Nebulizers – (Naso – Pulmonary Drug Delivery Systems)

Nebulizers

(Naso – Pulmonary Drug Delivery Systems)

Intended
learning outcomes

At the end of the session students will be able to:

  1.  Generalize the reasons for the usage of
    nebulizers

  2. Enlist
    the indications of nebulization

  3. Recall
    the factors influencing performance of nebulizers

  4. Differentiate
    several types of nebulizers

  5. Elaborate
    the technical differences between types of nebulizers

Nebulizers

       Nebulizers
are the oldest form of aerosol generation. Although they have been commonly
used for many years, their basic design and performance has changed little over
the past 25 years.

       Nebulizers
are most commonly used for bronchodilator administration, and it is well
established that nebulized bronchodilators produce a physiologic response.

       Because
bronchodilators are relatively inexpensive, there is little market pressure to
improve nebulizer performance.

Nebulization

       Nebulization
is means of administering drugs by inhalation. Equalizer breaks up the solution
to be inhaled into fine droplets which are then suspended in a stream of gas.

       The
patient actively inhales this gas stream containing the drug

       A
nebulizer is a machine that takes an asthma medication and through its
compressor, turns it into a fine misty aerosol.

       The
medication thus dispersed is inhaled directly into the airways. The diameter of
the aerosol particles is a major factor that influences its site of deposition
inside the lungs.

        Aerosol particles between 1 to 5 microns (a
micron is a thousandth part of a millimeter) manage to reach even the distal
parts of the airways where they are most effective drug.

       The
process of pneumatically converting a bulk liquid into small droplets is called
atomization.

        Pneumatic nebulizers have baffles incorporated
into their design so that most of the droplets delivered to the patient are
within the respirable size range of 1–5 micron meter

Although the first choice of aerosol generator for the
delivery of bronchodilators and steroids is the metered dose inhaler.

 

Nebulizers remain useful for several reasons.

        First, some drugs for inhalation are available
only in solution form.

        Second, some patients cannot master the
correct use of metered-dose inhalers or dry powder inhalers.

        Third, some patients prefer the nebulizer over
other aerosol generating devices

       In
fact, the market generally prefers an inexpensive nebulizer rather than a
high-performance nebulizer for bronchodilator administration.

        However, there are newer drugs available for
inhalation that are expensive and for which precise dosing may be important.

       These
include dornase alfa, tobramycin, and pentamidine.

       Nebulizer
performance is affected by both technical and patient-related factors

Technical
Factors

       Manufacturer
of nebulizer Gas flow used to power nebulizer Fill volume of nebulizer

       Solution
characteristics

       Composition
of the driving gas

       Designs
to enhance nebulizer output

        Continuous versus breath-actuated

Patient
Factors

       Breathing
pattern

        Nose versus mouth breathing

       Composition
of inspired gas

       Airway
obstruction

       Positive
pressure delivery

       Artificial
airway

        and mechanical ventilation

Indications of Nebulization:

1) Delivery of
bronchodilator drugs: –
On acute attack of asthma Nebulization is the most
common means of delivery. Respiratory patients who are too short of breath to
use pressurized aerosol or Rota haler effectively may be prescribed
bronchodilators.

2)  Infants and children with asthma: –
Inhalation by nebulizer is the only means of effective inhalation therapy until
a child is about 4 yrs. Old.

3) Administration of antibiotics and antifungal agents. In
some cases of resistant chest infections for e.g. cystic fibrosis or
bronchiectasis, antibiotics may be prescribed to be inhaled directly into the
lungs.

 4) To aid expectoration: – Inhalation of
hypertonic saline has been found to increase clearance of bronchial secretions.

 5) Local analgesia: – To relieve dyspnea
in some terminally in patients such as those suffering from alveolar carcinoma

Preparation of articles: –

        Nebulizers Pressurized gas source

       Flow
meter

       Oxygen
tubing

        T- Piece mouthpiece or mask or other
appropriate gas delivery device.

       Sterile
normal saline solution or sterile distilled water 5 ml syringe and water.

       Prescribed
medication Suction equipment

       Sputum
mug

       Kidney
tray

        Stethoscope

       B.P.apparatus,

       TPR
tray

       The
operation of a pneumatic nebulizer requires a pressurized gas supply as the
driving force for liquid atomization .Compressed gas is delivered through a
jet, causing a region of negative pressure.

       The
solution to be aerosolized is entrained into the gas stream and is sheared into
a liquid film.

        This film is unstable and breaks into droplets
because of surface tension forces.

       A
baffle is placed in the aerosol stream, producing smaller particles and causing
larger particles to return to the liquid reservoir.

       More
than 99% of the particles may be returned to the liquid reservoir. The aerosol
is delivered into the inspiratory gas stream of the patient.

        Before delivery into the patient’s respiratory
tract, the aerosol can be further conditioned by environmental factors such as
the relative humidity of the carrier gas.

