Deck 6: Physical Principles of Respiratory Care

Question 1

What is the physical process whereby the gaseous form of a substance is changed back into its liquid state?

A) Condensation
B) Sublimation
C) Vaporization
D) Radiation

Answer 1

A
Explanation: During condensation, a gas turns back into a liquid.

Question 2

Which of the following is false about evaporation?

A) Evaporation is a type of vaporization.
B) The process of evaporation warms the surrounding air.
C) Evaporation is the change of a liquid substance into a gas.
D) For evaporation to occur, heat energy is needed.

Answer 2

B
Explanation: Vaporization is the change of state from liquid to gas. Vaporization requires heat energy. According to the first law of thermodynamics, this heat energy must come from the surroundings. In one form of vaporization, called evaporation, heat is taken from the air surrounding the liquid, thereby cooling the air.

Question 3

Which of the following statements correctly describe gases?
1) Gases exhibit the phenomenon of flow.
2) Molecular forces of attraction are minimal.
3) Gases are difficult to compress.
4) Gases expand to fill their container.

A)1 and 2 only
B)1, 2, and 4 only
C)2, 3, and 4 only
D)3 and 4 only

Answer 3

B

Question 4

A near-drowning patient has a recorded body temperature of 30° C. What is the equivalent temperature in degrees Fahrenheit?

A) -4° F
B) 86° F
C) 32° F
D) 77° F

Question 5

Archimedes' principle is applied clinically in which of the following devices?

A) Nebulizer
B) Capillary tube
C) Hydrometer
D) Humidifier

Question 6

What is the primary means by which heat transfer occurs in fluids?

A) Convection
B) Radiation
C) Conduction
D) Evaporation

Question 7

At what temperature do all kinetic activities of matter cease?

A) 0 K
B) 0° C
C) 32° C
D) 0° F

Question 8

After placing a liquid into a small-diameter glass tube, you observe the formation of a convex (upwardly curved) meniscus. What conclusion is correct?

A) The liquid must have a very low surface tension.
B) Strong adhesive forces exist between the liquid and glass.
C) The liquid must have an extremely high viscosity.
D) Strong cohesive forces exist among the liquid molecules.

Question 9

What is the internal force that opposes the flow of fluids (equivalent to friction between solid substances)?

A) Conductivity
B) Kinetic energy
C) Viscosity
D) Density

Question 10

Which of the following is a good clinical example of using the principle of convection to transfer heat?

A) Humidifiers with immersion heaters
B) Heated, enclosed infant incubators
C) Wire-heated pneumotachometers
D) Heated ventilator exhalation valves

Question 11

Which of the following would be the worst heat conductor?

A) Water
B) Glass
C) Air
D) Copper

Question 12

By which of the following means can the internal energy of a substance be increased?
1) Cooling the substance
2) Performing work on the substance
3) Heating the substance

A)2 and 3 only
B)1 and 2 only
C)2 only
D)1, 2, and 3

Question 13

What term is used for the transfer of heat by the direct interaction of atoms or molecules in a hot area with atoms or molecules in a cooler area?

A) Radiation
B) Convection
C) Condensation
D) Conduction

Question 14

Which of the following equations can be used to calculate the pressure exerted by a liquid?

A) Liquid pressure = liquid depth ÷ liquid density
B) Liquid pressure = liquid depth $\times$ surface area
C) Liquid pressure = liquid density $\times$ liquid viscosity
D) Liquid pressure = liquid density $\times$ liquid depth

Question 15

Which of the following are true of liquids?
1) They are easy to compress.
2) They exert pressure.
3) They exert buoyant force.
4) They conform to their containers.

A)2 and 4 only
B)1, 2, and 3 only
C)1 and 3 only
D)2, 3, and 4 only

Question 16

Which of the following would help to decrease a patient's loss of body heat?
1) Increase the temperature of the room.
2) Increase the exposed skin surface area.
3) Move the patient away from cold windows.

A)1 and 2 only
B)2 and 3 only
C)1, 2, and 3
D)1 and 3 only

Question 17

Which of the following is false about viscosity?

