Sleep Diagnostics Comparison

Polysomnography (PSG)

The clinical gold standard. Conducted overnight in a specialized sleep laboratory under the supervision of a polysomnographic technologist.

Parameters Measured:

• EEG (Electroencephalogram): Brain wave activity to map sleep stages and micro-arousals.
• EOG (Electrooculogram): Eye movements to identify REM sleep.
• EMG (Electromyogram): Muscle tone (chin and legs) to detect bruxism, periodic limb movements, and REM atonia.
• ECG (Electrocardiogram): Heart rate and rhythm.
• Respiratory: Airflow, chest/abdominal effort, and pulse oximetry (SpO2).

Home Sleep Apnoea Testing (HSAT)

A portable Type III or Type IV monitor used by the patient in their own bed. It focuses almost entirely on cardio-respiratory variables.

Limitations of HSAT:

Because HSATs generally do not measure brain waves (EEG), they cannot accurately determine total sleep time. They assume the patient is asleep whenever the device is recording. This often leads to an underestimation of the AHI (Apnoea-Hypopnea Index), as the denominator (total time) is artificially inflated by wakefulness.

Furthermore, HSATs cannot diagnose non-respiratory sleep disorders such as Narcolepsy, REM Sleep Behavior Disorder, or Periodic Limb Movement Disorder.

Clinical Decision Matrix

Scenario	Recommended Modality
High probability of moderate/severe OSA, no significant comorbidities.	HSAT
Suspected OSA with significant cardiovascular disease (e.g., heart failure).	In-lab PSG
Suspected Central Sleep Apnoea, Narcolepsy, or parasomnias.	In-lab PSG
Negative HSAT result, but patient remains highly symptomatic.	In-lab PSG