TAILIEUCHUNG - Recent Advances in Biomedical Engineering 2011 Part 11

Tham khảo tài liệu 'recent advances in biomedical engineering 2011 part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Fractional-Order Models for the Input Impedance of the Respiratory System 389 Fig. 4. A healthy subject data evaluated with FO4 left and with FO2 right continuous lines denote the measured impedance and dashed lines denote the identified impedance. 3 2 1 0 1 Fig. 5. Tissue damping G kPa l with FO2 p 3e-5 left and with FO4 p 1e-8 right 1 Healthy subjects and 2 COPD patients. Fig. 6. Tissue elastance H kPa l with FO2 p left and with FO4 p right 1 Healthy subjects and 2 COPD patients. 390 Recent Advances in Biomedical Engineering 2 1 0 2 2 Fig. 7. Tissue hysteresivity n with FO2 p left and with FO4 p right 1 Healthy subjects and 2 COPD patients. Figures 5 6 and 7 depict the boxplots for the FO2 and FO4 for the tissue damping G tissue elastance H and histeresivity n. Due to the fact that FO2 has higher errors in fitting the impedance values the results are no further discussed. Although a similarity exists between the values given by the two models the discussion will be focused on the results obtained using FO4. Because FO are natural solutions in dielectric materials it is interesting to look at the permittivity property of respiratory tissues. In electric engineering it is common to relate permittivity to a material s ability to transmit or permit an electric field. By electrical analogy changes in trans-respiratory pressure relate to voltage difference and changes in air-flow relate to electrical current flows. When analyzing the permittivity index one may refer to an increased permittivity when the same amount of air-displacement is achieved with smaller pressure difference. In other words the hysteresivity coefficient incorporates this property for the capacitor that is the COPD group has an increased capacitance justified by the pathology of the disease. Many alveolar walls are lost by emphysematous lung destruction the lungs become so loose and floppy that a small change in pressure is enough to maintain a

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