Sleep disorders Flashcards
OSA and OHS - people typically wake up with …
Headache due to high CO2 levels
Pathophysiology of OHS
1) Leptin resistance (leptin is a powerful ventilatory stimulus)
2) Increased mechanical load (extrathoracic fat) on lungs
3) Chronic renal compensation by increasing serum bicarb –> reduce acidaemia –> normal pH
= Blunted ventilatory response –> persistent high CO2
Symptoms of OSA/OHS
- SOBOE
- Headache - specifically morning headaches may be secondary to retained CO2
- Snoring
- Poor quality sleep
- Mental cloudiness, fatigue
What screening tools are available for OSA?
STOP BANG
- Are you tired?
- Good sensitivity and NPV. Not specific.
Epworth sleepiness scale
- Are you likely to knock off?
- Not sensitive or specific to OSA. Weak correlation with all measurements of OSA severity.
FOS-Q
- Can be used to track improvements in QOL after treatment
Define OHS
TRIAD of
Obesity (BMI ≥30) +
Daytime hypercapnia (ABG with pCO2 ≥45mmHg) +
Sleep disordered breathing
Must exclude other causes of hypoventilation
85% have OSA
Things to look for on exam OHS
Central obesity (increased waist to hip ratio, increased neck circumference)
Mallampati score 3 or 4
Signs of cor pulmonale (lower extremity oedema, clubbing)
Daytime oxygen saturation - low-mid 90s
Can OHS and COPD coexist?
Yes
But you technically can’t call it OHS because its a diagnosis of exclusion
Define OSA
Apnoeas (stop breathing for ≥10 seconds) or hypopneas (decreased airflow ≥10 seconds) associated with desaturation or arousal
OSA is at least 5 episodes of apnoea or hypopneas per hour of sleep + symptoms
5-15 episodes = mild
15-30 episodes = moderate
30+ episodes = severe
Alternatively, its ≥15 episodes +/- symptoms
What is the proportion of OHS that has OSA?
70-90%
The greater the AHI (in OSA) the greater the risk of OHS
Pathophysiology of central sleep apnoea?
Overly brisk ventilatory response (overbreathe) to small changes in CO2 –> breathing exceeds what’s necessary
E.g. cheyne-stokes breathing in HF, or periodic breathing in opioid use or high altitude
How is central sleep apnoea diagnosed?
Only on sleep study
Investigations to get in OHS
1) ABG pCO2 >45
2)
Serum bicarbonate <27 = unlikely to have hypercapnia in low-to-moderate OHS patients
3) RFTs
- Rule out obstructive lung disease (if present, can be cause of hypoventilation)
- Rule out neuromuscular disease - increased FRC, ERV and RV
- Severe obesity/OHS - extrinsic restriction with mildly reduced TLC, preserved DLCO, low FRC and very low ERV (fat pushing on diaphragm so you can’t breathe out as easily)
4) CXR
5) TTE
- ?Pulmonary HTN
6) In Lab Sleep study
- To evaluate OHS and titrate PAP treatment +/- oxygen
- Cf OSA get usually get away with home sleep study
7) Polycythaemia on FBC
Treatment for severe OSA (>30 AHI) that is also associated with OHS
CPAP is equal to biPAP in terms of CO2 reduction, improvement in hypoxemia and QOL overtime
When do you give oxygen monotherapy to OHS?
Never - may worsen hypercapnia
Can give it together with PAP therapy if needed
What’s the difference between APAP, CPAP and biPAP?
APAP is auto-titrating PAP - a range of pressures can be delivered. Machine detects whether there is snoring or flow limiting then adjusts the pressure accordingly
CPAP is continuous positive airway pressure = airway stent (increases pressure at mouth and nose to keep the airway open)
BiPAP
- Type of NIV
- Expiratory pressure (ePAP) like CPAP
- Inspiratory pressure (iPAP) is higher than expiratory pressure; initiated when patient attempts to breathe in
- ePAP keeps the airway open, while the iPAP kicks in when the patient inhales to assist with work of breathing/increase tidal volume
- The difference between iPAP and ePAP is what’s driving the ventilation and decreasing the WOB
- Synchronised: every time you take a breath, the breath is made bigger
- Time-synchronised: if you don’t breathe at all like in central sleep apnoea, its going to give you a breath
How do you monitor progress of OSA/OHS on treatment?
Monitor ABG (bicarb) and daytime oxygenation and symptoms
What’s a typical BIPAP setting for OHS?
