Obstructive Sleep Apnoea Flashcards
What is obstructive sleep apnoea (OSA)?
Sleep-disorder breathing due to upper airway collapse leading to obstructive apnoea and hypopnoeas with desaturation.
Most common people getting OSA.
Middle aged overweight men.
Risk factors of OSA.
Age
Menopause
Obesity
Endocrine conditions such as acromegaly and hypothyroidism.
When might OSA occur in children?
Enlarged tonsils of trisomy 21.
Pathophysiology of OSA.
During sleep (especially REM) respiratory muscle activity is reduced. In REM only diaphragm is working.
Airway at back of the throat is sucked close (e.g. due to excessive neck fat) when breathing in during sleep in OSA.
Genioglossus and palatal muscles which keep the upper airway open when we are awake become hypotonic.
If there is complete occlusion this causes apnoea.
The apnoea leads to hypoxia and increasingly strenuous respiratory efforts.
The combination of hypoxia and effort to overcome obstruction wakes the patient up.
The awakening is so brief it’s not noticeable for the patient. This occurs throughout the night.
Symptoms of OSA.
Most common highest up…
Loud snoring
Daytime sleepiness
Unrefreshed sleep
Restless sleep
Morning headache
Nocturnal choking
Reduced libido
Mroning drunkenness
Ankle swelling
Causes of OSA.
Encroachment of pharynx such as obesity (fatty infiltration of pharyngeal tissues), large tonsils, craniofacial abnormalities and extra submucosal tissue (myxoedema)
Nasal obstruction like nasal deformities, rhinits, polyps and adenoids.
Respiratory depressant drugs like alcohol, sedatives, strong analgesics
Neuromuscular disease
How to diagnose OSA.
Relatives provide a snore-silence-snore cycle.
Symptom presentation such as poor concentration and waking up unrefreshed.
Patients are asked by Epworth Sleepiness Scale.
STOP BANG tool can be used to screen and differentiate from simple snoring.
Once the diagnosis is suspected, what further investigations should be done?
Overnight pulse oximetry, monitoring pulse and O2 levels done at home.
Nocturnal polygraphy can also be done.
What is the Epworth Sleepiness Scale?
A measure of excessive daytime sleepiness.
Broken into a chance of dozing from 0-3 when…
Sitting and reading,
Watching TV,
Sitting inactive in a public place,
Lying down to rest in the afternoon,
Sitting and talking to someone,
Sitting quietly after lunch,
In a car, while stopped for a few minutes in traffic.
What is a normal Epworth Sleepiness score?
<9
>9 might suggest OSA.
Explain the STOP BANG tool
Snoring?
Tiredness?
Observed apnoeas
Pressure (high BP)?
BMI? (>35)
Age? (>50)
Neck size? (> 43 cm male, 41 cm female)
Gender? (male)
Explain sleep-disordered investigation by overnight pulse oximetry, pulse monitoring and O2 levels.
Oximetry shows desaturations in a cyclical manner if OSA is suspected. The pattern is called sawtooth.
The oximetry desaturation index (ODI) measures the number of desaturations per hour.
This can determine the severity of sleep apnoea.
Overnight oximetry cannot distinguish between central and obstructive sleep apnoea.
How is this done?
By nocturnal polygraphy.
Explain nocturnal polygraphy.
Measures body posture, movements, breathing rate, EEG, and pulse oximetry.
This is only done when diagnosis is uncertain.
How is severity of OSA defined?
By apnoea-hypopnea index (AHI)
Explain AHI.
Number of episodes of apnoea or hypopnea per hour.
<5 is normal
5-15 is mild OSA
15-30 is moderate OSA
>30 is severe OSA
What is treatment based on in OSA?
On symptoms and quality of life not on severity in sleep studies.
Simple approach management of OSA.
Weight loss
Sleep decubitus instead of supine.
Avoid or reduce alcohol intake.
Treatment of OSA for snorers and mild OSA.
Mandibular advancement devices
Pharyngeal surgery as last resort.
Treatment of significant OSA.
Nasal CPAP
Gastroplasty/bypass
Very rarely tracheostomy
Treatment of severe OSA and CO2 retention.
NIV prior to CPAP if acidotic.
Compensated CO2 may reverse with CPAP alone.
What is CPAP?
Usually a nasal mask but can use mouth/nose masks as well.
Upper airways is splinted open with approx 10 cm H2O pressure.
This prevents the airway from collapsing.
Also prevents sleep fragmentation and ultimately daytime somnolence.
It also opens collapsed alveoli and improves V/Q mismatch.
Treatment ladder of OSA
Lifestyle changes with weight loss, sleeping on the side instead of back and avoiding or reducing alcohol (respiratory depressant).
If this is not enough and the symptoms and QOL are severly affected then you might want to move on to CPAP.
If this is still not enough or the person is not tolerating CPAP then surgery such as uvulopalatopharyngoplasty (UPPP) can be done. This is however rare.
Complications of OSA.
Can increase the risk of MI and stroke.
