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Biomedical subjects

T H Lesser

Publications and source records attributed to T H Lesser.

36 records · Page 2Linked to original sources
PubMed1990

A finite element analysis of the natural frequencies of vibration of the human tympanic membrane. Part I.

The present work examines the natural frequencies of vibration of the decoupled human tympanic membrane using the finite element method. A model comprising 49 isoparametric semi-loof thin shell elements was built, based on shape measurements of Kirikae (1960) and our own measurements on several local cadaver ears. A range of material data input was used similar to that assessed earlier by Funnell and Laszlo (1978). The present results indicate the natural vibration mode shapes are simple at low frequencies, but become more complex at higher values as found earlier (Tonndorf and Khanna, 1972; Funnell and Laszlo, 1978), but at reduced frequencies. Data input of the real drum thickenesses and dimensions considerably increases the natural frequencies by about 50% above those for a uniformly thick membrane. It is suggested that realistic eardrum natural frequencies may result from the use of a membrane internal stress parameter in the data file in order to simulate the interplay between radial and circular fibres resulting in the observed drum curvature.

Ear, Middle↗
PubMed1989

Changing incidence of sinus infection in children.

This study presents the results of a 20 year review of maxillary sinus wash-outs performed on children. The results show a decreasing incidence of purulent sinusitis over the study period. Only 17 per cent of antral wash-outs undertaken yielded pus, indicating that surgical practice has failed to adequately take account of the changing disease incidence.

Adolescent↗
PubMed1989

Altered laryngeal function following thyroidectomy.

The laryngograph was used to record and compare the voice changes in 11 thyroidectomy patients and 14 controls. The frequency histogram was studied and the change in its spread following surgery used to identify abnormal vocal fold movements due to recurrent laryngeal nerve damage. It also demonstrated changes which occur in thyroidectomy patients and not in patients having other operations. The possible causes include external laryngeal nerve damage.

Adult↗
PubMed1989

Fish bones in the throat.

Patients presenting with sharp pain in their throat after eating fish were studied to determine the site and frequency of impacted fish bones. In 79% no fish bone was demonstrated despite careful follow up. In those proven to have a fish bone 93% were in the oropharynx. The role of X-rays and the indications for referral for endoscopy are discussed.

Animals↗
PubMed1988

The tympanic membrane in cross section: a finite element analysis.

This paper applies the technique of finite element analysis to the tympanic membrane. A two-dimensional cross-sectional model of the tympanic membrane and malleus is described. A variety of experiments have been performed on this model, and the displacements under a uniform load are analysed. The shape of the displaced membrane and the movement of the umbo were found to be sensitive to a number of factors. These include the elastic modulus of the membrane, the presence and position of the axis or rotation of the malleus, and the size of the pars flaccida. Some implications of these results are discussed.

Humans↗
PubMed1988

A 15 year follow-up of a controlled trial of the use of grommets in glue ear.

The long-term natural history of secretory otitis media and the changes induced in the middle ear following grommet insertion are of importance. We report the results 15 years following the unilateral insertion of a Shepard grommet and adenoidectomy for bilateral secretory otitis media. The results suggest that grommets do not protect against attic disease of late onset and induce atrophic scars which do not resolve. Grommets confer no long-term advantages to the hearing when used in the management of childhood secretory otitis media.

Acoustic Impedance Tests↗
PubMed1988

Tympanosclerosis, grommets and shear stresses.

This paper deals with grommet induced tympanosclerosis. In the first part, patients from a controlled trial of the treatment of bilateral glue ear using unilateral grommet insertion are reviewed 15 years later. Tympanosclerosis due to grommet insertion is summated using computer graphics. Two areas of maximal tympanosclerosis are found, anteriorly and posteriorly midway between the annulus and the umbo. These maximal areas join inferiorly in the classical horse shoe shape. In an attempt to identify reasons for this distribution, the structure of the lamina propria is reviewed, and the changes that occur in tympanosclerosis considered. With this in mind, the tympanic membrane is modelled using finite element methodology to determine the areas of maximal shear stresses. These are found to be in the same position as tympanosclerosis. Such stresses would be increased by the weight of a grommet in situ. These stresses will damage the fibrils interconnecting between the fibrous layers of the lamina propria and this may lead to tympanosclerosis. This raises the question of whether a lighter grommet would decrease the incidence of grommet-induced tympanosclerosis.

Ear, Middle↗
PubMed1988

Tympanoplasty surgery and prophylactic antibiotics: surgical results.

This paper reports a multicentre, controlled, blind, prospective, randomized study into the use of prophylactic systemic antibiotics in myringoplasty surgery. A total of 130 individuals were randomly allocated to either an antibiotic or a non-antibiotic group. Each individual was clinically and audiometrically assessed preoperatively, and 8 weeks postoperatively. It was found that systemic prophylactic antibiotics did not influence either the success rate of myringoplasty surgery or the audiometric result.

Adolescent↗
PubMed1988

Intubation trauma: a comparison of two different endotracheal tubes.

