The controller detects transitions between {HEAD ~ inspiration} and expiration via a flow signal to discriminate between the respiratory phases of {TAIL ~ the patient} 
The controller detects transitions between { HEAD ~ inspiration } and expiration via a flow signal to discriminate between the respiratory phases of { TAIL ~ the patient }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL