Relationship between bronchial responsiveness and clinical evolution in infants who wheeze: a four-year prospective study

The link between early childhood lower airway symptoms, airway hyperresponsiveness, and school-age lung function

BACKGROUND

The role of early airway hyperresponsiveness (AHR) in the lung function of school-age children is currently unclear.

OBJECTIVE

To conduct a prospective follow-up study of lung function in schoolchildren with a history of lower airway symptoms and AHR to methacholine in early childhood and to compare the findings to schoolchildren with no previous or current lung diseases. We also explored symptoms and markers of type 2 inflammation.

METHODS

In 2004 to 2011, data on atopic markers, lung function, and AHR to methacholine were obtained from 193 symptomatic children under 3 years old. In 2016 to 2018, a follow-up sample of 84 children (median age, 11 years; IQR, 11-12) underwent measurements of atopic parameters, lung function, and AHR to methacholine. Moreover, in 2017 to 2018, 40 controls (median age, 11 years; IQR, 9-12) participated in the study.

RESULTS

Schoolchildren with early childhood lower airway symptoms and increased AHR had more frequent blood eosinophilia than their peers without increased AHR and lower prebronchodilator forced expiratory volume in 1 second (FEV1) and FEV1/forced vital capacity Z-scores than those without increased AHR and controls. Post-bronchodilator values were not significantly different between the two AHR groups. Atopy in early childhood (defined as atopic eczema and at least 1 positive skin prick test result) was associated with subsequent lung function and atopic markers, but not AHR.

CONCLUSION

In symptomatic young children, increased AHR was associated with subsequent obstructive lung function, which appeared reversible by bronchodilation, and blood eosinophilia, indicative of type 2 inflammation.

Severe bronchial hyperresponsiveness along with house dust mite allergy indicates persistence of asthma in young children

BACKGROUND

Significant risk factors for persistence of asthma later in life are family history of allergies, early allergic sensitization and bronchial hyperresponsiveness (BHR). The evolution of BHR in young children without allergic sensitization and with house dust mite allergy (HDM) was investigated.

METHODS

In this retrospective analysis, electronic charts of 4850 young children with asthma and wheezy bronchitis between 2005 and 2018 were reviewed in order to study all patients ≤6 years with BHR assessed by methacholine provocation tests (MCT) at least once (n = 1175). Patients with more than two follow-up measurements were divided in group 1 (no allergic sensitization; n = 110) and group 2 (HDM allergy; n = 88). Additionally, skin prick test, exhaled nitrite oxide (eNO), and asthma treatment were analyzed.

RESULTS

Forty-seven patients of group 1 aged median 4.3 years and 48 patients of group 2 aged median 4.7 years showed initially severe BHR <0.1 mg. At follow-up, patients with HDM were more likely to show persistence of severe BHR than non-sensitized patients (severe BHR group 1: n = 5 (10.6%) vs. group 2: n = 21 (43.8%), p < .001). In addition, 89.4% of group 1 had mild to moderate or no BHR, compared to only 56.2% of group 2. There was a significant difference in eN0 (median group 1: 9 ppb vs. group 2: 26 ppb, p < .001), at last follow-up. Age, sex, and asthma therapy had no effect on BHR.

CONCLUSION

In young children without sensitization BHR normalizes, whereas HDM allergy indicates a persistence of asthma beyond infancy.

Predictive value of childhood airway hyper-responsiveness to indirect stimuli: 10-year longitudinal study

BACKGROUND

Airway hyper-responsiveness (AHR) is a common feature in asthma. The use of AHR in predicting active asthma or the persistence of AHR in childhood is poorly understood. By analyzing longitudinal connections including different measures of AHR, lung function, and inflammation markers, we sought to identify the best available method for predicting persistence of AHR and identification of later active asthma.

METHODS

We tested 105 asthmatic children aged 3-7 years with fractional exhaled nitric oxide (FeNO), impulse oscillometry (IOS), and AHR evaluated by indirect methods (hypertonic saline and exercise challenge). Ten years later, 64 children participated in the follow-up visit and were tested with FeNO, IOS, spirometry, and methacholine challenge. At both study visits, blood samples were collected, and a questionnaire was completed.

RESULTS

Asthma was in remission in 66% of patients at adolescence. AHR measured by hypertonic saline challenge at preschool age was associated with asthma symptoms (OR 10.2; 95% CI 2.8, 37.3) but not with AHR estimated with methacholine challenge 10 years later. AHR measured by exercise challenge was not associated with AHR or recent asthma symptoms in adolescence. Preschool eosinophilia continued until adolescence in 87% of patients but was not associated with AHR or subjective signs of asthma 10 years later. Wheezy preschoolers with atopy had a higher risk for AHR in adolescence (OR 4.1; 95% CI 1.0, 16.2).

