Aerosol Therapy in Adults Receiving High Flow Nasal Cannula Oxygen Therapy

Short-acting β2 Agonist Inhalation Therapy for Asthma or Chronic Obstructive Pulmonary Disease with a High-flow Nasal Cannula in Japan -An Online Questionnaire Survey by the Japanese Respiratory Society, Japanese Society of Intensive Care Medicine, and Japanese Society of Respiratory Care Medicine

Objective Short-acting β2 agonists (SABAs) are key drugs for the treatment of asthma and chronic obstructive pulmonary disease (COPD). A high-flow nasal cannula (HFNC) is widely used for respiratory failure. Recently, a consensus statement on inhalation therapy with HFNC has been published. However, information regarding the real-world state of inhalation therapy practices in Japan is lacking. Methods An anonymous online questionnaire survey endorsed by three Japanese associations (the Japanese Respiratory Society, Japanese Society of Intensive Care Medicine, and Japanese Society of Respiratory Care Medicine) was administered from October to November 2023. Responses were stratified into three questions: Question A, "Do you routinely treat patients with asthma and COPD?" Question B "Do you routinely perform high-flow therapy?"; and Question C "How do you provide inhaled SABAs during high-flow therapy in patients with asthma or COPD?" Participants This questionnaire was distributed to all members of the three societies. Results Of the 567 participants who completed the questionnaire, 387 responded to all 3 questions. When a nebulizer was included in high-flow devices, the frequencies of using an ultrasonic nebulizer, jet, vibrating mesh, other, or not performing nebulization were 49.1%, 30.8%, 5.4%, 0.5%, and 14.2%, respectively; when a nebulizer was included in high-flow devices, these frequencies were 24.0%, 11.1%, 16.0%, 0%, and 48.9%, respectively. Conclusion Various techniques for inhalation therapy are being employed, revealing a discrepancy between current practices in Japan and the recommendations outlined in the consensus statement.

Development of an Infant Air-Jet Dry Powder Aerosol Delivery System (iDP-ADS) Including a New Multifunctional Bifurcating Two-Prong Nasal Interface

PURPOSE

To improve the quality of aerosol delivery to infants, the iDP-ADS was advanced to include dual-prong nose-to-lung aerosol administration with a bifurcating interface, consistently monitor lung pressures and control ventilatory parameters with a pressure monitoring and control (PMC) unit, and implement flexible nasal prongs for use across a range of subject sizes.

METHODS

Four bifurcating flow pathways were integrated into the iDP-ADS and tested in vitro with a full-term infant nose-throat (NT) model for comparison to the performance of a single-prong interface. After selecting the best-performing flow pathway, flexible prong designs were evaluated in the same model and chosen for additional testing. Realistic pulmonary mechanics (PM) and age-appropriate tidal volumes were used to simulate ventilation with the PMC unit and aerosol delivery in full-term and 34-week gestational age preterm NT models.

RESULTS

Three of the four bifurcating flow pathways matched the performance of the single-prong design (tracheal filter delivery of ~55%), and the FP4 design with co-flow was selected. A flexible prong version of FP4 produced similar performance to the rigid version. Measurements from the PMC unit demonstrated that consistent air volumes under safe operating pressures could be delivered with a PEEP between 4-6 cmH2O. Considering aerosol delivery, PM conditions resulted in ~4% decrease in filter deposition but high lung delivery efficiencies of ~45% and ~34% for the full-term and preterm models, respectively.

CONCLUSIONS

The best-performing interface with flexible prongs matched the lung delivery efficiency of a high-transmission single-prong interface and delivered high aerosol doses through late-preterm to full-term NT models.

Occupational agents-mediated asthma: From the perspective of autophagy

Occupational asthma (OA) is a common occupational pulmonary disease that is frequently underdiagnosed and underreported. The complexity of diagnosing and treating OA creates a significant social and economic burden, making it an important public health issue. In addition to avoiding allergens, patients with OA require pharmacotherapy; however, new therapeutic targets and strategies need further investigation. Autophagy may be a promising intervention target, but there is a lack of relevant studies summarizing the role of autophagy in OA. In this review consolidates the current understanding of OA, detailing principal and novel agents responsible for its onset. Additionally, we summarize the mechanisms of autophagy in HMW and LMW agents induced OA, revealing that occupational allergens can induce autophagy disorders in lung epithelial cells, smooth muscle cells, and dendritic cells, ultimately leading to OA through involving inflammatory responses, oxidative stress, and cell death. Finally, we discuss the prospects of targeting autophagy as an effective strategy for managing OA and even steroid-resistant asthma, encompassing autophagy interventions focused on organoids, organ-on-a-chip systems, nanomaterials vehicle, and nanobubbles; developing combined exposure models, and the role of non-classical autophagy in occupational asthma. In briefly, this review summarizes the role of autophagy in occupational asthma, offers a theoretical foundation for OA interventions based on autophagy, and identifies directions and challenges for future research.

Nasal high flow or noninvasive ventilation? navigating hypercapnic COPD exacerbation treatment: A randomized noninferiority clinical trial

BACKGROUND

Noninvasive ventilation (NIV) has been the cornerstone for managing acute exacerbations of COPD (AECOPD) with hypercapnic respiratory failure. Nasal high flow (NHF) oxygen therapy has emerged as a potential alternative, offering a more tolerable modality with promising outcomes. The aim of the present study was to evaluate whether NHF respiratory support is noninferior to NIV with respect to treatment failure, in patients with mild-to-moderate hypercapnic AECOPD.

METHODS

In this multi-center, randomized, noninferiority trial, 105 patients with AECOPD and respiratory failure type II were enrolled. Participants were randomly assigned to receive either NHF therapy or NIV. The primary endpoint was the frequency of treatment failure, defined as the need for intubation and invasive mechanical ventilation or a switch to the alternative treatment group. Secondary endpoints included changes in respiratory parameters, patient comfort indicators, and the occurrence of complications.

RESULTS

The findings revealed no significant difference in the primary outcome between the groups, with a treatment failure rate of 19.6 % (10 out of 51) in the NHF group and 14.8 % (8 out of 54) in the NIV group. Interestingly, NHF users reported significantly lower levels of dyspnea and discomfort at multiple follow-up points. Despite the differences in patient comfort, respiratory parameters such as respiratory rate, arterial blood gases, and use of accessory muscles of respiration showed no significant disparities between the groups throughout the study period.

CONCLUSIONS

NHF therapy was similar to NIV in preventing treatment failure among patients with hypercapnic AECOPD, offering a viable alternative with enhanced comfort.

TRIAL REGISTRATION

The study was prospectively registered in ClinicalTrials.gov (Identifier: NCT03466385) on March 15, 2018.

Dos and don'ts to optimize transnasal aerosol drug delivery in clinical practice

INTRODUCTION

Transnasal aerosol drug delivery has become widely accepted for treating acutely ill infants, children, and adults. More recently aerosol administration to wider populations receiving high and low-flow nasal oxygen has become common practice.

AREAS COVERED

Skepticism of insufficient aerosol delivery to the lungs has been tempered by multiple in vitro explorations of variables to optimize delivery efficiency. Additionally, clinical studies demonstrated comparable clinical responses to orally inhaled aerosols. This paper provides essential clinical guidance on how to improve transnasal aerosol delivery based on device-, settings-, and drug-related optimization to serve as a resource for educational initiatives and quality enhancement endeavors at healthcare institutions.

