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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

40

Flow may be measured using a pneumotachograph

True