Introduction

Sleep Apnoea is a condition in which breathing stops momentarily during sleep. There are two types of Sleep Apnoea, Obstructive Sleep Apnoea (OSA) and Cental Sleep Apnoea (CSA).

Obstructive Sleep Apnoea.

In normal snoring, the muscles which hold the pharynx (the part of the throat at the back of the of the tongue) open relax during sleep, partially choking the airway and causing the pharyngeal walls to vibrate, giving the sound of snoring.

Obstructive Sleep Apnoea (OSA) occurs when the pharyngeal narrowing results in a complete block of the airway during sleep.

Causes of OSA.

Obstructive Sleep Apnoea can be caused or worsened by several factors including:

• Obesity or Weight Gain which can narrow the upper airways
• Alcohol - Alcohol causes greater relaxation of muscles during sleep, which can result in an abnormally collapsible upper airway. It also decreases arousal responses.
• Nose or Throat Problems like abnormal lumps in the airways such as nasal polyps, enlarged tonsils or adenoid, thyroid gland swellings or a large tongue. Hayfever and smoking can also lead to narrowed nose passages, thus aggravating the condition.
  Variations in the shape of the jaw, throat, face or nose can result in some people having narrower upper airways. This is sometimes found to run in families, so if you are a snorer or have OSA, you may have relatives with the same problem.
• Sleeping Tablets can cause increased throat muscle relaxation, narrowing the upper airway, this is also the case with Anaesthetic drugs used during surgery.
• Men are more likely to snore or have OSA than women of reproductive age. This is thought to be due to sex hormone differences and their effect on muscle strength and fat distribution. It could also be due to the higher average alcohol consumption of men.

Effects of Obstructive Sleep Apnoea.

As the body's oxygen stores can last only a few minutes, when breathing in of fresh air is reduced or stopped for more than a few seconds, the changes in oxygen and carbon dioxide levels stimulate the brain to cause arousal from sleep and to increase respiration.

When the brain wakes up, it allows a return of strength to the pharyngeal muscles, the airway opens and breathing returns to normal. Sleep returns, the airways narrow again and the pattern repeats itself. In severe cases, this cycle can be repeated every 1-2 minutes. When the apnoeas and arousals occur frequently, the night's sleep can become highly disrupted and Excessive Daytime Sleepiness occurs the next day. As arousal rarely results in full wakefulness, few or none of the events can be remembered the next day.

Symptoms

Syptoms of Obstructive Sleep Apnoea may include:

• Snoring
• Daytime sleepiness (with increased risk of car and work accidents)
• Apnoeas (stopping breathing while sleeping)
• Morning headaches
• Poor memory and fuzziness in thinking
• Depression
• Restless sleep
• Bedwetting or passing urine at night
• Breathlessness either during the night or the day
• Reduced sexual activity
• Night time heartburn.

Diagnosis.

If you suspect that you may have OSA, consult your GP. Your GP may then may refer you to a sleep specialist who may require a sleep study to be done in a sleep laboratory.

Treatment.

Treatment can vary from person to person and according to the severity of the OSA. For mild OSA treatment may include:

• losing weight
• reducing alcohol consumption
• reducing nasal abstruction (nasal sprays or occasionally nasal surgery)
• ceasing or limiting on sleeping tablets or sedatives
• improving lung function by focusing on the any causes of reduced lung condition

For moderate or severe OSA treatment may involve:

• a mandibular splint (oral appliance to improve the position of the jaw during sleep)
• a nasal CPAP (Constant Positive Airways Pressure)
• surgery on the nose or throat

Central Sleep Apnoea (CSA)

In the less common Central Sleep Apnoea, hypoventilation (low respiration) is caused by reasons other than an obstructed upper airway.

Causes of Central Sleep Apnoea.

CSA can result from either:

• Weakened lung and/or chest muscles after certain diseases.
• Loss of ventilatory drive, due to conditions affectingthe brain stem including enchepalitis, stroke or brain trauma, or delayed responses to blood gas level changes like seen in heart failure.

Symptoms of CSA.

As in OSA, Daytime Sleepiness and spouse reported apnoeas are common as well as symptoms resulting from sleep disturbance and low oxygen levels like morning headaches, loss of memory, poor concentration, bedwetting or passing urine at night, depression and breathlessness. Unlike OSA however, there is usually no snoring present. Insomnia or difficulty in sleeping is another common problem.

Diagnosis.

Diagnosis is as per Obstructive Sleep Apnoea.

Treatment.

Central Sleep Apnoea may be treated in the various ways:

• Medications - sometimes respiratory stimulant medication can be of help. these should be taken on the advise of a doctor well trained in sleep and breathing disorders.
• Nasal CPAP may sometimes be tried.
• Home Ventilation (like a CPAP, but with timed bursts of air instead of constant pressure).
• Oxygen to breathe at night.
• A diaphragm Pacemaker (like a heart pacemaker, but for the diaphragm) has been used in some cases.

Further Reading

• Oral Appliance Therapy for Snoring and Obstructive Sleep Apnoea
• Heart Failure & Sleep Apnoea

References

1. Naughton, M. & Pierce R. Snoring, Sleep Apnoea and Other Sleep Related Problems. Published by the Victorian Tuburculosis and Lung Association: 1996.
2. Naughton, M. & Pierce R. Sleep Related Breathing Disorders. NODSS Guide to Sleep Disorders: 1999.