In medicine, a nebulizer (American English) or nebuliser (British English)is a drug delivery device used to administer medication in the form of a mist inhaled into the lungs. Nebulizers are commonly used for the treatment of asthma, cystic fibrosis, COPD and other respiratory diseases or disorders. They use oxygen, compressed air or ultrasonic power to break up solutions and suspensions into small aerosol droplets that can be directly inhaled from the mouthpiece of the device. An aerosol is a mixture of gas and solid or liquid particles.

Medical uses

Another form of nebulization

Guidelines

Various asthma guidelines, such as the Global Initiative for Asthma Guidelines [GINA], the British Guidelines on the management of Asthma, The Canadian Pediatric Asthma Consensus Guidelines, and United States Guidelines for Diagnosis and Treatment of Asthma each recommend metered dose inhalers in place of nebulizer-delivered therapies. The European Respiratory Society acknowledge that although nebulizers are used in hospitals and at home they suggest much of this use may not be evidence-based.

Effectiveness

Recent evidence shows that nebulizers are no more effective than metered-dose inhalers (MDIs) with spacers.An MDI with a spacer may offer advantages to children who have acute asthma. Those findings refer specifically to the treatment of asthma and not to the efficacy of nebulisers generally, as for COPD for example.For COPD, especially when assessing exacerbations or lung attacks, there is no evidence to indicate that MDI (with a spacer) delivered medicine is more effective than administration of the same medicine with a nebulizer.The European Respiratory Society highlighted a risk relating to droplet size reproducibility caused by selling nebulizer devices separately from nebulized solution. They found this practice could vary droplet size 10-fold or more by changing from an inefficient nebulizer system to a highly efficient one.Two advantages attributed to nebulizers, compared to MDIs with spacers (inhalers), were their ability to deliver larger dosages at a faster rate, especially in acute asthma; however, recent data suggests actual lung deposition rates are the same. In addition, another trial found that a MDI (with spacer) had a lower required dose for clinical result compared to a nebulizer (see Clark, et al. other references).Beyond use in chronic lung disease, nebulizers may also be used to treat acute issues like the inhalation of toxic substances. One such example is the treatment of inhalation of toxic hydrofluoric acid (HF) vapors. Calcium gluconate is a first-line treatment for HF exposure to the skin. By using a nebulizer, calcium gluconate can be delivered to the lungs as an aerosol to counteract the toxicity of inhaled HF vapors.

Aerosol deposition

The lung deposition characteristics and efficacy of an aerosol depend largely on the particle or droplet size. Generally, the smaller the particle the greater its chance of peripheral penetration and retention. However, for very fine particles below 0.5 μm in diameter there is a chance of avoiding deposition altogether and being exhaled. In 1966 the Task Group on Lung Dynamics, concerned mainly with the hazards of inhalation of environmental toxins, proposed a model for deposition of particles in the lung. This suggested that particles of more than 10 μm in diameter are most likely to deposit in the mouth and throat, for those of 5–10 μm diameter a transition from mouth to airway deposition occurs, and particles smaller than 5 μm in diameter deposit more frequently in the lower airways and are appropriate for pharmaceutical aerosols.

Types of nebulizers

A modern jet nebulizer

A vial of 0.5% albuterol sulfate inhalation solution for nebulizing Pneumatic Jet nebulizer The most commonly used nebulizers are jet nebulizers, which are also called “atomizers”.[10] Jet nebulizers are connected by tubing to a supply of compressed gas, usually compressed air or oxygen to flow at high velocity through a liquid medicine to turn it into an aerosol, which is then inhaled by the patient. Currently there seems to be a tendency among physicians to prefer prescription of a pressurized Metered Dose Inhaler (pMDI) for their patients, instead of a jet nebulizer that generates a lot more noise (often 60 dB during use) and is less portable due to a greater weight. However, jet nebulizers are commonly used for patients in hospitals who have difficulty using inhalers, such as in serious cases of respiratory disease, or severe asthma attacks. The main advantage of the jet nebulizer is related to its low operational cost. If the patient needs to inhale medicine on a daily basis the use of a pMDI can be rather expensive. Today several manufacturers have also managed to lower the weight of the jet nebulizer down to 635 grams (22.4 oz), and thereby started to label it as a portable device. Compared to all the competing inhalers and nebulizers, the noise and heavy weight is however still the biggest draw back of the jet nebulizer. Trade names for jet nebulizers include Maxin.Soft mist inhaler The medical company Boehringer Ingelheim also invented a new device named Respimat Soft Mist Inhaler in 1997. This new technology provides a metered dose to the user, as the liquid bottom of the inhaler is rotated clockwise 180 degrees by hand, adding a build up tension into a spring around the flexible liquid container. When the user activates the bottom of the inhaler, the energy from the spring is released and imposes pressure on the flexible liquid container, causing liquid to spray out of 2 nozzles, thus forming a soft mist to be inhaled. The device features no gas propellant and no need for battery/power to operate. The average droplet size in the mist was measured to 5.8 micrometers, which could indicate some potential efficiency problems for the inhaled medicine to reach the lungs. Subsequent trials have proven this was not the case. Due to the very low velocity of the mist, the Soft Mist Inhaler in fact has a higher efficiency compared to a conventional pMDI. In 2000, arguments were launched towards the European Respiratory Society (ERS) to clarify/expand their definition of a nebulizer, as the new Soft Mist Inhaler in technical terms both could be classified as a “hand driven nebulizer” and a “hand driven pMDI”.Electrical Ultrasonic wave nebulizer Ultrasonic wave nebulizers were invented in 1965 as a new type of portable nebulizer. The technology inside an ultrasonic wave nebulizer is to have an electronic oscillator generate a high frequency ultrasonic wave, which causes the mechanical vibration of a piezoelectric element. This vibrating element is in contact with a liquid reservoir and its high frequency vibration is sufficient to produce a vapor mist.As they create aerosols from ultrasonic vibration instead of using a heavy air compressor, they only have a weight around 170 grams (6.0 oz). Another advantage is that the ultrasonic vibration is almost silent. Examples of these more modern type of nebulizers are: Omron NE-U17 and Beurer Nebulizer IH30.Vibrating mesh technology A new significant innovation was made in the nebulizer market around 2005, with creation of the ultrasonic Vibrating Mesh Technology (VMT). With this technology a mesh/membrane with 1000–7000 laser drilled holes vibrates at the top of the liquid reservoir, and thereby pressures out a mist of very fine droplets through the holes. This technology is more efficient than having a vibrating piezoelectric element at the bottom of the liquid reservoir, and thereby shorter treatment times are also achieved. The old problems found with the ultrasonic wave nebulizer, having too much liquid waste and undesired heating of the medical liquid, have also been solved by the new vibrating mesh nebulizers. Available VMT nebulizers include: Pari eFlow, Respironics i-Neb,Beurer Nebulizer IH50, and Aerogen Aeroneb. As the price of the ultrasonic VMT nebulizers is higher than models using previous technologies, most manufacturers continue to also sell the classic jet nebulizers.

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