Factors affecting bronchodilator delivery in mechanically ventilated adults

Aerosol drug therapy in critically ill patients (Aero-in-ICU study): A multicentre prospective observational cohort study

BACKGROUND

In recent years, a significant understanding of delivering optimal aerosol therapy and the availability of various drugs and devices have led to an increase in its use in clinical practice. There are only a few studies available regarding their use in critically ill patients from a few parts of the world. We aimed to study the practice pattern of aerosol therapy in critically ill patients from Indian intensive care units (ICUs).

METHODS

After ethical approval, this multi-centric prospective observational study was performed over a study period of four weeks. Newly admitted adult patients considered who had an artificial airway and/or ventilation (including non-invasive). Patients were followed up for the next 14 days or until ICU discharge/death (whichever came first) for details of each aerosol therapy, including ongoing respiratory support, drug type, and aerosol-generating device.

RESULTS

From the nine participating centers across India, 218 patients were enrolled. Of 218 enrolled patients, 72.48% received 4884 aerosols with 30.91 ± 27.15 (95%CI: 26.6-35.1) aerosols per patient over 1108 patient days. Approximately 62.7% during IMV, 30.2% during NIV, 2.3% in spontaneously breathing patients with an artificial airway during weaning, and 4.7% were given without an artificial airway after weaning or decannulation. In 59%, a single drug was used, and bronchodilators were the most frequent. The jet nebulizer was the most common, followed by the ultrasonic and vibrating mesh aerosol generator. The ventilator setting was changed in only 6.6% of the aerosol sessions with IMV and none with NIV.

CONCLUSION

Aerosol therapy is frequently used with a wide variation in practices; bronchodilators are the most commonly used drugs, and jet nebulizers are the most widely used.

The effect of budesonide delivered by high-frequency oscillatory ventilation on acute inflammatory response in severe lung injury in adult rabbits

The inflammation present in acute respiratory distress syndrome (ARDS) and thereby associated injury to the alveolar-capillary membrane and pulmonary surfactant can potentiate respiratory failure. Even considering the high mortality rate of severe ARDS, glucocorticoids appear to be a reasonable treatment option along with an appropriate route of delivery to the distal lung. This study aimed to investigate the effect of budesonide therapy delivered intratracheally by high-frequency oscillatory ventilation (HFOV) on lung function and inflammation in severe ARDS. Adult New Zealand rabbits with respiratory failure (P/F<13.3 kPa) induced by intratracheal instillation of hydrochloric acid (HCl, 3 ml/kg, pH 1.5) followed by high tidal ventilation (VT 20 ml/kg) to mimic ventilator-induced lung injury (VILI) were treated with intratracheal bolus of budesonide (0.25 mg/kg, Pulmicort) delivered by HFOV (frequency 8 Hz, MAP 1 kPa, deltaP 0.9 kPa). Saline instead of HCl without VILI with HFOV delivered air bolus instead of therapy served as healthy control. All animals were subjected to lung-protective ventilation for 4 h, and respiratory parameters were monitored regularly. Postmortem, lung injury, wet-to-dry weight ratio, leukocyte shifts, and levels of cytokines in plasma and lung were evaluated. Budesonide therapy improved the lung function (P/F ratio, oxygenation index, and compliance), decreased the cytokine levels, reduced lung edema and neutrophils influx into the lung, and improved lung architecture in interstitial congestion, hyaline membrane, and atelectasis formation compared to untreated animals. This study indicates that HFOV delivered budesonide effectively ameliorated respiratory function, and attenuated acid-induced lung injury in a rabbit model of severe ARDS.

