perfusion

Information about 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]



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

 •  • [ e]
Respiratory system, physiology: respiratory physiology
Volumeslung volumes - vital capacity - functional residual capacity - respiratory minute volume - dead space - spirometry - body plethysmography - peak flow meter
Airwaysventilation (V) (positive pressure) - breath (inhalation, exhalation) -respiratory rate - respirometer - pulmonary surfactant - compliance - hysteresivity - airway resistance
Bloodpulmonary circulation - perfusion (Q) - hypoxic pulmonary vasoconstriction - pulmonary shunt
Interactionsventilation/perfusion ratio (V/Q) and scan - zones of the lung - gas exchange - pulmonary gas pressures - alveolar gas equation - hemoglobin - oxygen-haemoglobin dissociation curve (2,3-DPG, Bohr effect, Haldane effect) - carbonic anhydrase (chloride shift) - oxyhemoglobin - respiratory quotient - arterial blood gas - diffusion capacity - Dlco
Control of respirationpons (pneumotaxic center, apneustic center) - medulla (dorsal respiratory group, ventral respiratory group) - chemoreceptors (central, peripheral) - pulmonary stretch receptors - Hering-Breuer reflex
Insufficiencyhigh altitude - oxygen toxicity - hypoxia
Physiology (from Greek: φυσις, physis, “nature, origin”; and λόγος, logos, "knowledge") is the study of the mechanical, physical, and biochemical functions of living organisms.
..... Click the link for more information.
Arteries are muscular blood vessels that carry blood away from the heart.[1] All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood.

The circulatory system is extremely important for sustaining life.
..... Click the link for more information.
Blood is a specialized biological fluid consisting of red blood cells (also called RBCs or erythrocytes), white blood cells (also called leukocytes) and platelets (also called thrombocytes) suspended in a complex fluid medium known as blood plasma.
..... Click the link for more information.
capillary is used to describe any very narrow tube or channel through which a fluid can pass. See capillary action for details.


Capillaries are the smallest of a body's blood vessels, measuring 5-10 μm, which connect arterioles and venules, and are
..... Click the link for more information.
Biological tissue is a collection of interconnected cells that perform a similar function within an organism.

The study of tissue is known as histology, or, in connection with disease, histopathology.
..... Click the link for more information.
This article or section needs copy editing for grammar, style, cohesion, tone and/or spelling.
You can assist by [ editing it] now. A how-to guide is available, as is general .
This article has been tagged since August 2007.
..... Click the link for more information.
Medicine is the science and "" of maintaining and/or restoring human health through the study, diagnosis, and treatment of patients. The term is derived from the Latin ars medicina meaning the art of healing.
..... Click the link for more information.
The mean arterial pressure (MAP) is a term used in medicine to describe a notional average blood pressure in an individual. It is defined as the average arterial pressure during a single cardiac cycle.
..... Click the link for more information.
Vascular resistance is a term used to define the resistance to flow that must be overcome to push blood through the circulatory system. The resistance offered by the peripheral circulation is known as the systemic vascular resistance (SVR
..... Click the link for more information.
Shock
Classification & external resources

ICD-10 many incl. R 57.
ICD-9 785

DiseasesDB 12013
MedlinePlus 000039
eMedicine emerg/531   med/285 emerg/533

MeSH D012769

For other uses, see Shock.

..... Click the link for more information.
Skin layers: epidermis, dermis, and subcutis, showing a hair follicle, sweat gland & sebaceous gland.]] In zootomy and dermatology, skin is the largest organ of the integumentary system made up of multiple layers of epithelial tissues that guard underlying muscles and organs.
..... Click the link for more information.
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when temperature surrounding is very different. This process is one aspect of homeostasis: a dynamic state of stability between an animal's internal environment and its
..... Click the link for more information.
2, −1
(neutral oxide)
Electronegativity 3.44 (Pauling scale)
Ionization energies
(more) 1st: 1313.9 kJmol−1
2nd: 3388.3 kJmol−1
3rd: 5300.5 kJmol−1

