Comparison of lung tissue concentrations of nebulized ceftazidime in ventilated piglets: ultrasonic versus vibrating plate nebulizers

Internet of things based visualisation of effect of air pollution on the lungs using HEPA filters air cleaner

The impact of air quality on human health and the environment is very significant, with poor air quality being responsible for numerous deaths and environmental damage worldwide. Whereas a number of studies have been done to monitor the quality of air with help of emerging technologies, little has been done to visualize its effect on health particularly on the lungs. The study explores an approach that combines Internet of Things (IoT) technology with High Efficiency Particulate Air (HEPA) filters air cleaner to monitor and visualize the effects of air pollution on lung health, highlighting the significant damage that poor air quality causes particularly on the lungs graphically. To achieve this, a 3D display of the lungs is modelled using HEPA filters, which changes colour based on the air pollutant concentrations detected by IoT-based sensors. The collected air quality data is then transmitted to Thingspeak, a visualization platform for further analysis. It is observed that the colour of the 3D lung display changed to black over time as air pollutant concentrations increased which in our study is an indicator of unhealthy lung. The study presents an innovative approach to visualize the effects of air pollution on lung health using IoT and HEPA filters air cleaner, which could have significant implications for public health policies aimed at mitigating the harmful effects of air pollution, particularly on lung health.

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.

Aerosolized antibiotics in the treatment of hospital-acquired pneumonia/ventilator-associated pneumonia

Aerosolized antibiotics are being increasingly used to treat respiratory infections, especially those caused by drug-resistant pathogens. Their use in the treatment of hospital-acquired pneumonia and ventilator-associated pneumonia in critically ill patients is especially significant. They are also used as an efficient alternative to overcome the issues caused by systemic administration of antibiotics, including the occurrence of drug-resistant strains, drug toxicity, and insufficient drug concentration at the target site. However, the rationale for the use of aerosolized antibiotics is limited owing to their insufficient efficacy and the potential for underestimated risks of developing side effects. Despite the lack of availability of high-quality evidence, the use of aerosolized antibiotics is considered as an attractive alternative treatment approach, especially in patients with multidrug-resistant pathogens. In this review, we have discussed the effectiveness and side effects of aerosolized antibiotics as well as the latest advancements in this field and usage in the Republic of Korea.

Optimizing Antimicrobial Drug Dosing in Critically Ill Patients

A fundamental step in the successful management of sepsis and septic shock is early empiric antimicrobial therapy. However, for this to be effective, several decisions must be addressed simultaneously: (1) antimicrobial choices should be adequate, covering the most probable pathogens; (2) they should be administered in the appropriate dose, (3) by the correct route, and (4) using the correct mode of administration to achieve successful concentration at the infection site. In critically ill patients, antimicrobial dosing is a common challenge and a frequent source of errors, since these patients present deranged pharmacokinetics, namely increased volume of distribution and altered drug clearance, which either increased or decreased. Moreover, the clinical condition of these patients changes markedly over time, either improving or deteriorating. The consequent impact on drug pharmacokinetics further complicates the selection of correct drug schedules and dosing during the course of therapy. In recent years, the knowledge of pharmacokinetics and pharmacodynamics, drug dosing, therapeutic drug monitoring, and antimicrobial resistance in the critically ill patients has greatly improved, fostering strategies to optimize therapeutic efficacy and to reduce toxicity and adverse events. Nonetheless, delivering adequate and appropriate antimicrobial therapy is still a challenge, since pathogen resistance continues to rise, and new therapeutic agents remain scarce. We aim to review the available literature to assess the challenges, impact, and tools to optimize individualization of antimicrobial dosing to maximize exposure and effectiveness in critically ill patients.

