Unit 10 HEMODYNAMICS Flashcards
What is hemodynamics?
Answer: Hemodynamics is the study of blood flow in the cardiovascular system.
Due to energy gradient in our body blood flows through the cardiovascular system. Blood moves in the body from one region to another when amount of energy at one location is greater than the amount of energy at another location.
What is the volume flow rate?
Answer: Volume flow rate is the volume of fluid moving through a point during a particular time.Volumetric flow rate is also known as flow
What is energy?
Answer: Energy is the ability to do work.
There are different forms of energy such as kinetic energy, potential energy, and gravitational energy.
What is the energy gradient?
Answer: When energy at one location is greater than the energy at another location, an energy gradient is present. Blood flows in the body due to energy gradient.
What is kinetic energy?
Answer: Kinetic energy is associated with moving objects and is determined by two factors, the mass of the object and the speed at which it moves.
A heavy object moving fast has more kinetic energy than a lighter object moving at the same speed.
Kinetic energy is the energy of movement. If something is moving, it has kinetic energy.
The amount of kinetic energy depends on two things:
- Mass – Heavier objects have more kinetic energy.
- Speed – Faster-moving objects have more kinetic energy
What is potential energy?
Answer: Potential energy is a form of stored energy. Potential energy is the major form of energy in the circulatory system. It provides energy to blood to flow and overcome the resistance to blood flow due to different factors such as viscosity, friction and inertial loss.
What is pressure?
Answer: Pressure is the force per unit area exerted by ultrasound waves as they propagate through a medium.
The unit of pressure in ultrasound is the Pascal (Pa).
What is the pressure gradient?
Answer: Pressure Gradient is the pressure difference between two pressure locations.
The formula for calculating pressure gradient is:
pressure gradient = flow x resistance
The pressure gradient increases when the flow increases or resistance to flow increases.
What is gravitational energy?
Answer: Gravitational energy is a form of stored energy. All elevated objects have stored gravitational energy that can do work.
What are the three causes of energy loss as blood flows through the circulation?
Answer: The three causes of energy loss as blood flows through the circulation are
1. friction loss
2. inertial loss
3. viscous loss
What is frictional energy loss?
Answer: Friction energy loss is the conversion of flow energy into heat energy which decreases the total energy of blood as it flows through the circulation. Friction loss occurs when one object rubs against another such as blood cells sliding against vessel wall or red blood cells sliding against each other.
What is viscous energy loss?
Answer: Viscous energy loss is the loss of fluid energy from friction between molecules of the fluid as they slide by each other. Viscous loss decreases the total energy of blood as it flows through the circulation.
What is viscosity?
Answer: Viscosity is described as thickness of a fluid. Viscosity is the resistance to flow offered by the fluid in motion. The higher the viscosity of the fluid, the greater is the energy loss.
Honey is more viscous compared to water.
The unit of viscosity is Poise.
What is inertial energy loss?
Answer: Inertial energy loss is a form of energy loss that occurs when the speed of an object changes.
The energy is lost when blood flows through bifurcations or stenotic regions. The energy is also lost when blood speeds up and slows down such as in arterial circulation during systole and diastole.
What is hematocrit?
Answer: The hematocrit is the percentage of blood cells present in the blood compared to plasma. The normal hematocrit level is 45%.
What is the effect of lower hematocrit level on viscosity of blood?
Answer: The viscosity of the blood is reduced, and the blood becomes thinner when the hematocrit level is low in blood such as in anemia.
What is the effect of higher hematocrit level on viscosity of blood?
Answer: The viscosity of the blood is increased, and the blood becomes thicker when the hematocrit level is high in blood such as in erythrocytosis.
What is velocity?
Answer: Velocity is the speed at which fluid or blood moves from one location to another.
The unit of velocity is any distance divided by time such as m/sec.
What is Flow?
Answer: Flow is the volume of the fluid or blood moving from one location to another during a particular time. Flow indicates the volume of a fluid or blood passing a point during a particular time. Flow is also known as Volumetric Flow Rate (Q).
Volumetric flow rate is determined by the pressure difference divided by resistance.
volumetric flow rate = pressure difference/resistance
The unit of flow is any volume divided by time such as l/min.
What is steady flow?
Answer: Steady flow occurs when the fluid or blood moves at the same speed. There is no acceleration or deceleration because of cardiac contractions or respiratory changes. An example of steady flow is water flowing through a garden hose.
What is pulsatile flow?
Answer: Pulsatile flow happens when the fluid or blood moves with a variable velocity.
The blood flow accelerates and decelerates in the blood vessel. Pulsatile flow is seen in arterial circulation and is caused by the contraction of the left ventricle.
What is phasic flow?
Answer: Phasic flow occurs when the fluid or blood moves with a variable velocity.
The blood flow accelerates and decelerates in the blood vessel. Phasic flow is seen in venous circulation and is caused by the changes in thoracic pressure as a result of breathing.
What is laminar flow?
Answer: Laminar flow is an orderly, layered pattern of movement.
Laminar flow is characterized by layers of blood that slide over each other and travel at individual speeds. Laminar flow patterns are commonly found in normal physiologic states.
What is plug flow?
Answer: Plug flow occurs when all layers of blood in a vessel flow with same speed and direction.
