Define obstructive sleep apnoea.
Episodes of complete or partial upper airway obstruction during sleep, associated with oxyhaemoglobin desaturations and arousals from sleep.
What are the presenting symptoms of obstructive sleep apnoea?
- Snoring
- Witnessed apnoeas, which often interrupt snoring and end with a snort
- Choking episodes during sleep
- Nocturia
- Insomnia
- Decreased libido
- Daytime fatigue/tiredness - non restorative sleep; impaired concentration; morning headaches
- Dry mouth
- Other presenting conditions: obesity, cardiovascular disease, endocrine diseases e.g. PCOS, Cushing’s, T2DM
What is the epidemiology of OSA?
- Affects 4% of men and 2% of women in the US
- Snoring affects 25% of women, 30% of men
- Incidence is increasing
What are the criteria for diagnosing sleep apnoea?
Apnoea-Hypopnoea Index (the sum per hour of episodes of apnoeas and hypopnoeas)
Respiratory Distress Index (the sum per hour of episodes of apnoea, hypopnoea, and respiratory effort-related arousals) established with polysomnography or portable sleep test is ≥15 episodes/hour. However, 5 episodes/hour is considered sufficient for diagnosis if additional symptoms or comorbidities are present.
Describe the pathophysiology of OSA.
- Upper airway collapse during sleep
- Airway narrowing can be triggered by neuromuscular changes, anatomical narrowing or adenotonsillar hypertrophy. Neuromuscular dysfunction may prevent maintenance of pharyngeal dilator tone during sleep in people with OSA who have narrowed pharynx
- Pharyngeal dilator tone decreases during sleep onset. Tonic and phasic dilator activity is also decreased during REM sleep. So pharynx obstructs
- During sleep, pharynx is most vulnerable to collapse at end expiration secondary to loss of neural tone of pharyngeal dilators and loss of positive intraluminal pressure.
- Hypoxaemia and hypercapnia may result from airway obstruction, their magnitude also depending on the presence of pulmonary disease and reserve
- Episodes of apnoea and hypopnoea terminate with cortical or subcortical arousal.
- Autonomic sympathetic activation occurs, which may result in cardiac dysrhythmias and vasoconstriction.
- Sleep is resumed but the cycle of pharyngeal obstruction is repeated.
What are the risk factors for OSA?
- Obesity (strongest risk factor)/Large neck circumference e.g. collar size >17 in men and >15 in women
- Increased volume of soft tissues (tonsils/adenoids/tongue)
- Possibly genetic tendency related to jaw morphology.
- Male gender/post menopausal women
- Middle age (55-59 in men, 60-64 in women).
- Smoking.
- Sedative drugs.
- Excess alcohol consumption.
- Habitual snoring
- Family history
- Conditions: hypothyroidism/ PCOS/ Down’s syndrome/ mucopolysaccharidosis
- Some ethnicities - black, Hispanic, Asian ethnicity.
What are the 3 S’s of OSA?
S noring, S leepiness, and S ignificant-other report of sleep apnea episodes
Which muscle action is increased in people with a reduced pharyngeal cross-sectional area when awake?
When awake, genioglossus activity is increased in OSA patients to compensate for reduced pharyngeal area and to maintain patency.
What are the long-term consequences of OSA?
Higher rates of :
- CVD - HTN, stroke, MI, heart failure, cardiac dysrhythmias,
- Cognitive dysfunction, depression,
- Metabolic syndrome, oxidative stress,
- Motor vehicle accidents
What investigations would you do for OSA?
- BMI, collar size
- Ask partner for apnoea
- Epworth scale - daytime somnolence
Other:
- Polysomnography/”Sleep study” (definitive test) - result: Apnoea-Hypopnoea Index (AHI) ≥15 episodes/hour
- Portable multi-channel sleep tests - used in patients with less comorbidities. Respiratory Event Index (REI) of 15 or more episodes/hr.
- Awake fibreoptic endoscopy - to exclude polyps/lesions/tumours causing OSA.
sWhat is polysomnography and how is it used in the diagnosis of OSA?
- A sleep study used to diagnose sleep disorders.
- May involve CPAP titration
- Apnoeas and hypopnoeas are scored and added to determine the AHI.
- Includes EEG, electro-oculographic recording, air flow assessment, EMG, capnography, oesophageal manometry, ECG, and pulse oximetry.
How do you treat OSA?
Conservative:
- Weight loss - best predictor of success
- Stop hypnotics, narcotics, sedatives, alcohol
- Mandibular advancement devices (jaw thrust to open airway)
Medical:
- Continuous CPAP
- If CPAP intolerant then MRAs(mandibular repositioning appliances
Surgical:
- No universal procedure - needs to be tailored to the problem. Ultimate tx would be tracheostomy but this is not popular…
What is the difference between partial and complete apnoea?
- Complete apnoea= ten-second pause in breathing activity.
- Partial apnoea(hypopnoea) = ten-second period in which ventilation is reduced by at least 50%.
How common is snoring?
25% of females
30% males
What are the sleep-disordered breathing syndromes from mild to severe?
What is the pathophysiology of snoring?
Increase in negative intrathoracic pressure to draw air in is less efficient
Instead there is central venous pooling - raised CVP - raised ICP
Right heart fills with blood which puts pressure on left heart and raises pulmonary pressure
This can cause pulmonary hypertension
What is the consequence of snoring and hypoxia?
- Pulmonary and arterial hypertension due to snoring
- Asphyxia and hypoxia
- Arousal from sleep - stage IV and REM sacrificed
- Sympathetic activity rises - stays elevated all day e.g. cortisol
What can cause snoring?(ENT-related)
- Lymphoid hyperplasia e.g. adenoids
- Nasal blockage
- Tongue-base collapse
What are the legal and safety implications of OSA?
Heavy machinery, HGV drivers and airline pilots affected.
HGV drivers need to report OSA to DVLA and stop driving until symptoms are under control
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[1] Bronchiectasis25
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[4] Asthma61
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[5] Atelectasis36
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[7] Pleural Empyema18
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[9] Sarcoidosis52
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[10] Tuberculosis82
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[12] Pulmonary Aspergillus Infections27
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Idiopathic Pulmonary Fibrosis18
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Occupational Lung Disease22
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Pulmonary Vascular Disease24
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Respiratory Failure30
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Lung Cancer77
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Interstitial Lung Disease159
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Extrinsic allergic alveoltis17
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Asbestos-related lung disease (incl. asbestosis and mesothelioma)24
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Acute bronchitis11
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Obstructive sleep apnoea19
