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Gan RZ, Nakmali D, Ji XD, Leckness K, Yokell Z. Mechanical damage of tympanic membrane in relation to impulse pressure waveform - A study in chinchillas. Hear Res 2016; 340:25-34. [PMID: 26807796 DOI: 10.1016/j.heares.2016.01.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2015] [Revised: 12/27/2015] [Accepted: 01/11/2016] [Indexed: 11/26/2022]
Abstract
Mechanical damage to middle ear components in blast exposure directly causes hearing loss, and the rupture of the tympanic membrane (TM) is the most frequent injury of the ear. However, it is unclear how the severity of injury graded by different patterns of TM rupture is related to the overpressure waveforms induced by blast waves. In the present study, the relationship between the TM rupture threshold and the impulse or overpressure waveform has been investigated in chinchillas. Two groups of animals were exposed to blast overpressure simulated in our lab under two conditions: open field and shielded with a stainless steel cup covering the animal head. Auditory brainstem response (ABR) and wideband tympanometry were measured before and after exposure to check the hearing threshold and middle ear function. Results show that waveforms recorded in the shielded case were different from those in the open field and the TM rupture threshold in the shielded case was lower than that in the open field (3.4 ± 0.7 vs. 9.1 ± 1.7 psi or 181 ± 1.6 vs. 190 ± 1.9 dB SPL). The impulse pressure energy spectra analysis of waveforms demonstrates that the shielded waveforms include greater energy at high frequencies than that of the open field waves. Finally, a 3D finite element (FE) model of the chinchilla ear was used to compute the distributions of stress in the TM and the TM displacement with impulse pressure waves. The FE model-derived change of stress in response to pressure loading in the shielded case was substantially faster than that in the open case. This finding provides the biomechanical mechanisms for blast induced TM damage in relation to overpressure waveforms. The TM rupture threshold difference between the open and shielded cases suggests that an acoustic role of helmets may exist, intensifying ear injury during blast exposure.
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Affiliation(s)
- Rong Z Gan
- School of Aerospace and Mechanical Engineering and Biomedical Engineering Center, University of Oklahoma, Norman, OK, USA.
| | - Don Nakmali
- School of Aerospace and Mechanical Engineering and Biomedical Engineering Center, University of Oklahoma, Norman, OK, USA
| | - Xiao D Ji
- School of Aerospace and Mechanical Engineering and Biomedical Engineering Center, University of Oklahoma, Norman, OK, USA
| | - Kegan Leckness
- School of Aerospace and Mechanical Engineering and Biomedical Engineering Center, University of Oklahoma, Norman, OK, USA
| | - Zachary Yokell
- School of Aerospace and Mechanical Engineering and Biomedical Engineering Center, University of Oklahoma, Norman, OK, USA
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Thom JJ, Carlson ML, Driscoll CLW, St Louis EK, Ramar K, Olson EJ, Neff BA. Middle ear pressure during sleep and the effects of continuous positive airway pressure. Am J Otolaryngol 2015; 36:173-7. [PMID: 25459311 DOI: 10.1016/j.amjoto.2014.10.024] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Revised: 10/04/2014] [Accepted: 10/13/2014] [Indexed: 11/30/2022]
Abstract
PURPOSE Prior studies evaluating Eustachian tube physiology, baseline middle ear pressure (MEP), and the effects of continuous positive airway pressure (CPAP) have been performed on awake patients. No study to date has specifically investigated MEP during sleep despite the fact that the average individual spends a third of their lifetime sleeping. The primary objectives of the current study are to quantify normal physiologic MEP during sleep and to evaluate the effects of escalating CPAP levels. MATERIALS AND METHODS Prospective observational study at a tertiary academic referral center evaluating serial tympanometry on sleeping adult patients during polysomnography. MEP was recorded awake, at 1-hour intervals during diagnostic polysomnography, and at all CPAP levels during titration. Changes in MEP with duration of sleep and escalating CPAP levels were analyzed. RESULTS Ten adults were included (4 females; 6 males; mean age 58years). The mean MEP while awake was 3 decapascals (daPa). The mean MEP during sleep without CPAP rose steadily from 14 daPa at 1hour to 41 daPa at 4hours (r=0.52; p<0.001). The mean MEP during sleep at a CPAP level of 5cm of water was 54 daPa. The mean MEP rose steadily with increasing CPAP levels, and was 104 daPa at 10cm of water, (r=0.82; p<0.001). The mean MEP during sleep without CPAP was 26 daPa, which was significantly lower than the mean MEP during sleep with CPAP between 5-10cm H2O (p<0.01). CONCLUSIONS MEP naturally increases with duration of sleep. CPAP therapy causes a supraphysiologic elevation in MEP that rises with increasing pressure levels. These findings may help guide future studies examining the safety of CPAP following otologic surgery and the potential therapeutic benefit in patients with chronic middle ear disease.
