Delivery of inhaled medication in adults
Dean Hess, RRT, PhD
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INTRODUCTION — The inhalation of therapeutic aerosols is an effective method of drug delivery
frequently applied to the management of respiratory disease. Inhalation (or aerosol) therapy can be
employed with a range of medications using a number of different techniques. Examples include:

Inhaled beta agonists and anticholinergic bronchodilators are used to treat chronic
obstructive lung diseases

Inhaled steroids have a central role in the management of asthma

Inhaled antibiotics and mucokinetic agents are therapies for cystic fibrosis and bronchiectasis

Inhaled pulmonary vasodilators are used to manage pulmonary hypertension [ 1]

In the future, patients with nonrespiratory disease may benefit from aerosol delivery of
drugs, including insulin and opiates [2]
OVERVIEW — Three principal types of devices are used to generate therapeutic aerosols: nebulizers,
metered dose inhalers, and dry powder inhalers. All three generate aerosols using different
mechanisms. In many cases, clinicians must choose the most appropriate device for drug delivery as
well as the appropriate therapeutic agent [3].
In addition, the patient technique for proper use differs among these devices. The patient-aerosol
generator interface is an important, but often overlooked, component of patient compliance and
therapeutic response. Ineffective use of any of these devices will result in suboptimal drug
deposition. As a result, patient instruction and compliance are crucial aspects of prescription and use
of these devices.
All three types of devices can be used to efficiently deliver medication to spontaneously breathing
patients. Only nebulizer systems and metered dose inhalers can be used in intubated patients; dry
powder inhalers should not be used in intubated patients.
NEBULIZERS — The basic design and performance of pneumatic (or jet) nebulizers have changed
little over the past 25 years (show figure 1). Nebulizer performance is affected by both technical and
patient-related factors (show table 1) [4,5]. Jet nebulizers are often considered interchangeable.
However, differences in performance among nebulizers produced by various manufacturers have
been reported, some of which have clinical implications [ 6,7]. This may be less important for inhaled
bronchodilators, although newer nebulizer designs should be considered for more expensive
formulations where precise dosing is required. ( See "New nebulizer designs" below).
In addition to differences in design, the performance of nebulizers is influenced by several common
factors, including mechanism, use of mouthpiece or facemask, and drug formulation.
Mechanism — The operation of a pneumatic nebulizer requires a pressurized gas supply, which acts
as the driving force for liquid atomization. Compressed gas is delivered as a jet through a small
orifice, generating a region of negative pressure above the medication reservoir. The solution to be
aerosolized is first entrained, or pulled into the gas stream and then sheared into a liquid film. This
film is unstable, and rapidly breaks into droplets due to surface tension forces.
A baffle placed in the aerosol stream allows formation of smaller particles and recycling of larger
droplets into the liquid reservoir. The aerosol is entrained into the inspiratory gas stream inhaled by
the patient.
The correct technique for use of a nebulizer is important ( show table 2) [8,9]. A number of factors
determine the efficiency of a nebulizer system, including the respirable dose, nebulization time, dead
volume of the device, and the gas used to drive the nebulizer.

Respirable dose — The most important characteristic of nebulizer performance is the
respirable dose delivered to the patient. The respirable dose is a function of the mass output of the
nebulizer and the size of the particles produced. Droplet size should be 2 to 5 µm for airway
deposition and 1 to 2 µm or smaller for parenchymal deposition. Droplet size is usually reported as
mass median aerodynamic diameter (MMAD), which is the median diameter around which the mass
of the aerosol is equally divided.

Nebulization time — Nebulization time, the time required to deliver a dose of medication, is
an important determinant of patient compliance in the outpatient setting. In addition, a reduction in
nebulization time may decrease the need for clinical supervision in hospitalized or emergentlytreated patients. In general, the greater the volume of drug to be delivered and the lower the flow
rate of the driving gas, the longer the nebulization time. Treatment is complete when the nebulizer
begins sputtering.
Although usually given on a scheduled basis, continuous aerosolized bronchodilators can be
administered in the treatment of acute asthma. The available evidence suggests that this therapy is
safe, at least as effective as intermittent nebulization, and may be superior to intermittent
nebulization in patients with the most severe pulmonary dysfunction [ 4,10]. (See "Pathogenesis and
management of status asthmaticus in adults").
Several configurations have been described for continuous nebulization, including frequent refilling of
the nebulizer, use of a nebulizer and infusion pump, and use of a large volume nebulizer [ 4].

Dead volume — The volume of medication trapped inside the nebulizer, and therefore not
available for inhalation, is referred to as the dead volume of the device. The dead volume is typically
in the range of 1 to 3 mL. Increasing the amount of solution within the nebulizer (the fill volume)
reduces the proportion of the dose lost as dead volume. Although nebulizer output increases with a
greater fill volume, this also results in an increase in nebulization time. Considering both factors, a
nebulizer fill volume of 4 to 6 mL is recommended [7].
During nebulization, the solution within the nebulizer becomes increasingly concentrated as water
evaporates from the solution. Thus, on a per breath basis, more medication is delivered late in the
course of a treatment. Evaporative effects also result in cooling of the nebulizer solution over time.
Treatment is complete when the nebulizer begins sputtering.

