Bronchial responsiveness and symptoms in 5-6 year old children: a comparison of a direct and indirect challenge

Monitoring asthma in childhood: lung function, bronchial responsiveness and inflammation

This review focuses on the methods available for measuring reversible airways obstruction, bronchial hyperresponsiveness (BHR) and inflammation as hallmarks of asthma, and their role in monitoring children with asthma. Persistent bronchial obstruction may occur in asymptomatic children and is considered a risk factor for severe asthma episodes and is associated with poor asthma outcome. Annual measurement of forced expiratory volume in 1 s using office based spirometry is considered useful. Other lung function measurements including the assessment of BHR may be reserved for children with possible exercise limitations, poor symptom perception and those not responding to their current treatment or with atypical asthma symptoms, and performed on a higher specialty level. To date, for most methods of measuring lung function there are no proper randomised controlled or large longitudinal studies available to establish their role in asthma management in children. Noninvasive biomarkers for monitoring inflammation in children are available, for example the measurement of exhaled nitric oxide fraction, and the assessment of induced sputum cytology or inflammatory mediators in the exhaled breath condensate. However, their role and usefulness in routine clinical practice to monitor and guide therapy remains unclear, and therefore, their use should be reserved for selected cases.

Assessing direct and indirect airway hyperresponsiveness in children using impulse oscillometry

BACKGROUND

Airway hyperresponsiveness (AHR) is a hallmark of asthma but its assessment is usually restricted to older children who are capable of performing the maneuvers involved in spirometry. In younger children, a feasible option to perform the lung function measurement is impulse oscillometry (IOS), which requires less cooperation.

OBJECTIVE

To evaluate whether assessment of AHR by IOS could differentiate children with various obstructive symptoms from one another.

METHODS

One hundred twenty-one children (median age 6.0 years, range 3.7-8.1 years) were examined: 31 with probable asthma characterized by current troublesome lung symptoms, 61 with a history of early wheezing disorder (recurrent wheezing ≤24 months of age), 15 with a history of bronchopulmonary dysplasia, and 14 healthy controls. Indirect AHR was assessed by exercise and mannitol challenge tests, and direct AHR was assessed with methacholine using IOS. AHR to exercise was defined as an increase of at least 40% in respiratory resistance at 5 Hz. In the mannitol and methacholine challenges, the dose causing an increase of 40% in respiratory resistance at 5 Hz was calculated.

RESULTS

AHR to exercise was good at differentiating children with current troublesome lung symptoms from those in the other groups (P < .001). AHR to methacholine separated children with current troublesome lung symptoms, early wheezing disorder, and bronchopulmonary dysplasia from the controls (P < .001), whereas the mannitol test did not distinguish among the study groups (P = .209).

CONCLUSION

The methacholine and exercise challenge tests with IOS identify children with probable asthma characterized by troublesome lung symptoms and therefore may represent a practical aid in the evaluation of AHR in young children.

Spirometry and forced oscillations in the detection of airway hyperreactivity in asthmatic children

BACKGROUND

Provocation tests are routinely used to detect airway hyperreactivity (AH) in the diagnosis of asthma. We compared the sensitivities of the forced oscillation technique (FOT) and spirometry in the detection of AH in asthmatic children.

METHODS

FOT and spirometry were performed in 20 asthmatic children (aged 5-18 years) following aerosolized histamine and methacholine at an interval of 2 weeks. The respiratory system input impedance was measured by FOT; the resistance at 6 Hz (R(6) ), the average resistance between 4 and 24 Hz, the area under the reactance curve (AX) and the resonant frequency were extracted from these recordings. Spirometry was used to obtain forced expiratory volumes and flow parameters.

RESULTS

Following provocation with the two agonists, the FOT detected the airway response as early as spirometry. When the greater variability of the impedance parameters was taken into account, the two methods were observed to have similar sensitivities. Among the lung function parameters studied, AX and R(6) were the most sensitive for the demonstration of AH.