In recent years endotracheal tubes with low pressure cuffs have become available with the aim of reducing trauma to the trachea and larynx. This paper uses laryngographic methods to analyse intubation trauma in 20 short to medium term intubations. No difference in laryngeal trauma was found between low pressure, large diameter cuffs when compared to standard cuffs.

Adolescent↗
PubMed1987

Laryngeal trauma vs length of intubation.

The frequency histograms of six patients' laryngographs were studied pre- and post-endotracheal intubation. The changes were correlated with the length of intubation. The post-operative hoarse voice was seen as an increase in the spread of the lower frequencies, and an increase in the fundamental frequency. The latter change was thought to be a subconscious compensation for the hoarseness. The increased lower frequency spread as measured by standard deviation was directly proportional to the length of intubation.

Adolescent↗
PubMed1987

Systemic antibiotic prophylaxis and reconstructive ear surgery.

This paper reports a multicentre, controlled, blind, prospective, randomized study into the use of prophylactic systemic antibiotics in myringoplasty surgery. Seventy-one individuals were clinically and bacteriologically assessed both preoperatively, and for a period of 8 weeks postoperatively. The results showed that antibiotic prophylaxis did not eradicate bacterial pathogens already present in preoperative ears, nor did it prevent their development during the postoperative period. The observation that an ear was wet or dry gave no indication of the actual presence or absence of pathogenic organisms.

Ampicillin↗
PubMed1986

The role of radiography in the management of nasal fractures.

The role of radiographs in the management of nasal fractures is assessed. The injury is common and the total cost of radiographs significant. A retrospective study concluded that radiographs were not definitive in the management of nasal fractures. This prompted a prospective study, in which 54 patients were assessed clinically, radiologically and under anaesthesia. At each stage they were grouped into treatment and pathological categories and the contribution of each type of assessment studied. Radiographs were not found to be useful in the routine management of nasal fractures.

Fracture Fixation↗
PubMed1986

Efficacy of medical treatment as an adjunct to surgery in the treatment of secretory otitis media.

In a pilot controlled randomised trial of 38 children who had bilateral secretory otitis media, with effusion demonstrated at operation, we compared the efficacy of a six-week course of an oral decongestant--antihistamine combination and a mucolytic preparation with a control group in preventing the presence of middle-ear effusion six weeks after myringotomy and adenoidectomy. The mucolytic preparation decreased the presence of middle-ear effusion when compared to the decongestant-antihistamine combination and the control group (p = 0.06).

Adenoidectomy↗
PubMed1986

Day case surgery in otolaryngology: a 10-year analysis.

This paper analyses the ENT day case surgery performed over the period May 1974 to May 1984 in Cardiff. The patients undergoing such surgery, the types of surgery, forms of anaesthesia, travelling considerations, seasonal variation and admission rate are examined. The problems of list organization, patient selection and attendance are examined in detail in a 12-month period from May 1981 to May 1982.

Adolescent↗
PubMed1985

Pseudotumoral mycobacterial infection in the head and neck: a clinical study.

The clinical aspects of mycobacterial infection of the head and neck are considered as presenting in patients at a cancer hospital over the last 15 years. Some difficulties in diagnosis with respect to the evolution of tuberculosis in this region are discussed. A total of 32 patients with evidence of infection were identified. Twenty-six of these with cervical lymphadenopathy are considered as a group; their clinical features and diagnosis are summarized and a note made of the recent change in the macroscopic quality of the nodes removed. Six cases are given particular attention: two with laryngeal tuberculosis, two with nasal or adenoidal infection and two with atypical mycobacterial infection diagnosed on clinical grounds.

Adolescent↗
PubMedDate not supplied

Implantable hearing aids: changes in the auditory-evoked potential of the monkey in response to increased loading of the stapes.

This study examines the effects on the hearing response in the monkey resulting from an increasing load on the stapes exerted by an implantable middle ear transducer. The transducer was placed on the distal end portion of the long process of the incus in monkeys and progressively advanced in small increments in the direction of the long axis of the stapes. Auditory-evoked potentials were recorded to assess the hearing response induced by the vibration of the transducer at each point. A decrease in response equivalent to a change in stimulus sound pressure level of approximately 20 dB occurred as the load on the stapes increased. Frequency response may also change. Our results imply that, to achieve maximum efficiency, the load placed on the ossicles by a vibrating transducer must be minimized.

Animals↗
PubMedDate not supplied

Totally implantable hearing aids: the effects of skin thickness on microphone function.

With the advent of totally implantable hearing aids, the question of the impact of the choice of implantation site on microphone function has yet to be fully addressed. We investigated the effects of skin thickness on microphone function over a 2-week period in a porcine model. Sound attenuation was found to be directly proportional to skin thickness within the range of 0.5 to 3.0 mm. A decrease in resonant frequency of 500 Hz was noted after implantation under a skin thickness of 3.0 mm. The general shape of the frequency response curves was maintained across all thicknesses tested. Attenuation (dB loss) across the range of 500 to 8,000 Hz appeared to be linear over the various skin thicknesses measured, with a regression coefficient (r = .99 at 1 kHz and r = .99 at 3 kHz). To minimize attenuation and exploit the sound-collecting qualities of the external ear, the deep meatal skin appears to be a favorable position for implantation.

Animals↗