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What is Sleep Apnea?
Obstructive Sleep Apnea (OSA)
Central Sleep Apnea (CSA)
Sleep Labs
Home Sleep Study
What is Tested?
Apnea–Hypopnea Index (AHI)
How to use the Ares
How to use WatchPat
Intializing the ARES
Uploading the Results
What's Next?

Sleep Study Signals and Measurement

Oxygen Saturation –

ARES captures blood oxygen saturation and pulse rate using reflectance pulse oximetry. The ARES oximeter was designed specifically for the diagnosis of OSA, which involves the detections and quantification of brief desaturations and resaturations. It measures oxyhemoglobin saturation in 0.1% increments rather than the typical 1%, which allows identification of small but important changes in saturation. 

Airflow (nasal pressure) –

 Changes in air pressure are measured with a pressure transducer connected to the nasal opening via a nasal cannula. Decreases and increases in flow of 50% or more are automatically identified and marked as hypopneas and cessations of airflow for at least 10 seconds are marked as apneas. 

Pulse Rate – 

ARES uses reflectance pulse oximetry to measure pulse rate. Limited smoothing of pulse rate signal increases capability of ARES Insight software to recognize brief changes in pulse rate (e.g., Brady-tachycardias). These changes in pulse rate are recognized markers of arousal. 

Snoring – 

Snoring is recorded with a calibrated acoustic microphone so that the level of loudness can be precisely quantified. Changes in snoring patterns and crescendo snoring are automatically recognized and used as markers of a respiratory-related arousals. 

Head Position/Movement –

Head position indicates the position of the pharynx and is used to determine the positionality of obstructive events. Understanding the influence of position on the severity of the OSA is useful in making treatment decisions. Head movement is measured using accelerometers similar to those used for actigraphy. Head movement is a unique signal identified by ARES as a marker of respiratory related arousal. 

Sleep/Wake –

 ARES measures sleep behaviorally by combining the detection of subtle movements through actigraphy, with variability of the airflow signal and recognition of snoring. 


 ARES distinguishes REM from NREM using EEG, EOG and EMG signals derived from two electrodes placed at FP1 and FP2 on the forehead. 

Apnea/Hypopnea Index (AHI) –

ARES determines AHI by adding the number of apneas and hypopneas per hour, where there is a 4% oxygen desaturation.

Respiratory Disturbance Index (RDI) – 

ARES measures RDI by adding the number of apneas and hypopneas per hour, where the hypopneas require a 1% oxygen desaturation/resaturation and at least one behavioral arousal indicator.