Aerosol
A suspension of a solid or liquid particles in gas
Aerosols occur in nature as:
-pollens
-Spores
-Dust
-Smoke
-Fog
-Mist
Medical Aerosols are generated with
-atomizers
-nebulizers
-inhalers
(all are items that disperse matter into small particles & suspend them into a gas)
The aim of medical aerosol therapy is to:
Deliver a therapeutic dose of the selected agent (drug) to the desired site of action.
Key characteristics of aerosols
-aerosol output
-particle size
-desposition
-aging
Aerosol Output
-the mass of fluid or drug contained in aerosol product by a nebulizer.
-the mass of aerosol generated per unit of time
Emitted Dose
The mass of drug leaving the mouthpiece of a nebulizer or inhaler as aerosol
Aerosol particle size depends on:
-the substance for nebulization
- method used to generate the aerosol
-The environmental conditions surrounding the particle
The only reliable way to determine the characteristics of an aerosol suspension is:
Laboratory measurement
2 most common laboratory methods used to measure medical aerosol particle size distribution are:
-cascade impaction
- laser diffraction
Cascade impactors
are designed to collect aerosols of different sizes ranges on a series of stages ot plates
Laser Diffraction
A computer is used to estimate the range and frequency of droplet volumes crossing the laser beam.
Mass Median Aerodynamic Diameter
(MMAD)
measure of central tendency that describes the particle diameter in micrometers in medical aerosols and pertains to cascade impaction.
Volume Mean Diameter
(VMD)
the median diameter of an aerosol particle measured in units of volume.
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% & 84.13)
The Greater the GSD
the wider the range of particle sizes, and the more heterodisperse the aerosol
Monodisperse
Aerosols consisting of particles of similar size (GSD less than or equal to 1.2)
Inhaled Mass
- AKA inhaled dose
- the amount of drug inhaled
Fine-Particle Fraction
...
Respirable Mass
proportion of aerosolized drug of the proper particle size to reach the lower respiratory tract
Whether aerosol particles that are inhaled into the lungs are deposited into the respiratory tract depends on:
-size
-shape
-motion
of the particled and on the physical characteristics of the airways and breathing pattern.
Deposition
estimony of a witness taken on interrogatories, either oral or in writing.
Key Mechanisms of aerosol desposition include:
-inertial impaction
-gavimetric sedimentation
-Brownian Diffusion
Inertial Impaction
occurs when suspended particles in motion collide with and are deposited on a surface
-this is the primary deposition mechanism for particles larger than 5um
Sedimentation
Occurs when aerosol particles settle out of suspension & are deposited owing to gravity.
-The greater mass of the particle the faster it settles.
Breath holding after inhalation of an aerosol increases.....
The residence time for the particles in the lung and enhances distribution across the lungs and sedimentaiton
Brownian Diffusion
The primary mechanism for desposition of small particles (< 3um), mainly in the respiratory region where bulk gas flow ceases
Large Paticles
- are more susceptible to the force of gravity than smaller particles.
-are more affected by the bombardment of molecules deposited by diffusion.
Depth & Penetration & desposition of a particle in the respiratory tract vary...
with size and tidal volume.
- with this knowledge it may be possible to target aerosol deposition to specific areas of the lunh by using the proper particle size and breathing pattern.
Range of particle size for common aerosols in the environment and the influence of inertial impactions, sedimentation, and diffusion.
The site of deposition in the respiratory tract varies with the size of the particle. Use of nebulizers that produce particles in a specific size range improves the targeting of aerosols for deposition to a desired site in the respiratory tract, as follow
Aging
-The process by which an aerosol suspension changes over time.
How aerosol ages depends on:
-composition of the aerosol
-initial size of its particles
-time in suspension
-the ambient conditions to which it is exposed.
Aersol particle can change size as a result of
-evaporation
or
-hygroscopic water absorption.
Determinant of Desposition (where a particle of any specific size is deposited)
-particle size
-inspiratory flow rate
-flow pattern
-respiratory rate
-inhaled volume
-ratio of inspiraton time to expiratory time.
-breath holding.
precise amount of drug delivered to the patient's airways can be measured in terms of:
-patient's clinical response to aerosol drug therapy including the desired therapeutic effects and any unwanted adverse effects.
Scintigraphy
photograph showing the distribution and intensity of radioactivity in various tissues and organs after administration of a radiopharmaceutical.