Driving gas — Increasing the flow rate of the driving gas results in an increase in nebulized
output and a reduction in particle size. A flow of 8 L/min is recommended to optimize drug delivery
[7]. This may be problematic when a compressor is used to power the nebulizer, as the flow from
these is often <8 L/min, resulting in sub-optimal drug aerosolization and delivery [11-13].

Gas density — The density of the gas powering the nebulizer affects nebulizer performance.
For example, the inhaled mass of albuterol is significantly reduced when a nebulizer is powered with a
mixture of helium and oxygen (heliox). Accordingly, the flow to the nebulizer should be increased by
50 percent if it is powered with heliox [14]. Heliox may improve aerosol delivery to the lower
respiratory tract, because the decrease in density results in the creation of smaller particles;
however, the clinical benefit of this approach is unclear [15-20]. (See "Physiology and clinical use of
heliox").
Mouthpieces and facemasks — Inhaled aerosols can be administered using a mouthpiece or a
facemask. Bronchodilator response appears similar with either interface, and some have argued that
the selection of patient interface should be based upon patient preference. Significant facial and eye
deposition of aerosol can occur when a face mask is used, especially in young children [ 21]. Eye
deposition is of particular concern when aerosolized anticholinergic agents are administered, as this
can result in blurring of vision, pupil dilation, and worsening of narrow angle glaucoma. When a
facemask is used, it is important to instruct the patient to inhale through the mouth to minimize
nasopharyngeal deposition of medication. We generally favor use of a mouthpiece, rather than a
face mask, for aerosol administration.
Breathing pattern — The breathing pattern of the patient affects the amount of aerosol deposited in
the lower respiratory tract. Airflow obstruction increases the need for inhaled bronchodilator therapy,
but can decrease the effectiveness of that treatment. To improve aerosol penetration and deposition
in the lungs, the patient should be encouraged to use a slow breathing pattern with an occasional
deep breath.
Drug formulation — Drug formulation can affect nebulizer performance [ 22-24]. Metered dose
inhalers and dry powder inhalers have always been tested and approved as a drug-delivery system
combination. Some drug solutions are only approved for delivery with specific nebulizers [ 25].
Examples of medications that should be delivered only by approved nebulizer include pentamidine,
ribavirin, rhDNAase, and tobramycin.
Nebulizers for specific medications — Specially constructed small-volume nebulizers, such as the
Respirgard II for aerosolized pentamidine, should be used when contamination of the ambient
environment with the aerosolized drug needs to be avoided [ 4]. The Respirgard II is fitted with one-
way valves and filters to minimize gross contamination of the environment.
A separate device was developed to allow the safe delivery of aerosolized ribavirin, which is
potentially teratogenic. The Small-Particle Aerosol Generator (SPAG) was designed specifically to
aerosolize ribavirin. It consists of a nebulizer and drying chamber that reduce the MMAD to about
1.3 µm, which optimizes drug delivery to distal airspaces. The SPAG is used with a scavenging
system to minimize contamination of the ambient environment.
New nebulizer designs — With the traditional nebulizer design, an aerosol is generated throughout
the patient's respiratory cycle. This results in considerable waste of aerosol during exhalation. Newer
designs reduce aerosol waste during the exhalation phase .

Breath-enhanced nebulizers, such as the Pari LC, are designed to allow release of more
aerosol during inhalation. With this design, exhaled gas is routed out the expiratory valve in the
mouthpiece and aerosol is contained in the nebulizer chamber during the expiratory phase.

The Circulaire nebulizer reduces waste from a constant-output nebulizer by attachment of a
storage bag with a one-way valve in the mouthpiece connector. During the expiratory phase, aerosol
is collected in the bag and delivered to the patient on the subsequent inhalation.