EXPERT OPINION

Transnasal aerosol delivery is proliferating worldwide, but indiscriminate use of excessive-high flows, poor selection and placement of aerosol devices and circuits can greatly reduce aerosol delivery and efficacy, potentially compromising treatment to acute and critically ill patients. Attention to these details can improve inhaled dose by an order of magnitude, making the difference between effective treatment and the progression to more invasive ventilatory support, with greater inherent risk and cost. These revelations have prompted specific recommendations for optimal delivery, driving advancements in aerosol generators, formulations, and future device designs to administer aerosols and maximize treatment effectiveness.

In-Line Aerosol Therapy via Nasal Cannula during Adult and Paediatric Normal, Obstructive, and Restrictive Breathing

High-flow nasal oxygen therapy is being increasingly adopted in intensive and home care settings. The concurrent delivery of aerosolised therapeutics allows for the targeted treatment of respiratory illnesses. This study examined in-line aerosol therapy via a nasal cannula to simulated adult and paediatric models with healthy, obstructive and restrictive lung types. The Aerogen Solo vibrating mesh nebuliser was used in combination with the InspiredTM O2FLO high-flow therapy system. Representative adult and paediatric head models were connected to a breathing simulator, which replicated several different states of lung health. The aerosol delivery was quantified at the tracheal level using UV-spectrophotometry. Testing was performed at a range of supplemental gas flow rates applicable to both models. Positive end-expiratory pressure was measured pre-, during and post-nebulisation. The increases in supplemental gas flow rates resulted in a decrease in aerosol delivery, irrespective of lung health. Large tidal volumes and extended inspiratory phases were associated with the greatest aerosol delivery. Gas flow to inspiratory flow ratios of 0.29-0.5 were found to be optimum for aerosol delivery. To enhance aerosol delivery to patients receiving high-flow nasal oxygen therapy, respiratory therapists should keep supplemental gas-flow rates below the inspiratory flow of the patient.

Aerosol delivery through high-flow nasal therapy: Technical issues and clinical benefits

High-flow nasal cannula (HFNC) therapy is an oxygen delivery method particularly used in patients affected by hypoxemic respiratory failure. In comparison with the conventional "low flow" oxygen delivery systems, it showed several important clinical benefits. The possibility to nebulize drugs via HFNC represents a desirable medical practice because it allows the administration of inhaled drugs, mostly bronchodilators, without the interruption or modification of the concomitant oxygen therapy. HFNC, by itself has shown to exert a small but significant bronchodilator effect and improves muco-ciliary clearance; thus, the nebulization of bronchodilators through the HFNC circuit may potentially increase their pharmacological activity. Several technical issues have been observed which include the type of the nebulizer that should be used, its position within the HFNC circuit, and the optimal gas flow rates to ensure an efficient drug delivery to the lungs both in "quiet" and "distressed" breathing patterns. The aim of this review has been to summarize the scientific evidence coming from "in vitro" studies and to discuss the results of "in vivo" studies performed in adult subjects, mainly affected by obstructive lung diseases. Most studies seem to indicate the vibrating mesh nebulizer as the most efficient type of nebulizer and suggest to place it preferentially upstream from the humidifier chamber. In a quite breathing patterns, the inhaled dose seems to increase with lower flow rates while in a "distressed" breathing pattern, the aerosol delivery is higher when gas flow was set below the patient's inspiratory flow, with a plateau effect seen when the gas flow reaches approximately 50% of the inspiratory flow. Although several studies have demonstrated that the percentage of the loaded dose nebulized via HFNC reaching the lungs is small, the bronchodilator effect of albuterol seems not to be impaired when compared to the conventional inhaled delivery methods. This is probably attributed to its pharmacological activity. Prospective and well-designed studies in different cohort of patients are needed to standardize and demonstrate the efficacy of the procedure.

Aerosol release, distribution, and prevention during aerosol therapy: a simulated model for infection control

Aerosol therapy is used to deliver medical therapeutics directly to the airways to treat respiratory conditions. A potential consequence of this form of treatment is the release of fugitive aerosols, both patient derived and medical, into the environment and the subsequent exposure of caregivers and bystanders to potential viral infections. This study examined the release of these fugitive aerosols during a standard aerosol therapy to a simulated adult patient. An aerosol holding chamber and mouthpiece were connected to a representative head model and breathing simulator. A combination of laser and Schlieren imaging was used to non-invasively visualize the release and dispersion of fugitive aerosol particles. Time-varying aerosol particle number concentrations and size distributions were measured with optical particle sizers at clinically relevant positions to the simulated patient. The influence of breathing pattern, normal and distressed, supplemental air flow, at 0.2 and 6 LPM, and the addition of a bacterial filter to the exhalation port of the mouthpiece were assessed. Images showed large quantities of fugitive aerosols emitted from the unfiltered mouthpiece. The images and particle counter data show that the addition of a bacterial filter limited the release of these fugitive aerosols, with the peak fugitive aerosol concentrations decreasing by 47.3-83.3%, depending on distance from the simulated patient. The addition of a bacterial filter to the mouthpiece significantly reduces the levels of fugitive aerosols emitted during a simulated aerosol therapy, p≤ .05, and would greatly aid in reducing healthcare worker and bystander exposure to potentially harmful fugitive aerosols.

In Vitro Evaluation of Nebulized Pharmaceutical Aerosol Delivery to the Lungs Using a New Heated Dryer System (HDS)

The objective of this study was to develop a new heated dryer system (HDS) for high efficiency lung delivery of nebulized aerosol and demonstrate performance with realistic in vitro testing for trans-nasal aerosol administration simultaneously with high-flow nasal cannula (HFNC) therapy and separately for direct oral inhalation (OI) of the aerosol. With the HDS-HFNC and HDS-OI platforms, new active synchronization control routines were developed to sense subject inhalation and coordinate drug aerosol delivery. In vitro experiments were conducted to predict regional drug loss and lung delivery efficiency in systems that included the HDS with various patient interfaces, realistic airway models, and simulated breathing waveforms. For the HDS-HFNC platform and a repeating breathing waveform, total system loss was < 10%, extrathoracic deposition was approximately 6%, and best-case lung delivery efficiency was 75-78% of nebulized dose. Inclusion of randomized breathing with the HFNC system decreased lung delivery efficiency by ~ 10% and had no impact on nasal depositional loss. For the HDS-OI platform and best-case mouthpiece, total system loss was < 8%, extrathoracic deposition was < 1%, and lung delivery efficiency was > 90% of nebulized dose. Normal vs. deep randomized oral inhalation had little impact on performance of the HDS-OI platform and environmental aerosol loss was negligible. In conclusion, both platforms demonstrated the potential for high efficiency lung delivery of the aerosol with the HDS-OI platform having the added advantages of nearly eliminating extrathoracic deposition, being insensitive to breathing waveform, and preventing environmental aerosol loss.

In Vitro Characterization of Aerosolized Albuterol Generated by a Jet Nebulizer and Delivered through a Heated Flow Nasal Cannula System

Pediatric patients receiving respiratory support with heated flow nasal cannula (HFNC) systems frequently receive inhaled medications. Most available data have been obtained with vibrating mesh nebulizers that are expensive. Data are lacking regarding the feasibility of using less expensive devices such as continuous output jet nebulizers. The characteristics of the aerosols generated by jet nebulizers operated at different conditions (6 and 9 L/min) were studied alone and connected to a HFNC system and different size cannulas using a cascade impactor and spectrophotometry (276 nm). Aerosol characteristics changed while traveling through the HFNC system. Initial size selection occurred at the exit of the circuit (before connecting to the cannula) with all aerosol <5 µm. Nasal cannula size further selected aerosols and reduced drug delivery. The operating flow of the nebulizer did not affect the delivered mass but higher flows generated smaller particle size aerosols. The addition of supplemental flow significantly reduced the delivered mass. The measured aerosol characteristics would likely result in intrapulmonary deposition. The delivery of aerosolized albuterol generated by a continuous output nebulizer placed in the inlet of a HFNC system and connected to large or XXL cannulas is feasible.

