Experimental comparison between a Staffieri and a New Prototype tracheo-oesophageal valve

A tracheo-oesophageal valve is used for the rehabilitation of patients who have lost vocal function due to a total laryngectomy. The valve is positioned in a surgically created fistula between the airway and the upper oesophagus at the level of the post-laryngectomy stoma. It permits passage of air from the trachea to the pharynx to permit speech, while it blocks the flow of secretions and food materials from the digestive tract to the airway. In this paper, experimental results obtained with a Staffieri and a New Prototype tracheo-oesophageal valve are presented. The valves have been tested experimentally under different conditions of airflow through the valve and tracheal-side pressure; the airflow resistance has been calculated to compare the performance of the valves. The valves have also been experimentally tested under different conditions of fluid flow through the valve and oesophageal-side pressure. The airflow resistance of the Staffieri and the New Prototype valves has been compared for different angular extents, alpha, of the razor-thin slit through which the airflow passes. For each type of valve the parameter alpha has a significant influence on flow characteristics, while the shape of the dome becomes important only for the larger angular extents considered.Regarding the reverse flow, it is pointed out that for both of the valve types at different oesophageal pressures and for smaller angular extents of the razor-thin slit, the reverse fluid flow through the valves is smaller than the allowable reverse flow, that can be tolerated by patients without creating problems. In general, for high values of the angular extent of the razor-thin slit the Staffieri valve offers the least flow resistance, but, unlike the New Prototype, the direct flow under these conditions in unacceptably large.