Abstract: A transducer assembly comprising an inner, primary, transducer having a pair of transducers fixed to a liner or cavity for providing the fluid compression sending and receiving signals for measuring the velocity and change of composition of fluid in the cavity which is being inspired and expired by a patient in a setting, such as in an intensive care unit of a hospital. The inner transducer is disposed in a heated housing to maintain the temperature of the inner transducer at a temperature above the saturation point of the fluid being measured and is further provided with (1) an acoustical absorber to prevent sound energy from the connection tubes, which connect the transducer assembly to endotracheal tubing, from adversely affecting fluid measurements and, (2) water absorbing material to prevent water, which might condense in the connecting tubing, from entering the inner transducer and affecting the fluid measurements.