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.

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.

How free of tobacco smoke are 'smoke-free' homes?

The risks of exposure to environmental tobacco smoke (ETS) are well established and 'harm reduction' strategies such as smoking outside to protect infants and children from exposure to ETS have been advocated for some time. The aim of this study was to assess the validity of self-reported smoking levels in residential settings. The participants were families (n = 92) randomly selected from lower socioeconomic areas of Perth, Western Australia. Each household was monitored for vapor phase nicotine and particulates with an aerodynamic diameter of < or = 10 microm (PM(10)). Of the 42% (39) households who reported that someone smoked cigarettes at home, only four (4%) said that smoking occurred inside the house. There was a 'moderate' agreement between parental-reported tobacco smoking and levels of nicotine (kappa = 0.55, P < 0.01). There were significant differences in the median levels of air nicotine (P < 0.01) and PM(10) (P < 0.05) between households in which smoking was reported as only occurring outside, and the smoke-free households.

PRACTICAL IMPLICATIONS

The study outcome suggests that a strategy based on the separation of children and smoking activity is inadequate to protect the former from ETS at home, and that health professionals should give parents unambiguous advice to give up smoking in order to make their homes a completely smoke-free environment.

Beta2-Adrenoceptor polymorphisms and asthma phenotypes: interactions with passive smoking

The aim of the present study was to assess the effects of possible interactions between beta(2)-adrenoceptor gene polymorphisms and passive smoking on forced expiratory volume in one second (FEV(1)), forced vital capacity (FVC) and exhaled nitric oxide (eNO) in children aged 11 yrs. A cross-sectional analysis of the longitudinal cohort was conducted for associations between beta(2)-adrenoceptor gene polymorphisms and lung function and eNO with regard to passive smoking. Among children exposed to tobacco smoke, those with Arg16 (at least one Arg allele) exhibited lower adjusted mean FEV(1) (2.19 versus 2.38 L) and FVC (2.43 versus 2.64 L) than Gly16 homozygotes. Those with Gln27 (at least one Gln allele) also exhibited a lower adjusted mean FEV(1) relative to Glu27 homozygotes (2.24 versus 2.39 L). Among children with no exposure to smoking, those with Arg16 or Gln27 showed lower adjusted geometric mean eNO levels compared with Gly16 homozygotes (15.4 versus 30.9 ppb) and Glu27 homozygotes (18.0 versus 49.7 ppb). In conclusion, passive smoking had a significant effect on associations between beta(2)-adrenoceptor gene polymorphisms and asthma-related phenotypes, enhancing the relationship between Arg16 and lung function and removing the relationship between Arg16 or Gln27 and exhaled nitric oxide levels.

Indoor environmental quality in a 'low allergen' school and three standard primary schools in Western Australia

To investigate indoor environmental quality in classrooms, assessments were undertaken in a 'low allergen' school and three standard primary schools in Western Australia. Dust allergens, air pollutants and physical parameters were monitored in the four schools at four times (summer school term, autumn holiday, winter school term and winter holiday) in 2002. The levels of particulate matter (PM(10)) and volatile organic compounds were similar between the four primary schools. Although slightly decreased levels of dust-mite and cat allergens were observed in the 'low allergen' school, the reductions were not statistically significant and the allergen levels in all schools were much lower than the recommended sensitizing thresholds. However, significantly lower levels of relative humidity and formaldehyde level during summer-term were recorded in the 'low allergen' school. In conclusion, the evidence here suggests that the 'low allergen' school did not significantly improve the indoor environmental quality in classrooms. Practical Implications School is an important environment for children in terms of exposure to pollutants and allergens. By assessing the levels of key pollutants and allergens in a low allergen school and three standard primary schools in Western Australia, this study provides useful information for implementation of healthy building design that can improve the indoor environment in schools.

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.

Association of domestic exposure to volatile organic compounds with asthma in young children

AIM

To investigate the association between domestic exposure to volatile organic compounds (VOCs) and asthma in young children.

