Snoring and Sleep Apnoea

32.1 Introduction

• Snoring, obstructive sleep apnoea (OSA), and upper airway resistance syndrome (UARS) are conditions within the same spectrum of sleep-related breathing disorders (SRBDs)

• Prevalence of OSA is 1 to 4% (adults)

• SRBD is caused by flutter and collapse of tissues in the pharynx, predominantly the palate/uvula and tongue base/epiglottis

32.2 Definitions

• Apnoea = cessation of respiratory airflow for at least 10 s with respiratory effort

• Hypopnoea = reduced respiratory flow by at least 50% for at least 10 s and a drop of SaO₂ by at least 4%, with respiratory effort

• Apnoea/hypopnoea index (AHI) = (apnoea + hypopnoea)/hour of sleep

• OSA = AHI ≥5; subdivided into:

Mild: AHI = 5 to 15

Moderate: AHI = 15 to 30

Severe: AHI > 30

• Obstructive sleep apnoea syndrome (OSAS) = OSA with symptoms

• UARS = symptoms of OSA and somnographic evidence of sleep fragmentation but AHI ≤5

• Central sleep apnoea = apnoea without respiratory effort. This has neurological aetiology and there is no upper airway obstruction

• Arousal = abrupt change from sleep to wakefulness

• Microarousal = partial awakening, from a “deep” to a “light” sleep; patient is not aware of wakefulness

32.3 Pathophysiology

• Inward collapse of loose and floppy tissues in pharynx secondary to Bernoulli principle (reduced intraluminal pressure with increased airflow) with increased respiratory effort, leading to airway obstruction or flutter

• Multilevel areas of obstruction when considering snoring and OSA with involvement of: soft palate, lateral pharyngeal wall, palatine tonsils, tongue base/lingual tonsils, epiglottis

• Apnoea/hypopnoea → hypoxia →increased respiratory effort →increased venous return →risk of right heart failure and cor pulmonale in the long term

• Arousals/micro-arousals → sleep fragmentation → physiological stress (catecholamines and other chemical release) →ιncreased risk of other complications, e.g., arrhythmias

• Sleep fragmentation results in poor quality sleep leading to excessive daytime sleepiness

• OSA leads to increased risk of arrhythmias, cerebrovascular accidents, cardiovascular disease, insulin resistance, lower life expectancy

• Sleep fragmentation also causes excessive daytime sleepiness, which has been shown to increase risk of road traffic accidents. It also causes poor concentration and mood changes