Nebulizers

Nebulizers generate aerosols from liquid-based solutions and suspensions. Nebulizers are particularly well suited to delivering larger doses of medication than is practical with inhalers and are used with a broad range of liquid formulations. When the same drug is available in liquid or inhaler form, nebulizers are applicable for use with patients who will not or cannot reliably use a pressurized metered-dosed inhaler (pMDI) or dry powder inhaler (DPI) due to poor lung function, hand-breath coordination, cognitive abilities (e.g., infants, elderly) or device preference. In a nebulizer, liquid medication is placed in a reservoir and fed to an aerosol generator to produce the droplets. A series of tubes and channels direct the aerosol to the patient via an interface such as mouthpiece, mask, tent, nasal prongs or artificial airway. All nebulizers contain these basic parts, although the technology and design used can vary widely and can result in significant difference in ergonomics, directions for use, and performance. While many types of nebulizers have been described, the three categories of modern clinical nebulizers include: (1) pneumatic jet nebulizers (JN); (2) ultrasonic nebulizers (USN); and (3) vibrating mesh nebulizers (VMN). Nebulizers are also described in terms of their reservoir size. Small volume nebulizers (SVNs), most commonly used for medical aerosol therapy, can hold 5 to 20 mL of medication and may be jet, ultrasonic, or mesh nebulizers. Large volume nebulizers, typically jet or ultrasonic nebulizers, hold up to 200 mL and may be used for either bland aerosol therapy or continuous drug administration.

Effect of Interrupting Heated Humidification on Nebulized Drug Delivery Efficiency, Temperature, and Absolute Humidity During Mechanical Ventilation: A Multi-Lab In Vitro Study

Introduction: During mechanical ventilation (MV), inspired gases require heat and humidification. However, such conditions may be associated with reduced aerosol delivery efficiency. The practice of turning off heated humidification before nebulization and the impact of nebulization on humidity in a dry ventilator circuit remain topics of debate. This study aimed to assess the effect of turning off heated humidification on inhaled dose and humidity with nebulizer use during adult MV. Methods: A bronchodilator (albuterol) and two antibiotics (Colistimethate sodium and Amikacin sulfate) were nebulized with a vibrating mesh nebulizer placed at the humidifier inlet and in the inspiratory limb at the Y-piece. Additionally, albuterol was nebulized using a jet nebulizer in both placements. Aerosol particle size distribution was determined through a cascade impactor. Absolute humidity (AH) and temperature of inspired gases were determined with anemometer/hygrometers before, during, and after nebulization, before, during, and up to 60 minutes after interrupting active humidification. Aerosol collected on a filter distal to the endotracheal tube and on impactor stages were eluted and assayed by spectrophotometry. Results: The inhaled dose was greater when both nebulizers were placed at the humidifier inlet than the inspiratory limb at the Y-piece. Irrespective of the nebulizer types and placements, the inhaled dose either decreased or showed no significant change after the humidifier was turned off. The aerosol particle size ranged from 1.1 to 2.7 μm. With interruption of active humidification, humidity of inspired gas quickly dropped below recommended levels, and nebulization in dry ventilator circuit produced an AH between 10 and 20 mgH2O/L, lower than the recommended minimum of 30 mgH2O/L. Conclusion: Interrupting active humidification during MV before nebulization did not improve aerosol delivery efficiency for bronchodilator or antibiotics, but did reduce humidity below recommended levels.

The Effects of Inspiratory Flows, Inspiratory Pause, and Suction Catheter on Aerosol Drug Delivery with Vibrating Mesh Nebulizers During Mechanical Ventilation

Background: Some experts recommend specific ventilator settings during nebulization for mechanically ventilated patients, such as inspiratory pause, high inspiratory to expiratory ratio, and so on. However, it is unclear whether those settings improve aerosol delivery. Thus, we aimed to evaluate the impact of ventilator settings on aerosol delivery during mechanical ventilation (MV). Methods: Salbutamol (5.0 mg/2.5 mL) was nebulized by a vibrating mesh nebulizer (VMN) in an adult MV model. VMN was placed at the inlet of humidifier and 15 cm away from the Y-piece of the inspiratory limb. Eight scenarios with different ventilator settings were compared with endotracheal tube (ETT) connecting 15 cm from the Y-piece, including tidal volumes of 6-8 mL/kg, respiratory rates of 12-20 breaths/min, inspiratory time of 1.0-2.5 seconds, inspiratory pause of 0-0.3 seconds, and bias flow of 3.5 L/min. In-line suction catheter was utilized in two scenarios. Delivered drug distal to the ETT was collected by a filter, and drug was assayed by an ultraviolet spectrophotometry (276 nm). Results: Compared to the use of inspiratory pause, the inhaled dose without inspiratory pause was either higher or similar across all ventilation settings. Inhaled dose was negatively correlated with inspiratory flow with VMN placed at 15 cm away from the Y-piece (rs = -0.68, p < 0.001) and at the inlet of humidifier (rs = -0.83, p < 0.001). The utilization of in-line suction catheter reduced inhaled dose, regardless of the ventilator settings and nebulizer placements. Conclusions: When VMN was placed at the inlet of humidifier, directly connecting the Y-piece to ETT without a suction catheter improved aerosol delivery. In this configuration, the inhaled dose increased as the inspiratory flow decreased, inspiratory pause had either no or a negative impact on aerosol delivery. The inhaled dose was greater with VMN placed at the inlet of humidifier than 15 cm away the Y-piece.

Individualized aerosol medicine: Integrating device into the patient

Pulmonary drug delivery is complex due to several challenges including disease-, patient-, and clinicians-related factors. Although many inhaled medications are available in aerosol medicine, delivering aerosolized medications to patients requires effective disease management. There is a large gap in the knowledge of clinicians who select and provide instructions for the correct use of aerosol devices. Since improper device selection, incorrect inhaler technique, and poor patient adherence to prescribed medications may result in inadequate disease control, individualized aerosol medicine is essential for effective disease management and control. The components of individualized aerosol medicine include: (1) Selecting the right device, (2) Selecting the right interface, (3) Educating the patient effectively, and (4) Increasing patient adherence to therapy. This paper reviews each of these components and provides recommendations to integrate the device and interface into the patient for better clinical outcomes.

A randomized controlled trial of nebulized surfactant for the treatment of severe COVID-19 in adults (COVSurf trial)

SARS-CoV-2 directly targets alveolar epithelial cells and can lead to surfactant deficiency. Early reports suggested surfactant replacement may be effective in improving outcomes. The aim of the study to assess the feasibility and efficacy of nebulized surfactant in mechanically ventilated COVID-19 patients. Patients were randomly assigned to receive open-labelled bovine nebulized surfactant or control (ratio 3-surfactant: 2-control). This was an exploratory dose-response study starting with 1080 mg of surfactant delivered at 3 time points (0, 8 and 24 h). After completion of 10 patients, the dose was reduced to 540 mg, and the frequency of nebulization was increased to 5/6 time points (0, 12, 24, 36, 48, and an optional 72 h) on the advice of the Trial Steering Committee. The co-primary outcomes were improvement in oxygenation (change in PaO2/FiO2 ratio) and ventilation index at 48 h. 20 patients were recruited (12 surfactant and 8 controls). Demographic and clinical characteristics were similar between groups at presentation. Nebulized surfactant administration was feasible. There was no significant improvement in oxygenation at 48 h overall. There were also no differences in secondary outcomes or adverse events. Nebulized surfactant administration is feasible in mechanically ventilated patients with COVID-19 but did not improve measures of oxygenation or ventilation.

Aerosol therapy in adult critically ill patients: a consensus statement regarding aerosol administration strategies during various modes of respiratory support

BACKGROUND

Clinical practice of aerosol delivery in conjunction with respiratory support devices for critically ill adult patients remains a topic of controversy due to the complexity of the clinical scenarios and limited clinical evidence.

OBJECTIVES

To reach a consensus for guiding the clinical practice of aerosol delivery in patients receiving respiratory support (invasive and noninvasive) and identifying areas for future research.

METHODS

A modified Delphi method was adopted to achieve a consensus on technical aspects of aerosol delivery for adult critically ill patients receiving various forms of respiratory support, including mechanical ventilation, noninvasive ventilation, and high-flow nasal cannula. A thorough search and review of the literature were conducted, and 17 international participants with considerable research involvement and publications on aerosol therapy, comprised a multi-professional panel that evaluated the evidence, reviewed, revised, and voted on recommendations to establish this consensus.

RESULTS

We present a comprehensive document with 20 statements, reviewing the evidence, efficacy, and safety of delivering inhaled agents to adults needing respiratory support, and providing guidance for healthcare workers. Most recommendations were based on in-vitro or experimental studies (low-level evidence), emphasizing the need for randomized clinical trials. The panel reached a consensus after 3 rounds anonymous questionnaires and 2 online meetings.

