Flashcards in Flow Deck (40)
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1
Regarding the flow of gases A carrier gas with lower density is likely to increase flow
True. The lower the density of a fluid, the greater the flow in turbulent conditions.
2
Regarding the flow of gases In laminar flow, flow depends on viscosity
True
3
Regarding the flow of gases In laminar flow, gas flow is proportional to the fourth power of the radius
True
4
Regarding the flow of gases In turbulent flow, flow is inversely proportional to the square root of pressure
False. In turbulent flow, flow is directly proportional to the square root of pressure and inversely proportional to the square root of density (ρ).
5
Regarding the flow of gases Resistance is inversely proportional to the length of a tube
False. Resistance is directly proportional to the length of the tube.
6
Regarding the flow of gases Endotracheal tube adaptors (e.g. Magill) are specifically designed to avoid turbulent flow
False. Magill adaptors are not specifically designed to avoid turbulent flow and may add to resistance in the circuit.
7
Regarding the flow of gases Helium increases the density of inspired gases and therefore the likelihood of turbulent flow within the respiratory system
False. When helium is used as part of heliox, it lowers the density compared to the same proportional volume of nitrogen in air. Therefore, it improves gas flow within the upper airways where flow is turbulent.
8
Regarding the flow of gases If Reynold's number exceeds 1000, turbulent flow is likely to be present
False. A Reynold's number greater than 2000 indicates increased likelihood of turbulent flow.
9
Regarding the flow of gases The critical velocity at which laminar flow changes to turbulent flow varies only with the gas involved
False. The critical velocity occurs at a Reynold's number of 2000, so the likelihood of turbulence depends on fluid density, viscosity, velocity and tube diameter.
10
Regarding the flow of gases Turbulent flow can only be measured using vane meters
False. Turbulent flow can be measured using multiple techniques.
11
A pneumotachograph May consist of a large number of smaller tubes
True
12
A pneumotachograph May contain a differential pressure transducer
True
13
A pneumotachograph Is not affected by the gas viscosity
False. Output is affected by viscosity.
14
A pneumotachograph May give an erroneous reading in the presence of condensed water vapour
True
15
A pneumotachograph Works on the principle of Poiseuille's law
True
16
Regarding gas or liquid flow:
In laminar flow, flow is determined by the pressure gradient divided by resistance
True
17
Regarding gas or liquid flow:
In a laminar flow, resistance is constant and independent of flow
True
18
Regarding gas or liquid flow:
Resistance increases with flow in turbulent flow
True
19
Regarding gas or liquid flow:
Hagen-Poiseuille's law does not apply in turbulent flow
True
20
Regarding gas or liquid flow: Flow through an orifice is always laminar
False. Flow through an orifice is always turbulent.
21
Flow is laminar in tubes that are very long compared with their diameter
True. In the rotameter, at low flows, the bobbin is at the narrower end of the tube, so the gas flows across an obstruction of greater length than diameter, i.e. the gas behaves as if flowing through a tube and flow is laminar.
22
Flow is turbulent when Reynold's number is <2000
False. Flow is turbulent when Reynold's number is >2000.
23
Flow through an orifice is influenced by the density of a fluid or gas
True
24
Velocity is higher and pressure is lower at the point of constriction in a tube
True
25
At low haematocrit, blood flow is better in blood vessels
True
26
Flow Is doubled by doubling the length of a tube
False. If the length of a tube is doubled, then the flow is halved.
27
Flow Is doubled by quadrupling the radius
False. Flow increases 16 times by doubling the radius according to the Hagen-Poiseuille equation (remember r to the fourth power).
28
Flow May be reduced by using an agent with a higher density
True
29
Flow Is raised if the viscosity is raised
False. If viscosity increases, flow is decreased, according to the Hagen-Poiseuille equation.
30
Flow Is determined by the Hagan-Pousseille equation
True
31
The Venturi effect Is related to kinetic energy and potential energy
True
32
The Venturi effect Is related to potential energy and gravitational energy
False. The Venturi effect is based on the Bernoulli principle, so is related to potential and kinetic energy not gravitational energy.
33
The Venturi effectIs used in nebulizers
True
34
The Venturi effect Uses a fall in kinetic energy
False. The Venturi effect, is based on the Bernoulli principle, where a drop in pressure (analogous to potential energy) is accompanied by a rise in flow (analogous to kinetic energy). Venturi masks use this principle to increase flow by entraining a second fluid into the flow path of the driving fluid.
35
The Venturi Effect Uses a fall in potential energy
True
36
Flow may be measured by a pressure drop across an orifice
True
37
Flow may be measured by using ultrasound
True
38
Flow may be measured by high frequency sound wave reflection
True
39
Flow may be measured using a bell spirometer
True
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