METHODS

A population based case-control study was conducted in Perth, Western Australia in children aged between 6 months and 3 years. Cases (n = 88) were children recruited at Princess Margaret Hospital accident and emergency department and discharged with asthma as the primary diagnosis; 104 controls consisted of children from the same age group without an asthma diagnosis identified through the Health Department of Western Australia. Information regarding the health status of the study children and characteristics of the home was collected using a standardised questionnaire. Exposure to VOCs, average temperature and relative humidity were measured in winter and summer in the living room of each participating household.

RESULTS

Cases were exposed to significantly higher VOC levels (microg/m3) than controls (p<0.01). Most of the individual VOCs appeared to be significant risk factors for asthma with the highest odds ratios for benzene followed by ethylbenzene and toluene. For every 10 unit increase in the concentration of toluene and benzene (microg/m3) the risk of having asthma increased by almost two and three times, respectively.

CONCLUSIONS

Domestic exposure to VOCs at levels below currently accepted recommendations may increase the risk of childhood asthma. Measurement of total VOCs may underestimate the risks associated with individual compounds.

Home oxygen therapy after preterm birth in Western Australia

OBJECTIVES

To review our management of infants discharged home receiving supplemental oxygen. Stable preterm infants receive low flow O(2) by nasal cannulae aiming for SaO(2) of > or = 95%. Oxygen-dependent infants must pass an air test (ability to maintain SaO(2) > 80% during 4 h disconnection from oxygen) before discharge home with supplemental oxygen. A sleep study is performed before nocturnal O(2) is ceased.

METHODS

Infants less than 33 weeks gestational age (GA) who were admitted January 1999-June 2001 and discharged home with supplemental oxygen were identified through the databases and medical records of the King Edward Memorial/Princess Margaret Hospitals. The data collected were compared with an audit performed a decade earlier.

RESULTS

Ninety-three infants were discharged home with supplemental oxygen between 1999 and 2001 (10% neonatal intensive care unit admissions less than 33 weeks GA; median GA 26 weeks (interquartile range 25-28). All infants had an air test before discharge: 63% failed the first air test and 30% at least two air tests. The median delay between the first air test and discharge was 2 weeks. The median postmenstrual age at discharge was 40 weeks gestation (interquartile range 38-41). Ninety infants had a sleep study before nocturnal oxygen was ceased and nine failed the first sleep study. Hospital readmission rate was 60%. More preterm infants (less than 33 weeks) were discharged with supplemental oxygen in 1999-2001 (10%, n = 96 in 1999-2001) than in 1987-1992 (2.5%, n = 53) and this was associated with an earlier discharge (40 vs 44 weeks postmenstrual age), lower oxygen requirements at discharge (60 vs 125 mL/min), earlier discontinuation of daytime and nocturnal oxygen (1 vs 4 months postmenstrual age and 2.5 vs 6 months postmenstrual age) and no increase in readmission rate (64% vs 60%). The incidence of bronchopulmonary dysplasia for these infants has remained stable at 20%.

CONCLUSION

Our home oxygen programme, based on an air test predischarge and a sleep study prediscontinuation of nocturnal oxygen, facilitates early discharge home. Our data suggest that over the last decade, bronchopulmonary dysplasia is associated with less impairment in lung function. Further evidence from randomized clinical trials is required to determine optimal target range for oxygen saturation in preterm infants.

Pediatric origins of adult lung disease. 1. The contribution of airway development to paediatric and adult lung disease

In summary, factors that affect airway growth early in development appear to cause physiological effects that can be persistent. Reduced airway function early in life does not necessarily result in persistent symptoms, but the long term effects and impact on the development of chronic airflow limitation in adults are yet to be determined. Generally, long term sequelae seem to be related to the severity of the initial insult, but the development of persistent increased bronchial responsiveness is an independent risk factor for symptoms and abnormal lung function in later life. In addition, there appear to be separate genetic factors that influence atopy, airway development, and bronchial responsiveness.

