WordNet

or of relating to or involved in hemodynamics
the branch of physiology that studies the circulation of the blood and the forces involved

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/11/07 10:13:52」(JST)

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Hemodynamics, meaning literally "blood movement" is the study of blood flow or the circulation. It explains the physical laws that govern the flow of blood in the blood vessels.

Physiology[edit]

All animal cells require oxygen (O₂) for the conversion of carbohydrates, fats and proteins into carbon dioxide (CO₂), water and energy in a process known as aerobic respiration. The circulatory system functions to transport the blood to deliver O₂, nutrients and chemicals to the cells of the body to ensure their health and proper function, and to remove the cellular waste products.

The circulatory system is a connected series of tubes, which includes the heart, the arteries, the microcirculation, and the veins.

The heart is the driver of the circulatory system generating cardiac output (CO) by rhythmically contracting and relaxing. This creates changes in regional pressures, and, combined with a complex valvular system in the heart and the veins, ensures that the blood moves around the circulatory system in one direction. The “beating” of the heart generates pulsatile blood flow which is conducted into the arteries, across the micro-circulation and eventually, back via the venous system to the heart. The aorta, the main artery, leaves the left heart and proceeds to divide into smaller and smaller arteries until they become arterioles, and eventually capillaries, where oxygen transfer occurs. The capillaries connect to venules, into which the deoxygenated blood passes from the cells back into the blood, and the blood then travels back through the network of veins to the right heart. The micro-circulation—the arterioles, capillaries, and venules—constitutes most of the area of the vascular system and is the site of the transfer of O₂, glucose, and enzyme substrates into the cells. The venous system returns the de-oxygenated blood to the right heart where it is pumped into the lungs to become oxygenated and CO₂ and other gaseous wastes exchanged and expelled during breathing. Blood then returns to the left side of the heart where it begins the process again. Clearly the heart, vessels and lungs are all actively involved in maintaining healthy cells and organs, and all influence hemodynamics. Hemodynamic disorders- These are the disturbances in the blood movement in our body.

The factors influencing hemodynamics are complex and extensive but include CO, circulating fluid volume, respiration, vascular diameter and resistance, and blood viscosity. Each of these may in turn be influenced by physiological factors, such as diet, exercise, disease, drugs or alcohol, obesity and excess weight.

Our understanding of hemodynamics depends on measuring the blood flow at different points in the circulation. A basic approach to understanding hemodynamics is by “feeling the pulse”. This gives simple information regarding the strength of the circulation via the systolic stroke and the heart rate, both important components of the circulation which may be altered in disease. The blood pressure can be simply measured using a plethysmograph or cuff connected to a pressure sensor (mercury or aneroid manometer). This is the most common clinical measure of circulation and provides a peak systolic pressure and a diastolic pressure, often quoted as a normal 115/75. Sometimes the mean arterial pressure is calculated.

MAP ≈ ((BP_dia × 2) + BP_sys)/3 mm_Hg (or torr)

BP_dia is counted twice since the heart spends two thirds of the heart beat cycle in the diastolic.

where:

MAP = Mean Arterial Pressure
BP_dia = Diastolic blood pressure
BP_sys = Systolic blood pressure.

The arterial pulse pressure can be measured by placing a tonometer or pressure sensor on the skin surface above an artery. This provides a continuous pressure trace or arterial pulse pressure waveform which reflects cardiovascular performance (Fig1). A non-invasive Doppler can also be used to measure blood flow at any point in the circulation, including within the heart, the CO, and can be converted to a pressure difference using the modified Bernoulli equation, ΔP=4V2. An invasive manometer (pressure sensor) can be inserted into an artery on the end of a catheter to measure intra-arterial pulse pressures providing information on cardiovascular performance. Importantly all of these measures should be accompanied by a measure of CO so that the function of the heart and vessels can be distinguished. This allows for more effective understanding and treatment of the cardiovascular system.

The heart and the vascular beds are a dynamic and connected part of the circulatory system and combine to effect efficient transportation of the blood. Circulation is influenced by the resistance of the vascular bed against which the heart is pumping. For the right heart this is the pulmonary vascular bed, creating Pulmonary Vascular Resistance (PVR), while for the systemic circulation this is the systemic vascular bed, creating Systemic Vascular Resistance (SVR). The vessels actively change diameter under the influence of physiology or therapy, vasoconstrictors decrease vessel diameter and increase resistance, while vasodilators increase vessel diameter and decrease resistance. Put simply increasing resistance (narrowing the vessel) decreases CO, and conversely decreased resistance (widening the vessel) increases CO.

This can be explained mathematically:

By simplifying Darcy's Law, we get the equation that:

Flow = Pressure/Resistance

When applied to the circulatory system, we get:

CO = 80 x (MAP – RAP)/TPR

RAP = Mean Right Atrial Pressure in mmHg and

TPR = Total Peripheral Resistance in dynes-sec-cm-5.

