Aerosol delivery in infants and young children

Near Elimination of In Vitro Predicted Extrathoracic Aerosol Deposition in Children Using a Spray-Dried Antibiotic Formulation and Pediatric Air-Jet DPI

PURPOSE

This study evaluated the in vitro aerosol performance of a dry powder antibiotic product that combined a highly dispersible tobramycin powder with a previously optimized pediatric air-jet dry powder inhaler (DPI) across a subject age range of 2-10 years.

METHODS

An excipient enhanced growth (EEG) formulation of the antibiotic tobramycin (Tobi) was prepared using a small particle spray drying technique that included mannitol as the hygroscopic excipient and trileucine as the dispersion enhancer. The Tobi-EEG formulation was aerosolized using a positive-pressure pediatric air-jet DPI that included a 3D rod array. Realistic in vitro experiments were conducted in representative airway models consistent with children in the age ranges of 2-3, 5-6 and 9-10 years using oral or nose-to-lung administration, non-humidified or humidified airway conditions, and constant or age-specific air volumes.

RESULTS

Across all conditions tested, mouth-throat depositional loss was < 1% and nose-throat depositional loss was < 3% of loaded dose. Lung delivery efficiency was in the range of 77.3-85.1% of loaded dose with minor variations based on subject age (~ 8% absolute difference), oral or nasal administration (< 2%), and delivered air volume (< 2%). Humidified airway conditions had an insignificant impact on extrathoracic depositional loss and significantly increased aerosol size at the exit of a representative lung chamber.

CONCLUSIONS

In conclusion, the inhaled antibiotic product nearly eliminated extrathoracic depositional loss, demonstrated high efficiency nose-to-lung antibiotic aerosol delivery in pediatric airway models for the first time, and provided ~ 80% lung delivery efficiency with little variability across subject age and administered air volume.

High-Efficiency Dry Powder Aerosol Delivery to Children: Review and Application of New Technologies

While dry powder aerosol formulations offer a number of advantages, their use in children is often limited due to poor lung delivery efficiency and difficulties with consistent dry powder inhaler (DPI) usage. Both of these challenges can be attributed to the typical use of adult devices in pediatric subjects and a lack of pediatric-specific DPI development. In contrast, a number of technologies have recently been developed or progressed that can substantially improve the efficiency and reproducibility of DPI use in children including: (i) nose-to-lung administration with small particles, (ii) active positive-pressure devices, (iii) structures to reduce turbulence and jet momentum, and (iv) highly dispersible excipient enhanced growth particle formulations. In this study, these technologies and their recent development are first reviewed in depth. A case study is then considered in which these technologies are simultaneously applied in order to enable the nose-to-lung administration of dry powder aerosol to children with cystic fibrosis (CF). Using a combination of computational fluid dynamics (CFD) analysis and realistic in vitro experiments, device performance, aerosol size increases and lung delivery efficiency are considered for pediatric-CF subjects in the age ranges of 2-3, 5-6 and 9-10 years old. Results indicate that a new 3D rod array structure significantly improves performance of a nasal cannula reducing interface loss by a factor of 1.5-fold and produces a device emitted mass median aerodynamic diameter (MMAD) of 1.67 μm. For all ages considered, approximately 70% of the loaded dose reaches the lower lung beyond the lobar bronchi. Moreover, significant and rapid size increase of the aerosol is observed beyond the larynx and illustrates the potential for targeting lower airway deposition. In conclusion, concurrent CFD and realistic in vitro analysis indicates that a combination of multiple new technologies can be implemented to overcome obstacles that currently limit the use of DPIs in children as young as two years of age.

Knowledge of oxygen administration, aerosol medicine, and chest physiotherapy among pediatric healthcare workers in Italy

BACKGROUND

Oxygen administration, aerosol devices and drugs, or the use of chest physiotherapy are common practices in pediatrics; however, little is known about the knowledge of pediatric healthcare workers concerning the right utilization of these tools. The aim of this study was to fill this gap as a preliminary step in the implementation of appropriate educational programs.

