Aerosol Therapy Flashcards
What is the 3 ways that medical aerosol can be delivered
Atomizer, Nebulizers, and Inhalers
What is the three purposes of medical aerosol
Deliver bland water solutions to the respiratory tract in order to humidify inspired gases
Administer drugs (bronchodilators, anti-inflammatories and antibiotics) to the lungs, throat, or nose
Improved mobilization and clearance of respiratory secretions
What is an aerosol?
A suspension of solid or liquid particles in a gas.
Aerosol Therapy Compared with Other Forms of Administration
Administration of drugs by aerosol offers higher local drug concentrations in the lung with lower systemic levels compared with other forms of administration.
Improved therapeutic action with fewer systemic side effects provides a higher therapeutic index.
What is the main use of Aerosol Therapy
Deliver aerosolized drugs to respiratory tract
What is Aerosol Output
Weight or mass of aerosol particles produced by aerosol generator (usually per minute)
What is Aerosol Output in a Nebulizer
Mass of aerosol that is generated in a unit of time
What is Aerosol Output in a Drug Delivery System
Emitted dose describes the mass of a drug leaving the mouthpiece of a nebulizer or inhaler as an inhaler
What are the Methods to Measure Aerosol Output
Aerosol output can be measure via collect the aerosol leaving the nebulizer on filters or measuring the weight (gravimetric analysis) or quantity of a drug (assay)
Gravimetric Analysis
A gravimetric measurement is easier to do but less reliable compared to assay as weight will change with water evaporation while drug mass will not
Drug Assay
A drug assay is more reliable measurement of aerosol output and is the quantiy of a drug
What is the fundamental principle of aerosol deposition?
Only a fraction of the emitted aerosol will be inhaled and only a fraction of what is inhaled will make it to the lungs.
What is Deposition?
• Disposition is when an aerosol leaves its suspension in a gas it will deposit onto a surface
Inhaled Mass Vs. Emitted Dose
The inhaled mass is the amount of drug that is inhaled
Only a portion of a generated aerosol (emitted dose) from a nebulizer will be inhaled
Respirable Mass
The proportion of the drug mass in particles that are small enough (fine-particle fraction) to reach the lower respiratory tract is the respirable mass.
There will be a small percentage of a drug that will be exhaled
What are the determinants of deposition?
Particle size, inspiratory flow rate, flow pattern, respiratory rate, inhaled volume, ratio of inspiration time to expiratory time, and breath holding.
How is Aerosol Output measured?
By collecting the aerosol that leaves a nebulizer and collects on special filters.
What are heterodispersed aerosols?
They are aerosols with particles of different sizes.
What are key mechanisms of aerosol deposition?
Inertial impaction, Gravimetric sedimentation, and Brownian diffusion.
What are two methods to measure medical aerosol particle distribution?
(1) Cascade impaction, and (2) Laser diffraction
What does gravimetric analysis measure?
Aerosol weight.
What is an aerosol emitted dose?
The mass (amount) of the drug leaving the mouthpiece as an aerosol.
What is aerosol output rate?
The mass (amount) of aerosol generated per unit of time. It varies depending on different nebulizers and inhalers used.
What are the two most common laboratory methods used to measure medical aerosol particle size distribution?
Cascade impaction and laser diffraction.
What is aerosol output?
The mass of fluid or drug contained in the aerosol product by a nebulizer. It is the mass of aerosol generated per unit of time.
What is an Emitted Dose?
The mass of drug leaving the mouthpiece of a nebulizer or inhaler as an aerosol.
Where aerosol particles are deposited in the respiratory tract depends on what?
It depends on their size, shape, and motion and on the physical characteristics of the airways. Key mechanisms causing aerosol deposition include inertial impaction, sedimentation, and Brownian diffusion.
Why is particle size so important in aerosol therapy?
The ability of aerosols to travel through the air, enter the airways, and deposit in the lung is largely based on particle size.
Which of the following best defines an aerosol?
A suspension of liquid or solid particles in a gas.
The mass of aerosol particles produced by a nebulizer in a given unit time best describes which quality of the aerosol?
Output
Which of the following describes the mass of drug leaving the mouthpiece of a nebulizer as aerosol?
Emitted Dose.
What is the retention of aerosol particles resulting from contact with respiratory tract mucosa called?
Deposition.
What measure is used to identify the particle diameter, which corresponds to the most typical settling behavior of an aerosol?
Mean mass aerodynamic diameter (MMAD).
