A nebulizer is a device that turns water-based solutions into drops. It is one of the easiest ways to take inhaled medication and the preferred method for young children and the elderly. Still, its use comes with certain limitations. Read on to find out more about nebulizers, how they work, what are the most common uses, and how to use them safely.
What is a Nebulizer?
A nebulizer is a machine that turns water-based solutions into drops that are inhaled and small enough to reach the lungs (1 to 5 μm). It is usually used with drugs that help expand the lung passages, bronchi (bronchodilators). The direct delivery of the medication to the lungs reduces the dose and side effects [1, 2].
The droplets are generated using different methods: air-blast atomization, high-frequency vibrations, and colliding liquid jets (more information is in the Components section). These often determine the kind of drugs used with the device and its cost .
Who Should Use It?
Nebulizers are mostly used in patients that cannot use a specific breathing technique or coordinate their movements (hand-eye-breath coordination), such as in young children and the elderly. They are easily used as long as the person is breathing normally .
The use of home nebulizers is also recommended for patients with frequent airflow obstruction or low volume of breathing, or for those that need medications or doses not available for regular inhalers (dry-powder or metered-dose inhalers) .
Mechanism of Action
Drops with a size 2 to 5 μm reach the higher parts of the airway while smaller drops (1 to 2 μm) can reach deeper .
They reach the airways in different ways, such as by:
- Impaction, when big drops with a high-speed crash with the walls of the airway, usually in the upper parts. This also happens during exhalation 
- Sedimentation, which usually happens in the middle of the airway, where particles at a lower speed settle on the surface due to gravity. This is increased by holding your breath 
- Diffusion, the random movement of very small particles that eventually causes them to crash with the walls of the airway 
The nebulized drug must pass several barriers to be able to reach its target. In the upper airway, a layer of mucus covers the surface and removes foreign particles by “pushing” them out into the throat to be swallowed .
In the lower airway, white blood cells (macrophages) “eat” foreign particles 1 to 2 μm in size. The nebulized drug must be small enough to reach the lower airway, and have a chemical composition that interferes with sticking to the mucus or that helps cross it [7, 6].
The use of a mask is recommended for conditions such as allergic rhinitis. When looking to deliver a greater amount of aerosol into airways, a mouthpiece should be used to avoid being filtered by the nose .
The size of the inhaled particles should ideally be between 1 to 3 μm .
In jet nebulizers, compressed gas generates the drops (as an aerosol) containing the medication. A reservoir tube that helps maintain a continuous flow is commonly used. A collection bag that collects the drops not inhaled is another option [2, 8].
Other forms of jet nebulizers are the breath-actuated and breath-enhanced. While both help reduces the loss of medicine, their different designs also help minimize treatment times or deliver the desired dose more precisely [8, 9].
The main disadvantage of jet nebulizers is that they are noisy. They also take more time for each treatment and tend to cool the solvent, which can be uncomfortable for the patient .
In this case, a crystal vibrates at high frequencies (more than 20 kHz) to create the drops. They usually are smaller, silent, and have shorter dosing times. However, they should not be used with suspensions or with medications that are damaged by heating (proteins) [11, 10].
In mesh nebulizers, a vibrating mesh creates the drops and determines their size. They have faster treatment times and reduce drug waste. However, highly concentrated or very thick solutions can damage the mesh [2, 10, 12].
The interface is one of the most important parts of the equipment, as it’s the part that delivers the medicine. The choice of an interface depends on the age and ability of the patient to cooperate (children or the elderly) .
In hospitals, a mouthpiece is preferred for patients and children older than 3 years. For younger children, a face mask that covers both nose and mouth is used. It is very important that the face mask fits tightly and comfortably to avoid leaks [2, 3].
For babies, masks that incorporate a pacifier or allow the use of a pacifier while covering only the nose are available. Alternatively, hoods or tents can also be used [13, 2].
3) Nebulizer Cup or Medication Reservoir
The indicated amount of medicine is placed in this container. It should be rinsed and dried after each use, and periodically disinfected according to the manufacturer’s instructions .