Impact of gas humidification and nebulizer position under invasive ventilation: preclinical comparative study of regional aerosol deposition

Successful aerosol therapy in mechanically ventilated patients depends on multiple factors. Among these, position of nebulizer in ventilator circuit and humidification of inhaled gases can strongly influence the amount of drug deposited in airways. Indeed, the main objective was to preclinically evaluate impact of gas humidification and nebulizer position during invasive mechanical ventilation on whole lung and regional aerosol deposition and losses. Ex vivo porcine respiratory tracts were ventilated in controlled volumetric mode. Two conditions of relative humidity and temperature of inhaled gases were investigated. For each condition, four different positions of vibrating mesh nebulizer were studied: (i) next to the ventilator, (ii) right before humidifier, (iii) 15 cm to the Y-piece adapter and (iv) right after the Y-piece. Aerosol size distribution were calculated using cascade impactor. Nebulized dose, lung regional deposition and losses were assessed by scintigraphy using 99mtechnetium-labeled diethylene-triamine-penta-acetic acid. Mean nebulized dose was 95% ± 6%. For dry conditions, the mean respiratory tract deposited fractions reached 18% (± 4%) next to ventilator and 53% (± 4%) for proximal position. For humidified conditions, it reached 25% (± 3%) prior humidifier, 57% (± 8%) before Y-piece and 43% (± 11%) after this latter. Optimal nebulizer position is proximal before the Y-piece adapter showing a more than two-fold higher lung dose than positions next to the ventilator. Dry conditions are more likely to cause peripheral deposition of aerosols in the lungs. But gas humidification appears hard to interrupt efficiently and safely in clinical use. Considering the impact of optimized positioning, this study argues to maintain humidification.

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.

Quantifying Delivered Dose with Jet and Mesh Nebulizers during Spontaneous Breathing, Noninvasive Ventilation, and Mechanical Ventilation in a Simulated Pediatric Lung Model with Exhaled Humidity

Acutely ill children may transition between spontaneous breathing (SB), noninvasive ventilation (NIV), and mechanical ventilation (MV), and commonly receive the same drug dosage with each type of ventilatory support and interface. This study aims to determine the aerosol deposition with jet (JN) and mesh nebulizers (MN) during SB, NIV, and MV using a pediatric lung model. Drug delivery with JN (Mistymax10) and MN (Aerogen Solo) was compared during SB, NIV, and MV using three different lung models set to simulate the same breathing parameters (Vt 250 mL, RR 20 bpm, I:E ratio 1:3). A heated humidifier was placed between the filter and test lung to simulate exhaled humidity (35 ± 2 °C, 100% RH) with all lung models. Albuterol sulfate (2.5 mg/3 mL) was delivered, and the drug deposited on an absolute filter was eluted and analyzed with spectrophotometry. Aerosol delivery with JN was not significantly different during MV, NIV, and SB (p = 0.075), while inhaled dose obtained with MN during MV was greater than NIV and SB (p = 0.001). The delivery efficiency of MN was up to 3-fold more than JN during MV (p = 0.008), NIV (p = 0.005), and SB (p = 0.009). Delivered dose with JN was similar during MV, NIV, and SB, although the delivery efficiency of MN differs with different modes of ventilation.

A Review: The Prospect of Inhaled Insulin Therapy via Vibrating Mesh Technology to Treat Diabetes

Background: Inhaled insulin has proven to be viable and, in some aspects, a more effective alternative to subcutaneous insulin. Past and present insulin inhaler devices have not found clinical or commercial success. Insulin inhalers create a dry powder or soft mist insulin aerosol, which does not provide the required uniform particle size or aerosol volume for deep lung deposition. Methods: The primary focus of this review is to investigate the potential treatment of diabetes with a wet insulin aerosol. Vibrating mesh nebulisers allow the passive inhalation of a fine wet mist aerosol for the administration of drugs to the pulmonary system in higher volumes than other small-volume nebulisers. Results: At present, there is a significant focus on vibrating mesh nebulisers from the pharmaceutical and biomedical industries for the systemic administration of pharmaceuticals for non-traditional applications such as vaccines or the treatment of diabetes. Systemic drug administration using vibrating mesh nebulisers leads to faster-acting pharmaceuticals with a reduction in drug latency. Conclusions: Systemic conditions such as diabetes, require the innovative development of custom vibrating mesh devices to provide the desired flow rates and droplet size for effective inhaled insulin administration.

