Sleep disordered breathing

Question 1

What is classed as sleep restriction?

Answer 1

<8 hours

Question 2

What gland secretes melatonin? What is it stimulated by?

Answer 2

pineal gland
stimulated by darkness

Question 3

Which type of sleep has normal breathing?

Answer 3

NREM (non-rapid eye movement)

Question 4

Describe muscles and breathing in REM sleep

Answer 4

muscles atonic except diaphragm
breathing erratic
sleep apnoea exaggerated in REM sleep

Question 5

List 4 types of sleep disordered breathing

Answer 5

obstructive sleep apnoea (OSA)
central sleep apnoea
mixed obstructive/central sleep apnoea
obesity hypoventilation syndrome (OHS)

Question 6

Pathophysiology of obstructive sleep apnoea

Answer 6

lack of tone in pharyngeal dilator muscles (genioglossus)
- can block lumen of airway

Question 7

History/clinical presentation of obstructive sleep apnoea

Answer 7

snoring
witnessed apnoea
excessive daytime sleepiness (EDS)
nocturia
unrefreshed sleep
morning headaches (disappear as day goes on)

Question 8

What is it important to ask about in history with obstructive sleep apnoea?

Answer 8

occupation and driving (eg. could be unsafe)
medications (opioids)
PMH (thyroid diseases, diabetes, systemic hypertension, cardiovascular and cerebrovascular diseases)
Trisomy 21 (increases risk - low muscle tone)
past surgical history (tonsillectomy)

Question 9

Describe a scale to quantify sleepiness

Answer 9

Epworth sleepiness scale
excessive sleepiness could be due to any sleep disorder
>11/24 = pathological
patients not always truthful (eg. scared about losing driving licence)
sleepiness can change on a daily basis

Question 10

Features to look for on examination when suspecting obstructive sleep apnoea

Answer 10

obesity (BMI>30kg/m2)
upper airways + enlarged tonsils
acromegaly, hypothyroidism, Cushing’s syndrome
micrognathia (small mandible)
retrognathia (receding mandible)

Question 11

Define apnoea

Answer 11

cessation of breathing for >10 seconds (usually >4% SpO2 desaturation)

Question 12

Define hypopnoea

Answer 12

decrease in airflow (nasal flow) by 50% or more (may not cause O2 desaturation)

Question 13

What is a normal apnoea hypopnoea index?

Answer 13

<5 episodes/hour of recorded sleep

Question 14

Describe apnoea hypopnoea index (AHI) interpretation

Answer 14

5-15 = mild OSA
15-30 = moderate OSA
>30 = severe OSA

Question 15

What is considered a significant O2 desaturation in a sleep study?

Answer 15

> 4% desaturation

Question 16

What is OSA Syndrome (OSAS)?

Answer 16

abnormal sleep study and excessive day time sleepiness = OSAS

abnormal sleep study + no excessive day time sleepiness = OSA

Question 17

What variables should be monitored in a sleep study?

Answer 17

SpO2
HR
body position
snoring
apnoeas/hypopnoeas

Question 18

Treatment of obstructive sleep apnoea

Answer 18

lifestyle modifications
weight reduction (if obese)
sleep hygiene (eg. reduce caffeine intake)
positional training (eg. not on back)
mandibular advancement devices (pushes lower jaw forward therefore more space at back of throat)

continuous positive airway pressure (CPAP) -> definitive therapy for OSAS (moderate/severe) -> air blown through mouth to keep pharynx open

Question 19

How does OSA affect driving?

Answer 19

have to declare diagnosis to DVLA
CPAP compliance >4 hours/night
HGV/public transport drivers = must inform employers and do occupational health assessment

Question 20

What causes obesity hypoventilation syndrome?

Answer 20

morbid obesity (BMI>35kg/m2)

Question 21

What do tests show in obesity hypoventilation syndrome?

Answer 21

mean SpO2 <90% in sleep study
time spent <90% SpO2 measured
daytime CO2 retention and/or increased bicarbonate

shallow breaths and low tidal volume at night)

Question 22

Obesity hypoventilation syndrome treatment

Answer 22

weight loss
non-invasive ventilation

Question 23

Which lung diseases are often co-existent with obstructive sleep apnoea?

Answer 23

asthma (moderate/severe)
COPD/emphysema

Question 24

Consequences of systemic hypoventilation

Answer 24

systemic hypertension
AF
MI/CVA
Pulmonary arterial hypertension