CONCLUSION

Results from hypertonic saline challenge are associated with persistent asthma symptoms even after a decade. AHR measured by indirect methods at preschool age did not predict AHR in adolescence.

Airway hyperresponsiveness in young children with respiratory symptoms: A five-year follow-up

BACKGROUND

Recurrent wheezing in early life is transient in most children. The significance of airway hyperresponsiveness (AHR) in persistence of respiratory symptoms from infancy to early childhood is controversial.

OBJECTIVE

We evaluated whether AHR in wheezy infants predicts doctor-diagnosed asthma (DDA) or AHR at the age of 6 years.

METHODS

Sixty-one wheezy infants (age 6-24 months) were followed up to the median age of 6 years. Lung function and AHR with methacholine challenge test were assessed at infancy and 6 years. The exercise challenge test was performed at the age of 6 years. Atopy was assessed with skin prick tests.

RESULTS

At 6 years, 21 (34%) of the children had DDA. Children with DDA had higher logarithmic transformed dose-response slope (LOGDRS) to methacholine in infancy than children without DDA (0.047 vs 0.025; P = .033). Furthermore, AHR to methacholine in infancy and at 6 years were associated with each other (r = 0.324, P = .011). Children with exercise-induced bronchoconstriction (EIB) at 6 years were more reactive to methacholine in infancy than those without EIB (P = .019).

CONCLUSION

Increased AHR in symptomatic infants was associated with increased AHR, DDA, and EIB at median the age of 6 years, suggesting early establishment of AHR.

Factors predicting persistence of early wheezing through childhood and adolescence: a systematic review of the literature

Background

For the early identification of persistent asthma symptoms among young children with recurrent wheezing, it would be helpful to identify all available studies that have identified at least one factor for predicting the persistence of early wheezing. The objective of the present study was to perform a systematic review of all studies that have identified factors that predict the persistence of symptoms among young patients with recurring wheezing.

Methods

A systematic review of relevant studies was conducted through searching in MEDLINE, EMBASE, CINHAL, and SCOPUS databases up to June 2016. Studies that identified predictors of persistence of wheezing illness among young children with recurrent wheezing were retrieved. Two independent reviewers screened the literature and extracted relevant data.

Results

The literature search returned 649 references, 619 of which were excluded due to their irrelevance. Five additional studies were identified from reference lists, and 35 studies were finally included in the review. Among all the identified predictors, the most frequently identified ones were the following: family asthma or atopy; personal history of atopic diseases; allergic sensitization early in life; and frequency, clinical pattern, or severity of wheezing/symptoms.

Conclusion

Parental asthma (especially maternal), parental allergy, eczema, allergic rhinitis, persistent wheezing, wheeze without colds, exercise-induced wheeze, severe wheezing episodes, allergic sensitization (especially polysensitization), eosinophils (blood or eosinophil cationic protein in nasal sample), and fraction of exhaled nitric oxide were risk factors predicting persistence of early wheezing through school age. All of them are included in conventional algorithms, for example, Asthma Predictive Index and its modifications, for predicting future asthma.

Predicting the long-term course of asthma in wheezing infants is still a challenge

Background. In recurrent wheezing infants, it is important to identify those likely to remain asthmatic in order to propose appropriate long-term management. Objective. To establish predictive factors for persistent asthma at adolescence in a population of recurrent wheezing infants. Methods. Retrospective study of 227 infants. Inclusion criteria were age under 36 months, a history of at least three wheezing episodes assessed via a doctor-led ISAAC questionnaire and a standardized allergy testing programme. At 13 years, active asthma was assessed by questionnaire. Results. Risk factors for asthma persisting into adolescence were allergic sensitization to multiple airborne allergens (OR 4.6, CI-95% (1.9–11.2) P = 0.001), initial atopic dermatitis (OR 3.4, CI-95% (1.9–6.3) P < 0.001), severe recurrent wheezing (OR 2.3, CI-95% (1.3–4.2) P = 0.007), and hypereosinophilia ≥470/mm³ (OR 2.2, CI-95% (1.07–4.7) P = 0.033). Conclusion. While it is still difficult to predict the long-term course of asthma, atopy remains the major risk factor for persistent asthma.

