Level 3 Sleep Study

1. SLEEP / WAKE AREA

• Meaning: Estimated sleep vs. wake time based on body movement, respiratory effort, and sometimes actigraphy.
• Role in Diagnosis: Helps determine how much time the patient was likely asleep vs. awake during the study, allowing accurate calculation of sleep efficiency and apnea index.

2. RASTER VIEW – ACTIVITY

• Meaning: Actigraphy-based measurement of body movement (rest-activity cycles).
• Role: Used to identify rest periods (sleep) and activity (wake). Supports sleep/wake estimation in absence of EEG.

3. SLEEP EFFICIENCY

• Formula: Sleep Efficiency = (Total Sleep Time ÷ Total Recording Time) × 100
• Role: Indicates sleep quality. Low efficiency may suggest insomnia, discomfort, or frequent awakenings (possibly due to apnea or oxygen desaturation).

4. TOTAL SLEEP TIME (TST)

• Meaning: The total duration the patient is estimated to be asleep during the test.
• Role: Used to normalize respiratory events (e.g., AHI = events per hour of sleep). Accurate TST gives a more precise severity assessment.

5. SLEEP LATENCY

• Meaning: Time taken to fall asleep after the recording starts.
• Role: Increased latency may indicate poor sleep initiation, anxiety, or discomfort. Helps assess overall sleep pattern quality.

6. AROUSAL (AUTONOMIC)

• Meaning: Brief awakenings or surges in autonomic activity (heart rate, movement, or changes in respiratory pattern).
• Role: Frequent autonomic arousals indicate sleep fragmentation—common in sleep apnea due to repetitive breathing pauses.

7. RESPIRATORY ANALYSIS (ALL AHI EVENTS)

• AHI = Apnea–Hypopnea Index
• Apnea: ≥90% reduction in airflow for ≥10 seconds.
• Hypopnea: ≥30% reduction in airflow for ≥10 seconds with ≥3–4% oxygen desaturation or arousal.

8. BODY POSITIONS WITH APNEA AND FLOW LIMITATIONS

• Meaning: Records body posture (supine, lateral, prone) and correlates with respiratory events.
• Role: Helps identify positional sleep apnea, where events occur mostly in supine position.

9. RR INTERVAL (COMPLETE RECORDING)

• Meaning: Beat-to-beat interval derived from ECG or pulse oximetry (heart rate variability).
• Role: Detects cardiac autonomic fluctuations, arrhythmias, and heart rate changes due to apneas or hypoxia.

10. CHEYNE–STOKES EVENTS

• Meaning: A cyclic pattern of waxing and waning breathing amplitude, often with central apneas.
• Role: Seen in heart failure or neurological disorders; important for diagnosing Central Sleep Apnea syndromes.

11. SNORING ANALYSIS

Components:

• Snore Index: Number of snores per hour.
• Absolute Snoring (min): Total duration of snoring sounds.
• Snore Episodes (min): Number and length of distinct snoring periods.
• Role: Helps evaluate upper airway resistance and snoring severity, correlates with obstruction events.

12. O₂ SATURATION (SpO₂)

• Meaning: Continuous monitoring of blood oxygen levels.
• Key Metrics:
• Mean SpO₂: Average oxygen level.
• Lowest SpO₂: Nadir oxygen level.
• ODI (Oxygen Desaturation Index): Number of ≥4% drops in SpO₂ per hour.
• Role: Detects hypoxemia during apneas/hypopneas; critical in assessing physiological impact.

13. HEART RATE

• Meaning: Pulse rate variability throughout the study.
• Role: Increases during arousals and apneic events; used to detect autonomic responses and possible cardiac stress.