CLINICAL USE OF AEROSOL THERAPY IN INFECTIOUS RESPIRATORY DISEASES

Pulcini R, D’Amario G and Ambrosini G. Clinical use of aerosol therapy in infectious respiratory diseases. International Journal of Infection. 2025;9(3):78-82.

R. Pulcini¹, G. D’Amario^2* and G. Ambrosini³

¹ Center of Advanced Studies and Technology, Department of Innovative Technology in Medicine and Dentistry, University of Chieti, Chieti, Italy;
² Department of Neuroscience, Catholic University of the Sacred Heart, Rome, Italy;
³ École Polytechnique Fédérale de Lausanne, 1015, Lausanne, Switzerland.

*Correspondence to:
Giulia D’Amario, MD,
Department of Neuroscience,
Catholic University of the Sacred Heart,
Rome, Italy.
e-mail: giuliadamario@gmail.com

Received: 12 September, 2025 Accepted: 26 November, 2025

ISSN 3103-6678 [online] Copyright 2025 © by Biolife-publisher This publication and/or article is for individual use only and may not be further reproduced without written permission from the copyright holder. Unauthorized reproduction may result in financial and other penalties. Disclosure: all authors report no conflicts of interest relevant to this article.

ABSTRACT

Inhalation therapy has been used since ancient times and today the use of aerosol is a method that uses the dispersion of liquid or solid particles that can be breathed. Aerosol therapy is very common in the treatment of many respiratory diseases and it’s use is effective in treating respiratory infections, as the selected drug is injected directly into the target organ. With aerosol therapy, drugs directly reach the site of infection in the lungs through inhalation using devices such as nebulizers, which are commonly pneumatic or ultrasonic, although today new generation devices with double Venturi effect are used which allow the particles to be aerosolized much more quickly. The effect of aerosol therapy depends on how the particles are deposited and how they interact with cells and molecules in the respiratory system. In the lungs, the drug interacts with respiratory epithelial cells, bronchial smooth muscle cells, and immune cells, which absorb it through passive diffusion or transporters, modulating mucus secretion and the production of inflammatory mediators.

KEYWORDS: Aerosol therapy, respiratory disease, infection, inhalation, respiratory tract

INTRODUCTION

Inhalation therapy originated in ancient times when active or presumed active ingredients were added to boiling water and then inhaled to obtain a beneficial effect on health (1). Aerosol refers to the fine dispersion of liquid or solid particles (dispersed phase) in a gas suitable for breathing (dispersing phase). The first aerosol system of the modern era was conceived in 1978 (2). Since then, aerosol therapy has undergone considerable diffusion and has assumed scientific and therapeutic validity for the treatment of numerous pathologies, including infectious ones of the oral cavity (3).

In the treatment of respiratory diseases, the inhalation route represents the most rational method for the administration of drugs, presenting undoubted advantages. It allows a selective direct action of the drug in the target organ without having to pass through the bloodstream, achieving the same effect with a lower dosage than that required by oral or parenteral therapy, with a consequent reduced possibility of side effects (4). Additionally, aerosol therapy has a greater speed of action, is non-invasive, and allows the use of active drugs only if administered by aerosol (for example topical steroids).

Aerosol therapy is also indicated in the treatment of respiratory infections (5), with the inhalation route representing the most effective method for the administration of drugs because it allows a direct and selective action of the drug in the target organ, achieving the same effect with a lower dosage than that required by oral or parenteral therapy and thus reducing any side effects of the drugs (4).  The administration of drugs directly into the lungs through inhalation is achieved by using devices such as nebulizers, metered dose inhalers, or dry powder inhalers (6).  With this method, the drug is administered directly to the site of infection, ensuring better therapeutic efficacy and minimizing side effects on the entire organism (3).

The identification of the most suitable device for the individual patient is a crucial point for achieving the therapeutic objective and it must derive from a considered choice evaluating numerous factors (7). The multiple possibilities of choice are advantageous, but at the same time, can create doubts and uncertainties among both patients and doctors (8). Several studies have highlighted the inadequate knowledge of medical personnel regarding the use of inhalation instruments (9,10).

DISCUSSION

Aerosol therapy is a valid therapeutic method in the treatment of upper airway conditions such as rhinitis, rhinopharyngitis, rhino-tympanitis, rhino-sinusitis, and laryngotracheitis (11) (Table I). Among the respiratory diseases mentioned above, asthma plays a primary role as one of the major causes of morbidity and mortality in the world and has significantly increased in recent years (12). Numerous drugs can be administered via aerosols, such as beta-2 agonists, topical steroids, anticholinergics, chromones, antibiotics, ribavirin, and vaccines (13).

Table I. Inhalation therapy is indicated in pathologies characterized by airway obstruction and wheezing. The diseases indicated in the table are the most common ones treated by aerosol therapy.

For therapeutic purposes, for the inhaled drug to reach all areas of the respiratory tract, the inhaled particles must have a median mass diameter between 0.5 and 5 _/um (14). The median mass diameter is the diameter that divides the total mass of the aerosol into two equal parts, one of which is composed of particles with a diameter smaller than that indicated and the other with a larger diameter, referred to as the spherical particle of unit density and having the same sedimentation speed (15). Larger particles may settle at the level of the nose-oropharyngeal tract and be swallowed (6).  On the other hand, particles that are too small may not settle at the level of the lower airways and be exhaled or may carry a modest quantity of drug, which is why in this case the therapeutic efficacy will be reduced (16).

