Apnea

Apnea (from the Greek apnoia — “still air, absence of breath”) is a complete cessation of respiratory movements and pulmonary ventilation lasting 10 seconds or more. This condition is a hallmark manifestation of sleep-disordered breathing syndromes.

During an apneic event, pulmonary gas exchange ceases, leading to a drop in blood oxygen levels known as hypoxemia. Based on its underlying mechanism, apnea is classified into obstructive sleep apnea, caused by mechanical blockage of the airway, and central sleep apnea, resulting from impaired function of the brain’s respiratory center.

Aetiology and pathophysiology

There are two primary pathophysiological types of apnea:

• Obstructive Sleep Apnea (OSA). This is the most common form. It is caused by collapse of soft pharyngeal tissues (e.g., soft palate, tongue root) or enlarged adenoids, which physically obstruct airflow despite continued effort from the respiratory muscles.
• Central Sleep Apnea (CSA). This form occurs when the brain’s respiratory center fails to send impulses to the respiratory muscles. In this case, no respiratory effort is observed. Central sleep apnea is often associated with heart failure, stroke, or opioid use.

Clinical Significance

Sleep apnea typically presents with loud snoring, breathing pauses, and pronounced daytime sleepiness. Polysomnography is the gold standard for diagnosis. This study records multiple physiological parameters during sleep. The key diagnostic parameter is the apnea-hypopnea index (AHI), which helps determine disease severity.

Repeated apneic events lead to chronic hypoxemia and sleep fragmentation. The disease significantly increases the risk of arterial hypertension, myocardial infarction, stroke, and type 2 diabetes mellitus. Continuous positive airway pressure (CPAP) therapy is the primary treatment for obstructive sleep apnea.

Differential Diagnosis

A critical diagnostic task is differentiating between obstructive and central sleep apnea, as treatment approaches differ fundamentally. This distinction is reliably achieved only through polysomnography, which records the presence or absence of thoracic and abdominal respiratory effort during apneic events.