Chapter 40- Aerosol Drug Therapy Flashcards
what is aersol?
a suspension of solid or liquid particles in gas
when do you use aerosol?
in clinical settings, medical aerosols are generated with atomizers, nebulizers, and inhalers
what is an atomizer
converts liquid into droplet
what is a nebulizer
the produce finer aerosol particles from liquid-based formulations over greater periods of time using compressed gas or electricity
describe an inhalers purpose
they generate aerosolized medication from liquids or dry powders for a single inhalation
what is the goal of aerosol therapy
deliver a therapeutic dose of the selected agent to the desired site of action
what are some benefits of medicated aerosol
medication aerosol provides higher therapeutic index
- higher local drug concentration in lung
- lower systemic affects
What is the aerosol output?
mass of fluid or drug
-produced by aerosol generator per actuation or unit of time
what is the determination of aerosol output?
output rate is mass of aerosol generated per unit of time
-varies depending on different nebulizers and inhalers used
how is aerosol output measured?
measured by collecting aerosol that leaves nebulizer on filters
- gravimetric analysis measures aerosol weight
- assay measures quantity of drug
what is the emitted dose?
the emitted dose describes mass of drug leaving mouthpiece
what is an important take away on aerosol output?
large amounts of particles that leave the nebulizer may never reach the lungs
Particle size:
depends on what 3 factors
- substance being nebulized
- method used to generate the aerosol
- environmental conditions
what methods are used to measure medical aerosol particle distribution?
Cascade impaction:
-MMAD-mass median aerodynamic diameter
Laser diffraction:
-VMD- volume median diameter
what are two similar between cascade and laser aerosol particle distribution
- both laser and casacade are:
- -laboratory performed tests
- measured in microns
What is medication deposition
medication deposition occurs when particles leave suspension in gas and deposit on a surface
what is an inhaled dose
small fraction of the aerosol generated and emitted from a nebulizer will be inhaled, this is known as inhaled dose
what is respirable dose
respirable dose is the fraction deposited in the lungs
what is respirable mass
respirable mass is the small amount of drug that make it to the lower respiratory tract
what % of inhaled aerosol particles will be exhaled
1-5%
what is the deposition influenced by?
- inspiratory flow rate
- flow pattern
- respiratory rate
- inhaled volume
- I:E ration
- breath holding
what are 3 key mechanism of aerosol deposition
- inertial impaction
- sedimentation
- diffusion
what is inertial impaction
occurs when an aerosol in motion collides with a surface. this is the primary deposition mechanism for larger particles
where does inertial impaction deposit
deposit primarily in nose, mouth, and pharynx
what is the particle size for inertial impaction?
particles >10
what is sedimentation deposition
occurs when aerosol particles settle out of suspension and are deposited do to gravity.
Breath holding after inhalation of an aerosol will enhance distribution across the lungs
where does sedimentation deposition deposit
deposit primarily in proximal airways (those closest to the top of the tree, such as the bronchi)
where size are sedimentation deposition
particles 1-5 microns
what is diffusion deposition
the primary deposition mechanism for small particles deep within the lung
what size particles are diffusion deposition
very small particles have very low mass and often remain in suspension and are exhaled back into the environment
where does diffusion deposition occur
deposit primarily in the peripheral airways
describe the process of inertial impaction deposition (what happens to the particles)
inertial impaction of large particles:
the masses of which tend to maintain their motion in straight lines. As airway directions changes, the large particles are deposited on nearby walls. Smaller particles are carried around corners by the airstream and fall out less readily
Putting all together:
Why is all this important?
- different medications are to be delivered to different areas and we need different nebulizers to accomplish our goal
- nebulizers are not a one size fits all
what is aerosol aging?
process by which aerosol suspension changes over time
how is aerosol aging dependent on
- composition of aerosol
- initial size of its particles
- particles size can change due to evaporation or hygroscopic water absorption
- time in suspension
- ambient condition
what is scintigraphy
a drug is “tagged” with a radioactive substance, aerosolized, and inhaled
how is scintigraphy measured
a scanner measure the distribution and intensity of radiation across the device and the patients head and thorax
how is scintigraphy information used for
this information is used to calculate the percentage of drug retained by the device and delivered to various areas in the patient