CONCLUSIONS

We offer a multinational expert consensus that provides guidance on the optimal aerosol delivery techniques for patients receiving respiratory support in various real-world clinical scenarios.

Influence of Mechanical Ventilation Modes on the Efficacy of Nebulized Bronchodilators in the Treatment of Intubated Adult Patients with Obstructive Pulmonary Disease

BACKGROUND

Little has been reported in terms of clinical outcomes to confirm the benefits of nebulized bronchodilators during mechanical ventilation (MV). Electrical Impedance Tomography (EIT) could be a valuable method to elucidate this gap.

OBJECTIVE

The purpose of this study is to evaluate the impact of nebulized bronchodilators during invasive MV with EIT by comparing three ventilation modes on the overall and regional lung ventilation and aeration in critically ill patients with obstructive pulmonary disease.

METHOD

A blind clinical trial in which eligible patients underwent nebulization with salbutamol sulfate (5 mg/1 mL) and ipratropium bromide (0.5 mg/2 mL) in the ventilation mode they were receiving. EIT evaluation was performed before and after the intervention. A joint and stratified analysis into ventilation mode groups was performed, with p < 0.05.

RESULTS

Five of nineteen procedures occurred in controlled MV mode, seven in assisted mode and seven in spontaneous mode. In the intra-group analysis, the nebulization increased total ventilation in controlled (p = 0.04 and ⅆ = 2) and spontaneous (p = 0.01 and ⅆ = 1.5) MV modes. There was an increase in the dependent pulmonary region in assisted mode (p = 0.01 and ⅆ = 0.3) and in spontaneous mode (p = 0.02 and ⅆ = 1.6). There was no difference in the intergroup analysis.

CONCLUSIONS

Nebulized bronchodilators reduce the aeration of non-dependent pulmonary regions and increase overall lung ventilation but there was no difference between the ventilation modes. As a limitation, it is important to note that the muscular effort in PSV and A/C PCV modes influences the impedance variation, and consequently the aeration and ventilation values. Thus, future studies are needed to evaluate this effort as well as the time on ventilator, time in UCI and other variables.

In vitro model for investigating aerosol dispersion in a simulated COVID-19 patient during high-flow nasal cannula treatment

The use of high-flow nasal cannula in the treatment of COVID-19 infected patients has proven to be a valuable treatment option to improve oxygenation. Early in the pandemic, there were concerns for the degree of risk of disease transmission to health care workers utilizing these treatments that are considered aerosol generating procedures. This study developed an in vitro model to examine the release of simulated patient-derived bioaerosol with and without high-flow nasal cannula at gas flow rates of 30 and 50 L/min. Aerosol dispersion was evaluated at 30 and 90 cm distances. Reduction of transmission risk was assessed using a surgical facemask on the manikin. Results indicated that the use of a facemask facilitated a 94-95% reduction in exhaled aerosol concentration at 30 cm and 22-60% reduction for 90 cm distance across both gas flow rates. This bench study confirms that this in vitro model can be used as a tool to assess the risk of disease transmission during aerosol generating procedures in a simulated patient and to test factors to mitigate the risk.

Evaluation of aerosol drug delivery with concurrent low and high flow nasal oxygen

Question addressed by study

Administration of aerosol to patients receiving high flow nasal oxygen (HFNO) ranges from concurrent aerosol delivery by mouthpiece to aerosol via cannula alone. This study examines the conditions to provide optimal aerosol delivery with low or high flow nasal oxygen with concurrent mouthpiece or through nasal cannula alone, and the impact on fugitive aerosols.

Materials and Methods

A vibrating mesh nebulizer delivered salbutamol via mouthpiece, aerosol holding chamber and nasal cannula to an adult head model simulating relaxed breathing. The inhaled dose (%) (mean±sd) was assayed from a filter distal to the trachea. Optical particle sizers were used to measure fugitive aerosol concentrations during aerosol delivery.

Results

Concurrent low flow nasal oxygen (LFNO) and aerosol delivery with a mouthpiece and aerosol holding chamber increased the inhaled dose (%) available, 31.44±1.33% when supplemented with 2 LPM of nasal oxygen. Concurrent HFNO above 30 LPM resulted in a lower inhaled dose (%) compared to aerosol delivered through HFNO alone. The addition of concurrent low or high flow nasal oxygen resulted in no increase in aerosol levels in the test room.

Answer to question posed

Concurrent low flow nasal oxygen with a mouthpiece and aerosol holding chamber is an effective and safe means of aerosol delivery.

Efficacy of Various Mitigation Devices in Reducing Fugitive Emissions from Nebulizers

BACKGROUND

Fugitive aerosol concentrations generated by different nebulizers and interfaces in vivo and mitigation of aerosol dispersion into the environment with various commercially available devices are not known.

METHODS

Nine healthy volunteers were given 3 mL saline with a small-volume nebulizer (SVN) or vibrating mesh nebulizer (VMN) with a mouthpiece, a mouthpiece with an exhalation filter, an aerosol mask with open ports for SVN and a valved face mask for VMN, and a face mask with a scavenger (Exhalo) in random order. Five of the participants received treatments using a face tent scavenger (Vapotherm) and a mask with exhalation filter with SVN and VMN in a random order. Treatments were performed in an ICU room with 2 particle counters positioned 1 and 3 ft from participants measuring aerosol concentrations at sizes of 0.3-10.0 μm at baseline, before, during, and after each treatment.

RESULTS

Fugitive aerosol concentrations were higher with SVN than VMN and higher with a face mask than a mouthpiece. Adding an exhalation filter to a mouthpiece reduced aerosol concentrations of 0.3-1.0 μm in size for VMN and 0.3-3.0 μm for SVN (all P < .05). An Exhalo scavenger over the mask reduced 0.5-3.0 μm sized particle concentrations for SVN (all P < .05) but not VMN. Vapotherm scavenger and filter face mask reduced fugitive aerosol concentrations regardless of the nebulizer type.

CONCLUSIONS

SVN produced higher fugitive aerosol concentrations than VMN, whereas face masks generated higher aerosol concentrations than mouthpieces. Adding an exhalation filter to the mouthpiece or a scavenger to the face mask reduced aerosol concentrations for both SVN and VMN. Vapotherm scavenger and filter face mask reduced fugitive aerosols as effectively as a mouthpiece with an exhalation filter. This study provides guidance for reducing fugitive aerosol emissions from nebulizers in clinical practice.

Aerosol Delivery via Continuous High-Frequency Oscillation During Mechanical Ventilation

BACKGROUND

As the use of continuous high-frequency oscillation combined with nebulization during mechanical ventilation becomes more prevalent clinically, it is important to evaluate its aerosol delivery efficacy.

METHODS

A bench study was conducted that simulated 2 adult and 2 pediatric conditions. A continuous high-frequency oscillation device integrated into the inspiratory limb of a conventional critical care ventilator was attached to an endotracheal tube (ETT) with a collection filter and test lung. High-frequency oscillation with high-flow setting was used with jet nebulizers attached to the manifold, and a vibrating mesh nebulizer placed between the ETT and the ventilator circuit versus at the inlet of the humidifier. Albuterol (2.5 mg in 3 mL) was nebulized for each condition (no. = 3). The drug was eluted from the collection filter and assayed with ultraviolet spectrophotometry (276 nm).

RESULTS

During continuous high-frequency oscillation, the mean inhaled dose with jet nebulizers was low (<2% with the adult settings and <1% with the pediatric settings). Across both adult and pediatric conditions, when the vibrating mesh nebulizer was placed between the ETT and the Y-piece during continuous high-frequency oscillation, the inhaled dose was higher than with the placement of the vibrating mesh nebulizer at the inlet of the humidifier, median 11.1% (IQR 7.0%-13.7%) median 6.0% (IQR 3.9%-7.2%) (P = .002) respectively, but still lower than the inhaled dose with the vibrating mesh nebulizer placed at the inlet of the humidifier with continuous high-frequency oscillation off, median 22.7% (IQR 19.5%-25.4%) versus median 11.1% (IQR 7.0%-13.7%) (P < .001). The inhaled dose with the 10-year-old scenario was higher than with the 5-year-old scenario in all settings except aerosol delivery via continuous high-frequency oscillation.

CONCLUSIONS

During invasive mechanical ventilation with continuous high-frequency oscillation, aerosol delivery with jet nebulizers in the manifold resulted in a marginal inhaled dose. The vibrating mesh nebulizer at the ETT during continuous high-frequency oscillation delivered 6-fold more aerosol than did the jet nebulizer, while delivering only half of the inhaled dose with the vibrating mesh nebulizer placed at the inlet of the humidifier without continuous high-frequency oscillation.

Mitigating Fugitive Aerosols During Aerosol Delivery via High-Flow Nasal Cannula Devices

BACKGROUND

Aerosol delivery via high-flow nasal cannula (HFNC) has attracted clinical interest in recent years. However, both HFNC and nebulization are categorized as aerosol-generating procedures (AGPs). In vitro studies raised concerns that AGPs had high transmission risk. Very few in vivo studies examined fugitive aerosols with nebulization via HFNC, and effective methods to mitigate aerosol dispersion are unknown.

