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.

International consensus on (ICON) pediatric asthma

Asthma is the most common chronic lower respiratory disease in childhood throughout the world. Several guidelines and/or consensus documents are available to support medical decisions on pediatric asthma. Although there is no doubt that the use of common systematic approaches for management can considerably improve outcomes, dissemination and implementation of these are still major challenges. Consequently, the International Collaboration in Asthma, Allergy and Immunology (iCAALL), recently formed by the EAACI, AAAAI, ACAAI, and WAO, has decided to propose an International Consensus on (ICON) Pediatric Asthma. The purpose of this document is to highlight the key messages that are common to many of the existing guidelines, while critically reviewing and commenting on any differences, thus providing a concise reference. The principles of pediatric asthma management are generally accepted. Overall, the treatment goal is disease control. To achieve this, patients and their parents should be educated to optimally manage the disease, in collaboration with healthcare professionals. Identification and avoidance of triggers is also of significant importance. Assessment and monitoring should be performed regularly to re-evaluate and fine-tune treatment. Pharmacotherapy is the cornerstone of treatment. The optimal use of medication can, in most cases, help patients control symptoms and reduce the risk for future morbidity. The management of exacerbations is a major consideration, independent of chronic treatment. There is a trend toward considering phenotype-specific treatment choices; however, this goal has not yet been achieved.

What the pulmonary specialist should know about the new inhalation therapies

A collaboration of multidisciplinary experts on the delivery of pharmaceutical aerosols was facilitated by the European Respiratory Society (ERS) and the International Society for Aerosols in Medicine (ISAM), in order to draw up a consensus statement with clear, up-to-date recommendations that enable the pulmonary physician to choose the type of aerosol delivery device that is most suitable for their patient. The focus of the consensus statement is the patient-use aspect of the aerosol delivery devices that are currently available. The subject was divided into different topics, which were in turn assigned to at least two experts. The authors searched the literature according to their own strategies, with no central literature review being performed. To achieve consensus, draft reports and recommendations were reviewed and voted on by the entire panel. Specific recommendations for use of the devices can be found throughout the statement. Healthcare providers should ensure that their patients can and will use these devices correctly. This requires that the clinician: is aware of the devices that are currently available to deliver the prescribed drugs; knows the various techniques that are appropriate for each device; is able to evaluate the patient's inhalation technique to be sure they are using the devices properly; and ensures that the inhalation method is appropriate for each patient.

Definition, assessment and treatment of wheezing disorders in preschool children: an evidence-based approach

There is poor agreement on definitions of different phenotypes of preschool wheezing disorders. The present Task Force proposes to use the terms episodic (viral) wheeze to describe children who wheeze intermittently and are well between episodes, and multiple-trigger wheeze for children who wheeze both during and outside discrete episodes. Investigations are only needed when in doubt about the diagnosis. Based on the limited evidence available, inhaled short-acting beta(2)-agonists by metered-dose inhaler/spacer combination are recommended for symptomatic relief. Educating parents regarding causative factors and treatment is useful. Exposure to tobacco smoke should be avoided; allergen avoidance may be considered when sensitisation has been established. Maintenance treatment with inhaled corticosteroids is recommended for multiple-trigger wheeze; benefits are often small. Montelukast is recommended for the treatment of episodic (viral) wheeze and can be started when symptoms of a viral cold develop. Given the large overlap in phenotypes, and the fact that patients can move from one phenotype to another, inhaled corticosteroids and montelukast may be considered on a trial basis in almost any preschool child with recurrent wheeze, but should be discontinued if there is no clear clinical benefit. Large well-designed randomised controlled trials with clear descriptions of patients are needed to improve the present recommendations on the treatment of these common syndromes.

Chronic wet cough: Protracted bronchitis, chronic suppurative lung disease and bronchiectasis

The role of persistent and recurrent bacterial infection of the conducting airways (endobronchial infection) in the causation of chronic respiratory symptoms, particularly chronic wet cough, has received very little attention over recent decades other than in the context of cystic fibrosis (CF). This is probably related (at least in part) to the (a) reduction in non-CF bronchiectasis in affluent countries and, (b) intense focus on asthma. In addition failure to characterize endobronchial infections has led to under-recognition and lack of research. The following article describes our current perspective of inter-related endobronchial infections causing chronic wet cough; persistent bacterial bronchitis (PBB), chronic suppurative lung disease (CSLD) and bronchiectasis. In all three conditions, impaired muco-ciliary clearance seems to be the common risk factor that provides organisms the opportunity to colonize the lower airway. Respiratory infections in early childhood would appear to be the most common initiating event but other conditions (e.g., tracheobronchomalacia, neuromuscular disease) increases the risk of bacterial colonization. Clinically these conditions overlap and the eventual diagnosis is evident only with further investigations and long term follow up. However whether these conditions are different conditions or reflect severity as part of a spectrum is yet to be determined. Also misdiagnosis of asthma is common and the diagnostic process is further complicated by the fact that the co-existence of asthma is not uncommon. The principles of managing PBB, CSLD and bronchiectasis are the same. Further work is required to improve recognition, diagnosis and management of these causes of chronic wet cough in children.

