Surfactant and perfluorocarbon aerosolization by means of inhalation catheters for the treatment of respiratory distress syndrome: an in vitro study

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.

Aerosol drug delivery to spontaneously-breathing preterm neonates: lessons learned

Delivery of medications to preterm neonates receiving non-invasive ventilation (NIV) represents one of the most challenging scenarios for aerosol medicine. This challenge is highlighted by the undersized anatomy and the complex (patho)physiological characteristics of the lungs in such infants. Key physiological restraints include low lung volumes, low compliance, and irregular respiratory rates, which significantly reduce lung deposition. Such factors are inherent to premature birth and thus can be regarded to as the intrinsic factors that affect lung deposition. However, there are a number of extrinsic factors that also impact lung deposition: such factors include the choice of aerosol generator and its configuration within the ventilation circuit, the drug formulation, the aerosol particle size distribution, the choice of NIV type, and the patient interface between the delivery system and the patient. Together, these extrinsic factors provide an opportunity to optimize the lung deposition of therapeutic aerosols and, ultimately, the efficacy of the therapy.In this review, we first provide a comprehensive characterization of both the intrinsic and extrinsic factors affecting lung deposition in premature infants, followed by a revision of the clinical attempts to deliver therapeutic aerosols to premature neonates during NIV, which are almost exclusively related to the non-invasive delivery of surfactant aerosols. In this review, we provide clues to the interpretation of existing experimental and clinical data on neonatal aerosol delivery and we also describe a frame of measurable variables and available tools, including in vitro and in vivo models, that should be considered when developing a drug for inhalation in this important but under-served patient population.

In Vitro Performance of an Investigational Vibrating-Membrane Nebulizer with Surfactant under Simulated, Non-Invasive Neonatal Ventilation Conditions: Influence of Continuous Positive Airway Pressure Interface and Nebulizer Positioning on the Lung Dose

Non-invasive delivery of nebulized surfactant has been a long-pursued goal in neonatology. Our aim was to evaluate the performance of an investigational vibrating-membrane nebulizer in a realistic non-invasive neonatal ventilation circuit with different configurations. Surfactant (aerosols were generated with a nebulizer in a set-up composed of a continuous positive airway pressure (CPAP) generator with a humidifier, a cast of the upper airway of a preterm infant (PrINT), and a breath simulator with a neonatal breathing pattern. The lung dose (LD), defined as the amount of surfactant collected in a filter placed at the distal end of the PrINT cast, was determined after placing the nebulizer at different locations of the circuit and using either infant nasal mask or nasal prongs as CPAP interfaces. The LD after delivering a range of nominal surfactant doses (100–600 mg/kg) was also investigated. Surfactant aerosol particle size distribution was determined by laser diffraction. Irrespective of the CPAP interface used, about 14% of the nominal dose (200 mg/kg) reached the LD filter. However, placing the nebulizer between the Y-piece and the CPAP interface significantly increased the LD compared with placing it 7 cm before the Y-piece, in the inspiratory limb. (14% ± 2.8 vs. 2.3% ± 0.8, nominal dose of 200 mg/kg). The customized eFlow Neos showed a constant aerosol generation rate and a mass median diameter of 2.7 μm after delivering high surfactant doses (600 mg/kg). The customized eFlow Neos nebulizer showed a constant performance even after nebulizing high doses of undiluted surfactant. Placing the nebulizer between the Y-piece and the CPAP interface achieves the highest LD under non-invasive ventilation conditions.

From bench to bedside: in vitro and in vivo evaluation of a neonate-focused nebulized surfactant delivery strategy

Background

Non-invasive delivery of nebulized surfactant has been a neonatology long-pursued goal. Nevertheless, the clinical efficacy of nebulized surfactant remains inconclusive, in part, due to the great technical challenges of depositing nebulized drugs in the lungs of preterm infants. The aim of this study was to investigate the feasibility of delivering nebulized surfactant (poractant alfa) in vitro and in vivo with an adapted, neonate-tailored aerosol delivery strategy.

