Speaking valves: influence of the fatigue on the flow characteristics

The in vivo operation of a speaking valve consists of two stages: 1) air passes through the razor-thin slit, the dome opens and the patient can speak; 2) the dome is closed and the patient cannot speak. The valve is thus subject to fatigue, as its service life is made up of a certain number of opening/closing cycles. Two types of valve were investigated: the Staffieri valve and a new valve prototype featuring a different angular extension of the razor-thin slit. The investigation assessed fatigue degradation in valve flow characteristics; for this purpose a special test rig has been constructed. Fatigue tests have been performed in four steps and the airflow resistance has been determined experimentally at the end of each step. The experimental data have been used to make a statistical analysis to evaluate the effects of razor thin slit, type of valve, number of cycles and their interactions.