Hazards of aerosol drug therapy
-(PRIMARY HAZARD) adverse reaction to the medication being adminitered.
-infection
-airway reactivity
-systemic effects of bland aerosols
-drug concentration
-eye irritation.
Risk for Caregivers and Bystanders
risk the above hazards as a result of exposure to secondhand aerosol drugs.
Infections from aerosol generators
-nosicomial infections occur by spreading bacteria by the airborne route.
The most common sources of bacteria are
-patient secretions
-contaminated solutions
-caregiver's hands.
procedures to help reduce contamination and infection associated with respiratory care equipment
-nebulizers should be sterilized between patients
-nebulizers should frequently be replaced with disinfected or sterile units or rinsed with sterile water (not tap water) and ait dried every 24 hours.
Cold air and high-density aerosols can cause:
Reactive bronchospasm and increased airway resistance.
Monitoring for reactive bronchospasm should include:
-peak flow measuremenrs or percentage forced expiratory volume in 1 second before and after therapy.
-auscultation for for adventitious breath sounds
-observation of the patient's breathing pattern and overall appearance.
- most essential: communicating w
Pulmonary and Systemic Effects
Excess water can cause:
overhydration
oulmonary and systemic effects
excess saline solution can cause
hypernatremia
Preliminary assessment should balance
the need versus the risk of aerosol therapy
appropriate airway clearance techniques should accompany
any aerosol therapy designed to help mobilize secretions.
Drug Concentration: what increases solute concentrations during nebulization
eveporation
heating
baffling
recycling of drug solutions
Continuous Drug Delivery
when nebulization occurs over extended periods
this is the greatest effect.
Eye irritation is caused by:
aerosol asministered via face mask which causes the drug to be deposited in the eyes.
Workplace exposure to aerosol may be detectable in
-the plasma of bystanders & health care providers.
Implementation of an occupational health and safety policy could include:
-using systems that introduce less aerosol to the atmosphere
-dry powder inhalers
- filtering exhalation to contain aerosol
-using environmental controls.
Aerosol generators include
-pMDIs (w/ or w/o spacers & holding chambers)
-DPIs
- Small and Large Volume (jet) nebulizers
- Hand-Bulb atomizers
-Ultrasonic Nebulizers
-Vibrating Mesh Nebulizers
Most commonly prescribed method of aerosol delivery in the US
pMDI
pMDI
-used to administer bronchodilators, anticholinergics, & steroids
- Are easy to use but commonly misused.
Propellant
something that propels or provides thrust, as the propellant in a metered dose inhaler
pMDI is
- a pressurized canister that contains the prescribed drug in a volatile propellant combined with a surfactant and dispersing agent.
How pMDI works
When the canister is inverted (nozzle down) and placed in its actuator, or "boot," the volatile suspension fills a metering chamber that controls the amount of drug delivered. Pressing down on the canister aligns a hole in the metering valve with the mete
The output volume of pMDIs range
from 30-100mcl
Chlorofluorocarbons (CFCs)
gaseous chemical compounds that were originally used to power metered dose inmhalers but currently phased out of use
Components of pMDI, including function of the metering valve
...
hydrofluoroalkane (HFA)
the current gaseous chemical compound used to power metered dose inhalers.
Before initial use and after storage, every pMDI should be
-primed by shaking and actuating the device to atmosphere one to four times.
-without the priming, the initial dose actuated from a new pMDI cansiter contains less active substance than subsequent acutations.
- waste a single does when it has not been use
Breath-Actuated Pressurized Metered Dose Inhaler
-variation of a pMDI
-incorporates a trigger that is activated during inhalation.
-This trigger reduces the need for the patient or caregiver to coordinate MDI acutation with inhalaiton.
Aerocount Autohaler
-flow triggered pMDI
designed to eliminate the need for hand-breath coordination by automatically triggering in response to the patient's inspiratory effort.24 To use the Autohaler, the patient cocks a lever on the top of the unit, which sets in motion a
Dose Counters
- a serious limitation of pMDIs is the lack of a "counter" to indicate the number of doses remaining in the canister.
Tail-off effect
refers to variability in the amount of drug dispensed toward the end of the life of the canister.
without a dose counter
there is no viable method to determine remaining drug in a pMDI other manually keeping a log of every dose taken.
