Aerosol Route to Administer Teicoplanin in Mechanical Ventilation: In Vitro Study, Lung Deposition and Pharmacokinetic Analyses in Pigs

Indian Guidelines on Nebulization Therapy

Inhalational therapy, today, happens to be the mainstay of treatment in obstructive airway diseases (OADs), such as asthma, chronic obstructive pulmonary disease (COPD), and is also in the present, used in a variety of other pulmonary and even non-pulmonary disorders. Hand-held inhalation devices may often be difficult to use, particularly for children, elderly, debilitated or distressed patients. Nebulization therapy emerges as a good option in these cases besides being useful in the home care, emergency room and critical care settings. With so many advancements taking place in nebulizer technology; availability of a plethora of drug formulations for its use, and the widening scope of this therapy; medical practitioners, respiratory therapists, and other health care personnel face the challenge of choosing appropriate inhalation devices and drug formulations, besides their rational application and use in different clinical situations. Adequate maintenance of nebulizer equipment including their disinfection and storage are the other relevant issues requiring guidance. Injudicious and improper use of nebulizers and their poor maintenance can sometimes lead to serious health hazards, nosocomial infections, transmission of infection, and other adverse outcomes. Thus, it is imperative to have a proper national guideline on nebulization practices to bridge the knowledge gaps amongst various health care personnel involved in this practice. It will also serve as an educational and scientific resource for healthcare professionals, as well as promote future research by identifying neglected and ignored areas in this field. Such comprehensive guidelines on this subject have not been available in the country and the only available proper international guidelines were released in 1997 which have not been updated for a noticeably long period of over two decades, though many changes and advancements have taken place in this technology in the recent past. Much of nebulization practices in the present may not be evidence-based and even some of these, the way they are currently used, may be ineffective or even harmful. Recognizing the knowledge deficit and paucity of guidelines on the usage of nebulizers in various settings such as inpatient, out-patient, emergency room, critical care, and domiciliary use in India in a wide variety of indications to standardize nebulization practices and to address many other related issues; National College of Chest Physicians (India), commissioned a National task force consisting of eminent experts in the field of Pulmonary Medicine from different backgrounds and different parts of the country to review the available evidence from the medical literature on the scientific principles and clinical practices of nebulization therapy and to formulate evidence-based guidelines on it. The guideline is based on all possible literature that could be explored with the best available evidence and incorporating expert opinions. To support the guideline with high-quality evidence, a systematic search of the electronic databases was performed to identify the relevant studies, position papers, consensus reports, and recommendations published. Rating of the level of the quality of evidence and the strength of recommendation was done using the GRADE system. Six topics were identified, each given to one group of experts comprising of advisors, chairpersons, convenor and members, and such six groups (A-F) were formed and the consensus recommendations of each group was included as a section in the guidelines (Sections I to VI). The topics included were: A. Introduction, basic principles and technical aspects of nebulization, types of equipment, their choice, use, and maintenance B. Nebulization therapy in obstructive airway diseases C. Nebulization therapy in the intensive care unit D. Use of various drugs (other than bronchodilators and inhaled corticosteroids) by nebulized route and miscellaneous uses of nebulization therapy E. Domiciliary/Home/Maintenance nebulization therapy; public & health care workers education, and F. Nebulization therapy in COVID-19 pandemic and in patients of other contagious viral respiratory infections (included later considering the crisis created due to COVID-19 pandemic). Various issues in different sections have been discussed in the form of questions, followed by point-wise evidence statements based on the existing knowledge, and recommendations have been formulated.

Inhaled bacteriophage therapy in a porcine model of pneumonia caused by Pseudomonas aeruginosa during mechanical ventilation

BACKGROUND AND PURPOSE 255: Pseudomonas aeruginosa is a main cause of ventilator-associated pneumonia (VAP) with drug-resistant bacteria. Bacteriophage therapy has experienced resurgence to compensate for the limited development of novel antibiotics. However, phage therapy is limited to a compassionate use so far, resulting from lack of adequate studies in relevant pharmacological models. We used a pig model of pneumonia caused by P. aeruginosa that recapitulates essential features of human disease to study the antimicrobial efficacy of nebulized-phage therapy.