The AeroEclipse nebulizer has a breath-actuated valve that triggers aerosol generation only
during inhalation, eliminating the need for a storage bag or reservoir [ 26].
Ultrasonic nebulizers — Ultrasonic nebulizers consist of a power unit and transducer, with or without
an electric fan [4]. The power unit converts electrical energy to high-frequency ultrasonic waves with
a frequency of 1.63 megahertz. A piezoelectric element in the transducer vibrates at the same
frequency as the applied wave. Ultrasonic waves are transmitted to the surface of the solution to
create an aerosol. A fan is used to deliver the aerosol to the patient, or the aerosol is evacuated
from the nebulization chamber by the inspiratory flow of the patient.
Small volume ultrasonic nebulizers are commercially available for delivery of inhaled
bronchodilators; large volume ultrasonic nebulizers are used for sputum induction. A potential issue
with the use of ultrasonic nebulizers is drug inactivation by ultrasonic waves; however, to date this
has not been shown to occur with medications commonly delivered using this system.
Vibrating mesh nebulizers — Several manufacturers have developed aerosol devices that use a
vibrating mesh or plate with multiple apertures to produce a liquid aerosol ( show figure 3) [27]. A
common feature of these devices is their ability to generate aerosols with a high fine-particle
fraction, which results in more efficient drug delivery compared to conventional nebulizers. The
aerosol is generated as a fine mist, and no internal baffling system is required. These nebulizers are
portable, battery-operated, and they have minimal residual medication volume; some are breathactuated [27]. They are being developed in cooperation with pharmaceutical companies to deliver
expensive formulations with which precise dosing is needed.
The iNeb nebulizer uses vibrating mesh technology with adaptive aerosol delivery (ADD). ADD
monitors the patient's breathing pattern and injects the aerosol at the beginning of inhalation. This
improves the likelihood of the aerosol penetrating deep into the respiratory tract. This nebulizer is
used specifically for the administration of Ventavis® (iloprost) Inhalation Solution (CoTherix, Inc) for
the treatment of pulmonary arterial hypertension (show figure 4).
METERED DOSE INHALERS — A metered dose inhaler (MDI) consists of a pressurized canister, a
metering valve and stem, and a mouthpiece actuator (show figure 5) [28]. The canister contains the
drug suspended in a mixture of propellants, surfactants, preservatives, flavoring agents, and
dispersal agents. The propellant has traditionally been a chlorofluorocarbon (CFC). Following
adoption of the Montreal protocol, an international agreement to ban CFCs, CFC-free propellants
such as hydrofluoroalkane (HFA) 133a have become available [29-43]. Patients should be informed
that the plume emitted from an HFA-MDI is warmer and softer than the CFC plume. Without this
information, the patient may interpret the difference in sensation as the aerosol passes through the
upper respiratory tract as an ineffectively delivered dose.
The mixture is released from the MDI canister through a metering valve and stem into an actuator
boot. After volatilization of the propellant, the final volume emitted from the MDI is 15 to 20 mL per
dose [44]. The MDI can be actuated as frequently as every 15 seconds [45]. Lung deposition ranges
between 10 percent and 25 percent of the nominal dose in adults. The correct technique for using a
MDI is shown in the table (show table 3) [8,9]. The Autohaler (3M Corporation), designed for patients
with poor hand-breath coordination, is an example of a flow-triggered MDI that actuates in response
to the patient's inspiratory effort [46-50].
Patient teaching — Important patient teaching issues related to the use of an MDI include priming,
creaming (separation of drug from other ingredients in the canister), and determining when the
canister is empty. When an MDI is new, or if it has not been used for several days (eg, a patient
using inhaled beta-agonists on an as-needed basis), the first several actuations deliver an
inconsistent dose until the metering chamber is primed [51-53]. The clinical effects of this can be
avoided by wasting several actuations from the MDI. Creaming is reversed by shaking the canister
before use [54,55].
Determining when an MDI is empty — It is important for the patient to have a means to determine
when the canister is empty. A few MDIs are now being manufactured with integrated dose counters,
including Ventolin-HFA®, available in the United States as of June 2006 (show figure 6) [56]. Another
method is to have the patient maintain a log of the number of actuations, and to dispose of the
device when the designated number of actuations has been reached. The technique of dropping the
canister into a pan of water and observing how it floats has been shown to be unreliable and is no
longer recommended [57,58]. (See "Metered dose inhaler techniques in adults" and see "Patient
information: Metered dose inhaler techniques").
Spacers and holding chambers — Spacers and valved holding chambers are accessory devices that
reduce oropharyngeal deposition of drug, improve distal delivery, and minimize the importance of
hand-breath coordination. A spacer device is an open-ended tube or bag that allows the MDI plume
to expand and the propellant to evaporate. A valved holding chamber incorporates a one-way valve
that permits aerosol delivery from the chamber only during the inspiratory phase.
Accessory devices either use the boot that comes with the MDI or incorporate a universal canister
adapter to actuate the MDI (show figure 7). A valved holding chamber can incorporate a mask for
patients who are unable to use a mouthpiece due to age, poor coordination, or impaired mental
status. The technique for use of a spacer or valved holding chamber is provided ( show table 4) [8,9].
Drug particles deposit on the inner surface of the device due to static charge on the plastic material
of the chamber [59-61]. For this reason, the chamber may be less effective when it is new compared
to after it has been in use. Washing the device with dishwashing detergent and then allowing it to
air-dry eliminates this static charge [62,63]. Anti-static devices are commercially available from
several manufacturers. It is important to instruct patients to only actuate one dose into the holding
chamber at a time, rather than multiple doses, and to inhale the drug from the chamber
immediately after the MDI has been actuated [64-66].
DRY POWDER INHALERS — Dry powder inhalers (DPIs) create aerosols by drawing air through a
dose of powdered medication (show figure 8 and show figure 9) [67-69]. The release of respirable
particles of the drug requires inspiration at relatively high inspiratory flow rates [ 70,71], which
results in pharyngeal impaction of the larger carrier particles that comprise the bulk of the aerosol.
The oropharyngeal impaction of carrier particles gives the patient the sensation of having inhaled a
dose. DPIs produce aerosols in which most of the drug particles are in the respirable range;
however, the distribution of particle sizes differs significantly among various DPIs.
Because DPIs are breath-actuated, they reduce the problem of coordinating inspiration with
actuation. Breath coordination is still important because exhalation into a DPI blows the powder from
the device. Patients must be instructed to exhale while turned away from the device, then put their
mouth quickly to the mouthpiece and inhale. In addition, since the magnitude and duration of the
patient's inspiratory effort influence aerosol generation from a DPI, these devices should be used
cautiously in the elderly and those with altered mental status or neuromuscular weakness. Finally,
the manipulation required to operate some devices may make use difficult for patients with limited
