In the sleep laboratory, doctors analyze how a patient sleeps and what affects his sleep. This allows them to diagnose sleep disorders and find the optimal treatment.
Good sleep is very important for our physical and mental well-being. However, in the US every second adult occasionally has problems falling asleep, staying asleep or both. About one in ten adults even feel that their night’s sleep is often or permanently un-refreshable and thus suffers from a chronic sleep disorder.
In order to determine and analyze a possible sleep disturbance, an examination in the sleep laboratory is suitable. Over 5,000 of these specialized medical facilities are currently in the USA. While the patient sleeps there – usually for two nights, sometimes for three or four – various physiological functions such as brain waves, leg movements, breathing, heart activity or oxygen saturation of the blood are continuously measured and recorded. An expert in sleep medicine evaluates this so-called polysomnogram and interprets the results. From this data, he can assess the quality of sleep, detect an existing sleep disorder and draw conclusions about their causes. An examination in the sleep laboratory is completely painless for the patient and has no side effects.
How is a sleep laboratory structured?
The sleep laboratory consists of specially designed rooms or cubicles where the patients sleep, as well as a separate room, which houses most of the technical equipment and is used by the sleep medical staff.
When is an examination in the sleep laboratory in question?
Problems falling asleep, frequent waking at night, constant tiredness during the day, snoring with interruptions of breathing – all these are complaints that may be a reason for going to the sleep laboratory. However, the investigation is quite expensive. Therefore, it should only take place if the doctor can’t adequately classify a sleep disorder with other methods such as the detailed interview (anamnesis) of his patient or outpatient diagnostic procedure.
In 2009, the German Society for Sleep Research and Sleep Medicine defined a guideline (which is currently being revised) in which abnormalities a patient should be referred to the sleep laboratory for polysomnography:
Severe insomnia in which the condition and / or performance during the day is significantly impaired
Chronic and therapy-resistant sleep disorders that do not improve after treatment for more than half a year
Urgent suspicion of an organic sleep disorder such as sleep apnea syndrome, epilepsy or Restless Legs Syndrome
Remarkable behaviors during sleep whose cause is not clear. This includes, for example, so-called parasomnia, which includes sleepwalking and teeth grinding.
Disorders of sleep-wakefulness, for example through shift work
But also factors such as the personal suffering, such as impaired performance or fatigue, must be considered. Whether an examination in the sleep laboratory is necessary, each patient should therefore discuss in detail with the doctor – preferably with a specialist in sleep medicine.
What exactly is monitored and measured in the sleep laboratory?
A complete examination in the sleep laboratory is referred to by experts as “cardiorespiratory polysomnography”. The following measurements, body functions and activities are recorded:
Cerebral Currents (EEG): The measurement of brain waves is important to identify the different sleep stages (or depth of sleep).
Eye movements: The eye movements also provide information about the sleep stage
Heart rate and heart rhythm (ECG)
Oxygen content of the blood (pulse oximetry)
Respiratory flow to the mouth and nose
Respiratory movements of the ribcage and abdomen
Muscle tension of the chin (electromyogram or short EMG)
In order to detect behavioral problems during sleep and to include them in the analysis, patients in the sleep laboratory are always monitored with an infrared video camera and a microphone. Depending on the question, the sleep medical staff sometimes also measures values such as blood pressure, esophageal pressure or gastric reflux.
What should be considered before a sleep laboratory examination?
On the day on which a patient has an appointment in the sleep laboratory, he should refrain from drinking at the latest starting at 2pm on caffeinated drinks such as tea, coffee or cola as well as no alcohol. In addition, he is not allowed to sleep during the day because all of this can falsify the results of a polysomnography.
If the person taking medication, whether freely available or prescription, it is important to inform the attending physician, preferably in the preliminary interview. Because sometimes it is necessary to sell certain resources for the examination in the sleep laboratory in the short term. However, this must not be done arbitrarily, but only in consultation with the family doctor or the treating sleep specialist.
In addition, freshly washed hair that is not treated with hairspray, oil or gel should be taken to the sleep medicine center so that the electrodes for the EEG are better on the head.