Inhaled antibiotics during mechanical ventilation-why it will work

Inhaled antibiotics are a common therapy among patients suffering recurrent or chronic pulmonary infections. Their use is less frequent in acutely ill patients despite a strong theoretical rationale and growing evidence of their efficiency, safety and beneficial effect on reducing bacterial resistance emergence. Clinical trials of inhaled antibiotics have shown contradictory results among mechanically ventilated patients. The optimal nebulization setup, not always implemented in all trials, the difficulty to identify the population most likely to benefit and the testing of various therapeutic strategies such as adjunctive versus alternative to systemic antibiotics may explain the disparity in trial results. The present review first presents the reasons why inhaled antibiotics have to be developed and the benefits to be expected of inhaled anti-infectious therapy among mechanically ventilated patients. A second part develops the constraints of aerosolized therapies that one has to be aware of and the simple actions required during nebulization to ensure optimal delivery to the distal lung parenchyma. Positive and negative studies concerning inhaled antibiotics are compared to understand the discrepancies of their findings and conclusions. The last part presents current developments and perspective which will likely turn it into a fully successful therapeutic modality, and makes the link between inhaled antibiotics and inhaled anti-infectious therapy.

Adapting the Aerogen Mesh Nebulizer for Dried Aerosol Exposures Using the PreciseInhale Platform

Background: Many substances used in inhalation research are water soluble and can be administered as nebulized solutions. Typical examples are therapeutic, small-molecular agents, or macromolecules. Another category is a number of water-soluble agents used for airway diagnostics or disease modeling. Mesh nebulizers have facilitated well-controlled liquid aerosol exposures. Meanwhile, a benchtop inhalation platform, PreciseInhale, was developed for providing small-scale, well-controlled aerosol exposures in preclinical configurations. The purpose of the current research was to adapt the Aerogen mesh nebulizer to work within the PreciseInhale system for both cell culture and rodent exposures.

Methods: The wet aerosols produced with the Aerogen Pro nebulizer were dried out in an aerosol holding chamber by supplying dry carrier air, which was provided by passing the incoming ambient air through a column with silica gel. The nebulizer was installed in an aerosol holding chamber between an upstream flow-rate pneumotach and a downstream aerosol monitor. By pulsing, the nebulizer output was reduced to 1%–10% of continuous operation to better match the exposure ventilation requirements. Additional drying was obtained by mantling the holding chamber with dried paper.

Results and Conclusions: The nebulizer output was reduced to 3–30 μL/min and dried out before reaching the in vitro or in vivo exposure modules. Using solute concentrations in the range of 0.5%–2% (w/w), dried aerosols were produced with a mass median aerodynamic diameter of 1.5–2.0 μm, compared to the 4–5 μm droplets emitted by the nebulizer. Controlling the Aerogen nebulizer under a reduced output scheme within the PreciseInhale platform gave two major advantages: (i) by reducing aerosol output to better match exposure flow rates of single rodents, increased airway deposition yields were obtained in a range of 1%–10% relative to the nebulized amount of test substance and (ii) shrinking aerosol particle sizes through drying improved the peripheral lung deposition of test aerosols.

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.

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.

Nebulized antibiotics in mechanically ventilated patients: a challenge for translational research from technology to clinical care

Nebulized antibiotic therapy directly targets airways and lung parenchyma resulting in high local concentrations and potentially lower systemic toxicities. Experimental and clinical studies have provided evidence for elevated lung concentrations and rapid bacterial killing following the administration of nebulized antibiotics during mechanical ventilation. Delivery of high concentrations of antibiotics to infected lung regions is the key to achieving efficient nebulized antibiotic therapy. However, current non-standardized clinical practice, the difficulties with implementing optimal nebulization techniques and the lack of robust clinical data have limited its widespread adoption. The present review summarizes the techniques and clinical constraints for optimal delivery of nebulized antibiotics to lung parenchyma during invasive mechanical ventilation. Pulmonary pharmacokinetics and pharmacodynamics of nebulized antibiotic therapy to treat ventilator-associated pneumonia are discussed and put into perspective. Experimental and clinical pharmacokinetics and pharmacodynamics support the use of nebulized antibiotics. However, its clinical benefits compared to intravenous therapy remain to be proved. Future investigations should focus on continuous improvement of nebulization practices and techniques. Before expanding its clinical use, careful design of large phase III randomized trials implementing adequate therapeutic strategies in targeted populations is required to demonstrate the clinical effectiveness of nebulized antibiotics in terms of patient outcomes and reduction in the emergence of antibiotic resistance.

