Humidity and Bland Aerosol Therapy

Humidity and Bland Aerosol Therapy: Overview and Practice Questions

by | Updated: Jan 28, 2023

Humidity and bland aerosol therapy is a treatment method that involves the use of aerosolized mist to treat patients with respiratory conditions. It uses a nebulizer to convert liquid into water vapor and bland aerosols that can be inhaled into the lungs.

This study guide will provide you with a brief overview of this topic and has helpful practice questions for your benefit. 

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What is Humidity Therapy?

Humidity therapy is the process of adding water vapor to an inspired gas in order to treat a pulmonary disease. It is commonly used therapeutically to loosen up thick mucus and secretions from the airways of the lungs.

In general, air is conditioned by the nose during inhalation, which adds heat and humidity as it passes through the upper airway. However, if the upper airway is bypassed, this is when humidification therapy would be indicated.

Types of Humidifiers

There are a few different types of humidifiers used in respiratory care, including the following:

  1. Bubble humidifier
  2. Pass-over humidifier
  3. Vaporizer
  4. Heat and moister exchanger (HME)
  5. Heated humidifiers

Humidity therapy is also indicated for the treatment of bronchospasm, nonproductive cough, atelectasis, dyspnea, substernal pain, and airway dryness.

What is Bland Aerosol Therapy?

Bland aerosol therapy is the process of delivering liquid particles that are suspended in an inspired gas for therapeutic purposes. Some of the most common types of bland aerosols include:

  • Sterile water
  • Hypotonic saline
  • Isotonic saline
  • Hypertonic saline

This type of therapy can be administered with or without supplemental oxygen, depending on the patient’s oxygenation status.

Patient Bland Aerosol Therapy Nebulizer

Humidity and Bland Aerosol Therapy Practice Questions:

1. What are the types of humidifiers?
Bubble humidifier, passover humidifier, heat and moisture exchanger (HME), and room humidifier

2. What does humidity therapy involve?
It involves adding water vapor and sometimes heat to an inspired gas.

3. Heat and moisture exchange is a primary function of what?
It is a primary function of the upper respiratory tract, mainly the nose.

4. Which is more effective at providing heat and moisture, the mouth or nose?
The nose is more effective.

5. What is ISB?
It stands for isothermic saturation boundary and is the point that is normally 5 cm below the carina.

6. What happens above the ISB?
The temperature and humidity decrease during inhalation and increase during exhalation

7. What happens below the ISB?
The temperature and relative humidity remain constant (BTPS).

8. What is BTPS?
It stands for: body, temperature at the pressure to which the patient is exposed and 100% saturated with water vapor.

9. What is the primary goal of humidification?
To maintain normal physiologic conditions in the lower airways

10. What are the indications for humidification therapy?
Humidifying dry medical gases, flows greater than 4 lL/min, overcoming a humidity deficit
created when the upper airway is bypassed, managing hypothermia, and treating bronchospasm caused by cold air

11. What are the clinical signs and symptoms of inadequate airway humidification?
Atelectasis, dry or nonproductive cough, increased airway resistance, increased incidence of infection, increased work of breathing, patient complaint of substernal pain and airway dryness, and thick dehydrated secretions

12. What is absolute humidity?
The actual amount of moisture contained in a gas

13. What is relative humidity?
The amount of water vapor a sample could maximally hold at a given temperature

14. What is body humidity?
The amount of water vapor in a gas sample compared to the capacity for water vapor at body temperature.

15. What is the expected body humidity value at normal body temperature?
44 mg/L

16. What best describes a humidity deficit?
The amount of water vapor needed to achieve full saturation at body temperature

17. What is bland aerosol therapy used for?
It is used to treat upper airway inflammation from croup, epiglottitis, and post-extubation edema.

18. How does a heater improve the effectiveness of a humidifier?
Heat improves the water output of humidifiers.

19. When should heat be delivered with a large volume nebulizer?
It should be used if secretions are thick and hard to remove or if the patient’s upper airway is bypassed.

20. What are the four variables that affect the performance of a humidifier?
Temperature, surface area, time of contact, and thermal mass

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21. What are the low-flow humidifiers?
Bubble and jet humidifiers

22. What is a hazard of using a bubble humidifier?
At a high flow rate, it can produce aerosols which can transmit pathogenic bacteria from the humidifier reservoir to the patient.

23. When should a bubble humidifier be used?
When a patient is on a nasal cannula or simple mask with a flow greater than 4 L/min, or if the patient complains of a dry nose.