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Affiliation(s)
- Joshua J Thom
- Department of Otolaryngology, Head and Neck Surgery, Mayo Clinic School of Medicine, Rochester, MN, USA
| | - Matthew L Carlson
- Department of Otolaryngology, Head and Neck Surgery, Mayo Clinic School of Medicine, Rochester, MN, USA.
| | - Colin L W Driscoll
- Department of Otolaryngology, Head and Neck Surgery, Mayo Clinic School of Medicine, Rochester, MN, USA
| | - Erik K St Louis
- Department of Neurology and Center for Sleep Medicine, Mayo Clinic School of Medicine, Rochester, MN, USA
| | - Kannan Ramar
- Division of Pulmonary and Critical Care Medicine and Center for Sleep Medicine, Mayo Clinic School of Medicine, Rochester, MN, USA
| | - Eric J Olson
- Division of Pulmonary and Critical Care Medicine and Center for Sleep Medicine, Mayo Clinic School of Medicine, Rochester, MN, USA
| | - Brian A Neff
- Department of Otolaryngology, Head and Neck Surgery, Mayo Clinic School of Medicine, Rochester, MN, USA
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Thornton JL, Chevallier KM, Koka K, Gabbard SA, Tollin DJ. Conductive hearing loss induced by experimental middle-ear effusion in a chinchilla model reveals impaired tympanic membrane-coupled ossicular chain movement. J Assoc Res Otolaryngol 2013; 14:451-64. [PMID: 23615802 DOI: 10.1007/s10162-013-0388-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Accepted: 03/31/2013] [Indexed: 11/25/2022] Open
Abstract
Otitis media with effusion (OME) occurs when fluid collects in the middle-ear space behind the tympanic membrane (TM). As a result of this effusion, sounds can become attenuated by as much as 30-40 dB, causing a conductive hearing loss (CHL). However, the exact mechanical cause of the hearing loss remains unclear. Possible causes can include altered compliance of the TM, inefficient movement of the ossicular chain, decreased compliance of the oval window-stapes footplate complex, or altered input to the oval and round window due to conduction of sound energy through middle-ear fluid. Here, we studied the contribution of TM motion and umbo velocity to a CHL caused by middle-ear effusion. Using the chinchilla as an animal model, umbo velocity (V U) and cochlear microphonic (CM) responses were measured simultaneously using sinusoidal tone pip stimuli (125 Hz-12 kHz) before and after filling the middle ear with different volumes (0.5-2.0 mL) of silicone oil (viscosity, 3.5 Poise). Concurrent increases in CM thresholds and decreases in umbo velocity were noted after the middle ear was filled with 1.0 mL or more of fluid. Across animals, completely filling the middle ear with fluid caused 20-40-dB increases in CM thresholds and 15-35-dB attenuations in umbo velocity. Clinic-standard 226-Hz tympanometry was insensitive to fluid-associated changes in CM thresholds until virtually the entire middle-ear cavity had been filled (approximately >1.5 mL). The changes in umbo velocity, CM thresholds, and tympanometry due to experimentally induced OME suggest CHL arises primarily as a result of impaired TM mobility and TM-coupled umbo motion plus additional mechanisms within the middle ear.
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Affiliation(s)
- Jennifer L Thornton
- Department of Physiology and Biophysics, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, CO, USA
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Mechanisms of tympanic membrane and incus mobility loss in acute otitis media model of guinea pig. J Assoc Res Otolaryngol 2013; 14:295-307. [PMID: 23483330 DOI: 10.1007/s10162-013-0379-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Accepted: 02/15/2013] [Indexed: 10/27/2022] Open
Abstract
Acute otitis media (AOM) is a rapid infection of middle ear due to bacterial or viral invasion. The infection commonly leads to negative pressure and purulent effusion in the middle ear. To identify how these changes affect tympanic membrane (TM) mobility or sound transmission through the middle ear, we hypothesize that pressure, effusion, and structural changes of the middle ear are the main mechanisms of conductive hearing loss in AOM. To test the hypothesis, a guinea pig AOM model was created by injection of Streptococcus pneumoniae. Three days post inoculation, vibration of the TM at umbo in response to input sound in the ear canal was measured at three experimental stages: intact, pressure-released, and effusion-drained AOM ears. The vibration of the incus tip was also measured after the effusion was removed. Results demonstrate that displacement of the TM increased mainly at low frequencies when pressure was released. As the effusion was removed, the TM mobility increased further but did not reach the level of the normal ear at low frequencies. This was caused by middle ear structural changes or adhesions on ossicles in AOM. The structural changes also affected movement of the incus at low and high frequencies. The results provide new evidence for understanding the mechanism of conductive hearing loss in AOM.