Atomic radius 60 pm
Atomic radius (calc.
..... Click the link for more information.
In physics, dissipation embodies the concept of a dynamical system where important mechanical modes, such as waves or oscillations, lose energy over time, typically due to the action of friction or turbulence.
..... Click the link for more information.
Perspiration (also called sweating or sometimes transpiration) is the production and evaporation of a fluid, consisting primarily of water as well as a smaller amount of sodium chloride (the main constituent of "table salt"), that is excreted by the sweat glands in the skin of
..... Click the link for more information.
Thermal radiation is electromagnetic radiation emitted from the surface of an object which is due to the object's temperature. Infrared radiation from a common household radiator or electric heater is an example of thermal radiation, as is the light emitted by a glowing
..... Click the link for more information.
Functional magnetic resonance imaging (fMRI) is the use of MRI to measure the haemodynamic response related to neural activity in the brain or spinal cord of humans or other animals. It is one of the most recently developed forms of neuroimaging.
..... Click the link for more information.
In vivo (Latin: (with)in the living) means that which takes place inside an organism. In science, in vivo refers to experimentation done in or on the living tissue of a whole, living organism as opposed to a partial or dead one.
..... Click the link for more information.
See also:
Radiocontrast agents (also simply contrast agents or contrast materials) are compounds used to improve the visibility of internal bodily structures in an X-ray image.
..... Click the link for more information.
In physics and applied disciplines such as electrical engineering, the magnetic susceptibility is the degree of magnetization of a material in response to an applied magnetic field.
..... Click the link for more information.
In medicine, a bolus (from Latin bolus , ball) is the administration of a medication, drug or other compound that is given to raise blood concentration to an effective level. The administration can be given intravenously, by intramuscular or subcutaneous injection.
..... Click the link for more information.
magnet is a material or object that produces a magnetic field. A "hard" or "permanent" magnet is one which stays magnetized for a long time, such as magnets often used in refrigerator doors.
..... Click the link for more information.
Reperfusion injury refers to damage to tissue caused when blood supply returns to the tissue after a period of ischemia. The absence of oxygen and nutrients from blood creates a condition in which the restoration of circulation results in inflammation and oxidative damage through
..... Click the link for more information.
Medical College of Georgia is the smallest of four research schools in the University System of Georgia (USG). MCG currently has 5 undergraduate and graduate schools on campus: The School of Medicine, School of Dentistry, School of Nursing, School of Allied Health, and Graduate
..... Click the link for more information.
respiratory system generally includes tubes, such as the bronchi, used to carry air to the lungs, where gas exchange takes place. A diaphragm pulls air in and pushes it out. Respiratory systems of various types are found in a wide variety of organisms.
..... Click the link for more information.
Human physiology is the science of the mechanical, physical, and biochemical functions of humans in good health, their organs, and the cells of which they are composed. The principal level of focus of physiology is at the level of organs and systems.
..... Click the link for more information.
Respiratory physiology is the branch of human physiology focusing upon respiration.

Topics include:

Volumes

  • lung volumes
  • vital capacity
  • functional residual capacity
  • dead space
  • spirometry
  • body plethysmography
  • peak flow meter


..... Click the link for more information.
Larger volumes Smaller volumes
males females
taller people shorter people
non-smokers heavy smokers
professional athletes[1] non-athletes
people living at high altitudes people living at low altitudes
..... Click the link for more information.
Vital capacity is the maximum volume of air that a person can exhale after maximum inhalation. It can also be the maximum volume of air that a person can inhale after maximum exhalation.
..... Click the link for more information.
Functional Residual Capacity (FRC) is the volume of air present in the lungs at the end of passive expiration. At FRC, the elastic recoil forces of the lungs and chest wall are equal but opposite and there is no exertion by the diaphragm or other respiratory muscles.
..... Click the link for more information.

This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.