Persistent of respiratory syncytial virus in human dendritic cells and influence of nitric oxide

The annual epidemics of respiratory syncytial virus (RSV) infection are probably explained by poor herd immunity and the existence of a dormant reservoir of virus that is activated by an unknown trigger. The virus causes particular problems in infants, the elderly and patients with chronic obstructive airways disease (COPD). During two consecutive winters, human monocyte-derived dendritic cells (DCs) were exposed on a single occasion to one of two forms of RSV labelled with a fluorescent expresser genes (rgRSV or rrRSV) during the epidemic season. The cultures were maintained for many months, with fresh DCs being added at monthly intervals. The cultures were variously exposed to 600 parts per billion (ppb) nitric oxide for 15 min, nitric oxide (NO) donors and NO inhibitors outside the RSV epidemic season. The pattern of productive infection of DCs in vitro appeared to parallel the natural epidemics, in that DCs exhibited evidence of viral replication and productive infection only as manifested by intracellular fluorescence and infection of HeLa cells during the RSV epidemic season. When the long-term cultures were exposed to the above agents outside the RSV epidemic season there was again evidence of vigorous replication and productive infection, as shown by the reappearance of fluorescence and productive infection of HeLa cells. The results indicate that RSV may remain dormant in dendritic cells for prolonged periods and that replication appears to be activated by suppression of endogenous NO production. These observations may be key to our understanding of the mechanisms contributing to the annual epidemics of RSV infection.

Phenotype of acute respiratory syncytial virus induced lower respiratory tract illness in infancy and subsequent morbidity

The objective of this study was to investigate the association hypothesis that outcome following respiratory syncytial virus (RSV) induced bronchiolitis (RSVB) and RSV induced wheeze (RSVW) are different. At 3 years respiratory symptoms were more common in those with RSV infection than the control group but there was no increase in allergic sensitisation (11% vs 10%). Those with RSVW were more likely to have evidence of allergic sensitisation when compared with RSVB subjects (22% vs 7%), and have increased symptoms and increased use of inhaled steroids.

CONCLUSION

The data argue that RSV infection during infancy does not induce allergic asthma and that host factors rather than the virus determine long-term outcomes.

Differentiation and immune function of human dendritic cells following infection by respiratory syncytial virus

RSV causes annual epidemics of bronchiolitis in winter months resulting in the hospitalization of many infants and the elderly. Dendritic cells (DCs) play a pivotal role in coordinating immune responses to infection and some viruses skew, or subvert, the immune functions of DCs. RSV infection of DCs could alter their function and this could explain why protection after natural RSV infection is incomplete and of short duration. In this study, this interaction between DCs and RSV was investigated using a human primary culture model. DCs were generated from purified healthy adult volunteer peripheral blood monocytes. Effects of RSV upon DC phenotype with RSV primed DCs was measured using flow cytometry. Changes to viability and proliferation of cocultured DCs and T-cells were determined using microscopy with fluorescent dyes (Hoechst 33342 and propidium iodide). DC maturation was not prevented by the RSV challenge. RSV infected a fraction of DCs (10-30%) but the virus replicated slowly in these cells with only small reduction to cell viability. DCs challenged with RSV stimulated T-cell proliferation less well than lipopolysaccharide. This is the first study to demonstrate RSV infection of human monocyte derived DCs and suggests that the virus does not significantly interfere with the function of these cells and potentially may promote cellular rather than humoral responses.

Respiratory syncytial virus and neutrophil activation

Respiratory syncytial virus infects almost all children by 2 years of age. Neutrophils are the predominant airway leucocytes in RSV bronchiolitis and they are activated in the presence of infection. However it is not clear whether RSV can directly signal to activate neutrophil cytotoxic function. To investigate this we have used a preparation of RSV washed using a new centrifugal diafiltration method to rapidly remove inflammatory molecules produced by the epithelial cells used to propagate the RSV stock. Human neutrophils were isolated from peripheral blood and activated with either the unwashed crude RSV preparations or the purified intact RSV. Neutrophils were also challenged with purified RSV G-glycoprotein. The effect of challenging human neutrophils with these preparations of intact RSV, or the RSV G-glycoprotein, was assessed by measuring the cell surface expression of CD11b and CD18b, the phagocytic oxidative burst, and intracellular release of calcium pools. Neutrophils challenged with the washed RSV exhibited significantly lower activation of surface marker expression (P < 0.001) and oxidative burst (P < 0.001) than those challenged with unwashed virus or with virus free supernatant. There was no increase in intracellular calcium release on exposure to the washed RSV. Purified G glycoprotein did not stimulate neutrophils, whilst the use of a blocking antibody to the F protein did not prevent unwashed RSV from activating cytotoxic responses. These results suggest that neutrophils have no innate signalling system that recognizes RSV but they are activated at sites of RSV infection as a result of the cytokines and inflammatory molecules released by virally infected cells.

A pilot study of oral L-arginine in cystic fibrosis

Exhaled nitric oxide has previously been found to be low in cystic fibrosis. The aim of this study was to determine whether exhaled nitric oxide levels would increase in response to oral L-arginine supplementation administered daily for 4 weeks. Exhaled and nasal nitric oxide was measured weekly. Plasma L-arginine levels increased in response to supplementation but this was not reflected in an increase in eNO levels.