Factors Affecting Pressurized Metered Dose Inhaler Performance & Drug Delivery
-Temperature
- Nozzle Size and Cleanliness
- Priming
- Timing od Actuation Intervals
temperature
Decreased temperature (<10� C) has been shown to decrease the output of CFC pMDIs.
Nozzle Size and Cleanliness
-as debris builds up on the nozzle or actuator orifice, the emitted dose is reduced.
Priming
-Shaking the device and releasing one or more sprays into the air when the pMDI is new or has not been used for a while.
-done to mix the drug and the propellant
-required to provide an adequate dose.
Timing of Actuation Intervals
-Manufacturers recommended 30 sec to 1 min between actuations.
-Very rapid acutation of multiple puffs per breath reduces inhaled drug per puff
Optimal Technique for use of MDI steps 1-5
1.Warm the pMDI canister to hand or body temperature, and shake it vigorously.
2.Before first use of a new pMDI and when the pMDI has not been used for several days, prime the pMDI by pointing it into the air (away from people) and actuating.
3.Assemble t
Optimal Technique for use of MDI steps 6-11
6.Breathe out normally.
7.As you slowly begin to breathe in (<0.5 L/sec), actuate the pMDI.
8.Continue inspiration to total lung capacity.
9.Hold your breath for up to 10 seconds. Then relax and breathe normally.
10.Wait 1 minute between puffs.
11.Disasse
Through preliminary patient instuction
-can last 10-30 min
-should include:
- demonstration
- Practice
- Confirmation of patient performance
Cold Freon Effect
-occurs when the cold aerosol plume reaches the back of the mouth and the pati ent stops inhaling.
-can be reduced by using a spacer or holding chamber.
with ipatropium use
the closed-mouth technique to avoiid spraying in the eyes.
To avoid opportunistic oral yeast infection:
rinse the mouth after steriod use.
pMDI steroid aerosol impaction occurs deep in the hypopharynx, which cannot be easily rinsed with gargling for this reason...
steroid pMDIs should not be used alone but always in combination with a spacer or valved holding chamber.
Spacers and Valved holding Chambers
-are pMDI accessory devices designed to reduce both oropharyngeal deposition and the need for hand-breath coordination.
-all spacers add distance between the pMDI and the mouth, reducing the initial forward velocity of the pMDI droplets.
-reduces foul tas
Determine Dose Left in Pressurized MDI with dose counters
The user should29:
1.Determine how many puffs of drug the pMDI has when full.
2.Learn to read the counter display because each dose counter has a different way of displaying doses left in the canister.
3.Check the counter display to track the pMDI actuati
Determine Dose Left in Pressurized MDI without dose counters
The user should29:
1.Read the label to determine how many puffs of drug the pMDI has when full.
2.Calculate how long the pMDI will last by dividing the total number of puffs in the pMDI by the total puffs used per day. If the pMDI is used more often than
Valved holding chambers
- protect the patient from poor hand-breath coordination, with exhaled gas venting to the atmosphere, allowing aerosol to remain in the chamber available to be inhaled with the next breath.
-allow infants, small children, and adults who cannot control the
Basic Concepts for spacer devices include:
1. Small volume adapters
2. Open Tube Designs
3. Bag reservoirs
4. Valved holding chambers.
Spacer
-A spacer is a simple valveless extension device that adds distance between the pMDI outlet and the patient's mouth.
-This distance allows the aerosol plume to expand and the propellants to evaporate before the medication reaches the oropharynx.
Holding Chambers
- allow the aerosol plume to develop and reduce oropharyngeal deposition. A holding chamber also incorporates one or more valves that prevent aerosol in the chamber from being cleared on exhalation.
- provide less oropharyngeal deposition, higher respirab
Holding Chambers vs Spacers
holding chambers produce a finer, slower moving, more "respirable" aerosol with less impaction of drug in the oropharyngeal area (1% of dose) than simple spacers
Optimal Technique for Use of Metered Dose Inhaler With A Valved Holding Chamber
1.Warm the pMDI to hand or body temperature.
2.Assemble the apparatus, ensuring there are no objects or coins in the chamber that could be aspirated or obstruct outflow.
3.Hold the canister vertically, and shake it vigorously. Prime if necessary.
4.Place
Holding chambers with masks are available for use in the care of infants, children, and adults.