CONCLUSIONS

Our findings demonstrate that FOT is as suitable as spirometry for the measurement of bronchoconstriction and thus it may be considered for the detection of AH in asthmatic children. Since its application requires minimal cooperation, this approach imposes less stress and may be particularly favorable in the diagnosis of asthma at a young age.

Salmeterol and fluticasone in young children with multiple-trigger wheeze

BACKGROUND

Treatment guidelines recommend using an inhaled corticosteroid (ICS) plus a long-acting β(2)-agonist (LABA) for childhood asthma when the symptoms are not controlled by ICS alone, but the appropriate use of LABAs in children continues to be debated.

OBJECTIVE

To compare the efficacy of an inhaled salmeterol and fluticasone propionate combination, 50/100 μg twice daily, with fluticasone propionate, 100 μg twice daily, or salmeterol, 50 μg twice daily, in children with multiple-trigger wheeze.

METHODS

A total of 105 children 4 to 7 years of age with multiple-trigger wheezing based on respiratory symptoms and bronchodilator responsiveness and/or exercise-induced bronchoconstriction without a viral cold were randomized to salmeterol-fluticasone, fluticasone propionate alone, or salmeterol alone via a metered-dose inhaler and a spacer device for 8 weeks. The primary efficacy outcome was exhaled nitric oxide level. Secondary outcomes were lung function measurements via impulse oscillometry, respiratory symptoms, and rescue medication use.

RESULTS

The exhaled nitric oxide levels decreased after all treatments, significantly more so after salmeterol-fluticasone and fluticasone than with salmeterol (adjusted geometric means at 8 weeks: salmeterol-fluticasone, 9.4 ppb; fluticasone, 9.3 ppb; salmeterol, 13.9 ppb; salmeterol-fluticasone vs salmeterol, P = .02; fluticasone vs salmeterol, P = .01). No treatment differences were found with respect to respiratory symptoms or median rescue use. Salmeterol-fluticasone resulted in a small but statistically significant improvement in baseline lung function compared with fluticasone. All treatments were equally well tolerated.

CONCLUSION

The effects of salmeterol-fluticasone and fluticasone were comparable, although lung function improvement was better with salmeterol-fluticasone than with fluticasone alone. There is no obvious benefit in initiation therapy with salmeterol-fluticasone rather than fluticasone alone in the treatment of steroid-naive children with multiple-trigger wheeze.

TRIAL REGISTRATION

Pathway of clinical trial registry of Helsinki University:http://www.hus.fi/?Path=1;28;2530;9899;9900;23618;23903;33578.

Application of a shortened inhaled adenosine-5'-monophosphate challenge in young children using the forced oscillation technique

BACKGROUND

Adenosine-5'-monophosphate (AMP) is an indirect challenge agent thought to reflect allergic airway inflammation. The forced oscillation technique (FOT) is ideal for use in young children and is suitable for inhaled challenge studies in patients who are in this age group. We assessed the agreement between a shortened and a standard AMP challenge and the repeatability of the shortened AMP challenge using FOT as a primary outcome variable.

METHODS

Eighteen children completed a shortened and a standard AMP challenge, and 20 children completed repeated shortened AMP challenges. The children inhaled nebulized AMP tidally for 2 min, following which the presence of wheeze and pulse oximetric saturation (Spo(2)) was recorded prior to FOT measurement. Testing continued until the maximum dose was reached or until wheeze, a decrease in Spo(2) to < 90%, or an increase in respiratory resistance at 8 Hz of 2.0 hPa/s/L or 30% was noted. Concordance was assessed as a binary response, and agreement in provocation concentrations (PCs) causing a response was assessed with intraclass correlations.

RESULTS

There was a high degree of concordance between the shortened and standard AMP protocols (94%) and repeated shortened AMP protocols (100%). The mean log(10) PCs displayed a high degree of agreement for both AMP protocols, with intraclass correlation coefficients of 0.94 (95% confidence interval, 0.85 to 0.98) and 0.94 (95% confidence interval, 0.82 to 0.98), respectively.

