Accuracy of CO2 conductance predicted using a morphometric model of the middle ear mucosa

These results hold promise that morphometric analysis can be used to generate transMEM (middle ear mucosa) gas conductance estimates for MEM geometries representative of the shift from healthy to pathologic states (e.g. increased MEM thickness and capillary density).

Novel strategies to treat otitis media with effusion require a better understanding of how MEM geometry affects gas transport. Earlier studies developed techniques to empirically measure transMEM gas conductance and to estimate conductance using morphometric models of MEM geometry. We used chinchillas to determine the correspondence between experimentally measured transMEM CO2 conductance and that predicted by morphometric study of the MEM.

TransMEM CO2 conductance was measured unilaterally in 10 chinchillas; the animals were killed and the ME was removed and processed for morphometric analyses of MEM geometry.

The average measured and estimated transMEM CO2 conductances were 4.87+/-2.30 x 10-10 and 1.75+/-0.29 x 10-10 mol/s/mmHg, respectively. The magnitude and direction of the estimate error were similar for all ears, suggesting a fixed, negative bias to the estimate. A theoretically consistent source for this bias was identified as the representation of the true diffusional length within a 3-D geometry using a 2-D modeling platform. Best estimate correction for this effect based on available data significantly reduced the estimate bias.