A) The greater the viscosity, the greater is the opposition to flow.
B) Viscosity is most important under conditions of turbulent flow.
C) The stronger the cohesive forces, the greater the viscosity.
D) Fluid viscosity is equivalent to friction between solids.

Question 18

A patient has a recorded body temperature of 106° F. What is this temperature in degrees Celsius?

A) 41° C
B) 98° C
C) 39° C
D) 22° C

Question 19

According to Pascal's principle, the pressure exerted by a liquid in a container depends on which of the following?
1) Depth of the liquid
2) Density of the liquid
3) Shape of the container

A)1, 2, and 3
B)1 and 2
C)2 and 3
D)1 and 3

Question 20

Which of the following methods of heat transfer requires no direct contact between the warmer and cooler substances?

A) Conduction
B) Convection
C) Evaporation
D) Radiation

Question 21

What occurs during the evaporation of water?

A) The adjacent air is warmed.
B) The adjacent air is cooled.
C) The water temperature rises.
D) Heat is given up to the air.

Question 22

What is the term for the temperature at which the water vapor in a gas begins to condense back into a liquid?

A) Triple point
B) Critical pressure
C) Dew point
D) Boiling point

Question 23

What is the absolute humidity (water vapor content) of saturated gas at normal body temperature (37° C)?

A) 47.0 mg/L
B) 37.0 mg/L
C) 98.6 mg/L
D) 43.8 mg/L

Question 24

The ratio of the density of one fluid when compared with the density of another reference substance, which is typically water, describes the fluid's:

A) specific gravity.
B) specific weight.
C) atomic mass.
D) atomic volume.

Question 25

What is the temperature at which the vapor pressure of a liquid equals the pressure exerted on the liquid by the surrounding atmosphere?

A) Boiling point
B) Dew point
C) Triple point
D) Melting point

Question 26

Which of the following are true about molecular water vapor?
1) Water vapor exhibits kinetic activity.
2) Molecular water vapor can be seen.
3) Water vapor exerts pressure.

A)1 and 2 only
B)2 and 3 only
C)1, 2, and 3
D)1 and 3 only

Question 27

Which of the following methods would increase the rate of evaporation of a container of water?
1) Increase the temperature of the surrounding air.
2) Decrease the pressure of the surrounding air.
3) Increase the temperature of the water.

A)1 and 2
B)2 and 3
C)1 and 3
D)1, 2, and 3

Question 28

What is the term for the ratio of the actual water vapor present in a gas compared with the capacity of that gas to hold the vapor at a given temperature?

A) Relative humidity
B) Absolute humidity
C) Water vapor pressure
D) Percent body humidity

Question 29

What force is responsible for the spherical shape of liquid droplets and their ability to keep this shape when placed into an aerosol suspension?

A) Cohesion
B) Adhesion
C) Viscosity
D) Surface tension

Question 30

A gas at 50° C with a relative humidity of 100% is cooled to 37° C. Which of the following will occur?
1) Condensation on surfaces
2) Visible droplet formation
3) Warming of the adjacent air

A)1, 2, and 3
B)1 and 2 only
C)1 and 3 only
D)2 and 3 only

Question 31

Which of the following are true about boiling?
1) Boiling a liquid requires more energy than does evaporating it.
2) A liquid's boiling point varies with the atmospheric pressure.
3) The greater the ambient pressure, the lower is the boiling point.

A)2 and 3 only
B)1 and 3 only
C)1 and 2 only
D)1, 2, and 3

Question 32

What is the phenomenon whereby a liquid in a small tube tends to move upward against the force of gravity?

A) Capillary action
B) Shear stress
C) Surface tension
D) Buoyancy

Question 33

Which of the following represents a direct measure of the kinetic activity of water vapor molecules?

A) Absolute humidity
B) Water vapor pressure
C) Percent body humidity
D) Relative humidity

Question 34

What is the change in state of a substance from liquid to gaseous form occurring below its boiling point?

A) Evaporation
B) Sublimation
C) Boiling
D) Vaporization

Question 35

What is the water vapor pressure of saturated gas at normal body temperature (37° C)?

