Patent ID: 7402139

Claim:
An apparatus for determining impedance (Z aw ) of a patient's respiratory tract by measuring alternating pressure (dp) in a region of the patient's mouth after producing an oscillating air pressure signal, comprising: a mouthpiece; an electroacoustic transducer having an oscillation system for generating an oscillating air pressure signal; a tube for connecting said electroacoustic transducer to said mouthpiece; a reference resistance for determining a reference impedance (Z ref ); computing means for calculating impedance (Z aw ) of a patient's respiratory tract based upon said reference impedance (Z ref ) of said reference resistance, total impedance (Z ges ) and total phase angle (Φ); and, means for contactlessly measuring change in deflections of said oscillation system of said electroacoustic transducer caused by alternating pressure (dp) of the patient's breathing.