CONCLUSIONS

We demonstrated that a shortened AMP challenge that can be applied to young children is comparable to the standard AMP challenge and is highly repeatable. Further studies in young children to assess the clinical role of a shortened AMP challenge using FOT are required.

Exercise-induced changes in respiratory impedance in young wheezy children and nonatopic controls

Exercise-induced bronchoconstriction (EIB) is a specific sign of active asthma, but its assessment in young children may be difficult with lung function techniques requiring active cooperation. The aim of the study was to assess the normal pattern of exercise-induced responses of respiratory impedance by using impulse oscillometry (IOS), and to investigate how these responses discriminate wheezy children from control subjects. IOS measurements were performed in a consecutive sample of wheezy children aged 3-7 years (n = 130) and in an aged matched control group of nonatopic children without respiratory symptoms (n = 79) before and after a free running test. After exercise, wheezy children showed significantly larger responses in respiratory resistance (Rrs5), reactance (Xrs5), and the resonance frequency (Fr) than the control subjects. In the control group, the upper 95% confidence limit of the maximal change was 32.5% for Rrs5, 85.7% for Xrs5, and 53.1% for Fr. By using analysis of receiver operating characteristics, the change in Rrs5 distinguished the wheezy children from the control subjects more effectively than change in Xrs5 or Fr. In wheezy children, the response was significantly effected by the outdoor temperature and exercise intensity in terms of maximum heart rate. In conclusion, an increase of 35% in Rrs5 after a free running test can be regarded as an abnormal response. Wheezy children show an enhanced airway response, which is clearly distinguishable from the control subjects. IOS is a feasible method to detect EIB in young children.

Bronchial responsiveness to methacholine and adenosine 5'-monophosphate in atopic and non-atopic preschool children with recurrent wheezing

BACKGROUND

It is well known that atopy is a major determinant of bronchial hyper-responsiveness (BHR) in both asymptomatic and asthmatic children. However, the relationship between atopy and BHR has not been well studied in preschool children with wheezing. BHR is usually measured by bronchial challenges using direct and indirect stimuli.

OBJECTIVE

The aim of this study was to investigate whether atopic and non-atopic preschool wheezers display similar or different BHR profiles for direct and indirect stimuli.

METHODS

Methacholine and adenosine 5'-monophosphate (AMP) bronchial challenges were performed in 4 to 6-year-old children with recurrent wheezing, using a modified auscultation method. The end-point was defined as the appearance of wheezing and/or oxygen desaturation. Atopy was determined to be present when a child had at least one positive reaction to a panel of 13 common airborne allergens in the presence of positive and negative controls.

RESULTS

A positive response to methacholine (an end-point concentration < or =8 mg/mL) was observed in 89.3% (50/56) of atopic wheezers and in 83.8% (31/37) of non-atopic wheezers (P=0.44) for the difference. By contrast, the frequency of a positive response to AMP (an end-point concentration < or =200 mg/mL) was significantly higher in the atopic group (47/56, 83.9%) compared with the non-atopic group (12/37, 32.4%; P<0.01).

CONCLUSION

While a majority of both atopic and non-atopic preschool wheezers were hyper-responsive to methacholine, atopic subjects were more hyper-responsive to AMP than non-atopic subjects. These findings suggest that atopic and non-atopic wheeze in preschool children are related to distinctive pathophysiologic pathways.

Cough: are children really different to adults?

Worldwide paediatricians advocate that children should be managed differently from adults. In this article, similarities and differences between children and adults related to cough are presented. Physiologically, the cough pathway is closely linked to the control of breathing (the central respiratory pattern generator). As respiratory control and associated reflexes undergo a maturation process, it is expected that the cough would likewise undergo developmental stages as well. Clinically, the 'big three' causes of chronic cough in adults (asthma, post-nasal drip and gastroesophageal reflux) are far less common causes of chronic cough in children. This has been repeatedly shown by different groups in both clinical and epidemiological studies. Therapeutically, some medications used empirically for cough in adults have little role in paediatrics. For example, anti-histamines (in particular H1 antagonists) recommended as a front-line empirical treatment of chronic cough in adults have no effect in paediatric cough. Instead it is associated with adverse reactions and toxicity. Similarly, codeine and its derivatives used widely for cough in adults are not efficacious in children and are contraindicated in young children. Corticosteroids, the other front-line empirical therapy recommended for adults, are also minimally (if at all) efficacious for treating non-specific cough in children. In summary, current data support that management guidelines for paediatric cough should be different to those in adults as the aetiological factors and treatment in children significantly differ to those in adults.

