Definitions of obstructive sleep disordered breathing (SDB) and its clinical entities

Obstructive SDBA syndrome of upper airway dysfunction during sleep characterised by snoring and/or increased respiratory effort that result from increased upper airway resistance and pharyngeal collapsibility
Clinical entities
 Primary snoringHabitual snoring (>3 nights per week) without apnoeas, hypopnoeas, frequent arousals from sleep or gas exchange abnormalities
 Upper airway resistance syndromeSnoring, increased work of breathing, frequent arousals, but no recognisable obstructive events or gas exchange abnormalities
 Obstructive hypoventilationSnoring and abnormally elevated partial pressure of carbon dioxide in the absence of recognisable obstructive events
 Obstructive sleep apnoea syndromeRecurrent events of partial or complete upper airway obstruction (hypopnoeas, obstructive or mixed apnoeas) with disruption of normal oxygenation, ventilation and sleep pattern

Information from [4, 5].