In vitro assessment of drug delivery through an endotracheal tube using a dry powder inhaler delivery system

Administration of dry powders during respiratory supports

Inhaled drugs are routinely used for the treatment of respiratory-supported patients. To date, pressurized metered dose inhalers and nebulizers are the two platforms routinely employed in the clinical setting. The scarce utilization of the dry powder inhaler (DPI) platform is partly due to the lack of in vivo data that proves optimal delivery and drug efficacy are achievable. Additionally, fitting a DPI in-line to the respiratory circuit is not as straightforward as with the other aerosol delivery platforms. Importantly, there is a common misconception that the warm and humidified inspiratory air in respiratory supports, even for a short exposure, will deteriorate powder formulation compromising its delivery and efficacy. However, some recent studies have dispelled this myth, showing successful delivery of dry powders through the humidified circuit of respiratory supports. Compared with other aerosol delivery devices, the use of DPIs during respiratory supports possesses unique advantages such as rapid delivery and high dose. In this review, we presented in vitro studies showing various setups employing commercial DPIs and effects of ventilator parameters on the aerosol delivery. Inclusion of novel DPIs was also made to illustrate characteristics of an ideal inhaler that would give high lung dose with low powder deposition loss in tracheal tubes and respiratory circuits. Clinical trials are urgently needed to confirm the benefits of administration of dry powders in ventilated patients, thus enabling translation of powder delivery into practice.

Development of an Inline Dry Powder Inhaler for Oral or Trans-Nasal Aerosol Administration to Children

Background: Dry powder inhalers (DPIs) offer a number of advantages, such as rapid delivery of high-dose inhaled medications; however, DPI use in children is often avoided due to low lung delivery efficiency and difficulty in operating the device. The objective of this study was to develop a high-efficiency inline DPI for administering aerosol therapy to children with the option of using either an oral or trans-nasal approach. Methods: An inline DPI was developed that consisted of hollow inlet and outlet capillaries, a powder chamber, and a nasal or oral interface. A ventilation bag or compressed air was used to actuate the device and simultaneously provide a full deep inspiration consistent with a 5-year-old child. The powder chamber was partially filled with a model spray-dried excipient enhanced growth powder formulation with a mass of 10 mg. Device aerosolization was characterized with cascade impaction, and aerosol transmissions through oral and nasal in vitro models were assessed. Results: Best device performance was achieved when all actuation air passed through the powder chamber (no bypass flow) resulting in an aerosol mean mass median aerodynamic diameter (MMAD) <1.75 μm and a fine particle fraction (<5 μm) ≥90% based on emitted dose. Actuation with the ventilation bag enabled lung delivery efficiency through the nasal and oral interfaces to a tracheal filter of 60% or greater, based on loaded dose. In both oral and nose-to-lung (N2L) administrations, extrathoracic depositional losses were <10%. Conclusion: In conclusion, this study has proposed and initially developed an efficient inline DPI for delivering spray-dried formulations to children using positive pressure operation. Actuation of the device with positive pressure enabled effective N2L aerosol administration with a DPI, which may be beneficial for subjects who are too young to use a mouthpiece or to simultaneously treat the nasal and lung airways of older children.

Efficient Nose-to-Lung Aerosol Delivery with an Inline DPI Requiring Low Actuation Air Volume

PURPOSE

To demonstrate efficient aerosol delivery through an in vitro nasal model using a dry powder inhaler (DPI) requiring low actuation air volumes (LV) applied during low-flow nasal cannula (LFNC) therapy.

METHODS

A previously developed LV-DPI was connected to a LFNC system with 4 mm diameter tubing. System connections and the nasal cannula interface were replaced with streamlined components. To simulate nasal respiration, an in vitro nasal model was connected to a downstream lung simulator that produced either passive or deep nasal respiration. Performance of a commercial mesh nebulizer system was also considered.

RESULTS

For the optimized system, steady state cannula emitted dose was 75% of the capsule loaded dose. With cyclic nasal breathing, delivery efficiency to the tracheal filter was 53-55% of the loaded dose, which was just under the design target of 60%. Compared with a commercially available mesh nebulizer, the optimal LV-DPI was 40-fold more efficient and 150 times faster in terms of delivering aerosol to the lungs.