Bronchial responsiveness and serum eosinophil cationic protein levels in preschool children with recurrent wheezing

BACKGROUND

Bronchial hyperresponsiveness is a universally recognized phenomenon of asthma, and increased levels of eosinophil cationic protein (ECP) have been identified in the serum of patients with asthma.

OBJECTIVES

To investigate whether enhanced bronchial responsiveness and elevated serum ECP levels are associated with recurrent wheezing in preschool children and to examine the possible relationship between these 2 variables.

METHODS

We recruited 130 children aged 4 to 6 years: 59 with at least 3 episodes of wheezing in the previous year (current wheezers), 38 with a documented history of wheezing before 3 years of age but no subsequent wheezing episodes (past wheezers), and 33 who had never experienced wheezing (nonwheezers). The children underwent methacholine bronchial provocation tests using a modified auscultation method and blood sampling for the measurement of ECP levels.

RESULTS

Current wheezers showed greater bronchial responsiveness than past wheezers and nonwheezers, as demonstrated by lower provocation concentrations that caused audible wheeze and lower provocation concentrations that caused a decline in oxygen saturation of at least 5% from baseline. Likewise, current wheezers had higher serum ECP levels than the other 2 groups. Among current wheezers, ECP levels showed a significant negative correlation with provocation concentrations that caused oxygen desaturation and a marginally significant correlation with provocation concentrations that caused audible wheeze.

CONCLUSIONS

Enhanced bronchial responsiveness and elevated serum ECP levels are associated with recurrent wheezing in 4- to 6-year-old children. These results suggest that wheezing during preschool years may be phenotypically similar to wheezing in older children.

[Chronic cough in childhood]

INTRODUCTION

Although less frequent than viral induced recurrent cough; chronic cough remains a sometimes difficult to resolve diagnostic tool.

STATE OF THE ART

Most authors estimate that a cough can by considered as chronic after three weeks of duration. Few papers have been published concerning etiologic diagnosis of chronic cough in childhood but these indicate the same main causes as in adults: cough variant asthma, postnasal drip syndrome, gastro-esophageal reflux. Nevertheless, each age bracket presents specific diagnosis: malformations between zero and one year, psychogenic cough in adolescents.

PERSPECTIVES

New techniques as induced sputum studies helps to refine chronic cough diagnosis in childhood (after 7 years). Eosinophilic bronchitis, associated or not to bronchial hyperresponsiveness has important therapeutic consequences because associated with a favourable response to corticosteroids. Other techniques will be developed in the future (exhaled NO for example).

CONCLUSIONS

Chronic cough in childhood must be investigated from an anatomic point of view and on frequency arguments. Control and removal of the cough will only be obtained if a precise diagnosis and a suitable treatment are reached.

Respiratory syncytial virus bronchiolitis and the pathogenesis of childhood asthma

There is now convincing evidence that children who develop lower respiratory symptoms during infection with respiratory syncytial virus (RSV) in early life are at increased risk of developing asthma-like symptoms during the school years. What determines this association is not well-understood, but increased likelihood of allergic sensitization plays a minor role, if any, as a determinant of post-RSV wheeze. Current evidence suggests that both genetic and environmental factors determine the type of immune response to the acute RSV infection and that this response, in turn, may affect the development of the control mechanisms involved in the regulation of airway tone. Many different cytokines appear to play a role in this acute immune response, including interferon-gamma; interleukins 8, 10 and 12; and cytokines produced by T helper (Th) 1 and Th2 cells. Because asthma is a heterogeneous condition, future studies will need to determine the potentially different role of RSV infection as a risk factor for these different asthma phenotypes. It is likely, however, that strategies for the prevention of RSV infection may play a role in the prevention of the subsequent development of persistent wheezing and asthma-like symptoms in childhood.