However, as MAP >> RAP, and RAP is approximately 0, this can be simplified to:

CO ~= 80 x MAP/TPR

For right heart CO ~= MAP/PVR

For left heart CO ~= MAP/SVR

Physiologists will often re-arrange this equation, making MAP the subject, to study the body's responses.

80 x MAP ~= CO x TPR

Hemodynamics both as a clinical medical and as a discipline in physiology and bioengineering has many layers of complexity, beginning in the modern sense in the 1950s. For further information see the references at the end of the article on the Windkessel effect, and also the 1954 reference to the dynamics of pulsatile blood flow below.

Since the blood flow and blood pressure controls are performed by the cardiovascular system on the basic clock of the system (i.e., the heartbeat) and not on a per-minute basis, the new concepts of "per-beat hemodynamics" have been introduced and propagated by the International Hemodynamic Society.^[1]

Monitoring[edit]

An anesthetic machine with integrated systems for monitoring of several hemodynamic parameters, including blood pressure and heart rate.

Hemodynamic monitoring is the observation of hemodynamic parameters over time, such as blood pressure and heart rate. Blood pressure can be monitored either invasively through an inserted blood pressure transducer assembly (providing continuous monitoring), or noninvasively by repeatedly measuring the blood pressure with an inflatable blood pressure cuff.

Notes and references[edit]

^ Concept summary of per-beat hemodynamics
Detailed explanation of per-beat hemodynamics

Bibliography[edit]

Berne RM, Levy MN. Cardiovascular physiology. 7th Ed Mosby 1997
Rowell LB. Human Cardiovascular Control. Oxford University press 1993
Braunwald E (Editor). Heart Disease: A Textbook of Cardiovascular Medicine. 5th Ed. W.B.Saunders 1997
Siderman S, Beyar R, Kleber AG. Cardiac Electrophysiology, Circulation and Transport. Kluwer Academic Publishers 1991
American Heart Association
Otto CM, Stoddard M, Waggoner A, Zoghbi WA. Recommendations for Quantification of Doppler Echocardiography: A Report from the Doppler Quantification Task Force of the Nomenclature and Standards Committee of the American Society of Echocardiography. J Am Soc Echocardiogr 2002;15:167-184
Peterson LH, The Dynamics of Pulsatile Blood Flow, Circ. Res. 1954;2;127-139
Hemodynamic Monitoring, Bigatello LM, George E., Minerva Anestesiol, 2002 Apr;68(4):219-25

External links[edit]

Hemodynamic Society
Learn hemodynamics
Educational Particle Image Velocimetry (e-PIV) - resources and demonstrations

UpToDate Contents

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1. 心臓カテーテル検査法：正常な血行動態 cardiac catheterization techniques normal hemodynamics
2. 昇圧剤および強心剤の使用 use of vasopressors and inotropes
3. 心臓カテーテル検査で測定した弁膜疾患の血行動態 hemodynamics of valvular disorders as measured by cardiac catheterization
4. 肺動脈カテーテル法：トレーシングの解釈 pulmonary artery catheterization interpretation of tracings
5. 経食道心エコーによる血行動態評価 hemodynamics derived from transesophageal echocardiography

English Journal

Influence of wearing an unstable shoe on thigh and leg muscle activity and venous response in upright standing.

Sousa A, Tavares JM, Macedo R, Rodrigues AM, Santos R.SourceEscola Superior da Tecnologia de Saúde do Porto, Área Científica de Fisioterapia, Centro de Estudos de Movimento e Actividade Humana, Rua Valente Perfeito, 322, 4400-330 Vila Nova de Gaia, Portugal.
Applied ergonomics.Appl Ergon.2012 Sep;43(5):933-9. Epub 2012 Jan 25.
PURPOSE: To quantify the effect of unstable shoe wearing on muscle activity and haemodynamic response during standing.METHODS: Thirty volunteers were divided into 2 groups: the experimental group wore an unstable shoe for 8 weeks, while the control group used a conventional shoe for the same period.
PMID 22277098

Quantitative estimates of stimulation-induced perfusion response using two-photon fluorescence microscopy of cortical microvascular networks.

Chinta LV, Lindvere L, Dorr A, Sahota B, Sled JG, Stefanovic B.SourceImaging Research, Sunnybrook Research Institute, 2075 Bayview Avenue, Toronto, ON, Canada M4N 3M5; Department of Medical Biophysics, University of Toronto, 610 University Avenue, Toronto, ON, Canada M5G 2M9.
NeuroImage.Neuroimage.2012 Jul 2;61(3):517-24. Epub 2012 Apr 12.
Functional hyperemia, or the increase in focal perfusion elicited by neuronal activation, is one of the primary functions of the neurovascular unit and a hallmark of healthy brain functioning. While much is known about the hemodynamics on the millimeter to tenths of millimeter-scale accessible by MR
PMID 22521258

Japanese Journal

Vanishing of ruptured adrenal mass with takotsubo cardiomyopathy

Endocrine Journal, 2018
NAID 130007472756

Performance of computed tomography-derived pulmonary vasculature metrics in the diagnosis and haemodynamic assessment of pulmonary arterial hypertension