Recent advances in aerosol devices for the delivery of inhaled medications

Introduction: Aerosolized medications are commonly prescribed for the treatment of patients with pulmonary diseases, and there has been an increased interest in the development of aerosol delivery devices over the years. Technical innovations have advanced device design, novel features such as breath actuation, dose tracking, portability, and feedback mechanism during treatment that improved the performance of aerosol devices, and effectiveness of inhalation therapy.Areas covered: The purpose of this paper is to review recent advances in aerosol devices for delivery of inhaled medications.Expert opinion: Drug formulations and device designs are rapidly evolving to make more consistent dosing across a broad range of inspiratory efforts, to maximize dose and target specific areas of the diseased lung.

Vibrating Mesh Nebulisers – Can Greater Drug Delivery to the Airways and Lungs Improve Respiratory Outcomes?

Aerosols are an increasingly important mode of delivery of drugs, particularly bronchodilators, for the treatment of respiratory diseases, notably asthma and chronic obstructive pulmonary disease. The most common type of nebuliser is the jet nebuliser (JN); they have been in use for more than a century but these devices can be cumbersome to use and may sometimes deliver insufficient amounts of drug. A more recent development in aerosol therapy is the vibrating mesh nebuliser (VMN) which is very user friendly and is more efficient than the JNs due to an extremely low residual volume. Scintigraphy images from studies of volunteer subjects using radio-labelled aerosol treatment show that VMN-generated aerosols deliver more drug to patients in a shorter period of time than JN-generated aerosols. Various bench, animal model and small clinical studies have shown that VMNs are more efficient than JNs in drug delivery, potentially improving clinical outcomes. These studies have included various breathing circuits used in mechanical ventilation (MV), non-invasive ventilation, high-flow nasal cannula systems and devices for spontaneously breathing patients. The efficiency of drug delivery was affected by factors including the position of the nebuliser in the circuit and humidity. Some studies have shown potential substantial savings by hospitals in the cost of MV treatments after switching from metered dose inhalers to VMNs. VMNs have also been shown to be effective for the administration of inhaled antibiotics, corticosteroids and other drugs. Larger studies of the effects of VMNs on patient outcomes are needed but they are likely to be an increasingly important means of administering therapies to a burgeoning population with respiratory disease.

Aerosol delivery during spontaneous breathing with different types of nebulizers- in vitro/ex vivo models evaluation

BACKGROUND

Nebulizers for spontaneous breathing have been evaluated through different study designs. There are limitations in simulated bench models related to patient and nebulizer factors. The aim of this study was to determine the correlation of inhaled drug mass between in vitro and ex vivo studies by testing aerosol deposition of various types of nebulizers.

METHODS

Ten healthy subjects were recruited to receive aerosol therapy with five nebulizers in random order: 1) a jet nebulizer (JN); 2) a breath-enhanced nebulizer (BEN); 3) a manually triggered nebulizer (MTN), 4) a breath-actuated nebulizer (BAN), and 5) a vibrating mesh nebulizer (VMN) with valved-adapter. A unit dose of salbutamol containing 5 mg in 2.5 mL was placed into the nebulizer and administered for 10 min. For the ex vivo study, minute ventilation of healthy subjects was recorded for 1 min. For the in vitro study a breathing simulator was utilized with adult breathing patterns. Aerosolized drug from the nebulizers and the accessory tubes was captured using inspiratory and expiratory collecting filters. Captured drug was eluted, measured and expressed as inhaled and exhaled mass using spectrophotometry at a wavelength of 276 nm.

RESULTS

10 healthy subjects were recruited, aged 20.8 ± 0.7 years old, with a mean height of 166.2 ± 9.2 cm and weight of 64.7 ± 12.4 kg. There was no significant difference in the inhaled drug dose between the JN and BEN (15.0 ± 1.94% and 17.74 ± 2.65%, respectively, p = .763), yet the inhaled doses were lower than the other three nebulizers (p < .001). The VMN delivered greater inhaled dose than the other four nebulizers (p < .01). The respiratory rate of the cohorts was significantly correlated with the inhaled drug dose. For the in vitro model, the JN delivered a lower inhaled dose (11.6 ± 1.6, p < .001) than the other nebulizers, whereas the MTN and BAN deposited significantly lower exhaled doses (1.7 ± 0.4 and 2.7 ± 0.2, respectively, p < .001). The VMN demonstrated a greater drug dose with the in vitro study than the ex vivo model (44.0 ± 0.9% and 35.5 ± 6.3% respectively, p = .003), whereas the JN in the ex vivo model resulted in a greater inhaled drug dose (15.0 ± 1.9% for ex vivo vs 11.6 ± 1.6% for in vitro, p = .008).

