Document Detail

The effects of positive end-expiratory pressure on respiratory system mechanics and hemodynamics in postoperative cardiac surgery patients.
MedLine Citation:
PMID:  10625872     Owner:  NLM     Status:  MEDLINE    
We prospectively evaluated the effects of positive end-expiratory pressure (PEEP) on the respiratory mechanical properties and hemodynamics of 10 postoperative adult cardiac patients undergoing mechanical ventilation while still anesthetized and paralyzed. The respiratory mechanics was evaluated by the inflation inspiratory occlusion method and hemodynamics by conventional methods. Each patient was randomized to a different level of PEEP (5, 10 and 15 cmH2O), while zero end-expiratory pressure (ZEEP) was established as control. PEEP of 15-min duration was applied at 20-min intervals. The frequency dependence of resistance and the viscoelastic properties and elastance of the respiratory system were evaluated together with hemodynamic and respiratory indexes. We observed a significant decrease in total airway resistance (13.12 +/- 0.79 cmH2O l-1 s-1 at ZEEP, 11.94 +/- 0.55 cmH2O l-1 s-1 (P<0.0197) at 5 cmH2O of PEEP, 11.42 +/- 0.71 cmH2O l-1 s-1 (P<0.0255) at 10 cmH2O of PEEP, and 10.32 +/- 0.57 cmH2O l-1 s-1 (P<0.0002) at 15 cmH2O of PEEP). The elastance (Ers; cmH2O/l) was not significantly modified by PEEP from zero (23.49 +/- 1.21) to 5 cmH2O (21.89 +/- 0.70). However, a significant decrease (P<0.0003) at 10 cmH2O PEEP (18.86 +/- 1.13), as well as (P<0.0001) at 15 cmH2O (18.41 +/- 0.82) was observed after PEEP application. Volume dependence of viscoelastic properties showed a slight but not significant tendency to increase with PEEP. The significant decreases in cardiac index (l min-1 m-2) due to PEEP increments (3.90 +/- 0.22 at ZEEP, 3.43 +/- 0.17 (P<0. 0260) at 5 cmH2O of PEEP, 3.31 +/- 0.22 (P<0.0260) at 10 cmH2O of PEEP, and 3.10 +/- 0.22 (P<0.0113) at 15 cmH2O of PEEP) were compensated for by an increase in arterial oxygen content owing to shunt fraction reduction (%) from 22.26 +/- 2.28 at ZEEP to 11.66 +/- 1.24 at PEEP of 15 cmH2O (P<0.0007). We conclude that increments in PEEP resulted in a reduction of both airway resistance and respiratory elastance. These results could reflect improvement in respiratory mechanics. However, due to possible hemodynamic instability, PEEP should be carefully applied to postoperative cardiac patients.
J O Auler; M J Carmona; C V Barbas; P H Saldiva; L M Malbouisson
Publication Detail:
Type:  Clinical Trial; Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Brazilian journal of medical and biological research = Revista brasileira de pesquisas médicas e biológicas / Sociedade Brasileira de Biofísica ... [et al.]     Volume:  33     ISSN:  0100-879X     ISO Abbreviation:  Braz. J. Med. Biol. Res.     Publication Date:  2000 Jan 
Date Detail:
Created Date:  2000-06-05     Completed Date:  2000-06-05     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  8112917     Medline TA:  Braz J Med Biol Res     Country:  BRAZIL    
Other Details:
Languages:  eng     Pagination:  31-42     Citation Subset:  IM    
Unidade de Tratamento Intensivo Pós Operatório, InCorHC, Universidade de São Paulo, São Paulo, SP, Brasil.
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MeSH Terms
Airway Resistance / physiology
Analysis of Variance
Cardiac Surgical Procedures*
Hemodynamics / physiology*
Lung Compliance / physiology
Middle Aged
Oxygen Consumption
Positive-Pressure Respiration*
Postoperative Period
Prospective Studies
Respiratory Mechanics / physiology*

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

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