Baseline and post-bronchodilator interrupter resistance and spirometry in asthmatic children

Bronchodilator response by interrupter technique to guide management of preschool wheeze

OBJECTIVE

We examined relationships between clinical features and pulmonary function before and after inhaled corticosteroid (ICS) treatment in wheezy preschool children, and specifically, whether measuring bronchodilator response (BDR) could predict benefit from ICS.

DESIGN

Clinical non-randomised intervention study SETTING: Secondary care.

PATIENTS

Preschool children (2 years to <6 years) with recurrent wheeze.

INTERVENTIONS

Inhaled beta-agonist, ICS.

OUTCOME MEASURES

We measured prebronchodilator and postbronchodilator interrupter resistance (Rint) and symptom scores at 0 (V1), 4 (V2) and 12 (V3) weeks. At V2, those with a predetermined symptom level commenced ICS. Modified Asthma Predictive Index (mAPI) and parental perception of response to bronchodilator were recorded. Response to ICS was defined as a reduction in daily symptom score of >0.26. Positive BDR was defined as fall in Rint of ≥0.26 kPa.s/L, ≥35% predicted or ≥1.25 Z Scores.

RESULTS

Out of 138 recruited children, 67 completed the full study. Mean (SD) prebronchodilator Rint at V2 was 1.22 (0.35) kPa.s/L, and fell after starting ICS (V3) to 1.09 (0.33) kPa.s/L (p<0.001), while mean (SD) daily symptom score fell from 0.56 (0.36) to 0.28 (0.36) after ICS (p<0.001). Positive Rint BDR before ICS (at V1 and/or V2), using all three threshold criteria, was significantly associated with response to ICS on symptom scores at V3 (p<0.05). mAPI was not significantly associated with response to ICS, and parents' perception of response to bronchodilator was not related to measured Rint BDR .

CONCLUSIONS

Rint BDR may be helpful in selecting which wheezy preschool children are likely to benefit from ICS.

Comparative analysis of pulmonary function in children born preterm and full-term at 6–9 years of age

Abstract Objective: To compare pulmonary function parameters and the prevalence of altered pulmonary function in children born preterm and full-term, using the Global Lung Initiative reference values. Methods: This is a cross-sectional study with 6–9-year-old children submitted to measurement of airway resistance (Rint) and spirometry according to the American Thoracic Society and European Respiratory Society Technical Statement. The inclusion criteria were, among the preterm group: gestational age <37 weeks and birth weight <2000g; among the full-term group: schoolchildren born full-term with birth weight >2500g, recruited at two public schools in São Paulo, Brazil, matched by sex and age with the preterm group. As exclusion criteria, congenital malformations, cognitive deficit, and respiratory problems in the past 15 days were considered. Results: A total of 112 children were included in each group. Preterm children had gestational age of 30.8±2.8 weeks and birth weight of 1349±334g. Among them, 46.6% were boys, 46.4% presented respiratory distress syndrome, 19.6% bronchopulmonary dysplasia, and 65.2% were submitted to mechanical ventilation in the neonatal unit. At study entry, both groups were similar in age and anthropometric parameters. Parameters of pulmonary function (Z scores) in preterm and full-term groups were: Rint (0.13±2.24 vs. -1.02±1.29; p<0.001); forced vital capacity (FVC) (-0.39±1.27 vs. -0.15±1.03; p=0.106), forced expiratory volume in one second (FEV1)/FVC (-0.23±1.22 vs. 0.14±1.11; p=0.003), FEV1 (-0.48±1.29 vs. -0.04±1.08; p=0.071), and forced expiratory flow between 25% and 75% of vital capacity (FEF25-75) (1.16±1.37 vs. 2.08±1.26; p=0.005), respectively. The prevalence values of altered airway resistance (16.1 vs. 1.8%; p<0.001) and spirometry (26.8 vs. 13.4%, p=0.012) were higher in preterm infants than in full-term ones. Conclusions: Preterm children had higher prevalence of altered pulmonary function, higher Z scores of airway resistance, and lower Z scores of FEV1/FVC and FEF25-75 compared with those born full-term.

