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Estimating intratidal nonlinearity of respiratory system mechanics: a model study using the enhanced gliding-SLICE method

Stefan Schumann1,5, Boris Burcza1, Christoph Haberthür2, Michael Lichtwarck-Aschoff3,4 and Josef Guttmann1

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In the clinical situation and in most research work, the analysis of respiratory system mechanics is limited to the estimation of single-value compliances during static or quasi-static conditions. In contrast, our SLICE method analyses intratidal nonlinearity under the dynamic conditions of mechanical ventilation by calculating compliance and resistance for six conjoined volume portions (slices) of the pressure–volume loop by multiple linear regression analysis. With the gliding-SLICE method we present a new approach to determine continuous intratidal nonlinear compliance. The performance of the gliding-SLICE method was tested both in computer simulations and in a physical model of the lung, both simulating different intratidal compliance profiles. Compared to the original SLICE method, the gliding-SLICE method resulted in smaller errors when calculating the compliance or pressure course (all p < 0.001) and in a significant reduction of the discontinuity error for compliance determination which was reduced from 12.7 ± 7.2 cmH2O s L−1 to 0.8 ± 0.3 cmH2O s L−1 (mathematical model) and from 7.2 ± 3.9 cmH2O s L−1 to 0.4 ± 0.2 cmH2O s L−1 (physical model) (all p < 0.001). We conclude that the new gliding-SLICE method allows detailed assessment of intratidal nonlinear respiratory system mechanics without discontinuity error.


PACS

87.80.-y Biophysical techniques (research methods)

87.19.U- Hemodynamics

47.63.Ec Pulmonary fluid mechanics

Subjects

Fluid dynamics

Instrumentation and measurement

Medical physics

Biological physics

Dates

Issue 12 (December 2009)

Received 29 May 2009, accepted for publication 2 October 2009

Published 28 October 2009



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