In vivo aerodynamic characteristics of the Nijdam voice prosthesis

The Nijdam voice prosthesis is an indwelling valveless voice prosthesis for postlaryngectomy voice rehabilitation. The in vitro aerodynamic characteristics are reported to be comparable to that of the low-resistance Groningen voice prosthesis. Owing to the design of the prosthesis the airflow resistance depends on the shaft length of the voice prosthesis in relation to the thickness of the tracheo-oesophageal wall. As tissue characteristics of the patient's oesophageal mucosa could also be of importance, an in vivo study was found necessary. To assess in vivo characteristics the following parameters were recorded in 10 patients: intratracheal pressure, intraoesophageal pressure and airflow during phonation. At an airflow of 0.15 1/sec the transdevice pressure loss varied from 0.5 up to 7 kPa (mean 3.9 kPa). With an artificial increase of the tracheo-oesophageal wall thickness, transdevice pressure losses up to 13 kPa were found. Significant interindividual as well as intraindividual differences were noted. The airflow resistance of the 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 characteristics of the Nijdam voice prosthesis found in this study indicate the need to modify the present design in order to improve its airflow resistance and to eliminate the influence of the thickness and tissue characteristics of the tracheo-oesophageal wall.