Budesonide/formoterol in a single inhaler versus inhaled corticosteroids alone in the treatment of asthma

The aim of this study was to evaluate the efficacy (expressed as effect on lung function) and tolerability of Symbicort (budesonide/formoterol in a single inhaler) in children with asthma. This was a double-blind, double-dummy, randomized, parallel-group, multicenter trial. After a 2-4-week run-in period, 286 asthmatic children (177 boys, 109 girls; mean age, 11 years; mean forced expiratory volume in 1 sec (FEV(1)), 75% predicted normal), previously treated with inhaled corticosteroids (average dose 548 microg/day), were randomized to 12 weeks' treatment with either budesonide/formoterol 80/4.5 microg, two inhalations twice daily (n = 148), or an equivalent dose of budesonide 100 microg, two inhalations twice daily (n = 138). Efficacy variables included morning and evening peak expiratory flow (PEF), spirometery, asthma symptoms, and use of rescue medication (beta(2)-agonists). Serial FEV(1) assessments were carried out on a subgroup of children (budesonide/formoterol, n = 41; budesonide, n = 40) at randomization and at week 12. Relative to baseline, morning PEF (primary variable) increased to a significantly greater extent with budesonide/formoterol than with budesonide alone (7.22% predicted normal vs 3.45% predicted normal; P < 0.001). Evening PEF also increased significantly with budesonide/formoterol (6.13% predicted normal vs. 2.73% predicted normal; P < 0.001), as did mean FEV(1) and serial FEV(1) measured over 12 hr (both P < 0.05). Similar improvements in asthma symptoms and rescue medication use were observed in both groups. The two treatment groups were similar in terms of their adverse-event profile and rates of discontinuation. Budesonide/formoterol in a single inhaler provided rapid improvements in PEF and FEV(1) compared to inhaled budesonide alone. These improvements were sustained throughout the study period. Budesonide/formoterol was well-tolerated in children with moderate persistent asthma.

Neutrophil survival is prolonged in the airways of healthy infants and infants with RSV bronchiolitis

Large numbers of neutrophils in the airway of infants infected by respiratory syncytial virus (RSV) are recruited by chemokines, such as interleukin-8, and specific inflammatory molecules can delay apoptosis increasing their longevity. The aim of this study was to investigate whether airway secretions in RSV bronchiolitis contain factors that influence neutrophil apoptosis. Nasal lavage fluid (NLF) was obtained from 24 infants with RSV bronchiolitis (31 infant controls and 12 adults). Neutrophils isolated from healthy adult volunteers were incubated with the NLF in Dulbecco modified Eagle medium (DMEM) for 24 h, and apoptosis and necrosis were quantified using Hoechst 33342 and propidium iodide viability dyes. The presence of putative factors that delay neutrophil apoptosis was investigated using inhibitors to leukotriene-B4, lipopolysaccharide and the IL-8 receptor CXCR2, and blocking antibodies to granulocyte-monocyte colony-stimulating factor. Characterisation of NLF involved tests of thermal instability, proteolysis, deoxyribonuclease digestion and molecular filtration. NLF from infants with RSV bronchiolitis and controls significantly delayed neutrophil apoptosis, whereas NLF from healthy adults did not. None of these inhibitor molecules blocked this delay in apoptosis but activity was heat liable and >3 kDa. The study showed that nasal lavage fluid from infants significantly delays neutrophil apoptosis. The speculation is that the prolonged survival of neutrophils in the infant airway contributes to the characteristic accumulation of neutrophils in the airways of infants with respiratory infections.

Colistin stimulates the activity of neutrophil elastase and Pseudomonas aeruginosa elastase

Nonantimicrobial effects of antibiotics may contribute to their activity in the treatment of infective airway disease. The aim of this study was to identify antibiotics used for the treatment of infection in cystic fibrosis that may alter the activity of human neutrophil elastase (HNE) and Pseudomonas aeruginosa elastase (PE). The effect of antibiotics on the activity of purified HNE and PE, and HNE in sputum was assessed using colourimetric and fluorescent substrate assays by kinetic measurements, and by examining the interaction of HNE with inhibitors. Ceftazidime, tobramycin, and gentamycin slightly inhibited purified HNE activity whereas erythromycin and colistin significantly stimulated purified HNE and PE (395 and 557%, respectively). However, only colistin increased HNE activity in sputum (+102%) and was therefore studied in more detail. This increase in activity was not due an interference with the specific inhibition of HNE by alpha1-antitrypsin but colistin was found to reverse the inhibitory effects of small molecular weight molecules like heparin. Colistin increases the activity of human neutrophil elastase and Pseudomonas aeruginosa elastase, two proteases that contribute to the pathogenesis of cystic fibrosis airway disease.

Differential response of wheezes and ruttles to anticholinergics

Computerised breath sounds analysis was used to assess the response of infants with wheeze and ruttles to the drug ipratropium bromide. A mean decrease in breath sounds intensity occurred in infants with ruttles after five minutes (20.5 dB), but not until 20 minutes in those with wheeze (8.1 dB). This differential response may be related to different underlying pathophysiology.

Anticholinergic drugs for wheeze in children under the age of two years

BACKGROUND

Wheeze in infancy and early childhood is common and appears to be increasing though the magnitude of any increase is unclear. Most wheezing episodes in infancy are precipitated by respiratory viral infections. Treatment of very young children with wheeze remains controversial. Anti-cholinergics are often prescribed but practice varies widely and the efficacy of this form of therapy remains the subject for debate.

OBJECTIVES

Wheeze in infancy and early childhood is common and appears to be increasing. Most wheezing episodes in infancy are a result of viral infection. Bronchodilator medications such as beta2-agonists and anti-cholinergic agents are often used to relieve symptoms, but patterns of use vary. The objective of this review was to assess the effects of anti-cholinergic therapy in the treatment of wheezing infants.

