Obstructive Sleep Apnea and Sleep Studies

What is obstructive sleep apnea?

Obstructive sleep apnea is a condition in which the muscles of the throat relax during sleep and the upper airway repeatedly narrows or closes. Each closure stops airflow for ten seconds or longer, oxygen levels fall, and the brain briefly wakes to restore muscle tone and reopen the airway. This cycle can repeat dozens or even hundreds of times a night. The person rarely remembers waking, but sleep is fragmented and never reaches the deep, restorative stages.

The consequences extend far beyond tiredness. Repeated drops in oxygen and surges of sympathetic activity raise blood pressure, promote heart rhythm disturbance, worsen insulin resistance, and increase the risk of heart attack, stroke and road traffic accidents. Sleep apnea is one of the commonest identifiable causes of blood pressure that will not come under control on three or more drugs.

Central sleep apnea, in which the brain intermittently fails to signal the breathing muscles, and obesity hypoventilation syndrome, in which carbon dioxide accumulates in severely obese patients, are related conditions that are identified on the same sleep study but treated differently.

Symptoms of sleep apnea

At night

• Loud, habitual snoring, often heard through a closed door.
• Witnessed pauses in breathing followed by a gasp, snort or choking sound, usually reported by the bed partner.
• Restless sleep, frequent turning, sweating, and dry mouth on waking.
• Waking repeatedly to pass urine at night.
• Acid reflux and heartburn during sleep.

During the day

• Excessive daytime sleepiness: dozing off while reading, watching television, in meetings, or at traffic signals.
• Morning headache and a feeling of never having slept enough despite adequate hours in bed.
• Poor concentration, memory lapses, irritability and low mood.
• Reduced libido and erectile dysfunction.

Symptoms in women are often less typical and are frequently attributed to stress, thyroid disease or anaemia: fatigue, insomnia, morning headache and mood change may dominate rather than classic loud snoring, which contributes to sleep apnea being under-diagnosed in women.

Who is at risk

Excess weight, particularly around the neck and abdomen, is the strongest modifiable risk factor, although a substantial number of patients in India have sleep apnea at a body mass index that would be considered normal in Western populations, because of craniofacial structure. Other contributors include a large neck circumference, a receding or small lower jaw, a crowded oropharynx and large tonsils, nasal blockage from a deviated septum or allergic rhinitis, male sex, increasing age, menopause, hypothyroidism, acromegaly, alcohol and sedatives taken at bedtime, and smoking.

Sleep apnea should be actively looked for in anyone with resistant hypertension, atrial fibrillation, type 2 diabetes with poor control, heart failure, previous stroke, or unexplained daytime sleepiness in a professional driver.

How sleep apnea is diagnosed

Clinical suspicion is raised by history from the patient and the bed partner, questionnaires such as STOP-BANG and the Epworth Sleepiness Scale, and examination of the nose, throat, jaw, neck circumference and body mass index. Diagnosis, however, requires objective sleep testing, because snoring alone does not establish apnea and the severity cannot be guessed from symptoms.

Polysomnography

An overnight laboratory sleep study is the reference standard. It records brain waves, eye and chin muscle activity to stage sleep, airflow at the nose and mouth, chest and abdominal effort, oxygen saturation, heart rhythm, snoring sound, body position and leg movements. This combination allows apneas and hypopneas to be counted, obstructive events to be distinguished from central ones, and other sleep disorders such as periodic limb movements to be identified.

Home sleep apnea testing

A simplified portable device recording airflow, effort, oxygen and pulse can be used at home in patients with a high probability of moderate to severe obstructive disease and no significant heart or lung comorbidity such as COPD. A negative home study in a symptomatic patient should be followed by full laboratory polysomnography.

Reading the result

The index is interpreted alongside the depth and duration of oxygen desaturation, the fragmentation of sleep, symptoms and cardiovascular comorbidity, since a patient with mild apnea and profound desaturation may need treatment more urgently than the number alone suggests.

Treatment of sleep apnea

Positive airway pressure

CPAP delivers a gentle stream of air through a mask that splints the upper airway open, abolishing apneas, restoring oxygen levels and consolidating sleep. It is the most effective treatment for moderate and severe disease. The pressure is set by a titration study or by an auto-adjusting device, and the mask type, humidification and pressure-relief settings are adjusted for comfort. Patients often notice clearer mornings, reduced blood pressure and better concentration within the first weeks. BiPAP or adaptive servo-ventilation is used for central apnea, hypoventilation and patients who cannot tolerate a single fixed pressure.

Weight and lifestyle

A sustained weight reduction of even ten per cent can significantly reduce the apnea index, and bariatric surgery is considered in severe obesity. Avoiding alcohol and sedatives in the evening, stopping smoking, treating nasal allergy and blockage, and sleeping on the side rather than the back all contribute. Positional therapy helps the subset of patients whose events occur almost entirely when supine.

Oral appliances and surgery

A custom mandibular advancement device made by a dentist experienced in sleep medicine is a reasonable option for mild to moderate disease, for snoring, and for patients who cannot tolerate CPAP. Surgical options, chosen after careful airway assessment, include septoplasty and turbinate reduction for nasal obstruction, tonsillectomy and adenoidectomy, which is the primary treatment in children, and maxillomandibular advancement in selected skeletal abnormalities.

Living with CPAP

Most difficulty with CPAP occurs in the first few weeks and is solvable. Mask leak and pressure sores are usually a fitting problem, dryness and nasal congestion respond to heated humidification and saline, and a sensation of too much pressure often improves with ramp and expiratory pressure relief settings. Download of usage and residual event data at follow-up allows the settings to be refined objectively. Devices should be cleaned as advised, filters changed, and masks and tubing replaced periodically. Untreated apnea returns as soon as therapy stops, so CPAP is a long-term treatment rather than a course.

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