[Can mesh nebulizers improve prehospital aerosol therapy? An in vitro study on simulated prehospital emergency patients suffering from respiratory distress]

BACKGROUND

Nebulizers used to treat prehospital emergency patients should provide a high output efficiency to achieve a fast onset of therapeutic drug effects while remaining unaffected by the presence of supplementary oxygen flow or the patient's breathing pattern. On the other hand, nebulizer performance is directly influenced by differences in device design, gas flow and patients' breathing patterns. Several studies from emergency departments were able to demonstrate an improvement in patient outcome when using a mesh nebulizer instead of a jet nebulizer. Data or bench studies regarding prehospital care are non-existent.

OBJECTIVE

The aim of the present in vitro study was to evaluate which type of aerosol generator would best address the requirements of a prehospital adult emergency patient suffering from respiratory distress.

MATERIAL AND METHODS

We evaluated the performance of a jet nebulizer (Cirrus™ 2, Intersurgical®) and two mesh nebulizers (Aerogen Solo® with USB controller, Aerogen Limited and M‑Neb® mobile, NEBU-TEC International med. Produkte Eike Kern GmbH) with the possibility of portable operation in an in vitro model of a spontaneously breathing adult emergency patient. One physiological and three pathological breathing patterns (distressed breathing pattern as well as stable and acute exacerbated chronic obstructive pulmonary disease) were simulated. Nebulizer output and salbutamol lung deposition were measured at different oxygen flow rates using a face mask as the delivery interface.

RESULTS

The mesh nebulizers produced a significantly higher aerosol output when compared to the jet nebulizer. The M‑Neb® mobile was able to significantly exceed the output of the Aerogen Solo®. Oxygen flow had the largest influence on the output of the jet nebulizer but hardly affected the mesh nebulizers. After a nebulization time of 10 min the M‑Neb® mobile also achieved the highest total salbutamol lung deposition (P < 0.001). Aerosol drug deposition was therefore mainly determined by the nebulizer's drug output per unit time. The deposition could not be improved using a spacer but was strongly influenced by the simulated emergency patients' breathing pattern.

CONCLUSION

The use of mesh nebulizers might have the potential to improve the aerosol therapy of prehospital emergency patients. In general, mesh nebulizers seem to be superior to jet nebulizers regarding aerosol output per unit time and total lung deposition. The present data suggest that aerosol output and drug deposition to the collection filter in this simulated setting are closely connected and crucial for total salbutamol deposition, as the deposition could not be improved by adding a spacer. Aerosol drug deposition in simulated emergency patients' lungs is therefore mainly determined by the nebulizer's drug output per unit time. The level of oxygen flow used had the largest influence on the output of the jet nebulizer but hardly affected the output of the tested mesh nebulizers. Mesh nebulizers could therefore enable a demand-adapted oxygen therapy due to their consistent performance despite the presence of oxygen flow. A high respiratory rate was associated with a high drug deposition, which is clinically desirable in the treatment of patients in respiratory distress; however, drug underdosing must also be expected in the treatment of bradypneic patients. Further clinical studies must prove whether our findings also apply to the treatment of real prehospital emergency patients.

Aqueous dispersions of oxygen nanobubbles for potential application in inhalation therapy

Inhalation is a non-invasive method of local drug delivery to the respiratory system. This study analyzed the potential use of aqueous dispersion of oxygen nanobubbles (ADON) as a drug carrier with the additional function of oxygen supplementation to diseased lungs. The suitability of the membrane-based method of ADON preparation and, next, the stability of ADON properties during storage and after aerosolization in nebulizers of various designs (jet, ultrasonic, and two vibrating mesh devices) was investigated. The increased oxygen content in the aerosol generated in two mesh nebulizers suggests that the proposed concept may be helpful in the oxygen supplementation during drug delivery by aerosol inhalation without using an additional oxygen source. This application can increase the overall effectiveness of lung disease treatment and pulmonary rehabilitation.

High-Flow Nasal Cannula Oxygen Therapy: Physiological Mechanisms and Clinical Applications in Children

High-flow nasal cannula (HFNC) oxygen therapy has rapidly become a popular modality of respiratory support in pediatric care. This is undoubtedly due to its ease of use and safety, which allows it to be used in a wide variety of settings, ranging from pediatric intensive care to patients' homes. HFNC devices make it possible to regulate gas flow and temperature, as well as allowing some nebulized drugs to be administered, features very useful in children, in which the balance between therapeutic effectiveness and adherence to treatment is pivotal. Although the physiological effects of HFNC are still under investigation, their mechanisms of action include delivery of fixed concentration of oxygen, generation of positive end-expiratory pressure, reduction of the work of breathing and clearance of the nasopharyngeal dead space, while providing optimal gas conditioning. Nevertheless, current evidence supports the use of HFNC mainly in moderate-to-severe bronchiolitis, whereas for asthma exacerbations and breath sleeping disorders there is a lack of randomized controlled trials comparing HFNC to continuous positive airway pressure (CPAP) and non-invasive ventilation (NIV), which are essentials for the identification of response and non-response predictors. In this regard, the development of clinical guidelines for HFNC, including flow settings, indications, and contraindications is urgently needed.

Effect of pressures and type of ventilation on aerosol delivery to chronic obstructive pulmonary disease patients

Background

Continuous Positive Airway Pressure (CPAP), BiPhasic Positive Airway Pressure (BiPAP), and high flow nasal cannula (HFNC) show some evidence to have efficacy in COVID-19 patients. Delivery during noninvasive mechanical ventilation (NIV) or HFNC gives faster and more enhanced clinical effects than when aerosols are given without assisted breath. The present work aimed to compare the effect of BiPhasic Positive Airway Pressure (BiPAP) mode at two different pressures; low BiPAP (Inspiratory Positive Airway Pressure (IPAP)/Expiratory Positive Airway Pressure (EPAP) of 10/5 cm water) and high BiPAP (IPAP/EPAP of 20/5 cm water), with HFNC system on pulmonary and systemic drug delivery of salbutamol. On the first day of the experiment, all patients received 2500 μg salbutamol using Aerogen Solo vibrating mesh nebulizer. Urine samples 30 min post-dose and cumulative urinary salbutamol during the next 24 h were collected on the next day. On the third day, the ex-vivo filter was inserted before the patient to collect the delivered dose to the patient of the 2500 μg salbutamol. Salbutamol was quantified using high-performance liquid chromatography (HPLC).

Results

Low-pressure BiPAP showed the highest amount delivered to the lung after 30 min followed by HFNC then high-pressure BiPAP. But the significant difference was only observed between low and high-pressure BiPAP modes (p = 0.012). Low-pressure BiPAP showed the highest delivered systemic delivery amount followed by HFNC then high-pressure BiPAP. Low-pressure BiPAP was significantly higher than HFNC (p = 0.017) and high-pressure BiPAP (p = 0.008). No significant difference was reported between HFNC and high-pressure BiPAP. The ex-vivo filter was the greatest in the case of low-pressure BiPAP followed by HFNC then high-pressure BiPAP. Low-pressure BiPAP was significantly higher than HFNC (p = 0.033) and high-pressure BiPAP (p = 0.008). Also, no significant difference was found between HFNC and high-pressure BiPAP.

