Bronchodilator responsiveness in wheezy infants and toddlers is not associated with asthma risk factors

Modeling future asthma attributable to fine particulate matter (PM2.5) in a changing climate: a health impact assessment

Exposure to fine particulate matter (PM_2.5) is associated with asthma development as well as asthma exacerbation in children. PM_2.5 can be directly emitted or can form in the atmosphere from pollutant precursors. PM_2.5 emitted and formed in the atmosphere is influenced by meteorology; future changes in climate may alter the concentration and distribution of PM_2.5. Our aim is to estimate the future burden of climate change and PM_2.5 on new and exacerbated cases of childhood asthma. Projected concentrations of PM_2.5 are based on the Geophysical Fluid Dynamics Laboratory Coupled Model version 3 climate model, the Representative Concentration Pathway 8.5 greenhouse gas scenario, and two air pollution emissions datasets: a 2011 emissions dataset and a 2040 emissions dataset that reflects substantial reductions in emissions of PM_2.5 as compared to the 2011 inventory. We estimate additional PM_2.5-attributable asthma as well as PM_2.5-attributable albuterol inhaler use for four future years (2030, 2050, 2075, and 2095) relative to the year 2000. Exacerbations, regardless of the trigger, are counted as attributable to PM_2.5 if the incident disease is attributable to PM_2.5. We project 38 thousand (95% CI 36, 39 thousand) additional PM_2.5-attributable incident childhood asthma cases and 29 million (95% CI 27, 31 million) additional PM_2.5-attributable albuterol inhaler uses per year in 2030, increasing to 200 thousand (95% CI 190, 210 thousand) additional incident cases and 160 million (95% CI 150, 160 million) inhaler uses per year by 2095 relative to 2000 under the 2011 emissions dataset. These additional PM_2.5-attributable incident asthma cases and albuterol inhaler use would cost billions of additional U.S. dollars per year by the late century. These outcomes could be mitigated by reducing air pollution emissions.

Do helminth infections underpin urban-rural differences in risk factors for allergy-related outcomes?

Background

It is proposed that helminth exposure protects against allergy‐related disease, by mechanisms that include disconnecting risk factors (such as atopy) from effector responses.

Objective

We aimed to assess how helminth exposure influences rural‐urban differences in risk factors for allergy‐related outcomes in tropical low‐ and middle‐income countries.

Methods

In cross‐sectional surveys in Ugandan rural Schistosoma mansoni (Sm)‐endemic islands, and in nearby mainland urban communities with lower helminth exposure, we assessed risk factors for atopy (allergen‐specific skin prick test [SPT] reactivity and IgE [asIgE] sensitization) and clinical allergy‐related outcomes (wheeze, urticaria, rhinitis and visible flexural dermatitis), and effect modification by Sm exposure.

Results

Dermatitis and SPT reactivity were more prevalent among urban participants, urticaria and asIgE sensitization among rural participants. Pairwise associations between clinical outcomes, and between atopy and clinical outcomes, were stronger in the urban survey. In the rural survey, SPT positivity was inversely associated with bathing in lakewater, Schistosoma‐specific IgG4 and Sm infection. In the urban survey, SPT positivity was positively associated with age, non‐Ugandan maternal tribe, being born in a city/town, BCG scar and light Sm infection. Setting (rural vs urban) was an effect modifier for risk factors including Sm‐ and Schistosoma‐specific IgG4. In both surveys, the dominant risk factors for asIgE sensitization were Schistosoma‐specific antibody levels and helminth infections. Handwashing and recent malaria treatment reduced odds of asIgE sensitization among rural but not urban participants. Risk factors for clinical outcomes also differed by setting. Despite suggestive trends, we did not find sufficient evidence to conclude that helminth (Sm) exposure explained rural‐urban differences in risk factors.

Conclusions and clinical relevance

Risk factors for allergy‐related outcomes differ between rural and urban communities in Uganda but helminth exposure is unlikely to be the sole mechanism of the observed effect modification between the two settings. Other environmental exposures may contribute significantly.