Use of nebulized antimicrobials for the treatment of respiratory infections in invasively mechanically ventilated adults: a position paper from the European Society of Clinical Microbiology and Infectious Diseases

With an established role in cystic fibrosis and bronchiectasis, nebulized antibiotics are increasingly being used to treat respiratory infections in critically ill invasively mechanically ventilated adult patients. Although there is limited evidence describing their efficacy and safety, in an era when there is a need for new strategies to enhance antibiotic effectiveness because of a shortage of new agents and increases in antibiotic resistance, the potential of nebulization of antibiotics to optimize therapy is considered of high interest, particularly in patients infected with multidrug-resistant pathogens. This Position Paper of the European Society of Clinical Microbiology and Infectious Diseases provides recommendations based on the Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology regarding the use of nebulized antibiotics in invasively mechanically ventilated adults, based on a systematic review and meta-analysis of the existing literature (last search July 2016). Overall, the panel recommends avoiding the use of nebulized antibiotics in clinical practice, due to a weak level of evidence of their efficacy and the high potential for underestimated risks of adverse events (particularly, respiratory complications). Higher-quality evidence is urgently needed to inform clinical practice. Priorities of future research are detailed in the second part of the Position Paper as guidance for researchers in this field. In particular, the panel identified an urgent need for randomized clinical trials of nebulized antibiotic therapy as part of a substitution approach to treatment of pneumonia due to multidrug-resistant pathogens.

Key considerations on nebulization of antimicrobial agents to mechanically ventilated patients

Nebulized antibiotics have an established role in patients with cystic fibrosis or bronchiectasis. Their potential benefit to treat respiratory infections in mechanically ventilated patients is receiving increasing interest. In this consensus statement of the European Society of Clinical Microbiology and Infectious Diseases, the body of evidence of the therapeutic utility of aerosolized antibiotics in mechanically ventilated patients was reviewed and resulted in the following recommendations: Vibrating-mesh nebulizers should be preferred to jet or ultrasonic nebulizers. To decrease turbulence and limit circuit and tracheobronchial deposition, we recommend: (a) the use of specifically designed respiratory circuits avoiding sharp angles and characterized by smooth inner surfaces, (b) the use of specific ventilator settings during nebulization including use of a volume controlled mode using constant inspiratory flow, tidal volume 8 mL/kg, respiratory frequency 12 to 15 bpm, inspiratory:expiratory ratio 50%, inspiratory pause 20% and positive end-expiratory pressure 5 to 10 cm H₂O and (c) the administration of a short-acting sedative agent if coordination between the patient and the ventilator is not obtained, to avoid patient's flow triggering and episodes of peak decelerating inspiratory flow. A filter should be inserted on the expiratory limb to protect the ventilator flow device and changed between each nebulization to avoid expiratory flow obstruction. A heat and moisture exchanger and/or conventional heated humidifier should be stopped during the nebulization period to avoid a massive loss of aerosolized particles through trapping and condensation. If these technical requirements are not followed, there is a high risk of treatment failure and adverse events in mechanically ventilated patients receiving nebulized antibiotics for pneumonia.

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.

Aerosol delivery with two ventilation modes during mechanical ventilation: a randomized study

BACKGROUND

Volume-controlled ventilation has been suggested to optimize lung deposition during nebulization although promoting spontaneous ventilation is targeted to avoid ventilator-induced diaphragmatic dysfunction. Comparing topographic aerosol lung deposition during volume-controlled ventilation and spontaneous ventilation in pressure support has never been performed. The aim of this study was to compare lung deposition of a radiolabeled aerosol generated with a vibrating-mesh nebulizer during invasive mechanical ventilation, with two modes: pressure support ventilation and volume-controlled ventilation.