What is inertial impaction?
When aerosol in motion collides with and are deposited onto a surface. 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.
Aerosols occur in nature as what?
Pollens, Spores, Dust, Smoke, Fog, and Mist.
The aim of medical aerosol therapy is to?
To deliver a therapeutic dose of the selected agent (drug) to the desired site of action.
What is turbulent flow?
Turbulent flow is a function of the ability of the patient to inhale the powder with a sufficiently high inspiratory flow rate.
What is the respirable mass?
It is the proportion of aerosolized drug of the proper particle size to reach the lower respiratory tract.
Inertial Impactation is the primary mechanism of deposition for what type of particles
This is the primary mechanism for particles larger than 5 μm
Occurs in the first 10 generations
Inertial Impaction is a function of what
Inertial impaction is a function of particle size (mass) and velocity
There is a direct relationship with mass and velocity
Inertial Impaction and Mass and Velocity
The greater the mass and velocity of a particle the greater its inertia and tendency to move in a set path
When a large particle is moving with a gas stream and the stream changes direction the particle tends to remain on the same path and collide with the airway surface
A smaller particle on the other hand will tend to change direction along with the gas stream
Inertial Impaction and Flow
Higher the flow of a gas stream the greater the tendency for particle to impact and be deposited in the airways
Quicker particles can’t change direct easily.
Turbulent flow, obstructed airways, and inspiratory flow greater than 30 L/min will increase inertial impaction
Turbulent flow and convoluted passageways in the nose cause most particles larger than 10 μm to impact and become deposited.
Inertial Impaction and Airway Protection
Inertial impaction will filter out particles in order to help protect the lower airway from particulates such as dust and pollen
Particles 6 to 10 μm tend to become deposited in the oropharynx and hypopharynx especially due to the turbulent air flow as it passes around the tongue and into the larynx
What does the aerosol particle size depend on?
It depends on the substance being nebulized, the method used to generate the aerosol, and the environmental conditions surrounding the particle
What are monodispersed aerosols?
Aerosols with particles of similar sizes.
What are therapeutic aerosol depositions influenced by?
The inspiratory flow rate, the flow pattern, respiratory Rate, inhaled volume, the I:E ratio, and breath-holding.
What is gravimetric sedimentation?
When aerosol particles settle out of suspension and are deposited due to the pull of gravity. Breath-holding after inhalation increases sedimentation and distribution in the lungs. The greater the mass of a particle, the faster it settles.
What are cascade impactors?
They are designed to collect aerosols of different size ranges on a series of stages or plates.
What is sedimentation?
It occurs when aerosol particles settle out of suspension and are deposited owing to gravity. The greater mass of the particle, the faster it settles.
Which of the following is a common method to measure aerosol particle size?
Cascade Impaction.
What is the primary mechanism for deposition of large, high mass particles (greater than 5 um) in the respiratory tract?
Inertial Impaction.
What will increase aerosol deposition by inertial impaction?
Variable or irregular passages and turbulent gas flow.
sedimentation is a function of what
Size and time
sedimentation and Velocities
There is increased settling for larger particles with slower velocities
With normal breathing sedimentation is the primary mechanism of deposition for what
particles 1 to 5 μm and will occurs mostly in the central airways
Sedimentation and Time
• As sedimentation with time, an end- inspiratory breath hold maximizes sedimentation
o e.g. a 10 sec breath-hold can aerosol deposition by ~ 10% and increase the ratio of aerosol deposited in lung parenchyma to central airway by fourfold.
How are medical aerosols generated in the clinical setting?
They are generated with devices that physically disperse matter into small particles and suspend them in gas.
What is Brownian diffusion?
The primary deposition mechanism for very SMALL particles and will deposit DEEP within the lungs.
Breath holding after inhalation of an aerosol does what?
It increases the residence time for the particles in the lung and enhances distribution across the lungs and sedimentation.
What is Brownian Diffusion?
Brownian Diffusion is the primary mechanism for deposition of small particles (<3 μm) and will occur mainly in the region of the lung where bulk gas flow ceases and particles can reach the alveoli (particle inertia is low)
Small Particle Collisions
Small, low mass aerosol particles are easily bounced around by collisions with carrier gas molecules which will result in the deposition to surrounding surfaces
Particles 1 to 0.5 um
Particles 1 to 0.5 μm are stable and will remain in suspension and are cleared with the exhaled gas, whereas particles < 0.5 μm have greater retention rate in the lungs.
