Obstructive Sleep Apnoea

Description

Apnoea, defined as a temporary absence or cessation of breathing is commonly associated with Obstructive Sleep Apnea Hypopnea Syndrome (OSAHS), a condition in which a person experiences repeated episodes of apnoea because of a narrowing or closure of the pharyngeal airway during sleep. A decrease in the tone of the muscles supporting the airway during sleep can cause complete closure (obstruction) stops airflow (apnoea) or  partial obstruction decreasing airflow (hypopnoea). OSAHS results in episodes of brief awakening (arousals) from sleep to restore normal breathing.

Diagnosis

Moderate to severe OSAHS can be diagnosed from patient history and a home or laboratory sleep study using PSG. In some cases, further studies that monitor additional physiological variables in a sleep laboratory may be required, especially when alternative diagnoses are being considered. The severity of OSAHS is usually assessed on the basis of both severity of symptoms (particularly the degree of sleepiness) and the sleep study, by using the apnoea/hypopnoea index (AHI) otherwise known as the Respiratory Disturbance Index (RDI). OSAHS is considered mild when the AHI is 5-14 in a sleep study, moderate when the AHI is 15-30, and severe when the AHI is over 30. In addition to the AHI, the severity of symptoms is also important.

Symptoms

The symptoms of OSAHS include impaired alertness, cognitive impairment, excessive daytime sleepiness, snoring, nocturia, morning headaches and sexual dysfunction. The sleep quality of partners may also be affected. Excessive daytime sleepiness can adversely affect cognitive function, mood and quality of life. OSAHS is associated with high blood pressure, which increases the risk of cardiovascular disease and stroke. OSAHS has also been associated with an increased risk of road traffic accidents and is the reason we have undertaken the Mine Sleep Health Assessment Initiative sponsored by ourselves Respiratory and Sleep Specialists as well as BHP Billiton Mitsubishi Alliance to ensure safe driving of commercial vehicles for miners.

Treatment

Treatments aim to reduce daytime sleepiness by reducing the number of episodes of apnoea/hypopnoea experienced during sleep. The alternatives to CPAP are lifestyle management, dental devices and surgery. Lifestyle management involves helping people to lose weight, stop smoking and/or decrease alcohol consumption. Dental devices are designed to keep the upper airway open during sleep. The efficacy of dental devices has been established in clinical trials, but these devices are traditionally viewed as a treatment option only for mild to moderate OSAHS.

Further Reading

Sleep Med. 2006 Jun;7(4):385-6. Non-positional severe obstructive sleep apnea on polysomnogram became positional OSA with CPAP therapy. Siddiqui F, Osuna E, Chokroverty S.