Polysomnography - Sleep Study Secrets
- Polysomnography (PSG) is a comprehensive, multi-parametric test that records various physiological variables during sleep. 📌 PSG: Patient Sleep Graphed.
- Primary Goals:
- Diagnose Obstructive Sleep Apnea (OSA) and assess its severity.
- Differentiate central, obstructive, and mixed apneas.
- Evaluate other sleep disorders (e.g., narcolepsy, periodic limb movement disorder).
⭐ Polysomnography is the gold standard for the diagnosis of Obstructive Sleep Apnea (OSA).
Polysomnography - Sensor Central Station
📌 SEE Cardio-Respiratory Activity: Sensors (EEG, EOG, EMG), Cardiac (ECG), Respiratory (Airflow, Effort, SpO2), Additional (Snoring, Position).
| Sensor/Channel | Parameter Measured | Clinical Significance (OSA/SDB) |
|---|---|---|
| Electroencephalogram (EEG) | Brain activity | Sleep staging; arousals |
| Electrooculogram (EOG) | Eye movements | REM sleep identification |
| Electromyogram (EMG) - Chin | Chin muscle activity | Muscle atonia (REM); bruxism |
| Electromyogram (EMG) - Limbs | Limb muscle activity | Periodic Limb Movements (PLMS) |
| Electrocardiogram (ECG) | Heart rate/rhythm | Arrhythmias; event-related HR changes |
| Nasal/Oral Airflow (Thermistor/Pressure) | Airflow | Apneas/hypopneas detection |
| Thoracic & Abdominal Effort (RIP) | Respiratory movements | Differentiates central vs. obstructive events |
| Pulse Oximetry (SpO2) | Oxygen saturation | Oxygen desaturation with events |
| Snoring Sensor (Microphone) | Snoring | Upper airway resistance indicator |
| Body Position Sensor | Supine, prone, lateral | Positional OSA/SDB identification |
⭐ Chin EMG demonstrating muscle atonia is a key feature for identifying REM sleep.
Polysomnography - Decoding Dream Data
Polysomnography (PSG) records multiple physiological parameters during sleep to diagnose sleep disorders.
- Sleep Staging (AASM Criteria):
- NREM Sleep: N1, N2, N3 (Slow Wave Sleep).
- REM Sleep.
- Key parameters: EEG (brain activity), EOG (eye movements), EMG (muscle tone).
- Respiratory Event Definitions:
- Apnea: Cessation of airflow ≥90% for ≥10s. Types: Obstructive, Central, Mixed.
- Hypopnea: Airflow reduction ≥30% for ≥10s associated with ≥3% O2 desaturation or an arousal.
- Key Indices:
- Apnea-Hypopnea Index (AHI): $AHI = \frac{\text{Total Apneas + Total Hypopneas}}{\text{Total Sleep Time (hours)}}$
- Respiratory Disturbance Index (RDI)
- Oxygen Desaturation Index (ODI)
- Arousal Index
- OSA Severity (AHI): 📌 5 (Normal limit), 15 (Mild ends), 30 (Moderate ends). Thresholds: Normal <5/hr; Mild 5-14.9/hr; Moderate 15-29.9/hr; Severe ≥30/hr.
⭐ An obstructive apnea is defined by continued or increased respiratory effort despite airflow cessation, distinguishing it from central apnea where effort is absent.
Polysomnography - Levels & Links
📌 PSG Types: Type I is In-Lab, the Ideal standard. As numbers go up (II, III, IV), comprehensiveness typically goes down.
| Type | Setting | Key Channels Monitored | Attended? | Primary Use | Advantages | Disadvantages |
|---|---|---|---|---|---|---|
| I | In-Laboratory | EEG, EOG, EMG, ECG, Airflow, Effort, SpO2, Snoring, Leg movements | Yes | Gold standard; Complex sleep disorders, CPAP titration | Highest accuracy, comprehensive data | Costly, inconvenient, less natural sleep |
| II | Home (Unattended) | Similar to Type I | No | OSA diagnosis, CPAP titration in select cases | Comprehensive data at home | Less accurate than Type I, no direct observation |
| III | Home (Unattended) | ≥3 channels (e.g., Airflow, Effort, SpO2, HR) | No | Uncomplicated OSA diagnosis | Convenient, lower cost | Limited data, may miss other disorders, higher failure rate |
| IV | Home (Unattended) | 1-2 channels (e.g., SpO2 ± Airflow/HR) | No | Screening for OSA, oximetry | Very convenient, lowest cost | Lowest accuracy, high false negative rate |
High‑Yield Points - ⚡ Biggest Takeaways
- Polysomnography (PSG) is the gold standard for diagnosing Obstructive Sleep Apnea (OSA).
- Key parameters include EEG, EOG, EMG, ECG, airflow, respiratory effort, and SaO2.
- Apnea-Hypopnea Index (AHI) quantifies OSA severity: Mild (5-15), Moderate (15-30), Severe (>30 events/hr).
- Differentiates obstructive, central, and mixed apneas.
- Assesses sleep architecture, including sleep stages and arousals.
- Oxygen Desaturation Index (ODI) is also a critical measure of nocturnal hypoxemia related to OSA events.
Unlock the full lesson and continue reading
Signup to continue reading this lesson and unlimited access questions, flashcards, AI notes, and more