Certain nebulizer models have plastic tubing that connects the aerosol generator to the nebulizer cup and the interface. It should be carefully assembled before every use, and should not be washed .
Some nebulizers have special models for children that include accessories to keep the child entertained during the course of the treatment.
Make sure to consult with your doctor and follow their instructions precisely before applying any drug in a nebulized form, even if you are already using that drug. Drugs can have distinct health effects when nebulized, and their use requires medical supervision.
Asthma is a disease where the entire airway is swollen. Inhaled drugs help treat this inflammation by allowing high doses of drugs to reach their target site directly .
Nebulizers are recommended for patients, such as children, that cannot adequately use conventional inhalers. Nebulizers are also recommended during acute asthma attacks to deliver medications that help expand the airways (such as albuterol) .
In patients with occasional asthma attacks, short-acting beta-2 agonists are used whenever needed. They expand the airway by relaxing the muscles that surround it and quickly relieve the symptoms. Salbutamol and terbutaline are most used .
Corticosteroids are used to reduce inflammation and control asthma in the long term. Beclometasone, budesonide, ciclesonide, fluticasone, and mometasone are commonly prescribed [16, 14].
Long-acting beta-2 agonists (such as formoterol and salmeterol) are also used when asthma cannot be controlled by corticosteroids alone .
Another class of drugs that relaxes the airway muscles, such as muscarinic antagonists like ipratropium or tiotropium, are used in adults combined with beta-2 agonists to help improve breathing in severe acute asthma [18, 19].
Nebulized magnesium sulfate in addition to beta-2 agonists can be used in children only in cases of acute severe asthma attacks .
2) Cystic Fibrosis
Cystic fibrosis is a genetically inherited disorder that causes the buildup of very thick and viscous mucus that clogs the airways. This leads to constantly obstructed airways, chronic bacterial infections, and widening of the airways .
Nebulized dornase alfa is used to help break down mucus .
Nebulization with hypertonic salt water solution is also recommended .
Nebulization with N-acetylcysteine, which helps break down mucus, did not achieve a positive enough effect to recommend its use in cystic fibrosis patients (according to a meta-analysis) .
Opioids are reserved only for severe, end-stage cases [24, 25, 26, 27].
3) Lung Infections
The use of antibiotics through nebulization has the advantage of delivering large doses directly to the infected lungs. However, the risk of developing multi-drug resistant infections limits nebulized antibiotic therapy only to specific cases [28, 29].
Cystic Fibrosis Patients
In patients with cystic fibrosis, chronic P. aeruginosa infections are a significant problem. Use of the nebulized antibiotic tobramycin twice a day can be used, or alternatively, azithromycin or aztreonam [30, 22].
Pneumonia can be fatal for patients with a very weakened immune system, such as HIV positive patients, those with leukemia, or those who have undergone organ or stem cell transplants .
Nebulized pentamidine, a strong anti-infective drug, is used to prevent protozoa (Pneumocystis jiroveci) infections in people with compromised immunity (including transplant patients allergic to trimethoprim/sulfamethoxazole) [32, 31].
Pneumonia can also be caused by a virus, such as the respiratory syncytial virus. Nebulized ribavirin, an antiviral drug, is approved for use in patients with a compromised immune system .
The use of nebulized liposomal amphotericin B in patients who received a lung transplant to avoid infection (Aspergillus spp.) proved effective in a study of 412 patients (retrospective observational) .
Mechanically Ventilated Patients
Nebulized antibiotics (like colistin or aminoglycosides), antivirals, or antifungals are advised only if conventional (IV) therapy is not an option for mechanically ventilated patients; although, in practice, it is used in hospitals around the world [29, 35].
4) Chronic Obstructive Pulmonary Disease
Chronic Obstructive Pulmonary Disease (COPD) is a progressive condition that makes breathing difficult for the patient. Most patients have inflammation of the bronchial tubes, damage to the air sacs, and excessive production of mucus .
