Obstructrive Sleep Apnoea

OSA is caused by obstruction to the breathing tube, which occurs somewhere in the nose or throat, between the lips and voice box. It is often associated with being overweight. Other associated causes include large tonsils, large lingual tonsils, an oversized tongue, blocked nose, back-sloping jaw, long soft palate and uvula and other rarer conditions, such as throat tumours. All of the causes of OSA are also the causes of snoring (see elsewhere), its just that in OSA the problem is more severe.

Causes of OSA

• Weight gain
  Work out your body mass index (BMI), it gives you an idea as to whether you are over or under weight for a normal population. The BMI is calculated by taking your weight in kilogrammes, and dividing it by your (height in metres)2 A figure greater than 25 signifies that you are overweight. A figure over 30 signifies clinical obesity, and over 45 severe obesity. Weight gain causes OSA by a combination of factors – firstly, the patients oxygen demand is increased when carrying extra weight, so the rate of airflow if likely to be faster than in the same shape person who has normal weight, thus any mild blockage to the airway causes a relatively greater problem to air flow. Following on from this, those with weight gain have restricted breathing, due to the mass effect of abdominal fat on diaphragmatic movement, and also chest movement. Finally, weight around the neck causes squashing of the flexible part of the airway, mainly that above the voice box. This is all exacerbated by loss of muscle tone at night during REM sleep – which causes any relative airway compression to be worse. Thus weight related OSA is episodic throughout the night.

• Large tonsils
  The tonsils or palatine tonsils as they are correctly called, due to their site between the palatal folds of the throat, can cause obstruction to the airway by being sucked into the throat when breathing in deeply at night. This is again made worse by muscle relaxation during REM sleep – muscle tone keeps big tonsils from falling into the throat during the day. This falling in, or proptosis, of the tonsils, can completely obstruct breathing, with instant apnoea. This form of OSA is prevalent at all ages, but is commoner in children, when it may be related to other catarrhal symptoms such as glue ear and nose blockage.

• Lingual tonsils
  As their name suggests, these structures are the same tissue as palatine tonsil, but sit at the back of the tongue (hence lingual). The back of the tongue sits in the “retro-lingual space”, one of the narrowest parts of the airway, particularly when muscle relaxation occurs in REM sleep. If the lingual tonsils are enlarged, which can happen particularly after standard, palatine tonsillectomy, OSA can occur, again, with other catarrhal symptoms such as throat clearing, throat lump sensation.

• Oversized tongue
  Generally this is a relative condition, relative to the size of the mouth. Therefore a big mouth with a big tongue would have a relatively normal ratio, whereas a big tongue in a small mouth would cause problems – again, by obstructing the retrolingual space during REM sleep. Downs syndrome patients often suffer from a relatively large tongue.

• Blocked Nose
  A blocked nose can be part of the cause of OSA because a patent nose passage helps to improve the normal movement of air into the lungs, preventing mouth breathing, which is more prone to obstruction than nose breathing. Nose blockage can be due to a number of underlying conditions, most commonly a bent nasal septum, large inferior turbinates, nose polyps, and chronic sinusitis. Often there is an underlying allergic condition as well. In children, large adenoids may be present which can exacerbate the apnoea caused by large tonsils.

• Back sloping jaw
  A backward sloping jaw, or retrograde mandible, causes OSA again by allowing the tongue to move backwards, occluding the retrolingual space, mainly caused by loss of muscle tone in REM sleep. In conditions such as Pierre-Robin syndrome, this is particularly severe.

• Long soft palate / Uvula
  A thickened and elongated soft palate and uvula (the hanging down thing at the back of the throat) causes OSA by blocking the two main air passages from the mouth and nose, into the throat, namely the retrolingual and retropalatal airways. Again this is made worse by muscle relaxation during REM sleep.

  Retrolingual and retropalatal (small arrow) spaces – see how a thick and long soft palate can obstruct these?

• Throat tumours
  Benign or malignant, they can present clinically with OSA before their presence becomes obvious, These tumour grow in the larynx (voice box) and pharynx (throat), both of which are part of the upper airway, and where obstruction can lead to OSA. In these situations, the obstruction is progressive, and acute difficulty in breathing can eventually occur at night, and even during the day. This condition, known as stridor, is a medical emergency.

Treatment
The treatment of Obstructive Sleep Apnoea depends upon its severity, which can be diagnosed by means of simple sleep tests which measure flow of air and oxygen saturation. At the London Laser Clinic, we use the Embletta multi-channel system, which is used on an “at home” basis. Patients are brought into the Hospital, attached to the relative monitoring, and allowed to go home. When they are about to go to sleep, they plug themselves into a “black box” which records all of their sleep data. This can then be downloaded and emailed to The Royal Brompton Hospital, with whom we work closely, and analysed by one of the top sleep experts.

Severe OSA warrants referral to a chest specialist from The Brompton with an interest in ventilation assistance – called CPAP.

Mild to moderate OSA can often be controlled with a variety of local interventions, such as a mandibular advancement splint, or correction of the relevant abnormality, e.g. with nose unblocking surgery, laser tonsillectomy, laser palatoplasty or somnoplasty. Obviously, any underlying throat tumour needs urgent diagnosis and treatment, although these are rare causes of OSA. For more data on throat tumours etc, please go www.londonheadandneck.com.

This picture shows obstruction to the flow of air due to collapse of the palate and tongue base.

Large tonsils and lingual tonsils, or a blocked nose, all make this worse.

The London Laser Clinic has more background information, and a number of treatment solutions for sleep apnoea; click here to visit the LLC Sleep Apnoea pages.