       Determinants
of droplet size produced by nebulizers include the characteristics of the
solution (density, viscosity, and surface tension), the velocities of the gas
and solution, and the flow rates for the gas and the solution.

        The most important factors are gas velocity
and the ratio of liquid to gas flow.

        An increase in gas velocity decreases droplet
size, whereas an increase in the ratio of liquid to gas flow increases particle
size.

        It is interesting to note that gas velocity
affects the flow rates for both the gas and the solution.

        Thus, it is impossible to separately control
the primary factors affecting droplet size from nebulizers.

       An
important consideration in the use of nebulizers is the dead volume of the
device.

       Dead
volume refers to the amount of solution that is trapped inside the nebulizer
and is thus not made available for inhalation.

       The
dead volume is typically in the range of 1 to 3 mL.

        Dead volume is minimized by using a conical
shape of the nebulizer, by decreasing the surface area of the internal surface
of the nebulizer, and by improving the wetness of the plastic surface of the
nebulizer.

       To
reduce medication loss due to dead volume, clinicians and patients may tap the
nebulizer periodically during therapy, which has been shown to increase
nebulizer output.

       With
the internal mixing design (a), gas flow interacts with the solution
prior to leaving the exit port.

       With
external mixing (b), gas and the solution interact after both leave the
nozzle.

       Modifications
on these designs are used by nebulizer manufacturers, without clear superiority
of one approach over the other.

Types of
Nebulizer

There are two types of Nebulizer

 1. Pneumatic
Nebulizer

 2. Ultrasonic
Nebulizer

 

1.
Pneumatic Nebulizer

Pneumatic nebulizer sucks the liquid sample in the flow of
high pressure gas and break into small drops when strikes the glass beed

A high velocity of gas is blown through a fine hole creating
an area of negative pressure.

 Fluid is drawn from
the reservoir by the Bernville effect into the jet stream and is impacted on a
battle breaking the fluid into droplets large droplets fall back to into the
reservoir while the smaller ones may be inhaled

Types of Pneumatic
Nebulizer

There are four types of pneumatic Nebulizer

1. Concentric tube

2. Cross disk

3. Fritted disk

4. Babington

Concentric tube

       In
this nebulizer the liquid sample is drown through a capillary tube by a high
pressure stream of gas flowing around the tip of tube.

       The
high velocity gas break up the liquid in droplets and carried to atomizer

Cross flow

The high pressure gas flow across a capillary tip at the
right angle.

Fritted disk

The sample solution is pumped onto a fritted surface through
which carrier gas flows.

Babington

       Consist
of a hollow sphere in which a high pressure gas is pumped through a small
orifice in the spheres surface.

       The
expanding jet of gas nebulizes the liquid sample flowing in a thin film over
the spheres surface.

2.
Ultrasonic nebulizer

       An
ultrasonic nebulizer is a small portable device that uses ultrasonic sound
waves to break liquid particles down into a fog on that they can inhale

       High
frequency sound waves are passed through a solution in a reservoir to create an
aerosol.

       Advantage
is that they operate quietly but they are less robust and need more careful
maintenance than jet nebulizers and air compressors.

        Some of these nebulizers depend on patient’s
ability to breathe in actively to open a valve.

       Some
children and other patients with poor long function may find this difficult.

        It is indicated for those in short therapeutic
sessions. Indicated for the patient with thick secretions, to mobilize
secretions and facilitate a productive cough d easily.

Advantages

       Little
patient coordination required

       Small
dead volume

        Quiet

       Aerosol
accumulates during exhalation

       High
doses possible

       No
chlorofluorocarbon release

        Fast drug delivery

Disadvantages

       Expensive

       Contamination
possible

       Prone
to electrical and mechanical breakdown

       Not
all drug formulations available

        Drug preparation required

Procedure
for using Nebulizer

1. Plug the power cord into the electrical outlet.

2. Open the nebulizer cup by turning the upper part
counter-clockwise.

3. Pour into the cup, the quantity of drug as prescribed by
the physician.

 4. Close the nebulizer
by turning the upper part clockwise.

5. Connect the cup to the unit’s air outlet by means of the
tube

6. Apply one of the required accessories; mouthpiece or
mask, to the cup.

7. Position yourself comfortably in a sitting position in
front of the nebulizer.

8. Start the unit by turning the switch on.

9. See that the medication in the nebulizer cup is forming
the mist.

 10. Put your lips
securely around the mouthpiece, or position the mask around your face and
inhale as slowly and deeply as possible. Concentrate on inhaling the medication
as directed.

11. Hold your breath for one to two seconds and exhale
slowly.

12. Continue to breathe through the nebulizer until (a) you
have used all the drug, or (b) have taken the treatment for the prescribed
time.

13. Turn the machine off, and, if needed, cough several
times to bring up any mucus or secretions.

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