Document Detail

Effects of low flow on pulmonary vascular flow-pressure curves and pulmonary vascular impedance.
MedLine Citation:
PMID:  10435009     Owner:  NLM     Status:  MEDLINE    
OBJECTIVE: Flow-pressure curves and vascular impedance are commonly used to investigate pulmonary circulation, but they may be affected at low flow by reflex neurohumoral activation. We therefore investigated the mechanical effects and the reflex effects of decreased flow on pulmonary vascular resistance and impedance. METHODS: In ten anaesthetized dogs, we compared flow-pressure curves generated in less than 10 s to prevent sympathetic activation (fast curves), or generated over 20-30 min to allow neurohumoral equilibration (slow curves), in hyperoxia (inspired oxygen, 40%) and in hypoxia (inspired oxygen, 10%), before and after adrenergic blockade by phentolamine and propranolol. Resistance was assessed from the flow-pressure relationship. Impedance was computed from instantaneous flow and pressure obtained with an ultrasonic flowmeter and a micromanometer-tipped catheter. RESULTS: At baseline, fast flow-pressure curves were steeper and had a lower pressure intercept. Transient low flow did not affect heart rate or pulmonary arterial elastance. Sustained low flow increased heart rate, resistance and elastance, suggesting baroreceptor-induced sympathetic stimulation. After adrenergic blockade, no difference persisted between effects of transient and sustained low flow. In hypoxia, slow and fast flow-pressure curves were similar. Hypoxia increased heart rate and resistance but did not decrease elastance, suggesting chemoreceptor-induced sympathetic stimulation. In hypoxia, differences between transient and sustained low flow were no longer significant, and were completely suppressed by adrenergic blockade. In two additional dogs, epinephrine infusion increased pulmonary vascular resistance and elastance. CONCLUSIONS: We conclude that (1) compared to transient low flow, sustained low flow is associated with increases in distal resistance and proximal elastance due to sympathetic stimulation and (2) these differences between the effects of transient and sustained low flow do not persist in hypoxia, because of an already present chemoreceptor-induced sympathetic stimulation.
S Brimioulle; M Maggiorini; J Stephanazzi; F Vermeulen; P Lejeune; R Naeije
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Cardiovascular research     Volume:  42     ISSN:  0008-6363     ISO Abbreviation:  Cardiovasc. Res.     Publication Date:  1999 Apr 
Date Detail:
Created Date:  1999-08-19     Completed Date:  1999-08-19     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0077427     Medline TA:  Cardiovasc Res     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  183-92     Citation Subset:  IM    
Laboratory of Cardiovascular and Respiratory Physiology, Free University of Brussels, Belgium.
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MeSH Terms
Adrenergic alpha-Antagonists / pharmacology*
Adrenergic beta-Antagonists / pharmacology*
Anoxia / metabolism*,  physiopathology
Blood Pressure / drug effects
Dose-Response Relationship, Drug
Epinephrine / pharmacology
Phentolamine / pharmacology*
Propranolol / pharmacology*
Pulmonary Circulation / drug effects*
Regional Blood Flow / drug effects
Sympathomimetics / pharmacology
Vascular Resistance / drug effects
Reg. No./Substance:
0/Adrenergic alpha-Antagonists; 0/Adrenergic beta-Antagonists; 0/Sympathomimetics; 50-60-2/Phentolamine; 51-43-4/Epinephrine; 525-66-6/Propranolol

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

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