Chapter 39

Question 1

What is the point in the respiratory track where inspired gas reaches body temperature, ambient pressure, saturated (BTPS) conditions?
a. point of thermal equilibrium
b. hygroscopic saturation boundary
c. thermal inversion boundary
d. isothermic saturation boundary

Question 2

Which of the following is FALSE about the isothermic saturation boundary (ISB)?
a. Below the ISB, temperature and relative humidity remain constant.
b. Above the ISB, temperature and humidity increase during exhalation.
c. The ISB is normally located just below the larynx (vocal cords).
d. Above the ISB, temperature and humidity decrease during inspiration

Question 3

Which of the following factors cause the isothermic saturation boundary (ISB) to shift farther down into the airways?
1. decreased ambient temperature
2. increased tidal volume (VT)
3. endotracheal intubation
a. 1 and 2
b. 2 and 3
c. 1 and 3
d. 1, 2, and 3

Question 4

What is the primary goal of humidity therapy?
a. decrease airway reactivity to cold
b. maintain normal physiologic conditions
c. deliver drugs to the airway
d. reduce upper airway inflammation

Question 5

Indications for warming inspired gases include all of the following except:
a. treating a patient whose airways are reactive to cold
b. providing humidification when the upper airway is bypassed
c. treating a patient with a low body temperature (hypothermia)
d. reducing upper airway inflammation or swelling

Question 6

Administration of dry gases at flows exceeding 4 L/min can cause which of the following?
1. structural damage
2. heat loss
3. water loss
a. 1 and 2
b. 2 and 3
c. 1 and 3
d. 1, 2, and 3

Question 7

Inhalation of dry gases can do which of the following?
1. increase viscosity of secretions
2. impair mucociliary motility
3. increase airway irritability
a. 1 and 2
b. 3
c. 1 and 3
d. 1, 2, and 3

Question 8

Which of the following inspired conditions should be maintained when delivering medical gases to the nose or mouth?
a. 50% relative humidity (RH) at 20° to 22° C
b. 100% RH at 20° to 22° C
c. 80% RH at 28° to 32° C
d. 100% RH at 32° to 35° C

Question 9

Which of the following inspired conditions should be maintained when delivering medical gases to the hypopharynx, as when administering oxygen by nasal catheter?
a. 50% relative humidity (RH) at 20° to 22° C
b. 100% RH at 20° to 22° C
c. 95% RH at 29° to 32° C
d. 100% RH at 32° to 35° C

Question 10

Which of the following inspired conditions should be maintained when delivering medical gases directly into the trachea through an endotracheal tube or a tracheotomy tube?
a. 50% relative humidity (RH) at 20° to 22° C
b. 100% RH at 37° to 42° C
c. 95% RH at 29° to 32° C
d. 100% RH at 32° to 35° C

Question 11

Clinical indications for delivering cool humidified gas include which of the following?
1. post-extubation edema
2. upper airway inflammation
3. croup (laryngotracheal bronchitis)
4. epiglottitis
a. 2, 3, and 4
b. 1, 2, and 3
c. 1, 2, 3, and 4
d. 2 and 3

Question 12

What device adds molecular water to gas?
a. agitator
b. humidifier
c. nebulizer
d. atomizer

Question 13

Factors affecting a humidifier’s performance include all of the following except:
a. surface area
b. temperature
c. time of contact
d. outlet size

Question 14

What is the most important factor determining a humidifier’s performance?
a. surface area
b. temperature
c. time of contact
d. gas flow

Question 15

The greater the temperature of the gas, the:
a. more water vapor it can hold
b. less water vapor it can hold
c. less efficient the humidifier is
d. more water vapor is lost

Question 16

Gas leaving an unheated humidifier at 10° C and 100% relative humidity (absolute humidity = 9.4 mg/L) would provide what relative humidity at body temperature?
a. about 100%
b. about 60%
c. about 40%
d. about 20%

Question 17

What is the simplest way to increase the humidity output of a humidifier?
a. Increase the time that the gas and the water are in contact.
b. Increase the surface area between the water and the gas.
c. Decrease the water vapor pressure of the gas.
d. Increase the temperature of either the water or the gas.

Question 18

Which of the following is a common way to increase the surface area ratio of humidifiers?
1. Generate a water droplet aerosol.
2. Expose the gas to a saturated wick.
3. Use a bubble or diffusion head.
a. 1 and 2
b. 2 and 3
c. 1 and 3
d. 1, 2, and 3

Question 19

All of the following are TRUE about humidification and contact time except:
a. The longer a gas is exposed to water, the greater is the amount of evaporation.
b. The rate of gas flow through a humidifier determines contact time.
c. Low flows decrease and high flows increase relative humidity output.
d. Bubble humidifier contact time depends on the water column depth.

Question 20

Which of the following types of humidifiers are used in clinical practice?
1. heat-moisture exchanger
2. passover humidifier
3. bubble humidifier
a. 1 and 2
b. 2 and 3
c. 1 and 3
d. 1, 2, and 3

Answer 20

Simple unheated bubble humidifiers are commonly used to humidify gases with what type of systems?
a. mechanical ventilation
b. oronasal oxygen delivery
c. tracheal oxygen airway
d. aerosol drug delivery

Question 21

What is the goal of using an unheated bubble humidifier with oronasal oxygen delivery systems?
a. Raise the humidity of the gas to ambient levels.
b. Fully saturate the inspired gas to body temperature, ambient pressure, saturated (BTPS) conditions.
c. Cool the gas down to below room temperature.
d. Fully saturate the inspired gas to ambient temperature, ambient pressure, saturated (ATPS) conditions

Question 22

What is the typical water vapor output of an unheated bubble humidifier?
a. 5 to 10 mg/L
b. 10 to 15 mg/L
c. 15 to 20 mg/L
d. 20 to 25 mg/L

Question 23

Increasing the flow through an unheated bubble humidifier has which of the following effects?
a. decreasing the water vapor content
b. decreasing the relative humidity
c. increasing the water vapor content
d. increasing the relative humidity

Question 24

Unheated bubble humidifiers are of limited effectiveness at flows above which of the following?
a. 4 L/min
b. 6 L/min
c. 8 L/min
d. 10 L/min

Question 25

Why should you NOT heat the reservoirs of a bubble humidifier used with an oronasal oxygen delivery system?
a. Condensate will obstruct the delivery tubing.
b. Heating will melt the reservoir or cause a fire.
c. Heating will absorb the extra water vapor.
d. Heating will causes too much aerosol impaction.