Delivery of salbutamol pressurized metered-dose inhaler administered via small-volume spacer devices in intubated, spontaneously breathing rabbits

Development of an ex vivo respiratory pediatric model of bronchopulmonary dysplasia for aerosol deposition studies

Ethical restrictions are limitations of in vivo inhalation studies, on humans and animal models. Thus, in vitro or ex vivo anatomical models offer an interesting alternative if limitations are clearly identified and if extrapolation to human is made with caution. This work aimed to develop an ex vivo infant-like respiratory model of bronchopulmonary dysplasia easy to use, reliable and relevant compared to in vivo infant data. This model is composed of a 3D-printed head connected to a sealed enclosure containing a leporine thorax. Physiological data and pleural-mimicking depressions were measured for chosen respiratory rates. Homogeneity of ventilation was assessed by ^81mkrypton scintigraphies. Regional radioaerosol deposition was quantified with ^99mtechnetium-diethylene triamine pentaacetic acid after jet nebulization. Tidal volumes values are ranged from 33.16 ± 7.37 to 37.44 ± 7.43 mL and compliance values from 1.78 ± 0.65 to 1.85 ± 0.99 mL/cmH₂O. Ventilation scintigraphies showed a homogenous ventilation with asymmetric repartition: 56.94% ± 9.4% in right lung and 42.83% ± 9.36 in left lung. Regional aerosol deposition in lungs exerted 2.60% ± 2.24% of initial load of radioactivity. To conclude the anatomical model satisfactorily mimic a 3-months old BPD-suffering bronchopulmonary dysplasia and can be an interesting tool for aerosol regional deposition studies.

Albuterol delivery via metered dose inhaler in a spontaneously breathing pediatric tracheostomy model

RATIONALE

Little data are available regarding efficiency of drug delivery devices and techniques despite their widespread use in spontaneously breathing tracheostomized patients. We compared patient dose achieved with different devices, inhalation techniques, tracheostomy tube sizes and breathing patterns using a spontaneously breathing tracheostomized pediatric model.

METHODS

A tracheostomy model was connected in series to a breathing simulator with a filter interposed (patient dose). Breathing patterns of a 16-month-old and a 6- and 12-year-old child with tracheostomy with internal diameters (mm) of 3.5, 4.5, and 5.5 were used. Albuterol HFAp MDI was used. Aerotrach Plus, MediBag, Aerochamber MV, Aerochamber Mini, and inline adapter with 6-inch tubing were tested. The latter 3 devices were also tested with assisted technique. Albuterol was analyzed via spectrophotometry.

RESULTS

Aerotrach Plus outperformed almost all devices tested. Aerochamber MV with unassisted technique was the second best and the adapter was the worst. Comparison of efficiency between best and worst performer ranged from 3- to 17.2-fold. The 16-month-old breathing pattern and the 3.5 mm tracheostomy tube had the lowest patient dose. The use of assisted technique decreased patient dose by 18-67% for the 4.5 and 5.5 mm but not for 3.5 mm tracheostomy tubes. A median of 7.4% of the nominal dose was deposited in the tracheostomy tubes.

CONCLUSIONS

Aerotrach Plus and the adapter were the most and least efficient devices respectively. Tracheostomy size and breathing pattern affected drug delivery. The use of assisted technique reduced aerosol delivery.

Aerosol deposition in neonatal ventilation

Lung deposition of inhaled drugs in ventilated neonates has been studied in models of questionable relevance. With conventional nebulizers, pulmonary deposition has been limited to 1% of the total dose. The objective of this study was to assess lung delivery of aerosols in a model of neonatal ventilation using a conventional and novel electronic micropump nebulizer. Aerosol deposition studies with 99mTc diethylenetriamine pentaacetate (99mTc-DTPA) were performed in four macaques (2.6 kg) that were ventilated through a 3.0-mm endotracheal tube (with neonatal settings (peak inspiratory pressure 12-14 mbar, positive end-expiratory pressure 2 mbar, I/E ratio 1/2, respiratory rate 40/min), comparing a jet-nebulizer MistyNeb (3-mL charge, 4.8 microm), an electronic micropump nebulizer operating continuously [Aeroneb Professional Nebulizer (APN-C); 0.5-mL charge, 4.6 microm], and another synchronized with inspiration [Aeroneb Professional Nebulizer Synchronized (APN-S); 0.5-mL charge, 2.8 microm]. The amount of radioactivity deposited into lungs and connections and remaining in the nebulizer was measured by a gamma counter. Despite similar amounts of 99mTc-DTPA in the respiratory circuit with all nebulizers, both APN-S and APN-C delivered more drug to the lungs than MistyNeb (14.0, 12.6, and 0.5% in terms of percentage of nebulizer charge, respectively; p = 0.006). Duration of delivery was shorter with APN-C than with the two other nebulizers (2 versus 6 and 10 min for the APN-S and the MistyNeb, respectively; p < 0.001). Electronic micropump nebulizers are more efficient to administer aerosols in an animal model of ventilated neonates. Availability of Aerogen's electronic micropump nebulizers offers new opportunities to study clinical efficacy and risks of aerosol therapy in ventilated neonates.

Inhalation therapy for infants

Delivering aerosolised drugs to infants poses a number of challenges. It is clear that drug delivery is possible via the inhaled route but to date it has been difficult to demonstrate clearly therapeutic benefit from the use of any conventional therapy in the vast majority of infants. This is probably related to the nature of pulmonary disease in this age group. While most aerosol scientists focus on factors such as aerosol size and airways geometry drug delivery, as in all age groups, is most dependent upon patient behaviour. A small amount of drug reaches the lungs of distressed infants. Consideration of patient device interactions is vital if successful drug delivery is to be achieved and this includes consideration of mask design. Doses reaching the lungs are generally very low when considered in terms of the nominal dose but when considered in terms of dose delivered per kilogram body weight drug delivery to the lungs is generally similar to or greater than in adults. Upper airways deposition is relatively greater than in older subjects, in large part because of nasal breathing, and this will affect the 'therapeutic index' of some drugs.