SEARCH STRATEGY

We searched the Cochrane Airways Group trials register and the reference lists of articles. We contacted researchers in the field and industry sources.

SELECTION CRITERIA

Randomised trials that compared anti-cholinergic therapy with placebo or beta2-agonists in wheezing children under two years of age. Children with acute bronchiolitis and chronic lung disease were excluded.

DATA COLLECTION AND ANALYSIS

Eligibility for inclusion and quality of trials were assessed independently by two reviewers.

MAIN RESULTS

Six trials involving 321 infants in three different settings were included. Compared with beta2-agonist alone, the combination of ipratropium bromide and beta2-agonist was associated with a reduced need for additional treatment, but no difference was seen in treatment response, respiratory rate or oxygen saturation improvement in the emergency department. There was no significant difference in length of hospital stay between ipratropium bromide and placebo; or between ipratropium bromide and beta2-agonist combined compared with beta2-agonist alone. However, combined ipratropium bromide and beta2-agonist compared to placebo showed significantly improved clinical scores at 24 hours. Parents preferred ipratropium bromide over nebulised water or placebo for relief of their children's symptoms at home.

REVIEWER'S CONCLUSIONS

There is not enough evidence to support the uncritical use of anti-cholinergic therapy for wheezing infants, although parents using it at home were able to identify benefits.

Omega-3 fatty acids (from fish oils) for cystic fibrosis

BACKGROUND

Epidemiological (population studies) and other studies suggest that a diet rich in omega-3 essential fatty acids (derived from fish oil) may have beneficial anti-inflammatory effects for chronic conditions such as cystic fibrosis.

OBJECTIVES

To determine whether there is evidence that omega-3 polyunsaturated fatty acid supplementation reduces morbidity and mortality. To identify any adverse events associated with omega-3 polyunsaturated fatty acid supplementation.

SEARCH STRATEGY

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group specialised trials register, which comprises references identified from comprehensive electronic database searches, handsearching relevant journals and handsearching abstract books of conference proceedings. Authors and persons interested in the question were contacted. Date of the most recent search of the Group's specialised register: May 2002.

SELECTION CRITERIA

Randomised controlled trials in patients with cystic fibrosis in which omega-3 fatty acid supplements were compared with a placebo oil.

DATA COLLECTION AND ANALYSIS

Two reviewers independently selected the trials to be included in the review and assessed the methodological quality of the trials using two approaches: Cochrane assessment of allocation concealment and Jadad quality assessment score. Using data acquisition forms, two reviewers independently extracted data. Missing data has been requested.

MAIN RESULTS

The initial literature search identified six trials. Two trials, involving 31 participants satisfied our inclusion criteria and were included in the review. Both compared omega-3 fatty acids to olive oil controls for a six week treatment period. One study (19 participants) showed an improvement in FEV1, FVC, Shwachman score and reduction in sputum volume in the fish oil group at the end of this short treatment period.

REVIEWER'S CONCLUSIONS

The review of trials found that regular omega-3 supplements may provide some benefits for people with cystic fibrosis with relatively few adverse effects, although the evidence is insufficient to draw firm conclusions. There is insufficient evidence to recommend routine use of supplements of omega-3 fatty acids in people with cystic fibrosis. The most notable feature highlighted by this review was the lack of data for many of the outcomes likely to be meaningful to people with or making treatment decisions about CF. A large, long-term, multi-centre, randomised controlled study is needed in order to determine if there is a significant therapeutic effect and to assess the influence of disease severity, dosage and duration of treatment. Future researchers should note the need for additional pancreatic enzymes.

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.

The effect of ribavirin to treat previously healthy infants admitted with acute bronchiolitis on acute and chronic respiratory morbidity

The role of ribavirin in the treatment of acute bronchiolitis is controversial. It has been suggested that the use of ribavirin may be of benefit during the acute illness and may reduce subsequent recurrent respiratory morbidity. This randomized, double-blind, placebo-controlled study was designed to determine whether ribavirin administered during the acute illness would have an influence on respiratory morbidity during both the acute illness and during the following year. Bronchial reactivity 6 months after the acute illness was also assessed. Forty previously well infants with moderately severe acute bronchiolitis were recruited during three winter epidemics. Subjects received study medication for 18 h a day. Management was otherwise unaltered. Subjects were evaluated daily by the investigator and subsequently assessed at 6 weeks, 6 months and 1 year following the acute illness. Assessment of bronchial hyper-responsiveness was assessed at 6 months of age using total body plethysmography and an established ultra-sonically nebulized distilled water challenge. A total of 40 patients (21 ribavirin, 19 placebo) were entered into the study. The two groups did not differ with respect to age, gender or clinical severity on entry to the trial. No significant differences were identified in the rate of clinical improvement over the first 24 h, the time to discharge, bronchial responsiveness at 6 months of age, frequency of significant respiratory symptoms over the first year of life and the frequency of prescribed bronchodilators and inhaled steroids during the year of follow-up. This study was unable to demonstrate any clinical benefit from the use of ribavirin in the acute illness or during subsequent follow-up for 1 year.

Exhaled nitric oxide is reduced in infants with cystic fibrosis

BACKGROUND

Exhaled nitric oxide levels are low in patients with cystic fibrosis (CF), despite the chronic inflammation present in the airways. This study aimed to determine whether levels of exhaled nitric oxide were reduced prior to the onset of respiratory symptoms in infants with CF.