METHODS

This cross-sectional survey of a nationally representative sample of Italian pediatricians and nurses was carried out between September 1 and October 8, 2008. A self-administered, anonymous questionnaire concerning the approach to respiratory disease in infants and children was distributed to all of the participants at the Annual Congress of the Italian Society of Pediatrics, together with a stamped envelope addressed to the trained study researchers.

RESULTS

Of the 900 distributed questionnaires, 76.7% were completed and returned by 606 physicians (199 primary care pediatricians, 245 hospital pediatricians, and 162 pediatric residents) and 84 pediatric nurses. The vast majority of the respondents did not know the percentage of hemoglobin saturation indicating hypoxemia that requires oxygen administration. Most of the nurses admitted to overusing mucolytics and inhalatory corticosteroids, did not know the role of ipratropium bromide, were unable to indicate the first-line drug for respiratory distress, and did not know the correct dose of salbutamol. Only a minority of the respondents were able to specify the indications for chest physiotherapy. The nurses gave the fewest correct answers regardless of their age, gender, work setting, or the frequency with which they cared for children with respiratory distress in a year cared.

CONCLUSIONS

The knowledge of primary care pediatricians, hospital pediatricians, and pediatric nurses in Italy concerning the use of pulse oximetry, aerosol devices and drugs, and chest physiotherapy is far from satisfactory and should be improved. Educational programs are therefore required for both nurses and pediatricians.

Aerosol therapy in infants and toddlers: past, present and future

Infants and toddlers are a unique subpopulation with regard to aerosol therapy. There are various anatomical, physiological and emotional factors peculiar to this age group that present significant difficulties and challenges for aerosol delivery. Most studies on the factors determining lung deposition of therapeutic aerosols are based on data from adults or older children, which cannot simply be extrapolated directly to infants. The present review describes why infants/toddlers are very different with respect to two major issues - namely their anatomy/physiology and their behavior. We suggest possible solutions and future research directions aimed at improving clinical outcomes of aerosol therapy in this age group.

Numerical simulation of air flow and medical-aerosol distribution in an innovative nebulizer hood

The use of a hood to administer therapeutic aerosols to wheezy infants has many advantages and was found as efficient as administration using a mask. The aim of the present study is to investigate numerically the airflow induced drug dispersion inside the hood. Drug droplet dispersion is examined with respect to three breathing phases: inspiration, expiration, and apnea. The governing equations describing the airflow and the trajectories of drug droplets were solved using the FLUENT 6.1 Computational Fluid Dynamics (CFD) software package. The geometry and mesh were generated with the GAMBIT package. The velocity field of the air and the trajectories of drug droplets inside the funnel--the tube that delivers the drug from the nebulizer to the infant's mouth--and close to its exit are robust and do not show any appreciable differences among the three breathing phases studied. However, in other parts of the hood, air velocity, and particle motion largely depend on the infant's breathing and physiological state. The efficiency of drug delivery to the mouth during inspiration is found to be as high as 84%, whereas it is much smaller in the other two (common) breathing phases examined. Our results may be utilized to improve the hood design and to increase its efficacy for administration of aerosolized medications to infants.

Nebuliser hood compared to mask in wheezy infants: aerosol therapy without tears!

BACKGROUND

Small volume nebulisers (SVNs) with masks commonly provide aerosol therapy for infants with lung diseases. However, infants and toddlers are often disturbed by and thus reject masks.

AIMS

To compare the lung deposition efficiency of the "usual" SVN aerosol mask and a prototype hood attached to an SVN. The advantage of the hood is that no mask is needed and medication can readily be administered during sleep.

METHODS

99mTc salbutamol solution was administered at random by SVN plus mask or hood to 14 wheezy infants (mean age 8 (SD 5) months). The dose and distribution of salbutamol were evaluated using gamma scintigraphy. Clinical response, tolerability by the infants, and parent preference were also compared.

RESULTS

Mean total lung deposition was 2.6% with the hood and 2.4% with the mask (p > 0.05). Variability with the mask was greater than with the hood (coefficient of variation (CoV) 54% v 39%). Both treatments provided similar clinical benefit and side effects as reflected in improved oxygen saturation, reduced respiratory frequency, and increased heart rate. Infants accepted the hood better than the mask and there was a positive correlation between poor acceptance and upper airways and stomach deposition for both treatment modalities. Parents preferred the hood treatments.