EXPERIMENTAL APPROACH

(i) Lysis kinetic assays were performed to evaluate in vitro phage antibacterial efficacy against P. aeruginosa and select relevant combinations of lytic phages. (ii) The efficacy of the phage combinations was investigated in vivo (murine model of P. aeruginosa lung infection). (iii) We determined the optimal conditions to ensure efficient phage delivery by aerosol during mechanical ventilation. (iv) Lung antimicrobial efficacy of inhaled-phage therapy was evaluated in pigs, which were anaesthetized, mechanically ventilated and infected with P. aeruginosa.

KEY RESULTS

By selecting an active phage cocktail and optimizing aerosol delivery conditions, we were able to deliver high phage concentrations in the lungs, which resulted in a rapid and marked reduction in P. aeruginosa density (1.5-log reduction, p < .001). No infective phage was detected in the sera and urines throughout the experiment.

CONCLUSION AND IMPLICATIONS

Our findings demonstrated (i) the feasibility of delivering large amounts of active phages by nebulization during mechanical ventilation and (ii) rapid control of in situ infection by inhaled bacteriophage in an experimental model of P. aeruginosa pneumonia with high translational value.

Correlation and clinical relevance of animal models for inhaled pharmaceuticals and biopharmaceuticals

Nonclinical studies are fundamental for the development of inhaled drugs, as for any drug product, and for successful translation to clinical practice. They include in silico, in vitro, ex vivo and in vivo studies and are intended to provide a comprehensive understanding of the inhaled drug beneficial and detrimental effects. To date, animal models cannot be circumvented during drug development programs, acting as surrogates of humans to predict inhaled drug response, fate and toxicity. Herein, we review the animal models used during the different development stages of inhaled pharmaceuticals and biopharmaceuticals, highlighting their strengths and limitations.

Comparative lung distribution of radiolabeled tobramycin between nebulized and intravenous administration in a mechanically-ventilated ovine model, an observational study

BACKGROUND

Ventilator-associated pneumonia is common and is treated using nebulized antibiotics. Although adequate pulmonary biodistribution is important for antibiotic effect, there is a lack of data for both intravenous (IV) and nebulized antibiotic administration during mechanical ventilation.

OBJECTIVE

To describe the comparative pulmonary regional distribution of IV and nebulized technetium-99m-labeled tobramycin (^99mTc-tobramycin) 400 mg in a mechanically-ventilated ovine model.

METHODS

The study was performed in a mechanically-ventilated ovine model. ^99mTc-tobramycin 400 mg was obtained using a radiolabeling process. Computed tomography (CT) was performed. Ten sheep were given ^99mTc-tobramycin 400 mg via either an IV (five sheep) or nebulized (five sheep) route. Planar images (dorsal, ventral, left lateral and right lateral) were obtained using a gamma camera. Blood samples were obtained every 15 min for 1 h (4 time points) and lung, liver, both kidney, and urine samples were obtained post-mortem.

RESULTS

Ten sheep were anesthetized and mechanically ventilated. Whole-lung deposition of nebulized ^99mTc-tobramycin 400 mg was significantly lower than with IV (8.8% vs. 57.1%, P<0.001). For both administration routes, there was significantly lower deposition in upper lung zones compared with the rest of the lungs. Dorsal deposition was significantly higher with nebulized ^99mTc-tobramycin 400 mg compared with IV (68.9% vs. 58.9%, P=0.003). Lung concentrations of ^99mTc-tobramycin were higher with IV compared with nebulized administration. There were significantly higher concentrations of ^99mTc-tobramycin in blood, liver and urine with IV administration compared with nebulized.

CONCLUSIONS

Nebulization resulted in lower whole and regional lung deposition of ^99mTc-tobramycin compared with IV administration and appeared to be associated with low blood and extra-pulmonary organ concentrations.