METHODS

The levels of exhaled nitric oxide were measured using a chemiluminescence analyser in five infants with CF and 11 healthy control subjects, both groups having a mean age of 48.6 days.

RESULTS

Mean levels of exhaled nitric oxide were significantly lower in infants with CF than in the control group (4.9 ppb v 12.1 ppb; p=0.01).

CONCLUSIONS

This finding may be the key to understanding the inflammatory processes in early cystic fibrosis and may lead to novel treatment approaches.

Survey of respiratory sounds in infants

BACKGROUND

Over the last decade there has been an apparent increase in childhood wheeze. We speculated that much of the reported increase may be attributed to the term wheeze being adopted by parents to describe a variety of other forms of noisy breathing.

AIMS

To investigate terminology used by parents to describe their children's breath sounds.

METHODS

An interview was carried out with the parents of 92 infants with noisy breathing, beginning with an open question and then directed towards a more detailed description. Finally, the parents were asked to choose from a wheeze, ruttle, and stridor on imitation by the investigator and video clips of children.

RESULTS

Wheeze was the most commonly chosen word on initial questioning (59%). Only 36% were still using this term at the end of the interview, representing a decrease of one third, whereas the use of the word ruttles doubled.

CONCLUSIONS

Our results reflect the degree of inaccuracy involved in the use of the term wheeze in clinical practice, which may be leading to over diagnosis. Imprecise use of this term has potentially important implications for therapy and clinical trials.

When a "wheeze" is not a wheeze: acoustic analysis of breath sounds in infants

Epidemiological studies indicate that the prevalence of "wheeze" is very high in early childhood. However, it is clear that parents and clinicians frequently use the term "wheeze" for a range of audible respiratory noises. The commonest audible sounds originating from the lower airways in infancy are ruttles, which differ from classical wheeze in that the sound is much lower in pitch, with a continuous rattling quality and lacking any musical features. The aim of this study was to clearly differentiate wheeze and ruttles objectively using acoustic analysis. Lung sounds were recorded in 15 infants, seven with wheeze and eight with ruttles, using a small sensitive piezoelectric accelerometer, and information relating to the respiratory cycle was obtained using inductive plethysmography. The acoustic signals were analysed using a fast fourier transformation technique (Respiratory Acoustics Laboratory Environment programme). The acoustic properties of the two noises were shown to be quite distinct, the classical wheeze being characterized by a sinusoidal waveform with one or more distinct peaks in the power spectrum display; the ruttle is represented by an irregular nonsinusoidal waveform with diffuse peaks in the power spectrum and with increased sound intensity at a frequency of <600 Hz. It is important for clinicians and epidemiologists to recognize that there are distinct types of audible respiratory noise in early life with characteristic acoustic properties.

IL-8 and neutrophil elastase levels in the respiratory tract of infants with RSV bronchiolitis

The aim of this study was to determine whether interleukin (IL)-8 is released within the upper respiratory tract of infants during respiratory syncytial virus (RSV) bronchiolitis and whether the large number of polymorphonuclear neutrophils (PMNs) present in the respiratory tract of these infants are contributing to the inflammation through release of inflammatory mediators. Twenty-seven infants with acute bronchiolitis were recruited during one winter epidemic and 20 infant control subjects were recruited from a cohort participating in a community-based vaccine study. Samples of airways fluid were obtained using nasal lavage. The lavage fluid was spun to remove the cells, and the supernatant was stored at -70 degrees C. The supernatants were subsequently assayed for the presence of IL-8, total human neutrophil elastase (HNE) and neutrophil elastase activity. In the children with bronchiolitis compared with control infants, elevated levels of IL-8 (median (range) 1.53 (0-153) versus 0 (0-5.6) ng x mL(-1)) HNE (136 (32-694) versus 14 (0-516) ng x mL(-1)) and elastase activity (4 (1-220) versus 1 (0-339) mU x mL(-1)) were found. These results indicate that interleukin-8 is released in the upper respiratory tract in response to respiratory syncytial virus infection and suggest that polymorphonuclear neutrophil products are playing an important role in the inflammatory response to respiratory syncytial virus infection in infants with acute bronchiolitis. This contrasts with the predominantly eosinophilic response evident in atopic upper and lower respiratory tract disease.

Randomised controlled trial of budesonide for the prevention of post-bronchiolitis wheezing

BACKGROUND

Previous studies suggest that recurrent episodes of coughing and wheezing occur in up to 75% of infants after acute viral bronchiolitis.

AIM

To assess the efficacy of budesonide given by means of a metered dose inhaler, spacer, and face mask in reducing the incidence of coughing and wheezing episodes up to 12 months after acute viral bronchiolitis.

METHODS

Children under the age of 12 months admitted to hospital with acute viral bronchiolitis were randomised to receive either budesonide or placebo (200 microg or one puff twice daily) for the next eight weeks. Parents kept a diary card record of all episodes of coughing and wheezing over the next 12 months.

RESULTS

Full follow up data were collected for 49 infants. There were no significant differences between the two study groups for the number of infants with symptom episodes up to six months after hospital discharge. At 12 months, 21 infants in the budesonide group had symptom episodes compared with 12 of 24 in the placebo group. The median number of symptom episodes was 2 (range, 0-13) in those who received budesonide and 1 (range, 0-11) in those who received placebo. Because there is no pharmacological explanation for these results, they are likely to be caused by a type 1 error, possibly exacerbated by there being more boys in the treatment group.

