Chapter 5 and 6 chem/physics Flashcards
What are fluids and what affects their flow?
- any material that has the ability to flow
- both gases and liquids are considered fluids
- basic forces like gravity and pressure differences cause fluids to flow
- when in a container they take the shape of that container
what is hydrostatics?
- the study of fluids that are not moving
What is hydrodynamics?
- study of fluids in motion
What is poiseuilles law?
- laminar flow
- bigger IV increases flow
- shorter length can increase flow
- increasing the hydrostatic pressure in the IV bag by increase it height increase flow
What is laminar flow?
- is streamlined (in a straight line)
Reynolds number
- predicts whether flow will be laminar or turbulent
- directly proportional to fluid velocity, tube diameter, and fluid density
- inversely proportional to fluid viscosity
What number does Reynolds number greater than to be considered turbulent ?
> 2000
When flow is turbulent _____ not viscosity determines flow
- density
- (turbulent flow is inversely proportional to density)
Why is helium vs heliox different and what can they be used for? how does it effect flow?
- Helium has a low density so heliox decreases the work of breathing and restores laminar flow (obstruction causes flow to be turbulent so a low density gas mixture makes breathing easier)
- asthma attacks
how is laminar flow proportional to viscosity
inversely
(think about how this affects polycythemia and anemia)
how is turbulent flow proportional to density
inversely
Turbulent flow causes what?
- audible vibration called Bruits
- high velocities
- sharp turns in the circulation
- rough surfaces int he circulation
- rapid narrowing of blood vessels
How is turbulence increased?
- blood viscosity
- blood velocity
What is the coanda effect?
- tendency of fluid to flow to follow a curved surface upon emerging from a constriction
- causes a preferential flow in one tube at a bifurcation
Pascals principle
- pressure applied to a confined fluid increases the pressure throughout the fluid by the same amount
Bernoulli principle/ venturi effect use examples
venturi oxygen mask, nebulizer, jet ventilator and injectors
How does Bernoulli’s principle and/or venturi effect work?
When velocity increases the pressure drops.
Hypertrophic cardiomyopathy
normally no symptoms but with exercise the velocity of the blood flow is high so the pressure drops. The walls can snap shut and they suddenly die
is turbulent flow streamlined?
no.
Resistance to flow equation
R= P/F
R=resistance
F=flow
P=pressure
How does radius affect laminar flow?
When radius is doubled, the resistance will decrease 16 folds
Henry’s law
-amount of gas that dissolves in a liquid is proportional to the partial pressure (P) of the gas.
- this allows calculation of dissolved O2 and CO2 in the blood
Solubility
gas partition coefficient is useful index of solubility. It defined the relative affinity of an anesthetic agent for the blood compared to air
Graham’s law of effusion
- Diffusion is net movement of a gas from an area of high concentration (pressure) to an area of lower concentration
- effusion is the movement of a gas through a pinhole
-the rate of effusion is inversely proportional to the square root of the molecular weight
To determine the amount of O2 dissolved in blood,
PaO2 X 0.003 = mL/100 mL