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Principles of Humidification

As you have seen from the previous discussion, there are a number of reasons why humidity is an important aspect of the pulmonary system, including:

• It is needed to maintain normal bronchial hygiene
  
  
• It promotes functions of the normal mucociliary escalator
  
  
• It maintains the body's vital homeostasis
  
  
• Without humidity the cleansing activities of the cilia could not function properly, and the nearly 100 ml of mucus secreted daily would become quite thick and tenacious.
  
  
• Without humidity the actual lung parenchyma would dry up, causing a loss of normal compliance which would restrict lung movement and reduce ventilation.
  
  
• If normal use of the route of humidification and recapture of water were lost, problems would most certainly present themselves. If the upper airway were bypassed or dry gases were inhaled, a series of adverse reactions could occur, including:
  
  
• Impairment of ciliary activity
• Slowing of mucus movement
• Inflammatory changes and possible necrosis of pulmonary epithelium
• Retention of thick secretions and encrustation
• Bacterial infiltration of mucosa (bronchitis)
• Atelectasis
• Pneumonia

As a result of the importance of maintaining humidity, humidity and aerosol therapy are also important, and their general goals are to: Promote bronchial hygiene Loosen dried and/or thick secretions Promote a effective coughs to clear secretions Provide adequate humidity in the presence of an artificial airway Deliver adequate humidity when administering dry gases therapies Delivering prescribed medications

Clinical Evaluation of the Need for Humidity and/or Aerosol Use

There are a variety of factors to be considered when deciding to add humidity to dry gas therapies, including:

• patient's age and ability to move normal secretions
  
  
• neuromuscular status
  
  
• recent or planned surgeries
  
  
• trauma
  
  
• disease conditions

The presence of any of these may impair the patient's ability to cough and move secretions. Another problem may occur when patients develop very thick and abundant amounts of secretions which cannot be moved with normal muscle activity--making humidity or aerosol therapy necessary.

Indications for delivery of humidified gases and aerosols

Primary indications for humidifying inspired gases include:

• Administration of medical gases
  
  
• Delivery of gas to the bypassed upper airway
  
  
• Thick secretions in nonintubated patients

Additional indications for warming inspired gases:

• Hypothermia
  
  
• Reactive airway response to cold inspired gas

Primary indications for aerosol administration:

• Delivery of medication to the airway
  
  
• Sputum inductions