Studies During the Sleep

​Sleep polygraph

In the main, a short sleep polygraph examines respiratory disturbances during sleep. The most common finding is obstructive sleep apnoea in which the patient presents with discontinuous snoring and episodes of apnoea during sleep and this weakens the sleep quality, causes daytime fatigue and increases the risk of cardiovascular diseases. In addition, a sleep polygraph can detect the periodic movement disorder of the legs during the night that is often related to restless legs syndrome.

The examination is performed at night in the patient’s home. In the afternoon preceding the night of the examination, the patient picks up the examination equipment from the KNF ward and is given instructions on how to set it up at home in the evening. If the patient so desires, some of the sensors can also be left in place during the instruction visit. In most cases, the device is programmed to operate between 10.00 p.m. and 9.00 a.m. and, in the morning, the patient should return the device to the ward with the sleep survey forms.

The study measures the respiratory airflow, respiratory movements of the chest and diaphragm, blood oxygen concentration, heart rate, snoring, sleeping position and leg movements. The examination is painless and the device should not disturb sleep to a notable extent. Acute respiratory tract infection forms a contraindication for the examination, in which case the examination needs to be postponed. Careful adherence to the instructions is crucial for the success of the study. If repeatedly unsuccessful at home, the sleep polygraph can also be performed in hospital.

Based on the quantity, quality and consequences of abnormal events during the night, the occurrence and severity of respiratory disturbances during sleep or movement disorder of the legs can be assessed. In some cases, the examination is used to assess the effect of therapy on sleep apnoea.


Polysomnography

An extensive polysomnography is used to examine a range of sleep disorders. These include respiratory disturbances during sleep, periodic limb movement disorder, REM sleep behaviour disorder, disorder in experiencing sleep duration and excessive sleepiness diseases (narcolepsy and hypersomnia). A polysomnography is also used before a multiple sleep latency test (link) to ensure an adequately long sleep before the test.

During the preparation phase for the examination, the referring physician may give some instructions regarding the gradual ending of some pharmaceuticals affecting the structure of sleep.

The examination is performed at night in the patient’s home. In the afternoon preceding the night of the examination, the patient picks up the examination equipment from the KNF department and is given instructions on how to set it up at home in the evening. Some of the sensors are left in place during the instruction visit. In most cases, the device is programmed to operate between 10.00 p.m. and 9.00 a.m. and, in the morning, the patient should return the device to the ward with the sleep survey forms.

The study measures the EEG or electrical activity of the brain, eye movements, muscle tone, respiratory airflow, respiratory movements of the chest and diaphragm, blood oxygen concentration, heart rate, snoring, sleeping position and leg movements. The examination is painless and the device should not disturb sleep to a notable extent. Acute respiratory tract infection forms a contraindication for the examination, in which case the examination needs to be postponed. Careful adherence to the instructions is crucial for the success of the study.

The polysomnography can also be performed in hospital if it is repeatedly unsuccessful at home and also if there is a need to video record the patient's behaviour during sleep for the purpose of diagnosing night-time seizures, for example.

The relative proportion of sleep phases, number of awakenings and sleep cycles provides information regarding the quality of sleep. Based on the quantity, quality and consequences of abnormal events during sleep, the occurrence and severity of respiratory disturbances during sleep, movement disorder of the legs or some other sleep disorder can be assessed.