A) 47.0 mm Hg
B) 43.8 mm Hg
C) 37.0 mm Hg
D) 98.6 mm Hg

Question 36

Which of the following is/are good clinical example(s) of the principle of capillary action?
1) Capillary stick blood samples
2) Absorbent humidifier wicks
3) Certain surgical dressings

A)1, 2, and 3
B)1 and 2 only
C)2 and 3 only
D)2 only

Question 37

What is the equilibrium condition in which a gas holds all the water vapor molecules that it can?

A) Evaporation
B) Stabilization
C) Saturation
D) Body humidity

Question 38

At a room temperature of 22° C, air has the capacity to hold 19.4 mg/L of water vapor. If the absolute humidity in the air is 7.4 mg/L, then what is the relative humidity (RH)?

A) 45%
B) 58%
C) 70%
D) 38%

Question 39

What is the term for the actual content or weight of water present in a given volume of air?

A) Percent body humidity
B) Water vapor pressure
C) Absolute humidity
D) Relative humidity

Question 40

When the water vapor content of a volume of gas equals its capacity, what is the relative humidity (RH) of this gas?

A) 80%
B) 100%
C) 40%
D) 60%

Question 41

The American National Standards Institute has set a water vapor content level of 30 mg/L as the minimum absolute humidity required for patients whose upper airways have been bypassed. This equals what body humidity (BH)?

A) 68%
B) 47%
C) 75%
D) 100%

Question 42

The peak pressure on a ventilator reads 30 cm H₂O. What is the equivalent pressure in kilopascals (kPa)?

A) 37.0 kPa
B) 68.0 kPa
C) 4.9 kPa
D) 2.9 kPa

Question 43

Which of the following occurs when the temperature of a gas rises?
1) The kinetic activity of the gas increases.
2) The rate of molecular collisions increases.
3) The pressure exerted by the gas rises.

A)1, 2, and 3
B)1 and 2 only
C)2 and 3 only
D)3 only

Question 44

From a bedside capnograph (CO₂ measuring device), you obtain a "dry" gas reading of 5.3% CO₂ in a patient's exhaled gas. Given a barometric pressure of 765 mm Hg, what is the partial pressure of CO₂ in this patient's exhaled gas?

A) 347 mm Hg
B) 41 mm Hg
C) 164 mm Hg
D) 35 mm Hg

Question 45

In the lung's alveoli, there are four gases mixed together: O₂, carbon dioxide, nitrogen, and water vapor. At a normal barometric pressure of 760 mm Hg, alveolar O₂ exerts a partial pressure of 100 mm Hg, CO₂ 40 mm Hg, and water vapor 47 mm Hg. What is the alveolar partial pressure of nitrogen?

A) 187 mm Hg
B) 713 mm Hg
C) 660 mm Hg
D) 573 mm Hg

Question 46

Which of the following best describes the physical concept of pressure?

A) Weight ÷ unit volume
B) Mass $\times$ acceleration
C) Force $\times$ distance
D) Force ÷ unit area

Question 47

What occurs when the temperature of a saturated gas drops down to its dew point?

A) Excess water vapor will condense as visible droplets.
B) The temperature of the surrounding air decreases.
C) Any liquid water present will quickly evaporate.
D) The relative humidity of the gas begins to decrease.

Question 48

What is the common British unit of pressure?

A) Newton (N)/m²
B) dyne/cm²
C) Pascal (Pa)
D) lb/in² (psi)

Question 49

According to Avogadro's law, which of the following is/are TRUE?
1) One gram of any substance contains the same number of particles.
2) Equal volumes of gases at standard temperature, standard pressure, dry (STPD) have the same number of molecules.
3) Equal numbers of gas molecules at STPD occupy the same volume.

A)1 and 2 only
B)1, 2, and 3
C)2 and 3 only
D)1 only

Question 50

What is the density of a mixture of 40% oxygen (O₂) and 60% helium at STPD?

