ISSN:
1573-9686
Keywords:
Crosstalk
;
Hammerstein model
;
Wiener model
;
Lung tissue mechanics
;
Bronchoconstriction
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
,
Technology
Notes:
Abstract We present a simple index, extended harmonic distortion (k d ), to represent the degree of system nonlinearity under sparse pseudorandom noise inputs (SPRN). The frequencies in a SPRN waveform are neither harmonics nor sums or differences of the other component frequencies. Expressed by percentage, the k d is the square root of the ratio of output power at non-input frequencies to the total output power. We evoke three simple corrections to recover the true k d under imperfect SPRN inputs. Simulations on two block-structured nonlinear models (Wiener and Hammerstein) demonstrate the necessity and effectiveness of these corrections especially for the Wiener-type nonlinearity. By applying k d to pressure-flow data of dog lungs, we found that the nonlinear harmonic interactions from a lung arise primarily from its tissues most likely the processes governing the tissue stiffness. This nonlinearity, assessed from k d , is stronger at higher tidal volumes and enhanced (but to a lesser degree) during bronchoconstriction. We conclude that since the k d approach avoids the necessity for multiple-input measurements and lengthy data records, it may be useful for tracking the dynamic variations in nonlinearities of a physiological system.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00000013
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