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🏥 | I won't lose to the low pressure!Three self-cares to make you feel comfortable both physically and mentally


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Don't lose to low pressure!Three self-cares to make you feel comfortable both physically and mentally

 
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By warming the part where these three necks are attached, blood flow improves.
 

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Blood flow

Blood flow(Ketsuryu,British: bloodflow) Isblood OfItineraryThat.Blood circulationAlso called (Kekko).

Overview

Blood flow is very complex and academicallyHemorheologyIt is being studied in fields such as (blood rheology).

bloodIt is composed of cellular components (erythrocytes, white blood cells, platelets) and plasma (aqueous solutions of various electrolytes and various organic substances) and has non-Newtonian viscosity.[1].

blood TheplasmaAnd variousblood cellIt is composed of ingredients.91.5% of plasmaWedAnd 7%protein, Other solute components are 1.5%.What makes up the blood cell componentplatelet,White blood cell,Red blood cellIs.The presence of these blood cell components and the molecules in plasmaInteractionByBlood is "idealNewtonian fluidBehave differently from[2]

It is pointed out that the diameter of red blood cells is larger than the diameter of small parts of capillaries, which is sometimes mentioned to help beginners understand the difficulty of understanding blood flow. is there.Red blood cellIs said to be 7-8 μm, etc.CapillariesThe inner diameter of the blood cells is 5 to 15 μmn, which means that red blood cells are found in the narrow areas of the capillaries.TransformationIt is sometimes pointed out that it is finally passing by doing so.

Of blood flowモデルThe conversion is not straightforward, and the range of conditions in which each model is effective, such as the Newtonian fluid model, Bingham fluid model, Einstein model, Casson model, and Quemada model, is carefully examined, and depending on the part and situation of the human body, Adoption of multiple models should be carefully considered. →HemorheologySee

[3]

The flow velocity (flowing speed) of blood flow varies greatly depending on the location of blood vessels.

Human capitalRelationship between blood flow velocity and total cross-sectional area of ​​blood vessels[4]
 Types of blood vessels  Total cross section  Flow velocity (cm / s) 
大動脈3–5 cm240 cm / s
Capillaries4500–6000 cm20.03 cm / s[5]
up and downVena cava14 cm215 cm / s

The blood flow is basicallyPulsating current(The flow rate is not a constant flow, but a pulsating flow, and the flow rate changes periodically).

Biomechanics of blood flow

The driving force for blood to flow through blood vessels is心 臓It is the pumping of blood by the pump function of.Since the blood vessel wall has a highly elastic and mobile structure, a force interaction acts between the blood and the blood vessel wall, affecting each other's mechanical behavior.Therefore, to consider the circulatory dynamics of bloodFluid mechanicsElastic mechanicsA basic understanding of is required.

Quantitative description

Normal blood flowLaminar flowTherefore, the flow velocity of blood flow is inversely proportional to the cross-sectional area of ​​the blood vessel, and therefore has a different flow velocity for each cross section.Therefore, the flow velocity is the fastest near the center of the blood vessel and the slowest near the wall of the blood vessel.Average velocity is usually used when referring to flow velocity[6].

Pulsation index (PI)

To measure the flow velocity of blood flowLaser Doppler velocimeterThere are various methods such as[7].arteryThe flow velocity in is faster.As one of the parameters to quantify the differencePulsation index(Pulsatility index, PI) Is used.This is equal to the difference between the maximum systolic flow velocity and the diastolic minimum flow velocity divided by the average flow velocity.This value decreases as you move further away from the heart[8].

Darcy's Law and Hagen-Poiseuille's Formula

Below is Darcy's Law[9](Darcy's law, Above formula) andHagen-Poiseuille ceremony[10][11](Bottom) is shown.

symbol:

F = blood flow Blood flow (m*s-1)
P = pressure (Pa)
R = resistance resistance (m-1)
ν = fluid viscosity Of fluidViscosity (Pa · s)
L = length of tube Tube length (m)
r = radius of tube tube radius (m)

As shown by the second equation, the resistance changes dramatically depending on the radius of the tube.Based on this principle, if the blood vessel contracts slightly due to cold weather, the blood flow will drop extremely, and if the radius of the blood vessel becomes slightly larger due to bathing, the blood flow will increase at once.Also, AngioplastyThen.Balloon catheterThis makes it possible to increase blood flow by slightly increasing the radius.

measurement

Can be measured with.There are several types such as ultrasonic blood flow meters and laser blood flow meters.

In addition, a method for visualizing blood flow as a vector using phase contrast MRI, Vector Flow Mapping applying ultrasonic measurement, and Echo PIV is also being researched.

Phase contrast MRI

A blood flow visualization measurement method using the phase contrast method, which is a method of MRI.Utilizing the fact that the phase difference of protons generated by the gradient magnetic field is proportional to the velocity of the fluid, the spatial distribution of blood flow velocity is visualized as a vector by synthesizing images taken with the gradient magnetic field in two or three directions. It is a method to do. The one taken three-dimensionally is called 2D Flow MRI, and it is the only method that can actually measure the three-dimensional blood flow vector.