A) 0.34 g/L
B) 0.55 g/L
C) 0.68 g/L
D) 1.25 g/L

Question 51

One atmosphere (1 atm) of pressure is equivalent to which of the following?
1) 29.9 in Hg
2) 14.7 lb/in²
3) 1034.0 g/cm²
4) 760.0 mm Hg

A)1, 2, and 3
B)2 and 4
C)1 and 3
D)1, 2, 3, and 4

Question 52

What is the physical process whereby atoms or molecules tend to move from an area of higher concentration or pressure to an area of lower concentration or pressure?

A) Sublimation
B) Melting
C) Diffusion
D) Capillary action

Question 53

In International System (SI) units, what is any quantity of matter that contains 6.023 $\times$ 10²³ atoms, molecules, or ions?

A) Pound (lb)
B) Gram (g)
C) Ounce (oz)
D) Mole (mol)

Question 54

If the absolute humidity in a medical gas being delivered to a patient is 14 mg/L, then what is the body humidity (BH)?

A) 7%
B) 16%
C) 24%
D) 32%

Question 55

What is the term for the ratio of the amount of water vapor in a volume of gas compared to the amount of the water in gas saturated at a normal body temperature of 37° C?

A) Percent body humidity (BH)
B) Relative humidity (RH)
C) Absolute humidity
D) Water vapor pressure

Question 56

Which of the following factors determine how much of a given gas can dissolve in a liquid?
1) Solubility coefficient of the gas
2) Temperature of the liquid
3) Gas pressure above the liquid

A)2 and 3 only
B)1 and 2 only
C)1 and 3 only
D)1, 2, and 3

Question 57

According to Avogadro's law, under standard conditions of temperature and pressure (0° C and 760 mm Hg), 1 mol of any gas occupies which of the following?

A) 1.34 L
B) 22.40 L
C) 7.48 L
D) 28.30 L

Question 58

Which of the following properties of gases distinguish them from liquids-that is, are unique to the gaseous phase of matter?
1) Gases fill the available space.
2) Gases exhibit viscosity.
3) Gases exert pressure.
4) Gases are readily compressed.

A)2, 3, and 4 only
B)1 and 3 only
C)2 and 4 only
D)1 and 4 only

Question 59

You obtain a mercury barometric reading of 760 mm Hg at 17° C. Using the following factor table, compute the corrected pressure.

A) 223.0 mm Hg
B) 747.7 mm Hg
C) 757.8 mm Hg
D) 762.3 mm Hg

Question 60

The peak pressure on a ventilator reads 40 cm H₂O. What is the equivalent pressure in mm Hg?

A) 37.0 mm Hg
B) 29.6 mm Hg
C) 68.3 mm Hg
D) 4.9 mm Hg

Question 61

Which of the following medical gases can be maintained in the liquid form at room temperature?
1) Nitrous oxide
2) Carbon dioxide
3) O₂
4) Helium

A)1 and 2 only
B)2, 3, and 4 only
C)2 and 3 only
D)2 and 4 only

Question 62

The resistance to flow of a fluid through a tube can be computed according to which of the following formulas?

A) Resistance = flow $\times$ viscosity
B) Resistance = flow ÷ pressure
C) Resistance = pressure ÷ flow
D) Resistance = flow $\times$ pressure

Question 63

Which of the following will occur when a gas undergoes expansion?
1) The pressure of the gas increases.
2) Molecular collisions decrease.
3) The gas temperature increases.

A)1 and 2 only
B)2 and 3 only
C)2 only
D)1 and 3 only

Question 64

What is the pattern of flow in which a fluid moves in discrete cylindrical streamlines?

A) Transitional
B) Turbulent
C) Laminar
D) Tracheal

Question 65

A combination of neutral atoms, free electrons, and atomic nuclei describes:

A) potential energy.
B) kinetic energy.
C) plasma.
D) compressed gases.

Question 66

Assuming a constant flow, what will happen to a fluid if the cross-sectional area of the tube in which its flows decrease?

A) Its velocity will increase.
B) Its velocity will decrease.
C) Its density will decrease.
D) Its viscosity will decrease.

Question 67

Which of the following is a false statement about O₂?

