Obstructive sleep apneoa Flashcards
What is it?
Obstructive sleep apnoea is characterised by recurrent episodes of complete or partial obstruction of the upper airway during sleep, causing apnoea or hypopnoea
Why does this occur?
Upper airway patency depends on dilator muscle
activity. All muscles relax during sleep (including
pharyngeal dilators).
Excessive narrowing can be due to either :
- an already small pharyngeal size during awake state which undergoes a normal degree of muscle
relaxation during sleep causing critical narrowing
- OR excessive narrowing occurring with relaxation during sleep
Risk factors?
- Increasing age
- Male sex
- Upper body Obesity
- Collar size >17 inches
- Alcohol
- Smoking
Causes of small pharyngeal size?
- Fatty infiltration of pharyngeal tissues and external
pressure from increased neck fat and/or muscle
bulk - Nasopharyngeal obstruction: large tonsils
- Craniofacial abnormalities- relatively undersized or set back mandible
- Extra submucosal tissue, e.g. myxoedema
Causes of excessive narrowing during sleep?
- Obesity may enhance residual muscle dilator
action - Neuromuscular disease with pharyngeal
involvement may lead to greater loss of dilator
muscle tone, e.g. stroke, MND, myotonic
dystrophy - Muscle relaxants – sedatives, alcohol
- Increasing age
Differentials to the symtoms ?
Narcolepsy
Hypothyroidism
Symptoms
- excessive daytime sleepiness (daytime somnolence)
- Recurrent arousals lead to highly fragmented and waking up unrefreshed from sleep
- Concentration problems
- excessive snoring
- Transient arousal required
Signs
- Reduces oxygen saturation during sleep
- Hypertension
- Heart failure
- compensated respiratory acidosis
What do we use to assess Sleepiness ?
Epworth Sleepiness Scale- questionnaire completed by patient +/- partner
In the sleepiness scale what do they use to measure it
- Points for following: 0=would never doze, 1=slight chance, 2=moderate chance, 3=high chance
- Sitting & reading
- Watching TV
- Sitting in a public place, e.g. theatre
- Passenger in a car for an hour
- Lying down to rest in the afternoon
- Sitting & talking
- Sitting quietly after lunch without alcohol
- In a car, while stopped in traffic
For the sleepiness scale: what score would make OSA likely and need to investigate further
> 9
What is the diagnostic test for OSA?
Sleep studies- Polysomnography
What are the types of polysomnography? Which one is most common ?
- Overnight oximetry alone
-
Limited sleep study – oximetry, snoring, body
movement, heart rate, oronasal flow,
chest/abdominal movements, leg movements –
usual study of choice - Full polysomnography – limited study plus EEG,
EMG
How many apnoeic episodes is significant?
- Apnoeic episodes ≤ 5 is normal
- Apnoeic episodes 5-15 mild
- Apnoeic episodes 15-30 Moderate
- Apnoeic episodes >30 severe
What is treatment based on?
on symptoms/quality of life – NOT on severity seen on sleep study
Correct reversible risk factors in OSA?
- weight loss
- Avoid/reduce evening alcohol
- Smoking cessation
- sleep decubitus rather than supine
Treatment for mild OSA
Mandibular advancement device
consider pharyngeal surgery as last resort
treatment for significant OSA?
- Nasal Continuous positive airway pressure (CPAP)is first line
- consider gastroplasty/bypass
- rarely tracheostomy
treatment in SEVERE OSA &CO2 retention?
May require a period of NIV prior to CPAP if acidotic, but compensated CO2 may reverse with CPAP alone
What is CPAP?
- Usually given via nasal mask, but can use
mouth/nose masks - Upper airways splinted open with approximately
10cm H2O pressure – this prevents airways
collapse, sleep fragmentation, and ultimately
daytime somnelence - Also opens collapsed alveoli and improves V/Q
matching
Is CPAP a form of ventilatory support like NIV
No
