In vivo measurements of indwelling tracheo-oesophageal prostheses in alaryngeal speech.

Over the last 5 years, detailed air pressure, flow and voice measurements have been made on indwelling tracheo-oesophageal speaking valves whilst inserted in patients, using specially designed apparatus. This study was set up to investigate the relationship between speech and in vivo parameters. In vivo pressure measurements were generally lower for Groningen low resistance than Groningen high resistance, while flow and voice measurements were higher. A plot of opening pressure against pressure at maximum flow for all valves suggested a straight line relationship. A graph of maximum voice against composite parameter score for all valves showed a cluster of points between the composite score of 0-15. The advances in knowledge about these valves should be of use in the design of improved valves.