Aerosol Delivery Using Jet Nebulizer and Vibrating Mesh Nebulizer During High Frequency Oscillatory Ventilation: An In Vitro Comparison

Aerosol delivery via invasive ventilation: a narrative review

In comparison with spontaneously breathing non-intubated subjects, intubated, mechanically ventilated patients encounter various challenges, barriers, and opportunities in receiving medical aerosols. Since the introduction of mechanical ventilation as a part of modern critical care medicine during the middle of the last century, aerosolized drug delivery by jet nebulizers has become a common practice. However, early evidence suggested that aerosol generators differed in their efficacies, and the introduction of newer aerosol technology (metered dose inhalers, ultrasonic nebulizer, vibrating mesh nebulizers, and soft moist inhaler) into the ventilator circuit opened up the possibility of optimizing inhaled aerosol delivery during mechanical ventilation that could meet or exceed the delivery of the same aerosols in spontaneously breathing patients. This narrative review will catalogue the primary variables associated with this process and provide evidence to guide optimal aerosol delivery and dosing during mechanical ventilation. While gaps exist in relation to the appropriate aerosol drug dose, discrepancies in practice, and cost-effectiveness of the administered aerosol drugs, we also present areas for future research and practice. Clinical practice should expand to incorporate these techniques to improve the consistency of drug delivery and provide safer and more effective care for patients.

In vitro evaluation of disposable transport ventilators with combination aerosol therapy

Background

The COVID-19 pandemic has highlighted the need for alternative short-term, reliable means to aid in the treatment of patients requiring ventilatory support. Concurrent aerosol drug delivery is often prescribed to such patients. As such, this study examines one such short-term option, the disposable gas-powered transport ventilator to effectively deliver aerosol therapy. Factors such as aerosol generator type, patient breathing pattern, humidification and nebuliser position within the respiratory circuit were also examined.

Methods

Aerosol drug delivery characterisation was undertaken using two different disposable transport ventilators (DTVs). Two different nebuliser types, a closed circuit vibrating mesh nebuliser (VMN) and an open circuit jet nebuliser (JN), at different locations in a respiratory circuit, proximal and distal to an endotracheal tube (ETT), with and without passive humidification, were evaluated in simulated adult and paediatric patients.

Results

Placement of a nebuliser proximal to the ETT (VMN: 25.19%–34.15% and JN: 3.14%–8.92%), and the addition of a heat and moisture exchange filter (VMN: 32.37%–40.43% and JN: 5.60%–9.91%) resulted in the largest potential lung dose in the adult patient model. Irrespective of nebuliser position and humidification in the respiratory circuit, use of the VMN resulted in the largest potential lung dose (%). A similar trend was recorded in the paediatric model data, where the largest potential lung dose was recorded with both nebuliser types placed proximal to the ETT (VMN: 8.12%–10.89% and JN: 2.15%–3.82%). However, the addition of a heat and moisture exchange filter had no statistically significant effect on the potential lung dose (%) a paediatric patient would receive (p>>0.05).

Conclusions

This study demonstrates that transport ventilators, such as DTVs, can be used concurrently with aerosol generators to effectively deliver aerosolised medication in both adult and paediatric patients.

Quantitative shadowgraphy of aerosol and droplet creation during oscillatory motion of the microkeratome amid COVID-19 and other infectious diseases

High-speed shadowgraphy showed droplets generated during flap cut with microkeratome. However, aerosolization of these droplets was unlikely because these droplets would settle on surface before aerosolization.

Purpose:

To quantify the atomization of liquid over the cornea during flap creation using microkeratome using high-speed shadowgraphy.

Setting:

Laboratory investigational study.

Design:

Laboratory study.

Method:

In an experimental setup, flap creation was performed on enucleated goat's eyes (n = 8) mounted on a stand using One Use-Plus SBK Moria microkeratome (Moria SA) to assess the spread of aerosols and droplets using high-speed shadowgraphy. Two conditions were computed. A constant airflow assumed uniform air velocity throughout the room. A decaying jet assumed that local air velocity at the site of measurements was smaller than the exit velocity from the air duct.