METHODS

Seventeen postoperative neurosurgery patients without pulmonary disease were randomly ventilated in pressure support or volume-controlled ventilation. Diethylenetriaminepentaacetic acid labeled with technetium-99m (2 mCi/3 mL) was administrated using a vibrating-mesh nebulizer (Aerogen Solo(®), provided by Aerogen Ltd, Galway, Ireland) connected to the endotracheal tube. Pulmonary and extrapulmonary particles deposition was analyzed using planar scintigraphy.

RESULTS

Lung deposition was 10.5 ± 3.0 and 15.1 ± 5.0 % of the nominal dose during pressure support and volume-controlled ventilation, respectively (p < 0.05). Higher endotracheal tube and tracheal deposition was observed during pressure support ventilation (27.4 ± 6.6 vs. 20.7 ± 6.0 %, p < 0.05). A similar penetration index was observed for the right (p = 0.210) and the left lung (p = 0.211) with both ventilation modes. A high intersubject variability of lung deposition was observed with both modes regarding lung doses, aerosol penetration and distribution between the right and the left lung.

CONCLUSIONS

In the specific conditions of the study, volume-controlled ventilation was associated with higher lung deposition of nebulized particles as compared to pressure support ventilation. The clinical benefit of this effect warrants further studies. Clinical trial registration NCT01879488.

Inhaled Antibiotics for Gram-Negative Respiratory Infections

Gram-negative organisms comprise a large portion of the pathogens responsible for lower respiratory tract infections, especially those that are nosocomially acquired, and the rate of antibiotic resistance among these organisms continues to rise. Systemically administered antibiotics used to treat these infections often have poor penetration into the lung parenchyma and narrow therapeutic windows between efficacy and toxicity. The use of inhaled antibiotics allows for maximization of target site concentrations and optimization of pharmacokinetic/pharmacodynamic indices while minimizing systemic exposure and toxicity. This review is a comprehensive discussion of formulation and drug delivery aspects, in vitro and microbiological considerations, pharmacokinetics, and clinical outcomes with inhaled antibiotics as they apply to disease states other than cystic fibrosis. In reviewing the literature surrounding the use of inhaled antibiotics, we also highlight the complexities related to this route of administration and the shortcomings in the available evidence. The lack of novel anti-Gram-negative antibiotics in the developmental pipeline will encourage the innovative use of our existing agents, and the inhaled route is one that deserves to be further studied and adopted in the clinical arena.

Global survey on nebulization of antimicrobial agents in mechanically ventilated patients: a call for international guidelines

Nebulized antimicrobial agents are increasingly administered for treatment of respiratory infections in mechanically ventilated (MV) patients. A structured online questionnaire assessing the indications, dosages and recent patterns of use for nebulized antimicrobial agents in MV patients was developed. The questionnaire was distributed worldwide and completed by 192 intensive care units. The most common indications for using nebulized antimicrobial agent were ventilator-associated tracheobronchitis (VAT; 58/87), ventilator-associated pneumonia (VAP; 56/87) and management of multidrug-resistant, Gram-negative (67/87) bacilli in the respiratory tract. The most common prescribed nebulized agents were colistin methanesulfonate and sulfate (36/87, 41.3% and 24/87, 27.5%), tobramycin (32/87, 36.7%) and amikacin (23/87, 26.4%). Colistin methanesulfonate, amikacin and tobramycin daily doses for VAP were significantly higher than for VAT (p < 0.05). Combination of parenteral and nebulized antibiotics occurred in 50 (86%) of 58 prescriptions for VAP and 36 (64.2%) of 56 of prescriptions for VAT. The use of nebulized antimicrobial agents in MV patients is common. There is marked heterogeneity in clinical practice, with significantly different in use between patients with VAP and VAT. Randomized controlled clinical trials and international guidance on indications, dosing and antibiotic combinations to improve clinical outcomes are urgently required.