A) No pressure can keep it in a liquid state above -118.8° C.
B) Below its boiling point, it remains liquid at ambient pressure.
C) Its critical temperature is above normal room temperature.
D) It cannot be turned into a liquid at room temperature.

Question 68

With all else equal, under which of the following conditions would the drop in pressure occurring while a fluid flows through a tube be greatest?

A) A; Small; Low
B) B; Large; Low
C) C; Large; High
D) D; Small; High

Question 69

Both a compressed gas cylinder and its regulator are at room temperature with all valves in the off position. After the cylinder is opened and gas begins flowing, you note that the regulator is extremely cold to touch. Which of the following principles best explains this observation?

A) Adiabatic compression
B) Gay-Lussac's law
C) Joule-Thompson effect
D) Venturi principle

Question 70

In what processes of gas compression or expansion does the temperature remain constant?

A) Isothermal
B) Adiabatic
C) Hypothermal
D) Neutral kinetic

Question 71

Which of the following occur(s) when water vapor is added to a dry gas at a constant pressure?
1) The volume occupied by the gas mixture decreases.
2) The relative humidity of the mixture increases.
3) The partial pressure of the original gas is reduced.

A)1 and 2 only
B)1 and 3 only
C)1, 2 and 3
D)3 only

Question 72

According to Poiseuille's law, the pressure needed to drive a fluid through a tube will increase under which of the following conditions?
1) Increased fluid viscosity
2) Decreased tube length
3) Decreased rate of flow
4) Decreased tube radius

A)1 and 2
B)2, 3, and 4
C)1 and 4
D)1, 3, and 4

Question 73

At 37° C and 760 mm Hg pressure, 0.023 ml of O₂ can be dissolved in 1 ml of plasma, whereas at the same temperature and pressure, 0.510 ml of CO₂ will dissolve in 1 ml of plasma. What explains this difference?

A) CO₂ diffuses more rapidly than O₂.
B) CO₂ is more soluble in plasma than O₂.
C) CO₂ has a greater molecular weight than O₂.
D) O₂ has less affinity for plasma than CO₂.

Question 74

Under conditions of turbulent flow, what is the driving pressure?

A) Proportional to the square of the flow
B) Inversely proportional to the flow
C) Linearly proportional to the flow
D) Inversely proportional to the density

Question 75

Which of the following conditions tend to cause laminar flow to become turbulent (producing a high Reynold's number)?
1) High linear gas velocity
2) High gas density
3) Low gas viscosity
4) Smaller tube diameter

A)2, 3, and 4 only
B)2 and 3 only
C)1, 2, and 3 only
D)1 and 4 only

Question 76

What temperature is necessary to liquefy O₂ at 1 atm pressure?

A) -118.8° C
B) -181.1° F
C) -463.3° F
D) -183.0° C

Question 77

During some pulmonary function tests, saturated gas exhaled from a patient's lungs is gathered at room temperature. Which of the following correction-factor tables would you use to determine what volume this gas occupied in the patient's lungs?

A) Standard temperature, standard pressure, dry (STPD) to body temperature, ambient pressure, saturated (BTPS)
B) BTPS to STPD
C) Ambient temperature, ambient pressure, saturated (ATPS) to BTPS
D) ATPS to STPD

Question 78

If a given mass of a gas is maintained at a constant temperature, what will decreasing its pressure do?

A) Decrease its volume.
B) Increase its mass.
C) Increase its volume.
D) Decrease its mass.

Question 79

For every liquid there is a temperature above which the kinetic activity of its molecules is so great that the attractive forces cannot keep them in a liquid state. This temperature is called the:

A) critical temperature.
B) melting point.
C) flash temperature.
D) triple point.

Question 80

Respiratory therapists must ensure that any oil or dust is cleared from high-pressure medical-gas delivery systems before pressurization. Why is this action needed?

A) Inhaled dust particles can cause pneumoconiosis.
B) The oil or dust can cause a leak in the system.
C) Oil or dust does not easily mix with medical gases.
D) Adiabatic compression could ignite the oil or dust.