NBRC SDS cheat sheet

Sleep-Focused Testing and Therapeutic Intervention by Respiratory Therapists

• Polysomnography (PSG) montage: EEG (F4-M1, C4-M1, O2-M1), EOG (E1-M2, E2-M2), chin EMG, ECG, airflow (thermistor for apnea, nasal pressure for hypopnea), respiratory effort (thoracic/abdominal belts or RIP), SpO2, body position, and snore microphone.

• AASM scoring rules: an apnea is a ≥90% drop in airflow from baseline lasting ≥10 s; obstructive apnea requires continued or increased inspiratory effort, central apnea requires absent effort, and mixed apnea begins central and ends obstructive.

• Hypopnea (AASM recommended rule): ≥30% drop in nasal pressure signal lasting ≥10 s with ≥3% desaturation OR an arousal; the acceptable rule uses ≥4% desaturation without arousal credit.

• Respiratory event index (REI) and apnea-hypopnea index (AHI) = total events ÷ hours of sleep; AHI 5-14.9 is mild, 15-29.9 moderate, ≥30 severe obstructive sleep apnea.

• Oxygen desaturation index (ODI) = number of ≥3% or ≥4% desaturations per hour of sleep; report which threshold was used because ODI and AHI are not interchangeable.

• Sleep architecture: N1 is >50% theta with slow eye movements; N2 requires K-complexes or sleep spindles; N3 requires ≥20% slow-wave (0.5-2 Hz, >75 µV) activity; REM shows low-voltage mixed-frequency EEG, rapid eye movements, and lowest chin EMG tone.

• Arousal scoring: abrupt EEG frequency shift (alpha, theta, or >16 Hz excluding spindles) lasting ≥3 s, with ≥10 s of stable sleep required before counting another arousal in REM.

• Positive airway pressure titration: start CPAP at 4-5 cmH2O and raise by 1-2 cmH2O to eliminate apneas, hypopneas, and snoring; for bilevel, set EPAP to abolish obstructive events and IPAP-EPAP (pressure support) to correct hypoventilation and flow limitation.

• Split-night criteria: AHI ≥40 in the first 2 hours (or AHI 20-40 with clinical judgment) permits conversion from diagnostic to titration study in the same night; otherwise a full-night titration is scheduled.