24. What problems could be wrong with a bubble humidifier if no sound is heard when pinching the tubing?
The inlet could be clogged, the reservoir could be cracked or loose, the gasket could be worn or missing, or the connection could be broken.

25. What is wrong if a bubble humidifier whistles by itself?
The oxygen flow may be too high, or the tubing may be kinked or obstructed.

26. What is wrong when no bubbling occurs in a bubble humidifier?
The capillary tube could be obstructed, there could be a loose connection, the oxygen flow may not be turned on, or there is inadequate pressure in the line.

27. What are the factors that influence the output of a bubble humidifier?
Temperature, relative humidity, and absolute humidity

28. What is the purpose of the pop-off valve on a bubble humidifier?
To warn of an obstruction and to prevent the bursting of the humidifier bottle

29. What is the expected water vapor output of a bubble humidifier?

30. What liter flows should be used with a bubble humidifier?
Flows of at least 2 L/min but not more 6 L/min

31. What type of probe does a servo-controlled heating system use at or near the patient’s airway?
Thermistor probe

32. What are the three most common problems with humidification systems?
(1) Dealing with condensation, (2) Avoiding cross-contamination, and (3) Ensuring proper conditioning of the inspired gas

33. What are some factors that would influence the amount of condensation in a humidified system?
(1) Temperature difference across the system, (2) Ambient temperature, (3) Gas flow, (4) Set airway temperature, and (5) The length, diameter, and thermal mass of the breathing circuit

34. What does particle size depend on?
It depends on the substance that is being nebulized, the methods used to generate the aerosol, and the environmental conditions.

35. How does an HME work?
It acts as an artificial nose and captures exhaled heat and moisture and uses it to heat and humidify the next inspiration.

36. What type of humidifier uses a filter?
Heat-moisture exchangers (HME)

37. When should an HME be used?
When the patient’s upper airway is bypassed during mechanical ventilation.

38. What is the correct placement of an HME?
It should be placed 10 cm away from the endotracheal tube and proximal to the ventilator circuit.

39. What are the three types of HMEs?
Simple (high thermal conductivity) condenser humidifier, hygroscopic (low thermal conductivity) condenser humidifier, and hydrophobic (water repellent element) condenser humidifier

40. What type of humidifier is known as an “artificial nose?”
Heat-moisture exchangers (HME)

41. What are the contraindications for using an HME?
Thick, copious, or bloody secretions; expired tidal volume less than 70% of the delivered tidal volume; body temperature less than 32 degrees C; high spontaneous minute volume greater than 10 L/min; and in patients who are receiving an in-line aerosol drug treatment

42. How can you tell if the HME is working properly?
If the patient is receiving proper heat and moisture

43. When should HME be changed to a large volume nebulizer with a heater?
When secretions can’t be broken up

44. Why is it a problem that large reservoir systems must be manually refilled?
This is problematic because, when the system is opened for refilling, cross-contamination can occur.

45. What is Bernoulli’s principle?
When gas in a tube exerts lateral wall pressure due to the gas velocity

46. What type of humidifier deals with Bernoulli’s principle?
Jet humidifiers

47. What is the purpose of a room humidifier?
To help with sinusitis and drainage.

48. How does a room humidifier work?
It creates an aerosol that exits the device and evaporates in the ambient air, increasing the humidity of the room.

49. What is a hazard of a room humidifier?
It has the potential to spread infections.

50. How does condensation occur?
Saturated gas cools as it leaves the point of humidification and passes through the delivery tubing to the patient. As the gas cools, its water vapor capacity decreases, causing condensation.

51. How is condensation disposed of?
It is treated as infectious waste and drained into an infectious waste container.

52. What is the formula for relative humidity?
%RH = content/capacity x 10

53. What is the capacity of water at body temperature?
44 mg/L

54. What is the formula for body humidity?
Absolute humidity / 44 mg/L x 100

55. What is a humidity deficit?
Inspired air that is not fully saturated at body temperature

56. What is the formula for humidity deficit?
44 mg/L – absolute humidity

57. What are the indications for humidification and warming of an inspired gas?
Dry gases that are at a flow greater than 4 L/min; following intubation; managing hypothermia; and treating bronchospasm caused by cold air.

