Snoring and Obstructive Sleep Apnoea Syndrome
This page is a short introduction to the broad themes associated with snoring and obstructive sleep apnoea syndrome (OSAS). Predominantly, it is aimed at FY1 doctors graduating from Swansea University Medical School. In depth treatments of the topic can be found elsewhere and we would direct you specifically to the CKS for a deeper review of OSAS.
Snoring is an abnormal noise associated with a partial obstruction of the upper airway during sleep. Note that stridor is caused by obstructions in the larynx and trachea.
Snoring is a symptom and it is associated with a continuum of sleep-related breathing disorders. It may be intermittent and mild to continuous and heavy. In some patients it is associated with upper airways resistance syndrome (UARS) or even obstructive sleep apnoea syndrome. These terms are explained below.
A common view of snoring is that it is a matter for joking or is just annoying. However, for the sufferer and those around them it is anything but. Snoring can put a significant strain on a relationship and is socially disruptive. It may also be a symptom of a disease that can cause severe cardiovascular disease and its impact on sleep can lead to death through accidents.
The physics behind a snore
Elsewhere, we have described the generation of stridor in a narrowed larynx. Snoring arises through the same physical laws: air flowing through a narrowing will increase in velocity and become turbulent. Remember that turbulent, non-laminar airflow becomes more likely as air velocity increases.
The upper airways are soft and mobile and the turbulence cause them to vibrate. Snoring tends to occur more during inspiration because of the negative pressures generated in respiration to draw air in. This causes the narrow airway to become narrower still. Expiration raises the pressure in the airway and widens it making noise less likely (but not impossible). Continuous positive airway pressure does the same thing – see treatment of OSAS below.
When Charles Dickens created the retired, successful Mr. Pickwick he described the classic snorer: ageing, male, and overweight. But it is Joe, "the fat boy" from the same story that has symptoms of OSAS. He ate a great deal, continually fell asleep, and snored at the dinner table. OSAS was originally called "Pickwickian syndrome" after Joe.
Snoring becomes more common as you get older because the airways slowly lose their muscular support. This makes them floppier and more likely to vibrate.
Men snore more than women. This may have something to do with the differing size of the airway but is also related to female hormones; women snore more at menopause.
Body Mass Index
Being overweight is a significant risk factor for snoring in both sexes. Fat deposits within the neck narrow the airway making it more prone to vibrate. Note that thin people can suffer too but for other reasons
Smoking and alcohol consumption both increase the risk of snoring.
Medications such as sleeping tablets and some sedating antihistamines can increase the risk of snoring.
Upper airway disease
Nasal disease or trauma increase the risk of snoring because a blocked nose requires a higher inspiratory effort. This means a greater negative pressure in the airway and greater collapse of soft tissues.
Upper airway anatomy
Even thin people can snore if their anatomy causes narrowing of the upper airway. Children have naturally large tonsils and adenoids causing anything from snoring to full blown OSAS. Enlarged lingual tonsils, retrognathia, long epiglottides or uvulae can all cause vibration in the airway.
What can be done about snoring?
Since the more easily modified risks are weight, smoking, alcohol consumption, sedatives, and nasal disease, it is not surprising that, for the majority of sufferers, these will be the first things that the doctor will discuss.
Weight reduction in the overweight or obese patient will usually ease the symptom of snoring and it will have tremendous impact on their other health too. Stopping smoking will also have a beneficial effect beyond the snoring problem.
Reduction in alcohol consumption will be needed to lose weight, especially in those people that drink to excess.
General Practitioners will manage any mucosal disease in the nose with nasal douching with or without nasal steroids. They will review medications to seek non-sedating alternatives.
Should these steps fail or not be appropriate then a referral for consideration of surgery will be considered. Surgery for snoring is rarely required if the patient is able to modify their lifestyle, lose weight or change the medications that may predispose them to snoring. However, some patients will come to surgery anyway.