Methacholine-induced lung function changes measured with infant body plethysmography

Several techniques have been applied to measure airway responsiveness (AR) in infants, but there are limited data on lung function changes measured by body plethysmography during induced bronchoconstriction. The aim of this study was to compare changes in maximum forced expiratory flow measured at functional residual capacity (V'(maxFRC)) by rapid thoracoabdominal compression (RTC) technique with plethysmographic measurements of specific airway conductance (sG(aw) ), and to investigate whether changes in functional residual capacity (FRC) occur during methacholine-induced bronchoconstriction in infants. We examined 94 infants with recurrent airway symptoms using methacholine airway challenge test including RTC and plethysmographic measurements. A significant association between changes in V'(maxFRC) and sG(aw) (r = 0.30; P = 0.004) was observed, but after adjustments with baseline variability the changes in V'(maxFRC) were greater and showed a closer association with changes in oxygen saturation. At the point of maximal airway obstruction, there was a poor agreement between V'(maxFRC) and sG(aw) to indicate a significant methacholine-induced bronchoconstriction. Airway challenge was also associated with a significant increase in FRC (P < 0.001), with decreasing V'(maxFRC). We conclude that in infants undergoing airway challenge with methacholine, plethysmographic measurements of sG(aw) correlate with the changes in V(maxFRC), but the agreement is poor and the methods cannot be used interchangeably. V(maxFRC) is also more sensitive to detect airway obstruction than sG(aw). However, methacholine-induced bronchoconstriction was associated with significant increases in FRC, which may affect the validity of V(maxFRC) measurements during the test.

Early wheeze as reported by mothers and lung function in 4-year-olds. Prospective cohort study in Krakow

SUMMARY

The purpose of the study was to check the hypothesis that early wheezing as reported by mothers would be associated with reduced lung function in 4-year olds. Study participants were recruited prenatally, as part of a prospective cohort study on the respiratory health of young children exposed to various ambient air pollutants. After delivery, infants were followed over 4 years and the interviewers visited participants at their home to record respiratory symptoms every 3 months in the child's first 2 years of life and every 6 months in the 3rd and 4th years. In the 4th year of follow-up, children were invited for standard lung function testing by spirometry quantified by forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV(1)), and forced expiratory volume in 0.5 sec (FEV(0.5)) levels. Out of 258 children attending spirometry testing 139 performed at least two acceptable exhalation efforts. Cohort children with acceptable spirometric measurements did not differ with respect to wheezing experience and exposure characteristics from those without. The study shows that episodic wheeze was reported in 28.1% of 4-year olds, 6.5% had transient wheeze, and 4.3% had recurrent wheeze. There was an increased frequency of wheezing symptoms and their duration in transient and recurrent wheezers. Adjusted multivariable regression models for gender and height showed that children who reported more than two episodes of wheezing at any point over the follow-up had FVC values lower by 120.5 ml (P = 0.016) and FEV(1) values lower by 98.3 ml (P = 0.034) compared to those who did not report any wheezing; children experiencing more than 10 wheezing days by age 4 showed FVC deficit of 87.4 ml (P = 0.034) and FEV(1) values of 65.7 ml (P = 0.066). The ratios of FEV(1)/FVC%, and FEV(0.5)/FVC% were neither associated with wheezing episodes nor wheezing days. In recurrent wheezers, lung function decrement amounted to 207 ml of FVC, 175 ml of FEV(1), and 104 ml of FEV(0.5). In conclusion, our findings show that wheezing experience during early postnatal life may be associated with lung function deficit of restrictive character in preschool children and detailed history of wheeze in early postnatal life, even though not physician-confirmed, may help define the high risk group of children for poor lung function testing.

[Involvement of distal airways in asthma: lessons from pediatric cohorts]

INTRODUCTION

Prospective studies of paediatric cohorts contribute to our knowledge of changes in pulmonary function in children with asthma.

STATE OF THE ART

Asthma is associated with a significant impairment of the distal airways which is more pronounced when asthma has started early, before 5 years of age, or when asthma is persistent. In utero exposure to tobacco smoke allergenic sensitization and persistent bronchial hyperresponsiveness are the main factors associated with an unfavourable respiratory function outcome. This impairment may persist despite the disappearance of symptoms. Distal airway alterations are also poorly responsive to conventional inhaled corticosteroid therapy. This could be due to early remodelling phenomenon or non-optimal deposition of the drugs on distal airways.

PERSPECTIVES AND CONCLUSIONS

The medium and long term clinical implications of distal airway involvement in paediatric asthma and the impact of treatment need to be evaluated.