METHODS

Two HFNC devices (Airvo 2 and Vapotherm) with or without a vibrating mesh nebulizer were compared; HFNC alone, surgical mask over HFNC interface, and HFNC with face tent scavenger were used in a random order for 9 healthy volunteers. Fugitive aerosol concentrations at sizes of 0.3-10.0 μm were continuously measured by particle sizers placed at 1 and 3 ft from participants. On a different day, 6 of the 9 participants received 6 additional nebulizer treatments via vibrating mesh nebulizer or small-volume nebulizer (SVN) with a face mask or a mouthpiece with/without an expiratory filter. In vitro simulation was employed to quantify inhaled dose of albuterol with vibrating mesh nebulizer via Airvo 2 and Vapotherm.

RESULTS

Compared to baseline, neither HFNC device generated higher aerosol concentrations. Compared to HFNC alone, vibrating mesh nebulizer via Airvo 2 generated higher 0.3-1.0 μm particles (all P < .05), but vibrating mesh nebulizer via Vapotherm did not. Concentrations of 1.0-3.0 μm particles with vibrating mesh nebulizer via Airvo 2 were similar with vibrating mesh nebulizer and a mouthpiece/face mask but less than SVN with a mouthpiece/face mask (all P < .05). Placing a surgical mask over HFNC during nebulization reduced 0.5-1.0 μm particles (all P < .05) to levels similar to the use of a nebulizer with mouthpiece and expiratory filter. In vitro the inhaled dose of albuterol with vibrating mesh nebulizer via Airvo 2 was ≥ 6 times higher than vibrating mesh nebulizer via Vapotherm.

CONCLUSIONS

During aerosol delivery via HFNC, Airvo 2 generated higher inhaled dose and consequently higher fugitive aerosols than Vapotherm. Simple measures, such as placing a surgical mask over nasal cannula during nebulization via HFNC, could effectively reduce fugitive aerosol concentrations.

Optimizing high-flow nasal cannula flow settings in adult hypoxemic patients based on peak inspiratory flow during tidal breathing

Background

Optimal flow settings during high-flow nasal cannula (HFNC) therapy are unknown. We investigated the optimal flow settings during HFNC therapy based on breathing pattern and tidal inspiratory flows in patients with acute hypoxemic respiratory failure (AHRF).

Methods

We conducted a prospective clinical study in adult hypoxemic patients treated by HFNC with a fraction of inspired oxygen (F_IO₂) ≥ 0.4. Patient’s peak tidal inspiratory flow (PTIF) was measured and HFNC flows were set to match individual PTIF and then increased by 10 L/min every 5–10 min up to 60 L/min. F_IO₂ was titrated to maintain pulse oximetry (SpO₂) of 90–97%. SpO₂/F_IO₂, respiratory rate (RR), ROX index [(SpO₂/F_IO₂)/RR], and patient comfort were recorded after 5–10 min on each setting. We also conducted an in vitro study to explore the relationship between the HFNC flows and the tracheal F_IO₂, peak inspiratory and expiratory pressures.

Results

Forty-nine patients aged 58.0 (SD 14.1) years were enrolled. At enrollment, HFNC flow was set at 45 (38, 50) L/min, with an F_IO₂ at 0.62 (0.16) to obtain an SpO₂/F_IO₂ of 160 (40). Mean PTIF was 34 (9) L/min. An increase in HFNC flows up to two times of the individual patient’s PTIF, incrementally improved oxygenation but the ROX index plateaued with HFNC flows of 1.34–1.67 times the individual PTIF. In the in vitro study, when the HFNC flow was set higher than PTIF, tracheal peak inspiratory and expiratory pressures increased as HFNC flow increased but the F_IO₂ did not change.

Conclusion

Mean PTIF values in most patients with AHRF were between 30 and 40 L/min. We observed improvement in oxygenation with HFNC flows set above patient PTIF. Thus, a pragmatic approach to set optimal flows in patients with AHRF would be to initiate HFNC flow at 40 L/min and titrate the flow based on improvement in ROX index and patient tolerance.

Trial registration: ClinicalTrials.gov (NCT03738345). Registered on November 13th, 2018. https://clinicaltrials.gov/ct2/show/NCT03738345?term=NCT03738345&draw=2&rank=1

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00949-8.

Aerosol particle concentrations with different oxygen devices and interfaces for spontaneous breathing patients with tracheostomy: a randomised crossover trial

For stable spontaneously breathing tracheostomy patients with uncuffed airways, different humidification devices and interfaces did not generate clinically significant differences of aerosol particle concentrations https://bit.ly/2Y1HSO2.

The Impact of High-Flow Nasal Cannula Device, Nebulizer Type, and Placement on Trans-Nasal Aerosol Drug Delivery: An In Vitro Study

BACKGROUND

Aerosol delivery via high-flow nasal cannula (HFNC) has been increasingly used in recent years. However, the effects of different HFNC devices, nebulizer types, and placement on aerosol deposition remain largely unknown.

METHODS

An adult manikin with anatomically correct upper airway was used with a collection filter placed between the manikin's trachea and a breathing simulator, composed of a dual-chamber model lung driven by a critical care ventilator. Three HFNC device configurations were compared, with vibrating mesh nebulizer and small-volume nebulizer placed at the humidifier (inlet for Optiflow and outlet for Airvo 2) and proximal to the nasal cannula at gas flows of 10, 20, 40 and 60 L/min, in quiet and distressed breathing patterns. Albuterol (2.5 mg) was nebulized for each condition (no. = 3). The drug was eluted from the collection filter and assayed with ultraviolet spectrophotometry (276 nm).

RESULTS

At all settings, except when a nebulizer was placed proximal to the nasal cannula with the Optiflow and when the HFNC flow was set at 60 L/min, the vibrating mesh nebulizer generated a higher inhaled dose than did the small-volume nebulizer (all P < .05). With the exception of distressed breathing at an HFNC flow of 10 L/min, the inhaled dose with the vibrating mesh nebulizer placed at the humidifier was greater than with the vibrating mesh nebulizer placed proximal to the nasal cannula (all P < .05), Optiflow provided a higher inhaled dose than did Airvo 2 with either AirSpiral or 900PT501 circuits with the vibrating mesh nebulizer placed at the humidifier (all P < .05).

CONCLUSIONS

During transnasal aerosol delivery, the vibrating mesh nebulizer generated a higher inhaled dose than did the small-volume nebulizer when the nebulizer was placed at the humidifier. With the vibrating mesh nebulizer placed at the humidifier and an HFNC flow > 10 L/min, the inhaled dose was higher than with the vibrating mesh nebulizer placed proximal to the nasal cannula, and the inhaled dose was higher with Optiflow than with Airvo 2.

Worldwide Clinical Practice of High-Flow Nasal Cannula and Concomitant Aerosol Therapy in the Adult ICU Setting

BACKGROUND

High-flow nasal cannula (HFNC) oxygen therapy has been broadly used. However, no consensus has been achieved on the practical implementation of HFNC and how to provide aerosol delivery during HFNC therapy in adult patients.

METHODS

An online anonymous questionnaire survey endorsed by 4 academic societies from America, Europe, mainland China, and Taiwan was administered from May to December 2019. Clinicians who had worked in adult ICUs for > 1 year and had used HFNC to treat patients within 30 days were included.

RESULTS

A total of 2,279 participants clicked on the survey link, 1,358 respondents completed the HFNC section of the questionnaire, whereas 1,014 completed the whole survey. Postextubation hypoxemia and moderate hypoxemia were major indications for HFNC. The initial flow was mainly set at 40-50 L/min. Aerosol delivery via HFNC was used by 24% of the participants (248/1,014), 30% (74/248) of whom reported reducing flow during aerosol delivery. For the patients who required aerosol treatment during HFNC therapy, 40% of the participants (403/1,014) reported placing a nebulizer with a mask or mouthpiece while pursuing HFNC whereas 33% (331/1,014) discontinued HFNC to use conventional aerosol devices. A vibrating mesh nebulizer was the most commonly used nebulizer (40%) and was mainly placed at the inlet of the humidifier.

CONCLUSIONS

The clinical utilization of HFNC was variable, as were indications, flow settings, and criteria for adjustment. Many practices associated with concomitant aerosol therapy were not consistent with available evidence for optimal use. More efforts are warranted to close the knowledge gap.

In-vitro and in-vivo comparisons of high versus low concentrations of inhaled epoprostenol to adult intubated patients

BACKGROUND

Inhaled epoprostenol (iEPO) has been shown to reduce pulmonary artery pressure and improve oxygenation. iEPO is mainly delivered via a syringe pump with feed tubing connected to a vibrating mesh nebulizer with high or low formulation concentration delivery.