Results:

With the advancement of the microkeratome across the wet corneal surface, the atomization of a balanced salt solution was recorded on shadowgraphy. The minimum droplet size was ∼90 μm. The maximum distance traversed was ∼1.8 m and ∼1.3 m assuming a constant airflow (setting of refractive surgery theater) and decaying jet condition (setting of an operating theater with air-handling unit), respectively.

Conclusions:

The microkeratome-assisted LASIK flap creation does seem to cause spread of droplets. The droplet diameters and velocities did not permit the formation of aerosols. Therefore, the risk of transmission of the virus to the surgeon and surgical personnel due to the microkeratome procedure seems to be low.

Efficiency of budesonide delivery via a mesh nebulizer in an in-vitro neonatal ventilator model

OBJECTIVE

To determine the delivery efficiency of budesonide aerosol via a mesh nebulizer in a neonatal ventilator model.

DESIGN/METHOD

In an in-vitro ventilated neonatal model, budesonide suspension was administered using a mesh nebulizer. A collection filter was placed distal to the endotracheal tube and budesonide captured by the filter was measured using UV spectroscopy. The ventilator was, in turn, either on high frequency or conventional ventilation mode and the nebulizer was placed either proximal (close to the endotracheal tube) or distal (between the wet side of humidifier and the inspiratory circuit). Each combination (nebulizer position and ventilation mode) to assess budesonide delivery was tested five times.

RESULTS

Overall delivery of budesonide to the distal end of the endotracheal tube a small percentage of the total dose administered. The deposition with conventional ventilation was 2.12% (±1.06) and 1.26% (±0.27), with proximal and distal placement of the nebulizer, respectively. With high-frequency ventilation, the deposition percentages were 1.82% (±0.82) and 1.69% (±0.23), with proximal and distal nebulizer placement, respectively.

CONCLUSION

Only a small percentage of administered budesonide is delivered to the distal endotracheal tube, irrespective of ventilation mode, and nebulizer placement.

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.

Current options in aerosolised drug therapy for children receiving respiratory support

Inhalation of aerosolised medications are the mainstay of treatment for a number of chronic lung diseases and have several advantages over systemically-administered medications. These include more rapid onset of action for drugs such as β-adrenergic agonists when compared with oral medication, high luminal doses for inhaled antibiotics when used to treat endobronchial infection, and an improved therapeutic index compared with systemic delivery for these and other classes of drugs such as corticosteroids. The use of aerosolised drugs to treat patients whose tracheas are intubated is less well established, in part because systemic delivery via the intravenous route can be a simpler alternative for many drugs. Consequently, research in this area is largely limited to a number of in vitro studies and very few clinical trials. Unfortunately, a lack of focus in this area has resulted in a number of practices which at best are ineffective, and at worst dangerous for the patient. Although there have been some attempts to re-invigorate research in order to improve delivery systems, current devices are, to a great extent, based on long-standing technology developed more than 50 years ago. In this review, we explore current knowledge and provide guidance as to when and how the inhaled route may be of value when treating patients whose tracheas are intubated, and we set out the challenges facing those attempting to advance the topic. We conclude by reviewing current areas of interest that may lead to more effective and widespread use of aerosols in the treatment of intubated patients.

Inhaled salbutamol dose delivered by jet nebulizer, vibrating mesh nebulizer and metered dose inhaler with spacer during invasive mechanical ventilation

BACKGROUND

Patient receiving invasive mechanical ventilation (IMV) may benefit from medical aerosol, but guidance on dosing with different aerosol devices is limited to in-vitro studies. The study was designed to compare aerosol delivery with five different types of aerosol generators during IMV.

METHOD

In randomized design, 60 (30 female) mechanically ventilated chronic obstructive pulmonary disease (COPD) patients were assigned to one of 5 groups. Groups 1-4 received 5000 μg salbutamol using Aerogen Pro (PRO), Aerogen Solo (SOLO), NIVO vibrating mesh and jet nebulizers (JN), respectively, while group 5 received 800 μg (8 puffs) of salbutamol via metered dose inhaler with AeroChamber-MV (MDI-AC). All devices were place in the inspiratory limb of ventilator downstream from humidifier which was switched off while delivery. Patients received the inhaled dose on day 1 and provided urine 30 post dosing. They also recived the same inhaled dose with a filter before the endotracheal tube on day 2. Amount of salbutamol excreted in urine 30 min post inhalation and the amount deposited on the filter from all the COPD patients were determined as indeces of pulmonary deposition and systemic absorption, respectively.