[Recurrent wheezing in three year-olds: facts and opportunities]

The 3 year-old group of children has an increased incidence and prevalence of recurrent wheezing episodes. There are different subgroups, who give different inflammatory responses to different triggering agents, and subgroups that differ in aetiopathology and immunopathology. Current diagnostic methods (exhaled nitric oxide in multiple breaths, nitric oxide in exhaled air condensate, induced sputum, broncho-alveolar lavage and endo-bronchial biopsy), enable the inflammatory pattern to be identified and to give the most effective and safe treatment. The various therapeutic options for treatment are reviewed, such as inhaled glucocorticoids when the inflammatory phenotype is eosinophilic, and leukotriene receptor antagonists, when the inflammatory phenotype is predominantly neutrophilic. In accordance with the current recommendations, for the diagnosis as well as for the therapy initiated in children of this age, they must be regularly reviewed, so that if the benefit is not clear, the treatment must be stopped and an alternative diagnosis and treatment considered. The start of treatment should be determined depending on the intensity and frequency of the symptoms, with the aim of decreasing morbidity and increasing the quality of life of the patient.

Childhood asthma and increased airway responsiveness: a relationship that begins in infancy

RATIONALE

Asthma is associated with increased airway responsiveness (AR), but the age when this relationship becomes established is not clear. The present study tested the hypothesis that the association between increased AR and asthma is established after 1 month of age.

OBJECTIVES

To relate AR in infancy to asthma in childhood.

METHODS

As part of a birth cohort study, AR was determined at 1 (early infancy), 6 (mid-infancy), and 12 months of age (late infancy). At 11 years of age (childhood), AR and the presence of asthma symptoms were determined.

MEASUREMENTS AND MAIN RESULTS

Of the 253 study subjects enrolled, AR was determined in 202 in early infancy, 174 in mid-infancy, 147 in late infancy, and 176 in childhood. Increased AR in late infancy, but not in early or mid-infancy, was associated with increased wheeze at 11 years of age (P = 0.016). Increased AR in infancy persisted into childhood in association with male gender, early respiratory illness, and maternal smoking and asthma. Among the 116 subjects assessed in late infancy and childhood, recent wheeze was present in 35% of children with increased AR at both ages, 13% with increased AR in childhood only, 12% for those with increased AR in late infancy only, and 0% for those who did not have increased AR at either age (P = 0.023); the proportions of children with diagnosed asthma in the corresponding groups were 27, 20, 12, and 0% (P = 0.038).

CONCLUSIONS

The association between increased infantile AR and childhood asthma emerges at the end of the first year of life.

New visions in specific immunotherapy in children: an iPAC summary and future trends

Specific immunotherapy is indicated for confirmed immunoglobulin E-mediated airway diseases using standardized allergen products with documented clinical efficacy and safety. For decades the subcutaneous route of administration (SCIT) has been the gold standard. Recently, the sublingual immunotherapy (SLIT) has also been investigated in children. SCIT, especially with grass and birch pollens but also house dust mites, is an effective treatment in children with allergic rhinitis and asthma when a significant part of their symptoms are caused by these allergens. A long-term effect up to 12 yr after discontinuation of SCIT with timothy allergen has been shown. Efficacy and safety of SLIT in pollen allergic rhinoconjunctivitis have been demonstrated in adults. The evidence in children is a little less convincing, and more data is needed. The clinical relevance, long-term results and the size of the effect, as well as the dose, the treatment regimen and duration has not been sufficiently elaborated. It is demonstrated that SCIT has the potential for preventing the development of asthma in children with allergic rhinoconjunctivitis. Also one randomized study indicates a preventive effect of SLIT in children on the development of asthma. At present, there are no studies who clearly demonstrates either a long-term effect or a preventive effect on the development of asthma of SLIT in children. The areas with lack of evidence should be addressed in well performed prospective, randomized long-term studies both with SCIT and SLIT. This review was initiated by iPAC (international Pediatric Allergy and Asthma Consortium) and aims to review current knowledge related to specific immunotherapy in childhood, and to identify needs for future research in this field.

Clinical assessment of asthma progression in children and adults

Asthma is a heterogeneous disorder with a variable course, characterized by episodes of cough, wheezing and shortness of breath, reversible airflow limitation, and bronchial hyperresponsiveness. It begins early in life in many subjects with intermittent symptoms occurring with viral respiratory tract infections. Over time, and in genetically susceptible children (those with an atopic predisposition), the disease becomes more persistent with symptoms occurring in the absence of respiratory tract infections. Children with persistent wheezing are eventually diagnosed with asthma, with those at greatest risk having developed allergic sensitization early in life. Among children with asthma, some will have lifelong asthma with active symptoms and progressive loss of lung function over time, whereas other children will undergo asthma remission in adolescence. Once in remission, the disease may remain quiescent, or it may relapse in midadult life. This review focuses on studies that have enhanced our understanding of the progression of asthma from infancy to adulthood. Studies evaluating progressive loss of lung function, the best-studied measure of asthma progression, are also reviewed, followed by a brief discussion of whether asthma progression can be modified by inhaled glucocorticoid therapy.

