An airway adapter that comprises a housing and a pressure transducer. The
housing comprises a flow path having a first end and a second end, a
first pressure port that communicates with the flow path, and a second
pressure port that communicates with the flow path. The first pressure
port is spaced apart from the second pressure port. The flow restriction
is disposed in the flow path between the first and second pressure ports
that creates a pressure differential therebetween. The pressure
transducer generates a signal that reflects the differential pressure
created by the flow restriction between the first and second pressure
ports, wherein the pressure transducer comprises an optical
interferometer.