CONCLUSIONS

Aerosol therapy by hood is as efficient as by mask but provides a better therapeutic index. It is much better tolerated by infants and preferred by parents. Hood nebulisation is a simple and patient friendly mode of aerosol therapy in wheezy infants.

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.

Nebulized antibiotics in cystic fibrosis

Nebulization is a useful administration route in cystic fibrosis (CF) as it delivers antibiotics directly to the endobronchial site of infection and is associated with decreased toxicity because of limited systemic absorption. It is assumed that the concentration of antibiotics in bronchial secretions should be as high as 10 times the minimum inhibiting concentration to allow penetration of antibiotics into biofilms, suppress inhibitory factors and promote bactericidal effectiveness. However, effective aerosol delivery is compromised by nebulizers with limited capacity to produce particles of a size in the respirable range. Three antibiotics are commonly used for inhalation: tobramycin, amikacin and colistin (colomycin). Placebo-controlled studies evaluating antibiotic aerosol maintenance in stable patients chronically infected with Pseudomonas aeruginosa indicate a significant improvement of lung function and a reduction of the number of hospital admissions for an acute exacerbation of CF. TOBI is a recently marketed preservative- and sulfate-free formula of tobramycin, specially designed for diffusion in the bronchioles and optimal tolerance. A wide-scope study involving 520 patients compared TOBI (300 mg twice daily; n = 258) with placebo (n = 262) for three 28-day cycles with each cycle separated by a 28-day period of no treatment. Respiratory function was significantly improved as early as in the second week and remained so for the rest of the trial even during periods without aerosol treatment. There was also a parallel decrease in the relative risk of hospitalization, the number of days of hospitalization and the number of days on intravenous antipyocyanic treatment. Toxicity studies carried out so far have shown no renal or ototoxicity with nebulized tobramycin. Introduction or selection of resistant bacteria is relatively rare but remains a matter of concern. Aerosol maintenance treatment with an appropriate antibiotic in a high enough dosage can be recommended for patients with CF who are chronically infected with P. aeruginosa.

Management of asthma in young children

Asthma and recurrent airway symptoms in a young child can result in significant morbidity and reduced quality of life. There is significant variability in asthma severity. Even for those who will "outgrow" asthma, regular problems can be minimized with appropriate pharmacotherapy, education, and environmental control. Success with primary prevention through environmental control for children at high risk for asthma has been limited. Avoidance of passive tobacco smoke exposure has primary and secondary prevention benefits. An inhaled short-acting bronchodilator should be available for use as needed. Patients with regular symptoms should receive maintenance anti-inflammatory medication. Add-on therapy can be considered for those with inadequate control on inhaled corticosteroid. Physicians should regularly review drug delivery technique and compliance and provide all patients with a written asthma action plan to guide symptom monitoring and medication use. Physicians should also establish a partnership with the child and family, providing self-management training to enhance skills and confidence.

Guidelines for devices and choices

Asthma patients can be treated safely and effectively with the compounds and inhalation devices currently available. However, the choice of devices is so wide that the healthcare professional may be easily confused, and the effectiveness of treatment reduced. Clear guidelines are needed to help resolve this difficulty; however, those currently available do not contain enough useful information on the different delivery systems to assist the selection process. The function of the anti-asthma drug (i.e., preventer or reliever) should determine the choice of device. For inhaled corticosteroids, the device should provide effective and reliable delivery, while simplicity in use will aid good inhalation technique. A device that minimizes systemic absorption of these drugs will improve drug safety. The devices of choice are pressurized metered dose-inhalers (pMDIs) with spacers and some dry powder inhalers (DPIs). The main selection criteria for short-acting beta2-agonists are portability and patient acceptability. DPIs and pMDIs are the most suitable systems for these drugs. Cost is an important consideration for both drug types.