The ENT Department will organise a sleep study and, if there is no suggestion of UARS/OSAS, may consider surgery targeted at the narrowing in the airway. This might mean a nasal operation or surgery to the oropharynx to reduce the soft palate and uvula, and remove the tonsils. Occasionally, surgery to reduce the lingual tonsil is also needed.
One such operation is shown below. In this procedure the patient has been found to have snoring caused by vibrations in the palate and lateral oropharyngeal wall. The tonsils and the free edge of the soft palate have been removed.
If there is UARS or OSAS then CPAP will be organised as a first management along with the lifestyle elements listed above.
UARS and OSAS.
If simple snoring is a symptom caused by slight airway narrowing at one end of a spectrum of disease, UARS is in the middle, and OSAS is very much at the other end. OSAS is the condition that, if left untreated, leads to severe cardiovascular disease and death through myocardial infarction or through accidents caused by sleepiness. Stroke, hypertension, metabolic syndrome and neurocognitive dysfunction are also possible. UARS causes similar problems to OSAS but there aren’t any complete obstructions during breathing. This is a spectrum of diseases.
For all practical purposes, consider UARS as a milder form of OSAS that requires the same management. It, too, is associated with significant morbidity and mortality.
What are the symptoms?
In OSAS, the airway is narrow causing snoring but, at intervals, it completely collapses for short periods. These are the obstructive sleep apnoeas. Once obstructed a number of things happen: PaO2 in the blood starts to fall and PaCO2 in the blood stream start to rise. The rising PaCO2 stimulates arterial chemoreceptors in the carotid body resulting in an increase in respiratory drive. This initially worsens the obstruction but then overcomes it, leading to a loud gasp, arousal from sleep to a greater or lesser degree, and a return to snoring.
Repeated cycles of this through the night significantly reduce sleep quality causing the patient to awaken unrefreshed and experience daytime somnolence.
Sleep disruption and periods of hypoxia during the night lead to longer-term effects too. Cognitive function is impaired and memory and concentration are particularly affected. Symptoms of depression, anxiety, impairment of social life, and decreased effectiveness at work are all consequences of poor sleep in OSAS.
Diabetes, hypertension, coronary artery disease and stroke are all more likely. Then there is death by accidents. These are more common in patients that are sleepy and inattentive. This is one reason that we have rumble-strips on the side of motorway lanes.
Breath holding and gasping
Daytime sleepiness (hypersomnolence)
Neurocognitive - poor concentration, memory, problem solving
Psychological - depression and anxiety
Cardiovascular - right sided hypertension / cor pulmonary, systemic hypertension, dysrhythmia, heart failure, MI, stroke, death
Metabolic - metabolic syndrome, diabetes, increased weight
How is it investigated?
Details of investigation are beyond the scope of our course. However, you should know that the gold-standard investigation is a full sleep study or polysomnogram. This measures a number of physiological parameters simultaneously during sleep including, oxygenation, heart rate, respiratory rate and effort, the noise of snoring amongst others. The sleep study will generate, amongst other things, an apnoea/hypopnea index (AHI).
The AHI gives a broad indication of the severity of the UARS/OSAS. It is a measure of the number of apnoeas and hypopnea per hour of sleep during the test. Apnoeas and hypopneas have definitions that are beyond the scope of the FY1 competences covered in our course in Swansea.
Ranges of AHI and severity of disease.
Mild disease: AHI <15
Moderate disease: AHI 15-29
Severe disease: AHI >30
What is the treatment?
As for snoring, the first steps will be to address the physical causes of the disease. This will involve losing weight, stopping alcohol and smoking. Should this be ineffective by itself then nasal continuous positive airway pressure (CPAP) will be tried next. This is done via a facemask attached to a pump that gently increases the airway pressure and decreases the tendency of the airway to collapse.
CPAP is successful for a range of symptoms. Better quality sleep means better cognition and memory, greater attentiveness, better energy (and a chance of improving activity levels and weight loss), and a reduction in cardiovascular strain and hence decreased hypertension, risk of arrhythmia, and the other consequences of chronic repeated nocturnal hypoxia.
The patient and their CPAP device are monitored to review effectiveness and compliance of usage.