Conclusions

Our results of pulmonary, systemic, and ex-vivo drug delivery were found to be consistent. The low BiPAP delivered the highest amount followed by the HFNC then the high BiPAP with the least amount. However, no significant difference was found between HFNC and high BiPAP.

Nebulizer particle size distribution measured by various methods

Pari LC Sprint Star nebulizer is an inhaler device dedicated to delivering the liquid drug formulation into peripheral lung regions. The particle size is one of the critical parameters which determine the location of aerosol deposition within the human lungs. In this study, the particle size distribution of aerosol was measured by two different methods: Andersen Cascade Impactor (ACI) and Aerodynamic Particle Sizer (APS). Mass Median of Aerodynamic Distribution (MMAD), and Geometric Standard Deviation (GSD) were evaluated. MMAD gained by APS was approx. 7 µm, MMAD acquired by ACI was approx. 2.5 µm. According to the results, these two measuring methods are not very consistent, and the comparison of the particle size acquired by the different methods is not appropriate.

The Impact of Head Model Choice on the In Vitro Evaluation of Aerosol Drug Delivery

There are variations in the values reported for aerosol drug delivery across in vitro experiments throughout the published literature, and often with the same devices or similar experimental setups. Factors contributing to this variability include, but are not limited to device type, equipment settings, drug type and quantification methods. This study assessed the impact of head model choice on aerosol drug delivery using six different adults and three different paediatric head models in combination with a facemask, mouthpiece, and high-flow nasal cannula. Under controlled test conditions, the quantity of drug collected varied depending on the choice of head model. Head models vary depending on a combination of structural design differences, facial features (size and structure), internal volume measurements and airway geometries and these variations result in the differences in aerosol delivery. Of the widely available head models used in this study, only three were seen to closely predict in vivo aerosol delivery performance in adults compared with published scintigraphy data. Further, this testing identified the limited utility of some head models under certain test conditions, for example, the range reported across head models was aerosol drug delivery of 2.62 ± 2.86% to 37.79 ± 1.55% when used with a facemask. For the first time, this study highlights the impact of head model choice on reported aerosol drug delivery within a laboratory setting and contributes to explaining the differences in values reported within the literature.

Aerosol delivery through high flow nasal cannula compared to biphasic positive airway pressure, at two different pressure: an in-vitro study

Background

Both non-invasive ventilation and high flow oxygen therapy are preferred over low flow oxygen therapy in many conditions. Nebulizers, for aerosol delivery, can be used within them without interrupting the circuit. The present study aimed to compare the efficiency of drug delivery within high flow nasal cannula (HFNC) and biphasic positive airway pressure (BiPAP) ventilation mode using two different inspiratory positive airway pressures. The aerosol delivery was examined in HFNC system at low flow, 5 L min−1, and BiPAP non-invasive ventilation under 2 different pressures [high pressure; inspiratory positive airway pressure/expiratory positive airway pressure (IPAP/EPAP) of 20/5 cm water, and low pressure; IPAP/EPAP of 10/5 cm water]. The total inhalable dose (TID) was measured by inserting an Aerogen Solo nebulizer installed with 1 mL salbutamol respiratory solution (5000 μg mL−1) within the circuit, and the salbutamol was collected on an inhalation filter placed in a filter holder connected to a breathing simulator. The breathing simulator was adjusted at a tidal volume of 500 mL, respiratory rate of 15 breaths min−1, and inhalation to exhalation (I:E) ratio of 1:1 for the adult setting. In each technique of the three (HFNC, and low, and high-pressures BiPAP), TID was determined 5 times (n = 5). For particle size characterization, cooled Anderson Cascade Impactor (ACI) was inserted instead of the inhalation filter and the breathing simulator with the same scheme. In each technique of the three, particle size characterization was determined 3 times (n = 3).

Results

The BiPAP mode at low inspiratory pressure had the highest TID, followed by HFNC at flow 5 L min−1, then BiPAP mode at high inspiratory pressure. There was a significant difference only between low and high inspiratory pressure modes of BiPAP mode. Low-inspiratory pressure BiPAP delivered the highest mean ± SD fine particle dose (FPD). It was significantly higher than that delivered in high inspiratory pressure BiPAP, and HFNC. Also, FPD in HFNC was significantly higher than that in high inspiratory pressure BiPAP. HFNC system had the smallest mass median aerodynamic diameter (MMAD) and the highest FPF followed by low then high inspiratory pressure BiPAP.

Conclusions

Increasing the inspiratory positive airway pressure in BiPAP, from 10 to 20 cm water, decreased the total inhalable dose and FPF nearly by half. Low inspiratory pressure BiPAP delivered the highest TID and FPD. The HFNC system at low oxygen flow resulted in the least MMAD, and the highest FPF. Using HFNC delivered a TID that was non-significant from that delivered by low inspiratory pressure BiPAP.

Graphical Abstract

Bronchodilator Delivery via High-Flow Nasal Cannula: A Randomized Controlled Trial to Compare the Effects of Gas Flows

(1) Background: Aerosol delivery via high-flow nasal cannula (HFNC) has attracted increasing clinical interest. In vitro studies report that the ratio of HFNC gas flow to patient inspiratory flow (GF:IF) is a key factor in the efficiency of trans-nasal aerosol delivery. (2) Methods: In a randomized controlled trial, patients with a history of COPD or asthma and documented positive responses to inhaled bronchodilators in an outpatient pulmonary function laboratory were recruited. Subjects were randomized to receive inhalation at gas flow ratio settings of: GF:IF = 0.5, GF:IF = 1.0, or GF = 50 L/min. Subjects were assigned to inhale saline (control) followed by salbutamol via HFNC with cumulative doses of 0.5 mg, 1.5 mg, 3.5 mg, and 7.5 mg. Spirometry was performed at baseline and 10-12 min after each inhalation. (3) Results: 75 subjects (49 asthma and 26 COPD) demonstrating bronchodilator response were enrolled. Per the robust ATS/ERS criteria no difference was observed between flows, however using the criteria of post-bronchodilator forced expiratory volume in the first second (FEV₁) reaching the screening post-bronchodilator FEV₁ with salbutamol, a higher percentage of subjects receiving GF:IF = 0.5 met the criteria at a cumulative dose of 1.5 mg than those receiving GF:IF = 1.0, and GF = 50 L/min (64% vs. 29% vs. 27%, respectively, p = 0.011). Similarly at 3.5 mg (88% vs. 54% vs. 46%, respectively, p = 0.005). The effective dose at GF:IF = 0.5 was 1.5 mg while for GF = 50 L/min it was 3.5 mg. (4) Conclusions: During salbutamol delivery via HFNC, cumulative doses of 1.5 mg to 3.5 mg resulted in effective bronchodilation. Applying the robust ATS/ERS criteria no difference was observed between the flows, however using the more sensitive criteria of subjects reaching post screening FEV₁ to salbutamol via HFNC, a higher number of subjects responded to the doses of 0.5 mg and 1.5 mg when HFNC gas flow was set at 50% of patient peak inspiratory flow.

The impact of changing patient interfaces on delivering aerosol with titrated oxygen in the high flow system

INTRODUCTION

Despite the widespread oxygen-culture as more is better in prehospital and hospital settings, the use of titrated oxygen-flow within a high-flow system can be beneficial especially when combined with aerosol-delivery and also save the patient from unnecessary-hyperoxia.