CONCLUSIONS

These in vitro/ex vivo model comparisons of nebulizers performance indicated that breath-related nebulizers can be estimated using an in vitro model; however, the JN and VMN delivered inhaled drug mass differed between models. There was a significant correlation between respiratory rate and inhaled mass, and the inhaled drug dose generated by VMN correlated with minute ventilation. This study demonstrated that the VMN produced greater inhaled drug dose and lowest residual dose, whereas the BEN, BAN, and MTN produced lower exhaled drug dose in both in vitro and ex vivo models.

In vitro evaluation of aerosol delivery of aztreonam lysine (AZLI): an adult mechanical ventilation model

BACKGROUND

The delivery profile of Aztreonam lysine (AZLI) during mechanical ventilation (MV) is unknown. We evaluated the amount of AZLI drug delivered using an in vitro model of adult MV.

METHODS

An adult lung model designed to mimic current clinical practice was used. Both nebulizers were placed before a Y-piece and 4 settings were tested: A) Aeroneb solo® [AS] with a t-piece; B) AS with the spacer; C) M-Neb® [MN] with a t-piece and D) MN with the spacer. Performance was evaluated in terms of: 1) Mass median aerodynamic diameter (MMAD); 2) Geometric standard deviation (GSD), 3) Fine particle dose (FPD), 4) Fine particle fraction (FPF), 5) Inhalable mass (IM), and 6) Recovery rate (RR).

RESULTS

Both devices showed an adequate delivery of AZLI during MV, with MMAD between 2.4-2.5 µm and 87% of FPF. The FPD (38.8 and 31.7), IM (44.8 and 36.1) and RR (30 and 24) were similar for AS and MN respectively. Nebulizer aerosol delivery increased (50 and 70% respectively) for both nebulizers when using the spacer.

CONCLUSION

Both AS and MN showed a good aerosol delivery profile for AZLI during in vitro mechanical ventilation. Better aerosol delivery performance was obtained using the spacer.

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.

Pulmonary Drug Delivery Following Continuous Vibrating Mesh Nebulization and Inspiratory Synchronized Vibrating Mesh Nebulization During Noninvasive Ventilation in Healthy Volunteers

BACKGROUND

A breath-synchronized nebulization option that could potentially improve drug delivery during noninvasive positive pressure ventilation (NIPPV) is currently not available on single-limb circuit bilevel ventilators. The aim of this study was to compare urinary excretion of amikacin following aerosol delivery with a vibrating mesh nebulizer coupled to a single-limb circuit bilevel ventilator, using conventional continuous (Conti-Neb) and experimental inspiratory synchronized (Inspi-Neb) nebulization modes.

MATERIALS AND METHODS

A crossover clinical trial involving 6 noninvasive ventilated healthy volunteers (mean age of 32.3 ± 9.5 y) randomly assigned to both vibrating mesh nebulization modes was conducted: Inspi-Neb delivered aerosol during only the whole inspiratory phase, whereas Conti-Neb delivered aerosol continuously. All subjects inhaled amikacin solution (500 mg/4 mL) during NIPPV using a single-limb bilevel ventilator (inspiratory positive airway pressure: 12 cm H₂O, and expiratory positive airway pressure: 5 cm H₂O). Pulmonary drug delivery of amikacin following both nebulization modes was compared by urinary excretion of drug for 24 hours post-inhalation.