Vector Flow Mapping (VFM)

It is a method of visualizing blood flow by superimposing color Doppler and speckle tracking on the assumption that the flow rate is preserved in the measurement surface.Keiichi ItayaDeveloped by Unlike Echo PIV, it does not use a contrast medium, so it can be measured easily and non-invasively.[12]
The principle is to visualize the blood flow as a two-dimensional vector by calculating the blood flow velocity in the direction orthogonal to the beam in addition to the blood flow velocity in the beam direction from the probe measured by the color Doppler.
In the ventricle, the blood flow velocity in the direction orthogonal to the beam is obtained by the following algorithm.[13]

  1. The inside of the measurement cross section of the ventricle lumen is divided into a quadrangular mesh.
  2. Under the assumption that there is no out-of-plane inflow and outflow on the ultrasonic measurement surface, the flow conservation law is calculated by the mesh adjacent to the heart wall.The inflow and outflow of the upper and lower sides are known from the color Doppler, the inflow and outflow of the adjacent side of the wall can be calculated from the speed of the speckle tracking wall, and the inflow and outflow of the remaining one side is calculated.
  3. The entire beam orthogonal velocity is calculated by repeating the calculation (2) inward from the heart wall in order.

Echo PIV

It is a method of injecting contrast-enhanced particles into a blood vessel and tracking the movement of individual particles.While it is possible to analyze with high accuracy in the low flow velocity region, it is difficult to maintain accuracy with high-speed blood flow due to the limitation of the frame rate in B mode, and it is difficult to measure blood flow exceeding 42 cm / s in the ventricle. ..

Blood circulation failure

Inhibition of blood flowIschemia,infarctionCan cause such things.

For example, it can occur due to the following.[Source required]

Source/Footnote

  1. ^ Motoaki Sugawara, Shinji Maeda, "Blood Leology and Blood Flow," Corona Publishing Co., Ltd., 2003. 
  2. ^ Gerard J. Tortora, Bryan Derrickson (2012). “The Cardiovascular System: The Blood”. Principles of Anatomy & Physiology, 13th. John Wiley & Sons, Inc .. pp. 729–732. ISBN 978-0470-56510-0 
  3. ^ [Who?]"Blood flow can theoretically be calculated using vascular resistance and pressure gradients.[Source required]""Mathematically speaking, blood flow is Darcy's law (so to speak, the blood flow version)Ohm's lawSomething like)Hagen-Poiseuille ceremonyCan be expressed by.[Source required]'
  4. ^ Gerard J. Tortora, Bryan Derrickson (2012). “The Cardiovascular System: Blood Vessels and Hemodynamics”. Principles of Anatomy & Physiology, 13th. John Wiley & Sons, Inc .. p. 816. ISBN 978-0470-56510-0 
  5. ^ Elaine N. Marieb, Katja Hoehn. (2013). “The Cardiovascular System: Blood Vessels”. Human anatomy & physiology, 9th ed.. Pearson Education, Inc .. p. 712. ISBN 978-0-321-74326-8 
  6. ^ Gerard J. Tortora, Bryan Derrickson (2012). “The Cardiovascular System: Blood Vessels and Hemodynamics”. Principles of Anatomy & Physiology, 13th. John Wiley & Sons, Inc .. p. 816. ISBN 978-0470-56510-0 
  7. ^ Stücker, M .; Bailer, V .; Reuther, T; Hoffman, K .; Kellam, K .; Altmeyer, P (1996). “Capillary Blood Cell Velocity in Human Skin Capillaries Located Perpendicularly to the Skin Surface: Measured by a New Laser Doppler Anemometer ”. Microvasc Research 52 (2): 188–192. two:10.1063/1.1754319. PMID 8901447. 
  8. ^ Gerard J. Tortora, Bryan Derrickson (2012). “The Cardiovascular System: Blood Vessels and Hemodynamics”. Principles of Anatomy & Physiology (13th ed.). John Wiley & Sons, Inc .. p. 817. ISBN 978-0470-56510-0 
  9. ^ H. Darcy, Les Fontaines Publiques de la Ville de Dijon, Dalmont, Paris (1856).
  10. ^ Kirby, BJ (2010). Micro- and Nanoscale Fluid Mechanics: Transport in Microfluidic Devices..Cambridge University Press. ISBN 978-0-521-11903-0. http://www.kirbyresearch.com/textbook 
  11. ^ Bruus, H. (2007). Theoretical Microfluidics 
  12. ^ Keiichi Itaya, Miyajikan "Ultrasound VFM", "Inspection and Technology", Vol. 41, No. 12, Igaku-Shoin, November 2013, 11, pp. 1-1126.
  13. ^ Katsutoshi Takenaka; Hiroyuki Tode; Tomoko Ishizu ed., Heart Echo Handbook Heart Failure, Kinhodo, 2016. 

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