Sleep medicine Flashcards
Mx of OSA
Management
-
PAP
- CPAP (BPAP if CPAP pressure is too high fr pt, or if level ≥15cmH2O and sleep disturbance cont) -
Lifestyle
Obesity Mx (dietary, bariatric surgery in BMI ≥35) -
Surgery
E.g. Nasal/ oropharyngeal/ tongue surgery, maxillary expansion/ maxillomandibular advancement surgery
- repeat PSG 3m post-op)/ nasal spray
- surgery for pt intolerant of PAP or to improve PAP compliance (help to reduce pressure) -
Sleep position
tennis ball - Maxillomandibular advancement appliance
- Hypothyroid Rx.
-
Pharmacological
Modafinil for daytime sleepiness
intranasal steroid for AR
Interpreting CPAP report
Therapy mode: If Auto (AVAPS), no need to change the pressure. It will change automatically
Pressure: pressure median & 95th percentile
AHI: no need to be <5. Make sure the current value showed improvement from baseline
Leak:
Acceptable:
nasal mask/pillow: 20-45
full face mask: 30-60
Compliance - look at use >4H %
Others:
Redo ESS score - make sure improved compared to pre CPAP
Take note of T2RF. If present before, to do one more ABG to see resolution after CPAP initiation.
Also to consider doing echo pre & post CPAP treatment. If high PASP prior to CPAP, to Ax if it reduces with CPAP
PSG interpretation
NREM & REM alternate in cyclical manner (4-6 cycles), each cycle lasting 90-120mins
Respiratory Disturbance Index (RDI)
= apnea + hypopnea + RERA
- score:
mild 5-15
mod: 15-30
severe: >30
What is central sleep apnea (CSA)
Central sleep apnoea (CSA)
= Sleep disordered breathing with
- decreased airflow
and
- diminished or absent resp effort
together with
- Sx of excessive daytime sleepiness/ frequent nocturnal awakening/ snoring/ witnessed apnea
What are the categories of central sleep apnea?
The International Classification of Sleep Disorders – Third Edition (ICSD-3) has divided CSA into different categories:
1) Primary CSA
2) CSA with Cheyne-Stokes Breathing
3) CSA due to high altitude periodic breathing
4) Treatment-emergent CSA
5) CSA due to medication/ substance
6) CSA due to medical disorder without Cheyne-Stokes breathing
7) Primary CSA of infancy
8) Primary CSA of prematurity
Types & pathophysiology of CSA
Types of CSA:
1) Hypoventilation
- causes: narcotics (morphine, methadone), encephalitis
- pathophysio: stimulate opioid Mu receptors on neurons located in medullary resp complex
2) Hyperventilation
- causes: CCF, ESRF
- pathophysio:
1) high loop gain
- Normally, while asleep, PaCO2 usually rises which is detected by chemoreceptors, which then send a signal to the resp control in the brain stem (known as controller gain). The controller gain will then signals the respiratory muscles of the lungs and thorax (known as the plant gain) to increase ventilation, with the aim to remove CO2.
- Once the CO2 level goes down, the chemoreceptors detected this, then hypoventilation ensues to stabilize the CO2 level. So there is this feedback loop to stablise CO2 level while asleep.
- In pts with CSA, they have what is known as high loop gain, where the response to correct CO2 level is very rapid and intense, which causes overshoot of the correction.
- This causes unstable ventilation, due to the cyclical hyperventilation and hypoventilation.
- This unstable ventilation response is further accentuated by the prolonged circulation time that occurs in CCF, leading to delay between change of CO2 level in the pulm venous system, and detection of the change by the chemoreceptors.
2) narrow apnea threshold
- apnoea treshold is the level of PCO2 that causes apnoe to occur when PCO2 drops below it. The reason that this occur is to retain CO2 level and thus stabilising the CO2 level.
- In pts with CSA, the apnoea treshold is increased, and thus the treshold of the CO2 to reach the higher treshold becomes narrower, thus increasing the probability of apnea with mild hypocapnea.
