Volume dependence of respiratory system resistance during artificial ventilation in rabbits

The volume dependence of respiratory resistance (Rrs), usually observed during normal breathing, is expected to be accentuated during expiratory flow limitation (EFL). In order to quantify this dependence we studied the pressure, flow, and volume data obtained from eight New Zealand rabbits, artific...

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Bibliographic Details
Published in:Intensive care medicine 2001-05, Vol.27 (5), p.898-904
Main Authors: VASSILIOU, M, SAUNIER, C, DUVIVIER, C, BEHRAKIS, P, PESLIN, R
Format: Article
Language:English
Subjects:
Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy
Animals
Biological and medical sciences
Emergency and intensive respiratory care
Forced Expiratory Flow Rates
Histamine
Intensive care medicine
Linear Models
Lung Compliance
Medical sciences
Models, Animal
Rabbits
Respiration, Artificial - methods
Respiratory Physiological Phenomena
Respiratory system
Ventilators
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Summary:The volume dependence of respiratory resistance (Rrs), usually observed during normal breathing, is expected to be accentuated during expiratory flow limitation (EFL). In order to quantify this dependence we studied the pressure, flow, and volume data obtained from eight New Zealand rabbits, artificially ventilated at different levels of applied expiratory pressure (0-10 hPa), before and during histamine i. v. infusion. EFL was provoked by lowering the expiratory pressure and was detected by the application of an additional negative expiratory pressure and by forced oscillations. The analysis of respiratory system mechanics was performed by multiple regression, using the classical linear first-order model and also a nonlinear model, accounting for volume dependence of Rrs. Both models satisfactorily fitted the data in the absence of EFL. The nonlinear model proved to be more appropriate in the presence of EFL. The coefficient expressing the volume dependence of Rrs (Rvd) was significantly more negative during EFL. Rvd values were highly correlated with the fraction of the tidal volume left to be expired at the onset of EFL. A threshold Rvd value of -1,000 (hPa x s x l(-2)) detected EFL with high sensitivity and specificity. We conclude that a strongly negative volume dependence of Rrs is a reliable and noninvasive index of EFL during artificial ventilation.
ISSN:0342-4642
1432-1238
DOI:10.1007/s001340100939