Particle Aging
Aging: Process by which an aerosol suspension changes over time.
Particles constantly growing, shrinking, coalescing or falling out of suspension
Aging of an aerosol depends on:
o Ambient conditions
o Composition of aerosol
o Initial size of particles
o Time in suspension
Aerosol Particle will change in size based on
hygroscopic tendancy or evaporation
Rate of particel growth
inversly porportional to size
Smaller particles grow faster than larger particles
Small water based particles can also shrink when exposed to relatively dry gas
Aerosols are generated in relatively dry ambient conditions and then taken into airway where both temperature and humidity increase
Optimal Pattern of Inhalation
Optimal pattern of inhalation varies with type of aerosol generating device
Aerosol Deposition and Airway Obstruction
The presence of airway obstruction is one of the greatest factors influencing aerosol deposition.
Total pulmonary deposition is greater in smokers and patients with obstructive airway disease than in healthy persons
When flow rate is constant deposition is influenced by
When inspiratory flow rates are constant, the deposition fraction of monodisperse aerosols increases with increased VT, length of inspiration, and particle size
Scintigraphy
Apporach to quantify aerosol deposition where a drug is tagged with a radioactive substance and then a scanner will be used to measure distribution
What is the Primary Hazard of Aerosol Therapy
Adverse reaction to a drug
Other Hazards of Aerosol Therapy
Infection Airway reactivity Systemic effects of bland aerosol Drug concentration Eye Irritation Secondhand Exposure
Aerosol Therapy and Airway Reactivity
Cold air and high-density aerosols can cause reactive bronchospasm and increased airway resistance, especially in patients with pre-existing respiratory disease
What Medication are At Risk for resulting in airway reactivity
acetylcysteine, antibiotics, steroids, ribavirin, and distilled water
How to help with airway recativity
Administration of bronchodilators before or with administration of these agents may reduce the risk or duration of increased airway resistance.
What May Increase the Solute concentration
During nebulization, the evaporation, heating, baffling, and recycling of drug solutions undergoing jet or ultrasonic nebulization increase solute concentrations.
This increase in concentration usually is time-dependent; the greatest effect occurs when nebulization of medications occurs over extended periods, as in continuous aerosol drug delivery.
Aerosol and Eye Irritation
Aerosol administration via a face mask may deposit drug in the eyes and cause eye irritation.
In very rare cases, anticholinergic medications have been suspected to worsen pre-existing eye conditions, such as forms of glaucoma.
Aerosol Therapy and Second-Hand Exposure
Repeated second-hand exposure to bronchodilators is associated with increased risk of occupational asthma.
Unless filters are placed in the expiratory limb, 40% of aerosols produced during mechanical ventilation are exhausted to the air of the intensive care unit
What Factors Effect the Efficiacy of Aerosol Generated by a Nebulizer
Residual "Dead" Volume Ideal Filling Volume Tx Time Gas Source Flow Rate Gas Density
Residual ‘Dead’ Volume
- Jet nebulizers do not aerosolize below minimum volume called ‘dead’ volume
- Dead volume is amount of drug solution remaining in reservoir when device begins to ‘sputter’ and aerosolization ceases
- ~ 0.5 to 1.0 ml but varies with different devices (always read the device manufacturers specifications)
Ideal Filling Volume
At any given flow rate, Increase volume will increase time of effective nebulization
A volume between 3- 5 ml (or as per manufacturers recommendation) of solution is recommended
Treatment Time
incresed volume will decrease concentration of drug in residual volume and increase the drug dose to a patient
increase volumes lenthen treatment time
Effect Of Gas Source And Flow Rate
Increased flow rate or gas pressure will decrease particle size and shift MMAD lower
Increased flow rate or gas pressure will increase output and shorten treatment time
Adequate flow rate for SVN
6-8 LPM
Gas Density
Affect aerosol production and depsoition
decreased density (ex. heliox) will decrease aerosol impaction resulting in better deposition in the lungs
When Heliox is used output is < than with air or O2 requiring increase in flow to produce comparable weight of aerosol per min
Even though HEliox will incresae the amount of aerosol in lungs it will require high . flows
Type of Solution
Viscosity and density of medication effects its output and particle size
Solutions that Tends to Need Modifications
Pentamidine
Antibiotics that have different characteristics and viscosity
Gentamicin requires 10- 12 lpm to produce adequately small aerosol particles
Advantages of Aerosolized Medications
Rapid onset Smaller dose Less systemic side effects Painless Convenient
How does a large volume ultrasonic nebulizer work?