METHODS

An in vitro study and a two-period retrospective case-control study were implemented. The in vitro study compared iEPO delivery via invasive ventilation at low concentrations of 7.5, and 15 mcg/mL and high concentration at 30 mcg/mL, to deliver the ordered dose of 30 and 50 ng/kg/min for three clinical scenarios with predicted body weight of 50, 70 and 90 kg. While in the clinical study, adult patients receiving iEPO via invasive ventilation to treat refractory hypoxemia, pulmonary hypertension, or right ventricular failure were included. 80 patients received low concentration iEPO at multiple concentrations (2.5, 7.5, and 15 mcg/mL, depending on the ordered dose) from 2015 to 2017, while 84 patients received high concentration iEPO at 30 mcg/mL from 2018 to 2019.

RESULTS

In the in vitro study, there were no significant differences in aerosol deposition between high vs low concentrations of iEPO at a dose of 50 ng/kg/min. In the clinical study, age, gender, ethnicity, and indications for iEPO were similar between high and low concentration groups. After 30-120 min of iEPO administration, both delivery strategies significantly improved oxygenation in hypoxemic patients and reduced mean pulmonary arterial pressure (mPAP) for patients with pulmonary hypertension. However, no significant differences of the incremental changes were found between two delivery groups. Compared to low concentration, high concentration delivery group had better adherence to the iEPO weaning protocol (96% vs 71%, p < 0.001), fewer iEPO syringes utilized per patient (5 [3, 10] vs 12 [6, 22], p = 0.001), and shorter duration of invasive ventilation (6 [3, 12] vs 9 [5, 18] days, p = 0.028). Intensive care unit length of stay and mortality were similar between two groups.

CONCLUSION

Compared to low concentration delivery of iEPO, high concentration iEPO via a vibrating mesh nebulizer maintained clinical benefits and increased clinician compliance with an iEPO weaning protocol, required less medication preparation time, and shortened duration of invasive ventilation.

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.

Delivered dose with jet and mesh nebulisers during spontaneous breathing, noninvasive ventilation and mechanical ventilation using adult lung models

What is the delivered dose with jet and mesh nebulisers during spontaneous breathing (SB), noninvasive ventilation (NIV), and mechanical ventilation (MV) using an adult lung model with exhaled humidity (EH)? The delivery of salbutamol sulfate (2.5 mg per 3 mL) with jet (Mistymax10) and mesh nebulisers (Aerogen Solo) was compared during SB, NIV, and MV using breathing parameters (tidal volume 450 mL, respiratory rate 20 breaths per min, inspiratory:expiratory ratio 1:3) with three lung models simulating exhaled humidity. A manikin was attached to a sinusoidal pump via a filter at the bronchi to simulate an adult with SB. A ventilator (V60) was attached via a facemask to a manikin with a filter at the bronchi connected to a test lung to simulate an adult receiving NIV. A ventilator-dependent adult was simulated through a ventilator (Servo-i) operated with a heated humidifier (Fisher & Paykel) attached to an endotracheal tube (ETT) with a heated-wire circuit. The ETT was inserted into a filter (Respirgard II). A heated humidifier was placed between the filter and test lung to simulate exhaled humidity (35±2°C, 100% relative humidity). Nebulisers were placed at the Y-piece of the inspiratory limb during MV and positioned between the facemask and the leak-port during NIV. A mouthpiece was used during SB. The delivered dose was collected in an absolute filter that was attached to the bronchi of the mannequin during each aerosol treatment and measured with spectrophotometry. Drug delivery during MV was significantly greater than during NIV and SB with a mesh nebuliser (p=0.0001) but not with a jet nebuliser (p=0.384). Delivery efficiency of the mesh nebuliser was greater than the jet nebuliser during MV (p=0.0001), NIV (p=0.0001), and SB (p=0.0001). Aerosol deposition obtained with a mesh nebuliser was greater and differed between MV, NIV, and SB, while deposition was low with a jet nebuliser and similar between the modes of ventilation tested.

Aerosol drug delivery to tracheotomized patients with COVID-19: Pragmatic suggestions for clinicians

Because of the wide and rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the number of hospitalized patients with coronavirus disease 2019 (COVID-19) has rapidly increased medically complex and resource-intensive treatment requirements in health care settings. Although tracheostomy is frequently needed for critically ill patients requiring extended mechanical ventilation, it has been described as an aerosol-generating procedure that puts health care professionals at an increased risk of viral transmission. In addition, the delivery of aerosolized medications to this patient population has become controversial because of concerns on the transmission of SARS-CoV-2 via droplets. Although aerosol therapy in spontaneously breathing patients with COVID-19 was described in recent publications, innovations in aerosol drug delivery to COVID-19 patients with tracheostomy have not been presented. Therefore, empirically based guidance on how to deliver aerosols safely and effectively to tracheotomized patients with COVID-19 is still lacking. This paper provides recommendations and rationales for device selection, interface selection, delivery techniques, and infection control based on the evolving body of literature.

Comparison of Vibrating Mesh and Jet Nebulizers During Noninvasive Ventilation in Acute Exacerbation of Chronic Obstructive Pulmonary Disease

Background: Advances in aerosol technology have improved drug delivery efficiency during noninvasive ventilation (NIV). Clinical evaluation of the efficacy of aerosol therapy during NIV in the treatment of acute exacerbation of chronic obstructive pulmonary disease (COPD) is very limited. The aim of our study was to compare the efficacy of bronchodilators administered through a vibrating mesh nebulizer (VMN) and jet nebulizer (JN) during NIV in patients with acute exacerbation of COPD. Methods: Prospective randomized cross-over study included 30 patients treated with NIV for acute exacerbation of COPD in an acute care hospital. Patients were consented and enrolled after stabilization of acute exacerbation (3-5 days after admission). Subjects were randomly assigned into two treatment arms receiving salbutamol (2.5 mg): with VMN (Aerogen Solo) and JN (Sidestream) positioned between the leak port and the nonvented oronasal mask during bilevel ventilation with a single-limb circuit. Measurements (clinical data, pulmonary function tests [PFTs], and arterial blood gases) were performed at baseline, 1, and 2 hours after treatment. Results: All measured PFT parameters significantly increased in both groups, but numerically results were better after inhalation with VMN than with JN: for forced expiratory volume in 1 second (FEV₁) (mean increase from baseline to 120 minutes-165 ± 64 mL vs. 116 ± 46 mL, p = 0.001) and for forced vital capacity (FVC) (mean increase-394 ± 154 mL vs. 123 ± 57 mL, p < 0.001). There was also a statistically significant reduction in respiratory rate and in Borg dyspnea score after therapy with VMN in comparison with the conventional JN. In both groups, there were improvements in PaCO₂, but with VMN these changes were significantly higher. Conclusion: Bronchodilator administration in patients with acute exacerbation of COPD during NIV with VMN resulted in clinically significant improvements in FVC and in Borg dyspnea score. Additional studies required to determine the impact on clinical outcomes.

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.

Narrative review of practical aspects of aerosol delivery via high-flow nasal cannula

Using high-flow nasal cannula (HFNC) as a "vehicle" to administer aerosolized medication has attracted clinicians' interest in recent years. In this paper, we summarize the current evidence to answer the common questions raised by clinicians about this new aerosol delivery route and best practices of administration. Benefits of trans-nasal aerosol delivery include increased comfort, ability to speak, eat, and drink for patients while meeting a range of oxygen requirements, particularly for those who need to inhale aerosolized medication for long periods. Aerosol administration via HFNC has been shown to be well tolerated by children and adults, with comparable or better delivery efficacy than other interfaces, ranging from 2-20%. In vitro and in vivo scintigraphy studies among pediatric and adult populations reported that the inhaled dose delivered via a vibrating mesh nebulizer is 2 to 3 fold greater than that via a jet nebulizer. For adults, placement of nebulizer at the inlet of humidifier increases inhaled dose while reducing rainout obstructing nasal prongs. When HFNC gas flow is set below patient inspiratory flow, aerosol deposition is higher than when the gas flow exceeds patient inspiratory flow; thus, if tolerated, titrating down HFNC gas flow during trans-nasal aerosol delivery, with close monitoring and the use of unit dose with high concentration are recommended. Trans-nasal pulmonary aerosol delivery has not been shown to increase bioaerosols generated by patients, but gas flow may disperse aerosols. Placement of a surgical or procedure mask over HFNC might reduce aerosol dispersion.

Placing a mask on COVID-19 patients during high-flow nasal cannula therapy reduces aerosol particle dispersion

Wearing a surgical/procedure mask over high-flow nasal cannula (HFNC) reduces aerosol particle concentrations in the patients' vicinity. Wearing a mask over HFNC should be encouraged to reduce risks of aerosol transmission. #COVID19 https://bit.ly/2HLg5cE.

