Obstructive Sleep Apnoea

Question 1

What is obstructive sleep apnoea?

Answer 1

Intermittement closure/collapse of pharyngeal airway causing apnoeic episodes during sleep; these apnoeic episodes are terminated by partial arousal. Causes sufficient sleep framentation to result in significant daytime symptoms- usually excessive sleepiness.

Question 2

Discuss the stereotypical appearance for someone with obstructive sleep apnoea

Answer 2

Most pts with significant sleep apnoea are:

• Male
• Upper body obesity
• Relatively undersized or set back mandible

Question 3

Discuss the pathophysiology of obstructive sleep apnoea

Answer 3

• When you sleep all muscles relax; this includes pharygneal dilators which are respsonsible for airway patency
• Since pharyngeal dilators relax, some loss of tone and hence some narrowing is normal in sleep
• Excessive narrowing can be due to:
  
  • An already small pharyngeal size undergoing normal degree of muscle relaxation
  • Excessive narrowing of a normal pharyngeal size

Question 4

We have already said that excessive narrowing in OSA can be due to an already narrow pharyngeal size undergoing normal relaxation; state some causes of a small pharyngeal size

Answer 4

• Fatty infiltration of pharyngeal tissues
• External pressure from increased neck fat and/or muscle bulk
• Large tonsils
• Craniofacial abnormalities
• Extra submucosal tissue e.g. myoxedema

Question 5

We have already said that excessive narrowing in OSA can be due to excessive narrowing of a normal pharyngeal size; state some causes of excessive narrowing

Answer 5

• Obesity may enhance residual muscle dilator action
• Neuromuscular disease with pharyngeal involvement may lead to greater loss of muscle tone e.g. stroke, MND etc..
• Muscle relaxants e.g. sedatives, alcohol
• Increaseing age

Question 6

Discuss the symptoms someone with OSA may present with

Answer 6

• Loud snoring
• Daytime sleepiness
• Poor sleep quality
• Morning headache
• Nocturia
• Decreased cognitive performance
• Decreased libido
• Nocturnal sweating
• Oesophageal reflux

***Last 3 less common

Question 7

What happens to bp with every arousal in OSA?

What happens to daytime bp in pts with OSA?

Answer 7

• With every arousal there is rise in bp- often over 50mmHg (not clear if it damages CVS)
• Rise in daytime bp

Question 8

Discuss how we can measure daytime sleepiness of someone with suspected OSA

Answer 8

Question 9

What might you find on clinical examination of someone with OSA?

Answer 9

• Appearance: often male with upper body obesity and excess neck fat and/or muscle
• Obstruction of upper airway e.g. enlarged tonsils, myoxedema
• Signs related to potential consequences of OSA:
  
  • Hypertension
  • Cor pulmonale
    
    • Hepatomegaly
    • Raised JVP
  • Congestive heart failure
    
    • Bibasal crepitations
    • Pedal oedeama
  • Arrhythmias

Question 10

Discuss the different ways in which we can diagnose OSA

Answer 10

• Overnight pulse oximetry
• Limited sleep studies:
  
  • Oximetry
  • Snoring
  • Body movement
  • HR
  • Oronasal flow
  • Chest/abdo movements
  • Leg movements
• Full polysomnography:
  
  • Limited study
  • • EEG
  • • EMG

*In both sleep studies, apnoeas and hypopnoeas are scored and added together to give an apnoea-hypopnoea index (AHI). If AHI >15 (hence pt having more than 15 incidences per hour) or pt has more than 5 episodes per hour and is symptomatic- diagnosis of OSA

Question 11

Discuss the treatment for OSA, think about:

• Simple/lifestyle approaches
• For snorers & mild OSA
• Significant OSA
• Severe OSA

Answer 11

Simple/Lifestyle Approaches

• Weigh loss
• Sleep decubitis rather than supine
• Avoid/reduce evening alcohol intake

For Snorers & Mild OSA:

• Mandibular advancement devices
• Pharyngeal surgery as last resort

For Significant OSA:

• Nasal CPAP
• Gastroplasty/bypass
• Tracheostomy (rarely)

Very Severe OSA with CO2 retention:

• May require period of NIV prior to CPAP if acidotic

Question 12

What driving advice must you give to pts with OSA?

Answer 12

• Not to drive while sleepy- must stop & nap
• MUST notify DVLA
• Doctor can advise pts to stop driving altogether (e.g. if HGV driver this may be appropriate)

Question 13

Discuss some potential complications of OSA

Answer 13

• Pulmonary hypertension
  
  • Cor pulmonale
• Type II respiratory failure
  
  • Hypercapnia
• Independent risk factor for systemic hypertension
  
  • CVD
    
    • MI
  • Stroke
  • CKD

​****Pulmonary & systemic hypertension possibly due to hypoxia causing oxidative stress leading to endothelial dysfunction & sympathetic activation)

Question 14

Discuss how CPAP helps OSA

Answer 14

• Usually given via nasal mask (but can use mouth/nose masks)
• Upper airways kept open by ~10cm H20 pressure (from continuous positive airway pressure from CPAP)
• Prevents airway collapse
• Also opens closed alveoli to increase V:Q ratio

Question 15

Remind yourself of the difference between CPAP and BIPAP

Answer 15

CPAP

• Continuous positive airway pressure during insp & exp
• Useful to keep airways open and force ‘stuff’ out of alveoli hence used in e.g. OSA, pulmonary oedema, pneumonia etc..

BIPAP (also referred to as NIV)

• Inspiratory positive pressure is greater than expiratory postive pressure. Can also set back up rates so machine operates when resp rate drops below a fixed level
• Useful to help ventilation so e.g. in type II respiratory failure