[Respiratory function assessment in cooperative patients. Part II]

Analysis of bronchial hyperresponsiveness using bronchial provocation tests are a key feature in the diagnosis of asthma, as well as a valid tool for monitoring disease severity, clinical course, and treatment response. We review non-specific bronchial challenge tests, including pharmacological stimuli (methacholine, adenosine) and physical stimuli (exercise, hypertonic saline, cold air hyperventilation). Although there is some correlation among responses to the distinct tests, individual responses are also observed. The indication for a single test will depend on whether the procedure will be used for diagnostic or epidemiologic purposes, and on experience of its use. Frequently, complementary information will be obtained. Indirect airway challenges tests such as physical stimuli and adenosine are more specific for asthma diagnosis.

Relationship between bronchial hyperresponsiveness and impaired lung function after infantile asthma

Wheezing during infancy has been linked to early loss of pulmonary function. We prospectively investigated the relation between bronchial hyperresponsiveness (BHR) and progressive impairment of pulmonary function in a cohort of asthmatic infants followed until age 9 years. We studied 129 infants who had had at least three episodes of wheezing. Physical examinations, baseline lung function tests and methacholine challenge tests were scheduled at ages 16 months and 5, 7 and 9 years. Eighty-three children completed follow-up. Twenty-four (29%) infants had wheezing that persisted at 9 years of age. Clinical outcome at age 9 years was significantly predicted by symptoms at 5 years of age and by parental atopy. Specific airway resistance (sRaw) was altered in persistent wheezers as early as 5 years of age, and did not change thereafter. Ninety-five per cent of the children still responded to methacholine at the end of follow-up. The degree of BHR at 9 years was significantly related to current clinical status, baseline lung function, and parental atopy. BHR at 16 months and 5 years of age did not predict persistent wheezing between 5 and 9 years of age, or the final degree of BHR, but it did predict altered lung function. Wheezing that persists from infancy to 9 years of age is associated with BHR and to impaired lung function. BHR itself is predictive of impaired lung function in children, strongly pointing to early airway remodeling in infantile asthma.

Chest computed tomography findings in bronchopulmonary dysplasia and correlation with lung function

OBJECTIVE

With changes in the predominant pathogenic factors in the new form of bronchopulmonary dysplasia (BPD), a different pattern of CT findings may be expected. This study aimed to (1) describe CT findings in infants with BPD and (2) correlate the CT findings with lung function abnormalities.

STUDY DESIGN AND METHOD

Retrospective review of 41 very low birthweight infants with BPD, who were referred for pulmonary investigations at between 10 and 20 months after birth because of persistent respiratory symptoms, and underwent CT and lung function tests.

RESULTS

None of the infants had normal CT findings. The most frequent abnormalities were hyperlucent areas (n = 36; 88%), linear opacities (n = 39; 95%), and triangular subpleural opacities (n = 26; 63%). Bronchiectasis was not seen. None of the CT abnormalities correlated with the maximum expiratory flow at functional residual capacity (VmaxFRC). In contrast, increased number of subpleural opacities and limited linear opacities were associated with low FRC and longer duration of neonatal oxygen exposure. The numbers of triangular subpleural opacities also correlated with duration of mechanical ventilation.

CONCLUSIONS

Despite advances in neonatal care, many CT findings in infants with BPD are similar to those observed in the pre-surfactant era, and are still associated with duration of supplemental oxygen and mechanical ventilation. The absence of bronchial involvement in the present study was the most striking difference from previous studies.

[Bronchial hyperresponsiveness to methacholine assessed by means of tracheal auscultation of healthy children aged under 4 years]

OBJECTIVE

To assess the safety of the tracheal auscultation method for measuring bronchial hyperresponsiveness in healthy unsedated children aged less than 4 years and to establish a range of normal bronchial hyperresponsiveness values.

POPULATION AND METHODS

The study population consisted of healthy children aged between 6 months and 4 years. A methacholine bronchial provocation test was administered to unsedated children, using the tidal volume breathing technique and applying an abbreviated protocol. The test was considered positive when wheezing was heard in the trachea, arterial oxygen saturation (SaO2) fell by 5% or more, or respiratory rate increased by 50% or more.