CONCLUSION

Routine administration of budesonide by means of a metered dose inhaler, spacer, and face mask system immediately after acute viral bronchiolitis cannot be recommended.

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.

Flow early in the inspiratory manoeuvre affects the aerosol particle size distribution from a Turbuhaler

Several in vitro and in vivo studies have emphasized the importance of generating a high inspiratory flow when using a dry powder inhaler. Little attention has been paid to the influence of the inspiratory flow profile on the particle size distribution contained in aerosols generated by these devices. The internal volume of a device such as the Turbuhaler is small compared with a vital capacity breath and it is possible that all the powder has been drawn from the device before peak inspiratory flow has been achieved, particularly if the time to peak inspiratory flow is prolonged. A series of experiments were performed to assess the effect of different flow profiles through the Turbuhaler, each with a peak flow of 60 1 min-1. A 400 microgram budesonide Turbuhaler was enclosed in a chamber allowing air to pass unimpeded through the dosing channels and entrainment ports. A large three-way tap was used to blow powder from the device across a Malvern Mastersizer laser particle sizer which produced a profile of the particle size distribution within the aerosol. The rate of increase in flow through the Turbuhaler was determined by the rate at which the three-way tap was turned, and recorded by means of a pneumotachograph. The rate of increase in flow was found to significantly affect the particle size-distribution within the aerosol. Failure to attain a flow of 30 1 min-1 before 150 ml of air had passed through the device resulted in the aerosol volume median diameter increasing from less than 6.6 microns to greater than 45.3 microns. These results indicate that flow during the initial part of the inspiratory effort may be important in determining the characteristics of the aerosol generated by a dry powder inhaler. With more sophisticated equipment, it might be possible to explore the relationship between flow profile and particle size distribution generated by dry powder devices in more detail.

Comparison of drug delivery from conventional versus "Venturi" nebulizers

Attempts to improve drug delivery from conventional jet nebulizers have included the use of storage systems to reduce drug wastage during exhalation. Venturi nebulizers enhance drug delivery during inhalation, reducing treatment times and drug wastage. This study investigated the effect of age on inhaled dose from a conventional jet nebulizer (Acorn) used both with and without a storage chamber (Mizer), compared to two Venturi nebulizers (Ventstream and Pari LC). Filters were attached to the four nebulizer systems, containing salbutamol, and 18 children with cystic fibrosis (3-16 yrs) inhaled through these devices. The quantity of drug collected on the filter was assessed using ultraviolet spectrophotometry. The particle size distribution of the aerosol from each nebulizer system was measured using laser diffraction. Inspiratory filter deposition using the Acorn was lower than the Acorn with Mizer, and both Venturi nebulizers. Filter deposition using the Acorn with Mizer was lower than the Pari LC. No trend with age, height or weight was noted using any nebulizer. Aerosol particle size using the Ventstream was lower than the other nebulizer systems. Drug output from both Venturi nebulizers was more efficient than from the jet nebulizer, used with and without the storage chamber, during inhalation by children with cystic fibrosis. The inhaled dose did not change with the patient's age or size using both types of nebulizer.

Lung deposition from the Turbuhaler in children with cystic fibrosis

Drug delivery to patients using dry powder inhalers, such as the Turbuhaler, is believed to be influenced by the inspiratory flow used. Clinical studies have indicated that this delivery system can be used effectively by children. However, it is not known how the total and weight-corrected dose delivered to the airways varies with age. A deposition study using technetium-99m (99mTc)-labelled budesonide was performed in order to determine the effect of age on delivery. Twenty one children with cystic fibrosis, aged 4-16 yrs, were recruited. They were clinically stable with normal lung function. Initially, a gamma camera scan was taken in front of a flood source containing 37 MBq of 99mTc. Subsequently, subjects inhaled through a low resistance inspiratory filter connected to a commercially available Turbuhaler. Immediately afterwards they inhaled from a noncommercial Turbuhaler containing budesonide labelled with 99mTc, and then underwent anterior and posterior gamma camera scans. Both Turbuhaler inhalers were attached to a portable spirometer and the peak inspiratory flow through the Turbuhaler was recorded for each inhalation. The total body dose was calculated from the dose deposited on the inspiratory filter connected to the commercial Turbuhaler. Analysis of the gamma camera images provided information on the proportion of the radiolabel delivered to the lungs compared to that deposited in the upper airway and stomach. As expected, a highly significant positive correlation was noted between the peak inspiratory flow generated by the patient through the Turbuhaler and the dose delivered to the lung. Similarly, there was a highly significant positive correlation between age and "total lung dose". However, when total lung dose was corrected for body weight, there was a nonsignificant negative correlation with age. This study suggests that the "weight-corrected lung dose" achieved when children aged > 6 yrs use the Turbuhaler, is largely independent of age. It would appear that the flow-dependent properties of this device are such that the reduced peak inspiratory flow generated by younger children results in a lower dose to the lungs, but that this is off-set by their lower body weight. This is unlikely to be a property of other devices with different flow/drug delivery characteristics.