Treatment of Pseudomonas aeruginosa Biofilm Present in Endotracheal Tubes by Poly-l-Lysine

The endotracheal tube (ETT) is an essential interface between the patient and ventilator in mechanically ventilated patients. However, a microbial biofilm is formed gradually on this tube and is associated with the development of ventilator-associated pneumonia. The bacteria present in the biofilm are more resistant to antibiotics, and current medical practices do not make it possible to eliminate. Pseudomonas aeruginosa is one of the leading pathogens that cause biofilm infections and ventilator-associated pneumonia. Poly-l-lysine (pLK) is a cationic polypeptide possessing antibacterial properties and mucolytic activity by compacting DNA. Here, we explored the antibiofilm activity of pLK to treat P. aeruginosa biofilms on ETTs while taking into consideration the necessary constraints for clinical translation in our experimental designs. First, we showed that pLK eradicates a P. aeruginosa biofilm formed in vitro on 96-well microplates. We further demonstrated that pLK alters bacterial membrane integrity, as revealed by scanning electron microscopy, and eventually eradicates biofilm formed either by reference or clinical strains of P. aeruginosa biofilms generated in vitro on ETTs. Second, we collected the ETT from patients with P. aeruginosa ventilator-associated pneumonia. We observed that a single dose of pLK is able to immediately disrupt the biofilm structure and kills more than 90% of bacteria present in the biofilm. Additionally, we did not observe any lung tolerance issue when the pLK solution was instilled into the ETT of ventilated pigs, an animal model particularly relevant to mimic invasive mechanical ventilation in humans. In conclusion, pLK appears as an innovative antibiofilm molecule, which could be applied in the ETT of mechanically ventilated patients.

Characterisation of 40 mg/ml and 100 mg/ml tobramycin formulations for aerosol therapy with adult mechanical ventilation

BACKGROUND

Preservative-free tobramycin is commonly used as aerosolized therapy for ventilator associated pneumonia. The comparative delivery profile of the formulations of two different concentrations (100 mg/ml and 40 mg/ml) is unknown. This study aims to evaluate the aerosol characteristics of these tobramycin formulations in a simulated adult mechanical ventilation model.

METHODS

Simulated adult mechanical ventilation set up and optimal settings were used in the study. Inhaled mass study was performed using bacterial/viral filters at the tip of the tracheal tube and in the expiratory limb of circuit. Laser diffractometer was used for characterising particle size distribution. The physicochemical characteristics of the formulations were described and nebulization characteristics compared using two airways, an endotracheal tube (ET) and a tracheostomy tube (TT). For each type of tube, three internal tube diameters were studied, 7 mm, 8 mm and 9 mm.

RESULTS

The lung dose was significantly higher for 100 mg/ml solution (mean 121.3 mg vs 41.3 mg). Viscosity was different (2.11cp vs 1.58cp) for 100 mg/ml vs 40 mg/ml respectively but surface tension was similar. For tobramycin 100 mg/ml vs 40 mg/ml, the volume median diameter (2.02 vs 1.9 μm) was comparable. The fine particle fraction (98.5 vs 85.4%) was higher and geometric standard deviation (1.36 vs 1.62 μm) was significantly lower for 100 mg/ml concentration. Nebulization duration was longer for 100 mg/ml solution (16.9 vs 10.1 min). The inhaled dose percent was similar (30%) but the exhaled dose was higher for 100 mg/ml solution (18.9 vs 10.4%). The differences in results were non-significant for type of tube or size except for a small but statistically significant reduction in inhaled mass with TT compared to ET (0.06%).

CONCLUSION

Aerosolized tobramycin 100 mg/ml solution delivered higher lung dose compared to tobramycin 40 mg/ml solution. Tracheal tube type or size did not influence the aerosol characteristics and delivery parameters.

Insights on animal models to investigate inhalation therapy: Relevance for biotherapeutics

Acute and chronic respiratory diseases account for major causes of illness and deaths worldwide. Recent developments of biotherapeutics opened a new era in the treatment and management of patients with respiratory diseases. When considering the delivery of therapeutics, the inhaled route offers great promises with a direct, non-invasive access to the diseased organ and has already proven efficient for several molecules. To assist in the future development of inhaled biotherapeutics, experimental models are crucial to assess lung deposition, pharmacokinetics, pharmacodynamics and safety. This review describes the animal models used in pulmonary research for aerosol drug delivery, highlighting their advantages and limitations for inhaled biologics. Overall, non-clinical species must be selected with relevant scientific arguments while taking into account their complexities and interspecies differences, to help in the development of inhaled medicines and ensure their successful transposition in the clinics.

