FIG. 21:  In addition to detection of an obstructed airway, current devices can also distinguish clear airway apneas, as described in this Figure.  For this the ASV device again provides inspiratory pressure support with a backup breath during an apnea and then analyzes flow.  If there is a flow response, this is an indication that this is a clear airway apnea, which would be similar to a central apnea, and in this case the EPAP is not increased.