CONCLUSIONS

The optimized LV-DPI system is capable of high efficiency lung delivery of powder aerosols through a challenging nasal cannula interface.

Application of an inline dry powder inhaler to deliver high dose pharmaceutical aerosols during low flow nasal cannula therapy

Inline dry powder inhalers (DPIs) offer a potentially effective option to deliver high dose inhaled medications simultaneously with mechanical ventilation. The objective of this study was to develop an inline DPI that is actuated using a low volume of air (LV-DPI) to efficiently deliver pharmaceutical aerosols during low flow nasal cannula (LFNC) therapy. A characteristic feature of the new inline LV-DPIs was the use of hollow capillary tubes that both pierced the capsule and provided a pathway for inlet air and exiting aerosol. Aerosolization characteristics, LFNC depositional losses and emitted dose (ED) were determined using 10 mg powder masses of a small-particle excipient enhanced growth (EEG) formulation. While increasing the number of inlet capillaries from one to three did not improve performance, retracting the inlet and outlet capillaries did improve ED by over 30%. It was theorized that high quality performance requires both high turbulent energy to deaggregate the powder and high wall shear stresses to minimize capsule retention. Best case performance included a device ED of approximately 85% (of loaded dose) and device emitted mass median aerodynamic diameter of 1.77 µm. Maximum ED through the LFNC system and small diameter (4 mm) nasal cannula was approximately 65% of the loaded dose. Potential applications of this device include the delivery of high dose inhaled medications such as surfactants, antibiotics, mucolytics, and anti-inflammatories.

Development of an Inline Dry Powder Inhaler That Requires Low Air Volume

BACKGROUND

Inline dry powder inhalers (DPIs) are actuated by an external air source and have distinct advantages for delivering aerosols to infants and children, and to individuals with compromised lung function or who require ventilator support. However, current inline DPIs either perform poorly, are difficult to operate, and/or require large volumes (∼1 L) of air. The objective of this study was to develop and characterize a new inline DPI for aerosolizing spray-dried formulations with powder masses of 10 mg and higher using a dispersion air volume of 10 mL per actuation that is easy to load (capsule-based) and operate.

METHODS

Primary features of the new low air volume (LV) DPIs are fixed hollow capillaries that both pierce the capsule and provide a continuous flow path for air and aerosol passing through the device. Two different configurations were evaluated, which were a straight-through (ST) device, with the inlet and outlet capillaries on opposite ends of the capsule, and a single-sided (SS) device, with both the inlet and outlet capillaries on the same side of the capsule. The devices were operated with five actuations of a 10 mL air syringe using an albuterol sulfate (AS) excipient-enhanced growth (EEG) formulation. Device emptying and aerosol characteristics were evaluated for multiple device outlet configurations.

RESULTS

Each device had specific advantages. The best case ST device produced the smallest aerosol [mean mass median aerodynamic diameter (MMAD) = 1.57 μm; fine particle fraction <5 μm (FPF_<5μm) = 95.2%)] but the mean emitted dose (ED) was 61.9%. The best case SS device improved ED (84.8%), but produced a larger aerosol (MMAD = 2.13 μm; FPF_<5μm = 89.3%) that was marginally higher than the initial deaggregation target.

CONCLUSIONS

The new LV-DPIs produced an acceptable high-quality aerosol with only 10 mL of dispersion air per actuation and were easy to load and operate. This performance should enable application in high and low flow mechanical ventilation systems and high efficiency lung delivery to both infants and children.

Current options in aerosolised drug therapy for children receiving respiratory support

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

Aerosol Drug Delivery During Noninvasive Positive Pressure Ventilation: Effects of Intersubject Variability and Excipient Enhanced Growth

BACKGROUND

Nebulized aerosol drug delivery during the administration of noninvasive positive pressure ventilation (NPPV) is commonly implemented. While studies have shown improved patient outcomes for this therapeutic approach, aerosol delivery efficiency is reported to be low with high variability in lung-deposited dose. Excipient enhanced growth (EEG) aerosol delivery is a newly proposed technique that may improve drug delivery efficiency and reduce intersubject aerosol delivery variability when coupled with NPPV.