Effects of Inhaled Epoprostenol and Prone Positioning in Intubated Coronavirus Disease 2019 Patients With Refractory Hypoxemia

OBJECTIVES

To evaluate the effects of inhaled epoprostenol and prone positioning, individually and in combination in mechanically ventilated patients with coronavirus disease 2019 and refractory hypoxemia.

DESIGN

Retrospective study.

SETTING

Academic hospital adult ICUs.

PATIENTS

Adult patients who received inhaled epoprostenol and prone positioning during invasive ventilation were enrolled. Patients were excluded if inhaled epoprostenol was initiated: 1) at an outside hospital, 2) after prone positioning was terminated, 3) during extracorporeal membrane oxygenation or cardiopulmonary resuscitation, and 4) with Pao2/Fio2 greater than 150 mm Hg.

INTERVENTIONS

Inhaled epoprostenol and prone positioning.

RESULTS

Of the 43 eligible patients, 22 and seven received prone positioning and inhaled epoprostenol alone, respectively, prior to their use in combination, Pao2/Fio2 was not different pre- and post-prone positioning or inhaled epoprostenol individually (89.1 [30.6] vs 97.6 [30.2] mm Hg; p = 0.393) but improved after the combined use of inhaled epoprostenol and prone positioning (84.0 [25.6] vs 124.7 [62.7] mm Hg; p < 0.001). While inhaled epoprostenol and prone positioning were instituted simultaneously in 14 patients, Pao2/Fio2 was significantly improved (78.9 [27.0] vs 150.2 [56.2] mm Hg, p = 0.005) with the combination. Twenty-seven patients (63%) had greater than 20% improvement in oxygenation with the combination of inhaled epoprostenol and prone positioning, and responders had lower mortality than nonresponders (52 vs 81%; p = 0.025).

CONCLUSIONS

In critically ill, mechanically ventilated patients with coronavirus disease 2019 who had refractory hypoxemia, oxygenation improved to a greater extent with combined use of inhaled epoprostenol and prone positioning than with each treatment individually. A higher proportion of responders to combined inhaled epoprostenol and prone positioning survived compared with nonresponders. These findings need to be validated by randomized, prospective clinical trials.

In Vitro Evaluation of a Vibrating-Mesh Nebulizer Repeatedly Use over 28 Days

This in vitro study evaluates the performance of a disposable vibrating-mesh nebulizer when used for 28 days. A lung model was used to simulate the breathing pattern of an adult with chronic obstructive pulmonary disease. The vibrating-mesh nebulizer was used for three treatments/day over 28 days without cleaning after each test. Results showed that the inhaled drug dose was similar during four weeks of use (p = 0.157), with 16.73 ± 4.46% at baseline and 15.29 ± 2.45%, 16.21 ± 2.21%, 17.56 ± 1.98%, and 17.13 ± 1.81%, after the first, second, third, and fourth weeks, respectively. The particle size distribution, residual drug volume, and nebulization time remained similar across four weeks of use (p = 0.110, p = 0.763, and p = 0.573, respectively). Mesh was inspected using optical microscopy and showed that approximately 50% of mesh pores were obscured after 84 runs, and light penetration through the aperture plate was significantly reduced after the 21st use (p < 0.001) with no correlation to nebulizer performance. We conclude that the vibrating-mesh nebulizer delivered doses of salbutamol solution effectively over four weeks without cleaning after each use even though the patency and clarity of the aperture plate were reduced by the first week of use.

High-flow nasal cannula for COVID-19 patients: risk of bio-aerosol dispersion

We appreciate the comments of J. Elshof and co-workers on our article “High-flow nasal cannula for COVID-19 patients: low risk of bio-aerosol dispersion” [1] and agree that further research is warranted to reduce the risk of virus transmission from infected patients. The presented in vitro data of J. Elshof and co-workers from a model using light detection of smoke dispersion distance and velocity, suggesting that high-flow nasal cannula (HFNC) generates a larger dispersion distance than non-rebreather masks and Venturi masks, is in contrast to reports from Huiet al. [2] using a similar model. Presumably, because the smoke used by J. Elshof and co-workers was larger (0.3–2.5 µm) than that used by Huiet al. [2] (≤1 µm), the larger particles dispersed differently. It should be noted that smoke in both models represents only a small fraction of the range of bio-aerosols generated by patients during breathing, speaking, coughing or sneezing [3]. Using the same size airway model, J. Elshof and co-workers observed that the dispersion distance decreased from 71 cm to 25 cm by changing the nasal cannula size from small to large when HFNC flow was set at 30 L·min⁻¹; however, when HFNC flow was set at 60 L·min⁻¹, the medium-size nasal cannula generated a shorter distance than both small and large nasal cannulas. This raises the role of proper fit of prongs to nares and highlights the limitations of modelling. Regardless of the sizes of nasal cannula, the dispersion distance was farther with 60 L·min⁻¹ than 30 L·min⁻¹, which is in line with the results of Huiet al. [2] and may be expected, as higher velocity of the gas will carry exhaled smoke to a further distance. However, this effect of total flow did not occur when testing the Venturi mask. Surprisingly, the Venturi mask with large open holes and a total gas flow of 40 L·min⁻¹ generated a shorter dispersion distance than normal breathing. These inconsistencies are difficult to interpret without comprehensive peer review of extensive methods and results. Whether smoke imaging models truly reflect the natural features of the transportation and dispersion of bio-aerosols generated by patients has not been established and results from these studies should be interpreted cautiously.

High-flow nasal cannula does not generate higher risk of bio-aerosol dispersion than conventional oxygen maskshttps://bit.ly/2Yn0RQn

Practical strategies to reduce nosocomial transmission to healthcare professionals providing respiratory care to patients with COVID-19

Coronavirus disease (COVID-19) is an emerging viral infection that is rapidly spreading across the globe. SARS-CoV-2 belongs to the same coronavirus class that caused respiratory illnesses such as severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). During the SARS and MERS outbreaks, many frontline healthcare workers were infected when performing high-risk aerosol-generating medical procedures as well as when providing basic patient care. Similarly, COVID-19 disease has been reported to infect healthcare workers at a rate of ~ 3% of cases treated in the USA. In this review, we conducted an extensive literature search to develop practical strategies that can be implemented when providing respiratory treatments to COVID-19 patients, with the aim to help prevent nosocomial transmission to the frontline workers.

The utilization of aerosol therapy in mechanical ventilation patients: a prospective multicenter observational cohort study and a review of the current evidence

Background

Aerosol delivery via mechanical ventilation has been reported to vary significantly among different intensive care units (ICU). The optimal technique for using each aerosol generator may need to be updated with the available evidence.

Methods

A 2-week prospective multicenter observational cohort study was implemented to record aerosol delivery for mechanically ventilated adult patients in Chinese ICUs. Our data included the type of aerosol device and its placement, ventilator type, humidification, and aerosolized medication administered. A guide for the optimal technique for aerosol delivery during mechanical ventilation was summarized after a thorough literature review.

Results

A total of 160 patients (105 males) from 28 ICUs were enrolled, of whom 125 (78.1%) received aerosol therapy via invasive ventilation. Among these 125 patients, 53 received ventilator-integrated jet nebulizer, with 64% (34/53) of them placed the nebulizer close to Y piece in the inspiratory limb. Further, 56 patients used continuous nebulizers, with 84% (47/56) of them placed the nebulizer close to the Y piece in the inspiratory limb. Of the 35 patients who received aerosol therapy via noninvasive ventilation, 30 received single limb ventilators and continuous nebulizers, with 70% (21/30) of them placed between the mask and exhalation port. Only 36% (58/160) of the patients received aerosol treatments consistent with optimal practice.

Conclusions

Aerosol delivery via mechanical ventilation varied between ICUs, and only 36% of the patients received aerosol treatments consistent with optimal practice. ICU clinicians should be educated on the best practices for aerosol therapy, and quality improvement projects aim to improve the quality and outcome of patients with the optimal technique for aerosol delivery during mechanical ventilation are warranted.

A narrative review on trans-nasal pulmonary aerosol delivery

The use of trans-nasal pulmonary aerosol delivery via high-flow nasal cannula (HFNC) has expanded in recent years. However, various factors influencing aerosol delivery in this setting have not been precisely defined, and no consensus has emerged regarding the optimal techniques for aerosol delivery with HFNC. Based on a comprehensive literature search, we reviewed studies that assessed trans-nasal pulmonary aerosol delivery with HFNC by in vitro experiments, and in vivo, by radiolabeled, pharmacokinetic and pharmacodynamic studies. In these investigations, the type of nebulizer employed and its placement, carrier gas, the relationship between gas flow and patient’s inspiratory flow, aerosol delivery strategies (intermittent unit dose vs continuous administration by infusion pump), and open vs closed mouth breathing influenced aerosol delivery. The objective of this review was to provide rational recommendations for optimizing aerosol delivery with HFNC in various clinical settings.