dexterity. The technique of using DPIs differs among devices ( show table 5A-5B) [8,9].
DPIs can be single- or multi-dose devices. The multi-dose devices contain a month's worth of
medication or more. With single-dose devices, the patient places a capsule into the device
immediately before each treatment. Because these capsules are similar in appearance to oral
medications, it is important to instruct patients not to ingest the capsules.
High ambient humidity produces clumping of the dry powder, creating larger particles that are not as
effectively aerosolized. Multi-dose DPI devices contain individual doses protected from humidity,
which limit this effect. The effect of humidity makes all DPIs ineffective when delivered to patients
receiving mechanical ventilation.
SPONTANEOUSLY BREATHING PATIENTS — For spontaneously breathing patients, there are
advantages and disadvantages to each aerosol delivery device ( show table 6). However, the available
evidence from systematic reviews and meta-analyses suggests equivalence among nebulizers,
metered dose inhalers, and dry powder inhalers with respect to drug delivery when used correctly
[72-78]. Accordingly, the selection of an aerosol delivery device is not based on a clear superiority of
one device over another [3].
The selection of an aerosol delivery device is usually based upon the preference and convenience of
the clinician and patient, the ability of the patient to use the device correctly, and the cost of
therapy. The selection of device is also limited by drug formulation, as some formulations are only
available for one delivery device. The nebulizer is often considered the most expensive aerosol
delivery device. The prescription of multiple delivery devices can be confusing, and may impair
compliance with therapy, particularly in patients with complicated regimens [ 79].
Regardless of the delivery technique, patient instruction in the proper use of the device is crucial. All
health care professionals interacting with the patient share responsibility for this teaching; this
includes physicians, respiratory therapists, nurses, and pharmacists. Thus, all involved clinicians also
must take responsibility to understand the correct use of aerosol delivery devices.
Patients with tracheostomies — Techniques have also been described for the delivery of aerosols by
nebulizer or MDI in a spontaneously breathing patient with a tracheostomy tube ( show figure 10)
[80].
MECHANICALLY VENTILATED PATIENTS — Nebulized medications can be delivered to patients
receiving mechanical ventilation using either an MDI or a nebulizer. A DPI cannot be used to deliver
dry powder during mechanical ventilation because ventilator circuit humidification impairs aerosol
formation.
A number of factors affect aerosol delivery during mechanical ventilation ( show table 7) [81-87]. One
major factor is that humidification of inhaled gas decreases aerosol deposition by approximately 40
percent due to increased particle drug deposition in the ventilator circuit. For this reason, increased
dosage of medication is often required to achieve a therapeutic effect in mechanically ventilated
patients.
Metered dose inhaler — A special actuator is needed to adapt the MDI into the ventilator circuit
(show figure 11). The size, shape, and design of these actuators have a major impact on drug delivery
to the patient. An MDI with a chamber results in a four- to six-fold greater delivery of aerosol than
MDI actuation into a connector attached directly to the endotracheal tube, or into an in-line device
that lacks a chamber. When using an MDI during mechanical ventilation, it is important to
synchronize actuation with inspiratory airflow to optimize drug delivery.
Helium-oxygen mixtures also affect aerosol deposition, and in vitro modeling has reported a 50
percent increase in deposition of albuterol from an MDI during mechanical ventilation when heliox
was used as the driving gas [88]. However, heliox can dramatically interfere with the functioning of
flow sensors and oxygen levels when delivered through a mechanical ventilator, and care must be
taken if this approach is employed [89-91]. (See "Physiology and clinical use of heliox", section on
Instrument sensitivity).
Nebulizer — Delivery of a large tidal volume, use of an end-inspiratory pause, and use of a slow
inspiratory flow affect aerosol delivery by nebulizer but not by MDI [81]. Nebulizer performance can
be optimized by placing the nebulizer 30 cm from the endotracheal tube, rather than at the Y-piece,
because the inspiratory ventilator tubing acts as a spacer. Operating the nebulizer only during
inspiration is more efficient for aerosol delivery compared with continuous aerosol generation. When
a breath-actuated nebulizer is used, the delivered dose increases by more than five-fold. In addition,
when the humidifier is bypassed the delivered dose increases by a factor of nearly four [ 82].
Disadvantages of nebulizer use during mechanical ventilation include circuit contamination,
decreased ability of the patient to trigger the ventilator, and the associated increases in tidal volume
and airway pressure due to nebulizer flow. (See "Ventilator circuit change and ventilator-associated
pneumonia").
Choice of device — Although the nebulizer is less efficient than the metered dose inhaler during
mechanical ventilation, the nebulizer can deliver a greater cumulative dose to the lower respiratory
tract [92]. Thus, nebulizers and MDIs produce similar therapeutic effects in mechanically ventilated
patients [93]. The use of an MDI for routine bronchodilator therapy in ventilator-supported patients
is preferred because of the problems associated with the use of nebulizers, including contamination
and triggering difficulty, as well as increased pressure and volume delivery.
Aerosol delivery by MDI is easy to administer, involves less personnel time, provides a reliable dose
of the drug, and is free from the risk of bacterial contamination. When an MDI is used with an in-line
spacer, the ventilator circuit does not need to be disconnected with each treatment; this may reduce
the risk of ventilator-associated pneumonia. This also prevents the loss of positive end-expiratory
pressure (PEEP) in patients with acute respiratory distress syndrome (ARDS). ( See "Ventilator circuit
change and ventilator-associated pneumonia", and see "Mechanical ventilation in acute respiratory distress
syndrome").
Aerosol therapy can also be administered during noninvasive positive pressure ventilation (NPPV)
(show figure 12) [94,95]. In patients with acute asthma randomized to albuterol delivery by NPPV
versus conventional nebulizer, a greater improvement in peak expiratory flow occurs in patients
randomized to receive NPPV [96]. Benefit for the delivery of albuterol by MDI with spacer during
NPPV has also been reported [97]. (See "Treatment of acute exacerbations of asthma in adults" and see
"Noninvasive positive pressure ventilation in acute respiratory failure").
INFORMATION FOR PATIENTS — Educational materials on this topic are available for patients. ( See
"Patient information: Overview of managing asthma", see "Patient information: Trigger avoidance in asthma",
see "Patient information: Metered dose inhaler techniques", and see "Patient information: How to use a peak
flow meter"). We encourage you to print or e-mail these topics, or to refer patients to our public web
site www.patients.uptodate.com, which includes these and other topics.
SUMMARY — Effective delivery of inhaled medications requires selection of the appropriate drug,
proper use of the delivery device, education of the patient in the correct use of the device, and
patient compliance. Frequent review of the proper use of the device is crucial. All health care
professionals interacting with the patient share responsibility for this teaching and should personally
understand the correct use of the various devices.
Available devices