Methods

Particle size distribution of undiluted poractant alfa aerosols generated by a customized eFlow-Neos nebulizer system was determined by laser diffraction. The theoretical nebulized surfactant lung dose was estimated in vitro in a clinical setting replica including a neonatal continuous positive airway pressure (CPAP) circuit, a cast of the upper airways of a preterm neonate, and a breath simulator programmed with the tidal breathing pattern of an infant with mild respiratory distress syndrome (RDS). A dose-response study with nebulized surfactant covering the 100–600 mg/kg nominal dose-range was conducted in RDS-modelling, lung-lavaged spontaneously-breathing rabbits managed with nasal CPAP. The effects of nebulized poractant alfa on arterial gas exchange and lung mechanics were assessed. Exogenous alveolar disaturated-phosphatidylcholine (DSPC) in the lungs was measured as a proxy of surfactant deposition efficacy.

Results

Laser diffraction studies demonstrated suitable aerosol characteristics for inhalation (mass median diameter, MMD = 3 μm). The mean surfactant lung dose determined in vitro was 13.7% ± 4.0 of the 200 mg/kg nominal dose. Nebulized surfactant delivered to spontaneously-breathing rabbits during nasal CPAP significantly improved arterial oxygenation compared to animals receiving CPAP only. Particularly, the groups of animals treated with 200 mg/kg and 400 mg/kg of nebulized poractant alfa achieved an equivalent pulmonary response in terms of oxygenation and lung mechanics as the group of animals treated with instilled surfactant (200 mg/kg).

Conclusions

The customized eFlow-Neos vibrating-membrane nebulizer system efficiently generated respirable aerosols of undiluted poractant alfa. Nebulized surfactant delivered at doses of 200 mg/kg and 400 mg/kg elicited a pulmonary response equivalent to that observed after treatment with an intratracheal surfactant bolus of 200 mg/kg. This bench-characterized nebulized surfactant delivery strategy is now under evaluation in Phase II clinical trial (EUDRACT No.:2016–004547-36).

Electronic supplementary material

The online version of this article (10.1186/s12931-019-1096-9) contains supplementary material, which is available to authorized users.

Experimental Evaluation of Perfluorocarbon Aerosol Generation with Two Novel Nebulizer Prototypes

The potential of non-invasive ventilation procedures and new minimally invasive techniques has resulted in the research of alternative approaches as the aerosolization for the treatment of respiratory distress syndrome (RDS). The aim of this work was to design two nebulizer prototypes and to evaluate them studying the particle size distribution of the inhaled droplets generated with distilled water and two perfluorocarbons (PFCs). Different experiments were performed with driving pressures of 1–3 bar for each compound. An Aerodynamic Particle Sizer was used to measure the aerodynamic diameter (Da), the mass median aerodynamic diameter (MMAD) and the geometric standard deviation (GSD). The results showed that both prototypes produced heterodisperse aerosols with Da mean values in all cases below 5 µm. The initial experiments with distilled water showed MMAD values lower than 9 µm and up to 15 µm with prototype 1 and prototype 2, respectively. Regarding the PFCs, relatively uniform MMAD values close to 12 µm were achieved. The air delivery with outer lumens of prototype 1 presented more suitable mass distribution for the generation and delivery of a uniform aerosol than the two half-circular ring geometry proposed in the prototype 2.

Experimental and Numerical Modeling of Aerosol Delivery for Preterm Infants

Respiratory distress syndrome (RDS) represents one of the major causes of mortality among preterm infants, and the best approach to treat it is an open research issue. The use of perfluorocarbons (PFC) along with non-invasive respiratory support techniques has proven the usefulness of PFC as a complementary substance to achieve a more homogeneous surfactant distribution. The aim of this work was to study the inhaled particles generated by means of an intracorporeal inhalation catheter, evaluating the size and mass distribution of different PFC aerosols. In this article, we discuss different experiments with the PFC perfluorodecalin (PFD) and FC75 with a driving pressure of 4–5 bar, evaluating properties such as the aerodynamic diameter (D_a), since its value is directly linked to particle deposition in the lung. Furthermore, we develop a numerical model with computational fluid dynamics (CFD) techniques. The computational results showed an accurate prediction of the airflow axial velocity at different downstream positions when compared with the data gathered from the real experiments. The numerical validation of the cumulative mass distribution for PFD particles also confirmed a closer match with the experimental data measured at the optimal distance of 60 mm from the catheter tip. In the case of FC75, the cumulative mass fraction for particles above 10 µm was considerable higher with a driving pressure of 5 bar. These numerical models could be a helpful tool to assist parametric studies of new non-invasive devices for the treatment of RDS in preterm infants.

