Sleep Disorder Terminology

Respiratory Event Types and Scoring Criteria:

 

Obstructive apnea: Cessation of airflow (≥90% decrease in apnea sensor excursions compared to baseline), lasting at least 10 seconds, with 90% of event duration meeting the amplitude criteria.  Obstructive apneas are associated with continued or increased effort throughout the entire period of absent airflow

Central apnea: Cessation of airflow (≥90% decrease in apnea sensor excursions compared to baseline), with 90% of event duration meeting the amplitude criteria.  Central apneas are associated with absence of inspiratory effort throughout the entire period of absent airflow

Mixed apnea Cessation of airflow (≥90% decrease in apnea sensor excursions compared to baseline), with 90% of event duration meeting the amplitude criteria.  Mixed apneas are associated with absence of inspiratory effort at the start of the event, followed by return of inspiratory effort during the second portion of the event

Hypopnea: A reduction in airflow (≥30% reduction in nasal pressure signal from baseline), lasting at least 10 seconds, with 90% of event duration meeting the amplitude criteria.  Hypopneas are associated with an oxygen desaturation of at least 3% or an EEG arousal

RERA: Respiratory Effort Related Arousal – a sequence of breaths ≥10 seconds, with increasing respiratory effort or flattening of the nasal pressure signal leading to an EEG arousal during sleep (scored when criteria for hypopnoea is not met)

Periodic Limb Movement (PLM) of sleep: Movements of the limbs occurring with a specific frequency, duration, and amplitude.

 

Level 2 Sleep Study

 

Device Used:  Nox A1

Signals Recorded: EEG, EOG, ECG, EMG, Thoracic & Abdominal Effort (RIP), Position, Audio (Snoring), Pulse Rate & Waveform, Nasal pressure, calRIP Flow, Ambient Light, Oxygen Saturation (+/- additional signals)

 

Index as an indication of severity

AHI - Apnoea Hypopnoea Index:

 

Normal: < 5/hr

Mild OSA: AHI 5 ≤ 15/hr

Moderate OSA: AHI 15 ≤ 30/hr

Severe OSA: AHI > 30 events/hr

 

Terminology Commonly Used in Sleep Test Reports

 

REM sleep:  Rapid Eye Movement

NREM sleep:  Non-Rapid Eye Movement (Stage 1, 2 and 3)

REM latency:  time it takes from sleep-onset to the first period of REM sleep

Sleep latency:  how long it takes for a patient to get to sleep.  From time of lights off to the start of the first epoch of any stage of sleep

WASO: Wake After Sleep Onset. Any time spent awake after sleep onset

Arousal: abrupt shift of EEG frequency during a minimum of 10 sec of sleep prior for >3 seconds

Arousal Index: indicates frequency of all types of arousals per hour of total sleep time

AHI: Apnea Hypopnea Index - indicates frequency of obstructive events (#apneas

+ #hypopneas) per hour of total sleep time (TST)

RDI: Respiratory Disturbance Index – indicates frequency of respiratory events (#RERA + #apneas + #hypopneas) per hour of total sleep time (TST)

ODI:  Oxygen Desaturation Index - indicates frequency of a blood's oxygen desaturation drop of ≥3% or more from baseline per hour of total sleep time (TST)

Sleep Efficiency (%): Total Sleep Time / Total Recording Time (“lights on” to “lights off”) x 100

Nadir Oxygen Desaturation - From the ASA guidelines it states:

  • severe oxygen desaturation has been classified as an oxygen saturation <85% for more than 2% of the total PSG sleep time
  • minimal or no desaturation has been classified as no PSG sleep saturation less than 90%
  • oxygen saturation of <85% for more than 50% of sleep time (breathing air) has been suggested as another threshold value defining severe sleep-related hypoventilation

Please Note:  These figures are just a guideline as there is no standardised index:

97%>     Normal

<90%     Mild

<85%     Moderate

<80%     Severe

 

Treatment Devices Abbreviations

 

CPAP:  Continuous Positive Airway Pressure – a fixed pressure is delivered to the patient

APAP:  Automatic Positive Airway Pressure - automatically adjusts to the patient’s pressure requirements

BiPAP or VPAP:  Bi-level or Variable pressure device that provides two levels of pressure. Inspiratory Positive Airway Pressure (IPAP) and a lower Expiratory Positive Airway Pressure (EPAP) for easier exhalation

 

Screening Tests

 

ESS:  Epworth Sleepiness Scale –a short questionnaire that determines the likeliness of the patient to fall asleep in certain situations.  The total score is out of 24, a score above 10 indicates an above average sleepiness