Sleep disordered breathing Flashcards
What is classed as sleep restriction?
<8 hours
What gland secretes melatonin? What is it stimulated by?
pineal gland
stimulated by darkness
Which type of sleep has normal breathing?
NREM (non-rapid eye movement)
Describe muscles and breathing in REM sleep
muscles atonic except diaphragm
breathing erratic
sleep apnoea exaggerated in REM sleep
List 4 types of sleep disordered breathing
obstructive sleep apnoea (OSA)
central sleep apnoea
mixed obstructive/central sleep apnoea
obesity hypoventilation syndrome (OHS)
Pathophysiology of obstructive sleep apnoea
lack of tone in pharyngeal dilator muscles (genioglossus)
- can block lumen of airway
History/clinical presentation of obstructive sleep apnoea
snoring
witnessed apnoea
excessive daytime sleepiness (EDS)
nocturia
unrefreshed sleep
morning headaches (disappear as day goes on)
What is it important to ask about in history with obstructive sleep apnoea?
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)
Describe a scale to quantify sleepiness
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
Features to look for on examination when suspecting obstructive sleep apnoea
obesity (BMI>30kg/m2)
upper airways + enlarged tonsils
acromegaly, hypothyroidism, Cushing’s syndrome
micrognathia (small mandible)
retrognathia (receding mandible)
Define apnoea
cessation of breathing for >10 seconds (usually >4% SpO2 desaturation)
Define hypopnoea
decrease in airflow (nasal flow) by 50% or more (may not cause O2 desaturation)
What is a normal apnoea hypopnoea index?
<5 episodes/hour of recorded sleep
Describe apnoea hypopnoea index (AHI) interpretation
5-15 = mild OSA
15-30 = moderate OSA
>30 = severe OSA
What is considered a significant O2 desaturation in a sleep study?
> 4% desaturation
What is OSA Syndrome (OSAS)?
abnormal sleep study and excessive day time sleepiness = OSAS
abnormal sleep study + no excessive day time sleepiness = OSA
What variables should be monitored in a sleep study?
SpO2
HR
body position
snoring
apnoeas/hypopnoeas
Treatment of obstructive sleep apnoea
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
How does OSA affect driving?
have to declare diagnosis to DVLA
CPAP compliance >4 hours/night
HGV/public transport drivers = must inform employers and do occupational health assessment
What causes obesity hypoventilation syndrome?
morbid obesity (BMI>35kg/m2)
What do tests show in obesity hypoventilation syndrome?
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)
Obesity hypoventilation syndrome treatment
weight loss
non-invasive ventilation
Which lung diseases are often co-existent with obstructive sleep apnoea?
asthma (moderate/severe)
COPD/emphysema
Consequences of systemic hypoventilation
systemic hypertension
AF
MI/CVA
Pulmonary arterial hypertension