Much higher delta pressure 8-15mmHg needed
Might have a lower ePAP but a bigger difference between iPAP and ePAP
Management of OHS
Lose weight
Avoid BZDs
BIPAP
- CPAP usually first choice if significant co-existing OSA (monitor over 2-3/12 with sx, ABG)
- If minimal/mild OSA but significant OHS/respiratory failure, NIV may be first choice
- If presenting with acute on chronic T2RF, NIV
Patients admitted with concern for OHS that have not yet had the diagnosis confirmed should be managed how?
NIV +/- oxygen (goal is to control the acidosis)
Discharge them on NIV/bipap while they wait for sleep study (within 3 months) –> titrate PAP accordingly after sleep study
When acidosis normalises, may be able to downgrade to CPAP
If patients have central sleep apnoea on sleep study, how do you manage them?
BiPAP ST (time-synchronised) - likely lifelong as it is unlikely to resolve Decrease opioids
What are the goals of treatment for OHS?
1) Improvement/normalisation of pCO2
2) Improvement/normalisation of pH
3) Improvement/normalisation of bicarb (often elevated before therapy)
What’s the delta pressure?
The difference between iPAP and ePAP on biPAP/NIV
Are men or women more likely to have OHS and OSA?
Men > women OSA
Men = women OHS (women may be more likely to present later in their course, and thus present with more advanced disease/need to be hospitalised
Which part of a sleep study report should you look at in OSA?
AHI
Oxygen desaturation index (ODI) - Number of times oxygen desaturation falls by >4% in one hour of sleep
T90 - time spent below SpO2 90%
Data suggests that it is not the number of hypopneas/apneas but rather the time spent hypoxemic (T90) that most strongly correlates with outcomes such as CV disease, malignancy
Why use home study instead of IP lab study in OSA?
Data suggests data from home sleep study is non-inferior to traditional lab-run polysomnography
Sleep better at home
Much better access
Less expensive
People tend to adhere to CPAP better after home sleep study ?unsure why
Do all severities of OSA require CPAP?
Mild OSA may not require treatment unless they have excessive daytime sleepiness
Asymptomatic patients with mild OSA who are started on CPAP and have bad experiences may be much more difficult to reach in the future should their disease worsen
Causes of OSA
Majority of people are heavy and have metabolic syndrome
But you don’t need to be heavy to have OSA
Other reasons: hypothyroidism, receding chin, Down’s syndrome or Treacher-Collins (pharynx is narrowed), genetic predisposition, post menopausal women (tissue laxity including palate), children with large tonsils
Benefits of CPAP in OSA
Improves sleepiness, depression, cognitive function, QOL
Reduces BP
Reduces MVA
No RCT evidence that it decreases CV mortality (despite lots of observational data)
Other than CPAP, what are interventions are effective in OSA?
Weight loss!!
Reduce ETOH
Avoid opioids, BZD (controversial)
Positional therapy - highly effective for those with only positional OSA (up to 25%)
Oral appliance (mouth guards fit by dentist) - moderate effectiveness, $$$
Surgery may be a rescue option in those who don’t tolerate CPAP or oral appliance
Hypoglossal nerve stimulation
Tonsillectomy
Bariatric surgery
Radical maxillofacial/ENT surgery - “last resort”, variable efficacy
When would you do an in-lab polysomnography rather than home sleep study?
Not suitable for complex sleep pathology
CI: neuromuscular weakness or hypoventilation, intellectual impairment, seizures, parasomnias (abnormal behaviours during sleep)
Sleep is divided into NREM and REM sleep. Explain the difference.
NREM
- Makes up 80% of sleep
- Divided into N1/N2/N3 - progressively ‘deeper’ sleep. N3 (slow wave sleep) mostly occurs in the first half of the night.
REM
- Makes up 20% of sleep
- Characterised by atonia (EMG), tonic/phasic eye movements (EOG)
- Predominantly 2nd half of night
Does narcolepsy involve NREM or REM sleep?
REM - intrusion of REM sleep into wakefulness
Define apnoea
Cessation of airflow for ≥10 seconds
Central vs obstructive vs mixed
Define hypopnea
Reduction of airflow by 30% for ≥10 seconds followed by:
- 4% oxygen desaturation
- EEG arousal
Define apnoea-hypopnea index (AHI)
Number of apnoea and hypnoea events per hour
What’s respiratory effort related arousal (RERA)?
Increased respiratory effort for ≥10 seconds associated with EEG arousal BUT don’t meet criteria for hypopnea
What’s respiratory disturbance index (RDI)?
AHI + RERAs
What is the definition of sleep hypoventilation?