Aerosol delivery during invasive mechanical ventilation: a systematic review

BACKGROUND

This systematic review aimed to assess inhaled drug delivery in mechanically ventilated patients or in animal models. Whole lung and regional deposition and the impact of the ventilator circuit, the artificial airways and the administration technique for aerosol delivery were analyzed.

METHODS

In vivo studies assessing lung deposition during invasive mechanical ventilation were selected based on a systematic search among four databases. Two investigators independently assessed the eligibility and the risk of bias.

RESULTS

Twenty-six clinical and ten experimental studies were included. Between 30% and 43% of nominal drug dose was lost to the circuit in ventilated patients. Whole lung deposition of up to 16% and 38% of nominal dose (proportion of drug charged in the device) were reported with nebulizers and metered-dose inhalers, respectively. A penetration index inferior to 1 observed in scintigraphic studies indicated major proximal deposition. However, substantial concentrations of antibiotics were measured in the epithelial lining fluid (887 (406-12,819) μg/mL of amikacin) of infected patients and in sub-pleural specimens (e.g., 197 μg/g of amikacin) dissected from infected piglets, suggesting a significant distal deposition. The administration technique varied among studies and may explain a degree of the variability of deposition that was observed.

CONCLUSIONS

Lung deposition was lower than 20% of nominal dose delivered with nebulizers and mostly occurred in proximal airways. Further studies are needed to link substantial concentrations of antibiotics in infected pulmonary fluids to pulmonary deposition. The administration technique with nebulizers should be improved in ventilated patients in order to ensure an efficient but safe, feasible and reproducible technique.

Atomization method for verifying size effects of inhalable particles on lung damage of mice

To explore the size effects of inhalable particles on lung damage, aqueous aerosol containing cadmium was studied as a model to design a new type of two-stage atomization device that was composed of two adjustable parts with electronic ultrasonic atomization and pneumatic atomization. The working parameters and effectiveness of this device were tested with H₂O atomization and CdCl₂ inhalation, respectively. By gravimetrically detecting the mass concentrations of PM_2.5 and PM₁₀ and analysing the particle size with a laser sensor, we confirmed the particle size distribution of the aqueous aerosol produced by the new device under different working conditions. Then, we conducted experiments in male Kunming mice that inhaled CdCl₂ to determine the size effects of inhalable particles on lung damage and to confirm the effectiveness of the device. The new device could effectively control the particle size in the aqueous aerosol. The inhaled CdCl₂ entered and injured the lungs of the mice by causing tissue damage, oxidative stress, increasing endoplasmic reticulum stress and triggering an inflammatory response, which might be related to where the particles deposited. The smaller particles in the aqueous aerosol atomized by the new two-stage atomization device deposited deeper into lung causing more damage. This device could provide a new method for animal experiments involving inhalation with water-soluble toxins.

Fundamentals of aerosol therapy in critical care

Drug dosing in critically ill patients is challenging due to the altered drug pharmacokinetics–pharmacodynamics associated with systemic therapies. For many drug therapies, there is potential to use the respiratory system as an alternative route for drug delivery. Aerosol drug delivery can provide many advantages over conventional therapy. Given that respiratory diseases are the commonest causes of critical illness, use of aerosol therapy to provide high local drug concentrations with minimal systemic side effects makes this route an attractive option. To date, limited evidence has restricted its wider application. The efficacy of aerosol drug therapy depends on drug-related factors (particle size, molecular weight), device factors, patient-related factors (airway anatomy, inhalation patterns) and mechanical ventilation-related factors (humidification, airway). This review identifies the relevant factors which require attention for optimization of aerosol drug delivery that can achieve better drug concentrations at the target sites and potentially improve clinical outcomes.