Humidity and aerosol therapy_1_

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					Humidity and aerosol therapy Objectives
• • • Describe indications and goals for aerosol therapy Discuss the operating principles of aerosol generators Calculate any total flow unknown

Humidity Concepts
• Humidity: Molecular water in gas
– Primary function of the upper airway heat, humidify, and filter. – Body Temperature and Pressure Saturated (BTPS)

• Aerosol: Particles of liquid or solid in a carrier gas. • 3 factors influence the amount of H2O in vapor
– Temperature – Surface area – Time of contact

Humidity Concepts
• At a particular temperature there is a maximum amount of water a gas can hold. • Absolute humidity: the actual weight of water contained in a given volume of gas (content). • Relative humidity is defined as a relationship between the actual weight or pressure (Content) of water in air at a specific temperature and the maximum weight or pressure (capacity) expressed as a percentage
– RH =Content/capacity*100

Humidity Concepts
• Body Humidity: The relative humidity as compared to BTPS • Humidity Deficit: The difference between Capacity at BTPS and actual content
– EX. Room air at 20C when it is 100% saturated holds 17mg/l What is the humidity deficit from air at BTPS? – Air at 37C holds 44 mg/l – 44-17=27 mg/l

Indications for humidification
• Anhydrous medical gasses • Upper airway bypassed

– Minimize Humidity deficit created

• Thick inspissated secretions • Hypothermia • Treating cold induced bronchospasm

Effects of dry air
• • • • Decreased ciliary motility Irritated airways Mucus production increases Pulmonary secretions become thick and inspissated

Types of humidifiers
• Bubble humidifier • Pass over humidifier • Heat and moisture exchanger (HME)

Bubble Humidifier
• • • • • • • • • Simple capillary tube design Gas is directed down tube and through a diffuser Bubbles pass through H2O and obtain a slightly higher AH Low flow device

Pass over humidifier
High flow Gas passes over heated water Works by evaporation Low efficiency Wick humidifier uses a porous element adds surface element and increases efficiency

Heat Moisture Exchanger
• Artificial nose • Heat and moisture are stored on exhalation and passed back to the patient on inspiration • May be contraindicated in some patients

Aerosol generators
• Atomizers or Nebulizers that physically disperse matter into small particles suspended in a gas
– Bland aerosol to enhance secretion removal or as an adjunct for upper airway swelling

– Respiratory drugs have a strong therapeutic action when delivered to the respiratory tract

Hazards of therapy
• Side effects of medication • Over hydration • Infection
– Pseudomonas aerunginosa – Legionella pneumophila

• Bronchospasm

Mechanics of deposition
• Inertial impaction
– Increased with particle size and speed
• Take a slow deep inspiration

• Gravitational settling
– Particle size and time – Happens at the end of the breath hold

• Diffusion
– Through airway wall – Smaller particles diffuse faster

• Humidity!!!

Principals related to aerosol administration
• Aerosol
– Particles small enough for pulmonary applications (1-10 microns)

• Stability
– The tendency of aerosol particles to remain in suspension

• Penetration
– Depth which particles reach

• Deposition
– Process of particles depositing out of suspension to remain in the lung

The role of particle size
• Range of particle sizes among different devices.
– 5-20 microns Upper airway nose larynx and trachea – Lower airways 2-5 microns – 1-3 microns to the respiratory zone

• Specific areas can be targeted with particle size.

Large volume jet nebulizer
• Air entrainment • Uses the jet shearing principal

• Able to nebulize large volumes of water to the respiratory tract • Gas injection type of nebulizer • Flow limitations

Aerosol generators
• Ultrasonic neb
– Electric powered piezoelectric driven high output
• New small sizes for home use and vent use

– Frequency determines the particle size

Small volume nebulizer (SVN)
• • • • What are they? Advantages and disadvantages Factors to consider with the use of SVNs The latest and greatest

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