Aerosol delivery in infants and young children

Despite extensive use of aerosol therapy to treat infants and young children with respiratory disease, our knowledge of factors influencing drug delivery in this age group remains relatively rudimentary. Recent work with filters used in conjunction with pumps or patients have emphasised some of the factors that will maximise the dose inhaled using different devices though results obtained particularly when used with patients should be interpreted with caution and in context. There are few pharmacokinetic or radiolabelled deposition studies on which to base statements regarding dose likely to reach the lungs of children in this age group. Lung function and clinical results suggest that drugs can be delivered via nebulisers and holding chambers with face masks and inevitably performance of such devices will vary. However, factors such as screaming and non-compliance with treatment are likely to influence the lung dose to a great extent. Hence choice of drug delivery system must be based on patient/parent acceptability as much as on theoretical grounds. Aerosol therapy in this age group is further complicated by our lack of knowledge related to the aetiology of recurrent respiratory symptoms in young children and hence it is quite likely that many children are being treated with effective delivery systems but inappropriate therapeutic agents. Much work is still required before we have a clear understanding of the aetiology and pathology of the distinct sub groups of respiratory disease in young children. Until we have a greater understanding in this area together with improved understanding of delivery systems, drug therapy in this age group will remain very much an empirical art.

Effect of electrostatic charge, flow, delay and multiple actuations on the in vitro delivery of salbutamol from different small volume spacers for infants

BACKGROUND

A study was undertaken to determine the influences of electrostatic charge, flow, delay, and multiple actuations on the in vitro delivery of salbutamol generated by a pressurised metered dose inhaler (pMDI) from small volume spacers used in infants.

METHODS

Ten actuations from a salbutamol pMDI were drawn at different flow rates after either single or multiple actuations, with or without delay, through either static or reduced static spacers. An ionic detergent was used to reduce the charge of plastic spacers (Babyhaler, Babyspacer, Aerochamber, Nebuhaler). Electrostatic charge was measured using an electrometer. A multistage liquid impinger was used to determine the particle size distribution of the output of the pMDI through the spacers.

RESULTS

Electrostatic charge on the surface of plastic spacers had the greatest influence on delivery, causing a decrease in drug delivery. Reducing charge by coating the surface with ionic detergent resulted in an increase of 46.5-71.1% (p < 0.001) in small (< 6.8 microns) particle delivery from small volume plastic spacers. Lower flow, delay, and multiple actuations resulted in decreased delivery from static spacers. Lower flow resulted in a decrease of 15% in small (< 9.6 microns) particle delivery. Delay and multiple actuations resulted in a decrease of 40.7% and 76.0%, respectively, in small (< 6.8 microns) particle delivery. The influences of lower flow, delay, and multiple actuations were greatly reduced or even eliminated by reducing charge. However, multiple actuations still resulted in a significant decreased delivery (p < 0.05). The reduced static Nebuhaler had a higher delivery than all small volume spacers.

CONCLUSIONS

Electrostatic charge has a major influence on the delivery of salbutamol from small volume spacers. Using a metal spacer or ionic detergent coating of plastic spacers resulted in no or reduced charge and hence in improved delivery. Lower flow, delay, and multiple actuations played a major part only in static spacers.

Particle size selection device for use with the Turbohaler

BACKGROUND

Drug deposited within the upper airways of patients using dry powder inhalers does not contribute to the therapeutic effect but can result in unwanted local side effects and, when swallowed, may contribute to systemic effects. A chamber has been devised which uses the centrifugal force generated by the Turbohaler to remove large "non-respirable" particles with a view to minimising deposition in the upper airway. An in vitro study was performed to determine whether such a chamber could reduce the dose contained in coarse particles without having a significant effect on the "respirable dose".

METHODS

The mouthpiece of a 200 micrograms Turbohaler was modified to allow a small volume chamber to be attached. The particle size distribution generated by the Turbohaler was assessed using a multi-stage liquid impinger with a flow rate of 60 l/min. The quantity of drug on each stage was quantified using an ultraviolet spectrophotometric technique. For each experiment 10 actuations were used to ensure adequate quantities of drug on each stage. Particles depositing on stages 3 + 4 have a diameter of < 6.8 microns and are arbitrarily referred to as the "respirable dose". The particle size distribution obtained using the Turbohaler (n = 10) was compared with that from the Turbohaler+ chamber (n = 11).

RESULTS

The addition of the chamber resulted in the mean (SD) dose contained in larger "non-respirable" particles depositing on stages 1 + 2 being reduced from 52.2 (12.3) to 29.6 (6.9) micrograms per actuation. However, the chamber did not affect the "respirable" dose. The dose contained in particles with a diameter of < 6.8 microns from the standard Turbohaler was 91.1 (8.9) micrograms compared with 82.4 (18.6) micrograms when used with the chamber.

CONCLUSIONS

These results indicate that it is possible to devise an effective particle size selection device for the Turbohaler. It may be possible to produce such devices for other dry powder inhalers, although the design would need to be tailored to each particular device.

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

BACKGROUND

Jet nubulisers and metered dose inhalers are widely used to deliver aerosolised drugs to the lungs of intubated patients in adult intensive care units. Drug delivery using these systems has been shown to be inefficient and both forms of delivery have the potential to induce paradoxical bronchoconstriction in patients with reactive airways disease.

METHODS

Experiments were carried out to determine whether it was possible to deliver drug from a dry powder delivery system through an endotracheal tube. A 200 micrograms budesonide Turbohaler was enclosed in a chamber which allowed it to be inserted into a ventilator circuit. Experiments were performed with a multistage liquid impinger in which drug was drawn through the Turbohaler and endotracheal tube at 60 l/min providing an index of the maximum drug delivery achievable via this route. A second series of experiments was performed in which the Turbohaler was placed in a ventilator circuit using a Servo 900C volume cycled ventilator. Drug delivered from the Turbohaler during the inspiratory phase was collected on a filter placed between the end of a 9 mm endotracheal tube and a model lung. A tidal volume of 500 ml and inspiratory time of 0.5 seconds was used. Budesonide was assayed using an ultraviolet spectrophotometric assay.