RESULTS

The total daily amount of amikacin excreted in the urine was significantly higher with Inspi-Neb (median: 44.72 mg; interquartile range [IQR]: 40.50-65.13) than with Conti-Neb (median: 40.07 mg; IQR: 31.00-43.73), (p = 0.02). The elimination rate constant of amikacin (indirect measure of the depth of drug penetration into the lungs) was significantly higher with Inspi-Neb (median: 0.137; IQR: 0.113-0.146) than with Conti-Neb (median: 0.116; IQR: 0.105-0.130), (p = 0.02). However, the mean pulmonary drug delivery rate, expressed as the ratio between total daily urinary amount of amikacin and nebulization time, was significantly higher with Conti-Neb (2.03 mg/min) than with Inspi-Neb (1.09 mg/min) (p < 0.01).

CONCLUSIONS

During NIPPV with a single-limb circuit bilevel ventilator, the use of inspiratory synchronized vibrating mesh nebulization may improve pulmonary drug delivery compared with conventional continuous vibrating mesh nebulization.

A Novel In-Line Delivery System to Administer Dry Powder Mannitol to Mechanically Ventilated Patients

BACKGROUND

Mechanically ventilated patients commonly suffer from ventilator-associated pneumonia, hypoxemia, and other lower respiratory tract infection as a result of pathogen colonization and poor sputum clearance. Consequently, there is a high rate of morbidity and mortality in these patients. Dry powder mannitol increases sputum clearance, and therefore, we developed a system to administer it to mechanically ventilated patients without disconnection from the ventilator.

METHODS

The inspiratory line from a ventilator was split by using a three-way valve into two parallel lines where one contains a humidifier for normal breathing cycle and the other line contains a dry powder inhaler (Osmohaler™). The inspiratory air went through the dry powder line and aerosolized the mannitol powder only when its administration to a patient is required. We determined the delivered dose and particle size distributions of emitted aerosols in vitro from 9.5 mm endotracheal and 7.5 mm tracheostomy tubes, with inspiratory airflow of 60, 70, and 80 L/min.

RESULTS

This novel setup was able to deliver 24.6% ± 3.33% of the 160 mg loaded dose mannitol powder (4 × 40 mg capsules) and 26.7% ± 2.19% of the 320 mg dose (4 × 80 mg capsules) when the endotracheal tube was used. With the shorter tracheostomy tube, the delivery dose increased to 35.6% ± 3.01% and 39.5% ± 2.04% of the 160 and 320 mg doses, respectively. The volume median diameters of the aerosols were in the respirable range with the largest value being 5.17 ± 0.87 μm.

CONCLUSIONS

This delivery system has been shown to consistently deliver a high respirable dose of mannitol powder. Since this setup does not require disconnection of patients from the ventilator, it is safer for hypoxemic patients and easier to be adapted in a real clinical use.

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.

In Vitro Comparison of a Vibrating Mesh Nebulizer Operating in Inspiratory Synchronized and Continuous Nebulization Modes During Noninvasive Ventilation

Backround: Coupling nebulization with noninvasive ventilation (NIV) has been shown to be effective in patients with respiratory diseases. However, a breath-synchronized nebulization option that could potentially improve drug delivery by limiting drug loss during exhalation is currently not available on bilevel ventilators. The aim of this in vitro study was to compare aerosol delivery of amikacin with a vibrating mesh nebulizer coupled to a single-limb circuit bilevel ventilator, using conventional continuous (Conti-Neb) and experimental inspiratory synchronized (Inspi-Neb) nebulization modes.

METHODS

Using an adult lung bench model of NIV, we tested a vibrating mesh device coupled with a bilevel ventilator in both nebulization modes. Inspi-Neb delivered aerosol only during the whole inspiratory phase, whereas Conti-Neb delivered aerosol continuously. The nebulizer was charged with amikacin solution (250 mg/3 mL) and placed at two different positions: between the lung and exhalation port and between the ventilator and exhalation port. Inhaled, expiratory wasted and circuit lost doses were assessed by residual gravimetric method. Particle size distribution of aerosol delivered at the outlet of the ventilator circuit during both nebulization modes was measured by laser diffraction method.

