S. Stick

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 β2-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.

Epithelial inducible nitric oxide synthase activity is the major determinant of nitric oxide concentration in exhaled breath

Background: The fractional concentration of nitric oxide (NO) in exhaled breath (FeNO) is increased in asthma. There is a general assumption that NO synthase (NOS) 2 in epithelium is the main source of NO in exhaled breath. However, there is no direct evidence to support the assumption and data from animal models suggest that non-inducible NOS systems have important roles in determining airway reactivity, regulating inflammation, and might contribute significantly to NO measured in exhaled breath. Methods: Bronchial epithelial cells were obtained from healthy, atopic, and asthmatic children by non-bronchoscopic brushing. Exhaled NO (FeNO) was measured directly using a fast response chemiluminescence NO analyser. RNA was extracted from the epithelial cells and real time polymerase chain reaction was used to determine the expression of NOS isoenzymes. NOS2 was examined in macrophages and epithelial cells by immunohistochemistry. Results: NOS1 mRNA was not detectable. NOS3 mRNA was detected in 36 of 43 samples at lower levels than NOS2 mRNA which was detectable in all samples. The median FeNO was 15.5 ppb (95% CI 10 to 18.1). There was a significant correlation between FeNO and NOS2 expression (R = 0.672, p<0.001). All epithelial cells exhibited NOS2 staining, whereas staining in the macrophages was variable and not related to phenotype. Conclusions: Only NOS2 expression was associated with FeNO in respiratory epithelial cells obtained from children (R = 0.672; p<0.001). This suggests that FeNO variability is largely determined by epithelial NOS2 expression with little contribution from other isoforms.

Acquisition and eradication of P. aeruginosa in young children with cystic fibrosis

When do infants and young children with cystic fibrosis acquire infection with Pseudomonas aeruginosa? Can this be eradicated when first detected? Children <6 yrs of age participated in an annual bronchoalveolar lavage (BAL)-based microbiological surveillance programme in Perth, Australia. When P. aeruginosa was detected, an eradication programme using combination treatment with i.v., oral and nebulised antibiotics was undertaken. Repeat BAL was performed 3 months following treatment, to assess eradication success. P. aeruginosa was detected in 33 (28.4%) children; median (range) age at detection was 30.5 (3.3–71.4) months. P. aeruginosa was mucoid at detection in six (18.2%) out of 33 patients and associated with respiratory symptoms in 16 (48.5%) out of 33 children. In total, 26 children underwent eradication therapy, with P. aeruginosa eradicated in 20 (77%) out of 26 following one eradication cycle and in three (total 88%) additional children following a second cycle. Eradication was associated with a significant decrease in neutrophil elastase and interleukin-1β in BAL fluid 12 months post eradication. Eradication of Pseudomonas aeruginosa infection is achievable in young children with cystic fibrosis for up to 5 yrs using combination i.v., oral and nebulised antibiotic therapy and is associated with reduced pulmonary inflammation 12 months post eradication.

Correlation of forced oscillation technique in preschool children with cystic fibrosis with pulmonary inflammation

Background: Lung disease in cystic fibrosis (CF) is established in early childhood with recurrent bacterial infections and inflammation. Using spirometry, the effect of this early lung damage cannot be measured until a child is 6 years of age when some irreversible lung damage may already have occurred. Techniques for measurement of lung function in infants and young children include raised volume rapid thoracic compression (RVRTC) and low frequency forced oscillation (LFFOT). The aim of this study was to investigate the role of inflammation and infection on a population of infants and young children with CF and to determine whether lung function in this population (measured by LFFOT) is affected by early lung disease. Methods: Lung function was measured by LFFOT in 24 children undergoing bronchoalveolar lavage (BAL) on 27 occasions as part of an annual programme while still under general anaesthesia. Following lung function testing, three aliquots of saline were instilled into the right middle or lower lobe. The first aliquot retrieved was processed for the detection of microbes, and the remaining aliquots were pooled to assess inflammatory markers (cytology, IL-8, NE, LTB4). Results: Inflammation (percentage and number of neutrophils) was significantly higher in children with infections (p<0.001, p = 0.04, respectively), but not in those with symptoms. Several markers of inflammation significantly correlated with LFFOT parameters (R, G, and η). Conclusion: Infections and inflammation are established before symptoms are apparent. Inflammation is correlated with measures of parenchymal changes in lung function measured by LFFOT.

