HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 98/1/114    most recent 00203.2004v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Kanick, S. C. Articles by Federspiel, W. J. Search for Related Content PubMed PubMed Citation Articles by Kanick, S. C. Articles by Federspiel, W. J.

On morphometric measurement of oxygen diffusing capacity in middle ear gas exchange

¹Department of Pediatric Otolaryngology, Children's Hospital of Pittsburgh; ²Department of Chemical and Petroleum Engineering, University of Pittsburgh; and ³Department of Otolaryngology, University of Pittsburgh School of Medicine, Pittsburgh; ⁴Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem; and ⁵McGowan Institute for Regenerative Medicine, Pittsburgh, Pennsylvania

Submitted 25 February 2004 ; accepted in final form 10 August 2004

An accurate mathematical model of transmucosal gas exchange is prerequisite to understanding middle ear (ME) physiology. Current models require experimentally measured gas species time constants for all extant conditions as input parameters. However, studies on pulmonary gas exchange have shown that a morphometric model that incorporates more fundamental physiochemical and anatomic parameters accurately simulates transport from which the species time constants can be derived for all extant conditions. Here, we implemented a variant of that model for ME gas exchange that requires the measurement of diffusional length () for the ME mucosa. That measure contributes to the mucosal diffusing capacity and reflects the resistance to gas flow between air space and capillary. Two methods for measuring have been proposed: linear distance between the air-mucosal boundary and capillary and the harmonic mean of all contributing pathway lengths. Oxygen diffusing capacity was calculated for different ME mucosal geometries by using the two measures, and the results were compared with those predicted by a detailed, two-dimensional finite element analysis. Predictive accuracy was improved by incorporating the harmonic measure, which captures important information regarding variations in capillary shape and distribution. However, compared with the oxygen diffusing capacity derived from the finite element analysis, both measures yielded nonlinear, positively biased estimates. The morphometric techniques underestimate diffusion length by failing to account for the curvilinear gas flow pathways predicted by the finite element model.

diffusion length; mathematical model; finite element analysis