Biomedical Engineering Reference
In-Depth Information
Fig. 7.17 The real part of impedance R 6 evaluated at 6 Hz against the height in healthy ( square ),
asthma before bronchial challenge ( triangle ) and asthma after bronchial challenge ( crosses ). Pre-
dicted values for R 6 from [ 33 ]( diamond )
Fig. 7.18
The percent ratios FEV 1 /VC %( diamond )and FEF/VC %( square ) against height
Fig. 7.19 Impedance plots
for the healthy children group
QF 6 and the power factor PF 6aregiveninFig. 7.24 . Finally, the boxplots for the
real part of impedance R 6 and resonant frequency η r are given in Fig. 7.25 .
There were no significantly different values obtained between the groups for the
hysteresivity η r ( p< 0 . 41), perhaps due to prior medication of the asthmatic group.
Indeed, in lung tissues, the frictional stress is almost invariably between 0.1 and 0.2
of the elastic stress, a fraction known as hysteresivity. This means that for each unit
of peak elastic strain energy that is stored during a cyclic deformation, 10 to 20 %
of that energy is lost irreversibly to heat. This fixed relationship holds at the level of
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