Respiratory - Obstructive Sleep Apnoea Flashcards
What is obstructive sleep apnoea?
Collapse of the pharyngeal airway during sleep, causing apnoea episodes during sleep where the person will stop breathing for a few minutes.
What are the risk factors for obstructive sleep apnoea?
- male sex
- obesity
- smoking
- alcohol
What is the pathophysiology of obstructive sleep apnoea?
Upper airway patency relies on pharyngeal dilator muscle activity, however all muscles relax during sleep.
Excessive narrowing can be due to:
- pre-existing small pharyngeal size during awake state, that undergoes normal degree of muscle relaxation during sleep causing critical narrowing
- excessive narrowing occurring during relaxation during sleep
What are some causes of pre-existing small pharyngeal size?
- fatty infiltration of pharyngeal tissues
- large tonsils
- craniofacial abnormalities
What are some causes of excessive narrowing of the airway during sleep?
- obesity (enhance residual muscle dilator action)
- neuromuscular disease with pharyngeal involvement (e.g. stroke, MND)
- muscle relaxants (e.g. sedatives, alcohol)
- increasing age
What are the features of obstructive sleep apnoea?
- apnoea episodes during sleep
- snoring
- morning headache
- waking up unrefreshed from sleep
- daytime sleepiness
- concentration problems
- reduced oxygen saturation during sleep
What is the Epworth sleepiness scale?
Used to assess symptoms of sleepiness associated with obstructive sleep apnoea.
TOM TIP: If interviewing someone that you suspect has obstructive sleep apnoea ask about their daytime sleepiness and their occupation. Daytime sleepiness is a key feature that should make you suspect obstructive sleep apnoea. Patients that need to be fully alert for work, for example heavy goods vehicle operators, require urgent referral and may need amended work duties whilst awaiting assessment and treatment.
How is obstructive sleep apnoea investigated?
Referral to ENT specialist or specialist sleep clinic, where sleep studies can be performed.
This involves the patient sleeping in a laboratory whilst staff monitor their oxygen saturations, heart rate, respiratory rate and breathing to establish any apnoea episodes and the extent of their snoring.
How is obstructive sleep apnoea conservatively managed?
- weight loss
- avoid evening alcohol intake
- sleep decubitus rather than supine
How is obstructive sleep apnoea definitively managed?
- continuous positive airway pressure (CPAP)
- surgery (surgical reconstruction of soft palate and jaw)
Most common surgical procedure is a uvulopalatopharyngoplasty (UPPP)
What is non-invasive ventilation?
An alternative to full intubation to support the lungs in respiratory failure due to obstructive disease. It is much less invasive than intubation.
What are the options for non-invasive ventilation?
- BiPAP
- CPAP
What is BiPAP?
Bilevel positive airway pressure - a type of non-invasive ventilation involving a cycle of high and low pressure to correspond to the patients inspiration (IPAP; inspiratory positive airway pressure) and expiration (EPAP; expiratory positive airway pressure).
BiPAP is used where there is type 2 respiratory failure, typically due to COPD.
What is the criteria for initiating BiPAP?
Respiratory acidosis (pH < 7.35 AND PaCO2 > 6) despite adequate medical management.
What are the main contraindications for BiPAP?
- untreated pneumothorax
- structural abnormality affecting the face, airway or GI tract
Patients should have a CXR prior to NIV to exclude pneumothorax.