METHODS

Forty-five COPD patients were included in this study where they allocated in three-groups (nasal-delivery, oral-delivery, and oronasal-delivery groups). All patients were received their inhaled-salbutamol dose using Aerogen Solo nebuliser by one of the three interfaces, eg, nasal-cannula, mouthpiece, and facemask in two conditions; with oxygen-flow and without any oxygen-flow. Pulmonary and systemic salbutamol deposition was estimated by collecting two urine-samples from the patient; 30 min post-inhalation and cumulatively 24 hr post-inhalation. The quantity of salbutamol in these collected samples was measured by high-performance liquid chromatography. Lung function measurement was performed pre-bronchodilator inhalation and 30 min post-bronchodilator to estimate the change in pulmonary functions post-inhalation regarding all tested interfaces.

RESULTS

COPD patients showed the highest salbutamol percentage excreted 30 min post-inhalation of 5.7% (1.4) with mouthpiece interface when combined with oxygen at P < .002. While with the same condition using oxygen, valved-facemask showed the highest salbutamol percentage excreted in 24 hr post inhalation samples but the difference is only significantly compared with nasal cannula (P < .006). Moreover, without oxygen delivery, mouthpiece and valved facemask showed approximately the same salbutamol percentage excreted in 30 min post-inhalation samples, higher than that delivered by nasal cannula (P < .001). Of note, salbutamol delivery is significantly increased with oxygen flow for all interfaces (P < .05) except with nasal cannula.

CONCLUSIONS

The nasal cannula is a more comfortable and tolerable interface despite the lower fraction of the delivered drug compared with other tested interfaces. The use of oxygen-flow with aerosol delivery within a high flow system positively affects the delivered drug fraction and the pulmonary deposition of the drug.

Application of aerosol therapy in respiratory diseases in children: A Saudi expert consensus

The Saudi Pediatric Pulmonology Association (SPPA) is a subsidiary of the Saudi Thoracic Society (STS), which consists of a group of Saudi experts with well-respected academic and clinical backgrounds in the fields of asthma and other respiratory diseases. The SPPA Expert Panel realized the need to draw up a clear, simple to understand, and easy to use guidance regarding the application of different aerosol therapies in respiratory diseases in children, due to the high prevalence and high economic burden of these diseases in Saudi Arabia. This statement was developed based on the available literature, new evidence, and experts' practice to come up with such consensuses about the usage of different aerosol therapies for the management of respiratory diseases in children (asthma and nonasthma) in different patient settings, including outpatient, emergency room, intensive care unit, and inpatient settings. For this purpose, SPPA has initiated and formed a national committee which consists of experts from concerned specialties (pediatric pulmonology, pediatric emergency, clinical pharmacology, pediatric respiratory therapy, as well as pediatric and neonatal intensive care). These committee members are from different healthcare sectors in Saudi Arabia (Ministry of Health, Ministry of Defence, Ministry of Education, and private healthcare sector). In addition to that, this committee is representing different regions in Saudi Arabia (Eastern, Central, and Western region). The subject was divided into several topics which were then assigned to at least two experts. The authors searched the literature according to their own strategies without central literature review. To achieve consensus, draft reports and recommendations were reviewed and voted on by the whole panel.

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.

A path to successful patient outcomes through aerosol drug delivery to children: a narrative review

Although using aerosolized medications is a mainstay of treatment in children with asthma and other respiratory diseases, there are many issues in terms of device and interface selection, delivery technique and dosing, as well as patient and parental education that have not changed for half a century. Also, due to many aerosol devices and interfaces available on the market and the broad range of patient characteristics and requirements, providing effective aerosol therapy to children becomes a challenge. While aerosol delivery devices are equally effective, if they are age-appropriate and used correctly, the majority of aerosol devices require multiple steps to be used efficiently. Unfortunately, many children with pulmonary diseases have problems with the correct delivery technique and do not gain therapeutic benefits from therapy that result in poor disease management and increased healthcare costs. Therefore, the purpose of this paper is to review the current knowledge on aerosol delivery devices used in children and guide clinicians on the optimum device- and interface-selection, delivery technique, and dosing in this patient population. Strategies on how to deliver aerosolized medications in crying and distressed children and how to educate parents on aerosol therapy and promote patient adherence to prescribed medications are also provided. Future directions of aerosol therapy in children should focus on these issues and implement policies and clinical practices that highlight the potential solutions to these problems.

Pressurized Metered Dose Inhaler Aerosol Delivery Within Nasal High-Flow Circuits: A Bench Study

Background: Obstructive patients may benefit from nasal high-flow (NHF) therapy, but the use of pressurized metered-dose inhalers (pMDIs) has not been evaluated in this situation. Methods: Using an adult circuit and medium-sized cannula, we have tested different NHF rates, pMDI positions, breathing patterns, spacers, and spacer orientation. First, we evaluated albuterol delivery at the nasal cannula outlet. The second set of experiments made use of a nasopharyngeal cast to estimate the mass of albuterol potentially reaching the lungs. Albuterol was caught on filters placed at the cannula outlet and downstream of the nasal cast, and albuterol was quantified by spectrophotometry. Results: The highest amounts of albuterol delivered at the cannula outlet were observed with a 30 L/min flow rate (vs. 45 and 60 L/min) and placing the device close to the nasal cannula (in comparison with a position on the dry side of the humidification chamber). The use of a spacer was associated with higher delivery. The highest albuterol delivery was observed placing the spacer close to the nasal cannula, oriented for aerosol delivery following the gas flow and a 30 L/min NHF rate. Using this optimal setting, activating the pMDI at the beginning of inspiration (compared to expiration) increased albuterol delivery downstream of the nasopharyngeal cast. Whether in a quiet- or distress-breathing pattern, our measurements showed an amount of albuterol potentially delivered to the lungs exceeding 10% of the actuated dose in optimal conditions. Conclusions: The use of pMDIs is feasible to deliver albuterol within a NHF circuit. Using a spacer placed just upstream from the nasal cannulas, a low NHF rate and activating the pMDI at the beginning of inspiration was associated with drug delivery susceptible to induce bronchodilation, which will require to be tested in the clinical setting.

How to deliver aerosolized medications through high flow nasal cannula safely and effectively in the era of COVID-19 and beyond: A narrative review

Background

The treatments of COVID-19 involve some degree of uncertainty. Current evidence also shows mixed findings with regards to bioaerosol dispersion and airborne transmission of COVID-19 during high flow nasal cannula (HFNC) therapy. While coping with this global pandemic created hot debates on the use of HFNC, it is important to bring detached opinions and current evidence to the attention of health care professionals (HCPs) who may need to use HFNC in patients with COVID-19.

Aim

The purpose of this paper is to provide a framework on the selection, placement, and use of nebulizers as well as HFNC prongs, gas flow, and delivery technique via HFNC to help clinicians deliver aerosolized medications through HFNC safely and effectively in the era of COVID-19 and beyond.

Methods

We searched PubMed, Medline, CINAHL, and Science Direct to identify studies on aerosol drug delivery through HFNC using the following keywords: (“aerosols,” OR “nebulizers”) AND (“high flow nasal cannula” OR “high flow oxygen therapy” OR “HFNC”) AND (“COVID-19,” OR “SARS-CoV-2”). Twenty-eight articles including in vitro studies, randomized clinical trials, scintigraphy studies, review articles, prospective and retrospective research were included in this review.

Discussion and results

It is not clear if the findings of the previous studies on bacterial contamination could be applied to viral transmission because they do not provide data that could be extrapolated to the risk of SARS-CoV-2 transmission. In the face of the unknown risk with the transmission of COVID-19 during HFNC therapy, the benefits of HFNC must be weighed against the risk of infection to HCPs and other patients. Due to the limited number of ventilators available in hospitals and the confirmed effectiveness of HFNC in treating hypoxemic respiratory failure, HFNC may prevent early intubation, and prolonged intensive care unit stays in patients with COVID-19.

