Intro Flashcards
What are the components of the two process model of sleep?
- Circadian rhythm (body clock)
24 hour cycle, rhythmic, intrinsic, generated from SCN - Homeostatic drive (sleep pressure)
dependent on previous sleep quality and time awake
What is a Zeitberger?
An environmental agent/event that provides the stimulus for a biological clock
Which hormone causes sleepiness?
Melatonin
How long does a normal sleep cycle last?
Around 90 mins
What are the stages of sleep?
- Stage 1 sleep
- Stage 2 sleep
- Stage 3 sleep (slow-wave/deep) sleep
- REM sleep
How are sleep studies performed?
Polysomnography (+ECG)
What is a hypnogram?
A graphical representation of the stages of sleep as a function of time
What is stertor?
Noisy breathing during sleep, usually caused by obstruction at the level of the oral or nasal cavities or oropharynx or nasopharynx
- Typically low-pitched
What is stridor?
High pitched noise while sleeping, usually associated with obstruction at the level of the larynx
Where is melatonin produced?
The pineal gland
What is a normal Epworth sleepiness scale score?
If the patient has an Epworth sleepiness score of 10 then they should consider seeking medical advice
How many apnoea hypopnea events per hour is classed as normal?
< 5 events
What is the equation used for lung function predicted values and the age ranges?
GLI - available for over 3 year olds but only up to 80 year olds for the box
What do you measure with sleep pulse oximetry?
ODI (oxygen desaturation index), Total number of dips (<3), time below 90%, Nadir value
What is responsible for circadian rhythm and where is it located?
The suprachiasmatic nucleus (SCN) - located near cerebral cortex at the bottom of the brain
- in the anterior hypothalamus
Are circadian rhythm and homeostatic drive linear?
Circadian rhythm - is not (dips at 3pm)
Homeostatic drive is
Where is melatonin produced?
Pineal gland
How can you determine which stage of sleep patients are in?
Polysomnography - each stage has different waveforms
Which stage of sleep is deep sleep?
Stage 3 (delta sleep) - big delta waves seen
What waves are seen in REM sleep?
Low-voltage random, Saw-tooth waves
What polysomnography waves are seen when awake?
Low-voltage, random waves
What polysomnography waves are seen when drowsy?
Alpha waves - low voltage spikes
What polysomnography waves are seen when in stage 1 sleep?
Theta waves - short stubby waves
What polysomnography waves are seen when in stage 2 sleep?
Sleep spindles - small spikes
K complexes - massive rare spike
What polysomnography waves are seen when in stage 3 sleep?
Delta waves - large common spikes
In which sleep stage is there hypotonia of skeletal muscles and only the diaphragm working?
REM sleep - ensures we don’t act out our dreams
What is a hypnogram?
Graphical representation of the stages and cycles of sleep
How much time each night is spent in stage 1 sleep?
Very little (5 - 10 mins or so) = 2 - 5% of night
What percentage of the night is spent in NREM sleep?
70 - 80%
How do the length of sleep cycles vary throughout the night?
First cycle is shorter 70 - 100 mins
Subsequent cycles are 90 - 120 mins
How long does a stage 2 sleep cycle last and what percent of total sleep time does it make up?
Cycle = 10 - 25 mins
Total = 45 - 55%
What are stage 3 sleep also called?
Slow-wave sleep
How long does slow wave sleep cycle last and what percent of total sleep time does it make up?
Cycle = 20 - 40 mins
Total = 13 - 25%
What happens to BP in sleep?
BP can be up to 20% lower - however there are spikes with K complexes, arousals and body movements
What happens to blood flow in sleep?
NREM - blood flow and metabolism is reduced
REM is similar to wakefulness however flow in certain brain areas is increased
What is stage 3 sleep dependent on?
Adenosine - the reason stage 3 sleep time gets shorter throughout the night
What happens to length of REM sleep throughout the night?
It gets longer - why we dream later throughout the night
What can a morning headache be indicative of?
Carbon dioxide retention
What is the Mallampati score?
Grading of soft palate obstruction
What percentage of males and females have OSA? (Switzerland study)
50% of men and 23% of females
What is the difference between OSA and OSAHS?
OSA is a precursor and often not symptomatic
What is a normal apnoea hypopnoea index range?
< 5 events per hour
Is ENT surgery recommended for OSA?
No, however tonsillectomy might be
What is hypoglossal nerve stimulation?
Implanted device connected to nerve under tongue
Causes muscle activation to reduce airway collapsibility
- is effective but not available on the NHS
When was CPAP first used?
1980
In addition to improving sleep quality, what else can CPAP improve?
Helps lower daytime sleepiness and blood pressure, vascular function and DCCV in AF patients
What is obesity hypoventilation syndrome?
Combination of obesity (BMI > 30) and daytime hypercapnia
- other causes of impaired ventilation must be excluded
- increased risk of pulmonary hypertension and heart failure
How by what percentage is mortality increased in OHS patients?
Mortality rate of 23% compared with 9% in eucapnic obesity group
What percentage of patients who have OHS also have OSA?
90%
What are some presenting symptoms of OHS?
- Morning headaches
- Significantly obese
- Daytime sleepiness
- May have oedema
- May have unexplained polycythemia (blood cancer)
What is TS90 and what values are commonly present in OHS patients?
Time Spend below O2 saturation of 90%
- OHS patients will often have > 30% of night below 90%
What are the two main causes of arterial blood gas changes?
