Document Detail

Maintenance of end-expiratory recruitment with increased respiratory rate after saline-lavage lung injury.
MedLine Citation:
PMID:  16959915     Owner:  NLM     Status:  MEDLINE    
Cyclical recruitment of atelectasis with each breath is thought to contribute to ventilator-associated lung injury. Extrinsic positive end-expiratory pressure (PEEPe) can maintain alveolar recruitment at end exhalation, but PEEPe depresses cardiac output and increases overdistension. Short exhalation times can also maintain end-expiratory recruitment, but if the mechanism of this recruitment is generation of intrinsic PEEP (PEEPi), there would be little advantage compared with PEEPe. In seven New Zealand White rabbits, we compared recruitment from increased respiratory rate (RR) to recruitment from increased PEEPe after saline lavage. Rabbits were ventilated in pressure control mode with a fraction of inspired O(2) (Fi(O(2))) of 1.0, inspiratory-to-expiratory ratio of 2:1, and plateau pressure of 28 cmH(2)O, and either 1) high RR (24) and low PEEPe (3.5) or 2) low RR (7) and high PEEPe (14). We assessed cyclical lung recruitment with a fast arterial Po(2) probe, and we assessed average recruitment with blood gas data. We measured PEEPi, cardiac output, and mixed venous saturation at each ventilator setting. Recruitment achieved by increased RR and short exhalation time was nearly equivalent to recruitment achieved by increased PEEPe. The short exhalation time at increased RR, however, did not generate PEEPi. Cardiac output was increased on average 13% in the high RR group compared with the high PEEPe group (P < 0.001), and mixed venous saturation was consistently greater in the high RR group (P < 0.001). Prevention of end-expiratory derecruitment without increased end-expiratory pressure suggests that another mechanism, distinct from intrinsic PEEP, plays a role in the dynamic behavior of atelectasis.
Rebecca S Syring; Cynthia M Otto; Rebecca E Spivack; Klaus Markstaller; James E Baumgardner
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2006-09-07
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  102     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2007 Jan 
Date Detail:
Created Date:  2007-01-08     Completed Date:  2007-03-13     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  331-9     Citation Subset:  IM    
Department of Clinical Studies, Section of Critical Care, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
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MeSH Terms
Blood Gas Analysis
Bronchoalveolar Lavage / adverse effects*
Cardiac Output / physiology
Disease Models, Animal
Exhalation / physiology*
Lung / physiopathology
Lung Injury
Maximal Expiratory Flow Rate / physiology
Positive-Pressure Respiration / methods*
Pulmonary Atelectasis / etiology*,  physiopathology*
Respiratory Mechanics / physiology
Sodium Chloride
Grant Support
Reg. No./Substance:
7647-14-5/Sodium Chloride
Comment In:
J Appl Physiol (1985). 2007 Jun;102(6):2414; author reply 2415   [PMID:  17551113 ]

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