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Hoffstetter M, Lugauer F, Kundu S, Wacker S, Perea-Saveedra H, Lenarz T, Hoffstetter P, Schreyer AG, Wintermantel E. Middle ear of human and pig: a comparison of structures and mechanics. ACTA ACUST UNITED AC 2012; 56:159-65. [PMID: 21657989 DOI: 10.1515/bmt.2011.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
INTRODUCTION Animal studies are an essential method to evaluate implants for the middle ear prior to clinical studies. New Zealand rabbits, guinea pigs and chinchillas are, among other small mammals, well established animal models, but their auditory system is significantly smaller compared to human. Hence, the suitability of the domestic pig (sus scrofa domesticus) as a new animal model for research on the middle ear (ME), that would match the human in size, was investigated. METHODS Thirty halved pig heads were obtained from the butcher and each middle ear was dissected. Using a digital light microscope, several anatomical magnitudes were determined for 24 specimens, namely the planar projected area of the tympanic membrane (TM), in relation to the stapes footplate as well as the dimensions and weight of the ossicles, in order to determine the effective lever ratios. Using normal and micro computed tomography (CT), six porcine temporal bones were scanned and the geometric data obtained were transferred into a finite element model (FEM) simulation of the porcine middle ear. The transfer function was determined and compared to those from humans determined by measurements and simulations, respectively. RESULTS The anatomy investigated presented itself as highly comparable to that of the human. Differing from literature, no fourth ossicle could be found. The porcine dimensions and lever ratios determined match the humans far better than those of all established animal models. The obtained transfer function was congruent to the human one. This underlines the suitability of the pig as an animal model for middle ear implants.
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Affiliation(s)
- Marc Hoffstetter
- Department and Chair for Medical Engineering, Technische Universität München, Munich, Germany.
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Guan X, Gan RZ. Effect of middle ear fluid on sound transmission and auditory brainstem response in guinea pigs. Hear Res 2011; 277:96-106. [PMID: 21414396 DOI: 10.1016/j.heares.2011.03.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Revised: 02/16/2011] [Accepted: 03/07/2011] [Indexed: 11/30/2022]
Abstract
Combined measurements of middle ear transfer function and auditory brainstem response (ABR) in live guinea pigs with middle ear effusion (MEE) are reported in this paper. The MEE model was created by injecting saline into the middle ear cavity. Vibrations of the tympanic membrane (TM), the tip of the incus, and the round window membrane (RWM) were measured with a laser vibrometer at frequencies of 0.2-40 kHz when the middle ear fluid increased from 0 to 0.2 ml (i.e., full fill of the cavity). The click and pure tone ABRs were recorded as the middle ear fluid increased. Fluid introduction reduced mobility of the TM, incus and RWM mainly at high frequencies (f > 1 kHz). The magnitude of this reduction was related to the volume of fluid. The displacement transmission ratio of the TM to incus varied with frequency and fluid level. The volume displacement ratio of the oval window to round window was approximately 1.0 over most frequencies. Elevation of ABR thresholds and prolongation of ABR latencies were observed as fluid level increased. Reduction of TM displacement correlated well with elevation of ABR threshold at 0.5-8 kHz. Alterations in the ratio of ossicular displacements before and after fluid induction are consistent with fluid-induced changes in complex ossicular motions.
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Affiliation(s)
- Xiying Guan
- School of Aerospace and Mechanical Engineering and Bioengineering Center, University of Oklahoma, 865 Asp Avenue, Room 200, Norman, OK 73019, USA
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Petrova P, Freeman S, Sohmer H. Mechanism and Rate of Middle Ear Fluid Absorption. ACTA ACUST UNITED AC 2007; 12:155-9. [PMID: 17259701 DOI: 10.1159/000099017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2005] [Accepted: 09/27/2006] [Indexed: 11/19/2022]
Abstract
Several mechanisms have been suggested to explain the clearance of fluids from the middle ear. These include a pumping action through the eustachian tube, mucociliary beating through the tube, outflow of water to the blood due to osmotic gradients and an active Na(+) transport driving water absorption. In order to assess these mechanisms, the middle ear cavity of paralyzed, ventilated (eustachian tube occluded) guinea pigs was filled with fluids varying in osmotic pressure (hypotonic, isotonic, hypertonic) to which a vertical tube was attached. The change in height of fluid in the tube was taken as a measure of changes in middle ear fluid volume. A greater fluid volume reduction was seen with the hypotonic (1/5 saline) solution. A small volume increase was observed with the hypertonic solution. These results provide evidence that in these experimental conditions, water absorption due to osmotic gradients can contribute to middle ear fluid clearance.
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Affiliation(s)
- Petia Petrova
- Department of Otolaryngology, Head and Neck Surgery, Hadassah University Hospital, Jerusalem, Israel
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Gan RZ, Dai C, Wood MW. Laser interferometry measurements of middle ear fluid and pressure effects on sound transmission. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2006; 120:3799-810. [PMID: 17225407 DOI: 10.1121/1.2372454] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
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.
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Affiliation(s)
- Rong Z Gan
- School of Aerospace and Mechanical Engineering and Bioengineering Center; University of Oklahoma, Norman, Oklahoma 73019, USA.
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