OSA (obstructive sleep apnoea) Flashcards
What is sleep apnoea?
Episodic partial / complete obstruction of upper airways during sleep
Define
- Apnoea
- Hypopnoea
- Hyperpnoea
- complete airway obstruction lasting 10+ seconds
- Reduction in RR/depth of breathing (>50% reduced ventilation)
- Increased RR/depth of breathing
Types of sleep apnoea
- Obstructive = airflow obstruction (reduced/no airflow despite resp. effort)
- Central = reduced drive to breath (no airflow – no resp. effort)
- Mixed = both
Mechanisms of sleep apnoea
- Anatomical obstruction due to increased mass of pharyngeal tonsils/tongue/adenoids, maxillomandibular abnormalities, obesity (airway compression) –> reduced pharyngeal inlet
- Neuromuscular dysfunction
Normal Δ breathing during sleep
- Reduced tidal volume
- Higher PaCO2
- relaxation of pharyngeal muscles (+ glossopharyngeus which extends tongue to prevent airway obstruction)
Pathophysiology of an apnoeas episode → physiological consequences
Reduced drive to breathe during sleep + narrowed upper airways
- -> partial / complete airway obstruction (esp. during inspiration w. loss of positive pressure)
- -> reduced ventialation
- -> hypoxia + hypercapnoea
- -> detected by chemoreceptors
- -> SNS stimulation –> arousal -
- > normal breathing (cycle repeats)
Key RF for OSA (9)
- obesity
- age
- male (or postmenopausal female)
- CVD (HTN, etc…)
- FHx
- Chronic snoring
- Large neck circumference
- anatomical abnormalities (maxillomandibular, tonsils, adenoids, tongue)
- Metabolic disorders (T2DM, PCOS, hypothyroidism), Down’s syndrome
Other RFs for OSA (4)
Smoking
Alcohol
Nasal obstruction
Sex hormone levels (changes ass. w. age)
AIH classification of sleep apnea
15+ episodes /h
5+ if additional symptoms / co-morbidities
Clinical Px
- Symptoms
- Cx
- Co-morbidities
Important to get a collateral Hx from partner
- morning headaches
- night time gasping
- excessive daytime somnolence
- restless sleep / insomnia
- loud snoring
- dry mouth
- night sweats
- heartburn/dyspepsia (laryngospasm)
- reduced libido / erectile dysfunction
- depression / mood
- cognitive impairment
- MVAs
- CVD
- nocturia
- those listed above
- CVD
- GORD
- Hx tooth extraction due to overcrowding / difficulty intubating for anaesthesia
Ix
- Polysomongram
- 15+ episodes a night (5+ in some cases)
- multi-modal monitoring during a full-night sleep study (EEG, EOG, ECG, capnography, oesphageal manometry, pulse oxymetry)
- most accepted test - Portable multichannel sleep test
- fewer parameters
- not done routinely - avoid if possible - Awake fibre optic endoscopy
- done to rule out nasal/pharyngeal/laryngeal masses
Possible Cx (7)
- cognitive impairment
- CVD (e.g. pulmonary HTN, HTN)
- depression
- MVAs
- type II resp. failure
- impaired glucose metabolism
- increased mortality
What is OSA an independent RF for?
HTN
Rx
- Weight reduction
- smoking cessation, alcohol reduction
- change sleep behaviours (sleep on side, tongue/mandibular splint…)
- CPAP
- Surgery (to repair anatomical defect)
- Medication for somnolence (e.g. medafinil)
Screening
Screening (e.g. questionnaire) recommended for at-risk populations
- commercial drivers
- operators of heavy machinery
- obesity
- Other populations at risk from diurnal sleepiness