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perfusion

  (pər-fyū'zhən) pronunciation
n.
  1. The act of perfusing.
  2. The injection of fluid into a blood vessel in order to reach an organ or tissues, usually to supply nutrients and oxygen.

 
 
Dental Dictionary: perfusion

n

A therapeutic measure whereby a drug intended for an isolated part of the body is introduced via the bloodstream.

 

The flow of fluid, usually blood through the vessels of an organ.

 

1. the act of pouring through or over; especially the passage of a fluid through the vessels of a specific organ.
2. a liquid poured through or over an organ or tissue.

  • p. pressure — the gradient between arterial blood pressure and venous pressure in a comparable location in the vascular tree.
  • pulmonary p. — blood flow through the pulmonary capillaries.
  • renal p. — the rate of perfusion in the kidney is much higher than in any other organ. The rate of formation of urine depends to a large extent on the perfusion rate.
  • p. scan — using pulmonary scintigraphy, radionucleotide agents injected into a peripheral vein can be detected where it is trapped in the pulmonary capillary bed. Used to assess pulmonary blood flow.
  • p. technique — maintenance of blood circulation to tissues during cardiopulmonary bypass.
  • p.:ventilation ratio — see ventilation: perfusion ratio.
 
Wikipedia: perfusion

In physiology, perfusion is the process of nutritive delivery of arterial blood to a capillary bed in the biological tissue.

Tests of adequate perfusion are a part of patient triage performed by medical or emergency personnel in a mass casualty incident.

Calculation

Perfusion ("F") can be measured with the following formula, where Pa is mean arterial pressure, Pv is mean venous pressure, and R is vascular resistance: [1]

F =  \frac{ P_A - P_V }{ R}

The term "Pa - Pv" is sometimes presented as "ΔP", for the change in pressure.[2]

The terms "perfusion" and "perfusion pressure" are sometimes used interchangably, but the equation should make clear that resistance can have an effect on the perfusion, but not on the perfusion pressure.

Overperfusion and underperfusion

The terms "overperfusion" and "underperfusion" are measured relative to the average level of perfusion across all tissues in an individual body, and the terms should not be confused with hypoperfusion and "hyperperfusion", which measure the perfusion level to the tissue's current need.

Tissues like the skin are considered overperfused and receive more blood than would be expected to meet the metabolic needs of the tissue. In the case of the skin, extra blood flow is used for thermoregulation. In addition to delivering oxygen, the blood helps dissipate heat by redirecting warm blood close to the surface where it can cool the body through the sweating and thermal radiation.

Measurement using fMRI

Two main categories of functional magnetic resonance imaging (fMRI) techniques can be used to measure tissue perfusion in vivo.

  • The first is based on the use of injected contrast agent that changes the magnetic susceptibility of blood and thereby the MR signal which is repeatedly measured during bolus passage.
  • The other category is based on arterial spin labeling (ASL), where arterial blood is magnetically tagged before it enters into the tissue of interest and the amount of labeling is measured and compared to a control recording obtained without spin labeling.

See also

References

  1. ^ Richard E. Klabunde. Cardiovascular Physiology Concepts. Retrieved on 9/12/06.
  2. ^ Physiology at MCG 7/7ch04/7ch04p26 - "Renal Perfusion Pressure and Vascular Resistance"

External links



 
 

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Copyrights:

Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved.  Read more
Dental Dictionary. Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved.  Read more
Sports Science and Medicine. The Oxford Dictionary of Sports Science & Medicine. Copyright © Michael Kent 1998, 2006, 2007. All rights reserved.  Read more
Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.  Read more
Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Perfusion" Read more

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