3a. Aerosol Flashcards
What is an aerosol?
Suspension of solid of liquid particles in gas
What is Aerosol Therapy?
Delivery of aerosol particles to the respiratory tract
What are the 3 main uses for aerosol therapy?
- Humidification of Dry inspired gases by using bland aerosols
- Airway Clearance and mobilization of respiratory secretions using bland aerosols
- Delivery of aerosolized drugs to respiratory tract
What’s a Bland Aerosol? and give 3 examples
Liquid particles suspended in an inspired gas
Ex) Sterile Water, Hypotonic/Isotonic/Hypertonic Saline
What are the 3 factors particle size depend on?
- Substance being nebulized
- Method of Use
- Environmental Conditions
What does GSD stand for and what does it mean?
Geometric Standard Deviation
Describes the variability of particle sizes in an aerosol distribution
What’s the difference between Heterodisperse and Monodispersed aerosols?
Heterodispersed : Particles with different sizes
Monodispersed: Particles with similar sizes
What is the relationship between GSD and the range of particle sizes?
The greater the GSD is, the more wider range of particles sizes ➔ heterodispersed
What is used to measure particle size distributions?
Cascade impaction (more common) and Laser Scattering
How does Cascade Impaction work?
Cascade Impactor collects aerosols of different size ranges on a series of stages or plates.
Collects large particles and whatever that’s not impacted move to next stage with smaller orifices until it is collected on a final filter with vacuum pump on the end.
How does Laser Scattering/Diffraction work?
Determines the relationship between the intensity & angle of light scattered from a particle, then calculates the particle size based on the Mie-scattering theory
What is particle aging?
When aerosol suspension is changing over time
What are the 4 factors that depend on particle aging?
Composition, Initial Size, Time in suspension, Ambient Condition
How can Aerosol Particles change?
Particle can change as a result of either evaporation or hygroscopic water absorption
What is the relationship with the rate of particle size change and the size of particle?
They are inversely proportional
Small particles grow/shrink faster than large particles
Large particles grow/shrink slower than small particles
What is Deposition?
A process where aerosol particles leave suspension in gas, they deposit on (attach to) a surface
What’s the major factor that influences Deposition?
Particle Size
What’s the particle size range that delivers to the Upper Airways (Nose, larynx, trachea)
5 - >50 um
What’s the particle size range that delivers to the Lower Generation?
2-5 um
What’s the particle size range that delivers to the Parenchyma: Alveolar Region
1-3 um Parenchyma: Alveolar Region
<0.1 in parenchyma
What is Inhaled Mass?
Amount of emitted aerosol/dose is inhaled
What is Respirable Mass
Amount of inhaled/respirable dose is deposited in lungs that can reach lower airways
What are 3 Key Mechanisms/Motions of Deposition?
Inertial Impaction, Gravimetric Sedimentation, and Brownian Diffusion
What is Inertial Impaction? and What particle size
Where aerosol in motion collides with and are deposited on surface
Large Particles >5um
Inertial Impaction: What’s the theory?
The greater the mass and velocity of a moving droplet, the greater the inertia and tendency of that droplet to continue moving along its set path.
What will increase aerosol deposition by inertial impaction?
Variable or irregular passages and turbulent gas flow.
What is Gravimetric Sedimentation? and What particle size?
When aerosol particles settle out of suspension and are deposited due to the pull of gravity.
Small Particles: 1-5 um
Gravimetric Sedimentation: What’s the theory (2)?
Breath-holding after inhalation increases sedimentation and distribution in the lungs.
The greater the mass of a particle, the faster it settles.
What is Brownian Diffusion? and what particle size?
Primary mechanism for deposition of small particles, mainly in the respiratory region where bulk gas flow ceases and most aerosol particles reach the alveoli by diffusion
Very Small Particles: <3um
Brownian Diffusion: What’s the theory for smaller particles (2)?
Particles 1 to 0.5 μm: so stable, most remain in suspension and are cleared with the exhaled gas
Particles < 0.5 μm: have a greater retention rate in the lungs
What are therapeutic aerosol depositions influenced by? (6)
Inspiratory Flow Rate, Flow Pattern, RR, Inhaled Volume, I:E Ratio, and Breath Holding
What are the hazards to Aerosol Therapy? (7)
Primary: Adverse reaction to the drug
Others: Infection, Risk of inducing Bronchospasm, Systemic effects of Bland Aerosols (Overhydration), Drug Reconcentration, Eye irritation
Tubing condensation draining into the airway.
Why is particle size important for aerosol delivery?
Particle size will tell us how it enters the airways (mechanism) and where it will deposit in the body or lungs.
What is the primary method of deposition of large, high mass particles?
Inertial impaction
What do you to prevent bronchospasm when you nebulize reactive substances?
Administer a bronchodilator prior to given agents that cause spasms
Gravimetric Sedimentation:
How long is an ideal breath hold maneuver?
How much will you increase drug deposition?
What about drug distribution?
Ideal breath hold maneuver: 10 seconds
How much you might increase drug deposition: 10%
Drug Distribution: Increase ratio of aerosol deposited in the lung parenchyma to the central airways
What are the 6 aerosolized substances that are associated with increased airway resistance?
Acetylcysteine, Antibiotics, Steroids, Cromolyn Sodium, Ribavirin, and Distilled Water
3 CDC recommendations to prevent nosocomial infection
Sterilized between patients, Replace frequently with disinfected or sterile units, or rinse with sterile water and air dry every 24 hours
How will eye irritation occur?
Aerosol administration with face mask may deposit drug in eyes. Anticholinergic medications suspected to worsen preexisting eye conditions
Advantages of Aerosol Medication Delivery (7)
◦ *Provides high therapeutic index
◦ Aerosol Doses are smaller than doses for systemic treatment
◦ Rapid onset of drug action
◦ Local drug delivery to the respiratory system
◦ *Fewer or less severe systemic side effects
◦ Painless and Convenient
◦ Lung provides portal to the body for inhaled aerosol agents intended for systemic effect
Disadvantages of Aerosol Medication Delivery (5)
◦ Numerous variables affecting drug delivery
◦ Inconsistent dose estimation and dose reproducibility
◦ Coordination of hand action and breathing with MDIs
◦ Many nurses, physicians, and therapists lack knowledge of device use and protocols
◦ Numerous device types are confusing to patients and practitioners
How would you do a Patient Assessment? (5)
Basic Assessment: HR, RR, BS, BP
Correct use of devices (technique)
Drug Effectiveness: Reversibility, Peak Flow, Spirometry
Subjective Response (Patient’s POV)
ABG and/or SpO2 in acute situations as needed
How would you do Patient Assessment for Long Acting agents? (6)
‣ PFTs for long term monitoring
‣ Ongoing lung function
‣ Amount of B-Agonist Use
‣ Degree of nocturnal symptoms
‣ Number of exacerbations requiring physician consult
‣ Degree of lifestyle change due to symptoms