Raised exhaled nitric oxide in healthy children is associated with domestic formaldehyde levels

Exposure to domestic levels of formaldehyde has been associated with adverse respiratory symptoms in both adults and children. The underlying mechanisms responsible for these findings have not been established. In order to investigate possible inflammatory effects of formaldehyde at levels typically found in the home, we measured exhaled nitric oxide (eNO) in 224 healthy children 6 to 13 yr of age (116 girls) and monitored formaldehyde levels in their homes. Formaldehyde was monitored using a passive sampling technique. Exhaled NO was measured directly into a fast response chemiluminescence nitric oxide analyzer. The children also undertook a lung function (spirometry) test. There was no effect of formaldehyde levels measured in homes on spirometric variables. However, eNO levels were significantly elevated in children living in homes with average formaldehyde levels >/= 50 ppb. Exhaled NO levels (geometric mean) were 15.5 ppb (95% CI: 10.5 to 22.9 ppb) for children from homes with formaldehyde concentrations >/= 50 ppb compared with 8.7 ppb (7.9 to 9.6) for children from homes with formaldehyde concentrations < 50 ppb (p < 0.05). These results suggest that exposure to formaldehyde in homes may invoke a subclinical inflammatory response in the airways of healthy children.

Is breathing in infants chaotic? Dimension estimates for respiratory patterns during quiet sleep

We describe an analysis of dynamic behavior apparent in times-series recordings of infant breathing during sleep. Three principal techniques were used: estimation of correlation dimension, surrogate data analysis, and reduced linear (autoregressive) modeling (RARM). Correlation dimension can be used to quantify the complexity of time series and has been applied to a variety of physiological and biological measurements. However, the methods most commonly used to estimate correlation dimension suffer from some technical problems that can produce misleading results if not correctly applied. We used a new technique of estimating correlation dimension that has fewer problems. We tested the significance of dimension estimates by comparing estimates with artificial data sets (surrogate data). On the basis of the analysis, we conclude that the dynamics of infant breathing during quiet sleep can best be described as a nonlinear dynamic system with large-scale, low-dimensional and small-scale, high-dimensional behavior; more specifically, a noise-driven nonlinear system with a two-dimensional periodic orbit. Using our RARM technique, we identified the second period as cyclic amplitude modulation of the same period as periodic breathing. We conclude that our data are consistent with respiration being chaotic.

Decreased epinephrine responses to hypoglycemia during sleep

BACKGROUND

In patients with type I diabetes mellitus, hypoglycemia occurs commonly during sleep and is frequently asymptomatic. This raises the question of whether sleep is associated with reduced counterregulatory-hormone responses to hypoglycemia.

METHODS

We studied the counterregulatory-hormone responses to insulin-induced hypoglycemia in eight adolescent patients with type I diabetes and six age-matched normal subjects when they were awake during the day, asleep at night, and awake at night. In each study, the plasma glucose concentration was stabilized for 60 minutes at approximately 100 mg per deciliter (5.6 mmol per liter) and then reduced to 50 mg per deciliter (2.8 mmol per liter) and maintained at that concentration for 40 minutes. Plasma free insulin, epinephrine, norepinephrine, cortisol, and growth hormone were measured frequently during each study. Sleep was monitored by polysomnography.

RESULTS

The plasma glucose and free insulin concentrations were similar in both groups during all studies. During the studies when the subjects were asleep, no one was awakened during the hypoglycemic phase, but during the final 30 minutes of the studies when the subjects were awake both the patients with diabetes and the normal subjects had symptoms of hypoglycemia. In the patients with diabetes, plasma epinephrine responses to hypoglycemia were blunted when they were asleep (mean [+/-SE] peak plasma epinephrine concentration, 70+/-14 pg per milliliter [382+/-76 pmol per liter]; P=0.3 for the comparison with base line), as compared with when they were awake during the day or night (238+/-39 pg per milliliter [1299+/-213 pmol per liter] P=0.004 for the comparison with base line, and 296+/-60 pg per milliliter [1616+/-327 pmol per liter], P=0.004, respectively). The patients' plasma norepinephrine responses were also reduced during sleep, whereas their plasma cortisol concentrations did not increase and their plasma growth hormone concentrations increased slightly. The patterns of counterregulatory-hormone responses in the normal subjects were similar.