Conclusion

Clinicians should review the magnitude of this risk based on current evidence and use the suggested strategies of this paper for safe and effective delivery of aerosolized medications through HFNC in the era of COVID-19 and beyond.

Droplet Size and Distribution of Nebulized 3% Sodium Chloride, Albuterol, and Epoprostenol by Phase Doppler Particle Analyzer

Background

Aerosolized drug therapy administered to mechanically ventilated patients is a standard part of pulmonary critical care medicine. Aerosol particle size and distribution are important factors in the optimal delivery of aerosolized drugs to ventilated patients.

Objective

The objective of this study was to characterize aerosol droplet size and distribution with laser diffraction for nebulized 3% sodium chloride, albuterol, and epoprostenol sodium (containing glycine) delivered via Aeroneb Solo Mesh Nebulizers (Aerogen, Mountain View, California).

Methods

A series of functional flow tests were run on each of 8 Solo mesh nebulizers before the study to verify accuracy of flow rates in milliliters per minute. Aerosolized droplets exiting the nebulizer heads were then measured using a phase Doppler particle analyzer. Data collected during delivery of 3% sodium chloride, albuterol, and epoprostenol sodium included aerosol droplet size distribution, mass median aerodynamic diameter (MMAD), and geometric standard deviation. For each Solo nebulizer, droplet size measurements were taken 2 cm away from the nebulizer head and 2 cm away from the wye of a heated, humidified adult ventilator circuit. For measurements taken at the wye, 4 distinct, continuous flow rates (2, 10, 20, and 40 L/min) were generated by an air pump to simulate inspiratory flows delivered with mechanical ventilation. The expiratory limb was capped, and the nebulizer head was inserted into the breathing circuit upstream of the humidifier.

Results

Each Solo nebulizer met Aerogen's recommended minimum flow rate of 0.2 mL/min, ranging from 0.23 to 0.31 mL/min. The MMAD of the 3 tested aerosols was several times smaller when measured at the wye outlet of the heated/humidified breathing circuit (0.82–2.73 µm) compared with droplets measured directly at the nebulizer outlet (MMAD, 4.6–7.3 µm). There was also significant variability across Solo heads with some ventilator flow rates. The mean MMAD at the wye for the 3% sodium chloride solution, albuterol, and epoprostenol test solutions was 1.62 µm, 1.09 µm, and 1.18 µm, respectively. The mean MMAD at the nebulizer for the 3% sodium chloride solution, albuterol, and epoprostenol test solutions was 5.37 µm, 5.73 µm, and 6.73 µm, respectively.

Conclusions

Results from this study suggest that particle size of aerosolized drugs administered via a commonly used setup for delivery of in-line aerosols to mechanically ventilated patients may be several times smaller than expected and may result in less drug being delivered to the patient than previously realized.

(Curr Ther Res Clin Exp. 2021; 82:XXX–XXX)

© 2021 Elsevier HS Journals, Inc.

Aerosol delivery aspects within a high-flow therapy system in COPD patients

There is a lack of information about the influence of patient interfaces such as facemasks or mouthpieces on the effective dose of aerosolised drugs while using high-flow therapy in a clinical setting. These interfaces can improve pulmonary drug delivery over nasal cannulas but patient preference and comfort should also be considered.

The present work was to determine the effect of three different interfaces (nasal cannula, valved face mask, and mouthpiece) when combined with titrated oxygen flow on aerosol delivery in patients with COPD hospitalised due to acute exacerbation.

The variations between these interfaces were addressed in terms of change in lung function measurements pre-and post-inhalation, the delivered salbutamol dose, and patient tolerance to each interface.

A high-flow nasal cannula was the most comfortable interface used. However, its pulmonary drug delivery was significantly lower than both the valved face mask and mouthpiece (p<0.05). Although drug delivery was different with the three tested interfaces, the lung function improvements were similar.

Delivery in high-flow therapy with a different interfacehttps://bit.ly/3l7MJUb

Nasal high-flow oxygen versus noninvasive ventilation in acute exacerbation of COPD: protocol for a randomised noninferiority clinical trial

Background

Noninvasive ventilation (NIV) is considered as the first-line treatment for acute exacerbation of COPD (AECOPD) complicated by respiratory acidosis. Recent studies demonstrate a role of nasal high-flow oxygen (NHF) in AECOPD as an alternative treatment in patients intolerant to NIV or with contraindications to it.

Aim

The study aimed to evaluate whether NHF respiratory support is noninferior compared to NIV in respect to treatment failure, defined as need for intubation or change to alternative treatment group, in patients with AECOPD and mild-to-moderate acute or acute-on-chronic hypercapnic respiratory failure.

Methods

We designed a multicentre, prospective, randomised trial on patients with AECOPD, who have pH<7.35 but >7.25 and P_aCO2 >45 mmHg, in whom NIV is indicated as a first-line treatment. According to power analysis, 498 participants will be required for establishing noninferiority of NHF compared to NIV. Patients will be randomly assigned to receive NIV or NHF. Treatment will be adjusted to maintain S_pO2 between 88%–92% for both groups. Arterial blood gases, respiratory variables, comfort, dyspnoea score and any pulmonary or extrapulmonary complications will be assessed at baseline, before treatment initiation, and at 1, 2, 4, 6, 12, 24, 48 h, then once daily from day 3 to patient discharge, intubation or death.

Conclusion

Given the increasing number of studies demonstrating the physiological effects of NHF in COPD patients, we hypothesise that NHF respiratory support will be noninferior to NIV in patients with AECOPD and mild-to-moderate acute or acute on chronic hypercapnic respiratory failure.

Nasal high-flow oxygen could be an effective alternative to NIV respiratory support for patients with mild-to-moderate #AECOPD, especially for those who do not tolerate or have contraindications for NIVhttps://bit.ly/3bgxDYx

Defining a Regulatory Strategy for ATMP/Aerosol Delivery Device Combinations in the Treatment of Respiratory Disease

Advanced Therapeutic Medicinal Products (ATMP) are a heterogenous group of investigational medicinal products at the forefront of innovative therapies with direct applicability in respiratory diseases. ATMPs include, but are not limited to, stem cells, their secretome, or extracellular vesicles, and each have shown some potential when delivered topically within the lung. This review focuses on that subset of ATMPs. One key mode of delivery that has enabling potential in ATMP validation is aerosol-mediated delivery. The selection of the most appropriate aerosol generator technology is influenced by several key factors, including formulation, patient type, patient intervention, and healthcare economics. The aerosol-mediated delivery of ATMPs has shown promise for the treatment of both chronic and acute respiratory disease in pre-clinical and clinical trials; however, in order for these ATMP device combinations to translate from the bench through to commercialization, they must meet the requirements set out by the various global regulatory bodies. In this review, we detail the potential for ATMP utility in the lungs and propose the nebulization of ATMPs as a viable route of administration in certain circumstances. Further, we provide insight to the current regulatory guidance for nascent ATMP device combination product development within the EU and US.

CFD Guided Optimization of Nose-to-Lung Aerosol Delivery in Adults: Effects of Inhalation Waveforms and Synchronized Aerosol Delivery

PURPOSE

The objective of this study was to optimize nose-to-lung aerosol delivery in an adult upper airway model using computational fluid dynamics (CFD) simulations in order to guide subsequent human subject aerosol delivery experiments.

METHODS

A CFD model was developed that included a new high-flow nasal cannula (HFNC) and pharmaceutical aerosol delivery unit, nasal cannula interface, and adult upper airway geometry. Aerosol deposition predictions in the system were validated with existing and new experimental results. The validated CFD model was then used to explore aerosol delivery parameters related to synchronizing aerosol generation with inhalation and inhalation flow rate.