Three principal types of devices are used to deliver inhaled medications: nebulizers, metered
dose inhalers (MDIs), and dry powder inhalers (DPIs). The nebulizer is often considered the most
expensive aerosol delivery device. (See "Overview" above)

The most commonly-used type of nebulizer is the pneumatic (or jet) nebulizers ( show figure
1). Nebulizer performance is affected by both technical factors, such as mechanism of aerosol
generation and drug formulation (not all medications can be used with all nebulizers), as well as
patient-related factors (show table 1). (See "Nebulizers" above).

With all of the standard nebulizers, patients should be encouraged to use a slow breathing
pattern with an occasional deep breath. We generally favor the use of mouthpieces over face masks,
as the latter are associated with some facial and eye deposition of aerosol. ( See "Mouthpieces and
facemasks" above).

Newer nebulizer designs include breath-actuated devices that deliver the majority of the
medication during inhalation, and vibrating mesh nebulizers that produce a very fine mist of
aerosolized medication and deliver more of the dose to the patient. (See "New nebulizer designs"
above).

A MDI consists of a pressurized canister, a metering valve and stem, and a mouthpiece
actuator (show figure 5) [28]. CFC propellants are gradually being replaced with non-CFC agents,
such as hydrofluoroalkane (HFA). Lung deposition ranges between 10 and 25 percent of the nominal
dose in adults. (See "Metered dose inhalers" above).

The correct technique for using a MDI is shown in the table (show table 3). The Autohaler is an
example of a flow-triggered MDI that actuates in response to the patient's inspiratory effort and can
be useful to patients who have trouble coordinating breathing and actuation. Patients should also be
taught about the importance of priming and shaking the canister before use, and how to determine
when the canister is empty. (See "Metered dose inhalers" above).