Impulse oscillometry indices to detect an abnormal lung clearance index in childhood cystic fibrosis

The objective of our cross-sectional study was to assess the relationships between indices of multiple breath washout (MBW) and impulse oscillometry system (IOS) in cystic fibrosis in forty consecutive children (median age 8.1 years) in stable conditions and to evaluate whether cut-off values of IOS indices may help to avoid MBW, which is time-consuming. IOS measurements took a median duration of 3 min, while MBW measurements took a median duration of 49 min. Lung Clearance Index (LCI_2.5% ) depicted significant linear correlations with z-scores of R5Hz, R5-20Hz, X5Hz, AX, and Fres (r²  = 0.27 to 0.51). Receiver-operator characteristic curves were constructed and showed that the best compromise was obtained with the z-score of Fres, with a cut-off value of -1.37 that had a sensitivity of 0.966, a specificity of 0.636, and a negative predictive value of 0.875. This z-score is useful for excluding increased LCI_2.5% when below -1.37 using the reference set of Gochicoa et al. In conclusion, IOS measurement is easily and rapidly obtained in children and may be clinically useful for excluding increased LCI_2.5% , thus allowing the time-consuming MBW test to be avoided.

Usefulness of sRtot and Rint in bronchodilator testing in the diagnosis of asthma in children

Introduction

The usefulness of total specific resistance (sRtot) and interrupter resistance (Rint) as a bronchodilator reversibility test (BT) alternative to forced expiratory volume in 1 s (FEV₁) in asthma diagnosis in children has not been established.

Aim

To compare different applied definitions of airflow obstruction in children measuring response to the bronchodilator by spirometry, plethysmography and the interrupter technique in asthmatic children.

Material and methods

It was a prospective, real-life, non-interventional study. Children, aged 6–18 with newly diagnosed asthma, able to perform lung function tests were included into the study. Subjects underwent a history taking, physical examination, reversibility test in spirometry, plethysmography, and the interrupter technique. A standard cut-off of 12% from the initial value for reversibility in FEV₁ was employed. Improvement in the pre-bronchodilator sRtot and Rint ≥ 25% and ≥ 35% was assessed after administration of salbutamol (400 µg) as well as allergen sensitization were measured.

Results

We included 135 children diagnosed with asthma into the analysis. All investigated parameters changed statistically significantly due to the bronchodilator administration in the examined patients. The FEV₁ was not as useful in diagnostics of asthma as the sRtot and Rint, taking into consideration the fait accompli that all the study participants had aptly been diagnosed as having asthma (p < 0.001). The differences between the sRtot and Rint were not statistically significant (p = 0.215).

Conclusions

Our results suggest that sRtot and Rint may be useful parameters in BT in clinical practice in the asthma diagnostic process in children.

Cross-sectional phenotyping of small airway dysfunction in preschool asthma using the impulse oscillometry system

Objective. Asthma is a chronic inflammatory airway disorder known to induce small airways dysfunction (SAD). It is important to develop tools to assess the presence and extent of SAD in daily clinical practice. An Impulse Oscillometry System (IOS) might detect SAD, but the validity of the underlying model (serial Resistive airway and Compliant tissue model: RC model) in diseased lungs remains questionable.Methods. Our objective was to evaluate the usefulness of parameters obtained from six electrical circuit models that were fitted to the measurements of impedance obtained with IOS in asthmatic children characterized by an abnormal lung function defined by an increased baseline interrupter resistance (Rint, z-score > +1.645).Results. The six models were tested in 102 asthmatic children (median age: 5.5 years). Two models allowed the description of 92/102 (90%) children: 74 by the extended RIC model (central and peripheral Resistance, Inertance and peripheral airway Compliance) and 18 by the Mead₁₉₆₉ model (extended RIC plus lung compliance). Thus, peripheral airway compliance and resistance were essential to describe lung function abnormalities of these asthmatic children. Parenchyma impairment (increased lung compliance) which was responsive to salbutamol was present in 18% of asthmatic children. After salbutamol, peripheral airway resistance decreased while peripheral airway compliance increased, arguing for asthma-related SAD. R5-20Hz independently correlated with the two latter parameters but was increased in two thirds of children with increased Rint only.Conclusion. Additional modeling of IOS results can be a reliable tool to assess the presence and extent of SAD in young asthmatic children.