Bronchodilator response in wheezing infants assessed by the raised volume rapid thoracic compression technique

BACKGROUND

Bronchodilator response (BDR) analyzed by the raised volume rapid thoracic compression (RVRTC) in wheezing infants is not yet well described, although bronchodilators (BD) are routine in the treatment of this population.

OBJECTIVE

To evaluate BDR by RVRTC technique in infants with recurrent wheezing and compare to control group.

METHOD

Cross sectional study, 45 infants, age 56 weeks (38-67 weeks). Two groups: wheezing group (WG: history of recurrent wheezing) and control group (CG). RVRTC was evaluated, FVC, FEV_0.5, FEF₅₀, FEF₇₅, FEF_85, FEF_25-75 were measured. Salbutamol was delivered to infants and RVRTC evaluated again. BDR was determined by the increase greater than two standard deviation from the mean change in the CG.

RESULTS

In WG (n = 32) lung function was worse than in CG (n = 13): FEV_0.5: 0.0(-0.9-0.9z score) vs 0.8(0.2-1.4z score); FEF₅₀: 0.2(-0.3-1.1z score) vs 0.9(0.5-1.4z score); and FEF_25-75: 0.2(-0.5-1.1z score) vs 1.1(0.6-1.6z score), respectively, p < 0.05. Both groups had similar increase after BD. In WG 11 patients (34%) were responder and these had worse lung function compared to nonresponder (n = 21) (p < 0.05). The increase in lung function after BD in responder was higher than in nonresponder: FEV_0.5: 6.5(2.1-7.1%) vs -0.5(-2.5-0.7%), FEF₅₀: 5.1(2.7-11.7%) vs 0.4(-1.1-2.8%), FEF₇₅: 20.7(4.7-23.6%) vs -1.3(-6.4-3.9%), FEF_25-75: 9.9(3.8-16.4%) vs 0.0(-1.5-1.0%), respectively, p < 0.05.

CONCLUSION

34% WG showed BDR measured by the RVRTC. The best variables to detect BDR were FEF₇₅, FEF_25-75 and FEV_0.5. Patients with worse lung function showed better response to BD.

Pulmonary Morbidity in Infancy after Exposure to Chorioamnionitis in Late Preterm Infants

RATIONALE

Chorioamnionitis is an important cause of preterm birth, but its impact on postnatal outcomes is understudied.

OBJECTIVES

To evaluate whether fetal exposure to inflammation is associated with adverse pulmonary outcomes at 6 to 12 months' chronological age in infants born moderate to late preterm.

METHODS

Infants born between 32 and 36 weeks' gestational age were prospectively recruited (N = 184). Chorioamnionitis was diagnosed by placenta and umbilical cord histology. Select cytokines were measured in samples of cord blood. Validated pulmonary questionnaires were administered (n = 184), and infant pulmonary function testing was performed (n = 69) between 6 and 12 months' chronological age by the raised volume rapid thoracoabdominal compression technique.

MEASUREMENTS AND MAIN RESULTS

A total of 25% of participants had chorioamnionitis. Although infant pulmonary function testing variables were lower in infants born preterm compared with historical normative data for term infants, there were no differences between infants with chorioamnionitis (n = 20) and those without (n = 49). Boys and black infants had lower infant pulmonary function testing measurements than girls and white infants, respectively. Chorioamnionitis exposure was associated independently with wheeze (odds ratio [OR], 2.08) and respiratory-related physician visits (OR, 3.18) in the first year of life. Infants exposed to severe chorioamnionitis had increased levels of cord blood IL-6 and greater pulmonary morbidity at age 6 to 12 months than those exposed to mild chorioamnionitis. Elevated IL-6 was associated with significantly more respiratory problems (OR, 3.23).

CONCLUSIONS

In infants born moderate or late preterm, elevated cord blood IL-6 and exposure to histologically identified chorioamnionitis was associated with respiratory morbidity during infancy without significant changes in infant pulmonary function testing measurements. Black compared with white and boy compared with girl infants had lower infant pulmonary function testing measurements and worse pulmonary outcomes.