Influence of inspiratory flow pattern and nebulizer position on aerosol delivery with a vibrating-mesh nebulizer during invasive mechanical ventilation: an in vitro analysis

BACKGROUND

Aerosol delivery during invasive mechanical ventilation (IMV) depends on nebulizer type, placement of the nebulizer and ventilator settings. The purpose of this study was to determine the influence of two inspiratory flow patterns on amikacin delivery with a vibrating-mesh nebulizer placed at different positions on an adult lung model of IMV equipped with a proximal flow sensor (PFS).

METHODS

IMV was simulated using a ventilator connected to a lung model through an 8-mm inner-diameter endotracheal tube. The impact of a decelerating and a constant flow pattern on aerosol delivery was evaluated in volume-controlled mode (tidal volume 500 mL, 20 breaths/min, inspiratory time of 1 sec, bias flow of 10 L/min). An amikacin solution (250 mg/3 mL) was nebulized with Aeroneb Solo(®) placed at five positions on the ventilator circuit equipped with a PFS: connected to the endotracheal tube (A), to the Y-piece (B), placed at 15 cm (C) and 45 cm upstream of the Y-piece (D), and placed at 15 cm of the inspiratory outlet of the ventilator (E). The four last positions were also tested without PFS. Deposited doses of amikacin were measured using the gravimetric residual method.

RESULTS

Amikacin delivery was significantly reduced with a decelerating inspiratory flow pattern compared to a constant flow (p<0.05). With a constant inspiratory flow pattern, connecting the nebulizer to the endotracheal tube enabled similar deposited doses than these obtained when connecting the nebulizer close to the ventilator. The PFS reduced deposited doses only when the nebulizer was connected to the Y-piece with both flow patterns or placed at 15 cm of the Y-piece with a constant inspiratory flow (p<0.01).

CONCLUSIONS

Using similar tidal volume and inspiratory time, a constant flow pattern (30 L/min) delivers a higher amount of amikacin through an endotracheal tube compared to a decelerating inspiratory flow pattern (peak inspiratory flow around 60 L/min). The optimal nebulizer position depends on the inspiratory flow pattern and the presence of a PFS.

Delivering antibiotics to the lungs of patients with ventilator-associated pneumonia: an update

Ventilator-associated pneumonia is a serious hospital-acquired infection, with 20-70% crude mortality and 10-40% estimated attributable mortality. Insufficient antibiotic concentrations at the infection site when these drugs are given intravenously may lead to poor outcomes, particularly when difficult-to-treat pathogens are responsible; for example, Pseudomonas aeruginosa, extended spectrum beta lactamase-producing Gram-negative bacilli, Acinetobacter spp. and/or methicillin-resistant Staphylococcus aureus. Direct drug delivery to the infection site via aerosolization combined with intravenous administration achieves concentrations exceeding MICs of the pathogens, even those with impaired susceptibility. Experimental and recent clinical results demonstrated our markedly improved ability to deliver aerosolized antibiotics to the lung with new-generation devices, for example, vibrating-mesh nebulizers. Convincing clinical data from a large randomized trial are still lacking to support the routine administration of aerosolized antibiotics to treat ventilator-associated pneumonia, even though some small-randomized trials' observations are encouraging.

Ultrasonic nebulization platforms for pulmonary drug delivery

IMPORTANCE OF THE FIELD

Since the 1950s, ultrasonic nebulizers have played an important role in pulmonary drug delivery. As the process in which aerosol droplets are generated is independent and does not require breath-actuation, ultrasonic nebulizers, in principle, offer the potential for instantaneously fine-tuning the dose administered to the specific requirements of a patient, taking into account the patient's breathing pattern, physiological profile and disease state. Nevertheless, owing to the difficulties and limitations associated with conventional designs and technologies, ultrasonic nebulizers have never been widely adopted, and have in recent years been in a state of decline.