Relationship between baseline and post-bronchodilator interrupter resistance and specific airway resistance in preschool children

BACKGROUND

The assessment of airway function in preschool children can be done using simple measurement techniques such as interrupter resistance (Rint) or specific airway resistance (sRaw).

OBJECTIVE

The aim of the study was to assess the relationship and the agreement between Rint and sRaw baseline measurements expressed in z-score and bronchodilator response (BDR) in accordance with the latest reference equations and recommended procedures.

METHODS

One hundred thirty children aged 3 to 6 years old, referred to our pediatric pulmonary function test unit for assessment of airway function were consecutively included. Children performed baseline and post-bronchodilator measurements of Rint and sRaw.

RESULTS

One hundred twenty baseline measurements were obtained (98.7%) with both techniques. At baseline there was a strong correlation between Rint and sRaw z-score (r = 0.5, P < .01) despite the poor agreement (Cohen Kappa coefficient 0.09 [-0.08; 0.26]). The agreement for BDR was fair, with Cohen Kappa coefficient (95% IC) = 0.33 (0.13; 0.54). Children with poorly or partially controlled asthma had both higher baseline Rint and sRaw (P < .01), and higher post-bronchodilator mean change (P < .01), than children with well-controlled asthma.

CONCLUSION

The poor agreement between the Rint and sRaw reference measurements demonstrates the lack of reliability of sole Rint or sRaw technique for airway obstruction diagnosis and the need to perform each technique concomitantly with BDR test. Other longitudinal and larger sample studies are needed to confirm the threshold value for a positive BDR, especially for sRaw.

Air pollution and airway resistance at age 8 years - the PIAMA birth cohort study

BACKGROUND

Air pollution has been found to adversely affect children's lung function. Forced expiratory volume in 1 s and forced vital capacity from spirometry have been studied most frequently, but measurements of airway resistance may provide additional information. We assessed associations of long-term air pollution exposure with airway resistance.

METHODS

We measured airway resistance at age 8 with the interrupter resistance technique (R_int) in participants of the Dutch PIAMA birth cohort study. We linked R_int with estimated annual average air pollution concentrations [nitrogen oxides (NO₂, NO_x), PM_2.5 absorbance ("soot"), and particulate matter < 2.5 μm (PM_2.5), < 10 μm (PM₁₀) and 2.5-10 μm (PM_coarse)] at the birth address and current home address (n = 983). Associations between air pollution exposure and interrupter resistance (R_int) were assessed using multiple linear regression adjusting for potential confounders.

RESULTS

We found that higher levels of NO₂ at the current address were associated with higher R_int [adj. mean difference (95% confidence interval) per interquartile range increase in NO₂: 0.018 (0.001, 0.035) kPa·s·L^- 1]. Similar trends were observed for the other pollutants, except, PM₁₀. No association was found between R_int and exposure at the birth address.

CONCLUSIONS

Our results support the hypothesis that air pollution exposure is associated with a lower lung function in schoolchildren.

Maternal hemoglobin and hematocrit levels during pregnancy and childhood lung function and asthma. The Generation R Study

OBJECTIVE

To examine the associations of maternal hemoglobin and hematocrit levels during pregnancy with childhood lung function and asthma, and whether adverse pregnancy outcomes and atopic predisposition modify the associations.

METHODS

In a population-based prospective cohort study among 3672 subjects, we measured maternal hemoglobin and hematocrit levels in early pregnancy, and lung function by spirometry and current asthma by questionnaire at age 10 years.