RESULTS

A total of 16 children were studied. Ages ranged from 8 to 47 months, with a mean (SD) of 23.5 (12.2) months. There was no response to the methacholine in 11 children. In the other 5 children, there was a positive response at a concentration of 8 mg/mL. Response to the test was considered positive on the basis of tracheal wheezing in 3 cases, tracheal wheezing and a fall in SaO2 in 1 case, and a fall of SaO2 of 5% or more in 1 case. SaO2 never fell below 93%.

CONCLUSIONS

As a means for assessing bronchial hyperresponsiveness, the tracheal auscultation method is appropriate, is simple to apply, and can be safely administered to unsedated children aged less than 4 years. The lowest concentration at which a response to methacholine occurs in healthy children of this age group is 8 mg/mL.

Age differences in cholinergic airway responsiveness in relation with muscarinic receptor subtypes

Children seem more susceptible to increased airway reactivity than adults. Such an age-dependent discrepancy in airway reactivity may involve different airway smooth muscle functions. Therefore, we compared the in vivo and in vitro responsiveness of airway smooth muscles between two age groups of animals. Rats of 6 and 21 weeks old were challenged in vivo with acetylcholine (ACh) infused intravenously and airway resistance (R(aw)) was measured. Tracheal muscle was also isolated and the isometric force developed to ACh or KCl was measured. Furthermore, the level of genes encoding muscarinic receptor subtypes (M(1-3)) and acetylcholinesterase (AChE) expressed in the tracheal muscle was determined by RT-PCR. In results, the basal R(aw) was similar in the two age groups. The R(aw) at each ACh dose was significantly greater in young rats than older rats (p<0.05, n=22-27). Tracheal muscles from young rats were more sensitive to ACh than older rats (p<0.05, n=20-21), while receptor-independent muscle contraction to KCl was greater in older rats (p<0.05, n=10-19). Genes encoding AChE, M(2) and M(3) muscarinic receptors were more highly expressed in the tracheal muscles from young than older rats (p<0.05, n=4-6). In conclusion, airway smooth muscle in young rat is more sensitive to cholinergic stimulation in vivo and in vitro compared to older rats, which may be due to a higher expression of M(2) and M(3) muscarinic receptors in airway smooth muscle.

Sensitivity of bronchial responsiveness measurements in young infants

OBJECTIVES

There is limited evidence on the preferred methods for evaluating lung function in infancy. The objective of this study was to compare sensitivity and repeatability of indexes of lung function in young infants during induced airway obstruction.

METHODS

The study population consisted of 402 infants (median age, 6 weeks). Forced flow-volume measurements were obtained by the raised volume rapid thoracoabdominal compression technique and were compared with indexes of tidal breathing, measurements of transcutaneous oxygen (Ptco(2)), and auscultation during methacholine challenge testing.

RESULTS

Ptco(2) was the most sensitive parameter to detect increasing airway obstruction during methacholine challenge, followed by forced expiratory volume at 0.5 s (FEV(0.5)). Both were superior to other indexes of forced spirometry as well as tidal breathing indexes and auscultation. Coefficients of variations for Ptco(2) and FEV(0.5) were 4% and 7%, respectively.

CONCLUSIONS

Ptco(2) and FEV(0.5) are the most sensitive parameters for measurement of bronchial responsiveness in young infants. Measurements of baseline lung function should preferably be made using FEV(0.5.) Measurements of bronchial responsiveness are best assessed using Ptco(2), which may be performed in nonsedated infants and improve feasibility of future studies on lung function in infancy.

2003 canadian asthma consensus guidelines executive summary

BACKGROUND

Guidelines for the diagnosis and management of asthma have been published over the last 15 years; however, there has been little focus on issues relating to asthma in childhood. Since the last revision of the 1999 Canadian Asthma Consensus Report, important new studies, particularly in children, have highlighted the need to incorporate new information into the asthma guidelines. The objectives of this article are to review the literature on asthma published between January 2000 and June 2003 and to evaluate the influence of new evidence on the recommendations made in the 1999 Canadian Asthma Consensus Report and its 2001 update, with a major focus on pediatric issues.

METHODS

The diagnosis of asthma in young children and prevention strategies, pharmacotherapy, inhalation devices, immunotherapy, and asthma education were selected for review by small expert resource groups. The reviews were discussed in June 2003 at a meeting under the auspices of the Canadian Network For Asthma Care and the Canadian Thoracic Society. Data published through December 2004 were subsequently reviewed by the individual expert resource groups.

RESULTS

This report evaluates early-life prevention strategies and focuses on treatment of asthma in children, emphasizing the importance of early diagnosis and preventive therapy, the benefits of additional therapy, and the essential role of asthma education.