- allow effective administration of aerosol from a pMDI to patients who are unable to use a mouthpiece device (because of their size, age, coordination, or mentation).
- Holding chambers are helpful in administration of pMDI steroids because deposition of
Cleaning of holding chambers and spacers
should be cleaned regularly, typically monthly, as recommended by the manufacturer. Use of dilute liquid dishwashing soap, with or without rinsing, and allowing to air dry are recommended.
Dry Powder Inhaler (DPI)
- typically a breath-actuated dosing system.
- patient creates the aerosol by drawing air though a dose of finely milled drug powder with sufficient force to disperse and suspend the powder in the air.
- dispersion of the powder into respirable particles
3 Categories of DPIs
1. Unit-Dose DPI
2. Multiple unit-dose DPI
3. Multiple Dose Drug Reservoir DPI
Unit-Dose DPIs
dispense individual doses of drug from punctured gelatin capsules.
Multiple Unit-Dose DPIs
contain a case of four or eight individual blister packets of medication on a disk inserted into the inhaler.
Optimal performance for each DPI occurs at
- a specific inspiratory flow rate.
- The fine-particle fraction of respirable drug from existing DPIs ranges from 10% to 60% of the nominal dose.
- The higher the resistance or the greater the flow requirement of a DPI device, the more difficult it is fo
In a humid Environment the emitted dose
decreases
If inhalation is not performed at the optimal inspiratory flow rate for a particular device,
delivery to the lung decreases as the dose of drug dispensed decreases and the particle size of the powder aerosol increases
Passive, or patient-driven, DPIs rely on
the patient's inspiratory effort to dispense the dose.
The most critical factor in using a passive DPI is the need for high inspiratory flow.
- Patients must generate an inspiratory flow rate of at least 40 to 60 L/min to produce a respirable powder aerosol.
DPIs SHOULD NOT BE USED FOR
the management of acute bronchospasm.
exhalation into the device before inspiration can result in
- loss of drug delivery to the lung
Optimal Technique for Use of a Dry Powder Inhaler
1.Assemble the apparatus.
2.Load dose, keeping device upright.
3.Exhale slowly to functional residual capacity.
4.Seal lips around the mouthpiece.
5.Inhale deeply and forcefully (>60 L/min). A breath hold should be encouraged but is not essential.
6.Repea
Nebulizers
generate aerosols from solutions and suspensions.
three categories of nebulizers include
(1) pneumatic jet nebulizers,
(2) USNs, and
(3) VM nebulizers.
Small volume nebulizers (SVNs)
most commonly used for medical aerosol therapy hold 5 to 20 ml of medication.
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.
Most modern jet nebulizers are powered by
-high-pressure air or oxygen (O2) provided by a portable compressor
-compressed gas cylinder,
- 50-psi wall outlet.
a typical SVN is powered by
a high-pressure stream of gas directed through a restricted orifice (the jet). The gas stream leaving the jet passes by the opening of a capillary tube immersed in solution. Because it produces low lateral pressure at the outlet, the high jet velocity dra
Determining Doses Left in the Dry Powder Inhaler
...
Factors Affecting Performance of SVN
-Nebulizer Design
-Gas Source: Wall, Cylinder, Compressor
- Characteristics of Drug Formulation
Nebulizer Design
�Baffles
�Fill volume
�Residual drug volume
�Nebulizer position
�Continuous vs. intermittent nebulization
�Reservoirs and extensions
�Vents, valves, and gas entrainment
�Tolerances in manufacturing within lots
Gas Source: Wall, Cylinder, Compressor
�Pressure
�Flow through nebulizer
�Gas density
�Humidity
�Temperature
Characteristics of Drug Fomulation
�Viscosity
�Surface tension
�Homogeneity
Baffle
is a surface on which large particles impact and fall out of suspension, whereas smaller particles remain in suspension, reducing the size of particles remaining in the aerosol.
well-designed baffling systems decrease both
the MMAD (size) and the GSD (range of sizes) of the generated aerosol.
Residual Drug Volume
-or dead volume, is the medication that remains in the SVN after the device stops generating aerosol and "runs dry."37
-The residual volume of a 3-ml dose can range from 0.5 to more than 2.2 ml, which can be more than two-thirds of the total dose.
