The GK™420E is an automatic CPAP device. The advanced Auto algorithm adjusts the pressure in response to apneas and hypopneas, but also to all indicators of increased resistance in upper airway such as snoring or inspiratory flow limitation. The Cardiac Oscillations Technique (COT) classifies the apneas in either Obstructive or Central, making sure that no pressure increase will occur in central events. Summary data, usage data, pressure, respiratory events and trends are recorded in the device memory and can be downloaded and processed by the Silverlining3 PC software.