The effects of inhaled beclomethasone dipropionate on lung function and histamine responsiveness in recurrently wheezy infants.

Inhaled steroids improve pulmonary function and bronchial responsiveness in older asthmatics. Data from studies using subjective outcome measures to determine the effectiveness of inhaled steroids in infants with recurrent wheezing are equivocal. Therefore, this study tested the hypothesis that beclomethasone dipropionate improves pulmonary function, including bronchial responsiveness to histamine, in recurrently wheezy infants. The study was double blind, placebo controlled lasting nine weeks. After the first baseline week, pulmonary function was measured using the rapid thoracoabdominal compression technique and bronchial responsiveness assessed with a histamine challenge test. Infants were then randomly allocated to receive doses of placebo or beclomethasone dipropionate (100 micrograms/puff) from metered aerosols. Two puffs of test aerosol were administered twice daily for eight weeks via a large volume spacer fitted with a facemask. Symptoms were recorded daily and pulmonary function and bronchial responsiveness assessed at the end of the treatment period; 50 infants, median age 12 months (range 5 to 18 months), were recruited. Twenty three in the beclomethasone dipropionate group and 15 in the placebo group completed the study and had pairs of pulmonary function measurements. Three were probable treatment failures (one beclomethasone dipropionate, two placebo), three were possible treatment failures (placebo), and others were non-compliant with study protocol. Baseline variables were not significantly different between those infants who completed the study and those who did not. Beclomethasone dipropionate and placebo groups were similar in all respects at baseline. Lung function and symptoms improved for both groups of infants during the study. Bronchial responsiveness increased significantly in the placebo group but there were not statistically significant differences between groups for any of the other outcome measures. It is concluded that beclomethasone dipropionate (400 microgram daily) via a large volume spacer does not significantly improve lung function or symptoms in recurrently wheezy infants but might hav a beneficial effect on bronchial responsiveness.

Selection of housekeeping genes for real-time PCR in atopic human bronchial epithelial cells

The stability of housekeeping genes (HKGs) is critical when performing real-time quantitative PCR. To date, the stability of common HKGs has not been systematically compared in human airway epithelial cells (AEC) in normal and atopic subjects. Expression levels of 12 HKGs were measured in AECs from a cohort of 30 healthy atopic nonasthmatic or atopic asthmatic children. Gene expression stability was determined using three different Visual Basic for Applications applets (geNorm, NormFinder and BestKeeper). All 12 HKGs were expressed in AECs. However, the hypoxanthine ribosyltransferase and TATA-binding protein genes were excluded from further analysis due to low expression levels. The cyclophilin A gene was ranked the most stable by all three methods. The expression levels of the β-actin and glyceraldehyde-3-phosphate dehydrogenase genes were significantly different between the three groups of patients, with atopic asthmatics showing the highest expression levels for both genes. The results suggest that the cyclophilin A gene is the most suitable housekeeping gene analysed for expression studies utilising uncultured bronchial airway epithelial cells from healthy and asthmatic children, and highlight the importance of validating housekeeping genes for each experimental model.

Respiratory impedance in children with cystic fibrosis using forced oscillations in clinic

Measurement of lung function is an important component of clinical management in cystic fibrosis (CF), but has been difficult in young children. The present study aimed to characterise the utility of the forced oscillation technique for measurement of lung function in preschool-aged children with CF in a routine clinical setting. Lung function was assessed in 56 young children (aged 2–7 yrs) with CF. Respiratory system resistance (Rrs) and reactance (Xrs) at 6, 8 and 10 Hz were measured and expressed as Z-scores. Children were classified as asymptomatic or symptomatic based on an administered respiratory questionnaire and physical examination at the time of testing. Between-test repeatability was assessed in 25 children. Measurement of lung function using the forced oscillation technique was feasible in the CF clinic. The children with CF, as a group, had Z-scores for Rrs at 6 Hz (Rrs,6) Rrs,8, Rrs,10, Xrs at 6 Hz (Xrs,6) and Xrs,8 that were significantly different from zero. Children with current symptoms showed significantly decreased Xrs and increased Rrs,6 compared with asymptomatic children. Measurement of lung function using the forced oscillation technique is feasible in young children with cystic fibrosis in a clinical setting. The technique has the potential to improve knowledge concerning early cystic fibrosis lung disease.

Respiratory pattern changes in sleep in children on vagal nerve stimulation for refractory epilepsy.

