Document Detail


Positive end-expiratory pressure affects regional redistribution of ventilation differently in prone and supine sheep.
MedLine Citation:
PMID:  15483412     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
OBJECTIVE: To examine interactions between positive end-expiratory pressure (PEEP) and posture on regional distribution of ventilation and to compare measurements of regional ventilation with two aerosols: a wet fluorescent microsphere aerosol (FMS, median mass aerodynamic diameter 1.1 microm) and a dry Tc-labeled carbon particle aerosol (Technegas, TG, median mass aerodynamic diameter approximately 0.1 microm). DESIGN: Experimental study. SETTING: Academic laboratory. SUBJECTS:: Anesthetized and mechanically ventilated sheep (n = 16). INTERVENTIONS: Four conditions were studied: prone or supine posture with or without 10 cm H2O PEEP. MEASUREMENTS AND MAIN RESULTS: Comparisons of FMS and TG were made in five animals. The median correlation coefficient of the two ventilation tracers was .95 (range, .91-.96). The mean ventilation per unit weight of dry lung for horizontal planes was almost identical whether measured with TG or FMS. The distribution of ventilation was assessed by analyzing deposition of aerosol in about 1,000 lung regions per animal. Distribution of ventilation down the vertical axis was linear in prone (the slope indicated a dorsal-to-ventral three-fold difference in ventilation) but unimodal in supine animals with the mode in the center of the lung. Redistribution of ventilation with 10 PEEP differed between posture, shifting the mode in supine toward dependent lung regions while eliminating the dorsal-to-ventral gradient in prone. The regional heterogeneity in ventilation was greater in supine sheep at both levels of PEEP, and this was due mostly to greater isogravitational heterogeneity in supine than in prone position. CONCLUSIONS: The wet fluorescent microsphere aerosol was as reliable as Technegas for high-resolution measurements of regional ventilation. The markedly different effects of 10 PEEP in supine and prone sheep may have important implications for gas exchange both in noninjured and injured lungs.
Authors:
Mats J Johansson; Andreas Wiklund; Torun Flatebø; Anne Nicolaysen; Gunnar Nicolaysen; Sten M Walther
Publication Detail:
Type:  Comparative Study; Journal Article    
Journal Detail:
Title:  Critical care medicine     Volume:  32     ISSN:  0090-3493     ISO Abbreviation:  Crit. Care Med.     Publication Date:  2004 Oct 
Date Detail:
Created Date:  2004-10-14     Completed Date:  2004-11-19     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0355501     Medline TA:  Crit Care Med     Country:  United States    
Other Details:
Languages:  eng     Pagination:  2039-44     Citation Subset:  AIM; IM    
Affiliation:
Division of Anesthesiology, Department of Medicine and Care, Faculty of Health Sciences at the University of Linköping, Linköping, Sweden.
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MeSH Terms
Descriptor/Qualifier:
Administration, Inhalation
Aerosols / administration & dosage,  diagnostic use*
Animals
Fluorescence
Microspheres
Models, Animal
Positive-Pressure Respiration*
Posture / physiology*
Prone Position / physiology
Pulmonary Gas Exchange / physiology*
Pulmonary Ventilation / physiology*
Respiration, Artificial
Sheep
Sodium Pertechnetate Tc 99m / administration & dosage,  diagnostic use
Supine Position / physiology
Chemical
Reg. No./Substance:
0/Aerosols; 112263-77-1/Technegas; 23288-60-0/Sodium Pertechnetate Tc 99m
Comments/Corrections
Comment In:
Crit Care Med. 2004 Oct;32(10):2156-7   [PMID:  15483433 ]

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


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