Obstructive Sleep Apnoea

Question 1

Definition of OSA

Answer 1

Disorder characterised by episodes of complete or partial closure/collapse of the pharyngeal airway (upper airway) during sleep. This leads to apnoeic periods (cessation of airflow >10 seconds) that are terminated by arousal from sleep

Question 2

Aetiology and risk factors for OSA

Answer 2

• An episode of OSA is caused by dynamic narrowing of the upper airway during sleep
• Can be due to neuromuscular mechanisms within an anatomically small airway

• Risk factors:
• Weight gain/obesity
• Smoking
• Alcohol
• Male
• Family Hx
• Chronic snoring
• Sedative use
• Enlarged tonsils
• Macroglossia
• Marfan’s syndrome

Question 3

Pathophysiology of OSA

Answer 3

• The upper pharyngeal dilator muscle activity DECREASES with sleep.
◦ The tone of the muscle decreases
◦ The pharynx is hence vulnerable to collapse during sleep

• Hypoxaemia and hypercapnia may result from the airway obstruction.
• Individuals with OSA would be at higher risk of developing CVD, stroke and metabolic issues

Question 4

History and examination of OSA

Answer 4

• Obesity
• Middle aged man
• Excessive daytime sleepiness: due to non-refreshing sleep
• Episodes of apnoea: episodic cessation of breathing terminated by a loud snore, commonly observed by partner
• Loud snoring
• Episodic gasp: commonly observed by partner
• Restless sleep/ poor sleep quality
• Reduced cognitive performance, reduced libido, mood changes: due to lack of sleep
• Morning headaches
• Macroglossia: may have large tongue
• Large neck circumference

Question 5

Investigations for OSA

Answer 5

• Polysomnography (PSG):
• Currently the definitive test
• Monitors O2 saturation, airflow at the nose and mouth, ECG, EMG, chest and abdominal wall movement during sleep
• Apnoea Hypoapnoea Index (AHI): would be scored, should be 15 or more episodes/hour (indicates significant OSA)

Question 6

Treatment for OSA

Answer 6

• Lifestyle changes:
◦ Weight reduction, avoid tobacco and alcohol

1) CPAP: via a nasal mask, is the treatment of choice
• Oral appliances: can be given to those with mild-moderate OSA or those who don’t like CPAP. Can use mandibular repositioning appliances

Anatomical lesions:
1) Upper airway surgery: first line for those with anatomical obstruction. E.g tonsillectomy

Question 7

Prevention and prognosis of OSA

Answer 7

• Lifestyle advice , sleeping in anon-supine position may help
• STOP-BANG score for risk of OSA

With adequate treatment the majority of patients report a better quality of life and reduced sleepiness

Question 8

Complications of OSA

Answer 8

• CVD: risk of hypertension, stroke, ACS etc is raised with OSA
• Depression: due to poor sleep
• Cognitive dysfunction
• Impaired glucose metabolism: occurs with short-term sleep deprivation
• Type 2 respiratory failure