RESULTS

Regardless of the nebulizer position, Inspi-Neb produced higher inhaled dose (p < 0.01; +6.3% to +16.8% of the nominal dose), lower expiratory wasted dose (p < 0.05; -2.7% to -42.6% of the nominal dose), and greater respirable dose (p < 0.01; +8.4% to +15.2% of the nominal dose) than Conti-Neb. The highest respirable dose was found with the nebulizer placed between the lung and exhalation port (48.7% ± 0.3% of the nominal dose).

CONCLUSIONS

During simulated NIV with a single-limb circuit bilevel ventilator, the use of inspiratory synchronized vibrating mesh nebulization improves respirable dose and reduces drug loss of amikacin compared with continuous vibrating mesh nebulization.

Influence of Tracheostomy on Lung Deposition in Spontaneously Breathing Patients

BACKGROUND

Nebulized drugs are frequently administrated through tracheostomy in clinical routine. So far, the amount of drug deposited into the lung in these patients remains unknown. The aim of our pharmacokinetic study was to compare lung delivery of amikacin in the same subjects in two settings: spontaneously breathing through a tracheostomy and through the mouth.

METHODS

Lung delivery was measured by amikacin urinary drug concentration in nine patients who were transitory tracheostomized for the need of a head and neck oncologic surgery. Patients performed two nebulization sessions: with a mouthpiece (MB) and through tracheostomy (TB) using a adapted jet nebulizer (Sidestream^®).

RESULTS AND CONCLUSION

Lung delivery was similar with the two conditions of nebulization (6.5 ± 2.5% vs. 6.3 ± 2.0% of the nominal mass of amikacin, respectively, for MB and TB; p = 0.95). Duration of nebulization was also comparable (19.7 ± 1.6 vs. 20.1 ± 1.8 min, respectively, for mouth and tracheostomy breathing; p = 0.307). The half-life and elimination rate constant were not different between the two settings. We conclude that nebulized therapy can be administered in spontaneously breathing tracheostomized adults patients, with a similar amount of drug delivered to the lung compared with spontaneously mouth breathing patients.

In vitro comparison of five nebulizers during noninvasive ventilation: analysis of inhaled and lost doses

BACKGROUND

Few studies on performance comparison of nebulizer systems coupled with a single-limb circuit bilevel ventilator are available. Most of these data compared the aerosol drug delivery for only two different systems. Using an adult lung bench model of noninvasive ventilation, we compared inhaled and lost doses of three nebulizer systems coupled with a single-limb circuit bilevel ventilator, as well as the influence of the nebulizer position.

METHOD

Three vibrating mesh nebulizers (Aeroneb(®) Pro, Aeroneb(®) Solo, and NIVO(®)), one jet nebulizer (Sidestream(®)), and one ultrasonic nebulizer (Servo Ultra Nebulizer 145(®)) coupled with a bilevel ventilator were tested. They were charged with amikacin solution (500 mg/4 mL) and operated at two different positions: before and after the exhalation port (starting from the lung). The inhaled dose, the expiratory wasted dose, and the estimated lost dose were assessed by the residual gravimetric method.

RESULTS

The doses varied widely among the nebulizer types and position. When the nebulizer was positioned before the exhalation port, the vibrating mesh nebulizer delivered the highest inhaled dose (p<0.001), the jet nebulizer the highest expiratory wasted dose (p<0.001), and the ultrasonic device the highest total lost dose (p<0.001). When the nebulizer was positioned after the exhalation port, the vibrating mesh nebulizers delivered the highest inhaled (p<0.001) and expiratory wasted doses (p<0.001), and the ultrasonic device the highest total lost dose (p<0.001). The most efficient nebulizers were NIVO and Aeroneb Solo when placed before the exhalation port.

CONCLUSIONS

In a single-limb circuit bilevel ventilator, vibrating mesh nebulizers positioned between the exhalation port and lung model are more efficient for drug delivery compared with jet or ultrasonic nebulizers. In this position, the improved efficiency of vibrating mesh nebulizers was due to an increase in the inhaled dose and a reduction in the exhaled wasted dose compared with placement between the ventilator and the expiratory port. Because of the high total lost dose, the ultrasonic device should not be recommended. Nebulizer placement before the exhalation port increased the inhaled dose and decreased the expiratory wasted dose, except for the jet nebulizer.