MDIs can be used with spacers and valved holding chambers, accessory devices that reduce
oropharyngeal deposition of drug, improve distal delivery, and minimize the importance of handbreath coordination. (See "Spacers and holding chambers" above).

DPIs create aerosols by drawing air through a dose of powdered medication ( show figure 8 and
show figure 9). The technique of using DPIs differs among devices ( show table 5A-5B). (See "Dry powder
inhalers" above).
Options for different patient situations

For spontaneously breathing patients, there are advantages and disadvantages to each
aerosol delivery device (show table 6). However, nebulizers, MDIs, or DPIs are all effective when used
correctly. Thus, we recommend selecting a delivery device based upon convenience, cost, and the
patient's preferences and ability to use the device correctly ( Grade 1B). (See "Spontaneously breathing
patients" above).

Techniques have also been described for the delivery of aerosols by nebulizer or MDI in a
spontaneously breathing patient with a tracheostomy tube ( show figure 10). (See "Patients with
tracheostomies" above).

In mechanically-ventilated patients, both MDIs and nebulizers are equivalently effective. We
suggest the use of MDIs, because this method is technically easier, involves less personnel time,
provides a reliable dose of the drug, and is free from the risk of bacterial contamination that can
occur with a nebulizer (Grade 2B). Patients can also receive inhaled therapies during NPPV. ( See
"Mechanically ventilated patients" above).
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GRAPHICS
Pneumatic nebulizer
Pneumatic nebulizer
A jet flow of driving gas creates an area of low pressure above the medication reservoir,
generating an aerosol. The baffle helps insure the formation of respirable particles, and
prevents inhalation of oversized droplets of medication. Most nebulizers require a flow rate
of 8 liters per minute for optimum performance.
Nebulizer performance
Factors affecting aerosol delivery by nebulizer
Technical Factors
Mechanism and manufacturer
Patient Factors
Flow rate
Breathing pattern
Fill volume
Nose vs mouth breathing
Solution characteristics
Artificial airway
Characteristics of driving gas
Airway obstruction
Designs to enhance output
Positive pressure level
Continuous vs. intermittent delivery
Nebulizer technique
Technique for use of medication nebulizer
Assemble apparatus
Add medication to nebulizer
Use a fill volume of 4 to 6 mL
Attach a gas source with a flow of 8 L/min
Place patient in a comfortable position
Instruct patient to breathe through the mouth
Periodically tap nebulizer to return impacted particles to reservoir.
Encourage patient to breathe with a slow inspiratory flow and an occasional deep breath
Assess patient for comfort, adverse effects, and response throughout treatment
Terminate treatment when nebulizer begins to sputter
Nebulizers vibrating mesh
Vibrating mesh nebulizers
Vibrating mesh nebulizers generate fine mists with more efficient dry delivery and minimal
residual medication volume compared to conventional nebulizers.
Nebulizer iNeb
iNeb nebulizer showing device and principle of operation
The iNeb nebulizer monitors the patient's breathing pattern and injects the aerosolized
medication at the start of each inhalation. It is used for the administration of iloprost.
Metered dose inhaler
Metered dose inhaler
Medication is stored under pressure in the canister and released in fixed volumes from the
dosing chamber following actuation.
Metered dose inhaler technique
Technique for use of a MDI
Warm the MDI canister to body temperature
Shake vigorously
Uncap mouthpiece and check for loose objects in the device
Open mouth and keep tongue from obstructing the mouthpiece
Hold the MDI in a vertical position, with the outlet aimed at the mouth
Place canister outlet between lips or position it about 4 cm from the mouth
Breathe out normally
Breathe in slowly; actuate the MDI at beginning of inspiration
Continue to inhale to total lung capacity
Hold breath for 4 to 10 seconds
Wait at least 15 seconds between actuations
Recap mouthpiece
MDI with counter
MDI with counter
Some MDIs are now manufactured with built-in dose counters.
MDI spacers
Accessory devices used with metered dose inhalers
(A) AeroChamber, (B) AeroChamber with mask, and (C) InspirEase. These devices can
facilitate the use of metered dose inhalers and decrease the amount of drug deposited on
the upper airway.
MDI with spacer technique
Technique for use of MDI with spacer or valved holding chamber
Warm MDI canister to body temperature
Assemble apparatus and check for loose objects in the device
Shake canister vigorously
Hold canister in vertical position
Breathe out normally
Place holding chamber in mouth, or place mask completely over nose and mouth
Encourage patient to breathe through mouth
Breathe in slowly and actuate MDI once at the beginning of inspiration
Allow 15 seconds between actuations
Dry powder inhalers
Examples of various dry powder inhalers
With these devices, the patient inhales the medication in the form of a fine powder rather
than an aerosol. (A) Aerolizer, (B) Turbuhaler, (C) Diskus, (D) Diskhaler, (E) HandiHaler.
Courtesy of Dean Hess, RRT, PhD.
DPI twisthaler
The twisthaler device
Dry powder inhaler technique I
