Biomedical subjects

Mark W Wood

Publications and source records attributed to Mark W Wood.

5 recordsLinked to original sources

PubMed2006

Laser interferometry measurements of middle ear fluid and pressure effects on sound transmission.

An otitis media with effusion model in human temporal bones with two laser vibrometers was created in this study. By measuring the displacement of the stapes from the medial side of the footplate, the transfer function of the middle ear, which is defined as the displacement transmission ratio (DTR) of the tympanic membrane to footplate, was derived under different middle ear pressure and fluid in the cavity with a correction factor for cochlear load. The results suggest that the DTR increases with increasing frequency up to 4k Hz when the middle ear pressure was changing from 0 to 20 or -20 cm H20 (e.g., +/-196 daPa) and fluid level was increasing from 0 to a full middle ear cavity. The positive and negative pressures show different effects on the DTR. The effect of fluid on DTR varies between three frequency ranges: f < 1k, between 1k and 4k, and f > 4k Hz. These findings show how the efficiency of the middle ear system for sound transmission changes during the presence of fluid in the cavity and variations of middle ear pressure.

Bone Conduction↗

PubMed2005

Acoustic-structural coupled finite element analysis for sound transmission in human ear--pressure distributions.

A three-dimensional (3D) finite element (FE) model of human ear with accurate structural geometry of the external ear canal, tympanic membrane (TM), ossicles, middle ear suspensory ligaments, and middle ear cavity has been recently reported by our group. In present study, this 3D FE model was modified to include acoustic-structural interfaces for coupled analysis from the ear canal through the TM to middle ear cavity. Pressure distributions in the canal and middle ear cavity at different frequencies were computed under input sound pressure applied at different locations in the canal. The spectral distributions of middle ear pressure at the oval window, round window, and medial site of the umbo were calculated and the results demonstrated that there was no significant difference of pressures between those locations at frequency below 3.5 kHz. Finally, the influence of TM perforation on pressure distributions in the canal and middle ear cavity was investigated for perforations in the inferior-posterior and inferior sites of the TM in the FE model and human temporal bones. The results show that variation of middle ear pressure is related to the perforation type and location, and is sensitive to frequency.

Acoustic Stimulation↗

PubMed2004

Human middle ear transfer function measured by double laser interferometry system.

HYPOTHESIS: Simultaneous measurements of vibrations on the stapes footplate, incudostapedial (IS) joint, and tympanic membrane (TM) can be made in both normal and drained cochleae, and the stapes displacement transfer function (S-DTF) and TM displacement transfer function (TM-DTF) are derived. BACKGROUND: A single laser Doppler interferometer previously has been used for measuring movement of the stapes or TM in temporal bones. However, there may be a limitation to optimally describing acoustic-mechanical transmission when the interferometer and temporal bone are moved frequently during experimental recordings. Simultaneous measurements of vibrations of the TM and stapes footplate, or TM and IS joint may reveal different acoustic-mechanical characteristics of the middle ear. METHODS: Dual laser interferometers simultaneously measured vibrations of the TM, IS joint, and stapes in 10 temporal bones with both intact and drained cochleae. From these measurements, the middle ear transfer function was expressed as the S-DTF, TM-DTF, and displacement transmission ratio (DTR). RESULTS: Simultaneous displacements of the TM, IS joint, and stapes footplate induced by sound pressure in the ear canal were recorded in both amplitude and phase. The middle ear transfer functions in terms of displacement ratio confirmed published single interferometer data but provided new information from drained cochlea. CONCLUSION: Stapes and TM displacement transfer functions were determined using dual interferometry, provided accurate amplitude and phase relationships from stapes footplate, IS joint, and TM, with new data from drained and normal cochlea.

Acoustic Stimulation↗

PubMed2002

Middle ear electromagnetic semi-implantable hearing device: results of the phase II SOUNDTEC direct system clinical trial.

OBJECTIVE: To assess the safety and efficacy of the SOUNDTEC Direct System, a partially implantable electromagnetic middle ear hearing device. STUDY DESIGN: Food and Drug Administration Phase II clinical trial of 103 patients at 10 sites across the United States. SETTING: Tertiary referral medical centers. PATIENTS: Individuals with bilateral moderate to moderately severe sensorineural hearing impairment who had worn optimally fit hearing aids for at least 45 days. INTERVENTIONS: Therapeutic intervention included implantation of a 27-mg neodymium iron boron magnet encased in a laser-welded titanium canister onto the incudostapedial joint, followed, after a 10-week healing period, by fitting with a deep earmold coil assembly and activation of the sound processor. MAIN OUTCOME MEASURES: Functional gain, speech recognition in quiet and noise, articulation index scores, perceived aided benefit, sound quality judgments, satisfaction, and presence of feedback and occlusion with the Direct System were compared with those of the patients' optimally fit hearing aid. RESULTS: The results of this multicenter clinical trial were submitted to the Food and Drug Administration on April 13, 2001, and are presented here. The results with the use of the SOUNDTEC Direct System compared with an optimally fit hearing aid provided an average 7.9-dB increase in functional gain in the speech frequencies (500-4,000 Hz) and a 9.6 dB gain in high frequencies (2,000, 3,000, and 4,000 Hz). There was a statistically significant average increase of 5.3% in speech discrimination. The mean speech perception in noise test score was improved, but the improvement was not statistically significant. Subjective tests using abbreviated profile of hearing aid benefit and the Hough Ear Institute Profile demonstrated scores statistically improved over the hearing aid condition. These subjective tests measured areas such as the presence of occlusion and feedback, speech quality judgments, device preference, and perceived aided benefit. CONCLUSIONS: The results of this Phase II clinical trial demonstrate that the SOUNDTEC Direct System provided statistically significant reduction in feedback and occlusive effect as well as a statistically significant improvement in all the following categories: functional gain, articulation index scores, speech discrimination in quiet, perceived aided benefit, patient satisfaction and device preference over the patient's optimally fit hearing aid.

Adult↗

PubMed2002

Homograft microlathed femur prosthesis in stapedectomy.

The use of homografts in ossiculoplasty has been well documented in the literature. In the early 1980s, nonossicular homograft otic capsule bone was used as a prosthetic material in stapedectomy. We began using homograft femur as a prosthetic material in the early 1990s. In this article, we report the results of a retrospective study of the use of homograft femur prostheses. A series of 300 stapedectomies was performed between Aug. 24, 1992, and Jan. 20, 2000. Total footplate removal with preservation of the posterior crus was our procedure of choice. However, in 116 of these cases, the posterior crus could not be used, and a homograft femur prosthesis was substituted. For these prostheses, all homograft femurs were obtained from the American Red Cross. All prostheses were prepared in the bone laboratory and stored in the bone bank until needed. After an adequate period of follow-up, we tabulated our results. We found that in 89 of 113 cases (78.8%) available for follow-up, the air-bone gap was completely closed. In addition, the air-bone gap was closed to within 5 dB in 11 patients (9.7%) and closed to within 10 dB in five patients (4.4%). In all, 105 of the 113 homograft femur prosthetic procedures (92.9%) resulted in a successful outcome.

Bioprosthesis↗