1. Aerosol Drug Therapy
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2. Learning Objectives Define the term “aerosol.”
Describe how particle size, motion, and airway characteristics affect aerosol deposition.
Describe how aerosols are generated.
List the hazards associated with aerosol drug therapy.
Describe how to select the best aerosol drug delivery system for a given patient.
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.

3. Introduction Aerosol is suspension of solid or liquid particles in gas
In clinical setting, medical aerosols are generated with devices that physically disperse matter into small particles & suspend them into gas
Atomizers
Nebulizers
Inhalers
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4. Introduction (cont.)
Medication aerosol provides higher therapeutic index
Higher local drug concentration in lung
Lower systemic effects
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5. Characteristics of Therapeutic Aerosols
Aerosol Output
Mass of fluid or drug contained in aerosol
Output rate is mass of aerosol generated per unit of time
Varies depending on different nebulizers & inhalers used
Emitted dose describes mass of drug leaving mouthpiece as aerosol
Measured by collecting aerosol that leaves nebulizer on filters
Gravimetric analysis measures aerosol weight
Assay measures quantity of drug
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.

6. Characteristics of Therapeutic Aerosols (cont.)
Particle size
Depends on 3 factors
Substance being nebulized
Method used
Environmental conditions
Methods to measure medical aerosol particle distribution include:
Cascade impaction
Laser diffraction
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.

7. Characteristics of Therapeutic Aerosols (cont.)
Particle size (cont.)
Geometric standard deviation (GSD) describes variability of particle sizes
Heterodisperse aerosols are aerosols with particles of different sizes
Monodisperse aerosols are aerosols with particles of similar sizes
Greater the GSD, wider range of particle sizes & more heterodisperse aerosols
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.

8. Characteristics of Therapeutic Aerosols (cont.)
Deposition
Only fraction of emitted aerosol (emitted dose) will be inhaled
Only fraction of inhaled (respirable dose) is deposited in lungs
Amount of drug inhaled called “inhaled mass.”
Portion of inhaled mass that can reach lower airways is “respirable mass”
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9. Characteristics of Therapeutic Aerosols (cont.)
Deposition (cont.)
Influenced by
Inspiratory flow rate
Flow pattern
Respiratory rate
Inhaled volume
I:E ratio
Breath-holding
Key mechanisms of aerosol deposition include:
Inertial impaction
Gravimetric sedimentation
Brownian diffusion
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.

10. Characteristics of Therapeutic Aerosols (cont.)
Deposition (cont.)
Inertial impaction
Occurs when aerosol in motion collides with & are deposited on surface
Primary deposition mechanism for larger particles
(>5 µm).
Greater mass & velocity of moving object, then greater inertia & greater tendency of that object to continue moving along its set path
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.

11. Characteristics of Therapeutic Aerosols (cont.)
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.

12. Characteristics of Therapeutic Aerosols (cont.)
Deposition (cont.)
Sedimentation
Occurs when aerosol particles settle out of suspension & are deposited due to gravity
Represents primary mechanism for deposition of small particles (1-5 µm)
Breath-holding after inhalation of aerosol increases sedimentation & distribution across lungs
Greater mass of particle, the faster it settles
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.

13. Characteristics of Therapeutic Aerosols (cont.)
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.

14. Characteristics of Therapeutic Aerosols (cont.)
Deposition (cont.)
Brownian diffusion
Primary deposition mechanism for very small particles (<3 µm) deep within lung
Particles between 1 & 0.5 µm have very low mass & are so stable that most remain in suspension & are exhaled back into environment
Particles <0.5 µm have greater retention rate in lungs
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.

15. Characteristics of Therapeutic Aerosols (cont.)
Aging
Process by which aerosol suspension changes over time
How aerosol ages depends on:
Composition of aerosol
Initial size of its particles
Particle size can change due to evaporation or hygroscopic water absorption
Time in suspension
Ambient condition
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.

16. Hazards of Aerosol Therapy
Primary hazard of aerosol drug therapy is adverse reaction to medication
Other possible hazards:
Infection
Airway reactivity
Pulmonary & systemic effects of bland aerosols
Drug concentration changes during nebulization
Eye irritation
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.

17. Aerosol Drug Delivery Systems MDI
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18. Aerosol Drug Delivery Systems (cont.)
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.

19. Aerosol Drug Delivery Systems (cont.) Pneumatic (jet) nebulizers
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20. Aerosol Drug Delivery Systems (cont.) Small volume nebulizers (SVN)
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.

21. Aerosol Drug Delivery Systems (cont.) Large-volume jet nebulizers
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.

22. Aerosol Drug Delivery Systems (cont.) Ultrsasonic nebulizer
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23. Aerosol Drug Delivery Systems (cont.) Vibrating mesh (VM) nebulizers
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24. THANK YOU
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