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
To determine the amount of CO2 dissolved in blood,
PaCO2 X 0.067 =___ mL/100 mL
Squeezing an ambu bag is an example of which empirical gas laws?
Boyle’s law
During inspiration, thoracic volume is increased and the pressure goes down. During expiration, thoracic volume decreases and pressure goes up.
Inflatable cuff of larungeal mask airway expanding when placed into a autoclave is an example of which empirical gas laws?
Charle’s law
Hot air balloon is an example of which empirical gas laws?
Charle’s law
Tire pressure warning in winter is an example of which empirical gas laws?
Gay Lussac’s law
Pressure is directly proportional to absolute temperature . Volume is CONSTANT.
Alveolar gas equation
PAO2 =PIO2-PACO2 /R
PAO2= alveolar PO2
PIO2= inspired PO2
PACO2= alveolar PCO2=arterial PCO2
R=respiratory quotient (0.8)
Avogadro’s number
6.022 x 10 ^23
occupies 22.4 L for every gas. All gasses have the same volume. Ex. two moles of N2O occupies 22.4 L x 2= 44.8 L
Law of Laplace (cylindrically shaped structures)
- tension is generated by a structure (newton/cm)
- If the cylindrical structure expands (increase radius), the tension (force) in the wall (T) of the structure increases
ex: aortic aneurysm more likely to rupture than normal segment of aorta
small capillaries don’t burst with High BP but the large vessels will. The greater the filing of LV, the greater the tension in the ventricular wall. The greater then tension the greater the SV. Small diameter capillaries do not burst during the high BP and larger vessel may.
Law of laplace for cylindrical shaper structures formula
T=P x r
Law of laplace for spherically shaped structures formula
T= (P x r )/2
Law of laplace for spherically shaped structures
- Tension is independent of radius of all spheres where there is liquid-air interface
- Because tension is independent of size, pressure inside the bubble will change with size
Smaller Smaller alveoli have higher pressure and will empty into larger alveoli (like soap bubbles) leading to
atelectasis without surfactant
Fick’s law of diffusion
- directly proportional to pressure gradient, membrane area and has solubility
- inversely proportional to membrane thickness and square root of molecular weight
- P is the driving force for diffusion
Flow is directly ____ to the ___ power of radius
proportional; 4th
In polycythemia, viscosity _____ and flow ________
increases, decreases
In anemia, viscosity _____ and flow ________
decreases, increases
If someone has high BP,
they have to work x16 harder to keep the flow going.
How do you apply Poiseuille’s law while transfusing packed RBCs?
lower gauge (Increased diameter), shorter length, pressure bag, dilution by adding normal saline (to decrease viscosity).
Flow becomes turbulent if
-Velocity of flow is high
-Tube wall is rough (corrugated)
-Kinks, bends, narrowing or branches in the tube
-Fluid flow through orifice
Increased resistance = for breathing
increased WOB
Coanda application
-mucous plug in respiratory tree
-lift of airplane
-atherosclerotice plaque
Flow is ______ proportional to r^4
directly
Flow is ______ proportional to delta P
directly
Flow is ______ proportional to viscosity
inversely
Flow is ______ proportional to L (length)
inversely
How much O2 is dissolved when PO2 is 100 mmHg?
100 X 0.003 = 0.3 mL/100 mL of blood
How much O2 is dissolved when PO2 is 500 mmHg?
500 X 0.003 = 1.5 mL/ 100 mL of blood
How much PaO2 when FiO2 is 40%
estimate
40 X 5 =200 mmHg
How much CO2 is dissolved when PO2 is 50 mmHg?
50 X 0.067 = 3.35 mL/100 mL of blood
CO2 is _____ solubility compared to O2
high
Decompression sickness
think air embolism
Partial pressure application. How is it calculated?
760 X partial pressure/vapor pressure/FiO2 =
atelactasis in the patient with ARDS is explained by ______ law
Laplace
Why can turning on the N2O cause an increase in volume in gas spaces in the body?
NO2 has low blood gas. equals high pressure in the alveoli. leads to quick induction
Why CO2 diffuses 20 times faster across respiratory membrane then O2 ?
Low blood:gas partition coefficient
-rapid rise of partial
pressure rapid transfer of gas from lungs to blood and brain
rapid onset and recovery ( Example nitrous oxide)
– N2O quickly leaves the blood and increase partial pressure in
alveoli
High blood:gas partition coefficient
slow rise of partial
pressure slow transfer of gas from lungs to blood and brain
slow onset and recovery ( Example halothane)
– Once dissolve in blood , the anesthetic agent will exert NO partial
pressure.
The most potent inhalational anesthetics have
low blood solubility
-high lipid solubility
The least potent inhalational anesthetics have
- high blood solubility
- low lipid solubility