Nebulizers can be distinguished in two types: pneumatic and ultrasonic. Pneumatic nebulizers exploit the Venturi effect, in that the liquid to be nebulized is pushed by a compressed gas towards a narrow orifice called a Venturi narrow (17). The air expands and determines a negative pressure and the fragmentation of the liquid into droplets with a diameter of 15-500 _/um (7).  Only even smaller particles will be able to pass and will be inhaled thanks to the presence of a deflector placed on the orifice. The most recent instruments consist of a device with a double Venturi effect that allows the particles to be aerosolized much more quickly, reducing the delivery time and improving compliance (18).

Ultrasonic nebulizers produce the aerosol by vibrating a piezoelectric crystal (19). These vibrations of the crystal are transmitted to the drug in solution where waves are formed, and droplets fall from the crest of the waves and are released as an aerosol (20). In pneumatic nebulizers, a “whisker” stops the droplets that are too large from falling back into the reservoir and this liquid is subsequently re-nebulized (21). Nebulizers can be used both with a mask or with a mouthpiece, however the mouthpiece is preferable because it allows double the amount of drug to reach the airways.

Nebulizers can be used at any age without difficulty because they do not require a respiratory procedure other than a physiological one. The use of nebulizers is indicated in patients who have poor cooperation and in all those subjects who, due to their incapacity or because they have an acute pathology in progress (for example, asthma attack), are unable to use other devices (22).  They are also useful in cases where it is necessary to administer high doses of the drug.

Aerosol devices are machines with poor performance (23). In fact, only 10% of the nebulized product is available to the patient (output) and that only a part of this output will be pharmacologically available in relation to the type of machine used, the type of patient to be treated, and the type of drug used. There are several elements to consider when choosing a good nebulizer and among these, particularly important are the volume of the particles to be nebulized (granulometry), the age of the patient and his/her compliance, the pathology, and the cost (24).

Drug particles introduced through aerosol therapy are deposited in the respiratory tract, interacting with respiratory epithelial cells, bronchial smooth muscle cells, and immune cells. The drug is absorbed through passive diffusion or transporters, modulating mucus secretion and the production of inflammatory mediators.

The patient’s disease conditions the choice of nebulizer. Cystic fibrosis patients need devices that nebulize particles of 0.5-3 _/um to better reach the alveoli (25). The amount of drug to be put in the nebulizer vial must be at least 3 ml for the pneumatic nebulizer, and 5 ml for the ultrasonic nebulizer. Lower amounts of liquid are not effectively nebulized with an increase in osmolarity and possible paradoxical bronchoconstriction, while higher amounts lead to an increase in delivery time with excessive cooling of the nebulizer and reflex blocking of the respiratory act.

Traditional nebulizers are inefficient because they deliver the drug both in the inspiratory and expiratory phases and during the respiratory pause. To reduce drug waste during expiration, new nebulizers have been designed, some with a plastic bag that acts as a reservoir, others “improved” (enhanced) or activated (actuated) by breathing (26). Breath-enhanced nebulizers, through the open-vent system, allow an increase in output during inspiration compared to that generated during expiration, with a consequent reduction in drug loss during expiration (27). Drug loss during the expiratory phase can be eliminated if the nebuliser is activated only during the inspiratory phase, as happens with breath-actuated nebulisers. New “smart” nebulisers combine the technology of the perforated vibrating membrane with that of adaptive aerosol delivery (AAD) (28).

The most surprising and revolutionary innovation is the presence of a chip that records and transmits data via the internet, allowing the doctor to examine and monitor the patient’s performance in real-time (29). From a clinical point of view, they have numerous advantages: lower residual volume of the drug, greater precision of the dose delivered as they adapt to the patient’s breathing without wasting the drug during expiration, greater adherence to therapy thanks to the presence of a visual, sound, or vibratory signal that informs the patient of the correct and complete execution of the maneuver. These are silent, portable, and rechargeable devices that allow, through a single platform, the administration of multiple drugs. The first studies have highlighted the possible use of the AAD System for the administration of a1-antitrypsin in patients with cystic fibrosis, with an evident saving of time and high levels of compliance (30).

Prescribing the most appropriate device can significantly improve the management and prognosis of respiratory diseases such as asthma. All types of aerosol devices have advantages and disadvantages, and the choice must be evaluated on a case-by-case basis. A summary of key points to evaluate for a reasoned choice is shown in table II (Table II).

Table II. Factors to consider when choosing an inhaler.

CONCLUSIONS

Aerosol therapy is an important and evolving tool in the management of respiratory infectious diseases and plays a critical role in the treatment. It involves the administration of medication directly into the lungs via inhalation, using devices such as nebulizers. This method offers targeted and effective treatment options. Ongoing research is aimed at improving its applications and effectiveness.

Conflict of interest

The authors declare that they have no conflict of interest.

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