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Physics > Fluids (E1) > Flashcards

Fluids (E1) Flashcards

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1
Q

Pressure

A

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

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2
Q

Atmospheric Pressure Equivalents

A

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

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3
Q

Fluid

A

any substance that can move
(liquids and gases)

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4
Q

Liquid pressure

A

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

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5
Q

Pascal’s Principle

A

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

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6
Q

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

A

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

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7
Q

Equation difference for transducer below or above the heart

A

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

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8
Q

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

A

15 mmHg

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9
Q

gauge pressure

A

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

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10
Q

Bourdon Manometer

A

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

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11
Q

Strain Gauge

A

-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

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12
Q

absolute pressure

A

pressure measured relative to zero pressure

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13
Q

Pressure Limiting Valves

A

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

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14
Q

Pressure Reducing Valve

A

-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

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15
Q

Surface tension

A

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

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16
Q

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

A

greater than

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17
Q

Transmural pressure

A

the pressure difference between two sides of a membrane

18
Q

LaPlace’s Equation

A

(4 x surface tension) / radius

19
Q

What requires a greater force to expand a bubble?

A

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

20
Q

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

A

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

21
Q

Laplace’s equation & cardiomyopathy

A

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

22
Q

Compliance

A

-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

23
Q

What factors decrease pulmonary compliance?

A

-pulmonary edema
-interstitial lung disease

24
Q

Elastance

A

-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

25
Q

Laminar flow is dependent on which measure?

A

Viscosity

26
Q

Turbulent flow is based on what measure?

A

Density

27
Q

Conservation of mass

A

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

28
Q

Conservation of energy

A

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

29
Q

Viscosity

A

Measure of resistance of a fluid to flow

30
Q

Laminar flow

A

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

31
Q

Turbulent flow

A

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

32
Q

What makes a Reynolds number larger?

A

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

33
Q

Density

A

The amount of mass per unit volume of fluid

34
Q

Viscosity

A

The thickness of a fluid

35
Q

Poiseuille’s Law

A

-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)

36
Q

Ohm’s Law

A

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

37
Q

Thorpe Tube

A

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

38
Q

Wright Spirometer

A

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

39
Q

Pitot flow meter

A

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

40
Q

Electronic flow meter

A

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

41
Q

Flo-trak

A

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

42
Q

Thermodilution

A

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

Physics (6 decks)

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