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A perfusion pump, c. 1935, an early device for simulating natural perfusion
In physiology, perfusion is the process of a body delivering blood to a capillary bed in its biological tissue. The word is derived from the French verb "perfuser" meaning to "pour over or through."
Tests verifying that adequate perfusion exists are a part of a patient's assessment process that are performed by medical or emergency personnel. The most common methods include evaluating a body's skin color, temperature, condition and capillary refill.
Contents
- 1 Overperfusion and underperfusion
- 2 Discovery
- 3 Measurement
- 3.1 Nuclear medicine
- 3.2 MRI
- 3.3 CT
- 3.4 Thermal diffusion
- 4 See also
- 5 References
- 6 External links
Overperfusion and underperfusion
The terms "overperfusion" and "underperfusion" are measured relative to the average level of perfusion that exists across all the tissues in an individual body, and should not be confused with hypoperfusion and "hyperperfusion", which measure the perfusion level relative to a tissue's current need to meet its metabolic needs.
Heart tissues, for example, are usually classified as being overperfused because they normally are receiving more blood than the rest of tissues in the organism. In the case of skin cells, extra blood flow in them is used for thermoregulation of a body. In addition to delivering oxygen, blood flow helps to dissipate heat in a physical body by redirecting warm blood closer to its surface where it can help to cool a body through sweating and thermal dissipation.
Discovery
In 1920, August Krogh was awarded the Nobel Prize in Physiology or Medicine for his discovering the mechanism of regulation of capillaries in skeletal muscle. Krogh was the first to describe the adaptation of blood perfusion in muscle and other organs according to demands through the opening and closing of arterioles and capillaries.[citation needed]
Measurement
See also: Perfusion scanning
Nuclear medicine
Perfusion of various tissues can be readily measured in vivo with nuclear medicine methods which are mainly positron emission tomography (PET) and single photon emission computed tomography (SPECT).[citation needed] Various radiopharmaceuticals targeted at specific organs are also available, some of the most common are
- 99mTc labelled HMPAO and ECD for brain perfusion (rCBF) studied with SPECT
- 99mTc labelled Tetrofosmin and Sestamibi for myocardial perfusion imaging with SPECT
- 133Xe-gas for absolute quantification of brain perfusion (rCBF) with SPECT
- 15O-labeled water for brain perfusion (rCBF) with PET (absolute quantification is possible when measuring arterial radioactivity concentration)
- 82Rb-chloride for measuring myocardial perfusion with PET (absolute quantification is possible)
MRI
Two main categories of magnetic resonance imaging (MRI) techniques can be used to measure tissue perfusion in vivo.
- The first is based on the use of an injected contrast agent that changes the magnetic susceptibility of blood and thereby the MR signal which is repeatedly measured during bolus passage.[citation needed]
- The other category is based on arterial spin labelling (ASL), where arterial blood is magnetically tagged before it enters into the tissue being examined and the amount of labelling that is measured and compared to a control recording obtained without spin labelling.[citation needed]
CT
Brain perfusion (more correctly transit times) can be estimated with contrast-enhanced computed tomography.[citation needed]
Thermal diffusion
Perfusion can be determined by measuring the total thermal diffusion and then separating it into thermal conductivity and perfusion components.[1] rCBF is usually measured continuously in time. It is necessary to stop the measurement periodically to cool down and reassess the thermal conductivity.
See also
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Medicine portal |
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Underwater diving portal |
- Reperfusion injury
- Machine perfusion
- Perfusionist
- Myocardial perfusion imaging
- rCBF
- Cerebral edema
References
- ^ P. Vajkoczy, H. Roth, P. Horn, T. Lucke, C. Thome, U. Hubner, G. T. Martin, C. Zappletal, E. Klar, L. Schilling, and P. Schmiedek, “Continuous monitoring of regional cerebral blood flow: experimental and clinical validation of a novel thermal diffusion microprobe,” J. Neurosurg., vol. 93, no. 2, pp. 265–274, Aug. 2000. [http://www.ncbi.nlm.nih.gov/pubmed/10930012.
