Sleep Apnoea

Sleep apnoea affects around one in 100 people. Overweight men between the ages of 30 and 65 are most commonly affected, but it may also occur in children with enlarged tonsils or adenoids. About 2-4 per cent of the middle-aged population suffers the consequences of recurrent upper airway obstruction during sleeps in the past decades.

The pause in breathing or period of very restricted breathing, is usually defined as about 10 seconds, although it varies from person to person. The frequency of apnoea or hypopnoea is used to assess the severity of this condition. The number of times that the apnoea occurs in an hour is called the apnoea/hypopnoea index (AHI) or the respiratory disturbance index (RDI). An AHI of between 5 and 14 in an hour is mild sleep apnoea. Between 15 and 30 is moderate. More than 30 in an hour is severe - that means at least one every two minutes.

Classification

Sleep apnoea may be classifieds as -

The incidence of OSA is higher than that of CSA in the general population, and OSA occurs 2 to 3 times more often in older adults. It is also twice as common in men as in women.

During wakefulness upper airway dilating muscles -including palatoglossus and genitoglossus active during each inspiration to preserve airway patency. During sleep muscle tone generally declines including that in the upper airway dilating muscle and their ability to maintain patency falls. In most people sufficient tone persists to result in uncompromised breathing during sleep. OSA occurs when the muscles in the back of the throat, which support the soft palate, uvula, and tongue, relax to the point of obstructing the airway. This obstruction prevents airflow to the lungs, which, in turn, creates temporary periods of hypoxia. The brain eventually senses the decrease in oxygen and briefly rouses a person from sleep in an attempt to open the airway. CSA results from the brain's failure to transmit signals to the breathing muscles of the throat. As the level of carbon dioxide progressively increases and the level of oxygen decreases, a trigger in the brain will ultimately arouse a person from sleep abruptly.

Causes

Sleep apnoea is caused by many actors those make the throat narrow more than usual during sleep.

Men and older people are more likely to experience sleep apnoea.

Symptoms

People affected by sleep apnoea are often unaware of that they have the condition. However, as their sleep is disrupted they usually begin to experience symptoms during the day and a partner may witness an apnoea or point out other symptoms that occur at night.

Symptoms include

Cardiovascular Effects

The cardiovascular consequences of sleep apnoea include arterial disease (eg, coronary heart disease), cardiac arrhythmias (eg, atrial fibrillation), pulmonary hypertension, and sudden death.

The repetitive and transient periods of decreased blood oxygen levels that occur during sleep apnoea are believed to increase sympathetic nervous activity (SNA), which, in turn, contributes to hypertension and left ventricular (LV) hypertrophy. Concomitant conditions such as obesity, plus preexisting hypertension and LV hypertrophy, in addition to sleep apnoea ultimately lead to both diastolic and systolic LV dysfunction. There is a strong association between obesity and OSA.

Prevalence in Heart Failure Patients

Although the prevalence of OSA is generally higher than that of CSA, the latter is more common in heart failure patients. At the American Heart Association (AHA) 2004 annual scientific session, Shahrokh Javaheri, MD (Cincinnati, Ohio), discussed the prevalence of sleep apnea in stable heart failure patients with systolic dysfunction. According to a number of studies, approximately 45 per cent to 82 per cent of these patients experience >/= 15 obstructive apnoea and hypopnoea episodes per hour of sleep (apnoea-hypopnoea index [AHI]). In addition, the reported prevalences of CSA and OSA have ranged from 29 per cent to 62 per cent and 5 per cent to 32 per cent respectively. Dr. Javaheri noted that the wide variance in the reported prevalence of sleep-related breathing disorders in patients with stable HF and systolic dysfunction is likely due to inconsistent definitions of sleep apnoea as applied by different institutions.

CSA is believed to be a consequence of heart failure, and can occur at any stage of the disease. Published in 2003, Paola A. Lanfranchi, MD, Fondazione Salvatore Maugeri, Italian Oncologic Institutes of Care and Research (Veruno, Italy), and colleagues studied 47 patients with LV dysfunction (ejection fraction [EF] </= 40 per cent) without overt HF. They found that these patients had a higher incidence of CSA than OSA; 55 per cent of patients had CSA (AHI >/= 15/hr), and severe CSA (AHI >/= 30/hr) was observed in 17 per cent of patients. By contrast, only 11 per cent of patients had OSA. The researchers noted that CSA was more prevalent in ischemic vs nonischemic cardiomyopathy patients. Furthermore, CSA patients had a higher occurrence of ventricular arrhythmias. The authors concluded that their findings suggest CSA may increase cardiovascular risk by impairing cardiac autonomic control, thus increasing the risk of cardiac arrhythmias.

The repetitive hypoxia of sleep apnoea, particularly CSA, can contribute to increased arterial afterload (both sleeping and awake), which can also worsen diastolic and systolic myocardial dysfunction.

Diagnosis

In addition to checking with the person affected, to find out what symptoms they have, the doctor may also ask the person's partner to describe the symptoms they have seen and heard. Sometimes the person themselves may be unaware that they have a problem but their partner may have actually seen them having an episode of apnoea.

The doctor will also assess the type of sleepiness a person is experiencing, to work out whether sleep apnoea is a possible diagnosis. In sleep apnoea, daytime sleepiness occurs when a person does not want to sleep, for example when driving or when working.

The Epworth Sleepiness Scale (ESS) is the way of measuring how likely a person is to fall asleep, in a particular situation during the daytime. It involves the patient filling out a questionnaire and helps the doctor to find out how severe the condition is. A number of tests can be carried out to help diagnose sleep apnoea.

A polysomnogram :

This involves an overnight stay in a sleep laboratory and records the apnoea/hypopnoea index, how much and how loudly a person is snoring and their sleeping position.

Visual Observation of Sleep

This enables doctors to check whether the patient is having breathing difficulties, if their breath is pausing for long periods and they are waking up.

Pulse rate and the amount of oxygen in the blood. This helps detect if breathing has been disrupted.

Other signs of sleep apnoea that tests may detect include abnormal heart rhythm or large increase in blood pressure during the night. Part of the diagnosis process will involve ruling out other causes of daytime sleepiness. These can include sleep deprivation, depression, narcolepsy (a condition involving an irresistible urge to sleep at any time of day) or neurological conditions such as Parkinson's.

Treatment:

Certain factors that are causing sleep apnoea, such as obesity, should be dealt with first. For example, by losing weight, the person may be cured of the condition. Changing sleeping position can help some people - sleeping on your side or front, rather than your back, discourages the tongue from rolling over the airway.

The most effective non-invasive (non-surgical) treatment for sleep apnoea is continuous positive airway pressure (CPAP). The patient wears a soft mask over their nose and mouth and a machine raises and regulates the pressure of the air they breathe, preventing the airway from collapsing during sleep. Many patients find that this treatment reduces daytime sleepiness and improves their concentration, although some experience facial or nasal pain.Feelings of claustrophobia sometimes occur.

If CPAP doesn't help a patient or if they cannot cope with the mask, sometimes surgery is required to manage snoring and sleep apnoea.

Surgery can involve correcting physiological abnormalities, such as removing nasal polyps. Other options include removing the adenoids, tonsils, or uvula (a tag of skin hanging down inside the mouth) or performing reconstructive surgery on the nose.

Complication:

People wakened frequently during the night, even without realising it, tend to feel sleepy the next day. The choking noises and the movements they make are also likely to cause serious disturbance to their partners. Sleepiness and lack of concentration during the day can be hazards at work, for example when operating machinery or driving. There is some evidence that sleep apnoea may be linked to high blood pressure (hypertension), strokes and heart attacks.

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