Ch 5 - Fluids Flashcards
What is a fluid
A fluid is any material that has the ability to flow. Liquids and Gases.
What causes fluids to flow?
Basic forces such as gravity and pressure changes
What are hydrostatics
Study of fluids that are not moving
What are two properties that are useful in studying hydrostatic fluids
density (mass/volume) and pressure
What are hydrodynamics
Study of fluids in motion
Units for Pascal
N/m^2 or kg/m x s^2
What is Pascal’s Principle?
When an external pressure is applied to a confined fluid, it is transmitted unchanged to every point within the fluid.
What variable has the most significant impact on Flow?
Radius. Because we raise the radius to the fourth power.
What is the relationship between viscosity and temperature?
Inverse.
Decreased temperature increases viscosity and resistance.
Increased temperature decreases viscosity and resistance.
What are 4 ways we can deliver PRBCs faster?
-Increase radius size with large bore IV
-Increase pressure gradient with a pressure bag or increases height of IV pole
-Decrease viscosity by diluting with 0.9% NaCl or running it through a warmer
-Decrease length of tubing
Poiseuille’s Law integrates which variables.
Radius, Pressure, Length, Viscosity
Doubling the radius of an IV catheter increases flow by how much?
16 times
What effect would fever have on blood flow?
Increase in temp, decreases viscosity which reduces resistance to blood flow.
What does Reynold’s number measure?
What are the 4 variables
The type of flow: laminar, transitional, or turbulent
Density, Diameter, Velocity, Viscosity
If Reynold’s number is less than 2,000, what kind of flow is present?
Laminar
If Reynold’s number is greater than 3,000, what kind of flow is present?
Turbulent
If Reynold’s number is between 2,000 and 3,000 what kind of flow is present? Describe what this looks like.
Transitional Flow. Turbulent near the center and laminar near the walls.
2 examples of laminar flow
Systemic Blood Circulation
Airflow in terminal Bronchioles
Examples of Turbulent Flow
Flow through an orifice - an annular space or glottis.
Flow at angles - air flow through medium bronchioles
Turbulent flow is dependent on?
Gas Density - Grahams Law
Laminar Flow is dependent on?
Gas Viscosity - Pouseilles Law
A pt with status asthmaticus, epiglottitis, and bronchospasm have increased airway resistance. This increases resistance and flow turbulence, what might you do to lower flow turbulence?
Because turbulent flow is density-dependent, we can have the patient inhale a lower-density gas to reduce turbulence.
Such an oxygen-helium (Heliox) gas mixture reduces Reynolds number and can improve airflow when resistance is high.