BACKGROUND An altered breathing pattern in sleep, over two to three weeks, reported by the parents of a child on Vagal Nerve Stimulation (VNS) therapy for refractory epilepsy, prompted a sleep study in him. His polysomnography (PSG) revealed respiratory irregularity concordant with VNS activation. Dyspnoea is a well recognised and reported side effect of the VNS. However there are only a few studies looking at respiration in sleep with VNS. We therefore undertook PSGs in seven other children on VNS. METHODS Sleep studies were undertaken, in accordance with standard clinical practice. Sleep and apnoeas and hypopneas were scored in accordance with conventional criteria. Respiratory pattern changes in sleep (RPCS) with VNS were looked for. RESULTS Respiratory pattern changes in sleep were seen during PSG in seven of eight children on VNS for refractory epilepsy. Decreased effort and tidal volume occurred in seven children, concordant with VNS activation. In one child, this was associated with a fall in respiratory rate, i the other six children with an increase. No study showed an apnoea/hypopnoea index in the abnormal range. The RPCS were not associated with significant hypoxia or hypercapnoea. CONCLUSION Our results suggest that RPCS occur in most children with VNS. This is not surprising in view of the significant influence vagal afferents have on respiratory control centres. The RPCS did not appear to have a clinical impact in our group. However further investigations are suggested to explore this phenomenon, especially in patients with sleep apnoea syndromes or compromised respiratory function.

Value of serology in predicting Pseudomonas aeruginosa infection in young children with cystic fibrosis

Background Early detection of Pseudomonas aeruginosa is essential for successful eradication. The accuracy of serum antibodies against specific and multiple P aeruginosa antigens at predicting lower airway infection in young children with cystic fibrosis (CF) was investigated. Methods A commercial P aeruginosa multiple antigen (MAg) ELISA and an in-house exotoxin A (ExoA) ELISA were compared in two populations: a discovery population of 76 children (0.1–7.1 years) undergoing annual bronchoalveolar lavage (BAL)-based microbiological surveillance and a test population of 55 children (0.1–5.6 years) participating in the Australasian CF Bronchoalveolar Lavage Trial. Results In the discovery population, P aeruginosa was cultured from BAL fluid (≥105 colony-forming units (cfu)/ml) in 15/76 (19.7%) children (median age 1.88 years). Positive MAg and ExoA serological results were found in 38 (50.0%) and 30 (39.5%) children, respectively. Positive (PPV) and negative (NPV) predictive values for serology at diagnosing P aeruginosa infection (≥105 cfu/ml) were 0.14 and 0.99 respectively (MAg assay) and 0.11 and 0.98 (ExoA assay). In the test population, P aeruginosa was cultured from BAL fluid (≥105 cfu/ml) in 16/55 (29.1%) children (median age 1.86 years) and from oropharyngeal swabs in 32/36 (88.9%). Positive MAg and ExoA serology was detected in 19 (34.5%) and 33 (60.0%) children, respectively. The PPV and NPV of serology were 0.26 and 0.94 respectively (MAg assay) and 0.19 and 0.98 (ExoA assay) and were marginally higher for oropharyngeal cultures. Conclusions Measuring serum antibody responses against P aeruginosa is of limited value for detecting early P aeruginosa infection in young children with CF.

Exhaled nitric oxide is not reduced in infants with cystic fibrosis

Fractional exhaled nitric oxide (FeNO) has been reported to be reduced in cystic fibrosis (CF) patients. However, data from young children are conflicting and it is not clear whether this is a primary feature of the disease or a secondary response. The present study compared FeNO between CF and healthy infants using a validated single-breath technique. A total of 23 healthy infants (11 females; mean age 40.1 weeks) and 18 infants with CF (nine females; 64.9 weeks) underwent tests of lung function and FeNO. Bronchoalveolar lavage (BAL) was collected from all CF infants 2–5 days after lung function testing. There was no significant difference in FeNO between the CF and healthy infants (geometric mean: 23.1 parts per billion (ppb) and 17.0 ppb, respectively). There was an inverse relationship between age and FeNO in the CF patients, but not in the healthy group. Within the CF group, there was no association between FeNO and any marker of airway inflammation measured in the BAL. Exhaled nitric oxide is not reduced in cystic fibrosis infants, but does decrease with age. The current data indicate that FeNO is not a good marker of airway inflammation in cystic fibrosis.