3) reduced cerebral flow in CCF
- cerebral acidosis can occur which induces hyperventilation. When this occur in high loop gain system, overcorrection of the system will lead to worsening of the unstable breathing
What are the diagnostic criteria of
- primary CSA
- CSA with Cheyne-Stokes Breathing
- Treatment-emergent CSA
- CSA due to medical disorder without Cheyne-Stokes Breathing
- CSA due to medication or substance
Based on AASM Edition 3 2014
Primary CSA
A) Presence of ≥1 of following:
i) sleepiness
ii) difficult initiating or maintaining sleep, frequent awakenings or nonrestorative sleep
iii) awakening SOB
iv) Snoring
v) Witnessed apnea
B) PSG showing all of the following:
i) ≥5 central apnoeas or hypopneas
ii) total number of central apneas and/or central hypopneas > 50% of total number of apneas and hypopneas
iii) absence of Cheyne-Stokes Breathing
C) There is no evidence of daytine or nocturnal hypoventilation
D) The disorder is not better explained by another current sleep disorder, medical or neurological disorder, medication use or substance use disorder
CSA with Cheyne-Stokes Breathing:
(A+C+D or B+C+D)
A) Presence of ≥1 of following:
i) sleepiness
ii) difficult initiating or maintaining sleep, frequent awakenings or nonrestorative sleep
iii) awakening SOB
iv) Snoring
v) Witnessed apnea
B) The presence of AF or flutter, CCF, or neurologic disorder
C) PSG showing all the following:
i) ≥5 central apnoeas or hypopneas
ii) total number of central apneas and/or central hypopneas > 50% of total number of apneas and hypopneas
iii) The pattern of ventilation meets criteria for Cheyne-Stokes Breathing
D) The disorder is not better explained by another current sleep disorder, med use or substance use disorder
What is the screening tools for OSA?
1) STOP-BANG score
Stands for
S: Snoring
T: Tiredness
O: Observed apnoea
P: blood Pressure
B: BMI
A: Age
N: Neck circumference
G: Gender
Score: ≥3 –> for diagnostic PSG (level 1/2/3)
2) Epworth Sleepiness Score (ESS) - to Ax excessive sleepiness
Score:
mild excessive sleepiness: 11-12
mod: 13-15
severe ≥16
Approach to OSA/other sleep disorder cases
- Hx taking
- Physical examination
- Ix
Hx taking:
1) Ax sleep habits, MHx, drug/ETOH Hx, SHx (including stressors), FHx (e.g. narcolepsy).
- Also interview the bed partner
- clarify onset
2) Ax daytime Sx: fatigue, early morning headache, unrefreshed sleep, dry mouth, poor attention, memory impairment, mood disturbance, erectile dysfunction
2) Ax night time Sx: snoring, witnessed apnea, gasping, choking, nocturia, difficult to initiate/ maintain sleep, frequent awakening
3) Ax complications:
High BP, stroke, cognitive issues, metabolic syndrome, CVD, MVA
4) Screening tool: STOP-BANG, ESS
Physical examination:
1) BP high
2) Large neck circumference
3) Obesity
4) crowded oropharynx: use Mallampati grading (3-4), micro/retrognathia, high arch palate, enlarged tonsils, macroglossia
5) chest wall deformity/ kyphoscoliosis
6) Neurological deficits
Ix
1) Ix conditions that may cause SDB & co-morbiditiess
2) PSG (+/- video PSG)
3) Multiple Sleep Latency Test (MSLT): to document pathological sleepiness/ narcolepsy
4) Maintenance of wakefulness test (MWT): measures pt’s ability to stay awake by doing 4-5 trials of remaining awake every 2h.
- result: mean sleep latency <8m: abnormal
- MWT less sensitive than MSLT to detect narcolepsy, but more sensitive to Ax Rx (e.g. CPAP in OSA, stimulant in narcolepsy)
5) PFT - e.g. Ax for muscle weakness in NMD
6) Iron studies in restless leg syndrome
7) EMG/ NCS TRO secondary causes of restless leg syndrome
What is the Dx of OSA?
(according to International Classification of Sleep Disorders -3)
1) AHI ≥5 with Sx of OSA or assoc med/psychiatric disorder
2) AHI ≥15 even in absence of Sx or disorder
What are the levels of PSG?
Level 1 (full PSG attended): at least 7 channels
(EEG, EOG, EMG, ECG, flow, resp effort, SpO2)
- also measure body position & leg movement)
Level 2 (full PSG unattended): at least 7 channels
- also measure body position & leg movement
Level 3 (partial PSG): min 4 channels
(resp effort, air flow, pulse/ECG, SpO2)
Level 4 (for screening): min 1 channel
(SpO2, RR)
How to Ax severity of OSA?
