The science of snoring

news: The science of snoring

This article was written in co-operation with Mike Dilkes MS FRCS and Santdeep Paun FRCS (ORL-HNS) from the prestigious St Bartholomew’s Hospital in London. Mr Dilkes holds monthly clinics in the Family Medical Centre in Vale do Lobo. Dr THOMAS KAISER

Snoring has long been the source of mirth and ridicule. Famous literary figures across the ages have remarked upon it, from both a jocular and scornful angle. The classical picture is the Pickwickian old soak – obese and drunk, lying on his back, asleep, producing a violent vibrating sound, levels of which have reached over 90 decibels (shouting levels).

What has rarely been remarked upon is the fact that he also completely stops snoring and breathing, intermittently throughout the night. There is a medical term for this – apnoea, which means ‘no breathing’. This is much more serious than simple snoring. It has been postulated (although never proven) that persistent and severe apnoea can cause hypertension, particularly in the lung blood vessels, and possible heart failure (cor pulmonare).

What is without doubt and proven when measuring the brain waves is that snoring affects the level and quality of sleep. Patients often suffer ‘sleep arousal’, when they wake up recurrently during sleep, and they may suffer other sleep syndromes secondary to this, such as vivid dreams, sleep paralysis and sleep walking. The consequence of this is that patients may wake up feeling abnormally tired and have a raised sleepiness level during the day. This can be measured in a number of different ways – the Epworth sleepiness score is the usual way of measuring this.

So what makes us snore?

After all, the shape and problem of our throat is there all day long, yet we only snore at night. Essentially, it is all down to physics and airflow. Classical snoring is caused by tissue flapping in the back of the throat (snoring is like a ‘throat clap’). It flaps because airflow in the throat becomes energetic in certain situations (turbulence). Flow becomes energetic because the speed of airflow increases, causing increased disturbance from the side walls of the throat, changing predominantly smooth laminar flow into energetic turbulent flow.

The reason the speed of flow increases is mainly down to posture and depth of sleep. If we sleep on our back, the back of the tongue will partially drop into the throat, slightly obstructing the airway. This causes oxygen levels to drop slightly, as less air is moved in and out of the lungs. The brain will realise this and increase the pressure changes in the lungs, which forces air in and out at a higher speed. That is why snoring often improves when we sleep on our side – the tongue flops forward and opens the airway.

Depth of sleep influences snoring because, when we drop into a deep sleep, the body relaxes almost completely and muscles lose their tone. In the throat, the muscles of the swallowing tube (pharynx) keep the airway open when we are awake, by being slightly contracted all the time (muscle tone). When in deep sleep this muscle relaxes, sags and causes the airway to decrease, thus increasing respiratory effort and causing flow to speed up, as with the tongue.

If you are overweight, adipose tissue around the neck will cause an increase in the sagging by a direct pressure effect, so worsening the problem. If you have drunk too much alcohol, your sleep pattern will be disturbed, the consequence being that you are in a deep sleep for longer and, therefore, snore for longer, sometimes for most of the night. The worse this whole situation gets, the more the airway blocks, until it begins to completely obstruct. This is when the oxygen levels start to fall significantly and the brain becomes aware, waking the snorer up, thus removing him/her from a deep sleep and so muscle tone returns and the problem settles – for a while… This is how sleep apnoea starts. So, we must pity the poor Pickwickian man, who never stood a chance.

How do we treat snoring?

Clearly, there are a number of causative factors in snoring. The approach must be multidisciplinary, with those involved having a particular interest in this area. The first port of call is usually with an ear, nose and throat (ENT) surgeon, with a specialist interest in snoring and sleep apnoea, since the level of the problem is always in the throat-nose area. The surgeon will assess all the factors mentioned and look for problematic areas. The body mass index (measure of obesity) and sleepiness score is calculated.

Particular problem areas for obstruction are the nose – whether due to polyps or a deviated septum – and the throat, where there may be large tonsils or a long palate and uvula. The patient will be thoroughly examined for problems in these areas and examination should include a direct look into the lower throat with a flexible endoscope. If there is clear ENT pathology, such as a blocked nose, or large tonsils, or a very elongated soft palate/uvula, these can be treated.

Otherwise, the next step of referral will be to a chest physician to arrange a test for sleep apnoea if the sleepiness score is greater than 12 (an overnight sleep study), a dietician for weight loss if the BMI is over 30, and an orthodontist to arrange a splint for the teeth to pull the tongue forward at night, preventing some of the airway collapse that is part of the problem. The patient is then reviewed a few months after these tests/treatments have been performed.

If the BMI has dropped below 30, the sleep study did not show serious apnoea and the splint was only partially effective, the next step of treatment is to treat the source of the sound, rather than the cause of the turbulence. This usually means the soft palate and uvula, which can be partially lasered away under local anaesthetic. If serious apnoea is found, referral to a dietician and orthodontist remains a requirement and extra treatment, using overnight ventilation via a facemask (CPAP), may be required. This prevents airway collapse by blowing air into the throat, splinting it open, albeit at fairly low pressures.

A reasonable reduction in snoring volume of around 70-80 per cent is usually achievable. Clearly, we have to make some sound at night to breathe, but a reduction in sound to levels that don’t disturb the sleeping partner is the desired outcome.