Obstructive Sleep Apnoea

Overview

Obstructive sleep apnoea (OSA) is the most common sleep-related breathing disorder, characterised by recurrent episodes of complete or partial obstruction of the upper airway during sleep. These episodes, termed "apnoeas" (complete cessation of breathing) and "hypopneas" (partial reduction in breathing), lead to reduced or absent airflow, resulting in decreased blood oxygen levels and sleep disruption.

Classification

OSA is classified into adult and paediatric categories. It is differentiated from central sleep apnoea (CSA), where the cessation in breathing is due to decreased effort rather than airway obstruction. The severity of OSA is often measured using the Apnoea-Hypopnea Index (AHI), which counts the number of episodes per hour of sleep.

Signs and Symptoms

Common symptoms include unexplained daytime sleepiness, restless sleep, and loud snoring with periods of silence followed by gasps. Other symptoms may include morning headaches, trouble concentrating, mood changes, increased heart rate or blood pressure, decreased sex drive, and increased urinary frequency.

Children with OSA may exhibit hyperactivity, irritability, and poor growth due to the intense work of breathing and discomfort while eating. In adults, excessive daytime sleepiness is a hallmark symptom, often leading to brief sleep episodes during the day.

Pathophysiology

The transition from wakefulness to sleep, especially REM sleep, results in reduced upper-airway muscle tone, leading to airway obstruction. This can cause significant sleep disruption and a reduction in restorative sleep stages. The cycle includes muscle-tone loss, airway blockage, and partial awakening to restore airway patency, often measured using polysomnography.

Risk Factors

Risk factors for OSA include obesity, advanced age, decreased muscle tone due to drugs or neurological disorders, increased soft tissue around the airway, and structural features like enlarged tonsils or a narrow airway. Lifestyle factors such as smoking and alcohol consumption also contribute to OSA. Certain craniofacial syndromes and genetic components can increase susceptibility to OSA.

Diagnosis

Diagnosis is made based on recurrent episodes of partial or complete airway collapse during sleep, leading to apnoeas or hypopneas. The Apnoea-Hypopnea Index (AHI) and the Respiratory Disturbance Index (RDI) are used to determine the severity. Polysomnography is the gold standard for diagnosis, monitoring several physiological parameters during sleep.

Treatment

Treatment options for OSA include lifestyle changes, such as weight loss and avoiding alcohol and smoking. Continuous positive airway pressure (CPAP) is the most common treatment, providing a steady stream of air to keep the airway open. Mandibular advancement devices are also effective. In some cases, surgical interventions like uvulopalatopharyngoplasty (UPPP) or tonsillectomy may be necessary.

Physical Intervention

Positive airway pressure therapies, such as CPAP, VPAP, and nasal EPAP, are widely used. Oral appliances that adjust the jaw position can also be beneficial. Elevating the upper body during sleep and sleeping on the side can help prevent airway collapse.

Surgery

Surgical treatments are tailored to the patient's specific needs, with options including septoplasty, tonsillectomy, and maxillomandibular advancement. For children, adenotonsillectomy is often the first line of treatment.

Neurostimulation

Neurostimulation devices can be used for patients who cannot tolerate CPAP. These devices stimulate the hypoglossal nerve to maintain muscle tone and prevent airway collapse.

Consequences

In children, untreated OSA can lead to learning and memory deficits, behavioural issues, and cardiovascular problems. In adults, OSA is associated with cognitive impairments, cardiovascular diseases, diabetes, and increased mortality. Effective treatment can significantly improve these outcomes and enhance the quality of life.

Epidemiology

OSA affects approximately 9% to 38% of the general population aged 18 and older, with higher prevalence in men and older adults. The incidence has increased due to rising obesity rates. Despite its prevalence, OSA is underdiagnosed, particularly in individuals without daytime sleepiness.

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Self-assessment MCQs (single best answer)

What is the most common sleep-related breathing disorder?

Which index is commonly used to measure the severity of OSA?

Which symptom is a hallmark of OSA in adults?

What physiological change primarily contributes to airway obstruction in OSA?

Which lifestyle factor is NOT a risk factor for OSA?

What is the gold standard for diagnosing OSA?

Which treatment is the most common for OSA?

Which surgical intervention might be used to treat OSA?

In children, which symptom might indicate OSA?

What is the prevalence of OSA in the general population aged 18 and older?