Nebulizers - (Naso - Pulmonary Drug Delivery Systems)


(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 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 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



       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.


       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.


       Little patient coordination required

       Small dead volume


       Aerosol accumulates during exhalation

       High doses possible

       No chlorofluorocarbon release

        Fast drug delivery



       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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