Optimum ventilator waveform for the estimation of respiratory impedance: An animal study

Z. Hantos, F. Petak, A. Adamicza, B. Daroczy, B. Suki, K. R. Lutchen

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Abstract

The aim of this study was to estimate respiratory mechanical parameters from broad-band impedance data with an alternative method of artificial respiration. In six anaesthetized and paralysed rabbits, body surface ventilation was maintained with either conventional mechanical ventilation (CMV), or a linear motor pump driven by an optimum ventilator waveform (OVW) signal. The frequency components of the latter were selected from relative prime numbers, and neither the sum of nor the difference between any two components coincided with an existing component. The lowest-frequency component (0.469 Hz) was the major factor of adequate tidal ventilation, and there was sufficient energy at higher frequencies up to 20 Hz. Total respiratory, pulmonary and chest wall impedances were measured during CMV, and with two amplitudes of OVW. In three rabbits, small-amplitude forced oscillations (SAO) with two amplitudes were also applied during apnoeic periods at end-expiration. Due to the spectral properties of the respirator signal, the CMV measurements could be evaluated only in terms of single- frequency resistance and elastance. In contrast, both OVW and SAO resulted in broad-band impedance data that were suitable for fitting by a four-parameter model, including Newtonian resistance, inertance, and tissue damping and elastance. The parameter values were realistic in most cases, and among their changes between the small and large excursions the marked fall in tissue parameters was the most apparent. We conclude that OVW can minimize the biasing effects of nonlinear harmonic production and cross-talk, and from the OVW impedance data reliable parameters characterizing the linear subsystem during tidal excursions can be derived.

Original languageEnglish
Pages (from-to)191-197
Number of pages7
JournalEuropean Respiratory Review
Volume4
Issue number19
Publication statusPublished - Jan 1 1994

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ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine

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