Respiratory: Obstructive Sleep Apnoea Flashcards
Outline the pathophysiology of OSA
Upper airway narrowing, provoked by sleep, causing sufficient sleep fragmentation to result in significant daytime symptoms
Causing of small pharyngeal size
- fatty infiltration, large tonsils
Causes of excessive narrowing with relaxation
- obesity, muscle relaxants, neuromuscular disease (stroke, MND)
Most pts are male and obese
Severe = repetitive upper airway collapse, arousal required to re-activate pharyngeal dilators
What is the Epworth Sleepiness Scale?
Points for following: 0= would never doze, 1 = slight chance, 2 = moderate chance, 3 = high chance
- Sitting + reading
- Watching TV
- Sitting in a public place
- Passenger in a car for an hour
- Lying down to rest in the afternoon
- Sitting + talking
- Sitting quietly after lunch without alcohol
- In a car, while stopped in traffic
How is OSA diagnosed?
Sleep study types =
Overnight oximetry alone
Limited sleep study – oximetry, snoring, body movement, heart rate, oronasal flow, chest/abdominal movements, leg movements – usual study of choice
Full polysomnography – limited study plus EEG (electroencephalogram), EMG (electromyogram)
Outline the management of OSA
Conservative = Weight loss, sleep decubitus rather than supine, avoid/reduce evening alcohol intake
Snores + mild OSA = Mandibular advancement devices, consider pharyngeal surgery as last resort
Significant OSA = Nasal CPAP, consider gastroplasty/bypass, and rarely tracheostomy
Severe OSA + CO2 retention = May require a period of NIV prior to CPAP if acidotic, but compensated CO2 may reverse with CPAP alone
What should pt with OSA be advised about driving?
Tell all patients with OSA to NOT drive while sleepy; stop and have a nap.
On diagnosis the patient should notify the DVLA
The doctor can advise drivers to stop altogether (e.g. HGV drivers)
Compare CPAP vs BIPAP (NIV)
CPAP supplies constant positive pressure during inspiration and expiration and is therefore not a form of ventilatory support. It can be used to treat OSA and helps oxygenation in some patients with acute respiratory failure, e.g. pulmonary oedema
Non-invasive ventilation (NIV) does provide ventilatory support with two levels of positive pressure (bilevel) – pressure support provided between selected inspiratory and expiratory positive pressures (IPAP + EPAP). They can also be set up with back up rates so the machine operates when the respiratory rate drops below a fixed level.