MATERIALS AND METHODS

A combined approach using in vitro experiments and computational fluid dynamics (CFD) was used to characterize aerosol delivery efficiency during NPPV in two new nasal cavity models that include face mask interfaces. Mesh nebulizer and in-line dry powder inhaler (DPI) sources of conventional and EEG aerosols were both considered.

RESULTS

Based on validated steady-state CFD predictions, EEG aerosol delivery improved lung penetration fraction (PF) values by factors ranging from 1.3 to 6.4 compared with conventional-sized aerosols. Furthermore, intersubject variability in lung PF was very high for conventional aerosol sizes (relative differences between subjects in the range of 54.5%-134.3%) and was reduced by an order of magnitude with the EEG approach (relative differences between subjects in the range of 5.5%-17.4%). Realistic in vitro experiments of cyclic NPPV demonstrated similar trends in lung delivery to those observed with the steady-state simulations, but with lower lung delivery efficiencies. Reaching the lung delivery efficiencies reported with the steady-state simulations of 80%-90% will require synchronization of aerosol administration during inspiration and reducing the size of the EEG aerosol delivery unit.

CONCLUSIONS

The EEG approach enabled high-efficiency lung delivery of aerosols administered during NPPV and reduced intersubject aerosol delivery variability by an order of magnitude. Use of an in-line DPI device that connects to the NPPV mask appears to be a convenient method to rapidly administer an EEG aerosol and synchronize the delivery with inspiration.

A Proof-of-Principle Setup for Delivery of Relenza® (Zanamivir) Inhalation Powder to Intubated Patients

BACKGROUND

A fatal incident was reported when a mechanical ventilated patient received nebulization of a reconstituted Relenza^® formulation. We propose a delivery system to introduce Relenza and other inhalation dry powders to intubated patients to avoid accidental fatalities in the future.

METHODS

This is a bench study demonstrating the feasibility of a delivery system to introduce dry powder of Relenza to intubated patients. A dry powder inhaler placed within a delivery chamber was actuated by compressing a ventilation bag to disperse powder into a tracheal tube. The performance of two inhalers, a Diskhaler^® and an Osmohaler^™, were compared. The effects of the length and size of the tracheal tube on the powder output and sizing of emitted powder were investigated using the more efficient Osmohaler^™.

RESULTS

The efficiency of Osmohaler in delivering Relenza to the distal end [delivered dose=30.2±0.2% and fine particle fraction (FPF)=14.5±1.7%] was significantly higher than the Diskhaler (delivered dose=18.1±4.7% and FPF=3.4±2.1%). While no differences in the delivered dose and FPF were observed between the tracheostomy and endotracheal tubes of the same internal diameter, a larger endotracheal tube (9.0 mm internal diameter) gave a 6% higher FPF compared with the smaller counterpart (7.0 mm internal diameter).

CONCLUSION

The dry powder delivery system has been demonstrated to be capable of delivering Relenza formulation to the distal end of tracheal tubes with a reasonable delivered dose and FPF. It would be necessary for further investigation into incorporating the proposed powder delivery system within a mechanical ventilator, as well as animal and clinical studies to prove its applicability to deliver zanamivir dry powder to ventilated influenza patients in the intensive care setting.

Efficient Nose-to-Lung (N2L) Aerosol Delivery with a Dry Powder Inhaler

PURPOSE

Delivering aerosols to the lungs through the nasal route has a number of advantages, but its use has been limited by high depositional loss in the extrathoracic airways. The objective of this study was to evaluate the nose-to-lung (N2L) delivery of excipient enhanced growth (EEG) formulation aerosols generated with a new inline dry powder inhaler (DPI). The device was also adapted to enable aerosol delivery to a patient simultaneously receiving respiratory support from high flow nasal cannula (HFNC) therapy.

METHODS

The inhaler delivered the antibiotic ciprofloxacin, which was formulated as submicrometer combination particles containing a hygroscopic excipient prepared by spray-drying. Nose-to-lung delivery was assessed using in vitro and computational fluid dynamics (CFD) methods in an airway model that continued through the upper tracheobronchial region.