Nebulized furosemide, a diuretic, helped relieve difficulty in breathing in 2 double-blind randomized controlled trials of 20 and 100 COPD patients [37, 38].
Nebulized fentanyl citrate or low doses of nebulized morphine helped improve breathing during exercise in 23 patients (9 with advanced COPD) in 2 trials. However, nebulized morphine resulted in no improvement in breathing in different double-blind randomized controlled trials with COPD patients [39, 40, 41, 42, 43].
5) Acute Lung Injury
Often, bleeding disorders with increased coagulation occur after acute lung injury. Nebulization of anticoagulants, drugs that stop excessive blood clotting, can deliver the required high concentrations to the lungs .
Nebulized anticoagulants decreased coagulation and inflammation in the lungs in several animal studies (mice, rats, and sheep) [45, 46, 47].
Nebulized heparin reduced blood clotting in 2 studies on 66 mechanically ventilated patients with no serious negative effects. The treatment reduced the amount of time mechanical ventilation was needed [48, 49].
6) Breathing in Advanced Cancer Patients
The use of nebulized pain medication or a diuretic furosemide might help with shortness of breath in patients in advanced stages of cancer .
In two studies of 26 cancer patients, nebulized morphine was as effective as injected (subcutaneous) morphine in relieving breathing difficulties [51, 52].
However, a study (double-blind randomized controlled trial) of 17 patients found no benefits to nebulized morphine compared to a salt water solution, while 2 systematic reviews found no evidence of benefits either [53, 54, 55].
Nebulized furosemide has also shown mixed results [56, 57, 58, 59].
7) Insulin Application
Patients with type 1 diabetes need constant insulin injections to control their symptoms and glucose levels .
Less invasive alternatives for insulin administration are being studied. According to one meta-analysis and two studies, nebulized insulin helps patients control their glucose levels, although not clearly as effective as injected insulin [61, 62, 63].
Nevertheless, an inhaled insulin treatment was approved by the FDA but was discontinued after poor sales. Other pharmaceutical companies also halted their research on this subject. Rapid-Onset nebulized insulin is now being studied, which was effective in 13 patients with type 2 diabetes [60, 64, 65].
Nebulizer Side Effects & Precautions
Drugs can have distinct side effects and interactions in a nebulized form. Make sure to consult with your doctor and follow their instructions carefully before applying a nebulized drug, even if you’re already using the same drug via different routes.
Most of the side effects due to nebulizer use correspond to the drug being taken. However, difficulties in breathing due to contraction of the airway may occur as effects of the temperature or nature (tonicity) of the nebulized solution .
Eye irritation may occur with the use of a face mask if not worn correctly .
The risk of bacterial infection increases (S. aureus and P. aeruginosa) if the device is not cleaned correctly .
The use of facemasks should be avoided when corticosteroids are used since they can cause side effects on the skin of the face and eyes .
To avoid the contamination of the nebulizer with bacteria, the nebulizer cup, and the interface should be rinsed and dried after every use, and disinfected once or twice a week according to the manufacturer’s instructions .
Use in Infants
When a nebulizer is used in small children, crying diminishes the amount of medicine that reaches the lungs. The nebulizer should be used only when the child is calm and breathing normally [68, 11].
A study attempting to treat 30 infants (under 2 years) in their sleep found most of them woke up and refused the treatment. A special mask that incorporated the babies’ own pacifier was successfully used in 10 babies (under 12 months) to administer the medicine without waking them up [69, 70].
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Those who use nebulizers at home generally look for one that is that is silent, easy to assemble and use, and one that has adequate pressure so treatment takes a reasonable amount of time.
Patients that use nebulizers daily recommend buying also a portable nebulizer to have at school/work. Some require AA batteries while other models have rechargeable batteries. Some of the rechargeable models have a car adapter, which people who travel a lot see as a great advantage.
Frequent users also recommend to always have a spare facemask/mouthpiece and keep close control of the service life of the filters/mesh. Thorough cleaning and drying are also advised to be very important.