Investigation of Eustachian tube function
This Thesis aims to investigate the relationship between the temporal characteristics of the muscular activity of the Eustachian tube and its opening in adults and children so as to achieve a greater understanding of the mechanisms involved in tubal function during the act of swallowing. This should lead ultimately to a greater understanding of the causes of the high occurrence of middle ear effusion in children. This was accomplished by developing a new methodology for evaluating Eustachian tube function and carrying out experiments on adults and preschool children. A comprehensive review of the literature related to the physiology of swallowing, the anatomy, physiology, and dysfunction of the Eustachian tube is presented which reveals that the above areas of research require further investigation. A new technique which measures tympanic membrane displacement was used as an indicator of Eustachian tube muscular activity, together with the more conventional method of sonotubometry which detects Eustachian tube opening, during experiments upon both adults and children. Evidence from the experimental work revealed differences in the muscular activity of the Eustachian tube between adults and children. The adult group had a larger muscular activity compared to a smaller muscular activity for the preschool children. It was also evident that an aquiescent period of 72 milliseconds exists between the muscular activity of the Eustachian tube and its opening. This was found to be the same for the two subject groups. In addition, using sonotubometry, 50 percent of the preschool children's ears tested showed no positive sound pressure change compared to 2.3 percent of adults. This implied the existence of an immature Eustachian tube opening in preschool children compared to adults. An hypothesis was proposed that a combination of muscular activity and nasal over-pressure is responsible for the Eustachian tube opening in adults compared only to muscular activity alone in preschool children. In the adult group 33 percent of the Eustachian tube opening occurred before the muscular activity of the Eustachian tube compared to 8 percent in the preschool children. In conclusion, it appears that these experimental techniques could form the basis of a clinical diagnostic tool for Eustachian tube function.