Impact of constant and breath-synchronized nebulization on inhaled mass of nebulized budesonide in infants and children

The aim of the present study was to compare the output of a breath-synchronized jet nebulizer to a conventional constant output nebulizer over a fixed period of time in terms of inhaled mass of budesonide, i.e., the amount of budesonide deposited on a filter interposed between the nebulizer and the face mask. One hundred and sixty-five asthmatic children (103 boys) were enrolled in this open, randomized, crossover trial. Their age ranged from 6 months to 7.9 years, height from 69 to 132 cm, and weight from 8.2 to 31.3 kg. Their duration of asthma ranged from less than 1 to 7 years. Budesonide suspension, 0.5 mg mL-1, 2 mL, was used. With 5 min of constant output nebulization, the mean inhaled mass of budesonide in percent of the nominal dose was 11.4% in the youngest children and 14.9% in the 7-year-old children. Expressed in percent of the total output of budesonide, i.e., the amount that left the nebulizer as an aerosol, the inhaled mass ranged from 34.6-48.6%. Thus, 51.4-65.4% of the total output was deposited on the expiratory filter. With 5 min of breath-synchronized nebulization, the mean inhaled mass ranged from 10.5-14.9% of the nominal dose. For the youngest patients less than 3-4 years of age, it was approximately 80-90% of the total output. For the older patients the inhaled mass was approximately 95% of the total output, i.e., only small amounts of budesonide were deposited on the expiratory filter. For both modes of nebulization the between-subject variation in inhaled mass was large: up to 6-fold in the young children and 3-4-fold in the older ones. The results of the present study showed that the inhaled mass of budesonide was significantly age-dependent with both modes of nebulization, i.e., the inhaled mass was less in younger children. Breath-synchronized nebulization resulted in reduced waste of drug during expiration.

Inhalation therapy in asthma: nebulizer or pressurized metered-dose inhaler with holding chamber? In vivo comparison of lung deposition in children

OBJECTIVE

To compare lung deposition from a nebulizer and a pressurized metered-dose inhaler (pMDI)/holding chamber to determine their efficiency in aerosol delivery to children.

STUDY DESIGN

Children with stable asthma (n = 17) aged 2 to 9 years inhaled in random order radiolabeled salbutamol from a nebulizer and a pMDI through a nonstatic holding chamber. Body and lung deposition of radiolabeled salbutamol was assessed with a gamma camera.

RESULTS

Mean (absolute dose) total lung deposition expressed as a percentage of the nebulized dose was 5.4% (108 microg) in younger children (<4 years) and 11.1% (222 microg) in older children (>4 years). Mean (absolute dose) total lung deposition expressed as a percentage of the metered dose was 5.4% (21.6 microg) in younger and 9.6% (38.4 microg) in older children.

CONCLUSIONS

For the same age groups we have shown equivalent percentages of total lung deposition of radiolabeled salbutamol aerosolized by either a nebulizer or a pMDI/holding chamber. However, the delivery rate per minute and the total dose of salbutamol deposited were significantly higher for the nebulizer.

Early inhaled glucocorticoid therapy to prevent bronchopulmonary dysplasia

BACKGROUND

The safety and efficacy of inhaled glucocorticoid therapy for asthma stimulated its use in infants to prevent bronchopulmonary dysplasia. We tested the hypothesis that early therapy with inhaled glucocorticoids would decrease the frequency of bronchopulmonary dysplasia in premature infants.

METHODS

We conducted a randomized, multicenter trial of inhaled beclomethasone or placebo in 253 infants, 3 to 14 days old, born before 33 weeks of gestation and weighing 1250 g or less at birth, who required ventilation therapy. Beclomethasone was delivered in a decreasing dosage, from 40 to 5 microg per kilogram of body weight per day, for four weeks. The primary outcome measure was bronchopulmonary dysplasia at 28 days of age. Secondary outcomes included bronchopulmonary dysplasia at 36 weeks of postmenstrual age, the need for systemic glucocorticoid therapy, the need for bronchodilator therapy, the duration of respiratory support, and death.

RESULTS

One hundred twenty-three infants received beclomethasone, and 130 received placebo. The frequency of bronchopulmonary dysplasia was similar in the two groups: 43 percent in the beclomethasone group and 45 percent in the placebo group at 28 days of age, and 18 percent in the beclomethasone group and 20 percent in the placebo group at 36 weeks of postmenstrual age. At 28 days of age, fewer infants in the beclomethasone group than in the placebo group were receiving systemic glucocorticoid therapy (relative risk, 0.6; 95 percent confidence interval, 0.4 to 1.0) and mechanical ventilation (relative risk, 0.8; 95 percent confidence interval, 0.6 to 1.0).