CONCLUSION

We generally support previous recommendations and focus on new issues, particularly those relevant to children and their families. This document is a guide for asthma management based on the best available published data and the opinion of health care professionals, including asthma experts and educators.

Response to bronchodilator in infants with bronchiolitis can be predicted from wheeze characteristics

OBJECTIVE

Lung sounds analysis has been used for clinical care. Our objectives were to characterize the spectral pattern of lung sounds and their relation to bronchodilator effects in acute bronchiolitis (AB). We hypothesized that patients with sinusoidal wheezes (SW) would show a more significant bronchodilator response.

METHODOLOGY

We studied 22 asleep hospitalized infants (14 boys, eight girls), aged 5.2 +/- 1 months, 16 with a positive respiratory syncytial virus test, during their first 3 days after admission. Patients breathed spontaneously through a face mask connected to a pneumotachograph during normal breathing, and only target flows of 0.1 +/- 0.02 L/s were analyzed. Sounds were obtained using two contact sensors attached over both posterior lower lobes. For inspiratory and expiratory sounds, we determined the frequencies below which 25% (F25), 50% (F50), 75% (F75) and 99% (SEF99) of the spectral power between 100 and 1000 Hz was contained. We repeated the measurements 20 min after bronchodilator therapy in all patients.

RESULTS

We found classic SW in 11 patients, while the other 11 had complex wheezes (CW). There were positive bronchodilator responses in 9/11 with SW and 3/11 with CW (P < 0.01). Patients who responded to salbutamol showed an increase in power at low frequencies after medication (P < 0.01), and a positive correlation between wheezing and the increase in the power spectra measured by F50 and SEF99 (P < 0.001).

CONCLUSIONS

We conclude that sinusoidal and complex wheezes occur in patients with AB, that a positive response to bronchodilator is significantly more common in those with classic SW and that lung sounds analysis is a reproducible, safe and non-invasive method for assessing wheeze in infants.

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.

[Bronchial changes in untreated asthma]

Persistent asthma is associated to airway remodeling, characterized by structural changes of the bronchi, poorly responsive to therapies. Remodeling may strongly contribute to the residual airway obstruction observed in asthmatic patients, both children and adults, and to the loss of reversibility of this obstruction. Remodeling has been demonstrated in paediatric asthma and is not limited to longstanding severe asthma. Numerous arguments indicate that this process begins early in the development of asthma. Some studies argue for a possible prevention - or limitation - of this process by an early treatment.

Wheeze Phenotypes and Lung Function in Preschool Children

Distinct phenotypes can be identified in childhood wheezing illness. Within the context of a birth cohort study, we investigated the association between preschool lung function and phenotypes of wheeze. From parentally reported history of wheeze (interviewer-administered questionnaire, age 3 and 5 years), children were classified as never wheezers, transient early wheezers, late-onset wheezers, or persistent wheezers. Lung function (specific airway resistance [sRaw]; kPa/second) was assessed at age 3 (n = 463) and 5 years (n = 690). Persistent wheezers had markedly poorer lung function compared with other groups. In children who had wheezed by age 3, the risk of persistent wheeze increased with increased sRaw (odds ratio [OR] 5.2, 95% confidence interval [CI] 1.3-22.0; p = 0.02). In a multivariate model, increasing sRaw (OR 5.5, 95% CI 1.2-25.9; p = 0.03) and the child's sensitization (OR 2.8, 95% CI 1.3-5.8; p = 0.008) were significant independent predictors of persistent wheezing. We found no association between lung function at age 3 and late-onset wheeze in children who had not wheezed previously (OR 0.6, 95% CI 0.07-5.3; p = 0.64). In conclusion, poor lung function at age 3 predicted the subsequent persistence of symptoms in children who had wheezed within the first 3 years, but was not associated with the onset of wheeze after age 3 in children who had not wheezed previously.

The relationship between infant airway function, childhood airway responsiveness, and asthma

The relationship between reduced pulmonary function in early life and persistent wheeze (PW) in school-aged children remains uncertain. In this study, VmaxFRC was assessed at 1 month of age, and the presence of wheeze up to 11 years of age was prospectively identified. At 11 years of age, airway responsiveness (AR) to inhaled histamine and atopy were assessed. Recent wheeze at 11 years of age was associated with a reduced mean z score for VmaxFRC at 1 month of age (-0.41 [SD 0.91], n = 31) compared with no recent wheeze (0.04 [SD 1.00], n = 153, p = 0.03). Wheeze between 4 and 6 years that persisted at 11 years (PW) was most prevalent among those with reduced VmaxFRC at 1 month and atopy aged 11 years (p = 0.002) or reduced VmaxFRC and increased AR aged 11 years (p = 0.015). When all factors were considered, reduced VmaxFRC at 1 month (p = 0.03) and increased AR aged 11 years (p < 0.001) were independently associated with PW (n = 17) compared with other outcomes (n = 129). Reduced airway function present in early infancy is associated with PW at 11 years of age, and this relationship is independent of the effect of increased AR and atopy in childhood.