Use AHI score
Score:
<5/hr: No OSA
5-15/hr: Mild
15-30/hr: Moderate
>30/hr: Severe
Monitoring required following PAP therapy
1) reduction in AHI
2) Reduction in Sx (use objective test e.g. ESS)
3) check Rx adherence via PAP usage data
#Rx should be multidisciplinary - respi, ENT, orthodontist, bariatric surgeon, dietitian
OSA in pregnancy
- epi
- risk
- screening/dx
- Mx
Epi:
- 15%
Risk:
preg-induced HTN
preeclampsia
GDM
PE
preterm birth
Sceening/Dx:
- Screening tool like STOPBANG has modest predictive value
- use level 1 psg or home psg (AASM guideline excludes home psg in preg)
Rx:
- CPAP
What is the requirement for split night study?
1) AHI ≥40
2) during a minimum of 2 hours of diagnostic PSG.
3) CPAP or BPAP titration is done for minimum of 3 hours
#Larger increments (i.e. 2 or 2.5cmH2O) may be needed given the shorter CPAP titration time
PAP titration
- CPAP titration method
1) Minimum starting CPAP: 4cmH2O
2) Maximum CPAP: 20cmH2O
3) CPAP to be increased by at least 1cmH2O with interval >5min until obstructive respiratory events are eliminated
4) CPAP should be increased if ≥2 apnoea/≥3 hypopnoeas/ ≥5 RERAs are observe/ ≥3min loud or unambiguous snoring
5) Pt maybe tried on BIPAP if pt is uncomfortable of high pressure on CPAP/ continued obstructive events at 15cmH2O of CPAP
6) Upward titration is continued until ≥30mins without breathing events is achieved
7) “Exploration” of CPAP above the pressure that controls the breathing events is to be done due to the residual high upper airway resistance that leads to repetitive arousal and insomnia.
It should not exceed 5cmH2O
8) “Down” titration is recommended due to “hysteresis” phenomenon, is but not required.
Hysteresis phenomenon is the lagging of an effect behind its cause.
Down titration allows for a pressure that eliminates breathing events while being a comfortable pressure for the patient.
PAP titration
- BPAP titration method
1) Minimum starting IPAP: 8cmH2O and EPAP: 4cmH2O
2) Maximum IPAP: 30cmH2O
3) Minimum IPAP-EPAP: 4cmH2O
4) Maximum IPAP-EPAP: 10cmH2O
5) IPAP and EPAP should be increased if ≥2 apnoea/≥3 hypopnoeas/ ≥5 RERAs are observe/ ≥3min loud or unambiguous snoring
6) When switching from CPAP to BPAP, the minimum starting EPAP should be set at 4 cm H2O or the CPAP level at which obstructive apneas were eliminated.
7) “Exploration” of IPAP above the pressure at which control of abnormalities in respiratory parameters is achieved should not exceed 5 cm H2O
8) Decrease in IPAP or setting BPAP in spontaneous-timed (ST) mode with backup rate may be helpful if treatment-emergent central sleep apneas are observed during the titration study
9) “Down” titration is not required but may be considered as an option
Definition of
- Apnoea
- Hypopnea
- Central apnea
- RERA
Apnoea/hypopnoea: events that lasts for ≥10s, characterized by transient reduction in (hypopnea), or complete cessation of breathing (apnoea)
Apnoea: a drop of peak signal excursion by ≥90% of pre-event baseline for ≥10s
Obstructive apnea: Apnoea with continued or increased inspiratory effort
Central apnea: Apnoea with absent inspiratory effort
Mixed apnea: Apnoea with absent inspiratory effort in the initial portion of the event, followed by resumption of insp effort in the second portion of the event
Hypopnoea: a drop of peak signal excursion by ≥30% pre-event baseline for ≥10s, with ≥3% drop in SpO2 or assoc with arousal
Respiratory effort-related arousals (RERA): a sequence of breaths lasting ≥10s characterized by increasing resp effort or by flattening of the inspiratory portion of the leading to arousal from sleep but not meeting the criteria for apnoea or hypopnoea
Problems with PAP and solution
OHA
- staging of hypoventilation in obesity
