As I mentioned earlier, sleep laboratories are the places where many paratemetrers of patient such as brain waves (EEG) and eyeball movement (electro-oculagram), muscle tension (electromyogram), respiratory movements and breathing air quantity, body movement etc. are shown on paper and examined. In sleep laboratoryies, it is provided conditions which are partly similar to that of the patient's own home environment. Here, patients are obliged to sleep with sensors placed on various parts of their bodies. These sensors are adhered to body surface with special substances; and it is given important to not to disturb the patient's sleep. It is not given them any medication for sleep. In order to examine the patients, it is expected their habitual sleep hours and it is tried to see their sleep as natural as possible. As you can imagine, it is not possible to monitor a fully natural sleep while patient is connected to devices in a totally foreign environment. However, the examinations made under these conditions are generally sufficient for diagnosis of suspected sleep disorders of patients. When it is considered that it is necessary to obtain more detailed and accurate information; the examinations are repeated a second night; thus, closer data to natural sleep is obtained.
When you analyze the sleep of patients who suffer from insomnia, the first thing you notice is that; their sleep is divided to short or long -term awakenesses.
Although some patients are not fully woken from sleep, or they do not feel that they are awake; it is noticed in the examinations that, their sleep often becomes superficial and it is often returned to the superficial period of sleep. During analysis, it is detected that; the number of patients’ wakefulness and the number of sleep phase changes are increased. Although it is not seen in all patients, normal sleep latency –which should be between 10-30 minutes – is prolonged in these patients. The objective indicator of the quality of sleep; the rate of sleep time to the time spent in bed (sleep efficiency) is reduced in these patients.
As any reduction in sleep duration occurs especially in the 2nd phase; it may not be seen a significant decrease in the duration of 3rd and 4th phase sleep –which is described as real sleep - and the REM sleep.
Another characteristic detected during the laboratory tests of sleepless patients is the change named as alpha- delta sleep. In these patients, 8-12 Hz frequency of brain waves observed in wakefulness are added to 1-4 frequency of brain waves observed in deep sleep during the sleep. Although patients are considered as sleeping based on objective data, the tiredness they feel when you wake up in the morning may be because of the wakefulness waves incorporated in the sleep.
As patients suffering from insomnia know very well, sleep of our patients is very variable. Although some patients sleep relatively better certain nights of the week, they can not sleep other nights. Considering that variability may occur both between nights and patiensts; it is seen that, the results obtained in sleep laboratories are global assesmentents. Therefore, data obtained in sleep laboratories should be assessed together with the patient’s complaints.
In order to peform correct assessments, patients should sleep several nights in a row in the laboratory. The first night spent in the laboratory is called as habituation night; and that night, it is ensured that; the patient habituates to foregn environment.During habituation night, generally it is detected frequently interrupted, short time sleep; but unlike the others, some patients sleep much better than they sleep in their own homes and they get surprised when they wake up in the following morning. This kind of sleep pattern which is called as “reverse first night effect”is generallay as a result of patient’s feeling himself confortable in a safe and different environment like hospital. Reverse first night effect is seen more frequently on patients who has psychophysiological insomnia, meaning the insomnia which is happened as a result of negatively conditioning to sleep or to sleep environment.
Except the aforementioned characteristics, when the patients suffering from insomnia are examined in sleep laboratories, the main aim is diagnosing diseases such as periodic movements in sleep and breath-disorder in sleep etc. which are considered as the reasons of insomniaand accepted as primary sleep disorders.