Document Detail

Assessment of neural inspiratory time in ventilator-supported patients.
MedLine Citation:
PMID:  10934085     Owner:  NLM     Status:  MEDLINE    
Neural inspiratory time (TI) is a measurement of fundamental importance in studies of patient-ventilator interaction. The measurement is usually based on recordings of flow, esophageal pressure (Pes), and transdiaphragmatic pressure (Pdi), but the concordance of such estimates of neural TI with a more direct measurement of neural activity has not been systematically evaluated. To address this issue, we studied nine ventilator-supported patients in whom we employed esophageal electrode recordings of the diaphragmatic electromyogram (EMG) as the reference measurement of neural TI. Comparison of the indirect estimates of neural TI duration, based on flow, Pes, and Pdi against the reference measurement, revealed a mean difference (bias) ranging from -54 to 612 ms during spontaneous breathing and from -52 to 714 ms during mechanical ventilation; the respective precisions (standard deviations of the differences) ranged from 79 to 175 ms and from 74 to 221 ms. Because an indirect estimate of neural TI duration could be identical to that of the reference measurement and yet be displaced in time, this lag or lead was quantified as the phase angle of neural TI onset. Flow-based estimates of the onset of neural TI displayed a systematic lag, which may be explained at least in part by concurrent intrinsic positive end-expiratory pressure. In conclusion, the indirect estimates of the onset and duration of neural TI in ventilator-dependent patients displayed poor agreement with the diaphragmatic EMG measurement of neural TI.
S Parthasarathy; A Jubran; M J Tobin
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  American journal of respiratory and critical care medicine     Volume:  162     ISSN:  1073-449X     ISO Abbreviation:  Am. J. Respir. Crit. Care Med.     Publication Date:  2000 Aug 
Date Detail:
Created Date:  2000-09-15     Completed Date:  2000-09-15     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9421642     Medline TA:  Am J Respir Crit Care Med     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  546-52     Citation Subset:  AIM; IM    
Division of Pulmonary and Critical Care Medicine, Edward Hines Jr., Veterans Affairs Hospital, Loyola University of Chicago Stritch School of Medicine, Hines, Illinois, USA.
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MeSH Terms
Aged, 80 and over
Esophagus / physiology*
Middle Aged
Positive-Pressure Respiration
Respiration, Artificial*
Respiratory Mechanics / physiology*
Thorax / physiology

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

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