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Why do REM sleep changes affect people with respiratory disorders and not normal people?
- Resp patients are dependent on ACCESSORY MUSCLE activity
- Resp pts already hypoxic when awake!
Which patients are most susceptible to sleep related oxygen desaturation? Give egs
- Type 2 resp failure: high CO2
- eg COPD, NMD eg muscular dystrophy, motor neuron diseae, kyphoscoliosis
how is oxygen desaturation during sleep treated in patients with resp disease?
- 1. treat underlying disease – bronchodilators in COPD
- 2. avoid aggravating factors: alcohol/sedatives
- 3. supplement oxygen at night but may lead to hypoventilation and CO2 retention
- 4. long term ventilatory support: NIPPV: tight mask over nose, connected to a specifically designed ventilating machine
how is response to NIPPV monitored?
- Improve quality of sleep and nocturnal symptoms
- Improves daytime symptoms
- Improve gas exchange – see on ABG
What collapses during OSA and what is the sequence of events in OSA?
- Pharyngeal collapse upper airway occludion during sleep hypopnoea/apnoea
- Reduced airflow – provoke arousals and sleep fragmentation daytime sleepiness
What factors contribute to narrowing of pharyngeal airway?
- Fat deposition in neck from obesity
- Bone morphology eg micrognathia = undersized jaw
- Soft tissue deposition eg hypothyroidism, acromegaly
- Enlarged tonsils or adenoids in children
What factors contibute to reduced pharyngeal dilator muscle tone?
- REM sleep
What factors contibute to increased upper airway resistance causing greater inspiratory effort and so sucking in the pharyngeal airway?
- Nasal polyps
- Deviated nasal septum
- Large tonsils
- Large adenoids
Why do patients with OSA get fluctuations in pulse and BP during sleep?
Apnoea is followed by arousal – burst of sympathetic nerve activity and release of catecholamines changes in BP and HR
What are the daytime symptoms of OSA?
- Sleepiness: dangerous
- Poor concentration
- Loss of libido
- Morning headaches
- Unrefreshing sleep
Which score is used to assess excessive sleepiness?
- Epworth sleepiness score
- If get 10+ need further evaluation for sleep disorder
What should drivers with OSA be advised?
- Notify DVLA
- Avoid driving until sleepiness controlled by treatment
What are the nighttime symptoms of OSA?
- Bed partner reports
- Loud snoring
- Restless sleep
What Qs need to be asked about aggravation of OSA?
What features are seen on examination of OSA?
- Increaesd neck circumference
- Reduced pharyngeal caliber: Micrognathia (undersized jaw), large tonsils
- Nasal obstruction: polyps, deviated septum
What are CVS complications of OSA? Why? (general principle)
- Structural cardiac changes
- Heart failure
- Cause: hypoxaemia, changes in BP, sympathetic NS activation
How are vessels damaged in OSA and what evokes an inflam response?
Recurrent apnoea and arousal leads to deoxygenation and reoxygenation increase formation of reactive oxygen species damage vasculature and prove inflam
What is the definitive assessment of OSA and how is it done?
- Polysomnography: record signals relating to oxygenation, airflow, chest wall movement and stage of sleep
- EEG: records stage of sleep
- EOG: detect REM
- Thermistor: detects airflow at nose and mouth
- Ribcage and abdo movements recorded
- Oximetry: O2 desaturation
- ECG: heart rate
- Combine with video of pt during sleep
How is OSA diagnosed according to apnoea/hypopnoea, O2 sats and clinical?
- More than 15 apnoea or hypopnoeas per hour
- Each lasting > 10s (apnoea/hypopnoea index > 15)
- Oxygen desaturation > 4%
- Clinical: daytime sleepiness
What is the initial/general treatment of OSA?
- Weight loss: diet advice, exercise
- Remove aggravating factors: alcohol, sedatives before sleep
- Discourage sleeping on the back as snoring and OSAS more common when lie on back
- Treat cause: eg tonsillectomy, excise nasal polyps, correct deviated nasal septum, treat COPD
What is the standard first choice treatment for OSA? How does it act?
- Nasal CPAP – tight fitting nasal mask
- MOA: splint pharyngeal airway open
- CPAP nurse to overcome difficulties
What is the pharmacological treatment of OSA?
- Modafanil: stimulant alerting drug
- Protriptylline: non sedative anti depressant which redues time spent in REM sleep
- None effective
What are the surgical treatment options for OSA?
- Relieve pharyngeal obstruction
- Uvulopalatopharyngoplasty (UPPP): excise redundant tissue of soft palate, uvula and pharyngeal walls increase calibre of pharyngeal airway
- Tracheostomy – last resort
What is the treatment of OSA if bone abnormality eg micrognathia?
- Mandibular advancement – surgical or device
- Device: worn over teeth and increases forward movement of mandible
What are the complications of OSA?
- Pulmonary hypertension
- Type 2 respiratory failure
- Complications during general anaesthesia
What is central sleep apnoea? What is primary?
- Lack of respiratory muscle activity
- Primary: due to instability of respiratory drive due to damage to respiratory centres by brainstem infarcts
What is Cheyne-Stokes respiration?
Pattern or irregular breathing with periods of apnoea followed by hyperventilation
Who gets Cheyne-Stokes respiration? Why?
- Heart failure patients
- Because carotid body is slow in responding to changes in ventilation because of prolonged circulation time