In Vitro Evaluation of a Device for Intra-Pulmonary Aerosol Generation and Delivery

For infants born with respiratory distress syndrome (RDS), liquid bolus delivery of surfactant administered through an endotracheal tube is common practice. While this method is generally effective, complications such as transient hypoxia, hypercapnia, and altered cerebral blood flow may occur. Aerosolized surfactant therapy has been explored as an alternative. Unfortunately, past efforts have led to disappointing results as aerosols were generated outside the lungs with significant pharyngeal deposition and minimal intrapulmonary instillation. A novel aerosol generator (Microjet™) is evaluated herein for intrapulmonary aerosol generation within an endotracheal tube and tested with Curosurf and Infasurf surfactants. Compared with other aerosol delivery devices, this process utilizes low air flow (range 0.01-0.2 L/min) that is ideal for limiting potential barotrauma to the premature newborn lung. The mass mean diameter (MMD) of the particles for both tested surfactants was less than 4 μm, which is ideal for both uniform and distal lung delivery. As an indicator of phospholipid function, surfactant surface tension was measured before and after aerosol formation; with no significant difference. Moreover, this device has an outside diameter of <1mm, which permits insertion into an endotracheal tube (of even 2.0 mm). In the premature infant where intravenous access is either technically challenging or difficult, aerosol drug delivery may provide an alternative route in patient resuscitation, stabilization and care. Other potential applications of this type of device include the delivery of nutrients, antibiotics, and analgesics via the pulmonary route.

In vitro surfactant and perfluorocarbon aerosol deposition in a neonatal physical model of the upper conducting airways

OBJECTIVE

Aerosol delivery holds potential to release surfactant or perfluorocarbon (PFC) to the lungs of neonates with respiratory distress syndrome with minimal airway manipulation. Nevertheless, lung deposition in neonates tends to be very low due to extremely low lung volumes, narrow airways and high respiratory rates. In the present study, the feasibility of enhancing lung deposition by intracorporeal delivery of aerosols was investigated using a physical model of neonatal conducting airways.

METHODS

The main characteristics of the surfactant and PFC aerosols produced by a nebulization system, including the distal air pressure and air flow rate, liquid flow rate and mass median aerodynamic diameter (MMAD), were measured at different driving pressures (4-7 bar). Then, a three-dimensional model of the upper conducting airways of a neonate was manufactured by rapid prototyping and a deposition study was conducted.

RESULTS

The nebulization system produced relatively large amounts of aerosol ranging between 0.3±0.0 ml/min for surfactant at a driving pressure of 4 bar, and 2.0±0.1 ml/min for distilled water (H2Od) at 6 bar, with MMADs between 2.61±0.1 µm for PFD at 7 bar and 10.18±0.4 µm for FC-75 at 6 bar. The deposition study showed that for surfactant and H2Od aerosols, the highest percentage of the aerosolized mass (∼65%) was collected beyond the third generation of branching in the airway model. The use of this delivery system in combination with continuous positive airway pressure set at 5 cmH2O only increased total airway pressure by 1.59 cmH2O at the highest driving pressure (7 bar).

CONCLUSION

This aerosol generating system has the potential to deliver relatively large amounts of surfactant and PFC beyond the third generation of branching in a neonatal airway model with minimal alteration of pre-set respiratory support.

Acute and sustained effects of aerosolized vs. bolus surfactant therapy in premature lambs with respiratory distress syndrome

BACKGROUND

Surfactant (SF) instillation may produce acute deleterious effects on gas exchange and both systemic and cerebral hemodynamics. Our aim was to compare the effects of aerosolized SF (SF-aero) with those of bolus SF (SF-bolus) administration on gas exchange, lung mechanics, and cardiovascular function in premature lambs with respiratory distress syndrome (RDS).

