IN-VIVO AERODYNAMIC CHARACTERISTICS OF THE NIJDAM VOICE PROSTHESIS

The Nijdam voice prosthesis is an indwelling valveless voice prosthesi s for postlaryngectomy voice rehabilitation. The in vitro aerodynamic characteristics are reported to be comparable to that of the low-resis tance Groningen voice prosthesis. Owing to the design of the prosthesi s the airflow resistance depends on the shaft length of the voice pros thesis in relation to the thickness of the tracheo-oesophageal wall. A s tissue characteristics of the patient's oesophageal mucosa could als o be of importance, an in vivo study was found necessary. To assess in vivo characteristics the following parameters were recorded in 10 pat ients: intratracheal pressure, intraoesophageal pressure and airflow d uring phonation. At an airflow of 0.15 l/sec the transdevice pressure loss varied from 0.5 up to 7 kPa (mean 3.9 kPa). With an artificial in crease of the tracheo-oesophageal wall thickness, transdevice pressure losses up to 13 kPa were found. Significant interindividual as well a s intraindividual differences were noted. The airflow resistance of th e Nijdam voice prosthesis in relation to the thickness of the tracheo- oesophageal wall was compared with the airflow resistance reported for various other voice prostheses. The in vivo aerodynamic characteristi cs of the Nijdam voice prosthesis found in this study indicate the nee d to modify the present design in order to improve its airflow resista nce and to eliminate the influence of the thickness and tissue charact eristics of the tracheo-oesophageal wall.