Novel Toxicology Program to Support the Development of Inhaled VentaProst

Currently, off-label continuous administration of inhaled epoprostenol is used to manage hemodynamics during mitral valve surgery. A toxicology program was developed to support the use of inhaled epoprostenol during mechanical ventilation as well as pre- and postsurgery via nasal prongs. To support use in patients using nasal prongs, a Good Laboratory Practice (GLP), 14-day rat, nose-only inhalation study was performed. No adverse findings were observed at ∼50× the dose rate received by patient during off-label use. To simulate up to 48 hours continuous aerosol exposure during mechanical ventilation, a GLP toxicology study was performed using anesthetized, intubated, mechanically ventilated dogs. Dogs inhaled epoprostenol at approximately 6× and 13× the dose rate reported in off-label human studies. This novel animal model required establishment of a dog intensive care unit providing sedation, multisystem support, partial parenteral nutrition, and management of the intubated mechanically ventilated dogs for the 48-hour duration of study. Aerosol was generated by a vibrating mesh nebulizer with novel methods required to determine dose and particle size in-vitro. Continuous pH 10.5 epoprostenol was anticipated to be associated with lung injury; however, no adverse findings were observed. As no toxicity at pH 10.5 was observed with a formulation that required refrigeration, a room temperature stable formulation at pH 12 was evaluated in the same ventilated dog model. Again, there were no adverse findings. In conclusion, current toxicology findings support the evaluation of inhaled epoprostenol at pH 12 in surgical patients with pulmonary hypertension for up to 48 hours continuous exposure.

Reducing Aerosol-Related Risk of Transmission in the Era of COVID-19: An Interim Guidance Endorsed by the International Society of Aerosols in Medicine

National and international guidelines recommend droplet/airborne transmission and contact precautions for those caring for coronavirus disease 2019 (COVID-19) patients in ambulatory and acute care settings. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, an acute respiratory infectious agent, is primarily transmitted between people through respiratory droplets and contact routes. A recognized key to transmission of COVID-19, and droplet infections generally, is the dispersion of bioaerosols from the patient. Increased risk of transmission has been associated with aerosol generating procedures that include endotracheal intubation, bronchoscopy, open suctioning, administration of nebulized treatment, manual ventilation before intubation, turning the patient to the prone position, disconnecting the patient from the ventilator, noninvasive positive-pressure ventilation, tracheostomy, and cardiopulmonary resuscitation. The knowledge that COVID-19 subjects can be asymptomatic and still shed virus, producing infectious droplets during breathing, suggests that health care workers (HCWs) should assume every patient is potentially infectious during this pandemic. Taking actions to reduce risk of transmission to HCWs is, therefore, a vital consideration for safe delivery of all medical aerosols. Guidelines for use of personal protective equipment (glove, gowns, masks, shield, and/or powered air purifying respiratory) during high-risk procedures are essential and should be considered for use with lower risk procedures such as administration of uncontaminated medical aerosols. Bioaerosols generated by infected patients are a major source of transmission for SARS CoV-2, and other infectious agents. In contrast, therapeutic aerosols do not add to the risk of disease transmission unless contaminated by patients or HCWs.

Predictive anatomical factors of lung aerosol deposition in obese individuals. Would modified mallampati score be relevant? Clinical trial

BACKGROUND

Obesity is a highly prevalent condition worldwide that aggravates symptoms of already existing conditions such as asthma and COPD. The limited effectiveness of inhaled medications in these individuals may be related to anatomic characteristics of their upper airways, mainly due to compressive factors.

METHODS

Controlled clinical trial with obese and nonobese individuals. The following variables were evaluated: anthropometric characteristics, Lung and airway deposition of radiolabeled aerosol (pulmonary scintigraphy), upper airways anatomy (CT scans), and modified Mallampati score.

RESULTS

29 subjects (17 nonobese and 12 obese) participated. Obese volunteers presented 30% lower aerosol lung deposition compared to nonobese. Moreover, obese subjects Mallampati classification of 4 presented an aerosol lung deposition two times lower than nonobese subjects (p = 0.021). The cross-sectional area of the retropalatal region and retroglossal region were lower in obese patients (p < 0.05), but no correlation to aerosol lung deposition was observed. BMI was associated with 32% of the variance of lung deposition (p < 0.001; β -0.28; 95% CI -0.43 to -0.11).

CONCLUSION

High BMI correlated to reduced percentage lung deposition. Also, modified Mallampati class 4 was even more detrimental to aerosol delivery into the lungs. Obese subjects have narrower upper airways, compared to nonobese, but this is not reflected in higher radiolabeled aerosol impaction into their oropharynx and does not predict the percentage of lung deposition in this group.

CLINICAL TRIAL REGISTRATION

NCT03031093 (clinicaltrials.org).

High-flow nasal cannula for COVID-19 patients: low risk of bio-aerosol dispersion

Human-to-human severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission has been established, with >3300 clinicians reported to be infected in China and >1116 clinicians infected in Italy, where 13 882 cases were confirmed by 13 March 2020. Room surfaces in the vicinity of coronavirus disease 2019 (COVID-19) symptomatic patients and clinicians' protective equipment were found to be contaminated [1]. The primary strategy for COVID-19 patients is supportive care, including oxygen therapy for hypoxaemic patients, in which high-flow nasal cannula (HFNC) has been reported to be effective in improving oxygenation. Among patients with acute hypoxaemic respiratory failure, HFNC was proven to avoid intubation compared to conventional oxygen devices [2, 3].

Bio-aerosol dispersion via high-flow nasal cannula shows a similar risk to standard oxygen masks. High-flow nasal prongs with a surgical mask on the patient's face might benefit hypoxaemic COVID-19 patients without added risk for the environment.https://bit.ly/34p7Fyy

In vitro comparison of unit dose vs infusion pump administration of albuterol via high-flow nasal cannula in toddlers

OBJECTIVES

Transnasal pulmonary aerosol delivery using high-flow nasal cannula (HFNC) devices has become a popular route of aerosol administration in toddlers. Clinically, albuterol is administered using an infusion pump or unit doses. However, little evidence is available to compare the two administration strategies.

METHODS

A toddler manikin (15 kg) with appropriate anatomic airway was connected with collecting filter to a simulator of distressed breathing. HFNC device with mesh nebulizer placed at the inlet of a humidifier at 37°C, with the gas flow set at 25 and 3.75 L/min. Five milligrams of albuterol was delivered in all experiments. With infusion pump administration, albuterol concentrations of 5 and 1 mg/mL were delivered at 4 and 20 mL/hr for 15 minutes. With unit dose administration, 1 mL (5 mg/mL) and 2 mL (2.5 mg/mL) of albuterol were nebulized. Additional tests with mouth open and nebulizers via mask were using 5 mg/1 mL for mesh nebulizer and 5 mg/3 mL for jet nebulizer (n = 3). The drug was eluted from the filter and assayed with UV spectrophotometry (276 nm).

RESULTS

The inhaled dose was higher with unit dose than infusion pump administration with gas flows of 25 L/min (2.66 ± 0.38 vs 1.16 ± 0.28%; P = .004) and 3.75 L/min (10.51 ± 1.29 vs 8.58 ± 0.68%; P = .025). During unit dose administration, compared with closed-mouth breathing, open-mouth breathing generated a higher inhaled dose at 3.75 L/min and lower inhaled dose at 25 L/min. Compared to the nebulizers via mask with both open and closed-mouth breathing, nebulization via HFNC at 3.75 L/min generated greater inhaled dose, while HFNC at 25 L/min generated lower inhaled dose.

CONCLUSIONS

During transnasal aerosol delivery, the inhaled dose was higher with medication administrated using unit dose than using an infusion pump.

In vitro comparison between inspiration synchronized and continuous vibrating mesh nebulizer during trans-nasal aerosol delivery

BACKGROUND

Compared to continuous vibrating mesh nebulizer (VMN), inspiration synchronized VMN has shown increased inhaled dose during noninvasive ventilation; however, its use during aerosol delivery via high-flow nasal cannula (HFNC) is still unknown.

METHODS

An adult manikin was connected to a dual-chamber model lung, which was driven by a critical care ventilator to simulate spontaneous breathing. A HFNC system was utilized with temperature at 37 ° C while gas flow at 5, 10, 20, 40, and 60 L/min. Inspiration synchronized and continuous aerosol generation were compared at different positions (at the inlet of humidifier vs close to patient). One milliliter of albuterol (2.5 mg/mL) was used in each run (n = 3). Collection filter was placed at the trachea and was removed after each run. Drug was eluted from the filter and assayed with UV spectrophotometry (276 nm).

RESULTS

When nebulizer was placed close to patient, inhaled dose was higher with inspiration synchronized than continuous aerosol generation at all gas flows (p = 0.05) except at 5 L/min. When placed at the inlet of humidifier, compared to continuous, inspiration synchronized aerosol generated higher inhaled dose with gas flow set below 50% of patient inspiratory flow [23.9 (20.6, 28.3)% vs 18.1 (16.7, 19.6)%, p < 0.001], but lower inhaled dose with gas flow set above 50% of patient inspiratory flow [3.5 (2.2, 9.3)% vs 9.9 (8.2, 16.4)%, p = 0.001]. Regardless of breathing pattern, continuous aerosol delivered greater inhaled dose with nebulizer placed at humidifier than close to patient at all gas flows except at 5 L/min.

