Polysomnography, also known as a sleep study, is a test that can diagnose sleep-disordered breathing and related health problems. Although it is the most commonly used method for diagnosing obstructive sleep apnoea (OBS), it is not without its drawbacks. What should you know about polysomnography?
What is polysomnography?
Polysomnography is a complex study that records the body’s processes during sleep and is an important diagnostic tool in its disorders.
During the polysomnographic study, parameters such as:
- airflow through the nose,
- breathing air temperature,
- respiratory effort (by recording chest and abdominal movements),
- incidence of snoring,
- body position,
- arterial blood oxygen saturation (using a pulse oximeter),
- brain activity (electroencephalography, EEG),
- heart activity (electrocardiography, ECG)
- muscle and nerve function (electromyography, EMG),
- eye movements (electrooculogram, EOG).
These parameters allow to objectively determine whether a patient is asleep and in which phase of sleep he/she is, as well as to detect awakenings typical for obstructive apnoea, lasting from a few to several seconds, of which the patient is not aware. On the basis of the obtained results it is possible to analyse the physiological reaction of the organism to apnoeas.
What are the indications for polysomnography?
Polysomnography is indicated for people who snore and are suspected of having obstructive sleep apnea. Sleep study is also performed in people who have problems with getting up in the morning, struggle with insomnia, have restless sleep or show excessive muscle activity during sleep (frequent changes of positions, restless legs syndrome). Indications also include morning headaches, excessive daytime sleepiness, chronic fatigue. In patients diagnosed with OBS and other sleep disorders, polysomnographic examination is performed periodically to assess the effectiveness of treatment.
Polysomnographic study is particularly indicated in professional drivers and machine operators. The exclusion of OBS in these groups is important because sleep-disordered breathing can lead to excessive daytime sleepiness, difficulty in focusing attention and slowed reaction time. Apnoea and the associated lack of healthy, restorative sleep can cause traffic collisions and accidents at work.
Preparation for polysomnography
Polysomnography is performed in hospital, in a sleep study laboratory. It requires one-day hospitalisation and appropriate preparation. On the day of the study you should not drink alcohol or coffee, and you should not use sleeping pills or sedatives, which can interfere with the study results. Tell your doctor about any medication you are taking, especially psychotropic, sedative and antidepressants.
Pack pyjamas (preferably fastened at the front to make it easier to attach the pads) and toiletries (including hair shampoo and shower gel) for the hospital. If you need to, you can take your own pillow or even a duvet.
Course of polysomnography
Polysomnography usually takes place at night – during the hours when you usually sleep. However, you will need to arrive at the hospital a few hours earlier to prepare for the study. Before you go to bed, you will be interviewed by a doctor and have to fill in questionnaires and documents. The staff will then prepare you for the examination by placing a set of sensors necessary for polysomnography in different parts of your body.
Electrodes for EEG are placed in different parts of the head, electrodes for EOG are placed at the outer angle of the left eye and at the outer angle of the right eye, electrodes for EMG are placed on the chin muscle. A temperature and airflow sensor is placed in the mouth area and a microphone is glued there. Electrodes for ECG are attached to the chest. A pulse oximeter is placed on the finger of the hand. A limb movement sensor is placed on the ankle. In addition, belts measuring movement are attached to the abdomen and chest.
There is a camera in the corner of the room and there are staff in the next room, watching over the study. You should go to bed at a time that is normal for you. After a good night’s sleep you can go home straight away. The course of polysomnography may vary slightly depending on the health facility performing the study and the purpose of the study.
An alternative to polysomnography
Polysomnography is a valuable study in sleep diagnosis, but it is not without its drawbacks. Not only does it involve high costs associated with the use of specialised equipment and the presence of staff for several hours of examination, but it is also uncomfortable for the patient. Although the electrodes are placed in such a way as to be as uncomfortable as possible, most patients experience discomfort during polysomnography and the results may be unreliable. The most common problems are difficulty falling asleep and falling into a supine position, which aggravates apnoea symptoms and causes frequent awakenings. The short duration of this study is also a disadvantage. One-night parameters are not as objective as several days of sleep observation. Another disadvantage is the place of examination itself – the hospital is not the patient’s home, which is a great discomfort for many people.
An alternative to polysomnography are modern diagnostic solutions which can be used at home, allowing measurements to be taken over a longer period of time. Observation of the course of sleep over several days allows for averaging the result and making an objective diagnosis. Similar procedures have been used in the case of other diseases, such as hypertension – the basis for making a diagnosis and introducing pharmacotherapy is a number of measurements taken at home, not a single visit to a doctor’s surgery. An example of such a solution in apnoea diagnostics is the Clebre sensor together with an intuitive application. Simply attach it to your neck, at tracheal level, switch it on and go to sleep as usual. The sensor records and analyses your every breath. When you wake up, you can immediately see your results in the app and share them with your doctor. The device records and analyses every inhale and exhale, detects snoring episodes, counts shallow breaths and estimates the number of apneas during sleep. Thanks to its advanced technology, it enables the assessment of most parameters that are tested during polysomnography, including body position and motor activity.