6.1 Sleep Disordered Breathing Flashcards
What are the 2 states of sleep?
- Rapid eye movement (REM)
- non-REM (NREM)
What are the three sources of data that enable us to determine whether someone is in REM or NREM?
- Electroencephalographic (EEG)
- Electro-occulographic (EOG)
- Electromyographic (EMG)
What are the three divisions of NREM sleep? Which is the deepest, and which is the lightest?
Divided into N1, N2, and N3
N1 is the lightest, N3 is the deepest
What is the first state that someone usually goes into when they fall asleep: REM or NREM?
NREM
Which state of sleep predominates the first third of the night? Why?
N3; this is thought to be critical to bodily recovery and growth.
Which state of sleep predominates the last third of the night? What happens to the heart during this time?
REM sleep; the heart is active, although there is general muscle atonia
Do we need more or less sleep as we age?
Less
How much does alveolar ventilation decrease during sleep (in litres/min)? Why?
- 1-2L/min
- Occurs due to decreased tidal volume, and shallower and more irregular breathing
What happens to the body’s response to hypercapnia and hypoxaemia during sleep? When is this trend more pronounced?
- It is attenuated; lower alveolar ventilation increases CO2 conc and decreases O2
- This is especially pronounced during N3, and even more so during REM
How does the body’s response to hypercapnia and hypoxaemia decrease during sleep?
- No wakefulness drive to breathe
- Reduced lung volume (when lying flat, the organs push the diaphragm upwards)
- Reduced chemosensitivity to CO2 and O2 (20-50%)
- Reduced tone of intercostal muscles
What happens to metabolic rate during sleep? By how much?
Down by 10-15%
What questions should you ask during a sleep history?
- Do you sleep well?
- Are you restless during sleep (waking up a lot)?
- Difficulty falling/staying asleep?
- Do you wake early?
- Are you uncomfortable during sleep?
- Sleep routine (alarm/no alarm)
- Are you refreshed upon waking?
- Tired?
- Inappropriate falling asleep? (Safety?)
- Snoring (other apnoea symptoms)
- Rest of history (after PC)
- Collateral history
What characterises OSA?
Repetitive episodes of upper airway obstruction during sleep; frequent arousals. Effort to breathe despite obstruction.
OSA risk factors?
- Alcohol
- Obesity
- Upper airway abnormality
(Homer Simpson)
List some consequences of sleep fragmentation that could show up in an OSA history
- Decreased memory, concentration, irritability
- Headaches
- Unrefreshing sleep
Obstructive vs central apneas?
Obstructive: Upper airways resistance and obstruction, characterised by effort to breathe against resistance
Central: Due to lack of control from brainstem resp. centres; charcterised by lack of effort
What are mixed apnoeas?
Combination of central and obstructive apnoea
Define hypopnea
Reduction of airflow with associated arousal during sleep, or oxygen desaturation
How many apnoeas, hypopnoeas and “unsure” events must happen per hour to be considered abnodrmal or severe?
Abnormal: >10
Severe: >30
Describe some acute consequences of OSA
- Excessive somnolence (desire to fall asleep); could pose a safet risk
- Sleep deprivation may have psychosocial consequences (including snoring, which could piss of your girlfriend…)
Why does sleep apnoea increase risk of CVD, Cerebrovascular event, and hypertension?
- Arousal releases excitatory hormones, interrupting periods of restorative sleep and leading to vascular remodelling
How does OSA cause pulmonary hypertension?
Remodelling due to excessive hypoxia
You suspect someone may have OSA, but they are not drowsy. They operate heavy machinery for a living. Do you refer them to a sleep study?
Yes. Of course.
Why might patients not be very compliant with CPAP treatment?
- Mask discomfort
- Dry mouth from airflow
- It doesn’t look very appealing
- Claustrophobia
- Cost
How does a mandibular splint work? Is it effective for obese patients?
- Splint pulls jaw forward to keep airways open
- Not effective for obese patients
True or false: weight loss has minimal impact on improving OSA
- False
- It almost always leads to an improvement, and the improvement can be significant
What is respiratory disturbance index?
Total number of apnoeas/hypopneas per hour
Is surgery available for OSA?
Yes
How much less common is central sleep apnoea than obstructive sleep apnoea?
About 10 times less common
Why is central sleep apnoea important?
It can lead to the diagnosis of other, comorbid conditions
Can neuromuscular diseases cause central sleep apnoea? If so, how?
- Yes, they can
- Muscles are either too weak to breathe, or lack of brainstem control of muscles
What are some parameters recorded by a sleep study?
- EMG
- EEG
- EOG
- ECG
- Leg movement
- Microphone (snoring)
What is the minimum amount of time without breathing before an event is considered an apnoea?
10 seconds