CONCLUSIONS

Sleep impairs counterregulatory-hormone responses to hypoglycemia in patients with diabetes and normal subjects.

Nocturnal hypoglycaemia and sleep disturbances in young teenagers with insulin dependent diabetes mellitus

OBJECTIVE

To determine the effect of nocturnal hypoglycaemia on sleep architecture in adolescents with insulin dependent diabetes mellitus (IDDM).

DESIGN

20 adolescents with IDDM (mean age 12.8 years, mean glycated haemoglobin (HbA1c) 8.9%) were studied on one night. Plasma glucose was measured every 30 minutes and cortisol and growth hormone levels every 60 minutes. Sleep was recorded using standard polysomnographic montages, and sleep architecture was analysed for total sleep time, stages 1-4, rapid eye movement, fragmentation, and arousals.

RESULTS

Six subjects (30%) became hypoglycaemic (five subjects < 2.5 mmol/l), with one being symptomatic. There were no differences in age, HbA1c, duration of diabetes, or insulin regimen between hypoglycaemic and non-hypoglycaemic subjects. Hypoglycaemia was not predicted by glucose measurements before bed. There was no detectable rise in plasma cortisol or growth hormone concentrations during hypoglycaemia. Sleep architecture was not disturbed by nocturnal hypoglycaemia with no differences found in sleep stages, fragmentation, or arousals.

CONCLUSIONS

Nocturnal hypoglycaemia is a common and usually asymptomatic complication of treatment in adolescents with IDDM. Moderate hypoglycaemia has not been shown to affect sleep architecture adversely. These findings are consistent with, and may explain, the observation that severe hypoglycaemia, with consequent seizure activity, is more common at night than during the day. Counterregulatory hormone responses to nocturnal hypoglycaemia may be less marked than with similar degrees of diurnal hypoglycaemia.

Transmission of pressure across the chest wall during the rapid thoracic compression technique in infants

During the rapid thoracic compression maneuver in infants, the transmission of pressure from compression jacket to pleural space and airway is less at functional residual capacity than at end inspiration. To examine whether reduced pressure transmission at functional residual capacity vs. higher lung volumes is explained by passive characteristics of the chest wall rather than by respiratory muscle activity, we assessed the pressure transmitted across the chest wall in nine anesthetized infants and young children after muscle relaxation. We measured esophageal and airway occlusion pressure during chest compressions at different lung volumes determined by varying distending pressure. In six subjects studied under static conditions, there was an approximately linear relationship between distending pressure and the proportion of pressure transmitted to the airway and esophagus from the compression jacket. The mean r2 value (95% confidence interval) was 0.80 (0.09) for pressure transmission to the airway and 0.85 (0.04) for pressure transmission to the esophagus. This relationship between lung volume and pressure transmission observed under static conditions was also demonstrated dynamically. Thus the reduced transmission of pressure from compression jacket to airway and pleural space at low lung volumes occurs independently of respiratory muscle activity.

Induction of epidermal NAD(P)H:quinone reductase by chemical carcinogens: a possible mechanism for the detoxification

NAD(P)H:quinone reductase, which plays an important role in the detoxification of carcinogenic metabolites as well as oxidative cellular damage, was found to be present in epidermal cytosol where its specific activity far exceeds (140-160%) the corresponding hepatic value. The effect of topical application of crude coal tar, 3-methylcholanthrene and polychlorinated biphenyl Aroclor 1254, on epidermal and hepatic cytosolic NAD(P)H:quinone reductase activities was investigated in neonatal rats, Sencar and athymic nude mice. A single topical application of each agent resulted in significant increases in epidermal (185%-389%) and hepatic (150-255%) enzyme activities. This inducible enzyme may play an important role in the detoxification of reactive quinone species during the course of malignant neoplasia and against oxidative cellular damage in skin.