Obstructive Sleep Apnoea (OSA)
Definition
Epidemiology
Increasingly M=F from M>F
Clinically significant sleep apnoea: 2-4% (common)
Risk Factors
Aetiopathogenesis
Obstruction around base of tongue (epiglottis, front and back wall of larynx) --> Brainstem arousal mechanism withdraws from REM sleep to NREM phases regain mm tone to breathe --> broken sleep pattern --> sleep drive strong --> sleep --> wake --> sleep
Clinical Features
Symptoms
Daytime somnolence, even with enough hours of sleep
Witness apnoea (observation of obstructive breathing pattern)
Unaware of night time events
Investigations
Polysomnography (Gold standard)
Classification:
Management
Complications
Heart failure/ Atrial arrhythymia/ ++ risk IHD (obstruction --> ++ adrenaline --> ++ work)
CPAP complications (poor fit, flatulences, sinusitis, worst outcome = non compliance)
Nocturia (-- thoracic pressure --> ++ RA pressure --> ++ ANP --> diuresis)
Diaphoresis (obstruction --> ++ adrenaline --> sympathetic sweating)
Source
Dr Gregory Haug 2014
- Apnoea = no breathing; zero airflow for 10s
- Obstructive apnoea = chest movement with no airflow
- Central apnoea = no airflow no effort
- Hypopnoea = insufficient movement of air into lungs
- Apnoea Hypopnoea Index (AHI): All apnoea/ hypopnoea (<5 = normal)
- Amount of sleep: ~7h, regular times, pattern
- Time taken to fall asleep (sleep latency): 7-10min
- Time of all NREM phase (REM latency): 7 min - 1h from lights out
- NREM1: light sleep
- NREM2: deeper sleep
- NREM3/4: slow wave sleep; important phase of sleep, growth hormones secreted
- REM: total mm paralysis, except ocular mm+diaphragm, to be refreshed
- 1 cycle ~ 1h-1.5h; more slow wave sleep, earlier in sleep, more REM later in sleep
- Children: A lot more slow wave than adults
Epidemiology
Increasingly M=F from M>F
Clinically significant sleep apnoea: 2-4% (common)
Risk Factors
- Obesity (compression of upper airway, not because they are too fat to breathe)
- Pierre Robin syndrome (smaller than normal jaw)
Aetiopathogenesis
Obstruction around base of tongue (epiglottis, front and back wall of larynx) --> Brainstem arousal mechanism withdraws from REM sleep to NREM phases regain mm tone to breathe --> broken sleep pattern --> sleep drive strong --> sleep --> wake --> sleep
Clinical Features
Symptoms
Daytime somnolence, even with enough hours of sleep
Witness apnoea (observation of obstructive breathing pattern)
Unaware of night time events
Investigations
Polysomnography (Gold standard)
- EEG (identify NREM.REM sleep)
- EMG (mm tone)
- O2: Oximetry (can drop to 70%), air flow (nasal prongs w pressure transducers), effort band (identify effort to breathe)
- Autonomic trigger: ECG (tachy), BP (htn), Pulse (variability)
Classification:
- Normal: AHI < 5/ hour
- Mild: AHI 5-15
- Moderate: AHI 15-25
- Severe: AHI >25
Management
- Lose weight
- CPAP (1/3 easy compliance, 1/3 hard but can comply, 1/3 non compliant)
- Splint to draw mandible forward
- Last resort: tracheostomy
Complications
Heart failure/ Atrial arrhythymia/ ++ risk IHD (obstruction --> ++ adrenaline --> ++ work)
CPAP complications (poor fit, flatulences, sinusitis, worst outcome = non compliance)
Nocturia (-- thoracic pressure --> ++ RA pressure --> ++ ANP --> diuresis)
Diaphoresis (obstruction --> ++ adrenaline --> sympathetic sweating)
Source
Dr Gregory Haug 2014