Technique for use of various dry powder inhalers - I
Aerolizer
Remove cover and hold the base of inhaler.
Twist mouthpiece in counter-clockwise direction.
Remove capsule from foil blister immediately before use and place capsule in the base of the inhaler.
Hold the base of the inhaler and turn clockwise to close.
Simultaneously press both buttons once to pierce the capsule.
Exhale normally - do not exhale into the mouthpiece.
Tilt head back slightly, hold device horizontal with the buttons on the left and right, place
mouthpiece into the mouth, and close lips around mouthpiece.
Breathe in rapidly and steadily, as deeply as possible; hold breath.
Remove device from mouth and exhale outside device.
Open chamber and examine capsule; if powder remains, repeat inhalation process.
After use, remove and discard capsule, and cover mouthpiece; store device in cool, dry place.
Diskhaler
Remove mouthpiece cover and pull tray out from device.
Place disk on wheel with numbers facing up.
Rotate disk by sliding tray out and in.
Lift back of lid until fully upright so that needle pierces both sides of blister.
Keep device level while inhaling dose with a rapid and steady flow.
Breathe in rapidly and steadily, as deeply as possible; hold breath.
Remove device from mouth and exhale outside device.
Brush off any powder remaining within device once every week; store device in cool, dry place.
Diskus
Open the device and slide the lever until it clicks.
Keep device level while inhaling dose.
Breathe in rapidly and steadily, as deeply as possible; hold breath.
Remove device from mouth and exhale outside device; store device in cool, dry place.
Dry powder inhaler technique II
Technique for use of various dry powder inhalers - II
HandiHaler
Capsules should be stored in sealed blisters and only removed immediately before use.
Peel back the foil using the tab until one capsule is fully visible.
Open the dust cap by pulling it upwards, then open the mouthpiece.
Place the capsule in the center chamber (it does not matter which end of the capsule is placed in the
chamber).
Close the mouthpiece firmly until you hear a click, leaving the dust cap open.
Hold the HandiHaler with the mouthpiece upwards and press the piercing button completely in once
and release.
Breathe out completely. Do not breathe into the mouthpiece at any time.
Close your lips tightly around the mouthpiece.
Breathe in rapidly and steadily, as deeply as possible; hold breath.
To ensure you get the full dose, repeat the inhalation from the HandiHaler as described.
After the dose, open the mouthpiece, tip out the used capsule, and dispose. Do not handle used
capsules.
Close the mouthpiece and dust cap for storage; store device in cool, dry place.
Turbuhaler
Twist and remove cover.
Hold inhaler upright with mouthpiece facing up.
Turn grip right then left until it clicks.
Inhaler may be held upright or horizontal.
Breathe in rapidly and steadily, as deeply as possible; hold breath.
Remove device from mouth and exhale outside device.
Replace cover and twist to close; store device in cool, dry place.
Twisthaler
Hold the inhaler straight up with the pink portion (the base) on the bottom.
Remove the cap while it is in the upright position to make sure you get the right amount of medicine
with each dose.
Hold the pink base and twist the cap in a counter-clockwise direction to remove it.
As you lift off the cap, the dose counter on the base will count down by 1. This action loads the
medicine that you are now ready to inhale.
Make sure the indented arrow located on the white portion (directly above the pink base) is pointing
to the dose counter.
Breathe out normally - do not exhale into the device.
Place the mouthpiece into your mouth, with the mouthpiece facing towards you, and close your lips
tightly around it.
Inhale dose with a rapid and steady flow while holding the Twisthaler horizontal.
Remove the mouthpiece from your mouth and hold your breath for 5 to 10 seconds (or as long as
you comfortably can).
When you exhale, be sure that you are not exhaling into the device
Immediately replace the cap and turn in a clockwise direction as you gently press down until you
hear a click.
Firmly close the Twisthaler to assure that your next dose is properly loaded.
Be sure that the arrow is in line with the dose-counter window.
Store device in cool dry place.
The dose counter displays the number of doses remaining. When the unit reads 01, this indicates the
last remaining dose. When the counter reads 00, the unit must then be discarded.
Aerosol device comparison
Advantages and disadvantages of various aerosol devices
Type
Jet nebulizer
Advantages
Patient coordination not
required
Disadvantages
Expensive
High doses possible
Not portable - pressurized gas source
required
No CFC release
More time required
Contamination possible
Device preparation required before
treatment
Not all medications available
Less efficient than other devices (dead
volume loss)
Ultrasonic nebulizer
Patient coordination not
required
Expensive
Contamination possible
High doses possible
Prone to malfunction
No CFC release
Not all medication available
Small dead volume
Quiet
Device preparation required before
treatment
No drug loss during
exhalation
Faster delivery than jet
nebulizer
Metered-dose inhaler
Convenient
Patient coordination essential
Less expensive than
nebulizer
