis and muscle relaxation (in Greek paralysis derives from παράλυσις = parálysis, which means "relaxation, relaxation")
What is polysomnography?
Polysomnography is a diagnostic test that records the progress and variations of some physiological parameters during the REM and NON-REM phases, in subjects with suspected sleep disorders.
Figure: polysomnography. Here is where some polysomnograph sensors are applied.
The instrument used to record these parameters is a computerized device, called a polysomnograph ; this instrument is connected to the individual under examination, through skin sensors, located at the end of different cables.
WHAT ARE THE REGISTERED PARAMETERS?
The physiological parameters recorded by the polysomnograph during sleep at night are: brain waves (ie brain activity), oxygen levels, heart rate, breathing, eye movements and limb movements (both upper and lower).
When you run
Polysomnography is indicated when an individual suffers from some sleep disorder.
In fact, the parameters recorded by the polysomnograph allow to establish the anomalies of the REM and NON-REM phases and what alters their correct alternation.
Based on the results of the test, a specialist in sleep diseases is able to assess the nature of the nocturnal disorder and plan the most appropriate therapy.
SLEEP DISORDERS FOR WHICH POLYSONNOGRAPHY IS INDICATED
Polysomnography is carried out when the doctor, on the basis of a preliminary objective examination, suspects that the patient suffers from:
- Sleep apnea syndrome . Also known as nocturnal obstructive apnea syndrome, it causes temporary breathing interruptions during sleep.
- Sleep-related movement disorders . The individual suffering from such problems is the protagonist of involuntary movements, usually with the lower limbs (it is very rare that the arms or hands are moved). Two typical examples of movement-related sleep disorders are: restless leg syndrome (RLS) and periodic movements of the lower limbs.
- Narcolepsy . It is a neurological disease that causes repeated sleep attacks and a continuous feeling of daytime sleepiness. Sufferers fall asleep several times throughout the day, even when engaged in engaging activities.
- Behavioral disorders during the REM phase . People who "physically" live their dreams, with leg or arm gestures, curses, agitation, etc. suffer from these disorders.
- Disorders of behavior during the NON-REM phase (or nocturnal behavioral disorders of the NON-REM phase) . A number of different problems belong to this category, such as sleepwalking and confusion awakening.
- Chronic insomnia . It is the inability to give continuity to nocturnal sleep. Some people are chronically affected.
risks
Polysomnography is a painless and non-invasive test.
The only problems that could arise are related to skin irritations caused by the application of polysomnograph sensors to the skin.
Preparation
Polysomnography requires a very simple preparation, which is easy to follow.
In fact, just a few hours after the exam (starting in the afternoon), it is sufficient not to take alcohol and caffeinated foods or drinks.
For what reason?
Because alcohol and caffeine can disturb nocturnal sleep, altering the results of polysomnography.
Procedure
The polysomnography is performed, of course, at night and in a hospital center equipped for the procedure. The exam, in fact, takes place in a particular room, equipped with everything needed to follow the patient's nocturnal activity step by step. Among other things, the environment also features a camera and an audio system for communication between patient and medical staff.
Key Stages of the Procedure
Arrival
The medical staff requires the patient to arrive at the hospital in the evening, so that there is time to prepare the instrument.
To facilitate adaptation to the new environment, the individual under examination can bring along everything he usually uses at home when he goes to sleep.
Room
The room is similar to a hotel room and is equipped with all comforts, so that the patient can feel more at ease. Furthermore, it is equipped with a camera and an audio system: the camera allows the medical staff to observe what happens inside the room during the night; the audio system, on the other hand, serves to communicate with the outside, in the event that the patient suffers from some illness.
Instrumentation connection
As anticipated, the connection to the polysomnograph takes place through skin sensors, placed at the end of different cables. The cables are long enough to allow the patient any movement at night.
Sensors are applied to the scalp, temples, chest and legs using an adhesive or glue.
The sensor for measuring oxygen levels is an exception, compared to the others: it is, in fact, a sort of clip to be applied generally to the index finger.
Measured parameters
In summary, the parameters measured or monitored during polysomnography are: brain waves (which describe brain activity), eye movements, heart rate, breathing, oxygen levels in the blood and limb movements (both lower that superior).
Duration of registration
Registration begins when the patient falls asleep and ends when the patient wakes up. Generally, in the absence of hitches, it lasts all night.
Support
If the patient feels a sudden illness he has the possibility of communicating it to the medical staff, through the sound system which is fitted to the room for the night. The medical staff is in the immediate vicinity, just outside the room; therefore, he can intervene immediately
Possible problems
It may happen that the patient feels uncomfortable and struggles to sleep, because the examination and the environment, foreign to him, worries him. However, this does not alter the success of the test, as it is sufficient for the patient to sleep a few hours, not necessarily overnight.
AFTER THE PROCEDURE
Upon awakening, the recording is interrupted, the instrument and the sensors are disconnected and the patient can immediately return home.
The results of the examination will be released by the doctor of the hospital center, where the polysomnography took place, only a few days later. Indeed, their interpretation takes some time.
Results
INTERPRETATION OF THE ANALYZED PARAMETERS
Below is a brief description of what they mean (or may mean) certain parameters, recorded during a polysomnography.
- Brain waves and eye movements . Diseases such as narcolepsy and behavioral disorders during the REM phase interfere with brain activity and / or eye movements (NB: the acronym REM stands for Rapid Eye Movement ).
- Heart rate, breathing and changes in oxygen levels . These three parameters undergo strong variations when the so-called sleep apnea syndrome is underway.
- Movements of the limbs, in particular of the legs . Their presence could mean that the patient suffers from some sleep-related movement disorder, such as restless legs syndrome (RLS) and so-called periodic movements of the lower limbs.
- Unusual movements and behaviors during sleep . Unusual gestures and ways of acting during sleep are the possible sign of a behavioral disturbance during the REM or NON-REM phase.
The data emerging from the polysomnography serve to confirm the doctor's suspicions of departure and make it possible to establish the most appropriate therapeutic treatment.
