Document Detail

Marked differences between prone and supine sheep in effect of PEEP on perfusion distribution in zone II lung.
MedLine Citation:
PMID:  15774701     Owner:  NLM     Status:  MEDLINE    
The classic four-zone model of lung blood flow distribution has been questioned. We asked whether the effect of positive end-expiratory pressure (PEEP) is different between the prone and supine position for lung tissue in the same zonal condition. Anesthetized and mechanically ventilated prone (n = 6) and supine (n = 5) sheep were studied at 0, 10, and 20 cm H2O PEEP. Perfusion was measured with intravenous infusion of radiolabeled 15-microm microspheres. The right lung was dried at total lung capacity and diced into pieces (approximately 1.5 cm3), keeping track of the spatial location of each piece. Radioactivity per unit weight was determined and normalized to the mean value for each condition and animal. In the supine posture, perfusion to nondependent lung regions decreased with little relative perfusion in nondependent horizontal lung planes at 10 and 20 cm H2O PEEP. In the prone position, the effect of PEEP was markedly different with substantial perfusion remaining in nondependent lung regions and even increasing in these regions with 20 cm H2O PEEP. Vertical blood flow gradients in zone II lung were large in supine, but surprisingly absent in prone, animals. Isogravitational perfusion heterogeneity was smaller in prone than in supine animals at all PEEP levels. Redistribution of pulmonary perfusion by PEEP ventilation in supine was largely as predicted by the zonal model in marked contrast to the findings in prone. The differences between postures in blood flow distribution within zone II strongly indicate that factors in addition to pulmonary arterial, venous, and alveolar pressure play important roles in determining perfusion distribution in the in situ lung. We suggest that regional variation in lung volume through the effect on vascular resistance is one such factor and that chest wall conformation and thoracic contents determine regional lung volume.
Sten M Walther; Mats J Johansson; Torun Flatebø; Anne Nicolaysen; Gunnar Nicolaysen
Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't     Date:  2005-03-17
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  99     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2005 Sep 
Date Detail:
Created Date:  2005-08-16     Completed Date:  2005-10-27     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:  909-14     Citation Subset:  IM    
Intensive Care Unit, Div. of Surgery, Ullevål University Hospital, N-0407 Oslo, Norway.
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MeSH Terms
Blood Flow Velocity / physiology
Lung / blood supply*,  physiology*
Models, Biological*
Positive-Pressure Respiration / methods*
Prone Position / physiology*
Pulmonary Circulation / physiology*
Pulmonary Gas Exchange / physiology*
Supine Position / physiology*

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