RESULTS

The low volume of the new HFNC unit minimized aerosol transit time (0.2 s) and aerosol bolus spread (0.1 s) enabling effective synchronization of aerosol generation with inhalation. For aerosol delivery correctly synchronized with inhalation, a small particle excipient-enhanced growth delivery strategy reduced nasal cannula and nasal depositional losses each by an order of magnitude and enabled ~80% of the nebulized dose to reach the lungs. Surprisingly, nasal deposition was not sensitive to inhalation flow rate due to use of a nasal cannula interface with co-flow inhaled air and the small initial particle size.

CONCLUSIONS

The combination of correct aerosol synchronization and small particle size enabled high efficiency nose-to-lung aerosol delivery in adults, which was not sensitive to inhalation flow rate.

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.

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.

Nasal High Flow Use in COPD Patients with Hypercapnic Respiratory Failure: Treatment Algorithm & Review of the Literature

Nasal high flow (NHF) therapy has recently gained attention as a new respiratory support system and is increasingly being utilized in every day clinical practice. Recent studies suggest that it may also be effective in patients with hypercapnia and suggest NHF as a possible alternative for patients who cannot tolerate standard noninvasive ventilation. The present review discusses the mechanisms of action that make NHF potentially suitable for chronic obstructive pulmonary disease (COPD) patients and evaluates the current evidence of NHF use for treatment of stable hypercapnic COPD patients as well as acute hypercapnic exacerbation of COPD. An algorithm is also proposed for the clinical application of NHF in patients with acute hypercapnic exacerbation of COPD, based on current literature.

Effect of nebulizer type, delivery interface, and flow rate on aerosol drug delivery to spontaneously breathing pediatric and infant lung models

BACKGROUND

Different types of nebulizers, interfaces, and flow rates are used to deliver aerosolized medications to children. The purpose of this study was to determine the effect of nebulizer type, delivery interface, and flow rate on aerosol drug delivery to spontaneously breathing pediatric and infant lung models.

METHODOLOGY

A teaching mannequin was attached to a sinusoidal pump via a collecting filter at the bronchi to simulate a spontaneously breathing child (Vt: 250 mL, RR: 20 bpm and Ti: 1 second) and infant (Vt = 100 mL, RR = 30 bpm, Ti: 0.7 seconds). Albuterol sulfate was nebulized with jet (Misty Max 10; Cardinal Health) and mesh (Aerogen Solo; Aerogen) nebulizers using a low-flow nasal cannula (LFNC; Hudson), a high-flow nasal cannula (HFNC; Fisher & Paykel), face mask (FM; Hudson), and mouthpiece (MP; Cardinal Health). While all interfaces were used in the pediatric study, only LFNC, HFNC, and FM were tested in the infant study. The mesh nebulizer was tested at 2, 4, and 6 L/min with LFNC, 4 and 6 L/min with HFNC, and 6 L/min with FM and MP. The jet nebulizer was operated at 6 and 8 L/min with FM and 6 L/min with LFNC, HFNC, and MP (n = 5). The drug was eluted from the filter and analyzed by spectrophotometry. Factorial analysis of variance and post hoc comparisons were used for data analysis. P < .05 was considered statistically significant.

RESULTS

Delivery efficiency of mesh nebulizers is two to fourfold more than jet nebulizers used with HFNC, FM, and MP. No statistical difference was found between jet and mesh nebulizers used with LFNC in infants (P = .643) and pediatrics (P = .255). Aerosol delivery with MP was the best compared to other interfaces used in pediatrics (P < .05). As the second-best interface in aerosol drug delivery, the delivery efficiency of FM was greater than HFNC (P = .0001) and LFNC (P = .0001). Increasing flow rate with LFNC and HFNC decreased aerosol delivery with the mesh nebulizer in both infants and pediatrics.

CONCLUSION

The type of nebulizer, delivery interface, and flow rate used in the treatment of children affect aerosol drug delivery.

Management of severe asthma exacerbation: guidelines from the Société Française de Médecine d'Urgence, the Société de Réanimation de Langue Française and the French Group for Pediatric Intensive Care and Emergencies

BACKGROUND

The French Emergency Medicine Society, the French Intensive Care Society and the Pediatric Intensive Care and Emergency Medicine French-Speaking Group edited guidelines on severe asthma exacerbation (SAE) in adult and pediatric patients.

RESULTS

The guidelines were related to 5 areas: diagnosis, pharmacological treatment, oxygen therapy and ventilation, patients triage, specific considerations regarding pregnant women. The literature analysis and formulation of the guidelines were conducted according to the Grade of Recommendation Assessment, Development and Evaluation methodology. An extensive literature research was conducted based on publications indexed in PubMed™ and Cochrane™ databases. Of the 21 formalized guidelines, 4 had a high level of evidence (GRADE 1+/-) and 7 a low level of evidence (GRADE 2+/-). The GRADE method was inapplicable to 10 guidelines, which resulted in expert opinions. A strong agreement was reached for all guidelines.

CONCLUSION

The conjunct work of 36 experts from 3 scientific societies resulted in 21 formalized recommendations to help improving the emergency and intensive care management of adult and pediatric patients with SAE.

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.

Development of a High-Flow Nasal Cannula and Pharmaceutical Aerosol Combination Device

Background: Aerosol drug delivery to the lungs is known to be very inefficient during all forms of noninvasive ventilation, especially when the aerosol is administered simultaneously with high-flow nasal cannula (HFNC) therapy. The objective of this study was to develop a new combination device based on vibrating mesh nebulizers that can provide continuously heated and humidified HFNC therapy as well as on-demand pharmaceutical aerosols with high efficiency. Methods: The combination device implemented separate mesh nebulizers for generating humidity (humidity nebulizer) and delivering the medical aerosol (drug nebulizer). Nebulizers were actuated in an alternating manner with the drug nebulizer delivering the medication during a portion of an adult inhalation cycle. Aerosol entered a small-volume mixing region where it was combined with ventilation gas flow and then entered a heating channel to produce small particles that are desirable for nose-to-lung administration and potentially excipient enhanced growth delivery. Three assessment methods (analytical calculations, computational fluid dynamics [CFD] simulations, and in vitro experiments in three-dimensional [3D] printed devices) were used to improve the mixer-heater design to minimize depositional drug losses, maintain a small device volume, ensure sufficient droplet evaporation, and control the outlet thermodynamic conditions. Results: For an initial configuration (Design 1), good agreement in performance metrics was found using the three assessment methods. Based on insights gained from the CFD simulations of Design 1, two new designs were developed and produced with 3D printing. Experimental analysis indicated that the new designs both achieved <5% depositional loss in the mixer-heater even with cyclic operation and sufficiently dried the aerosol from an initial size of 5.3 μm to an outlet size of ∼1.0 μm. A combination of the applied methods indicated that the desired thermodynamic conditions of HFNC therapy were also met. Conclusions: Multiple methodological approaches were used concurrently to develop a new combination device for administering HFNC therapy and simultaneous on-demand pharmaceutical aerosols to the lungs with high efficiency. The use of a small-volume mixer-heater (<100 mL), synchronization of the drug nebulizer with inhalation, and small outlet particle size should enable high efficiency lung delivery of the aerosol.

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.

