Mucosal Surface Area Determines the Middle Ear Pressure Response Following Establishment of Sniff-Induced Underpressures

Doyle, William J.

doi:10.1080/00016489950180658

Cited by 13 publications

(12 citation statements)

References 23 publications

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“…The developed equations show that this is true only true for ears derived from a population where the tympanum/MACS ratio of effective blood perfusion (related to surface area) per unit volume, M, is less than 1. Geometrical considerations show that the surface area per unit volume ratio of the MACS is much greater than that for the tympanum, and consequently, if M<1, blood perfusion per unit surface area must be much less for the MACS when compared to the tympanum [1,14,[37][38][39].…”

Section: Discussionmentioning

confidence: 99%

“…These include active gas generation and ME pressure-buffering. While the physiological mechanism underlying MACS gas generation is not well developed [3,5,13] and experimental evidences supporting that possibility have alternative explanations [14], ME pressure-buffering is easily demonstrated. There, pressure-buffering can be decomposed into two effects, a magnitudelimiting effect on pressure change under conditions where ME cavity volume is changed (Boyle's Law) [15] and a rate-limiting effect on pressure change under conditions where the contained volume of ME gas is changed (General Gas Law) [16].…”

Section: Introductionmentioning

confidence: 99%

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The mastoid as a functional rate-limiter of middle ear pressure change

Doyle

2007

International Journal of Pediatric Otorhinolaryngology

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The mastoid as a functional rate-limiter of middle ear pressure change

Doyle

2007

International Journal of Pediatric Otorhinolaryngology

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“…Considering the above ratio and the initial partial pressure differences given in Table 2, the initial rate at which O 2 diffuses into the blood is calculated to be 4.3 times the rate at which N 2 diffuses into the ME. For CO 2 , the solubility times diffusivity product is ϳ35 times higher than that of N 2 (7,8,11,14,15,17). Taking into account the initial gradient, CO 2 is initially transported into the ME cavity at ϳ480 times the N 2 rate.…”

Section: Phase Imentioning

confidence: 99%

Role of nitrogen in transmucosal gas exchange rate in the rat middle ear

Kania¹,

Herman²,

Huy³

et al. 2006

Journal of Applied Physiology

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. Role of nitrogen in transmucosal gas exchange rate in the rat middle ear. J Appl Physiol 101: [1281][1282][1283][1284][1285][1286][1287] 2006. First published July 13, 2006; doi:10.1152/japplphysiol.00113.2006.-This study investigates the role of nitrogen (N 2) in transmucosal gas exchange of the middle ear (ME). We used an experimental rat model to measure gas volume variations in the ME cavity at constant pressure. We disturbed the steady-state gas composition with either air or N 2 to measure resulting changes in volume at ambient pressure. Changes in gas volume over time could be characterized by three phases: a primary transient increase with time (phase I), followed by a linear decrease (phase II), and then a gradual decrease (phase III). The mean slope of phase II was Ϫ0.128 l/min (SD 0.023) in the air group (n ϭ 10) and Ϫ0.105 l/min (SD 0.032) in the N 2 group (n ϭ 10), but the difference was not significant (P ϭ 0.13), which suggests that the rate of gas loss can be attributed mainly to the same steady-state partial pressure gradient of N 2 reached in this phase. Furthermore, a mathematical model was developed analyzing the transmucosal N2 exchange in phase II. The model takes gas diffusion into account, predicting that, in the absence of change in mucosal blood flow rate, gas volume in the ME should show a linear decrease with time after steady-state conditions and gas composition are established. In accordance with the experimental results, the mathematical model also suggested that transmucosal gas absorption of the rat ME during steady-state conditions is governed mainly by diffusive N2 exchange between the ME gas and its mucosal blood circulation. rat model

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“…As stated in [19], understanding the mechanism of the middle ear pressure regulation is important for both physiologists and practising clinicians; especially for the practising clinicians in their decisions on how to treat their patients. The surface area of the mucosa in the middle ear, especially the one covering the mastoid air cell system, is therefore a valuable parameter for physiological studies of gas exchanged between the air cells and the capillaries present in the mucosa lining the air cells [18,19,62].…”

Section: Forewordmentioning

confidence: 99%

Structural properties of the mastoid using image analysis and visualization

Cros¹

2017

Linköping Studies in Science and Technology. Dissertations

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Volume rendering of a 3D shape analysis where medial balls are fitting the mastoid air cell system of a human temporal bone specimen, overlaid over a manually cropped version of the original data. The different colours represent the different size classes: from very small in dark blue to vary large in purple. The bone is rendered with a modified transfer function so as to reveal the micro-channels.Copyright © 2017 Olivier Cros, unless otherwise noted. AbstractThe mastoid, located in the temporal bone, houses an air cell system whose cells have a variation in size that can go far below current conventional clinical CT scanner resolution. Therefore, the mastoid air cell system is only partially represented in a clinical CT scan. Where the conventional clinical CT scanner lacks level of minute details, micro-CT scanning provides an overwhelming amount of fine details. The temporal bone being one of the most complex in the human body, visualization of micro-CT scanning of this bone awakens the curiosity of the experimenter, especially with the correct visualization settings.This thesis first presents a statistical analysis determining the surface area to volume ratio of the mastoid air cell system of human temporal bone, from micro-CT scanning using methods previously applied for conventional clinical CT scans. The study compared current results with previous studies, with successive downsampling the data down to a resolution found in conventional clinical CT scans. The results from the statistical analysis showed that all the small mastoid air cells, that cannot be detected in conventional clinical CT scans, do heavily contribute to the estimation of the surface area, and in consequence to the estimation of the surface area to volume ratio by a factor of about 2.6. Such a result further strengthens the idea of the mastoid to play an active role in pressure regulation and gas exchange.Discovery of micro-channels through specific use of a non-traditional transfer function was then reported, where a qualitative and a quantitative preanalysis were performed and reported. To gain more knowledge about these micro-channels, a local structure tensor analysis was applied where structures are described in terms of planar, tubular, or isotropic structures. The results from this structural tensor analysis suggest these micro-channels to potentially be part of a more complex framework, which hypothetically would provide a separate blood supply for the mucosa lining the mastoid air cell system.The knowledge gained from analysing the micro-channels as locally providing blood to the mucosa, led to the consideration of how inflammation of the mucosa could impact the pneumatization of the mastoid air cell system. Though very primitive, a 3D shape analysis of the mastoid air cell system was carried out. The mastoid air cell system was first represented in a compact form through a medial axis, from which medial balls could be used. The medial balls, representative of how large the mastoid air cells can be locally, were used in two co...

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Mucosal Surface Area Determines the Middle Ear Pressure Response Following Establishment of Sniff-Induced Underpressures

Abstract: These results do not support a pressure-regulating role for the mastoid mucosa. Contrary to currently held beliefs, the model simulation suggests that small, not large mastoid volumes buffer ME pressure from rapid change due to trans-mucosal gas transfers.

Cited by 13 publications

References 23 publications

The mastoid as a functional rate-limiter of middle ear pressure change

The mastoid as a functional rate-limiter of middle ear pressure change

Role of nitrogen in transmucosal gas exchange rate in the rat middle ear

Structural properties of the mastoid using image analysis and visualization

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