AREAS COVERED IN THIS REVIEW

An overview is provided on the advances in new miniature ultrasonic nebulization platforms in which large increases in lung dose efficiency have been reported.

WHAT THE READER WILL GAIN

In addition to a discussion of the underlying mechanisms governing ultrasonic nebulization, in which there appears to be widely differing views, the advantages and shortcomings of conventional ultrasonic nebulization technology are reviewed and advanced state-of-the-art technologies that have been developed recently are discussed.

TAKE HOME MESSAGE

Recent advances in ultrasonic nebulization technology demonstrate significant potential for the development of smart, portable inhalation therapy platforms for the future. Nevertheless, there remain considerable challenges that need to be addressed before such personalized delivery systems can be realized. These have to be addressed across the spectrum from fundamental physics through to in vivo device testing and dealing with the relevant regulatory framework.

Nebulized and intravenous colistin in experimental pneumonia caused by Pseudomonas aeruginosa

PURPOSE

Emergence of multidrug-resistant strains in intensive care units has renewed interest in colistin, which often remains the only available antimicrobial agent active against resistant Pseudomonas aeruginosa. The aim of this study is to compare lung tissue deposition and antibacterial efficiency between nebulized and intravenous administration of colistin in piglets with pneumonia caused by P. aeruginosa.

METHODS

In ventilated piglets, colistimethate was administered 24 h following bronchial inoculation of Pseudomonas aeruginosa (minimum inhibitory concentration of colistin = 2 microg ml(-1)) either by nebulization (8 mg kg(-1) every 12 h, n = 6) or by intravenous infusion (3.2 mg kg(-1) every 8 h, n = 6). All piglets were killed 49 h after inoculation. Colistin peak lung tissue concentrations and lung bacterial burden were assessed on multiple post mortem subpleural lung specimens.

RESULTS

Median colistin peak lung concentration following nebulization was 2.8 microg g(-1) (25-75% interquartile range = 0.8-13.7 microg g(-1)). Colistin was undetected in lung tissue following intravenous infusion. In the aerosol group, peak lung tissue concentrations were significantly greater in lung segments with mild pneumonia (median = 10.0 microg g(-1), 25-75% interquartile range = 1.8-16.1 microg g(-1)) than in lung segments with severe pneumonia (median = 1.2 microg g(-1), 25-75% interquartile range = 0.5-3.3 microg g(-1)) (p < 0.01). After 24 h of treatment, 67% of pulmonary segments had bacterial counts <10(2) cfu g(-1) following nebulization and 28% following intravenous administration (p < 0.001). In control animals, 12% of lung segments had bacterial counts <10(2) cfu g(-1) 49 h following bronchial inoculation.

CONCLUSION

Nebulized colistin provides rapid and efficient bacterial killing in ventilated piglets with inoculation pneumonia caused by Pseudomonas aeruginosa.

Pharmacokinetics and lung delivery of PDDS-aerosolized amikacin (NKTR-061) in intubated and mechanically ventilated patients with nosocomial pneumonia

Introduction

Aminoglycosides aerosolization might achieve better diffusion into the alveolar compartment than intravenous use. The objective of this multicenter study was to evaluate aerosol-delivered amikacin penetration into the alveolar epithelial lining fluid (ELF) using a new vibrating mesh nebulizer (Pulmonary Drug Delivery System (PDDS), Nektar Therapeutics), which delivers high doses to the lungs.

Methods

Nebulized amikacin (400 mg bid) was delivered to the lungs of 28 mechanically ventilated patients with Gram-negative VAP for 7-14 days, adjunctive to intravenous therapy. On treatment day 3, 30 minutes after completing aerosol delivery, all the patients underwent bronchoalveolar lavage in the infection-involved area and the ELF amikacin concentration was determined. The same day, urine and serum amikacin concentrations were determined at different time points.