External links
- Perfusion Protocol (requires Adobe Acrobat Reader)
- University of Iowa Perfusion Technology Program
- SUNY Upstate Medical University Perfusion Program
- Cardiac Surgery Portal
- The New Orleans Conference: Practices in Cardiac Surgery and Extracorporeal Technologies
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Respiratory system, physiology: respiratory physiology
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| Lung volumes |
- VC
- FRC
- Vt
- dead space
- CC
- PEF
- calculations
- respiratory minute volume
- FEV1/FVC ratio
- methods of lung testing
- spirometry
- body plethysmography
- peak flow meter
- nitrogen washout
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| Airways/ventilation (V) |
- positive pressure ventilation
- breath (inhalation
- exhalation)
- respiratory rate
- respirometer
- pulmonary surfactant
- compliance
- elastic recoil
- hysteresivity
- airway resistance
- bronchial hyperresponsiveness
- bronchoconstriction/bronchodilation
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| Blood/perfusion (Q) |
- pulmonary circulation
- hypoxic pulmonary vasoconstriction
- pulmonary shunt
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Interactions/
ventilation/perfusion ratio (V/Q) |
- ventilation/perfusion scan
- zones of the lung
- gas exchange
- pulmonary gas pressures
- alveolar gas equation
- alveolar–arterial gradient
- hemoglobin
- oxygen–haemoglobin dissociation curve (Oxygen saturation
- 2,3-BPG
- Bohr effect
- Haldane effect)
- carbonic anhydrase (chloride shift)
- oxyhemoglobin
- respiratory quotient
- arterial blood gas
- diffusion capacity (DLCO)
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| Control of respiration |
- pons
- pneumotaxic center
- apneustic center
- medulla
- dorsal respiratory group
- ventral respiratory group
- chemoreceptors
- pulmonary stretch receptors
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| Insufficiency |
- high altitude
- oxygen toxicity
- hypoxia
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anat (n, x, l, c)/phys/devp
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noco (c, p)/cong/tumr, sysi/epon, injr
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proc, drug (R1/2/3/5/6/7)
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Cardiovascular system, physiology: cardiovascular physiology
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| Heart |
| Volumes |
- Stroke volume = End-diastolic volume – End-systolic volume
- Cardiac output = Heart rate × Stroke volume
- Frank–Starling law of the heart
- Cardiac function curve
- Venous return curve
- Aortic valve area calculation
- Ejection fraction
- Cardiac index
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| Dimensions |
- Fractional shortening = (End-diastolic dimension – End-systolic dimension) / End-diastolic dimension
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| Interaction diagrams |
- Cardiac cycle
- Wiggers diagram
- Pressure volume diagram
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| Tropism |
- Chronotropic (Heart rate)
- Dromotropic (Conduction velocity)
- Inotropic (Contractility)
- Bathmotropic (Excitability)
- Lusitropic (Relaxation)
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Conduction system /
Cardiac electrophysiology |
- Cardiac action potential
- Atrial action potential
- Ventricular action potential
- Effective refractory period
- Pacemaker potential
- EKG
- P wave
- PR interval
- QRS complex
- QT interval
- ST segment
- T wave
- U wave
- Hexaxial reference system
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| Chamber pressure |
Central venous pressure/right atrial pressure → Right ventricular pressure → Pulmonary artery pressure → Pulmonary wedge pressure/left atrial pressure → Left ventricular pressure → Aortic pressure
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| Other |
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Vascular system/
Hemodynamics |
| Blood flow |
- Compliance
- Vascular resistance
- Total peripheral resistance
- Pulse
- Perfusion
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| Blood pressure |
- Pulse pressure
- Mean arterial pressure
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| Regulation of BP |
- Baroreflex
- Kinin–kallikrein system
- Renin–angiotensin system
- Vasoconstrictors/Vasodilators
- Autoregulation
- Myogenic mechanism
- Tubuloglomerular feedback
- Cerebral autoregulation
- Paraganglia
- Aortic body
- Carotid body
- Glomus cell
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noco/cong/tumr, sysi/epon, injr
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proc, drug (C1A/1B/1C/1D), blte
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anat (a:h/u/t/a/l,v:h/u/t/a/l)/phys/devp/cell/prot
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noco/syva/cong/lyvd/tumr, sysi/epon, injr
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proc, drug (C2s+n/3/4/5/7/8/9)
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