Abnormal increase in PaCO2 during sleep
E.g. neuromuscular disorders, OHS
Transcutaneous CO2 increases to >55mmHg for ≥10 minutes
OR
≥10mmHg increase in transcutaneous CO2 to value >50mmHg for ≥10 minutes
What is the definition of Cheyne Stokes respiration?
Central apnoeas/hypopneas alternating with a respiratory phase (crescendo-decrescendo pattern of flow)
Long cycle length >45 seconds
In what conditions do you get Cheyne strokes respiration?
CCF
Post stroke
Terminal phase
Pathophysiology of OSA
Narrow collapsible upper airway
What questions are listed in STOP BANG?
S - snoring T - tiredness O - observed apnoea P - blood pressure B - BMI A - age N - neck circumference G - gender
- Are you tired?
- ≥3 intermediate risk
- ≥5 high risk
What score in epworth sleepiness score is likely pathological?
≥10 is likely pathological
Risk factors for OSA
Male Older age BMI - strongest risk factor Increased neck circumference Snoring Witnessed apnoeas Menopause Craniofacial abnormalities e.g. short mandible, tonsilar hypertrophy
Complications of untreated OSA
MVA Cardiovascular disease - HTN, CAD, CCF, AF CVA Pulmonary HTN Diabetes, poor BSL control Mortality
What are the 2 kinds of PAPs that can be used in OSA?
APAP
CPAP
Complicated of untreated OHS
CV disease - HTN, pulmonary HTN, RHF
Increased mortality
What types of sleep disordered breathing can you get in HF?
Cheyne strokes respiration
OSA
Rx sleep disordered breathing in HF
Optimise HF therapy
Treatment is controversial
Treatment options include CPAP, O2, NIV
Adaptive servo ventilation is CI in those with EF <45%
Pathophysiology of narcolepsy
Autoimmune destruction of hypothalamic neurons that produce hypocretin (orexin) that keeps up awake
What’s cateplexy?
Sudden + transient muscle weakness associated with conscious awareness usually triggered by emotions e.g. laughing
Definition of narcolepsy
Excessive daytime sleepiness for at least 3 months + positive mean sleep latency test +/- cataplexy
Rx narcolepsy
Dexamphetamine or armodafinil
SSRI/SNRI for cataplexy
How to diagnose narcolepsy?
Mean sleep latency test (MSLT)
1) PSG to ensure at least 6 hour sleep before MSLT
2) MSLT during the day in sleep lab
- x5 20 minute naps set 2 hours apart
- <8 minutes associated with 2 sleep onset REM periods = highly suggestive of narcolepsy
Most common cause of restless leg syndrome
Iron deficiency
What is the difference between restless leg syndrome and periodic limb movement disorder?
PLMD occurs during sleep and people are unaware of it (seen in sleep study), while RLS occurs when a person is awake and asleep.
80% of people with RLS also have PLMS, but not the reverse.
What is parasomnia?
Abnormal behaviours during sleep
E.g. REM sleep disorder, occurs in Parkinson’s
Is RLS related to genetics?
Yes
Autosomal dominant
Phenotypes of RLS
Primary (early onset)
Younger, slowly progressive, FHx, idiopathic
Secondary
Iron deficiency, ESKD, pregnancy, medications that block the DA pathway (AD, antihistamine, lithium, D2 receptor blocker)
Pathophysiology RLS
Reduced CNS iron
Iron important for DA synthesis –> reduced CNS DA
Diagnosis RLS
Clinical diagnosis
Iron studies
Pregnancy
Renal function
BUT if you do a sleep study, may see periodic limb movements (non-specific)
Rx RLS
Lack robust evidence
Stop caffeine, nicotine, ETOH
Iron replacement if ferritin <75
1st line: DA agonist (pramipexole or ropinorole)
Side effects: augmentation with time
(paradoxical worsening RLS during the day), impulsive behaviours
1st line: pregabalin/gabapentin
Side effects: suicidal ideation, weight gain, sleepiness
2nd line: opioids, BDZ
Periodic limb movements disorder
RARE. Controversial diagnosis. Diagnosis of exclusion Period limb movements on sleep study Marked sleep disturbance and daytime sleepiness No other sleep disorder
Explain normal sleep
Early part of the night: deep sleep (NREM)
Late part: REM sleep
NREM–>REM–>NREM–REM (x4 cycles)
NREM parasomnia
Undesirable behaviour or phenomenon occurring during NREM sleep
Partial arousal from sleep
Some genetic susceptibility
Can be related to zolpidem, sleep deprivation, emotion stress
Common in children
Happens first part of night
Types NREM parasomnia
Sleep walking
Confusional arousal - sexsomnia
Sleep terrors - wake up, high pitched screaming
Treatment NREM parasomnia
Generally grow out of it
Reverse exacerbating factors
Rx: clonazepam in difficult to treat (no RCT)
REM behaviour disorder (REM parasomnia) associated with
Alpha synucleopathies
PD
DLB
MSA
Within 16 years, 80% of them will develop alpha synucleopathies/neurodegeneration.