RESULTS

Higher maternal hematocrit levels, both continuously and categorized into clinical cut-offs, were associated with lower forced expiratory flow at 75% of forced vital capacity (FEF₇₅ ) in children (Z-score (95%CI): -0.04 (-0.07, -0.01), per increase of 1 SDS in hematocrit level; Z-score (95%CI) difference: -0.11 (-0.20, -0.03) compared with normal hematocrit levels, respectively), taking lifestyle and socio-economic factors into account. Adverse pregnancy outcomes and atopic predisposition did not modify the results. No associations of maternal hemoglobin and hematocrit with current asthma were observed.

CONCLUSION

Higher maternal hematocrit levels during pregnancy are associated with lower childhood lung function but not with risk of asthma. Adverse pregnancy outcomes and atopic predisposition do not modify these associations. Underlying mechanisms need to be further studied.

Associations of maternal and fetal 25-hydroxyvitamin D levels with childhood lung function and asthma: the Generation R Study

BACKGROUND

Exposure to low levels of vitamin D in fetal life might be a risk factor for childhood asthma.

OBJECTIVE

We examined whether 25-hydroxyvitamin D levels in mid-gestation and at birth were associated with higher airway resistance and inflammation, and increased risks of wheezing and asthma in school-age children.

METHODS

We performed a population-based prospective cohort study among 3130 mothers and their children. Maternal blood samples in mid-gestation and umbilical cord blood samples at birth were used to determine 25-hydroxyvitamin D levels. At age of 6, airway resistance (Rint) was measured by interrupter technique and airway inflammation by fractional exhaled nitric oxide (FENO) using NIOX chemiluminescence analyser. Wheezing and asthma were prospectively assessed by annual questionnaires until age 6.

RESULTS

Maternal levels of 25-hydroxyvitamin D in mid-gestation were not associated with Rint, FeNO, wheezing patterns, or asthma. Children in the lowest tertile of 25-hydroxyvitamin D levels at birth had a higher Rint (Z-score (95% confidence interval [95% CI]): -0.42 (-0.84, -0.01), P-value for trend< 0.05), compared to those in the highest tertile group. The effect estimate attenuated when child's current 25-hydroxyvitamin D level was taken into account [Z-score (95% CI): -0.55 (-1.08, 0.01)].

CONCLUSION AND CLINICAL RELEVANCE

Low levels of 25-hydroxyvitamin D at birth were associated with a higher airway resistance in childhood. Additional adjustment for child's current 25-hydroxyvitamin D level reduced the effect size of the association. Further studies are needed to replicate these findings and to examine mechanisms underlying the observed association and the long-term consequences.

Total specific airway resistance vs spirometry in asthma evaluation in children in a large real-life population

BACKGROUND

Total specific airway resistance (sRtot) has been introduced as an alternative technique to assess lung function with a particular application to younger children with asthma.

OBJECTIVE

To establish a diagnostic value of the body plethysmographic parameter (sRtot) in asthma diagnosis in young children.

METHODS

This was a prospective, noninterventional study. Children 4 to 18 year old with symptoms suggestive of asthma were included (n = 885). Subjects underwent body plethysmography and spirometry (when capable) with reversibility tests. Of 788 subjects who could perform spirometry in addition to body plethysmography, 578 were diagnosed with asthma. Subjects with asthma were treated for minimum of 6 months and then their asthma was confirmed or refuted.

RESULTS

In 471 patients, asthma diagnosis was confirmed after 6 months of antiasthmatic treatment; 142 patients were 4 to 6 years old and 329 were 7 to 18 years old. Change in response to bronchodilator in children with asthma was significant for sRtot (P = .02) but not for forced expiration volume in 1 second (P = .21); sRtot was more sensitive and specific in identifying children with reversible obstruction than spirometry. There was a significant association between sRtot and asthma diagnosis in patients 4 to 6 years old (odds ratio 1.02, 95% confidence interval 1.01-1.03, P = .001); to differentiate subjects with asthma from those without asthma, the optimal cutoff point for sRtot was 174.5%. A sRtot value higher than 174.5% was associated with a positive prediction of an asthma diagnosis in patients 4 to 6 years old. A ratio of forced expiration volume in 1 second to forced vital capacity below 80% was not significantly associated with asthma.

CONCLUSION

These data support the recommendation of performing sRtot rather than spirometry in young children as a fairly sensitive marker of asthma.