It incorporates air blowers to carry mist to the patient for delivery of bland aerosol therapy or sputum induction.
How do ultrasonic nebulizers work?
They use a piezoelectric crystal to produce aerosols. The crystal converts electrical energy into high frequency vibrations which will form oscillation waves and form droplets with break free as fine aerosol particles. Output is directly affected by amplitude setting.
How do you prime an MDI?
Shake the device and release one or more sprays into the air when the MDI is new or hasn’t been used in a while.
How are DPIs categorized?
They are categorized by the design of their dose containers.
How often do you assess a patient on continuous nebulization?
Assess them every 30 minutes for the first 2 hours then hourly after that for adverse drug responses.
What affects MDI performance and drug delivery?
Low temperature decreases the output of the CFC MDI’s. Debris build up on nozzle or actuator orifice reduces the emitted dose.
What are beneficial characteristics of using an MDI?
They are portable, compact, short tx time, and easy to use.
Things that will affect lung deposition
Substance being nebulized
Method of generating the aerosol
Breathing pattern
Inspiratory flow rate
What are small volume ultrasonic nebulizers used for?
The delivery of aerosolized medications (i.e. bronchodilators, antibiotics and anti-inflammatory agents).
What are sub-hazards to aerosol drug therapy?
Infection, airway reactivity, pulmonary and systemic effects of bland aerosols, drug concentration changes during nebulization, and eye irritation.
What contributes to aging of aerosols?
The composition of aerosol, the initial size of particles, the time in suspension, and the ambient condition.
What happens to the temperature of a solution placed in an ultrasonic nebulizer?
The temperature of the solution increases.
What is a dry powder inhaler (DPI)?
It is a breath-actuated dosing system by which a patient creates the aerosol by drawing air through a dose of finely milled drug powder. The dispersion of powder into respirable particles depends on creation of turbulent flow in inhaler.
The two most common laboratory methods used to measure medical aerosol particle size distribution
cascade impaction and laser diffraction.
Cascade impactors
designed to collect aerosols of different size ranges on a series of stages or plates.
The mass of aerosol deposited on each plate is quantified by drug assay, and a distribution of drug mass across particle sizes is calculated.
laser diffraction
a computer is used to estimate the range and frequency of droplet volumes crossing the laser beam.
expression of average particle size
Because medical aerosols contain particles of many different sizes (heterodisperse), the average particle size is expressed with a measure of central tendency, such as mass median aerodynamic diameter (MMAD) for cascade impaction or volume median diameter (VMD) for laser diffraction.
o These measurement techniques of the same aerosol may report different sizes, so it is important to know which measurement is used.
o The MMAD and VMD both describe the particle diameter in micrometers (μm).
what are the two common ways to quantify particles
o The average particle size which is expressed n terms of central tendency
Mass Median Particle Size (MMAD)
o Variability of particle size in an aerosol
Geometric Standard Deviation (GSD)
Mass Median Aerodynamic Diameter (MMAD)
• Mass median aerodynamic diameter (MMAD) is the size where 50% of the mass of particles will be above this size and 50% will be below this size
• MMAD is important to determine which nebulizer to use to deliver medication to a target area
o If you want deposition into small airways you need to use a nebulizer with a lower MMAD
Geometric Standard Deviation (GSD) “The Spread”
• The geometric standard deviation (GSD) describes the variability of particle sizes in an aerosol distribution set at 1 standard deviation above or below the median (15.8% and 84.13%).
• The greater the GSD, the wider the range of particle sizes produced by a device.
• GSD < 1.22, aerosol considered monodispersed = single particle size
o Nebulizers that produce monodisperse aerosols are used mainly in laboratory research and in nonmedical industries
• GSD > 1.22, aerosol considered heterodispersed = range of particle sizes
• Most aerosols used in respiratory care
• Particles > 10 microns
o Tx nasopharyngeal or oropharyngeal regions e.g. nasal spray for rhinitis
• Particles 5- 10 microns
o Deposition to more central airways with significant deposition in oropharyngeal region
Deposits into the large airways, first 6 generations
• Particles 2- 5 microns
o Deposition in LRT (last 6 generations)
o More adrenergic receptors in bronchioles (compared to rest of airway) thus increased response with bronchodilators
• Particles 0.8- 3 microns
increased delivery of aerosol to lung parenchyma (alveoli)
o Used for anti-infective drugs such as pentamidine where intra-alveolar deposition needed with minimum deposition in airways due to irritation
what is a nebulizer
• Nebulizers generate aerosols from solutions and suspensions.