Patient actuation required
Large pharyngeal deposition
Portable
Difficult to deliver high doses
More efficient than
nebulizer
No drug preparation
required
Many use CFC propellants
Not all medications available
Difficult to contaminate
Metered-dose inhaler with
holding chamber
Less patient coordination
required
More complex for some patients
More expensive than MDI alone
Less pharyngeal deposition
Less portable than MDI alone
Dry powder inhaler
Less patient coordination
required
Requires moderate to high inspiratory
flow
Convenient
Some units are single dose
Breath-hold not required
Can result in high pharyngeal deposition
Propellant not required
Not all medications available
Portable
Difficult to deliver high doses
Breath-actuated
CFC: chlorofluorocarbon; MDI: metered-dose inhaler.
From Consensus Statement: Aerosols and Delivery Devices. Respir Care 2000; 45:589.
MDI use with trach
Equipment for aerosol delivery to tracheostomy in spontaneously breathing patients
Aerosol delivery ventilator
Factors affecting aerosol delivery during mechanical ventilation
Nebulizer
Position of nebulizer placement in the circuit
Type of nebulizer and fill volume
Treatment time
Duty cycle (I:E ratio)
Ventilator brand
MDI
Type of actuator
Timing of actuation
Nebulizer and MDI
Endotracheal tube size
Humidification of the inspired gas
MDI in-line spacer
Inline metered dose inhaler spacing device
Using a chamber results in a four- to six-fold greater delivery of aerosol than actuation into
a connector attached directly to the endotracheal tube, or into an inline device that lacks a
chamber.
Neb or MDI use with NPPV
Aerosolized medications, either by nebulizer or MDI, can be administered during NPPV
Grade 1B
Grade 1B recommendation
A Grade 1B recommendation is a strong recommendation, and applies to most patients. Clinicians
should follow a strong recommendation unless a clear and compelling rationale for an alternative
approach is present.
Explanation:
A Grade 1 recommendation is a strong recommendation. It means that we believe that if you follow
the recommendation, you will be doing more good than harm for most, if not all of your patients.
Grade B means that the best estimates of the critical benefits and risks come from randomized,
controlled trials with important limitations (eg, inconsistent results, methodologic flaws, imprecise
results, extrapolation from a different population or setting) or very strong evidence of some other
form. Further research (if performed) is likely to have an impact on our confidence in the estimates
of benefit and risk, and may change the estimates.
Recommendation grades
1. Strong recommendation: Benefits clearly outweigh the risks and burdens (or vice versa)
for most, if not all, patients
2. Weak recommendation: Benefits and risks closely balanced and/or uncertain
Evidence grades
A. High-quality evidence: Consistent evidence from randomized trials, or overwhelming
evidence of some other form
B. Moderate-quality evidence: Evidence from randomized trials with important limitations,
or very strong evidence of some other form
C. Low-quality evidence: Evidence from observational studies, unsystematic clinical
observations, or from randomized trials with serious flaws
For a complete description of our grading system, please see the UpToDate editorial policy
that can be found by clicking on Help, and then About UpToDate
Grade 2B
Grade 2B recommendation
A Grade 2B recommendation is a weak recommendation; alternative approaches may be better for
some patients under some circumstances.
Explanation:
A Grade 2 recommendation is a weak recommendation. It means "this is our suggestion, but you
may want to think about it." It is unlikely that you should follow the suggested approach in all your
patients, and you might reasonably choose an alternative approach. For Grade 2 recommendations,
benefits and risks may be finely balanced, or the benefits and risks may be uncertain. In deciding
whether to follow a Grade 2 recommendation in an individual patient, you may want to think about
your patient's values and preferences or about your patient's risk aversion.
Grade B means that the best estimates of the critical benefits and risks come from randomized,
controlled trials with important limitations (eg, inconsistent results, methodologic flaws, imprecise
results, extrapolation from a different population or setting) or very strong evidence of some other
form. Further research (if performed) is likely to have an impact on our confidence in the estimates
of benefit and risk, and may change the estimates.
Recommendation grades
1. Strong recommendation: Benefits clearly outweigh the risks and burdens (or vice versa)
for most, if not all, patients
2. Weak recommendation: Benefits and risks closely balanced and/or uncertain
Evidence grades
A. High-quality evidence: Consistent evidence from randomized trials, or overwhelming
evidence of some other form
B. Moderate-quality evidence: Evidence from randomized trials with important limitations,
or very strong evidence of some other form
C. Low-quality evidence: Evidence from observational studies, unsystematic clinical
observations, or from randomized trials with serious flaws
For a complete description of our grading system, please see the UpToDate editorial policy
that can be found by clicking on Help, and then About UpToDate.