Fluids (E1)

Question 1

Pressure

Answer 1

the force distributed over a given area that a substance exerts on an object
SI unit: Pascal (1 N/m^2)

Question 2

Atmospheric Pressure Equivalents

Answer 2

1 atmosphere (atm)
760 mmHg
1033 cmH20
14.7 psi
101,325 Pa (101 kPa)

Question 3

Fluid

Answer 3

any substance that can move
(liquids and gases)

Question 4

Liquid pressure

Answer 4

-pressure on all sides of liquid
-pressure depends on depth

Question 5

Pascal’s Principle

Answer 5

The pressure at any point in a liquid depends on…
-the pressure at the surface
-the density of the liquid
-the depth of the point in the liquid
P(atm) + pgh

Question 6

What does the pressure difference between two points in liquid depend on?

Answer 6

-the density of the liquid
-the difference in height of the two points

Question 7

Equation difference for transducer below or above the heart

Answer 7

+ (add) if transducer is higher
- (subtract) if transducer is lower

Question 8

For every 20 cm change in height, there is a _____ pressure change.

Answer 8

15 mmHg

Question 9

gauge pressure

Answer 9

pressure measured relative to atmospheric pressure
-most pressures we deal with
ex. peak airway pressure

Question 10

Bourdon Manometer

Answer 10

-volume of Bourdon tube increases with increasing pressure
-expanding Bourdon tube moves gear that moves pointer

Question 11

Strain Gauge

Answer 11

-contains deformable wires imbedded in a membrane that change the electrical current transmitted in the wire within the membrane
-stopcock open to atm: atm pressure is on both sides of membrane
-gauge pressure

Question 12

absolute pressure

Answer 12

pressure measured relative to zero pressure

Question 13

Pressure Limiting Valves

Answer 13

devices that can allow pressure to build up until a certain point
ex. APL valve

Question 14

Pressure Reducing Valve

Answer 14

-serves to reduce risk of pressure injury to the lungs
ex. located on gas cylinders, wall outlets, and in the anesthesia machine
-reduces pressure to 45-50 psi

Question 15

Surface tension

Answer 15

forces are not equal and a strong film forms on the surface of a liquid
Force = 2(surface tension)(length)

Question 16

The pressure inside a balloon is greater/less than the pressure outside.

Answer 16

greater than

Question 17

Transmural pressure

Answer 17

the pressure difference between two sides of a membrane

Question 18

LaPlace’s Equation

Answer 18

(4 x surface tension) / radius

Question 19

What requires a greater force to expand a bubble?

Answer 19

-higher surface tension (thicker rubber)
-smaller radius (smaller balloon)

Question 20

Why is the work of breathing equal in small and large alveoli in healthy lungs?

Answer 20

small alveoli: small radius (inc. work) but more concentrated surfactant (dec. work)
large alveoli: large radius (dec. work) but less concentrated surfactant (inc. work)

Question 21

Laplace’s equation & cardiomyopathy

Answer 21

Dilated CM: thinner LV wall, larger LV radius makes it easy to fill
Hypertrophic CM: thicker LV wall, smaller LV radius makes it difficult to fill

Question 22

Compliance

Answer 22

-the change in volume that occurs when pressure is increased inside a cavity
-more compliant = larger volume increase for given pressure increase
-based off the slope of a line (X=pressure, Y=volume)
C=V/P

Question 23

What factors decrease pulmonary compliance?

Answer 23

-pulmonary edema
-interstitial lung disease

Question 24

Elastance

Answer 24

-measures the change in pressure that occurs in response to a given volume change
-based on the slope of the line tangent to the curve at that point (X=volume, Y=pressure)
E=P/V

Question 25

Laminar flow is dependent on which measure?

Answer 25

Viscosity

Question 26

Turbulent flow is based on what measure?

Answer 26

Density

Question 27

Conservation of mass

Answer 27

-mass entering tube = mass exiting tube -Continuity equation A(i)V(i)=A(f)V(f)

Question 28

Conservation of energy

Answer 28

-when a fluid flows through a constriction, its velocity increases and pressure decreases -Bernoulli's equation -Modified equation Pressure change = 4v^2

Question 29

Viscosity

Answer 29

Measure of resistance of a fluid to flow

Question 30

Laminar flow

Answer 30

-fluid flows smoothly -lower flow velocities (<2000) -depends on viscosity

Question 31

Turbulent flow

Answer 31

-flow is irregular and complex -higher flow velocities (>3000) -depends on density

Question 32

What makes a Reynolds number larger?

Answer 32

-higher density -higher linear flow rate -longer tube -lower viscosity

Question 33

Density

Answer 33

The amount of mass per unit volume of fluid

Question 34

Viscosity

Answer 34

The thickness of a fluid

Question 35

Poiseuille's Law

Answer 35

-double the pressure, double the flow -decrease viscosity in half, double the flow -decrease tube length by half, double the flow -double the radius, increase flow by 2^4 (16 fold)

Question 36

Ohm's Law

Answer 36

-used to calculate SVR and PCR -flow = change in pressure / resistance -pressure mmHg and CO in L/min

Question 37

Thorpe Tube

Answer 37

-Used to measure gas flow rate -ball or bobbin with groove Ex. O2 flow meter

Question 38

Wright Spirometer

Answer 38

Gas forced to rotate a vane and a photo detector counts the number of times the light source is interrupted

Question 39

Pitot flow meter

Answer 39

-two tubes within a larger tube with openings facing in opposite directions -measure difference in pressures -based on Bernoulli's equation

Question 40

Electronic flow meter

Answer 40

-measures rate of heat transfer from heater to sensor -or measures the amount of current needed to keep the heater at a constant temperature

Question 41

Flo-trak

Answer 41

Assesses arterial waveform to estimate strike volume and cardiac output -used pulse rate not heart rate

Question 42

Thermodilution

Answer 42

Measures temperature change further along the catheter after cold saline injected at proximal point