3 categories of nebulizers
(1) pneumatic jet nebulizers,
(2) USNs,
(3) vibrating mesh (VM) nebulizers.
Nebulizers described in terms of their reservoir size.
o Small volume nebulizers (SVNs) most commonly used for medical aerosol therapy hold 5 to 20 ml of medication.
o Large volume nebulizers, also known as jet nebulizers, hold up to 200 ml and may be used for either bland aerosol therapy or continuous drug administration.
Small Volume Nebulizer
Either pneumatic (gas powered) that utilize a jet-shearing principle for creation of an aerosol
Four categories of jet SVNs include
Continuous nebulizer with simple reservoir
Continuous nebulizer with collection reservoir bag,
Breath-enhanced nebulizer
Breath- actuated nebulizer
most commonly used SVN
• The most commonly used SVN is the constant output design.
o Aerosol is generated continuously, with 30% to 60% of the nominal dose being trapped as residual volume in the nebulizer, and more than 60% of the emitted dose is wasted to the atmosphere.
o Continuous nebulization wastes medication because the aerosol is produced throughout the respiratory cycle and is largely lost to the atmosphere
o Patients with an I:E ratio of40:60 (or1:1.5) lose 60% of the aerosol generated to the atmosphere.
o If 50% of the total dose is emitted from the nebulizer, and 50% of that aerosol is in the respiratory range and 40% of that is inhaled by the patient, less than 10% deposition is commonly measured in adults receiving continuous nebulizer therapy.
How can aerosolized medication be conserved with a sVN
• Aerosolized medication can also be conserved with reservoirs.39
o A reservoir on the expiratory limb of the nebulizer conserves drug aerosol.
• Factors affecting SVN efficiency are:
o Dead Volume – minimum volume required in the reservoir to aerosolize the drug – 0.5 to 1.0 ml - only 35% to 60% of a drug solution is delivered from a SVN before sputter
o Filling Volume and Treatment Time – ideal is 3 to 5 ml at 6 to 8 LPM flow-rate for a treatment time of 10 minutes
Advantages Of SVN
• Less technique and device dependent
o Minimal coordination
• Effective with low inspiratory flows and volumes which improve deposition
• Useful in very young, very old, pts in severe distress, debilitated patients
• No breath hold is required, although it can’t hurt
• Patients in severe distress may have high inspiratory flows…we like the fact we can use a “hands free mask” & just continuously administer medication, eventually some medication reaches our intended target site
Disadvantages Of SVN
• Tx times can get lengthy • Contamination • Wet cold spray with mask delivery • External power source o Electrical power or compressed gas
Uses of a SVN
• Emergency:
o Unable to follow instructions / disoriented
o Tachypneic (> 25 bpm) / unstable respiratory pattern
o Poor inspiratory capacity
o Incapable of breath hold
• Patient preference/home use
• Formulation of drug
Small Volume Nebulizer With a Reservoir
- Many types of disposable SVNs are packaged with a 6-inch (15-cm) piece of aerosol tubing to be used as a reservoir
- This may increase inhaled dose by 5% to 10% or increase the inhaled dose from 10% to approximately 11% with the reservoir tube.
Continuous Small Volume Nebulizer With Collection Bag
- Bag reservoirs hold the aerosol generated during exhalation and allow the small particles to remain in suspension for inhalation with the next breath, while larger particles rain out.
- These additions have been attributed with a 30% to 50% increase in inhaled dose.
- A collection bag is attached on the expiratory side of the nebulizer “T,” which collects aerosol leaving the SVN when the patient is not actively inhaling.
- Some of the aerosol in the bag is inhaled with the next inspiration, increasing total dose efficiency.
Breath Enhanced Nebulizers
• Breath-enhanced nebulizers generate aerosol continuously, using a system of vents and one-way valves to minimize aerosol waste.
an inspiratory vent allows the patient to draw in air through the nebulization chamber generating and containing aerosolized drug.
• On exhalation, the inlet vent closes, and aerosol exits by a one-way valve near the mouth- piece; this process can increase inhaled mass by 50% over standard continuous nebulizers and reduces aerosol waste to the atmosphere.
nebulizer with constant output
• When there is a constant output the drug will be delivered continuously through inspiration and expiration, this means that when expiration is long than inspiration there will be significant losses in the drug amount
Dosimetric output
• With Dosimetric output the drug will only be delivered during inhalation
o Used in PFT laboratories
o Sense inspiration and pulse airflow to the jet orifice and transform a conventional nebulizer into a breath actuated system
Sputtering
- It can be difficult to determine when a nebulizer treatment is complete.