Pulmonary function tests in preschool children with asthma

Pulmonary function tests are seldom performed in preschool children with asthma. The aim of this multicenter study was to compare pulmonary function in 74 preschool children with asthma (height of 90-130 cm) and 84 healthy control subjects. Functional residual capacity (helium dilution technique) and expiratory interrupter resistance (interrupter technique) were measured. As compared with control children, children with asthma had a significantly higher resistance (0.77 +/- 0.20 vs. 0.92 +/- 0.22 kPa. L-1. second, p < 0.001) and significantly lower specific expiratory interrupter conductance (p < 0.005) values. Resistance values were significantly higher in children with asthma with than without symptoms on exertion (p < 0.05). The effect of bronchodilator administration, expressed as the percentage of baseline and predicted resistance values, was significantly greater in children with asthma than in control subjects (-18.6 +/- 13.6% vs. -11.2 +/- 15.2%, p </= 0.001, and -23.2 +/- 19.2% vs. -12.6 +/- 17.8%, p < 0.001), respectively. A 35% decrease in resistance after bronchodilation expressed as the percentage of predicted values had a likelihood ratio of 3 for separating the bronchodilator response in children with asthma from that in healthy control subjects. Pulmonary function tests that do not require active cooperation may help in the management and follow-up of preschool children with asthma who are unable to perform forced expiratory maneuvers.

Primary and secondary prevention of allergic airway disease

The incidence of atopic conditions is continuing to rise. The number of primary prevention cohorts is increasing and results are becoming available. There is a lack of true secondary prevention trials, however. This article reviews the results currently available from primary and secondary prevention studies.

Recurrent wheezing in infants and young children and bronchial hyperresponsiveness: a perspective

Epidemiological studies report a 50% incidence of at least one wheezing episode in young children. If we can argue that 10% of children have asthma sometime during their pediatric years, it still leaves a significant percentage of children with an unexplained cause for their wheezing. Other recognized phenotypes of recurrent wheezing include young children exposed to excessive environmental tobacco smoke (ETS), while other infants wheeze recurrently following a significant episode of bronchiolitis. Bronchial hyperresponsiveness (BHR) is a universally recognized phenomenon of asthma, but its presence in young children with recurrent wheezing is not as well studied. Currently available studies demonstrates that BHR is also seen in young pediatric asthmatics, paralleling what is well recognized in adolescent or adult asthma. In those children with post-bronchiolitis wheezing, BHR appears to be present to a degree; while infants and young children exposed to ETS have increased BHR, as a group. If exaggerated BHR in recurrent wheezing children without asthma has the same inherent disadvantage as it does in asthmatic children, additional studies looking directly at this issue in a longitudinal fashion need to be designed. A hypothesis of BHR in non-asthmatic children is presented that could be studied prospectively.

Pulmonary physiology, airway responsiveness and asthma

What we know: Tests that have allowed the measurement of lung function in infants have greatly enhanced our understanding of early pulmonary development and the pathophysiology of early respiratory disease. Airway responsiveness in infancy appears to be an independent determinant of symptoms and lung function later in childhood. New tests of airway responsiveness hold the promise of predicting, with increased specificity, infants at risk of developing asthma. What we need to know: What are the factors that determine airway responsiveness soon after birth? Why does airway responsiveness in the first weeks of life relate to lung function many years later? Do different challenge agents reflect different pathophysiological processes involved in the development of persistent asthma?

Non-invasive monitoring of airway inflammation

What we know: Various techniques are available that purport to measure aspects of airway inflammation non-invasively, including analysis of volatile molecules in exhaled breath and components of breath condensates. Adapting and validating these methods for use in young children and infants poses significant methodological problems, but progress has been made, particularly with regard to measurements of exhaled nitric oxide. Future studies to validate such tests are likely to require access to airway tissue for examination as a "gold standard". What we need to know: How can we obtain airway tissue from infants and young children to better characterise the early airway changes in asthma? How do non-invasive tests of airway inflammation compare with a validated gold standard? How sensitive and specific are non-invasive tests of inflammation for predicting outcomes in asthma, including response to therapy?