TRIAL REGISTRATION

www.ClinicalTrials.gov (NCT01805635).

Diagnostic value of lung function parameters and FeNO for asthma in schoolchildren in large, real-life population

BACKGROUND AND OBJECTIVE

To establish a diagnostic value of fractional exhaled nitric oxide (FeNO), interrupter resistance measurement (Rint), specific resistance of the airways (sRaw), spirometric parameters in asthma diagnosis in schoolchildren.

METHODS

It was a retrospective, cross-sectional study. We evaluated data from medical documentation of 6,439 children (aged 6-18) with symptoms suggestive of asthma, who attended our Pediatric Allergic Outpatient Clinic. Medical documentation of the patients was analyzed with special attention to the first ever obtained results (before the introduction of controller medication) of: FeNO, Rint, sRaw, spirometry, diagnoses of allergic diseases, and allergen sensitization (specific IgE results).

RESULTS

We included 3,612 children in the analysis. Older age, male gender, the presence of allergic rhinitis, sensitization to perennial and seasonal allergens, higher FeNO and Rint, and FEV1 /FVC <80% were significantly associated with asthma. We observed a significant association between FeNO and Rint in the prediction of asthma diagnosis. Optimal cutoff points to differentiate asthmatics from non-asthmatics were established. Thus, Rint >175.4% was defined as asthma-predicting Rint, and FeNO >15.8 ppb was defined as asthma-predicting FeNO. In all study subgroups, sensitivity for asthma-predicting Rint was significantly higher than for asthma-predicting FeNO with an inverse trend in specificity value.

CONCLUSION

Our results suggest that asthma-predicting Rint and, to a lesser extent, asthma-predicting FeNO, defined in the present study, could serve as a reliable tool to exclude asthma in schoolchildren. However, our results also indicate a clinically important fact that all lung function parameters or FeNO should be interpreted in the context of age, gender, allergy profile, and the presence of co-morbidities in schoolchildren. Pediatr Pulmonol. 2014; 49:632-640. © 2013 Wiley Periodicals, Inc.

Pulmonary function testing in children and infants

Pulmonary function testing is performed in children and infants with the aim of documenting lung development with age and making diagnoses of lung diseases. In children and infants with an established lung disease, pulmonary function is tested to assess the disease progression and the efficacy of therapy. It is difficult to carry out the measurements in this age group without disturbances, so obtaining results of good quality and reproducibility is challenging. Young children are often uncooperative during the examinations. This is partly related to their young age but also due to the long testing duration and the unpopular equipment. We address a variety of examination techniques for lung function assessment in children and infants in this review. We describe the measuring principles, examination procedures, clinical findings and their interpretation, as well as advantages and limitations of these methods. The comparability between devices and centres as well as the availability of reference values are still considered a challenge in many of these techniques. In recent years, new technologies have emerged allowing the assessment of lung function not only on the global level but also on the regional level. This opens new possibilities for detecting regional lung function heterogeneity that might lead to a better understanding of respiratory pathophysiology in children.

Challenges and limitations of testing efficacy of aerosol device delivery in young children

An increasing number of medical conditions are chronically or acutely managed with some form of aerosolized therapy. Due to the benefit of directly administering medications to the intended site of action, there is great interest in evaluating treatments for aerosol use. One of the major challenges in selecting and testing new drug-device combinations in children is the uncertainty regarding the appropriate outcome measure to choose. In studies involving adult patients, typically exacerbations of disease or airflow obstruction are assessed as endpoints in drug trials or device assessment. However, in young children, choosing endpoints to assess efficacy is difficult due to the potential lack of sensitive, noninvasive endpoints that are easily performed across sites. In this review, we discuss the challenges and limitations of selecting clinical endpoints for drug-device trials in the youngest population, with a focus on novel emerging technologies. This article provides an overview of preschool and infant pulmonary function testing, multiple-breath washout, imaging techniques including computed tomography and magnetic resonance imaging, flexible bronchoscopy in children, mucociliary clearance scans, and exhaled breath condensate.