Bronchodilator responsiveness in wheezy infants predicts continued early childhood respiratory morbidity

OBJECTIVE

Spirometry including bronchodilator responsiveness is considered routine in the workup of asthma in older children. However, in wheezy infants the existence of bronchodilator responsiveness and its prognostic significance remain unclear.

METHODS

Infants (< 2 years) with chronic or recurrent wheezing or coughing were evaluated by infant pulmonary function testing (PFT). Maximal expiratory flow at the point of functional residual capacity (V̇maxFRC) was measured before and 20 minutes after salbutamol administration. Only infants with an obstructive profile (V̇maxFRC < 80% predicted) were included. The infants were divided into two groups with regard to whether or not a response to salbutamol was observed on PFT. A response was defined as a mean V̇maxFRC after salbutamol administration exceeding the upper confidence interval limit of individual pre-bronchodilator V̇maxFRC measurements. Follow-up data was gathered after a mean of 2 years.

MEASUREMENTS AND MAIN RESULTS

Sixty infants were included in the study of which 32 (53%) demonstrated responsiveness to bronchodilators. The infants in the responsive group had a significantly higher frequency of physician visits for wheezing than the non-responders (3.0 mean visits/yr vs. 1.5 respectively, P = 0.03), and had a higher likelihood of having received asthma medication in the last year of the follow-up period (84% vs. 50% respectively, RR: 1.68[1.10-2.56]). At the end of the follow-up period, more parents in the responsive group reported continued respiratory disease (71% vs. 22%, RR:3.21[1.30-7.95]).

CONCLUSIONS

Bronchodilator responsiveness can be demonstrated by infant PFT in infants with recurrent wheezing and can predict increased respiratory morbidity until 3 years of age.

Utility of bronchodilator response for asthma diagnosis in Latino preschoolers

BACKGROUND

Asthma diagnosis in preschoolers is mostly based on clinical evidence, but a bronchodilator response could be used to help confirm the diagnosis. The objective of this study is to evaluate the utility of bronchodilator response for asthma diagnosis in preschoolers by using spirometry standardised for this specific age group.

METHODS

A standardised spirometry was performed before and after 200 mcg of salbutamol in 64 asthmatics and 32 healthy control preschoolers in a case-control design study.

RESULTS

The mean age of the population was 4.1 years (3-5.9 years) and 60% were females. Almost 95% of asthmatics and controls could perform an acceptable spirometry, but more asthmatics than controls reached forced expiratory volume in one second (FEV₁) (57% vs. 23%, p=0.033), independent of age. Basal flows and FEV₁ were significantly lower in asthmatics than in controls, but no difference was found between groups in forced vital capacity (FVC) and FEV in 0.5s (FEV₀.₅). Using receiver operating characteristic (ROC) curves, the variable with higher power to discriminate asthmatics from healthy controls was a bronchodilator response (% of change from basal above the coefficient of repeatability) of 25% in forced expiratory flow between 25% and 75% (FEF₂₅₋₇₅) with 41% sensitivity, 80% specificity. The higher positive likelihood ratio for asthma equalled three for a bronchodilator response of 11% in FEV₀.₅ (sensitivity 30%, specificity 90%).

CONCLUSIONS

In this sample of Chilean preschoolers, spirometry had a very high performance and bronchodilator response was very specific but had low sensitivity to confirm asthma diagnosis.