RESULTS

Thirty percent of the nominal dose passed through the endotracheal tube and was collected in the multistage liquid impinger. Mean drug delivery to the filter in the ventilator circuit was 20%.

CONCLUSIONS

This in vitro study indicates that drugs from dry powder inhalers (in this case the Turbohaler) can be satisfactorily delivered through endotracheal tubes and that clinical evaluation of this technique is now indicated.

Factors affecting total and "respirable" dose delivered by a salbutamol metered dose inhaler

BACKGROUND

Many factors contribute to the high variability of doses delivered to the lungs of patients using metered dose inhalers (MDIs). Relatively little attention has been paid to the contribution to this variability of the way in which the MDI is handled before the inhalation manoeuvre. Instruction leaflets often recommend procedures at odds with those used for in vitro testing of the device. The standard protocol for in vitro assessment of salbutamol MDIs involves shaking the MDI vigorously for 30 seconds and wasting the first two actuations. Subsequent actuations are introduced into the testing device at five second intervals. Patient instructions do not include a recommendation to waste the first two actuations and recommend a delay of one minute between actuations. A series of experiments was performed to determine whether such differences might be important.

METHODS

The total and "respirable" doses delivered by a salbutamol MDI (Ventolin, Allen & Hanburys) under various conditions were assessed with a multistage liquid impinger. The quantity of drug deposited on each stage was measured by an ultraviolet spectrophotometric method. The effect on the delivered dose of not shaking the canister, not wasting the first two doses, waiting 30 seconds between actuations, and using multiple rapid actuations was assessed by comparing the results with those obtained using the standard in vitro testing protocol.

RESULTS

Compared with a standard protocol, it was found that not shaking the MDI before use reduced the total and "respirable" dose by 25.5% and 35.7%, respectively. The dose delivered when actuating the MDI at 30 second intervals was no different from that when intervals was no different from that when intervals of five seconds were used. Two actuations separated by one second had no effect on the total dose but reduced the "respirable" dose by 15.8%, while four rapid actuations reduced the total and "respirable" doses by 8.2% and 18.2%, respectively. Storing the MDI stem down reduced the total and "respirable" dose delivered in the first actuation by 25.0% and 23.3% despite shaking the MDI before use.

CONCLUSIONS

MDIs containing drug in suspension must be shaken before use to resuspend the drug contained in the MDI, but shaking does not alter the composition of the suspension in the metering chamber and hence the dose in the first actuation remains low. Very rapid actuations can reduce the dose delivered per actuation, but salbutamol MDIs can be actuated immediately after a 10 second breath holding pause without affecting the dose delivered.

Bronchiolitis. Origins and optimal management

There is currently no prospect of an end to the annual epidemics of acute bronchiolitis, which cause considerable morbidity in previously healthy infants and are a major threat to the well-being of infants with underlying cardiac, respiratory or immunological disease. The respiratory syncytial virus remains the major cause of this condition, and prospects of developing a vaccine remain bleak while our understanding of the viral-host interaction remain incomplete. Treatment of patients with this condition has remained essentially unchanged for more than 30 years. Correction of hypoxia with oxygen, minimal handling to reduce the risk of exhaustion and careful noninvasive monitoring for complications such as apnoea and respiratory failure are the mainstays of management. Mortality in at-risk groups has fallen substantially during the past 10 years. This appears to be due to improved supportive and intensive care. The role of the antiviral agent ribavirin in the improved outcome, if any, is unclear. Other novel therapies have been tried, but none have been shown to significantly alter the natural history of the condition. The only effective preventive intervention currently available is strict adherence to measures designed to prevent nosocomial infection. This condition is likely to remain a continuing challenge to paediatricians for the foreseeable future.

An alternative aerosol delivery system for amiloride

BACKGROUND

The advent of novel treatments such as aerosolized amiloride are potentially useful additions to the therapeutic options available for the treatment of cystic fibrosis. Unfortunately, amiloride and other aerosolized drugs such as antibiotics are generally administered via jet nebulisers which are time consuming to use, and thus limit the acceptance and efficacy of these forms of treatment. In vitro experiments were performed in order to determine whether amiloride could be administered in dry powder form using a Turbohaler.

METHODS

Amiloride was micronised and loaded into 200 micrograms Turbohalers. The dose delivered per actuation and particle size distribution of the generated aerosol were assessed using a flow of 60 l/min through the Turbohaler. The dose of amiloride delivered was measured by collecting the aerosol on a filter and the quantity of drug was assayed by an ultraviolet spectrophotometric method. The particle size distribution was assessed using a Malvern MasterSizer laser particle sizer and compared with that generated by a commercially available 200 micrograms budesonide Turbohaler.

RESULTS

The mean (SD) dose delivered per actuation was 246.3 (40.4) micrograms. The volume median diameter of the amiloride aerosol was 3.80 (0.68) micron compared with 3.07 (1.47) microns for budesonide.

CONCLUSIONS

These results suggest that therapeutic doses of micronised amiloride could be delivered effectively and conveniently as a dry powder aerosol using a Turbohaler.