Results

Median (range) ELF amikacin and maximum serum amikacin concentrations were 976.1 (135.7-16127.6) and 0.9 (0.62-1.73) μg/mL, respectively. The median total amount of amikacin excreted in urine during the first and second 12-hour collection on day 3 were 19 (12.21-28) and 21.2 (14.1-29.98) μg, respectively. During the study period, daily through amikacin measurements were below the level of nephrotoxicity. Sixty-four unexpected adverse events were reported, among which 2 were deemed possibly due to nebulized amikacin: one episode of worsening renal failure, and one episode of bronchospasm.

Conclusions

PDDS delivery of aerosolized amikacin achieved very high aminoglycoside concentrations in ELF from radiography-controlled infection-involved zones, while maintaining safe serum amikacin concentrations. The ELF concentrations always exceeded the amikacin minimum inhibitory concentrations for Gram-negative microorganisms usually responsible for these pneumonias. The clinical impact of amikacin delivery with this system remains to be determined.

Trial Registration

ClinicalTrials.gov Identifier: NCT01021436.

Nebulized ceftazidime in experimental pneumonia caused by partially resistant Pseudomonas aeruginosa

PURPOSE

Ventilator-associated pneumonia caused by Pseudomonas aeruginosa with impaired sensitivity to ceftazidime is frequent in critically ill patients. The aim of the study was to compare lung tissue deposition and antibacterial efficiency between nebulized and intravenous administrations of ceftazidime in ventilated piglets with pneumonia caused by Pseudomonas aeruginosa with impaired sensitivity to ceftazidime.

METHODS

Ceftazidime was administered 24 h following the intra-bronchial inoculation of Pseudomonas aeruginosa (minimum inhibitory concentration = 16 microg ml(-1)), either by nebulization (25 mg kg(-1) every 3 h, n = 6) or by continuous intravenous infusion (90 mg kg(-1) over 24 h after an initial rapid infusion of 30 mg kg(-1), n = 6). Four non-treated inoculated animals served as controls. All piglets were killed 48 h (intravenous and control groups) or 51 h (aerosol group) after inoculation. Lung tissue concentrations and lung bacterial burden were assessed on multiple post-mortem sub-pleural lung specimens [(lower limit of quantitation = 10(2) colony forming unit (cfu g(-1))].

RESULTS

Ceftazidime trough lung tissue concentrations following nebulization were greater than steady-state lung tissue concentrations following continuous intravenous infusion [median and interquartile range, 24.8 (12.6-59.6) microg g(-1) vs. 6.1 (4.6-10.8) microg g(-1)] (p < 0.001). After 24 h of ceftazidime administration, 83% of pulmonary segments had bacterial counts <10(2) cfu g(-1) following nebulization and only 30% following intravenous administration (p < 0.001). In control animals, 10% of lung segments had bacterial counts <10(2) cfu g(-1) 48 h following bronchial inoculation.

CONCLUSION

Nebulized ceftazidime provides more efficient bacterial killing in ventilated piglets with pneumonia caused by Pseudomonas aeruginosa with impaired sensitivity to ceftazidime.

Aerosolized antibiotics to treat ventilator-associated pneumonia

PURPOSE OF REVIEW

This review summarizes the recent data on antibiotic aerosolization to treat ventilator-associated pneumonia.

RECENT FINDINGS

Most studies on antibiotic aerosolization have been case reports or descriptive studies. The results of a recent randomized, placebo-controlled trial indicated that adjunctive use of nebulized antibiotic with intravenous antibiotics to treat purulent tracheobronchitis was associated with a better outcome than placebo aerosolization. A randomized study, so far published only as an abstract, showed that amikacin aerosolized with a vibrating-mesh nebulizer--a new-generation device--was well distributed in the lung parenchyma and might lead to less intravenous antibiotic use. Several thorough reviews on nebulization devices, techniques and drawbacks have been published recently.

SUMMARY

Despite recent promising findings, the widespread use of aerosolized antibiotics to treat ventilator-associated pneumonia cannot be recommended. It should be restricted to the treatment of multidrug-resistant Gram-negative ventilator-associated pneumonia.