58. What is a humidifier?
A device that adds molecular water to a gas, occurring by the evaporation of water from a surface

59. What are the factors that affect a humidifier’s function?
Temperature; the higher the temperature of a gas, the more water it can hold; surface area, time of contact, thermal mass; the greater the amount of water in the humidifier, the greater the thermal mass

60. What are the types of humidifiers?
Bubble, Passover, wick, HME, and cascade

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61. How much deadspace does an HME add?
30-90 mL

62. What are the types of heating elements that require an electrical source?
Hot plate, wraparound, yolk or collar element, immersion type, and a heated wire-ventilator circuit

63. What amount of humidity is used for intubated patients?
At least 30 mg/L

64. What piece of equipment is used to measure humidity?

65. How much can an unheated large volume nebulizer put out?
26-35 mg H2O/L

66. How much can a heated large volume nebulizer put out?
35-55 mg H2O/L

67. What is an ultrasonic nebulizer?
An electrically powered device that uses a piezoelectric crystal to generate aerosol. The crystal transducer converts radio waves into high-frequency mechanical vibrations that produce aerosols.

68. What does the amplitude do to the ultrasonic nebulizer?
It directly affects the volume of aerosol output. You cannot change the frequency, but you can increase the amplitude.

69. What are the types of aerosol masks?
Aerosol mask, trach collar, t-piece, face tent, mist hoods, and tents for small children and infants

70. What is the most effective humidifier/heater on the body?
The nose

71. What puts stress on the lower airway in order to provide heat and moisture?
An artificial airway

72. What is indicated following the intubation of a patient?
Humidification and warming of inspired gases

73. What is a device that adds molecular water to gas?

74. The higher the temperature of the gas in the humidifier?
The more water it can hold

75. What type of humidifier breaks an underwater gas stream into small bubbles?
Bubble humidifier

76. Are bubble humidifiers heated?

77. What is the goal of a bubble humidifier?
To raise the water vapor content of a gas to ambient levels

78. What type of humidifier directs gas over a water surface?
Passover (blow-by) humidifier

79. What type of humidifier is normally used for mechanical ventilation?
Reservoir humidifier

80. What type of humidifier does not have bubbles or aerosol and has a tube coming out of the top end?
Wick humidifier

81. What type of humidifier allows vapor to pass but not water?
Membrane humidifier

82. What kind of patients use a passover humidifier?
Patients on home CPAP units or those in the neonatal nursery

83. Do passover humidifiers have high efficiency and high exposure time?
No, they have low efficiency and low exposure time.

84. How often should an HME be changed?
Every 24 hours

85. What does heat improve in bubble and passover humidifiers?
Heat improves the water output (absolute humidity).

86. Heating systems are usually used on what type of patients?
They are used on patients with bypassed upper airways and those who are receiving mechanical ventilation.

87. What risk are patients exposed to when inhaling heated gases?
Airway burns

88. How much humidity is recommended for intubated patients?
30 mg/L

89. Inhaled gas is supposed to be maintained at what temperature?
35-37 degrees C

90. What can be used to minimize the risk of inhaling condensation?
Water traps or heated circuits

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91. What can cause bacterial colonization in the circuit?
The built-up of condensation

92. What are the most common devices used for bland aerosol therapy?
Large-volume jet nebulizers

93. How are large-volume jet nebulizers powered, and what are they connected to?
They are pneumatically powered and are connected directly to a flowmeter.

94. How does a large-volume jet nebulizer work?
Liquid particles are generated by passing gas at a high velocity through a small jet orifice

95. What is the optimal size for particles passing through a large-volume jet nebulizer?
2-5 micrometers

96. What device is electronically powered and uses a piezoelectric crystal to generate aerosol?
Ultrasonic nebulizer

97. Particle size is inversely proportional to what?
Signal frequency

98. Mist tents and hoods are normally used to deliver aerosol therapy to which type of patient?
Infants and children

99. What do high flows in mist tents help to do?
They help to “wash out” CO2 and reduce heat buildup.

100. What are six problems with bland aerosol therapy?
Cross-contamination and infection, environmental safety, inadequate mist production, over-hydration, bronchospasm, and noise

Final Thoughts

Humidity and bland aerosol therapy is an important treatment method for patients with specific signs and symptoms.

Hopefully, this article has given you a better understanding of this topic and how it can help those with pulmonary diseases. We have a similar guide on the topic of airway clearance therapy that I think would be helpful for you.

Thank you so much for reading, and, as always, breathe easy, my friend.

Written by:

John Landry, BS, RRT

John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.


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