REM behaviour disorder diagnosis
REM sleep loss of muscle atonia
+
Abnormal behaviour during REM often as dream enactment behaviour that can cause injury
Diagnosis requires both
EMG
- Sustained muscle activity during REM
REM behaviour disorder Rx
Clonazepam (90% response) +/- melatonin
Safe home environment
Avoid changes in sleep routine
Avoid antidepressants (TCAs, SSRI)
Neuro assessment
Clinical features REM behaviour disorder
30 seconds - 3 minutes
Fighting, violent during REM sleep
M>F
Rapid return to baseline +/- recall (tend to remember it)
What’s narcolepsy?
Don’t have neat NREM–>REM sleep cycle
Its all over the place
Young people get it
Forms of narcolepsy
3 forms
1) NT1 (with cataplexy)
- Well studied
- Low CSF hypocretin (lateral hypothalamus)
- HLA positive 98%
2) NT2 (without cataplexy)
- May improve spontaneously
- Some have normal CSF hypocretin
3) Secondary narcolepsy (rare)
- CNS tumour, brain trauma
What’s cateplexy?
Brought on by emotion
Transient loss of muscle tone - may be subtle like drooping of mouth or slumping to the ground. No LOC.
Possible REM sleep intruding into wakefulness
What’s hypocretin?
Maintains wakefulness
Maintains sleep stages
Symptoms narcolepsy
Daytime sleepiness
Irresistible urge to fall asleep
+/- cataplexy
Go into REM sleep very quickly (normally it takes 60-90 minutes)
Pathophysiology narcolepsy
Genetic predisposition and environmental factors (e.g. pandemic H1N1 in Finland)
Diagnosis narcolepsy
Sleep study - exclude other sleep disorders
MSLT - how long it takes for you to fall asleep during the day (<8 minutes)
How soon before ongoing into REM sleep?
Consider CSF hypocretin
Treatment narcolepsy
Schedule naps
Modafinil or armodafinil
Amphetamines
Cataplexy
Sodium oxybate (similar to date rape drug so very hard to access) - only drug that improves sleep consolidation
Antidepressants
Insomnia management
CBT works just as well as pharmacotherapy
However access to psychologist is difficult
BZD have significant side effects and safety concerns
Most other alternatives have not been systemically evaluated for efficacy or safety
Types of sleep study
Level 1 - in hospital, monitored
- Do this in patients with hypoventilation
Level 2 - at home, similar to level 1
- Similar outcomes to level 1
- Helpful in selected patients
Level 3
- Measures oximetry, airflow
Level 4
- Simple screening
- Oximetry only
2 patterns of presentation OHS
1) acute on chronic respiratory failure
- Often have RHF, pulmonary HTN
- Need BIPAP in ICU
2) Chronic (stable)
- Part of routine assessment for OSA
- May get away from simple CPAP
What’s central sleep apnoea?
Cessation of airflow
No effort to breathe
Causes of central sleep apnoea
CCF (50%) Stroke Drugs e.g. opioids Neuromuscular disorders CNS disorder e.g. MS, Arnold-Chiari Iatrogenic - when you over ventilate people (blow off CO2 too much)
Treatment central sleep apnoea
Treat underlying cause
Consider
Oxygen
Adaptive seroventilation (controversial)
What’s nocturnal hypoventilation syndrome?
Hypoventilation at night, most severe during REM
Increased PaCO2 (reduced PaO2)
Reduced or absent effort
Prone to RHF, pulmonary HTN, respiratory arrest (especially if they have pneumonia on top of that)
Causes nocturnal hypoventilation syndrome
Nocturnal hypoventilation syndrome is always caused by something else!!
OHS
Severe COPD
Neuromuscular disease e.g. severe scoliosis
CNS disorders
Congenital central hypoventilation syndrome (No PHOX 2B gene)
Diagnosis nocturnal hypoventilation syndrome
Severe desaturation, sustained, particularly in REM sleep
Rise in PaCO2
Stable hypercapnic COPD PaCO2 >52, not acidotic
Without overlay OSA, HF, opioids
Without exacerbation
Management
Long-term NIV
Better outcomes
