Tracheo-esophageal speech using various prostheses is currently the most successful form of voice and speech rehabilitation for laryngectomies. Main inter-device differences are durability and trans-device pressure loss during speech. The valveless indwelling Nijdam voice prosthesis is a new voice prosthesis. A barrier mechanism is created by a combination of the esophageal mucosa and the umbrella-like "hat" of the prosthesis that covers the esophageal side of the tracheo-esophageal fistula. The Nijdam prosthesis can be used clinically for longer periods of time when compared to such other indwelling voice prostheses as the Provox prosthesis and the low-resistance Groningen prosthesis. However, transdevice pressure loss during speech has been unknown. Adjustment of the shft length of the Nijdam voice prosthesis to tracheo-esophageal wall thickness was expected to affect trans-device pressure loss during speech. We report the results of in vitro tests to quantify the effect of tracheo-esophageal wall thickness on trans-device pressure loss. In the present study pressure loss was measured at different air flow rates in relation to tracheo-esophageal wall thickness. Findings demonstrated that when shaft length of the Nijdam prosthesis corresponded exactly to tracheo-esophageal wall thickness, trans-device pressure loss was comparable to that of the Provox prosthesis. If a relatively shorter Nijdam prosthesis was chosen to prevent aspiration from occurring, the pressure loss across the prosthesis increased to that of the low-resistance Groningen prosthesis.