In vitro performance of spacers for aerosol delivery during adult mechanical ventilation

BACKGROUND

During mechanical ventilation, different aerosol generators are employed with various interfaces. The objective of this study was to evaluate the performance of a range of spacers, including a new device called Combihaler® designed for connection with both nebulizers and pressurized Metered-Dose Inhalers (pMDIs).

METHODS

To assess the spacers, we used a ventilator and the Dual Adult Training and Test Lung (model 5600i, Michigan Instruments). Ventilation parameters were measured with and without spacers in volume-controlled and pressure-controlled mode. A filter was placed at the end of the endotracheal tube to measure aerosol delivery. Amikacin (1 g/8 mL) and salbutamol (5 mg/5 mL) were nebulized with an Aeroneb Solo® connected to its T-adapter or the Combihaler® spacer. Salbutamol (100 μg/actuation with 10 actuations) and beclomethasone (250 μg/actuation with 10 actuations) were delivered with a pMDI connected to a Minispacer®, an ACE® spacer, or a Combihaler® spacer. Drug delivery measurements were performed in volume-controlled mode in dry and humidified conditions. Drug deposits on the filter were assayed.

RESULTS

The use of spacers and the T-adapter did not change the ventilation parameters (p>0.9). Aerosol delivery of salbutamol and Amikacin by nebulization increased up to three-fold with the Combihaler® compared with the T-adapter in humidified and nonhumidified conditions (p<0.05). Aerosol delivery of salbutamol and beclometasone by pMDI increased up to three-fold with the Combihaler® and the ACE® spacer compared with the Minispacer® in humidified and nonhumidified conditions (p<0.05). Aerosol delivery by pMDIs and vibrating mesh nebulizers using either a T-adapter or spacers was reduced by up to 62.5% in a humidified circuit compared with a nonhumidified circuit.

CONCLUSION

Aerosol delivery via pMDIs and vibrating mesh nebulizers is greater with large spacers (Combihaler® and ACE®) than with smaller spacers (Minispacer®) or a T-adapter, in both humidified and nonhumidified conditions. In humidified conditions, the aerosol delivery decreased with all spacers.

NanoCluster budesonide formulations enable efficient drug delivery driven by mechanical ventilation

Agglomerates of budesonide nanoparticles (also known as 'NanoClusters') are fine dry powder aerosols that were hypothesized to enable drug delivery through ventilator circuits. These engineered powders were delivered via a Monodose inhaler or a novel device, entrained through commercial endotracheal tubes, and analyzed by cascade impaction. Inspiration flow rates and other parameters such as inspiration patterns and inspiration volumes were controlled by a ventilator. NanoCluster budesonide (NC-Bud) formulations had a higher efficiency of aerosol delivery compared to micronized budesonide with NC-Bud showing a much higher percent emitted fraction (%EF). Different inspiration patterns (sine, square, and ramp) did not affect the powder performance of NC-Bud when applied through a 5.0 mm endotracheal tube. The aerosolization of NC-Bud also did not change with the inspiration volume (1.5-2.5 L) nor with the inspiration flow rate (20-40 L/min) suggesting fast emptying times for budesonide capsules. The %EF of NC-Bud was higher at 51% relative humidity compared to 82% RH. The novel device and the Monodose showed the same efficiency of drug delivery but the novel device fit directly to a ventilator and endotracheal tubing connections. The new device combined with NanoCluster formulation technology allowed convenient and efficient drug delivery through endotracheal tubes.

Albuterol delivery in an in vitro pediatric ventilator lung model: comparison of jet, ultrasonic, and mesh nebulizers

OBJECTIVE

To determine the influence of nebulizer types and nebulization modes on bronchodilator delivery in a mechanically ventilated pediatric lung model.

DESIGN

In vitro, laboratory study.

SETTING

Research laboratory of a university hospital.