CONCLUSION

When the HFNC gas flow was set higher than 50% of patient inspiratory flow, no significant advantage was found in inspiration synchronized over continuous aerosol. However, inspiration synchronized aerosol generated 30% more inhaled dose than continuous with gas flow set below 50% of patient inspiratory flow, regardless of nebulizer placement. Continuous nebulizer needs to be placed at the inlet of humidifier.

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.

In vitro evaluation of aerosol drug delivery with and without high flow nasal cannula in children

OBJECTIVE

To quantify aerosol delivery with or without a high flow nasal cannula (HFNC) in place using pressurized metered-dose inhaler (pMDI) and jet nebulizer (JN) with facemask in a simulated spontaneously breathing pediatric lung model.

METHODS

An upper airway model of a 9-month-old infant (Sophia Anatomical Infant Nose-Throat) with an absolute filter distal to the trachea was connected to a breathing simulator to simulate pediatric parameters (tidal volume = 100 mL, respiratory rate = 30 breaths/min, and I:E ratio = 1:1.4). Oxygen at 3 L/min was administered through an infant HFNC (Fisher & Paykel Healthcare Ltd, Auckland, New Zealand) attached to the nares of the model. Albuterol sulfate (2.5 mg/3 mL) was delivered with JN attached to an aerosol facemask and powered by air at 8 L/min. Ventolin Hydrofluoroalkane (HFA) (360 μg) was administered using pMDI connected to a valved holding chamber (VHC) with a facemask. Aerosol was administered to the model with and without HFNC in the nares (n = 3). Drug was eluted from the filter and quantified using spectrophotometry. Independent t tests were performed for data analysis (P < .05).

RESULTS

Aerosol deposition was greater without HFNC (6.05% ± 1.53% and 39.54% ± 8.98% for JN and pMDI/VHC, respectively) than with HFNC using JN (2.91% ± 0.23%; P = .024) and pMDI/VHC (6.04% ± 0.28%; P = .003). Delivery efficiency of pMDI/VHC was greater than JN with or without nasal cannula in place (P = .0001 and .003, respectively).

CONCLUSION

Aerosol administered via facemask over HFNC was less efficient than removing HFNC during administration. When delivering medical aerosol by facemask, the benefit of increased aerosol delivery must be weighed against the changes in oxygen delivery and risk of lung derecruitment when nasal prongs are removed.

Aerosol Delivery During Continuous High Frequency Oscillation for Simulated Adults During Quiet and Distressed Spontaneous Breathing

BACKGROUND

Continuous high-frequency oscillation (CHFO) is a therapeutic mode for the mobilization of secretions. The Metaneb CHFO device also incorporates aerosol administration using an integrated jet nebulizer. However, the effectiveness of aerosol delivery and influential factors remain largely unreported.

METHODS

A collecting filter was placed between an adult manikin with a representative upper airway and a breath simulator, set to simulate quiet and distressed patterns of spontaneous adult breathing. The Metaneb CHFO device was attached to the manikin via a mask. Two jet nebulizers were tested in 2 different positions: placement in the manifold and placement between manifold and mask. A vibrating mesh nebulizer was placed between the manifold and mask with and without extension tubing. Aerosol administration was compared during CHFO and during nebulization mode alone. Albuterol (2.5 mg in 3 mL) was nebulized for each condition. The drug was eluted from the filter and assayed with ultraviolet spectrophotometry (276 nm).

RESULTS

During CHFO, inhaled doses with jet nebulizers were low (∼ 2%), regardless of nebulizer placement. Inhaled dose was improved with the vibrating mesh nebulizer placed between the manifold and mask (12.48 ± 2.24% vs 2.58 ± 0.48%, P = .004). Inhaled doses with the jet nebulizer in the manifold with nebulization mode alone was lower than with the jet nebulizer with an aerosol mask (4.03 ± 1.82% vs 10.39 ± 2.79%, P = .004). Inhaled dose was greater with distressed breathing than quiet breathing. The use of a vibrating mesh nebulizer (P < .001) and distressed breathing (P = .001) were identified as predictors of increased inhaled dose.

CONCLUSIONS

Inhaled dose with a jet nebulizer via the Metaneb CHFO device was lower than with a jet nebulizer alone. Placement of a vibrating mesh nebulizer at the airway and distressed breathing increased inhaled dose.

Size Distribution of Colistin Delivery by Different Type Nebulizers and Concentrations During Mechanical Ventilation

Although aerosol delivery through mechanical ventilators has been used to administer various medications, little is known of administration with colistin. This in vitro evaluation aimed to evaluate size distribution of colistin delivery by different types of nebulizers and concentrations during mechanical ventilation. Colistin methanesulfonate (colistin) for injection was dissolved in 6 mL of distilled water to produce a low concentration (L; 156 mg) and a high concentration (H; 312 mg). A dose volume of 6 mL was placed in a vibrating mesh nebulizer (VMN) and a jet nebulizer (JN). The inhaled mass (mean ± SD) of the VMN-L (53.80 ± 14.79 mg) was greater than both the JN-L (19.82 ± 3.34 mg, P = 0.001) and JN-H (31.72 ± 4.48 mg, P = 0.017). The nebulization time of the VMN-L (42.35 ± 2.30 min) was two times longer than the JN-L (21.12 ± 0.8 min) or JN-H (21.65 ± 0.42 min; P < 0.001). The mass median aerodynamic distal to the endotracheal tube was within a similar range at 2.03 to 2.26 μm (P = 0.434), independent of neb or formulation concentration. In conclusion, the VMN-L yields greater inhaled mass than the JN with either concentration. Therefore, a standard nominal dose of colistin results in a higher delivered dose during mechanical ventilation with a VMN compared with a JN and may be considered the preferred device. If JN must be used, multiple doses of low concentration colistin may compensate for poor delivery performance.

Dose Response to Transnasal Pulmonary Administration of Bronchodilator Aerosols via Nasal High-Flow Therapy in Adults with Stable Chronic Obstructive Pulmonary Disease and Asthma

BACKGROUND

There has been increasing interest in transnasal pulmonary aerosol administration, but the dose-response relationship has not been reported.

OBJECTIVES

To determine the accumulative bronchodilator dose at which patients with stable mild-to-moderate asthma and chronic obstructive pulmonary disease (COPD) achieve similar spirometry responses before and after bronchodilator tests using albuterol via a metered dose inhaler with a valved holding chamber (MDI + VHC).

METHOD

Adult patients who met ATS/ERS criteria for bronchodilator responses in pulmonary function laboratory were recruited and consented to participate. After a washout period, patients received escalating doubling dosages (0.5, 1, 2, and 4 mg) of albuterol in a total volume of 2 mL delivered by vibrating mesh nebulizer via a nasal cannula at 37°C with a flow rate of 15-20 L/min using a Venturi air entrainment device. Spirometry was measured at baseline and after each dose. Titration was stopped when an additional forced expiratory volume in 1 second (FEV1) improvement was <5%.

RESULTS

42 patients (16 males) with stable mild-to-moderate asthma (n = 29) and COPD (n = 13) were enrolled. FEV1 increment after a cumulative dose of 1.5 mg of albuterol via nasal cannula at 15-20 L/min was similar to 4 actuations of MDI + VHC (0.34 ± 0.18 vs. 0.34 ± 0.12 L, p = 0.878). Using ATS/ERS criteria of the bronchodilator test, 33.3% (14/42) and 69% (29/42) of patients responded to 0.5 and 1.5 mg of albuterol, respectively.

CONCLUSIONS

With a nasal cannula at 15-20 L/min, transnasal pulmonary delivery of 1.5 mg albuterol resulted in similar bronchodilator response as 4 actuations of MDI + VHC.