-Residu
Droplet size and nebulization time are inversely proportional to gas flow through the jet.
higher the flow of gas to the nebulizer, the smaller the particle size generated, and the shorter is the time required for nebulization of the full dose.
Gas pressure and flow through the nebulizer affect particle size distribution and output.
-the higher the pressure or flow, the smaller the particle size, the greater the output, and the shorter the treatment time.
-Too low a gas pressure or flow can result in negligible nebulizer output.
Concerns in the use of disposable nebulizers with compressors at home involve
possible degradation of performance of the plastic device over multiple uses
Failure to clean the nebulizer properly resulted in
degradation of performance because of clogging of the Venturi orifice, reducing the output flow, and buildup of electrostatic charge in the device.
Gas density affects both aerosol generation and delivery to the lungs.
-The lower the density of a carrier gas, the less turbulent the flow (i.e., the lower the Reynolds number), resulting in less aerosol impaction.
-The lower the density of a carrier gas, the less aerosol impaction occurs as gas passes through the airways,
Humidity and temperature can affect particle size and the concentration of drug remaining in the nebulizer.
-evaporation of water and adiabatic expansion of gas can reduce the temperature of the aerosol to 10� C less than ambient temperature.
-This cooling may increase solution viscosity and reduce the nebulizer output, while decreasing particle MMAD.40
-Aeroso
Four categories of jet SVNs include
(1) continuous nebulizer with simple reservoir, (2) continuous nebulizer with collection reservoir bag,
(3) breath-enhanced nebulizer, and
(4) breath-actuated nebulizer
Most Commonly Used SVN
Constant output design
In neonates and infants,
given the small minute volumes and small airways with increased impaction and reduced sedimentation, deposition can be only 0.5%.
A reservoir on the expiratory limb of the nebulizer
conserves drug aerosol
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 Colume Nebulizers with Collection Bags
- 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, attributed to a 30% to 50% increase in inhaled dose
Breath-Enhanced Nebulizers
-nebulizers that entrain room air in direct relationship to the inspiratory flow of the patient
-generate aerosol continuously, using a system of vents and one-way valves to minimize aerosol waste
Breath-Actuated Nebulizers
-aerosol device that is responsive to the patient's inspiratory effort and reduces or eliminates aerosol generation during exhalation
-generate aerosol only during inspiration.
-eliminates waste of aerosol during exhalation and increases the delivered dos
AeroEclipse
-A unique, spring-loaded, one-way valve design draws the jet to the capillary tube during inspiration and causes nebulization to cease when the patient's inspiratory flow decreases below the threshold or the patient exhales into the device.
-Expiratory pr
Technique for using a SVN
-Slow inspiratory flow optimizes SVN aerosol deposition.
-deep breathing and breath holding during SVN therapy do little to enhance deposition over normal tidal breathing.
-As long as the patient is mouth breathing, there is little difference in clinical
The CDC recommends that nebulizers
be cleaned and disinfected, or rinsed with sterile water, and air dried between uses.
Large volume jet nebulizers
- used to deliver aerosolized drugs to the lung.
- particularly useful when traditional dosing strategies are ineffective in the management of severe bronchospasm.
A potential problem with continuous bronchodilator therapy (CBT)
is increase in drug concentration. Patients receiving CBT need close monitoring for signs of drug toxicity (e.g., tachycardia and tremor).
Another special-purpose large volume nebulizer
-a small particle aerosol generator (SPAG)
- The SPAG was manufactured by ICN Pharmaceuticals specifically for administration of ribavirin (Virazole) to infants with respiratory syncytial virus infection.
-incorporates a drying chamber with its own flow c
SPAG
duces medical gas source from the normal 50 pounds per square inch gauge (psig) line pressure to 26 psig with an adjustable regulator. The regulator is connected to two flowmeters that separately control flow to the nebulizer and drying chamber. The nebul
Optimal Technique for Using a SVN 1-5
1.Assess the patient for need (clinical signs and symptoms, breath sounds, peak flow, %FEV1)
2.Select mask or mouthpiece delivery (nose clips may be needed with mouthpiece).
3.Use conserving system (thumb port, breath actuator or reservoir) if indicated.
Optimal Technique for Using a SVN 6-10
6.Coach patient to breathe slowly through the mouth at normal VT.
7.Continue treatment until nebulizer begins to sputter.
