Expansion
Repeated pharyngeal collapse causes intermittent hypoxia and arousals
Expansion
The cycle:
- Sleep reduces pharyngeal dilator tone
- Negative inspiratory pressure collapses the pharynx
- Continued effort against a closed airway, with hypoxia and hypercapnia
- Arousal restores tone and the airway opens, often with a loud snort
- Sleep resumes and the cycle repeats, sometimes hundreds of times a night
Consequences:
- Sleep fragmentation: daytime somnolence, poor concentration, accidents
- Intermittent hypoxia with reoxygenation generates oxidative stress and sympathetic activation, causing hypertension, arrhythmia (particularly atrial fibrillation), stroke and metabolic syndrome
- Large negative intrathoracic pressure swings raise cardiac afterload
- Chronic hypoxia can cause pulmonary hypertension and cor pulmonale
Severity is graded by the apnoea-hypopnoea index. Treatment with continuous positive airway pressure acts as a pneumatic splint, and weight loss, avoidance of alcohol and sedatives, and positional therapy all help.