Document Detail

Paradoxical responses to positive end-expiratory pressure in patients with airway obstruction during controlled ventilation.
MedLine Citation:
PMID:  16003057     Owner:  NLM     Status:  MEDLINE    
OBJECTIVE: To reevaluate the clinical impact of external positive end-expiratory pressure (external-PEEP) application in patients with severe airway obstruction during controlled mechanical ventilation. The controversial occurrence of a paradoxic lung deflation promoted by PEEP was scrutinized.
DESIGN: External-PEEP was applied stepwise (2 cm H(2)O, 5-min steps) from zero-PEEP to 150% of intrinsic-PEEP in patients already submitted to ventilatory settings minimizing overinflation. Two commonly used frequencies during permissive hypercapnia (6 and 9/min), combined with two different tidal volumes (VT: 6 and 9 mL/kg), were tested.
SETTING: A hospital intensive care unit.
PATIENTS: Eight patients were enrolled after confirmation of an obstructive lung disease (inspiratory resistance, >20 cm H(2)O/L per sec) and the presence of intrinsic-PEEP (> or =5 cm H(2)O) despite the use of very low minute ventilation.
INTERVENTIONS: All patients were continuously monitored for intra-arterial blood gas values, cardiac output, lung mechanics, and lung volume with plethysmography.
MEASUREMENTS AND MAIN RESULTS: Three different responses to external-PEEP were observed, which were independent of ventilatory settings. In the biphasic response, isovolume-expiratory flows and lung volumes remained constant during progressive PEEP steps until a threshold, beyond which overinflation ensued. In the classic overinflation response, any increment of external-PEEP caused a decrease in isovolume-expiratory flows, with evident overinflation. In the paradoxic response, a drop in functional residual capacity during external-PEEP application (when compared to zero-external-PEEP) was commonly accompanied by decreased plateau pressures and total-PEEP, with increased isovolume-expiratory flows. The paradoxic response was observed in five of the eight patients (three with asthma and two with chronic obstructive pulmonary disease) during at least one ventilator pattern.
CONCLUSIONS: External-PEEP application may relieve overinflation in selected patients with airway obstruction during controlled mechanical ventilation. No a priori information about disease, mechanics, or ventilatory settings was predictive of the response. An empirical PEEP trial investigating plateau pressure response in these patients appears to be a reasonable strategy with minimal side effects.
Maria Paula Caramez; Joao B Borges; Mauro R Tucci; Valdelis N Okamoto; Carlos R R Carvalho; Robert M Kacmarek; Atul Malhotra; Irineu Tadeu Velasco; Marcelo B P Amato
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Critical care medicine     Volume:  33     ISSN:  0090-3493     ISO Abbreviation:  Crit. Care Med.     Publication Date:  2005 Jul 
Date Detail:
Created Date:  2005-07-08     Completed Date:  2005-08-11     Revised Date:  2014-09-18    
Medline Journal Info:
Nlm Unique ID:  0355501     Medline TA:  Crit Care Med     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1519-28     Citation Subset:  AIM; IM    
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MeSH Terms
Aged, 80 and over
Airway Obstruction / complications*,  physiopathology,  therapy*
Asthma / complications,  physiopathology,  therapy
Lung Volume Measurements
Middle Aged
Monitoring, Physiologic
Positive-Pressure Respiration / adverse effects*
Pulmonary Disease, Chronic Obstructive / complications,  physiopathology,  therapy
Ventilators, Mechanical
Grant Support
K23 AG024837/AG/NIA NIH HHS; K23 AG024837-02/AG/NIA NIH HHS; R01 HL073146/HL/NHLBI NIH HHS; R01 HL073146-02/HL/NHLBI NIH HHS
Comment In:
Crit Care Med. 2005 Dec;33(12):2860   [PMID:  16352983 ]
Crit Care Med. 2005 Jul;33(7):1652-3   [PMID:  16003082 ]

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