RESULTS

The best performing device contained a 2.3 mm flow control orifice and a 3D rod array with a 3-4-3 rod pattern. Based on in vitro experiments, the emitted dose from the streamlined nasal cannula had a fine particle fraction <5 μm of 95.9% and mass median aerodynamic diameter of 1.4 μm, which was considered ideal for nose-to-lung EEG delivery. With the 2.3-343 device, condensational growth in the airways increased the aerosol size to 2.5-2.7 μm and extrathoracic deposition was <10%. CFD results closely matched the in vitro experiments and predicted that nasal deposition was <2%.

CONCLUSIONS

The developed DPI produced high efficiency aerosolization with significant size increase of the aerosol within the airways that can be used to enable nose-to-lung delivery and aerosol administration during HFNC therapy.

Development of a new technique for the efficient delivery of aerosolized medications to infants on mechanical ventilation

PURPOSE

To evaluate the efficiency of a new technique for delivering aerosols to intubated infants that employs a new Y-connector, access port administration of a dry powder, and excipient enhanced growth (EEG) formulation particles that change size in the airways.

METHODS

A previously developed CFD model combined with algebraic correlations were used to predict delivery system and lung deposition of typical nebulized droplets (MMAD = 4.9 μm) and EEG dry powder aerosols. The delivery system consisted of a Y-connector [commercial (CM); streamlined (SL); or streamlined with access port (SL-port)] attached to a 4-mm diameter endotracheal tube leading to the airways of a 6-month-old infant.

RESULTS

Compared to the CM device and nebulized aerosol, the EEG approach with an initial 0.9 μm aerosol combined with the SL and SL-port geometries reduced device depositional losses by factors of 3-fold and >10-fold, respectively. With EEG powder aerosols, the SL geometry provided the maximum tracheobronchial deposition fraction (55.7%), whereas the SL-port geometry provided the maximum alveolar (67.6%) and total lung (95.7%) deposition fractions, respectively.

CONCLUSIONS

Provided the aerosol can be administered in the first portion of the inspiration cycle, the proposed new method can significantly improve the deposition of pharmaceutical aerosols in the lungs of intubated infants.

Development of high efficiency ventilation bag actuated dry powder inhalers

New active dry powder inhaler systems were developed and tested to efficiently aerosolize a carrier-free formulation. To assess inhaler performance, a challenging case study of aerosol lung delivery during high-flow nasal cannula (HFNC) therapy was selected. The active delivery system consisted of a ventilation bag for actuating the device, the DPI containing a flow control orifice and 3D rod array, and streamlined nasal cannula with separate inlets for the aerosol and HFNC therapy gas. In vitro experiments were conducted to assess deposition in the device, emitted dose (ED) from the nasal cannula, and powder deaggregation. The best performing systems achieved EDs of 70-80% with fine particle fractions <5 μm of 65-85% and mass median aerodynamic diameters of 1.5 μm, which were target conditions for controlled condensational growth aerosol delivery. Decreasing the size of the flow control orifice from 3.6 to 2.3mm reduced the flow rate through the system with manual bag actuations from an average of 35 to 15LPM, while improving ED and aerosolization performance. The new devices can be applied to improve aerosol delivery during mechanical ventilation, nose-to-lung aerosol administration, and to assist patients that cannot reproducibly use passive DPIs.

NanoCluster budesonide formulations enable efficient drug delivery driven by mechanical ventilation

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

Treating systemic diseases via the lung

Inhalation of pharmacologically active substances for medicinal, social, or recreational purposes has been prevalent for centuries but experience of exploiting the lung as a route of delivery for treatment of nonrespiratory diseases is limited. Despite the success of current applications such as anesthetics, the utility of the lung for drug delivery is not well appreciated, despite advantages such as rapid onset of action. Two drawbacks are the relatively poor efficiency of current inhalation devices, especially for large molecules, and the poor patient acceptability of inhalers. Advances now being made in pulmonary delivery technology may provide the impetus needed for the development of new inhaled presentations of drugs such as peptide hormones and other biologically derived molecules. Molecules of various sizes can be delivered in clinically relevant quantities via the lung. In vitro methods show that lipophilic drugs are absorbed through the alveolar membrane more quickly. Early work in animal models has already shown that absorption of analgesic and antiinflammatory drugs that are not well absorbed orally can be improved by delivering them by inhalation. This work may soon give rise to new formulations for therapeutic use.