Metabolic and respiratory
What is a normal venous bicarbonate level?
23 mEq/L
How does non-invasive ventilation compare with CPAP?
NIV provides actual ventilation, whereas CPAP only opens airway
No significant difference in performance
When is NIV used over CPAP?
If only hypoxia and no cessation in breathing
What are the treatments for central sleep apnoea?
Treat the underlying cause
- adaptive servo-ventilation (sort of a mix of NIV + CPAP) can also be used - but not with patients with HF
What is overlap syndrome?
OSA and COPD
When are OSA patients reviewed for driving again?
4 weeks post-CPAP
What comprises the ascending arousal system?
The hypothalamus, brainstem and basal forebrain
What is the VLPO? And what is its function?
The ventrolateral preoptic nuclei - a cluster of neurons in the anterior hypothalamus
- it promotes sleep (along with melatonin + others)
When is the VLPO active?
During sleep - particularly REM
What is orexin/hypocretin?
A neuropeptide - responsible for stabilising the flip-flop switch of sleep
Which neuropeptide is missing in narcolepsy?
Orexin / hypocretin
Which neurotransmitters promote REM sleep?
Acetyle choline, GABA, dopamine, glycine
Which neurotransmitters promote NREM sleep?
GABA and galanin
Which neurotransmitters promote wakefulness?
Dopamine, neuradrenaline, histamine, hypocretin/orexin, acetylcholine, glutamate
What is caffeine’s half life?
3.5 - 7 hours
How does caffeine cause wakefulness?
Is an adenosine receptor antagonist
- leads to increased brain dopamine
How does nicotine impact caffeine?
It reduces half-life by 30 - 50%
What is sleep paralysis?
Abrupt wakefulness before muscle tone returns, accompanied by dream like hallucinations
At what age do your sleep cycles remain the same length for the rest of life?
8 years old
Are sleep cycles longer or shorter in children?
Shorter than adults (50 - 60 mins)
How many REM cycles do you have per night?
4 - 5
What generates circadian rhythm?
Retinal ganglion cells which communicate with the SCN to provide the sleep body clock
How is circadian rhythm synchronised?
Zietbergers (external cues)
What is the most important Zietberger?
Light
How many hours of sleep per day do babies require?
14 - 17 hours
How many hours of sleep per day do teenagers require?
8 - 10 hours
At what age does amount of slow wave sleep reduce and what does this signify?
Late 20s and may signify the start of brain function decline
What is the two-process model of learning during sleep?
Hippocampus encodes - repeatedly activated
Neocortex - strengthens and re-organises
What sleep activity increases when encoding and learning new information?
Increased slow wave activity
How does sleep impact synaptic plasticity?
There is a 40% downscaling of synaptic networks when we sleep
- erase synapses
What is the most common sleep disorder excluding OSA?
Insomnia
What values of the Epworth sleepiness scale indicate: insomnia, normal, excessive sleepiness?
Insomnia = 0 - 2
Normal = 2 - 7
Excessive sleepiness > 10
What is the STOP-BANG questionnaire?
Used to screen for OSA:
Snoring
Tiredness
Observed events
Pressure (blood pressure)
BMI
Age
Neck size
Gender
What factors are associated with central apnoea?
HF patients and patients on prescription painkillers (e.g. opioids)
What is narcolepsy?
A sleep switch problem - prevents person choosing when to sleep
What is cataplexy?
Sudden muscular weakness, triggered by sudden changes in emotions e.g. laughter, anger, surprise
What can cause canine narcolepsy?
Orexin / hypocretin 2 receptor defects
What is thought to cause human narcolepsy?
Autoimmune condition due to loss of hypocretinergic neurons in the hypothalamus
What are the criteria for Type 1 narcolepsy?
Excessive daytime sleepiness > 3 months on a daily basis
One or both of:
- cataplexy
- CSF hypocretin < 110 pg/ml
What are the criteria for Type 2 narcolepsy?
Excessive daytime sleepiness > 3 months.
No cataplexy
Normal CSF hypocretin
Not explained by any other disorder
What percentage of narcolepsy patients are Type 1 and Type 2?
70% Type 1
30% Type 2
What are some of the medications for narcolepsy and what are their side effects?
Psychostimulants e.g. Solriamfetol, ritalin
- have side effect of increased BP
What are NREM parasomnias?
Incomplete awakening from NREM sleep
- usually young onset (< 20)
- key is finding out what is interrupting their sleep
What is REM sleep behaviour disorder?
REM consists of short outbursts e.g. dream enactment
- progressive, neurodegenerative disorder
How can you identify REM sleep behaviour disorder on polysomnography?
Can see effort or movement in REM sleep
What are some medications used to treat REM sleep behaviour disorder?
Benzodiazepine (sedative) and melatonin
What comorbidities is REM sleep behaviour disorder associated with?
Neurodegenerative disorders, particularly Parkinson’s
What is the first treatment for restlest legs syndrome?
Lifestyle
What is the first and subsequent medical treatments for restless legs syndrome?
Iron (ferritin) if below 75 then treat
- gabapentin, dopamine agonists
What medications can aggravate restless legs?
Anti-depressants, anti-histamines
Is insomnia disorder more common in males of females?
Females
Should you go to sleep and wake up at the same time?
Don’t have to go to sleep at the same time
But should wake up at the same time
Can sleep walking occur in NREM sleep?
Yes
Can sleep walking occur in REM sleep?
No
What is homeostatic drive to sleep?
Sleep pressure that builds up with time awake
