Document Detail

Oscillations and noise: inherent instability of pressure support ventilation?
MedLine Citation:
PMID:  11779729     Owner:  NLM     Status:  MEDLINE    
Pressure support ventilation (PSV) is almost universally employed in the management of actively breathing ventilated patients with acute respiratory failure. In this partial support mode of ventilation, a fixed pressure is applied to the airway opening, and flow delivery is monitored by the ventilator. Inspiration is terminated when measured inspiratory flow falls below a set fraction of the peak flow rate (flow cutoff); the ventilator then cycles to a lower pressure and expiration commences. We used linear and nonlinear mathematical models to investigate the dynamic behavior of pressure support ventilation and confirmed the predicted behavior using a test lung. Our mathematical and laboratory analyses indicate that pressure support ventilation in the setting of airflow obstruction can be accompanied by marked variations in tidal volume and end-expiratory alveolar pressure, even when subject effort is unvarying. Unstable behavior was observed in the simplest plausible linear mathematical model and is an inherent consequence of the underlying dynamics of this mode of ventilation. The mechanism underlying the observed instability is "feed forward" behavior mediated by oscillatory elevation in end-expiratory pressure. In both mathematical and mechanical models, unstable behavior occurred at impedance values and ventilator settings that are clinically realistic.
John R Hotchkiss; Alexander B Adams; Mary K Stone; David J Dries; John J Marini; Philip S Crooke
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.; Validation Studies    
Journal Detail:
Title:  American journal of respiratory and critical care medicine     Volume:  165     ISSN:  1073-449X     ISO Abbreviation:  Am. J. Respir. Crit. Care Med.     Publication Date:  2002 Jan 
Date Detail:
Created Date:  2002-01-07     Completed Date:  2002-02-13     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  9421642     Medline TA:  Am J Respir Crit Care Med     Country:  United States    
Other Details:
Languages:  eng     Pagination:  47-53     Citation Subset:  AIM; IM    
Section of Pulmonary and Critical Care and Section of Surgery, Regions Hospital and University of Minnesota, St. Paul, Minnesota 55101, USA.
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MeSH Terms
Airway Resistance / physiology*
Bias (Epidemiology)
Linear Models*
Models, Biological*
Nonlinear Dynamics*
Peak Expiratory Flow Rate
Positive-Pressure Respiration* / adverse effects,  instrumentation,  methods,  standards
Positive-Pressure Respiration, Intrinsic / etiology,  physiopathology
Predictive Value of Tests
Respiratory Insufficiency / physiopathology*,  therapy
Systems Theory
Tidal Volume
Grant Support

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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