CONCLUSIONS

Early beclomethasone therapy did not prevent bronchopulmonary dysplasia but was associated with lower rates of use of systemic glucocorticoid therapy and mechanical ventilation.

Treatment of childhood asthma. Options and rationale for inhaled therapy

Epidemiological studies suggest the prevalence of asthma is increasing, though some remain sceptical as to the magnitude or indeed the presence of an increase. However, despite improved diagnosis and the availability of the potent drugs now available there remains considerable respiratory morbidity associated with asthma. It is clear from a number of studies that failure to deliver drugs to the lungs when using inhaler devices is a factor contributing to this high level of morbidity. Failure of drug delivery may result from the prescribing of inappropriate devices, failure to use devices appropriately or failure to comply with a treatment regimen. For most of the currently available forms of asthma therapy there are significant advantages to be gained from administering them in aerosol form. The benefits to be derived from administering these drugs as an aerosol include a rapid onset of action for drugs such as beta-agonists and a low incidence of systemic effects from drugs such as beta-agonists and corticosteroids. Over the past 25 years our understanding of the nature of asthma has changed. Though this has been reflected in the emphasis on inhaled corticosteroid therapy in recent guidelines, it has not been reflected in the range of inhaler devices available. Manufacturers continue to place drugs such as corticosteroids in the same devices as short acting beta-agonists even though the requirements for these different drug classes are very different. It is likely that this contributes to suboptimal therapeutic responses with inhaled corticosteroids. However, the variability associated with current delivery systems is relatively small compared with the variability introduced by poor compliance. There is no work currently available to indicate how the use of cheap disposable devises which do not incorporate any form of positive feedback influence compliance with inhaled steroids. Optimising aerosolised drug delivery in childhood involves consideration of the class of drugs, the particular drug within a class but more importantly, the age and abilities of the child. Devices must be selected to suit a particular child's needs and abilities. Devices utilising tidal breathing are generally used such as spacing chambers or, less commonly these days, nebulisers. A screaming or struggling child, or failure to use a closely fitting mask, reduces drug delivery to the lungs enormously. Failure to respond to inhaled therapy in early childhood may be attributable to failure of drug delivery. Drug delivery in early childhood using current devices remains more an art than a science.

Aerosol delivery to wheezy infants: a comparison between a nebulizer and two small volume spacers

Inhalation therapy for wheezy infants with either a nebulizer or a pressurized metered-dose inhaler (pMDI) through a spacer is common practice. The aim of our study was to compare aerosol delivery to wheezy infants from a nebulizer and from a pMDI via two small volume spacers. Twenty wheezy infants (aged 4-12 months) were recruited. They inhaled salbutamol from a Pari-Baby nebulizer, from a detergent-coated Babyhaler, and from a Nebuchamber in random order. A filter was placed between the inhalation systems and the patients. The amount of salbutamol deposited on the filter was measured using an ultraviolet spectrophotometer and was expressed as a percentage of the total nebulized or actuated doses. The mean total nebulized dose for the Pari-Baby (1030 micrograms) was higher (P < 0.001) than the mean actuated dose from a pMDI for the Babyhaler (374 micrograms) and for the Nebuchamber (378 micrograms). Mean drug deposition on the filter was 40.2% (150 micrograms) of the total actuated dose for the detergent-coated Babyhaler and 40.7% (154 micrograms) of the total actuated dose for the Nebuchamber. There was no significant difference in drug deposition on the filter between the two spacers. Mean drug deposition on the filter was 25.3% (260 micrograms) of the total nebulized dose for the Pari-Baby nebulizer. There was no weight dependence in drug deposition on the filter for the two spacers, but, drug deposition increased with the subject's weight for the nebulizer. We have shown that aerosol delivery to wheezy infants from a pMDI through small volume spacers is effective and that a higher percentage of the total amount of salbutamol is delivered than from a nebulizer. The weight dependence in drug deposition for the nebulizer can be of clinical relevance.