Preschool wheeze is not asthma: a clinical dilemma

Recurrent wheezing is common in preschool children and often gets labelled as asthma. It is important to differentiate preschool wheeze from asthma through focused history, examination and exclusion of other serious conditions that may present as wheeze. Two different pragmatic clinical phenotypes viz. episodic viral wheeze (EVW) and multi-trigger wheeze (MTW) have been described although categories do not remain fixed and cross over is often seen in clinical practice. Episodic use of inhaled bronchodilators such as salbutamol when wheezy, is the mainstay of treatment along with non-pharmacological measures such as avoidance of environmental tobacco smoke and parental education. Inhaled corticosteroids are the first choice for maintenance therapy in MTW whereas montelukast may be useful when maintenance therapy is considered in EVW. Any maintenance therapy should be viewed as a trial and need to be discontinued in cases where no benefit has been demonstrated. Short term systemic steroid therapy should be reserved for excaerbation of wheezy symptoms where hospitalization is necessary. Prognosis is good in recurrent mild EVW although remission in atopic MTW is often not achieved and the children in the latter group go on to develop asthma.

How to avoid misinterpreting lung function tests in children: a few practical tips

Assessments of pulmonary function play an integral part in the clinical management of school age children as well as providing objective outcome measures in clinical and epidemiological research studies. Pulmonary function tests (PFTs) can also be undertaken in sleeping infants and in awake young children from 3 years of age. However, the clinical utility of such assessments, which are generally confined to specialist centres, has yet to be established. Whether requesting or undertaking paediatric PFTs, or simply reading about how these tests have been applied in research studies, it is essential to question whether results have been interpreted in a meaningful way. This review summarises some of the issues that need to be considered, including: why the tests are being performed; which tests are most likely to detect the suspected pathophysiology; how often such tests should be repeated; whether results are likely to be reliable (in terms of data quality, repeatability and the availability of suitable reference equations with which to distinguish the effects of disease from those of growth and development), and whether the selected tests are likely to be feasible in the individual child or study group under investigation.

Birth cohorts in asthma and allergic diseases: report of a NIAID/NHLBI/MeDALL joint workshop

Population-based birth cohorts on asthma and allergies increasingly provide new insights into the development and natural history of the diseases. More than 130 birth cohorts focusing on asthma and allergy have been initiated in the last 30 years. A National Institute of Allergy and Infectious Diseases; National Heart, Lung, and Blood Institute; Mechanisms of the Development of Allergy (MeDALL; Framework Programme 7 of the European Commission) joint workshop was held in Bethesda, Maryland, on September 11-12, 2012, with 3 objectives: (1) documenting the knowledge that asthma/allergy birth cohorts have provided, (2) identifying the knowledge gaps and inconsistencies, and (3) developing strategies for moving forward, including potential new study designs and the harmonization of existing asthma birth cohort data. The meeting was organized around the presentations of 5 distinct workgroups: (1) clinical phenotypes, (2) risk factors, (3) immune development of asthma and allergy, (4) pulmonary development, and (5) harmonization of existing birth cohorts. This article presents the workgroup reports and provides Web links (AsthmaBirthCohorts.niaid.nih.gov or www.medall-fp7.eu), where the reader will find tables describing the characteristics of the birth cohorts included in this report, the type of data collected at differing ages, and a selected bibliography provided by the participating birth cohorts.

Infant wheeze: is asthma a possibility?

Most infant wheeze is not asthma. Nonetheless, infants are able to develop reversible airway obstruction with or without allergic sensitisation, and asthma does occur at this age. The many other causes of infant wheeze, however, make asthma more difficult to distinguish from the background 'noise'. Consideration of risk factors and clinical features can enable some infants to be given a provisional diagnosis and, if their symptoms are disabling, a cautious trial of asthma treatment.

Assessment of bronchodilator response in preschool children by pulmonary function tests

We performed pulmonary function test to document bronchodilator response by using tidal breathing flow volume loop (TBFVL), rapid thoracic compression (RTC), and raised volume rapid thoracic compression (RVRTC) techniques. Thirty-nine children (mean age 45.2 months) were evaluated. The parameters that showed significant improvement after bronchodilator administration included TEF10/ PTEF ratio in TBFVL, and FEF25-75%, FEV1 and PEF in RVRTC. None of the parameters measured in RTC showed significant improvement. We conclude FEV1, PEF and FEF 25-75% in RVRTC have greater sensitivity for detection of airways changes.