The deformation of new and failed silastic speaking valves

Abstract

Silastic speaking valves fail due to eroding microbial colonies. How this erosion affects the integrity of the silastic is unknown. A new technique to measure the deformability of the valves was devised and used to assess new and failed valves. Incremental weights were used to deform each valve: the degree of deformation was measured with a Vernier calliper. Graphs of the deformability against the weight increment were plotted and the slope determined. The instrument was tested by testing one valve 10 times. The deformation of 90 new Groningen values was tested, the same valves also tested after failure. The test re-test data was normally distributed. A Bland and Altman plot of the sd against the means showed good agreement demonstrating this to be a reliable and repeatable test. The deformation slopes of the 90 valves measured pre- and post-insertion were examined by Wilcoxon Matched Pairs and this showed that there was no difference between the two populations (z = −0.56, P = 0.57, NS, n = 90). Examination of the slopes demonstrated there was an equal increase and decrease in the deformability of the valves after failure. This work suggests that the integrity of the silastic is unaffected by colonization even though the architecture is disrupted.