Methods for "indirect" challenge tests including exercise, eucapnic voluntary hyperpnea, and hypertonic aerosols

Bronchial provocation tests that use stimuli that act indirectly to cause airway narrowing have a high specificity for identifying people with active asthma who have the potential to respond to treatment with antiinflammatory drugs. The first test to be developed was exercise and it was used to assess the efficacy of drugs such as sodium cromoglycate. Eucapnic voluntary hyperpnea was developed later, as a surrogate test for exercise. Hypertonic aerosols were introduced to mimic the dehydrating effects of evaporative water loss that occurs during hyperpnea. A wet aerosol of 4.5% saline or a dry powder formulation of mannitol is used. At present the indirect challenge tests are becoming increasingly recognised as appropriate for monitoring treatment with inhaled steroids. Indirect tests identify those with potential for exercise-induced bronchoconstriction, an important problem for some occupations, such as the defence forces, fire fighters and the police force and for some athletic activities. The advantage in using an indirect challenges, over a direct challenge with a single pharmacological agonist, is that a positive response indicates that inflammatory cells and their mediators (prostaglandins, leukotrienes and histamine) are present in the airways in sufficient numbers and concentration to indicate that asthma is active at the time of testing. The corollary to this is that a negative test in a known asthmatic indicates good control or mild disease. Another advantage is that healthy subjects do not have significant airway narrowing to indirect challenge tests. The protocols used for challenge with indirectly acting stimuli are presented in detail.

Age-dependent relationship between bronchial hyperresponsiveness to methacholine and total serum IgE level in asthmatic children

BACKGROUND

A relationship between nonspecific bronchial hyperresponsiveness and allergic airway inflammation has been reported in children and in adults with asthma, but the relationship in infants with asthma is still unclear.

OBJECTIVE

To evaluate the relationship between bronchial hyperresponsiveness and total serum IgE level throughout childhood. Bronchial reactivity to methacholine from the age of 1 to 16 years was studied by methacholine inhalation challenge using transcutaneous oxygen pressure (tcPO2) monitoring.

METHODS

Two hundred one asthmatic children (boys:girls = 132:69; 7.3+/-4.0 years of age, mean +/- SD) were enrolled in this study. The tcPO2 was measured using a tcPO2 monitor. Serial doses of methacholine were doubled until a 10% decrease in tcPO2 from the baseline was reached. The cumulative dose of methacholine at the inflection point of tcPO2 was considered to represent the bronchial reactivity to methacholine.

RESULTS

There was no relationship between the cumulative dose of methacholine at the inflection point of tcPO2 and total serum IgE level in the group of children aged 1 to 4 years (P = 0.212), but significant correlations were found in the groups aged 5 to 10 years and 11 to 16 years (P = 0.044 and P = 0.014, respectively).

CONCLUSIONS

We conclude that there is an age-dependent relationship between bronchial reactivity to methacholine and the total serum IgE level and that inhaled allergens, which were more common allergens in older children, may have some effects on the degree of bronchial reactivity to methacholine in children with asthma.

Inhaled steroids compared with disodium cromoglycate in preschool children with episodic viral wheeze