8.Rinse the nebulizer with sterile water and air dry, or discard, between treatments.
9.Monitor patient for adverse response.
10.Asse
Two specific problems are associated with SPAG use to deliver ribavirin.
1. Caregiver exposure to the drug aerosol.
2.Drug precipitation can jam breathing valves or occlude the ventilator circuit.
The Problem of Drug precipitation can jam breathing valves or occlude the ventilator circuit cn be overcome by:
(1) placing a one-way valve between the SPAG and the circuit and
(2) filtering out the excess aerosol particles before they reach the exhalation valve, changing filters frequently to avoid increasing expiratory resistance.
Guidelines for Use of Aerosol Devices in the Care of Infants and Children
Device
Age Group
SVN
Neonate to all ages
Valved chamber with mask
Neonate/infant/toddler
Valved chamber with mouthpiece
>3 years
pMDI alone
>4 years
Breath-actuated Neb
>4 years
DPI
?4 years
Spontaneous breathing in all patients, including pediatric and neonatal patients, results in
greater deposition of aerosol from an SVN than occurs with positive pressure breaths (e.g., intermittent positive pressure ventilation). This mode of ventilation reduces aerosol deposition more than 30% compared with the effect of spontaneously inhaled ae
Regardless of the device used, the clinician must be aware of
the limitations of aerosol drug therapy. First, depending on the device and patient, 10% or less of drug emitted from an aerosol device may be deposited in the lungs (Figure 36-30). As indicated in Box 36-7, additional reductions in lung deposition can oc
Clinical efficacy varies according to
both patient technique and device design. For these reasons, the best approach to aerosol drug therapy is to use an assessment-based protocol that emphasizes individually tailored therapy modified according to patient response.
Factors Associated With Reduced Aerosol Drug Deposition in the Lung
Mechanical ventilation
� Artificial airways
� Reduced airway caliber (e.g., infants and children)
� Severe airway obstruction
� High gas flows
� Low minute volumes
� Poor patient compliance or technique
� Limitation of specific delivery device
Careful, ongoing patient assessment is
is key to an effective bronchodilator therapy protocol. To guide practitioners in implementing effective bedside assessment, the AARC has published Clinical Practice Guideline: Assessing Response to Bronchodilator Therapy at Point of Care.
conventional spirometry
remains the standard for determining bronchodilator response.
the AARC recommends that when monitoring trends,
the same unit be used for a given patient and that the patient's range be reestablished if a different flowmeter is used
Sole dependence on tests of expiratory airflow for assessing patient response to therapy is
unwise because not all patients can perform these maneuvers. Other components of patient assessment useful in evaluating bronchodilator therapy include patient interviewing and observation, measurement of vital signs, auscultation, blood gas analysis, and
Restlessness, diaphoresis, and tachycardia also may indicate
severity of airway obstruction but must not be confused with bronchodilator overdose
In terms of breath sounds, a decrease in wheezing accompanied by an overall decrease in the intensity of breath sounds indicates
worsening airway obstruction or patient fatigue. Improvement is indicated when wheezing decreases and the overall intensity of breath sounds increases.
All patients with acute airway obstruction should be monitored for oxygenation status with
pulse oximetry. This value can be used in conjunction with observational assessment to titrate the level of inspired O2 given to the patient (see Chapter 35). Arterial blood gases are not essential for determining patient response to bronchodilator therap
Poor patient response to bronchodilator therapy often occurs because
an inadequate amount of drug reaches the airway. To determine the "best" dose for patients with moderate obstruction, the respiratory therapist (RT) should conduct a dose-response titration.
A simple albuterol dose-response titration involves
giving an initial 4 puffs (90 mcg/puff) at 1-minute intervals through a pMDI with a holding chamber. After 5 minutes, if airway obstruction is not relieved, the RT gives 1 puff per minute until symptoms are relieved, heart rate increases to more than 20 b
Frequency of Assessment of Bronchodilator Therapy
For Patient with an Acute Disorder Who is in Unstable Condition
� Whenever possible, perform a full assessment and obtain a pretreatment baseline.
� Assess and document all appropriate variables before and after each treatment (breath sounds, vital signs, side effects during therapy, and PEFR or FEV1).
� The frequency
Frequency of Assessment of Bronchodilator Therapy
For Stable Patient
� In the hospital, PEFR should be measured initially before and after each bronchodilator administration. Thereafter, twice-daily determinations may be adequate.