RESULTS

No significant difference was found between the 3 vibrating mesh nebulizers (VMNs). The in-vivo and ex-vivo testing showed that all the VMNs resulted in better aerosol delivery compared to JN (p < 0.01). However, MDI-AC resulted in better aerosol delivery to VMNs but must be accompanied with careful attention and proper delivery of MDI-AC doses by healthcare provider.

CONCLUSIONS

VMNs can be exchanged with each other, with no dose adjustment. However, dose adjustment is a must when replacing VMNs by JN or MDI-AC. This similarity and difference between the 5 aerosol delivery methods suggest that for IMV patients, aerosol delivery methods should be chosen or substituted with care.

Inhaled Treprostinil Drug Delivery During Mechanical Ventilation and Spontaneous Breathing Using Two Different Nebulizers

OBJECTIVES

To determine the feasibility of delivering inhaled treprostinil during mechanical ventilation and spontaneous unassisted ventilation using the Tyvaso Inhalation System and the vibrating mesh nebulizer. We sought to compare differences in fine particle fraction, and absolute inhaled treprostinil mass delivered to neonatal, pediatric, and adult models affixed with a face mask, conventional, and high-frequency ventilation between Tyvaso Inhalation System and with different nebulizer locations between Tyvaso Inhalation System and vibrating mesh nebulizer.

DESIGN

Fine particle fraction was first determined via impaction with both the Tyvaso Inhalation System and vibrating mesh nebulizer. Next, a test lung configured with neonatal, pediatric, and adult mechanics and a filter to capture medication was attached to a realistic face model during spontaneous breathing or an endotracheal tube during conventional ventilation and high-frequency oscillator ventilator. Inhaled treprostinil was then nebulized with both the Tyvaso Inhalation System and vibrating mesh nebulizer, and the filter was analyzed via high-performance liquid chromatography. Testing was done in triplicate. Independent two-sample t tests were used to compare mean fine particle fraction and inhaled mass between devices. Analysis of variance with Tukey post hoc tests were used to compare within device differences.

SETTING

Academic children's hospital aerosol research laboratory.

MEASUREMENTS AND MAIN RESULTS

Fine particle fraction was not different between the Tyvaso Inhalation System and vibrating mesh nebulizer (0.78 ± 0.04 vs 0.77 ± 0.08, respectively; p = 0.79). The vibrating mesh nebulizer delivered the same or greater inhaled treprostinil than the Tyvaso Inhalation System in every simulated model and condition. When using the vibrating mesh nebulizer, delivery was highest when using high-frequency oscillator ventilator in the neonatal and pediatric models, and with the nebulizer in the distal position in the adult model.

CONCLUSIONS

The vibrating mesh nebulizer is a suitable alternative to the Tyvaso Inhalation System for inhaled treprostinil delivery. Fine particle fraction is similar between devices, and vibrating mesh nebulizer delivery meets or exceeds delivery of the Tyvaso Inhalation System. Delivery for infants and children during high-frequency oscillator ventilator with the vibrating mesh nebulizer may result in higher than expected dosages.

Inhalation therapy in patients with tracheostomy: a guide to clinicians

INTRODUCTION

Inhalation therapy has become a popular procedure for the treatment of patients with tracheostomy. However, clinicians are faced with many challenges during inhalation therapy because of the many factors affecting aerosol therapy to this patient population, and the lack of literature providing guidance in this area of research. Areas covered: The purpose of this paper is to describe the factors affecting aerosol drug delivery to patients with tracheostomy and to explain how to optimize inhalation therapy through device selection, interface selection and delivery technique in this patient population. Expert commentary: Many factors affect inhalation therapy in this patient population and without understanding the impact of these factors on aerosol drug delivery, clinicians will not be able to provide the treatment properly and patients may not benefit from prescribed medications. In the next 5 years, aerosol medicine will continue to experience tremendous growth with new devices and drug/device combinations. However, these advances will have minimal impact on inhalation therapy in patients with tracheostomy unless we provide guidance and training to clinicians on optimizing aerosol drug delivery to this patient population.