Obstructive sleep apnoea

Question 1

Definition

Answer 1

recurrent episodes of partial or complete upper airway obstruction during sleep. Defined by

• Cessation of airflow from nose/mouth for >10secs
• resulting in intermittent respiratory arrests
• interruption of REM sleep
• > 5 episodes/h

Question 2

Incidence

Answer 2

1-2% middle aged men

Question 3

Pathophysiology

Answer 3

OSA is caused by a collapse of the soft-tissue of the upper airway (oropharynx and velopharynx, or “throat”) during sleep.

Occur during stage 3 NREM, and REM sleep, as this is the period of the least muscle tone.

Muscles of breathing continue to act, but are unable to perform ventilation.

As a result, blood oxygen levels fall (hypoxia) and CO2 levels may rise (hypercapnia).

This causes a period of ‘neurological arousal’ - whereby the REM sleep is disturbed, and the brain is aroused to a higher state, and the airway is restored. This does not usually result in full awakening, but severely disrupts deep sleep periods.

The hypoxia associated with apnoeic episodes causes vasoconstriction, which leads to hypertension and pulmonary hypertension, and can ultimately cause cor pulmonale.

The hypertension seen in OSA often does not follow normal diurnal variation, and does not fall with sleep. In some patients it may actually paradoxically increase with sleep

Question 4

Causes

Answer 4

Obesity (80%) 
Male 
Acromegaly 
Hypothyroidism 
Alcohol

Question 5

Diagnosis

Answer 5

Day time sleepiness and snore when sleeping but not specific

Overnight polysomnography 
(EEG electroencepalography for brain wave, EOG (electrooculography) for eye movements, EM (electromyography)  - muscle activity, pulse oximetry) 

Epworth sleepiness score

Question 6

Epworth sleepines score

Answer 6

Self-selective tool for identigying sleepiness of any cause

STOP BANG
Snoring 
Tired 
Observed to stop breath during sleeps 
Pressure- hypertension 

B-BMI>35
Age >50
Neck circumgerence >40cm
Gender - male

Question 7

Classification

Answer 7

Apnoa-hypopnoea index

Index is calculated as the number of apnoeas+ hypopnoease per hour

Mild - 0-15 per hour
Moderate - 15-30 per hour
Severe >30 per hour

Question 8

Complications

Answer 8

Cognitive (memory problems, poor concentration, increased risk of accidents)

Cardiovascular (pulmonary hypertension, cor pulmonae, arrhythmias)

Stroke, type 2 DM

Question 9

Management

Answer 9

Weight loss
Home CPAP

These are the two main interventions

CPAP need to be regularly (every night), but those who are complaint have greatly reduced risk of complications.

Other lifestyle interventions include:

Cessation of smoking
Avoidance of alcohol in the evening
Avoidance of sedating medications
Other Interventions have inconclusive evidence, but may be of benefit in some patients, usually those with mild symptoms. These include:

Surgery
Mechanical devices, including oropharyngeal devices
Medications, e.g. modafini