Obstructive Sleep Apnoea

Question 1

What is obstructive sleep apnoea?

Answer 1

Upper airway obstruction during sleep

Question 2

What is the clinical definition of obstructive sleep apnoea?

Answer 2

Upper airway narrowing, provoked by sleep, causing sufficient sleep fragmentation to result in significant day time symptoms, usually excessive sleepiness

Question 3

Describe a typical patient with obstructive sleep apnoea

Answer 3

Male
Upper body obesity (collar size >17inches)
Undersized or set back mandible

Question 4

What is the pathophysiology behind obstructive sleep apnoea?

Answer 4

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 is even smaller at night when there is normal dilatation or excessive narrowing occurring with relaxation during sleep

Question 5

What are 4 causes of small pharyngeal size?

Answer 5

Fatty infiltration of pharyngeal tissues with external pressure from increased neck fat/muscle
Large tonsils
Craniofacial abnormality
Extra submucosal tissue eg myxoedema

Question 6

What are 4 causes of excessive narrowing of the airway during sleep?

Answer 6

Obesity enhances residual dilator action
Neuromuscular disease with pharyngeal involvement may lead to greater loss of dilator muscle tone e.g. stroke, MND,
Muscle relaxants like sedatives or alcohol
Increasing age

Question 7

What is the immediate effect of OSA?

Answer 7

Repetitive upper airway collapse with arousal required to re activate the pharyngeal dilators
There may be associated hypoxia and hypercapnia which are corrected during the inter-apnoeic hyper ventilatory period

Question 8

What are the impacts of OSA?

Answer 8

Recurrent arousals lead to fragmented and unrefreshing sleep leading to excessive day time sleepiness

Question 9

How can day time sleepiness be measured?

Answer 9

Epworth Sleepiness Scale

Question 10

What is a consequence on the body to arousal from sleep?

Answer 10

There is a rise in BP with every arousal - often over 50mmHg This may damage CVS
Rise in daytime BP
Nocturia

Question 11

What are some less common side effects of OSA?

Answer 11

Nocturnal sweating
Reduced libido
Oesophageal reflux

Question 12

What types of sleep study can be used to diagnose OSA?

Answer 12

Overnight oximetry alone
Limited sleep study
Full polysomnography

Question 13

What does a limited sleep study involve?

Answer 13

Oximetry, snoring, body movement, HR, oronasal flow, chest/abdo/leg movements

Question 14

What is involved in full polysomnography?

Answer 14

Limited sleep study plus ECG and EMG

Question 15

What is the management of OSA based on?

Answer 15

Quality of life

Question 16

What are some simple approaches to OSA management?

Answer 16

Weight loss, sleep decubitus not supine, avoid alcohol in the evening

Question 17

How can mild OSA and snoring be managed?

Answer 17

Mandibular advancement device

?Pharyngeal surgery

Question 18

How can significant OSA be managed?

Answer 18

Nasal CPAP
Gastric bypass
?Tracheostomy

Question 19

How can severe OSA with CO2 retention be manages?

Answer 19

NIV then CPAP if acidotic

or CPAP alone

Question 20

How is CPAP usually delivered?

Answer 20

Given via nasal mask

but can use mouth/nose mask

Question 21

How does CPAP work?

Answer 21

Upper airways are splinted open with approximately 10mmHg H2O pressure

Question 22

What is the principle behind CPAP?

Answer 22

It prevents airway collapse, sleep fragmentation and day time sleepiness
Opens collapsed alveoli
Improves V/Q mismatch

Question 23

Does CPAP provide ventilatory support and why?

Answer 23

It provides a constant positive pressure during inspiration and expiration so is not a form of ventilatory supportt

Question 24

What is CPAP used for?

Answer 24

It can be used to treat OSA and sometimes in acute respiratory failure e.g. pulmonary oedema

Question 25

What is NIV and does it provide ventilatory support?

Answer 25

Does provide ventilatory support
Two levels of positive pressure (bilevel) for inspiratory and expiratory
Can also be set up with back up rates so the machine operates when the RR drops below a fixed level