Can you feel the electricity?
What signals are recorded in a typical PSG?
EEG (brain),
EOG (eyes),
EMG (muscles),
ECG (heart).
What does a piezoelectric sensor detect?
Mechanical movement or pressure, including body position and leg movement.
How is apnoea defined in a sleep study?
A ≥90% drop in airflow for at least 10 seconds.
What is the relationship between prolactin and sleep?
Prolactin levels increase during sleep but are not circadian-dependent.
What is impedance?
The resistance to electrical flow at the electrode-skin interface.
Where is the M1 reference electrode placed?
On the left mastoid process (behind the ear).
What is the most accurate method for measuring airflow?
Pneumotachograph (pressure-based flow transducer).
What is a hypopnoea?
A ≥30% reduction in airflow for ≥10 seconds with ≥3% desaturation or arousal.
When does core body temperature typically reach its lowest point?
During the second half of the night, especially during REM-rich sleep.
What physiological mechanism helps initiate sleep in terms of temperature?
Distal skin vasodilation promotes heat loss, facilitating sleep onset.
Name three factors that can reduce signal quality in PSG recordings.
High impedance, movement artefacts, and poor electrode placement
What is the gold standard for respiratory effort
Oesophageal pressure
Name two anatomical features that increase risk for OSA.
Enlarged tonsils/adenoids, retrognathia, or increased neck circumference.
What hormone peaks soon after sleep onset and is released during SWS?
Growth hormone.
Name two non-anatomical endotypic traits of OSA.
Low arousal threshold, high loop gain, poor pharyngeal muscle responsiveness.
What is the frequency range of delta waves?
0.5 to 2 Hz.
What are the three ways we can monitor airflow
1. Pneumotachograph
2. Thermal Sensor
3. Nasal Pressure
What distinguishes RERAs from apnoeas/hypopnoeas?
RERAs involve increased respiratory effort and arousal without meeting criteria for apnoea/hypopnoea and do not contribute to AHI.
How does chronic sleep deprivation affect metabolism?
Increases appetite (↑ghrelin, ↓leptin), reduces insulin sensitivity, and raises obesity risk.
What does a sleep spindle indicate?
A short burst of 12–14 Hz activity that marks Stage N2 sleep.
What physiological changes occur during REM sleep? (name all four listed)
Rapid eye movements, muscle atonia, sawtooth waves, and vivid dreaming.
Why is nasal pressure more reliable than thermal sensors in borderline cases?
It better detects hypopnoeas and flow limitation.
Describe the pathophysiological mechanism of OSA in terms of airway patency.
OSA results from a mismatch between collapsing forces (e.g. negative pressure) and inadequate dilating forces (e.g. pharyngeal muscle tone), leading to airway obstruction during sleep.
Which endocrine hormones are influenced by both sleep and circadian rhythms? (5)
Melatonin, cortisol, growth hormone, TSH, prolactin.
Describe the acute cardiovascular changes during an apnoeic event.
Hypoxia and negative intrathoracic pressure increase sympathetic activity, reduce stroke volume during apnoea, and cause BP/HR surges upon arousal.