� In the home, PEFR ideally should be measured three or four times a day: on rising, at noon,
Practitioner demonstration followed by repeated patient return demonstration is a
must and should be done frequently, such as with each office or clinic visit.
Every drug approved for inhalation to date has been designed for and tested in
populations of ambulatory patients with moderate disease. As patients with lung disease become acutely and critically ill, the approved label doses, frequency of administration, and devices may not be practical or effective, especially for treatment of pa
Another type of off-label use involves drugs that
have not been approved for inhalation, ranging from heparin to certain antibiotics. Although physicians may order such drugs via inhalation, the risk to the patient and institution is greater when the administration of such drugs via inhalation has not be
Patients in the emergency department with severe exacerbation of asthma or acute bronchospasm often have been taking standard doses of their bronchodilators for
24 to 36 hours before admission without response. Giving nebulizer treatments with standard bronchodilator doses and repeating the treatments until the symptoms are relieved can require hours of staff time. Administering higher doses of albuterol in short
Pediatric Asthma Score
SCORE
Indicator
0
1
2
PaO2
>70 mm Hg (air)
<70 mm Hg (air)
<70 mm Hg (40% O2)
SpO2
>94% (air)
<94% (air)
<94% (40% O2)
Cyanosis
No
Yes
Yes
Breath sounds
Equal
Unequal
Absent
Wheezing
None
Moderate
Marked
Accessory muscle use
None
Moderate
Marked
Level of
After CBT is started, the patient is carefully assessed every
30 minutes for the first 2 hours and thereafter every hour. A positive response is indicated by an increase in PEFR of at least 10% after the first hour of therapy. The goal is at least 50% of the predicted value. For small children, improved oxygenation
Four primary forms of aerosol generator are used to deliver aerosols during mechanical ventilation
SVN, USN, VM nebulizer, and pMDI with third-party adapter
Factors Affecting Aerosol Drug Delivery During Mechanical Ventilation
Category
Factor
Ventilator-related
Mode of ventilation
VT
Respiratory rate
Duty cycle
Inspiratory waveform
Breath-triggering mechanism
Circuit-related
Size of endotracheal tube
Type of humidifier
Relative humidity
Density and viscosity of inhaled gas
Devi
Additional techniques can be used for mechanically ventilated patients because
(1) a change in the differences between peak and plateau pressures (the most reliable indicator of a change in airway resistance during continuous mechanical ventilation) can be measured, (2) automatic positive end expiratory pressure levels may decrease
Optimal Technique for Aerosolized Drug Delivery to Mechanically Ventilated Patients
1 Review order, identify the patient, gather equipment, and assess the need for bronchodilators.
2 Clear the airways as needed, by suctioning the patient as needed.
3 If using a circuit with heat and moisture exchanger (HME), remove HME from between the a
Aerosol administration by a VM nebulizer has been estimated to deliver greater than
10% deposition in adults and infants without the addition of gas into the ventilator circuit. The low residual drug volume and small particle size are associated with higher efficiency. Similar to the USN, the VM nebulizer does not add gas flow into the v
Direct pMDI actuation by simple elbow adapters typically results in the least
pulmonary deposition, with most of the aerosol impacting in either the ventilator circuit or the tracheal airway. Higher aerosol delivery percentages occur only when an actuator or spacer is placed in-line in the ventilator circuit. These spacers allow an
With continuous or bias flow through the ventilator circuit, the delivery is reduced
as flow increases, whereas placement of a VM nebulizer near the ventilator increases delivery
Noninvasive ventilation may be administered with
standard and bilevel ventilators. Bilevel ventilators often use a flow turbine, with a fixed valve or leak in the circuit that permits excess flow to vent to atmosphere. Placement of the aerosol generator between the leak and the patient's airway seems to
Intrapulmonary percussive ventilation provides
high-frequency oscillation of the airway while administering aerosol particles. During intrapulmonary percussive ventilation, the aerosol generator should be placed in the circuit as close to the patient's airway as practical.