For the mostly two nights in the sleep laboratory, the patient needs the same things in his luggage as for a normal short visit to friends or in the hotel. So, pack your bag with toothbrush, nightwear, fresh linen for the day and possibly those drugs whose intake is continued according to the doctors in the sleep laboratory.
How does the examination in the sleep laboratory work?
As a rule, the patient comes to the sleep laboratory for an examination in the early evening. The staff of the sleep medicine department receives him there, shows him his bedroom, explains the technical equipment and its function and the exact procedure of the investigation. Of course, with this introduction, the patient also has the opportunity to ask questions.
When all this is discussed, the patient prepares to go to bed as he is used to from home. Then the staff connects the measuring devices. But he is only allowed to go to bed when the nurse or the nurse asks him to do so. In bed then also the “wiring” takes place. As a rule, the following sensors and measuring devices are attached to the body of the patient:
Electrodes on the head for monitoring brain waves, eye movements and muscle activity of the chin
Electrodes attached to the ribcage used to record the electrocardiogram (ECG)
Straps with stretch sensors around the ribcage and abdomen that measure respiratory movements
A sensor on the chest strap that registers the body position
A respiratory flow sensor between mouth and nose
A sensor on forefinger or earlobe for oxygen saturation in the blood.
Two electrodes on each lower leg to detect leg muscle movement
A microphone, usually fixed in the area of the larynx, picks up snoring sounds.
When sleeping, the patient is monitored the entire time by a sleep specialist or a nurse in a separate room, with whom he can always contact via an intercom. The staff observe the measurements as well as the patient himself via an infrared video camera.
What happens after the examination?
On the morning after the examination, doctor and patient have a discharge meeting. However, the final test results are not available yet. For this the sleep specialist first has to look at and evaluate up to 800 pages with different curves, numbers and signals. That’s why it often takes a few days for the final evaluation to be there. At the latest then an appointment for a follow-up examination should be agreed. There, doctor and patient discuss both the test results and the resulting treatment options.
Is it even possible to sleep “normally” in a sleep laboratory?
The very word “laboratory” often arouses the association of a cold, technical environment with neon light and bare walls. In fact, most establishments attach great importance to a friendly and homely atmosphere in which one can feel comfortable. They have cozy “bedrooms” that should be at least twelve square meters in size according to the specifications of the German Society for Sleep Research and Sleep Medicine. They are always occupied by only one patient. Most of the technology is in a separate room.
The numerous electrodes and sensors that are attached to the head and body, the patients often initially perceive as annoying. After a short while, however, they are barely noticed because the skin has become used to it – similar to a wristwatch around the wrist. The cables bring the staff in such a way that the examinee can easily turn and move – almost like in your own bed.
Studies by sleep researchers show that about 30 percent of patients on the first night in the laboratory actually (still) sleep worse than at home. But a quarter also sleeps much better than in the home environment – because the pressure is gone, to have to sleep in order to be fit the next morning. Both effects often take place on the second night. And even if a patient in the lab does not sleep one hundred percent as in his own bedroom, that does not usually affect the validity of the examination.
What is a multiple sleep latency test and a multiple wakefulness test?
These standardized examinations are sometimes performed by sleep lab physicians to determine how alert or drowsy a patient is during the day. For this, the electrodes and gauges of the night examination remain mostly attached to the body because they are also needed for these tests. Both examinations take place in a darkened, soundproofed room with a bed or armchair.
In the Multiple Sleep Latency Test (MSLT), the patient should try to fall asleep within 20 minutes in bed. At regular intervals of two hours, a total of five times throughout the day. This time schedule also applies to the Multiple Wake Test (MWT), although there are other variants here as well. The key difference with the MSLT is that the patient, sitting comfortably in the armchair or in bed, has to make an effort to stay awake every 40 minutes.
Does the patient manage not to fall asleep at MWT? How long does it take to finish the MSLT? And which sleep stages does he go through? Such information allows the physician to assess the degree of drowsiness or sleep pressure. This provides him with important clues as to what type of sleep disorder his patient suffers from. For example, it is characteristic of narcolepsy that those affected fall immediately into REM sleep in MSLT.