Epoprostenol Delivered via High Flow Nasal Cannula for ICU Subjects with Severe Hypoxemia Comorbid with Pulmonary Hypertension or Right Heart Dysfunction

Inhaled epoprostenol (iEPO) has been utilized to improve oxygenation in mechanically ventilated subjects with severe hypoxemia, but the evidence for iEPO via high-flow nasal cannula (HFNC) is rare. Following approval by the institutional review board, this retrospective cohort study evaluated subjects who received iEPO via HFNC for more than 30 min to treat severe hypoxemia comorbid with pulmonary hypertension or right heart dysfunction between July 2015 and April 2018. A total of 11 subjects were enrolled in the study of whom 4 were male (36.4%), age 57.5 ± 22.1 years, and APACHE II score at ICU admission was 18.5 ± 5.7. Ten subjects had more than three chronic heart or lung comorbidities; seven of them used home oxygen. After inhaling epoprostenol, subjects' SpO₂/F_IO₂ ratio improved from 107.5 ± 26.3 to 125.5 ± 31.6 (p = 0.026) within 30-60 min. Five subjects (45.5%) had SpO₂/F_IO₂ improvement >20%, which was considered as a positive response. Heart rate, blood pressure, and respiratory rate were not significantly different. Seven subjects did not require intubation, and seven subjects were discharged home. This retrospective study demonstrated the feasibility of iEPO via HFNC in improving oxygenation. Careful titration of flow while evaluating subjects' response may help identify responders and avoid delaying other interventions. This study supports the need for a larger prospective randomized control trial to further evaluate the efficacy of iEPO via HFNC in improving outcomes.

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.

The Ratio of Nasal Cannula Gas Flow to Patient Inspiratory Flow on Trans-nasal Pulmonary Aerosol Delivery for Adults: An in Vitro Study

Trans-nasal aerosol deposition during distressed breathing is higher than quiet breathing, and decreases as administered gas flow increases. We hypothesize that inhaled dose is related to the ratio of gas flow to patient inspiratory flow (GF:IF). An adult manikin (Laerdal) with a collecting filter placed at trachea was connected to a dual-chamber model lung, which was driven by a ventilator to simulate quiet and distressed breathing with different inspiratory flows. Gas flow was set at 5, 10, 20, 40 and 60 L/min. Albuterol (2.5mg in 1 mL) was nebulized by vibrating mesh nebulizer at the inlet of humidifier at 37 °C for each condition (n = 3). Drug was eluted from the filter and assayed with UV spectrophotometry (276 nm). GF:IF was the primary predictor of inhaled dose (p < 0.001). When the ratio was < 1.0, the inhaled dose was higher than ratio > 1.0 (21.8 ± 3.8% vs. 9.0 ± 3.7%, p < 0.001), and the inhaled dose was similar between quiet and distressed breathing (22.3 ± 5.0% vs. 21.3 ± 2.7%, p = 0.379). During trans-nasal aerosol delivery, GF:IF primarily affected the inhaled dose. Compared to the ratio above 1.0, the ratio below 1.0 produced a higher and more-consistent inhaled dose.

A comparative in vitro study of standard facemask jet nebulization and high-flow nebulization in bronchiolitis

Aim of Study: The use of a nebulizer paired with high-flow nasal cannulas (HFNC) has been proposed for drug delivery in bronchiolitis. Particle size nebulized is a relevant factor determining the efficacy of the nebulization. We replicated in vitro the theoretical parameters most widely used in bronchiolitis and we compared the size of the droplet nebulized with a standard nebulizer and a nebulizer integrated into HFNC. Materials and Methods: We used laser diffraction to analyze the particle size nebulized (volume median diameter Dv50). The standard system was a jet nebulizer connected to a facemask with a flow rate of 8 L/min (JN). Three designs were used as nebulizers integrated into HFNC: a vibrating mesh nebulizer set 1) before (HFNC-BH) and 2) after (HFNC-AH) the humidifier, and 3) a jet nebulizer connected before the nasal cannula (HFNC-BNC). HFNC was used with neonatal (3-8 L/min) and infant cannulas (8-15 L/min). Results: Droplet size was similar among the three drugs studied. A lower particle size was obtained when using the nebulization system integrated into HFNC compared to the standard nebulizer, regardless of the flow rate and the nasal cannula used when the position of the nebulizer was before the nasal cannula (p < 0.05): 6.89 µm (JN), 2.49 µm (HFNC-BNC 3 L/min), 2.59 µm (HFNC-BNC 5 L/min), 2.44 µm (HFNC-BNC 8 L/min), 3.22 µm (HFNC-BNC 10 L/min), 3.23 µm (HFNC-BNC 13 L/min), 3.16 µm (HFNC-BNC 15 L/min). The particle size was lower in HFNC-BF compared to the HFNC-AH using neonatal nasal cannula (3-8 L/min) (p < 0.05). Conclusion: The use of a nebulizer integrated with HFNC has shown promising results in an experimental scenario of bronchiolitis. The particle size achieved with the nebulizer placed before the humidifier is equivalent to the one obtained via conventional nebulization, and it is even smaller when the integrated nebulizer is placed before the nasal cannulas.

Comparison of aerosol delivery across combinations of drug delivery interfaces with and without concurrent high-flow nasal therapy

BACKGROUND

Current clinical practice during high-flow nasal therapy (HFNT) involves utilization of a nasal cannula to provide humidification, with a facemask placed over the cannula to deliver aerosol. Few studies have compared aerosol delivery across various delivery interfaces during HFNT. The objective of this study was to address this gap in the literature and evaluate aerosol delivery using two nebulizer types across different drug delivery interfaces, nasal cannula, facemask, and mouthpiece, during simulated adult HFNT.

METHODS

A facemask or mouthpiece and/or a nasal cannula were positioned on an anatomically correct adult head model. The head model was connected to a breathing simulator via a collection filter. Both healthy breathing pattern and distressed breathing patterns were utilized. Aerosol dose was determined by quantifying the mass of drug captured on a filter positioned distal to the trachea.

RESULTS

During simulated healthy breathing, a significantly greater aerosol dose was observed when the vibrating mesh nebulizer (VMN) was integrated with HFNT alone, supplying aerosol and humidified air simultaneously (2.88 ± 0.15%), as opposed to using with a facemask (0.33 ± 0.07%, 1.62 ± 0.46%, and 1.07 ± 0.25% at 0 L/min (LPM), 2LPM, and 6LPM, respectively) or mouthpiece (0.56 ± 0.13%, 2.16 ± 0.06%, and 1.82 ± 0.41% at 0LPM, 2LPM, and 6LPM). In addition, aerosol delivery was also significantly greater when the VMN was integrated into simulated HFNT (2.88 ± 0.15%), in comparison with using the jet nebulizer (JN) with a facemask (0.82 ± 0.16%) or a mouthpiece (0.86 ± 0.11%). During simulated distressed breathing, a significantly greater aerosol dose was observed when the VMN was integrated with HFNT, supplying aerosol and humidified air simultaneously (6.81 ± 0.45%), compared with using a facemask (0.86 ± 0.04%, 2.96 ± 0.26%, and 4.23 ± 0.93% at 0LPM, 2LPM, and 6LPM) or mouthpiece (0.73 ± 0.37%, 0.97 ± 0.20%, and 3.11 ± 0.53% at 0LPM, 2LPM, and 6LPM, respectively). Aerosol delivery was also greater when the VMN was integrated into HFNT (6.81 ± 0.45%), in comparison with using the JN with a facemask (5.72 ± 0.71%) or a mouthpiece (0.69 ± 0.53%). Furthermore, across all drug delivery interfaces, and in line with previous reports, aerosol delivery was greater during simulated distressed breathing, in comparison with simulated healthy adult breathing.

CONCLUSIONS

This article will be of considerable benefit in enhancing the understanding of aerosol delivery during HFNT, an increasingly adopted therapeutic intervention by healthcare professionals.