When used in conjunction with high-frequency oscillatory ventilation, administration of albuterol sulfate via a VM nebulizer placed between the ventilator circuit and the patient airway has been reported to
deliver greater than 10% of dose to both infants and adults.79,80 A pMDI with adapter placed immediately proximal to the endotracheal tube achieved similar results in adult patients ventilated via high-frequency oscillatory ventilation.81
Drugs for nebulization that escape from the nebulizer into the atmosphere or are exhaled by the patient can be inhaled by
anyone in the vicinity of the treatment. The risk imposed by this environmental exposure is clear and is associated with a range of drugs and patients with infectious disease. Pentamidine and ribavirin were associated with health risks to health care prov
Continuous pneumatic nebulizers produce the greatest amount of
secondhand aerosol, with most (60%) of the aerosol produced passing directly into the environment. The Respirgard II (Vital Signs, Totowa, NJ) nebulizer was developed for administration of pentamidine, adding one-way valves and an expiratory filter to con
The greatest occupational risk for RTs has been associated with
the administration of ribavirin and pentamidine. Conjunctivitis, headaches, bronchospasm, shortness of breath, and rashes have been reported among individuals administering these drugs.83 Patients given aerosolized ribavirin or pentamidine must be treated
When ribavirin or pentamidine is given, the treatment is provided in a
a private room. The room should be equipped for negative pressure ventilation with adequate air exchanges (at least six per hour) to clear the room of residual aerosols before the next treatment. HEPA filters should be used to filter room or tent exhaust,
Booths or stations should be used for
sputum induction and aerosolized medication treatments given in any area where more than one patient is treated. The area should be designed to provide adequate airflow to draw aerosol and droplet nuclei from the patient into an appropriate filtration sys
A variety of booths and specially designed stations are available for delivery of pentamidine or ribavirin
The Emerson containment booth (Figure 36-37) is an example of a system that completely isolates the patient during aerosol administration. The AeroStar Aerosol Protection Cart (Respiratory Safety Systems, San Diego, CA) is a portable patient isolation sta
Filters and nebulizers used in treatments with pentamidine and ribavirin should be treated as
hazardous wastes and disposed of accordingly. Goggles, gloves, and gowns should be used as splatter shields and to reduce exposure to medication residues and body substances. Staff members should be screened for adverse effects of exposure to the aerosol
Personal protective equipment is recommended when
caring for any patient with a disease that can be spread by the airborne route.84 The greatest risk is communication of tuberculosis or chickenpox.
The primary hazard of aerosol drug therapy is
an adverse reaction to the medication being administered. Other hazards include infection, airway reactivity, systemic effects of bland aerosols, and drug reconcentration
For targeting aerosols for delivery to the upper airway (nose, larynx, trachea), particles in the 5- to 20-�m MMAD range are used; for the lower airways,
2- to 5-�m particles are used; and for the lung parenchyma (alveolar region), 1- to 3-�m particles are used.
Where aerosol particles are deposited in the respiratory tract 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.
Hand-bulb atomizers and nasal spray pumps are used to
administer sympathomimetic, anticholinergic, antiinflammatory, and anesthetic aerosols to the upper airway, including nasal passages, pharynx, and larynx (see also Chapter 32). These agents are used to manage upper airway inflammation and rhinitis, to pro
The USN uses a piezoelectric crystal to
generate an aerosol. The crystal transducer converts an electrical signal into high-frequency (1.2- to 2.4-MHz) acoustic vibrations. These vibrations are focused in the liquid above the transducer, where they disrupt the surface and create oscillation wav
Large volume USNs (used mainly for bland aerosol therapy or sputum induction) incorporate
air blowers to carry the mist to the patient (see Chapter 35). Low flow through the USN is associated with smaller particles and higher mist density. High flow yields larger particles and less density. In contrast to jet nebulizers, the temperature of the
Small volume USNs have been promoted for administration of a wide variety of formulations ranging from
bronchodilators to antiinflammatory agents and antibiotics
Two types of VM nebulizers, active and passive, are available commercially.
Active VM nebulizers use a dome-shaped aperture plate, containing more than 1000 funnel-shaped apertures. This dome is attached to a plate that is also attached to a piezoceramic element that surrounds the aperture plate. Electricity applied to the piezoc
The Respimat soft mist inhaler (Boehringer, Ingelheim am Rhein, Germany) is a
small hand-held inhaler that uses mechanical energy to create an aerosol from liquid solutions to produce a low-velocity spray (10 mm/sec) that delivers a unit dose of drug in a single actuation. To operate the device, patients twist the body of the devic