Massimiliana Carello

Staffieri tracheo-oesophageal prosthesis for voice rehabilitation after laryngectomy : an evaluation of characteristics

Experimental results on voice prostheses used for the rehabilitation of patients that have lost their vocal function after total laryngectomy are presented. The purpose is to evaluate the difference in aerodynamic behaviour between Staffieri voice prosthesis and other commercial valves (Groningen standard, Groningen low pressure, Panje, Provox). Two different equipments for flow-rate measurement were designed and built to compare the performance of the valves. The valves have been experimentally tested under different conditions of airflow through the valve and tracheal side pressure. The data allow calculation of the airflow resistance, the parameter usually used to compare the performance of valves. The valves have also been experimentally tested under different conditions of fluid flow through the valve and oesophageal side pressure (reverse flow). Comparing the airflow resistance of Staffieri valves of different length L and different angular extension of the razor-thin slit α, it has been observed that the parameter α has a significant influence on the characteristics, while the effect of the length L is negligible. The airflow resistance of the Provox, Groningen low pressure and Staffieri α=270° valves are comparable; the Panje and Staffieri α=180° have similar behaviour; while the Groningen Standard is comparable to the Staffieri α=90°. Regarding reverse flow, it is pointed out that for most of the valves (Staffieri and commercial valves), at different oesophageal pressures the fluid flow is smaller than the flow that can be tolerated by patients without giving problems.

Dynamic behavior of the Provox and Staffieri prostheses for voice rehabilitation following total laryngectomy

Abstract The present study evaluated the differences in aerodynamic behavior between the 1990 Provox and 1986 Staffieri voice prostheses for total laryngectomy patients. Both prostheses were submitted to in vitro laboratory testing to assess their aerodynamic behavior under different conditions of air flow through the valve and tracheal side pressure. In addition, six patients using the Provox and another six using the Staffieri prostheses were submitted to a dynamic study of phonation. This latter study evaluated the intratracheal pressure corresponding to the different intensities at which the vowel sound /a/ was pronounced. In vitro measurements revealed significant differences between the two prostheses, with the best results achieved with Provox. In contrast, the in vivo measurements did not reveal any significant differences between the two groups of patients in the 50–79 dBSPL range, although there was some difference at intensities equal to or greater than 80 dBSPL. Again, in this latter case the best results were achieved with the Provox. However, the ideal prosthesis has yet to be found. In some patients, the so-called low-resistance prostheses fail to maintain their aerodynamic performances, most likely because anatomic resistors interfere with the effort (i.e., pressure) required to produce a voice. At present the choice of prosthesis is best determined on an individual patient-to-patient basis.

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.

Numerical and Experimental Development of a Hub+Bearing System for Tire Pressure Control

The paper presents the study of a hub+bearing system for tire pressure monitoring and control. The tire pressure control is of importance to improve vehicle safety and dynamic behavior, and to reduce fuel consumption and emissions. This feature becomes fundamental in the development of fully automated self-driving cars, which recently some important Companies started to study and test. Firstly, a commercial version of such a system was studied experimentally to evaluate the air-flow vs. pressure curves. Then, a 2D numerical model of the system, by using the commercial CFD software Fluent, was developed and a good match was found between the numerical and the experimental results. Subsequently, taking into account the most important geometric parameters that could influence the conductance and also considering the constraints connected to the bearing dimensions, different configurations of the hub+bearing system were studied numerically. Finally, to validate the CFD results different modular hub+bearing systems were built and experimentally tested. In this way, the critical zones in terms of pressure or velocity were detected and guidelines for designing a new system were obtained.