Definition:

Apnea Hypopnea Index>5 in a PSG study with daytime symptoms. Apnoea = period of complete cessation of oronasal airflow for minimum of 10s; period of more than 50% reduction of oronasal airflow with a decrease of more than 3% of ongoing saturated O₂ = hypopnea.
recurrent sleep-induced collapse of the pharyngeal airway leading to hypoxaemia, hypercapnia, with arousal from sleep required to re-establish airway patency
Obstructive: continued/raised diaphragm EMG activity and/or thoracoabdominal wall movement; thoracoabdominal paradox may be present
Central: absent diaphragm EMG and thoracoabdominal movement
Mixed: components of both

Mild to moderate OSA = AHI 5-30.

Prevalence: 2% adult females and 4% of adult males – estimated 80% of all mod to severe OSAS missed.

Features: characterized by repetitive obstruction of the upperairway during sleep, resulting in episodic hypoxemia and arousal,associated with symptoms, usually daytime sleepiness. It can cause impairment of cognitive function, changes in mood and personality, increase risk for CVSD.

Aetiology

Most patients have a anatomical predisposition for airway collapse
Factors promoting upper airway obstruction:
- anatomical narrowing of upper airway
- excessive loss of upper airway muscle tone
- defective upper airway protective reflexes
Site of airway collapse
- generally behind uvula and soft palate (retropalatal / nasopharynx)
- also behind the tongue (retroglossal / oropharynx)
- collapse at level of epiglottis is unusual

Diagnosis

Epworth Sleepiness Scale (ESS)
- validated self-administered questionnaire
- rate likelihood of falling asleep in different situations
- maximum score 24
- normal < 10
- significant sleepiness > 16
- Mean values for normal 6
- Mean value for OSAS 11
- Mean value for narcolepsy 18
- Mean value for insomnia 2

Neck circumference good predictor:
- <37cm, very negative predictor
- >48cm, high positive predictor
- >41cm, sensitivity of 61%
Craniofacial/upper airway features:
- retrognathia and overbite
- macroglossia (acromegaly, hypothyroidism, Down’s)
- oedema/erythema uvula common in heavy snoring

tonsillar/adenoidal hypertrophy

Definition:

Aetiology

Diagnosis

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