In school children with atopic asthma the beneficial effects of disodium cromoglycate (DSCG) and beclomethasone dipropionate (BDP) are well-established. In preschool children, wheezing is quite common, and in the majority of cases the symptoms are episodic and reported to be associated with viral infections rather than atopy. We compared the efficacy of regular treatment with DSCG and BDP for prevention of wheezing in preschool children. We were interested to establish whether regular treatment with inhaled anti-inflammatory drugs could lead to a decrease in bronchial responsiveness. In 15 patients (median age, 56 months; range, 43-66 months) bronchial responsiveness was assessed by measuring specific airway resistance (sRaw) during a histamine provocation test. The concentration of histamine eliciting a 100% increase in sRaw (PC100his) was determined. In a double-blind crossover study, patients inhaled either DSCG 10 mg three times a day or BDP 100 microg three times a day for 2 months. After a wash-out period, treatment was changed to BDP or DSCG, respectively. Daily peak flow measurements were carried out, and exacerbations were noted. PC100his was measured at the start and end of each treatment period. No significant decrease in bronchial responsiveness was seen (PC100his DSCG: before 1.3, after 1.66 mg/ml, Pvalue not significant; BDP: before 1.1 after 1.22 mg/ml, Pvalue not significant). Significantly higher morning peak flows were observed on BDP therapy (160 on BDP vs. 150 L/min on DSCG, P < 0.03). BDP treatment resulted in significantly fewer wheezing exacerbations (7 vs. 16, P < 0.005) compared with DSCG therapy. We conclude that in preschool children with episodic virally induced wheezing, BDP therapy was superior to DSCG aerosol treatments for the prevention of exacerbations of wheezing, although no significant effect on bronchial responsiveness was noted during either treatment protocol.

Peak flow variability, methacholine responsiveness and atopy as markers for detecting different wheezing phenotypes in childhood

BACKGROUND

There is increasing evidence that wheezing during childhood may be a heterogeneous condition, and that different forms of wheezing may be associated with different risk factors and prognosis. The aim of this study was to determine if measures of airway lability and of atopy could identify distinct wheezing phenotypes during childhood.

METHOD

In a cohort of children followed from birth peak flow variability (n = 600) was evaluated and methacholine challenge responsiveness (n = 397) was measured at age 11 in relation to wheezing before the age of three, and at age six and 11 years total serum IgE and skin test reactivity to allergens were determined.

RESULTS

Neither positive peak flow variability nor methacholine hyperresponsiveness measured at age 11 were associated with wheezing occurring only during the first three years of life. Both methacholine hyperresponsiveness and positive peak flow variability were associated with wheezing at both ages six and 11 (OR 5.1 (95% CI 2.4 to 10.6) and 2.3 (1.2 to 4.5), respectively). In addition, positive peak flow variability was associated with wheezing up to the age of six but not at age 11 in non-atopic children (OR 2.9 (95% CI 1.0 to 8.8)). Methacholine hyperresponsiveness measured at age 11 was more frequently observed in boys (OR 2.1 (95% CI 1.2 to 3.5)) and was strongly associated with serum IgE levels measured at ages six and 11 (p < 0.001) and with positive skin test reactivity (OR 4.5 (95% CI 2.0 to 10.1)). Peak flow variability was unrelated to sex or markers of atopy (IgE and skin test reactivity).

CONCLUSIONS

Methacholine responsiveness and peak flow variability assessed at age 11, together with markers of atopy (IgE and skin test reactivity to allergens) identify three different wheezing phenotypes in childhood: "transient early wheezing" limited to the first three years of life and unrelated to increased airway lability; "non-atopic wheezing" of the toddler and early school years associated with positive peak flow variability but not with methacholine hyperresponsiveness; and "IgE-associated wheeze/asthma" associated with persistent wheezing at any age and with methacholine hyperresponsiveness, peak flow variability, and markers of atopy.

Interpretation of epidemiological surveys of asthma

Two particular issues make the interpretation of epidemiological studies in asthma problematic. The first is the lack of any clear definition of asthma. This is a perennial area of controversy. Thirty-eight years ago a Ciba Foundation guest symposium addressed this issue and suggested a solution. However, as J. G. Scadding, one of the participants of that symposium, pointed out after further consideration of the problem, what they had proposed was a description, not a definition. Since then, further attempts have been made but with little progress. They remain descriptive rather than definitive and have become, if anything, vaguer. The second problem has been the widespread failure to be precise about hypotheses or to define more precisely the hypothetical influences on asthma. Examples of this are the notions of 'inflammation' and 'atopy'. Standardization of methods for epidemiological studies of asthma is likely to provide a more rigorous framework for the comparison of results and the testing of hypotheses. Nevertheless, the development of such protocols should itself be seen as a hermeneutic device rather than an assertion of established knowledge.