Monitoring and Measurement of Sleep Apnoea Flashcards
What is Sleep Apnoea?
- Full or partial collapse of Upper airway during sleep
- Leading to sleep arousal
Name some symptoms of SA?
- Snoring
- Restless Sleep
- Nocturia
- Wake choking
- Depression
- Unrefreshing sleep
- Decreased libido
- Daytime Somnolence
What is the most common sleep-related breathing disorder?
- OSA (obstructive sleep apnoea)
- Increasing with rising levels of obesity and also bc more people are actually being diagnosed now
What are some pre-disposing factors for SA?
- Obesity
- Age
- Gender
- Ethnicity (ACS)
- Prevalence in Asia for SA is similar to USA bc of craniofacial anatomy
- Airway size/shape
- Upper airway muscle function
What is the link between obesity and OSA?
-Risk of OSA correlates with increasing BMI
What are some factors affecting Upper airway shape/size?
- Obesity (increased neck size)
- Smoking
- Upper airway lesions
-Skeletal abnormalities
(Retrognathia and Cranio-facial deformity)
- Smoking
- Hormonal (Goitre)
- Supine sleeping position
What are 3 factors affecting Upper airway muscle function?
- Sleep Deprivation
- Alcohol and sedative usage
- Neurological disorders
How can we measure OSA?
- Accurate history is vital
- Identify features of OSA
- Rule out alternative diagnoses
- Assess impact on QoL
- Ideally partner/parent/family member present
What sort of history would you want to know to discuss OSA?
- General medical and drug history
- Alcohol intake?Smoker?
- Physical examination
- For pre-disposing factors
What is the Mallampati Score?
- Guide to increased likelihood of OSA
- Basically looking at the mouth to see how much of the tonsils you can see and how occluded it is
How can Sleep Questionnaires be useful?
- Measure daytime symptoms and QoL
- Most common is ESS (Epworth)
- Others include sleep diaries/QSQ/FOSQ/Beck depression inventory
- They are used in new and follow up patients to assess response to treatment
What is ESS score?
Epworth Sleep Score
-Looks at risk of dozing
- Normal 0-9
- Midl 10-15
- Significant 16-24
What is SF-36?
- Questionnaire with 36 questions related to QoL
- NO sleep component
What is FOSQ?
Functional Outcome in Sleep
-Assess impact of Sleep Disorders
What is Beck Depression Inventory?
- Similar to ESS
- High score more likely to deal with depression
What are 3 ways we can monitor Sleep?
- Overnight Oximetry
(SpO2 + HR)
-Limited Sleep Study
(Variety) (seen on placement)
-Full Polysomnography
(Resp parameters + EEG + EOG + EMG
Define an Apnoea?
- Cessation fo airflow (Greater than or equal to a 90% reduction)
- Minimum of 10s
- Obstructive if effort to breathe is maintained
- Central if absence of respiratory effort
Define an Hypopnea?
- Reduction in airflow signal with an Ox Desaturation
- Greater than or equal to 30% reduction in airflow
- Min 10s
Advantages of Oximetry?
- Simple
- Minimal invasion
- Cheap
- Suitable to use at home
Disadvantages of Oximetry?
- Limited info
- Single Measurement no other data if it falls for eg
- Sensitivity good but specificity poor
What parameters do we look for with Oximetry?
- Dips in SpO2
–>greater than or equal to 4% drop
–>more than 10 events per hour suggest respiratory disturbance
-Pulse rate
–> HR rises by more than or equal to 6BPM
–> If there’s more than 15 events per hour it is significant
What are some sources of error?
- Poor Signal
- Movement Artefact
- Sampling frequency
- Data smoothing
What does a Limited Sleep Study involve?
- Nasal Flow
- Chest and Abdomen bands to measure respiratory effort
- Oximeter
- Snoring via mic
- Body Position
- Video/Sound (sometimes)
- ECG (if required)
What are some sources of error with limited sleep studies?
- Nasal airflow could be nasal blockage
- Band movement may be high with high BMI patients
- Backround noise could affect snoring measurement
- Body position may be incorrect can confirm with video
- Sound/Video must be time synchronised and IR is essential
Advantages of Polygraphy?
- Wider range of data compared to pulse ox
- Can be used at home
- Can add extra channels
Disadvantages of Polygraphy?
- Still limitation of data
- More intrusive to patient ‘normal sleep’
What extra parameters does Full PSG have?
- EEG
- EOG
- EMG
What is EEG?
- Electroencephalography
- It measures electrical activity of brain placed on scalp and can determine sleep stages
What is EOG?
- Electrooculography
- Assists in determining sleep stage (REM)
What is EMG?
- Electromyography
- Chin electrodes determine REM using muscle atonia
- Leg electrodes to screen for PLM’s
Sources of error for full PSG?
- Poor Skin preparation
- Sweat artefact
- Body Hair
Advantages of PSG?
- Gold Standard
- Full picture of sleep
- confirms REM-related OSA
- Useful when patient history is mix of sleep disorders
Disadvantages of PSG?
- Expensive
- In-hospital test
- Lots of data not all necessary for simple respiratory screening
- Uncomfortable for patient
OSA and driving?
- Patients obliged to inform DVLA
- Wisconsin study found 7X more likely to have Motor accidents