METHODS

Fourteen preterm lambs (85% gestation) were randomly assigned to receive SF-aero or SF-bolus. Oxygenation index (OI), PaCO2, cardiovascular parameters, carotid blood flow (CBF), lung compliance (mean dynamic compliance), and tidal volume (VT) were measured every 30 min for 6 h. Biochemical and histological analyses were performed.

RESULTS

After delivery, lambs developed severe RDS (inspiratory fraction of oxygen: 1; pH < 7.15; PaCO2 > 80 mm Hg; PaO2 < 30 mm Hg, mean dynamic compliance < 0.08 ml/cm H2O/kg). By 60 min after treatment, both groups showed an improvement in OI, PaCO2, mean dynamic compliance, and VT that was maintained until the end of the experiment. PaCO2 and CBF increased significantly in the SF-bolus group during the first 15-30 min, without concomitant changes in cardiovascular parameters, whereas in the SF-aero group, PaCO2 and CBF decreased gradually. SF-aero induced less alveolar hemorrhage and inflammation.

CONCLUSION

SF-aero produced improvements in gas exchange and lung mechanics similar to those produced by bolus administration but with less lung injury and fewer cerebral hemodynamic changes.

Aerosolized perfluorocarbon improves gas exchange and pulmonary mechanics in preterm lambs with severe respiratory distress syndrome

BACKGROUND

Aerosolized perfluorocarbon (PFC) has been proposed as an alternative method of PFC administration; however, the efficacy of aerosolized PFC in a preterm animal model has not yet been demonstrated.

METHODS

Twelve preterm lambs were randomized to two groups: a perfluorodecalin (PFD) aerosol group (n = 6) receiving 10 ml/kg/h of PFD delivered by an intratracheal inhalation catheter followed by 4 h of mechanical ventilation (MV) or the control group, in which animals (n = 6) were managed for 6 h with MV. Gas exchange, pulmonary mechanics, cardiovascular parameters, and cerebral blood flow (CBF) were measured.

RESULTS

Both groups developed hypoxia, hypercarbia, and acidosis at baseline. Aerosolized PFD improved oxygenation (P < 0.0001) and pulmonary mechanics (P < 0.0001) and changed carbon dioxide values to normal physiological levels, unlike the treatment given to the controls (P < 0.0003). The time course of mean arterial blood pressure and CBF were significantly affected by PFD aerosolization, especially during the first hour of life. CBF gradually decreased during the first hour in the PFD aerosol group and remained stable until the end of the follow-up, whereas CBF remained higher in the control group (P < 0.0028).

CONCLUSION

Aerosolized PFD improves pulmonary function in preterm lambs and should be further investigated as an alternative mode of PFC administration.

Aerosolized semifluorinated alkanes as excipients are suitable for inhalative drug delivery--a pilot study

Semifluorinated alkanes (SFAs) have been described as potential excipients for pulmonary drug delivery, but proof of their efficacy is still lacking. We tested whether SFA formulations with the test drug ibuprofen can be nebulised and evaluated their pharmacokinetics. Physico-chemical properties of five different ibuprofen formulations were evaluated: an aqueous solution (H2O), two different SFAs (perfluorohexyloctane (F6H8), perfluorobutylpentane (F4H5)) with and without ethanol (SFA/EtOH). Nebulisation was performed with a jet catheter system. Inhalative characteristics were evaluated by laser diffraction. A confirmative animal study with an inhalative single-dose (6 mg/kg) of ibuprofen with each formulation was performed in anaesthetised healthy rabbits. Plasma samples at defined time points and lung tissue harvested after the 6-h study period were analyzed by HPLC-MS/MS. Pharmacokinetics were calculated using a non-compartment model. All formulations were nebulisable. No differences in aerodynamic diameters (MMAD) were detected between SFA and SFA/EtOH. The ibuprofen plasma concentration-time curve (AUC) was highest with F4H5/EtOH. In contrast, F6H8/EtOH had the highest deposition of ibuprofen into lung tissue but the lowest AUC. All tested SFA and SFA/EtOH formulations are suitable for inhalation. F4H5/EtOH formulations might be used for rapid systemic availability of drugs. F6H8/EtOH showed intrapulmonary deposition of the test drug.