- Aerosol delivery from a jet nebulizer ceased after the onset of inconsistent nebulization (sputtering)
- Aerosol output declined by one-half within 20 seconds of the onset of sputtering.
- The concentration of albuterol in the nebulizer cup increased significantly when the aerosol output declined, and further weight loss in the nebulizer was caused primarily by evaporation. Most consider aerosolization past the point of initial nebulizer sputter ineffective.
SVN Technique
• Use of an SVN is less technique-dependent and device-dependent than use of a pMDI or DPI delivery system.
• Slow inspiratory flow optimizes SVN aerosol deposition. However, deep breathing and breath holding during SVN therapy do little to enhance deposition over normal tidal breathing
• Because the nose is an efficient filter of particles larger than 5 μm, many clinicians prefer not to use a mask for SVN therapy.
o As long as the patient is mouth breathing, there is little difference in clinical response between therapy given by mouthpiece and therapy given by mask.
Optimal Technique for Using a SVN
• Assess patient for clinical need
• Select mask or mouthpiece
• Use a conserving system
o Thumb port
o Breath actuator
o Reservoir
• Place drug in nebulizer and saline if needed
• Set gas flow to 6 to 10 L/min
• Coach patient to breath slowly through mouth at normal Vt
• Continue treatment until nebulizer sputters
• Rinse neb with sterile water
• Monitor patient between treatments for adverse effects
• Assess outcome
Infection Control Issues
- The CDC recommends that nebulizers be cleaned and disinfected, rinsed with sterile water, or air dried between uses.
- Jet SVNs have reservoirs that are open to and positioned below the mouthpiece or mask. This allows secretions from the patient to enter the medication cup, contaminating medication.
- Multidose drug containers have been associated with contamination.
- After 7 days of nebulizer use five of six multidose containers of medication solutions were found to be contaminated.
- Refrigerating solutions and discarding syringes every 24 hours eliminated bacterial contamination.
- Use of single dose ampoules have not been associated with contamination of medications. In addition, some recommend one nebulizer for one treatment.
- The Cystic Fibrosis Foundation recommends that standard small volume nebulizers should be discarded after each treatment to prevent infection in cyctic fibrosis patients.
ultrasonic NEbulizer Output
• High output with small particles sizes and high aerosol densities
• Output is determined by the amplitude setting (some- times user-selected).
o The greater the signal amplitude, the greater the nebulizer output.
ultrasonic Nebulizers and PArticle Size
• Particle size is inversely proportional to the frequency of vibrations.
• Frequency is device- specific and is not user-adjustable.
o For example, the DeVilbiss (Somerset, PA) Portasonic nebulizer operating at a frequency of 2.25 MHz produces particles with an MMAD of 2.5 μm, whereas the DeVilbiss Pulmosonic nebulizer operating at 1.25 MHz produces particles in the 4- to 6-μm range
• Particle size and aerosol density also depend on the source and flow of gas conducting the aerosol to the patient.
Ultrasonic Nebulizer and Ventilators
Can be placed in line with a ventilator
In contrast to SVNs, USNs do not add extra gas flow to the ventilator circuit during use. This feature reduces the need to change and reset ventilator and alarm settings during aerosol administration
Advantages Of USN
- Small size
- Rapid nebulization with shorter Tx time
- Smaller filling volume
- Portability (batteries)
Disadvantages Of USN
- Expensive
- Fragility – lack of durability
- Infection control
Large Volume Ultrasonic Nebulizers
- Large volume USNs (used mainly for bland aerosol therapy or sputum induction) incorporate air blowers to carry the mist to the patient
- Low flow through the USN is associated with higher mist density.
- In contrast to jet nebulizers, the temperature of the solution placed in a USN increases during use.
- As the temperature increases, the drug concentration increases, and proteins can be denatured.
Small Volume ULtrasonic Nebs Vs LArge VOLUme
• In contrast to the larger units, some of these systems do not use a couplant compartment; the medication is placed directly into the manifold on top of the transducer.
o The transducer is connected by a cable to a power source, often battery- powered to increase portability.
• These devices have no blower; the patient’s inspiratory flow draws the aerosol from the nebulizer into the lung.