Impact of Gas Flow and Humidity on Trans-Nasal Aerosol Deposition via Nasal Cannula in Adults: A Randomized Cross-Over Study

Background: Trans-nasal pulmonary aerosol delivery using high flow nasal cannula (HFNC) devices is described with the administration of high gas flows exceeding patient inspiratory flow (HF) and with lower flows (LF). The aim of this pilot clinical trial was to compare deposition and distribution of radiolabeled aerosol via nasal cannula in healthy adults across three rates of gas flow delivered with active heated humidification, and to further identify the impact of aerosol administration without heated humidity. Methods: Twenty-three (23) healthy adults (16F) were randomized to receive aerosol with active heated humidification or unheated oxygen at gas flows of 10 L/min (n = 8), 30 L/min (n = 7), or 50 L/min (n = 8). Diethylenetriaminepentaacetic acid labeled with 1 millicurie (37 MBq) of Technetium-99m (DTPA-Tc99m) was mixed with NaCl to a fill volume of 1 mL, and administered via mesh nebulizer placed at the inlet of the humidifier. Radioactivity counts were performed using a gamma camera and the regions of interest (ROIs) were delimited with counts from the lungs, upper airways, stomach, nebulizer, circuit, and expiratory filter. A mass balance was calculated and each compartment was expressed as a percentage of the total. Results: Lung deposition (mean ± SD) with heated humidified gas was greater at 10 L/min than 30 L/min or 50 L/min (17.2 ± 6.8%, 5.71 ± 2.04%, and 3.46 ± 1.24%, respectively; p = 0.0001). Using unheated carrier gas, a lung dose of aerosol was similar to the active heated humidification condition at 10 L/min, but greater at 30 and 50 L/min (p = 0.011). Administered gas flow and lung deposition were negatively correlated (r = −0.880, p < 0.001). Conclusions: Both flow and active heated humidity inversely impact aerosol delivery through HFNC. Nevertheless, aerosol administration across the range of commonly used flows can provide measurable levels of lung deposition in healthy adult subjects (NCT 02519465).

Effects of flow rate on transnasal pulmonary aerosol delivery of bronchodilators via high-flow nasal cannula for patients with COPD and asthma: protocol for a randomised controlled trial

INTRODUCTION

Both in vitro and in vivo radiolabelled studies on nebulisation via high-flow nasal cannula showed that inhaled dose decreases as the administered gas flow increases. In our previous in vitro study, we investigated the effects of the ratio of gas flow to subject's peak inspiratory flow (GF:IF) on the aerosol deposition, which increased as the GF:IF decreased, with an optimal GF:IF between 0.1 and 0.5 producing a stable 'lung' deposition in both quiet and distressed breathing. Thus, we aim to validate our in vitro findings in subjects with reversible airflow limitations by assessing their response to inhaled bronchodilator.

METHODS AND ANALYSIS

This is a single-centre, randomised controlled trial. Subjects with chronic obstructive pulmonary disease or asthma with positive response to 400μg albuterol via metered dose inhaler and valved holding chamber will be enrolled and consented. After a washout period (1-3 days), subjects will be randomly assigned to inhale albuterol with one of three gas flows: 50 L/min, GF:IF=1.0 and GF:IF=0.5. In each arm, subjects will inhale 2 mL saline, followed by escalating doubling doses (0.5, 1, 2 and 4 mg) of albuterol in a fill volume of 2 mL, delivered by a vibrating mesh nebuliser via heated nasal cannula set up at 37°C. An interval of 30 min between each dose of albuterol, with spirometry measured at baseline and after each inhalation. Titration will be terminated if forced expiratory volume in 1 s improvement is <5%, or adverse event is observed.

ETHICS AND DISSEMINATION

This trial has been approved by the Ethic Committee of People's Liberation Army General Hospital, Beijing, China (no. S2018-200-01). The results will be disseminated through peer-reviewed journals, national and international conferences.

TRIAL REGISTRATION NUMBER

NCT03739359; Pre-results.

Decrease the flow setting to improve trans-nasal pulmonary aerosol delivery via "high-flow nasal cannula" to infants and toddlers

OBJECTIVES

Trans-nasal pulmonary aerosol delivery for infants and toddlers has recently gained popularity, however, the reported lung deposition is low. We aimed to investigate the influential factors to improve the delivery.

METHODS

Anatomic airway manikins simulating infant (5 kg) and toddler (15 kg) with collecting filter connected the trachea and breath simulator, were set to represent quiet and distressed breathing. Nasal cannula flow was set at 0.125, 0.25, 0.5, 1, and 2 L/kg/min. A mesh nebulizer (Aerogen) was placed at the inlet of humidifier (Fisher & Paykel) and proximal to patient. Albuterol (5 mg in 1 mL) was nebulized for each condition (n = 3). Drug was eluted from the filter and assayed with UV spectrophotometry (276 nm).

RESULTS

Inhaled dose was higher with nebulizer placed at the inlet of humidifier than proximal to patient in all settings, except the infant model at low gas flow settings (0.125 and 0.25 L/kg/min). When nebulizer was placed at the inlet of humidifier, inhaled dose was higher when gas flow was below patient's inspiratory flow than when gas flow exceeded patient's inspiratory flow (8.77 ± 3.84 vs 2.16 ± 1.29%, P < 0.001); aerosol deposition increased as gas flow decreased, with greatest deposition at gas flow of 0.25 L/kg/min (11.29 ± 2.15%). A multiple linear regression identified gas flow as the primary predictor of aerosol delivery.

CONCLUSIONS

Trans-nasal pulmonary aerosol delivery was significantly improved when gas flow was below patient's inspiratory flow, aerosol deposition increased with decreased nasal cannula flow, with greatest deposition at 0.25 L/kg/min.

A mesh nebulizer is more effective than jet nebulizer to nebulize bronchodilators during non-invasive ventilation of subjects with COPD: A randomized controlled trial with radiolabeled aerosols

BACKGROUND

Beneficial effects from non-invasive ventilation (NIV) in acute COPD are well-established, but the impact of nebulization during NIV has not been well described.

AIM

To compare pulmonary deposition and distribution across regions of interest with administration of radiolabeled aerosols generated by vibrating mesh nebulizers (VMN) and jet nebulizer (JN) during NIV.

METHODS

A crossover single dose study involving 9 stable subjects with moderate to severe COPD randomly allocated to receive aerosol administration by the VMN Aerogen and the MistyNeb jet nebulizer operating with oxygen at 8 lpm during NIV. Radiolabeled bronchodilators (fill volume of 3 mL: 0.5 mL salbutamol 2.5 mg + 0.125 mL ipratropium 0.25 mg and physiologic saline up to 3 mL) were delivered until sputtering during NIV (pressures of 12 cmH2O and 5 cmH2O - inspiratory and expiratory, respectively) using an oro-nasal facemask. Radioactivity counts were performed using a gamma camera and regions of interest (ROIs) were delimited. Aerosol mass balance based on counts from the lungs, upper airways, stomach, nebulizer, circuit, inspiratory and expiratory filters, and mask were determined and expressed as a percentage of the total.

RESULTS

Both inhaled and lung doses were greater with VMN (22.78 ± 3.38% and 12.05 ± 2.96%, respectively) than JN (12.51 ± 6.31% and 3.14 ± 1.71%; p = 0.008). Residual drug volume was lower in VMN than in JN (3.08 ± 1.3% versus 46.44 ± 5.83%, p = 0.001). Peripheral deposition of radioaerosol was significantly lower with JN than VMN.

CONCLUSIONS

VMN deposited > 3 fold more radioaerosol into the lungs of moderate to severe COPD patients than JN during NIV.

Anatomically Based Analysis of Radioaerosol Distribution in Pulmonary Scintigraphy: A Feasibility Study in Asthmatics

INTRODUCTION

Manual analysis of two-dimensional (2D) scintigraphy to evaluate aerosol deposition is usually subjective and has reduced sensitivity to quantify regional differences between central and distal airways.

AIMS

(1) To present a method to analyze 2D scans based on three-dimensional (3D)-linked anatomically consistent regions of interest (ROIs); (2) to evaluate peripheral-to-central counts ratio (P/C_2D) and penetration indices (PIs) for a set of 16 subjects with moderate-to-severe asthma; and (3) to compare the reproducibility of this method against one with manually traced ROIs.

METHODS

Two-dimensional scans were analyzed using custom software that scaled onto 2D-projections' 3D anatomical features, obtained from population-averaged computed tomography (CT) chest scans. ROIs for a rectangular box (bROI) and an anatomically shaped ROI (aROI) were defined by computer and by manually tracing the standard rectangular box (manual ROI [mROI]). These ROIs were defined five nonconsecutive times for each scan and average value and variability of the P/C_2D were estimated. Based on CT estimates of lung and airways, volumes lying under the bROI and aROI, a 2D penetration index (PI_2D) and a 3D penetration index (PI_3D), were defined as volume-normalized ratios of aerosol deposition in central and peripheral ROIs and in central and distal airways, respectively.

RESULTS

P/C_2D values and their variability, were influenced by the shape and method to define the ROIs: The P/C_2D was systematically greater and more variable for mROI versus bROI (p < 0.005). The P/C_2D for aROI was higher and its variability lower than those for the bROI (p < 0.001). The PI_2D was in average the same for aROI and bROI, and is substantially (∼30 × ) greater than PI_3D (p < 0.001). Both PI_2D and PI_3D, obtained with our analysis, compared well with literature values obtained with two scans (deposition and volume).

CONCLUSION

Our results demonstrate that 2D scintigraphy can be analyzed using anatomically based ROIs from 3D CT data, allowing objective and enhanced reproducibility values describing the distribution pattern of radioaerosol deposition in the tracheobronchial tree.