INTERVENTIONS

Using albuterol as a marker, three nebulizer types (jet nebulizer, ultrasonic nebulizer, and vibrating-mesh nebulizer) were tested in three nebulization modes in a nonhumidified bench model mimicking the ventilatory pattern of a 10-kg infant. The amounts of albuterol deposited on the inspiratory filters (inhaled drug) at the end of the endotracheal tube, on the expiratory filters, and remaining in the nebulizers or in the ventilator circuit were determined. Particle size distribution of the nebulizers was also measured.

MEASUREMENTS AND MAIN RESULTS

The inhaled drug was 2.8% ± 0.5% for the jet nebulizer, 10.5% ± 2.3% for the ultrasonic nebulizer, and 5.4% ± 2.7% for the vibrating-mesh nebulizer in intermittent nebulization during the inspiratory phase (p < 0.01). The most efficient nebulizer was the vibrating-mesh nebulizer in continuous nebulization (13.3% ± 4.6%, p < 0.01). Depending on the nebulizers, a variable but important part of albuterol was observed as remaining in the nebulizers (jet and ultrasonic nebulizers), or being expired or lost in the ventilator circuit (all nebulizers). Only small particles (range 2.39-2.70 µm) reached the end of the endotracheal tube.

CONCLUSIONS

Important differences between nebulizer types and nebulization modes were seen for albuterol deposition at the end of the endotracheal tube in an in vitro pediatric ventilator-lung model. New aerosol devices, such as ultrasonic and vibrating-mesh nebulizers, were more efficient than the jet nebulizer.

Inhalation therapy in patients receiving mechanical ventilation: an update

Incremental gains in understanding the influence of various factors on aerosol delivery in concert with technological advancements over the past 2 decades have fueled an ever burgeoning literature on aerosol therapy during mechanical ventilation. In-line use of pressurized metered-dose inhalers (pMDIs) and nebulizers is influenced by a host of factors, some of which are unique to ventilator-supported patients. This article reviews the impact of various factors on aerosol delivery with pMDIs and nebulizers, and elucidates the correlation between in-vitro estimates and in-vivo measurement of aerosol deposition in the lung. Aerosolized bronchodilator therapy with pMDIs and nebulizers is commonly employed in intensive care units (ICUs), and bronchodilators are among the most frequently used therapies in mechanically ventilated patients. The use of inhaled bronchodilators is not restricted to mechanically ventilated patients with chronic obstructive pulmonary disease (COPD) and asthma, as they are routinely employed in other ventilator-dependent patients without confirmed airflow obstruction. The efficacy and safety of bronchodilator therapy has generated a great deal of interest in employing other inhaled therapies, such as surfactant, antibiotics, prostacyclins, diuretics, anticoagulants and mucoactive agents, among others, in attempts to improve outcomes in critically ill ICU patients receiving mechanical ventilation.

Aerosol delivery through tracheostomy tubes: an in vitro study

BACKGROUND

Our study investigated the influence of the cannula's inner diameter (ID) and of its removal on the expected respiratory dose of amikacin, using three different jet nebulizer configurations (Sidestream(®)): vented (N1), unvented with a piece of corrugated tubing attached to the expiratory limb of the T attachment (N2), and unvented alone (N3).

METHODS

The jet nebulizer was filled with amikacin (500 mg/4 mL) and was attached to the tracheostomy tube. A lung model simulating spontaneous breathing was connected to the tracheostomy tube. A filter was connected between the nebulizer and the tracheostomy tube to measure the inhaled dose, and between the tracheostomy tube and the lung model to measure the respiratory dose. Different cannula IDs were tested (6.5, 8, 8.5, and 10 mm), and aerosol lost in the cannulas was determined.

RESULTS AND CONCLUSIONS

Respiratory dose varied between 96±1 mg and 44±3 mg, with higher values observed with N2. The aerosol lost in the cannula was significant and represented up to 63% of the inhaled dose. There was a negative correlation between the cannula's ID and the aerosol lost in the cannula. After removal of the internal cannula, an increase in the respiratory dose of up to 31.3% was observed. We recommend removing the inner tracheostomy cannula to nebulize a larger amount of drug through a tracheostomy tube. Among the three jet nebulizer configurations studied, we recommend the unvented one with a piece of corrugated tubing attached to the expiratory limb of the T attachment.