Obstructive sleep apnoea: Step by step to diagnosis

If obstructive sleep apnoea is suspected, various examinations are carried out step by step to confirm the diagnosis. The most reliable method of diagnosis is polysomnography in the sleep laboratory. First, however, less elaborate examinations are carried out to confirm or refute the suspicion.

The first point of contact is your GP, who will first ask you in detail (anamnesis). He may also involve your partner. Describe your observations to the doctor in detail, as these are very important for the diagnosis. Your doctor will also address the topic of sexuality, because sexual sensation disorders or erectile dysfunction can be associated with obstructive sleep apnoea. Standardised questionnaires specifically designed for the diagnosis of chronic sleep apnoea may be used in the anamnesis.

The interview is complemented by a comprehensive physical examination, which includes weight checks and blood pressure measurement. Obesity can not only be a symptom, but is also an important risk factor for developing OSA. High blood pressure is a common secondary disease that is largely responsible for the increased risk of heart attacks and strokes. Corresponding indications during questioning and examination lead to the suspected diagnosis of ‘obstructive sleep apnoea syndrome’. All the sequelae and symptoms together are called obstructive sleep apnoea syndrome (OSAS).

Polygraphy is, so to speak, a mini version of the examination in the sleep laboratory and is therefore also called a ‘small sleep laboratory’. It is a question of confirming or rejecting the suspected diagnosis. Therefore, it must be examined during sleep whether breathing stops actually occur and how the body reacts to them: Does the oxygen content of the blood drop as a result of the breathing stops? Is the blood pressure rising? Does the heart start to stumble?

As a rule, a polygraphy is first on the programme. This ‘screening procedure’ (OSAS screening) is less time-consuming than an examination in the sleep laboratory, but already provides important indications as to whether there is something to the suspected diagnosis.

You perform the polygraphy yourself – in the comfort and relaxation of your own home. Don’t worry: you can’t go wrong with it. Your doctor will explain everything to you in detail. Afterwards, you take the polygraph home with you, which can be easily transported in a handy case. Then, before you go to bed at night, all you have to do is attach some probes. The device does the rest all by itself. If the GP has the appropriate qualification, this diagnostic step also takes place under his supervision. Otherwise, your GP will refer you to a specialist – a sleep doctor.

During sleep, the polygraph device registers the respiratory flow and any pauses in breathing, the respiratory movements of the chest and abdomen, the oxygen content of the blood, the heartbeat, snoring sounds and the sleeping position. Based on the recordings, the doctor can later see if ‘unusual things’ have happened during sleep. If the polygraphy reveals indications of obstructive sleep apnoea, a final examination is carried out in the sleep laboratory. Your doctor will discuss this with you in detail and issue a referral to a sleep medicine centre.²

The examination in the sleep laboratory, during which a large number of measurements are taken, is called polysomnography.³ This conclusively confirms the suspected diagnosis of obstructive sleep apnoea. In the sleep laboratory, similar examinations are carried out as in polygraphy, but the data obtained are even much more precise and comprehensive. The sleep profile obtained includes a large number of measured variables, which together allow a reliable statement as to whether obstructive sleep apnoea is present or not. At the same time, polysomnography can be used to determine the severity of the disease. Among other things, the apnoea-hypopnoea index (AHI), which indicates how many pauses in breathing occur in one hour, is important.

The examination is usually carried out in a sleep medicine centre. This means you stay here for one night or possibly several nights. You will be accommodated in a patient room – a single room – which is usually furnished more like a hotel room than a hospital room. You should feel comfortable so that you can sleep as relaxed as possible.

You will be wired before going to bed: Electrodes are attached to the chest and arms or legs to record the electrical heart signals (electrocardiogram, ECG). Using the long-term ECG, the doctor can then see how your heart behaves during sleep: Does it beat evenly or does it perhaps stumble when breathing stops? Blood pressure is also monitored continuously. And the brain waves during sleep are also registered (encephalogram). For this purpose, electrodes are applied: four to six on the head, and five on the face.

In addition, the so-called sleep architecture is also examined. The REM sleep (Rapid Eye Movement) has a special significance. During REM sleep, the eyes move back and forth at lightning speed. Now we dream and process what we have experienced during the day. REM phases normally increase during the night and are important for a healthy sleep architecture. That’s why the sleep lab also logs eye movements, which are clearly visible under the closed eyelids. If the sleep architecture is disturbed, sleep is not properly restful, which can lead to typical OSA symptoms such as daytime sleepiness and lack of concentration.

In addition, you will be filmed with a video camera while you sleep – of course only if you have expressly consented to this. The camera records, among other things, whether there are any waking reactions with body movement during sleep, which is a sign of breathing cessation. In order to detect respiratory disorders, the air flow at the mouth and nose is also registered with special sensors.

The various examinations that are carried out as part of polysomnography are completely painless and the sleeper does not notice anything at all. The only thing that might be a little annoying at first is the cabling. I’m sure you’ve asked yourself: Is it even possible to sleep at all with all the electrodes and wires? Yes, you can. On the part of the sleep laboratory team, everything is done to make the examination situation as comfortable as possible. The quite fine cables are bundled and laid in such a way that they interfere as little as possible with freedom of movement and sleep.

Nevertheless, you may not sleep as well the first night as you would at home. Maybe you find it difficult to fall asleep or you wake up more often in between. Besides, you don't sleep the same way every night anyway. For example, with obstructive sleep apnoea there are ‘good nights’ with few breathing pauses and ‘worse nights’ when the pauses increase. The first night in the sleep lab often tends to be one of the good nights (first night effect). That is: If one were to judge only this first night, the disease would appear more harmless than it really is. Therefore, if it is suspected that you have obstructive sleep apnoea, you will usually be observed for several nights in the sleep laboratory.⁴