Central sleep apnoea Flashcards
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
PAP titration
- aim
Aim:
CPAP or BPAP pressure should
i)control pt’s obstruction with the aim of
ii) lowering the respiratory disturbance index (RDI) (preferably <5/hour),
iii) SpO2 >90% and with
iV) leak within acceptable parameters
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
PAP titration
- grading of titration
Optimal titration:
- RDI <5
- for at least 15mins and
- should include supine REM sleep at selected pressure
- that is not continually interrupted by spontaneous arousals or awakenings
Good titration:
- RDI ≤10 or
- by 50% if baseline RDI <15 and
- should include supine REM sleep at selected pressure
- that is not continually interrupted by spontaneous arousals or awakenings
Adequate titration:
- does not reduce RDI ≤10 but
- reduces the RDI by 75% from baseline, or
- criteria for optimal or good are met with exception that supine REM sleep did not occur at selected pressure.
Unacceptable titration: does not meet any one of the above grades
Repeat PAP titration to be considered if initial titration does not achieve a grade optimal or good, or if in split-night, it fails to meet AASM criteria (e.g titration duration should be >3h)
PAP titration
- aim
Aim:
CPAP or BPAP pressure should
i)control pt’s obstruction with the aim of
ii) lowering the respiratory disturbance index (RDI) (preferably <5/hour),
iii) SpO2 >90% and with
iV) leak within acceptable parameters
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
Scoring Cheyne-Stokes Breathing from AASM guideline 2023
Score CBS if BOTH the following are present:
a) There are episodes of ≥3 consecutive central apneas and/or hypopneas separated by a crescendo and decrescendo change in breathing amplitude with a cycle length of ≥40s
b) There are ≥5 central apneas and/or hypopneas perhour of sleep associated with the crescendo/decrescendo breathing pattern recorded over ≥2h of monitoring
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
Add for Treatment-emergent CSA
A) PSG:
- Diagnostic PSG showed ≥5 predominantly obstructive resp events (apnea, hypopnea, RERA) per hour of sleep
B) PSG during PAP without backup rate shows significant resolution of obstructive events and emergence or persistence of central apnea or central hypopnea with all the following:
i) AHI ≥5
ii) Central AHI ≥5
iii) Number of central apneas and hypopneas is ≥50% of total number of apneas and hypopneas
C) The central sleep apnea is not better explained by another central sleep apnea with CSB or CSA due to drug or substance
CSA due to medical disorder without Cheyne-Stokes Breathing
Criteria A-C must be met
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 snoring
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) The disorder occurs as a consequence of a medical or neurological disorder but is not caused by medication or substance use.
CSA due to medication or substance:
A) The pt is taking an opioid or other resp dspressants
B) 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 snoring
C) 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
D) The disorder occurs as a consequence of an opioid or other resp depressant and is not better explained by another current sleep disorder
How does Adaptive Servo Ventilation (ASV) help with CSA
ASV is a form of positive airway pressure (PAP) therapy that delivers auto-adjusting pressure support (with automatic Pressure Support (PS) and Expiratory Positive Airway Pressure (EPAP). ASV helps to treat both obstructive and central respiratory events and maintains adequate ventilation in response to patients’ changing needs.
This it stabilises the breathing and keeps the airway open
