Assessment and validation of bronchodilation using the interrupter technique in preschool children

Assessment of bronchodilator response in preschoolers: A systematic review

BACKGROUND

Several techniques can be used to assess bronchodilator response (BDR) in preschool-aged children, including spirometry, respiratory oscillometry, the interrupter technique, and specific airway resistance. However, there has not been a systematic comparison of BDR thresholds across studies yet.

METHODS

A systematic review was performed on all studies up to May 2023 measuring a bronchodilator effect in children 2-6 years old using one of these techniques (PROSPERO CRD42021264659). Studies were identified using MEDLINE, Cochrane, EMBASE, CINAHL via EBSCO, Web of Science databases, and reference lists of relevant manuscripts.

RESULTS

Of 1224 screened studies, 43 were included. Over 85% were from predominantly European ancestry populations, and only 22 studies (51.2%) calculated a BDR cutoff based on a healthy control group. Five studies included triplicate testing with a placebo to account for the within-subject intrasession repeatability. A relative BDR was most consistently reported by the included studies (95%) but varied widely across all techniques. Various statistical methods were used to define a BDR, with six studies using receiver operating characteristic analyses to measure the discriminative power to distinguish healthy from wheezy and asthmatic children.

CONCLUSION

A BDR in 2- to 6-year-olds cannot be universally defined based on the reviewed literature due to inconsistent methodology and cutoff calculations. Further studies incorporating robust methods using either distribution-based or clinical anchor-based approaches to define BDR are required.

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.

Can Asymptomatic or Non-Severe SARS-CoV-2 Infection Cause Medium-Term Pulmonary Sequelae in Children?

Pulmonary complications in adults who recovered from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been reported even in minimally symptomatic patients. In this study, lung ultrasound (LUS) findings and pulmonary function of children who recovered from an asymptomatic or mildly symptomatic SARS-CoV-2 infection were evaluated. We prospectively followed up for at least 30 days patients younger than 18 years who recovered from SARS-CoV-2 infection at the Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan (Italy). All enrolled patients underwent LUS. Airway resistance measured by the interrupter technique test was assessed in subjects aged 4-6 years, whereas forced spirometry and measurement of diffusing capacity of the lungs for carbon monoxide were performed in subjects older than 6 years. To evaluate a possible correlation between pulmonary alterations and immune response to SARS-CoV-2, two semiquantitative enzyme immune assays were used. We enrolled 16 out of 23 eligible children. The median age of enrolled subjects was 7.5 (0.5-10.5) years, with a male to female ratio of 1.7. No subject presented any abnormality on LUS, airway resistance test, forced spirometry, and diffusing capacity of the lungs for carbon monoxide. On the other hand, all subjects presented Ig G against SARS-CoV-2. In contrast in adults, we did not detect any pulmonary complications in our cohort. These preliminary observations suggest that children with an asymptomatic or mildly symptomatic SARS-CoV-2 infection might be less prone to develop pulmonary complications than adults.

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.

Lung function in a cohort of 5-year-old children born very preterm

OBJECTIVE

We assessed lung function and respiratory health in an area-based prospective cohort of preschool children born very preterm.

DESIGN

Lung function was measured by interrupter respiratory resistance (Rint) and forced oscillation technique (FOT) (respiratory resistance (Rrs8), reactance (Xrs8), and area under the reactance curve (AX)) at a median age of 5.2 years in a cohort of 194 children born at 22-31 weeks of gestational age (GA) in Tuscany, Italy. Respiratory symptoms and hospitalizations were also assessed.

RESULTS

Mean (SD) lung function Z-scores were impaired in preterm children for Rint (0.72 (1.13)), Xrs8 (-0.28 (1.34)), and AX (0.29 (1.41)). However, only a relatively small proportion of children (14.5-17.4%) had values beyond the 95th centile or below the 5th. Children with bronchopulmonary dysplasia (BPD) (n = 24) had slightly but not significantly impaired lung function indices in comparison with those without BPD (n = 170). In a multivariable analysis, lower GA was associated with worse lung function indices. Fifty-five percent of children had a history of wheezing ever and 21% had been hospitalized in their lifetime because of lower respiratory infections; 31% had wheezing in the last 12 months and this was associated with increased Rrs8 (P = 0.04) and AX (P = 0.08), and with decreased Xrs8 (P = 0.04) Z-scores.

CONCLUSIONS

Irrespectively of BPD preschool children born very preterm had impaired lung function indices, as measured by Rint and FOT, and a slightly higher burden of respiratory problems than the general population. GA seems to be crucial for lung development.

Interrupter resistance to measure dose-response to salbutamol in wheezy preschool children

AIM

Using a non-invasive lung function technique (interrupter resistance, Rint), we aimed to determine whether a dose-response to salbutamol could be detected in wheezy preschool children and if so, which dose of salbutamol should be administered to routinely evaluate bronchial reversibility.

METHOD

Wheezy children (3 to <7 years) were enrolled in a prospective multicenter study. Rint was measured at baseline, and after random assignment to a first dose (100 or 200 μg) and a second dose (cumulative dose: 400, 600, or 800 μg) of salbutamol. Data were analyzed using mixed modeling approach with an inhibitory maximal effect (I_max ) model, to account for a sparse sampling design. Simulations were performed to predict the percentage of children with significant Rint reversibility at several doses.

RESULTS

Final results were available in 99 children out of 106 children included. The model adequately fitted the data, showing satisfactory goodness-of-fit plots and a low residual error of 8%. Children with uncontrolled symptoms had lower I_max (ie, showed less reversibility) compared to children with totally/partly controlled symptoms (0.23 vs. 0.31, P < 0.001). Dose to reach 50% of I_max (D₅₀ ) was 51 μg. According to simulations, 88.1% of children with significant reversibility at dose 800 μg would already show significant reversibility at 400 μg.

CONCLUSION

Interrupter resistance was able to measure a dose-response curve to salbutamol in wheezy preschool children, which was similar to that of older patients. Young children require a high dose of salbutamol to correctly assess airway bronchodilator response, especially these with poor symptom control.

Lung function tests to monitor respiratory disease in preschool children

Pulmonary function tests are routinely used in the diagnosis and follow-up of respiratory diseases. In preschool children assessment and evaluation of lung function has always been challenging but improved techniques that require only minimal collaboration allowed obtaining reliable and useful results even in this group of patients. In this review we will describe the different techniques used in clinical practice to measure lung function in preschool children.(www.actabiomedica.it)

The bronchodilator response in preschool children: A systematic review

BACKGROUND

The bronchodilator response (BDR) is frequently used to support diagnostic and therapeutic decision-making for children who wheeze. However, there is little evidence-based guidance describing the role of BDR testing in preschool children and it is unclear whether published cut-off values, which are derived from adult data, can be applied to this population.

METHODS

We searched MEDLINE, EMBASE, Web of Science, and Cochrane databases (inception-September 2015) for studies reporting response to a bronchodilator in healthy preschool children, response following placebo inhalation, and the diagnostic efficacy of BDR compared with a clinical diagnosis of asthma/recurrent wheezing.

FINDINGS

We included 14 studies. Thirteen studies provided BDR data from healthy preschool children. Two studies reported response to placebo in preschool children with asthma/recurrent wheezing. Twelve studies compared BDR measurements from preschool children with asthma/recurrent wheeze to those from healthy children and seven of these studies reported diagnostic efficacy. Significant differences between the BDR measured in healthy preschool children compared with that in children with asthma/recurrent wheeze were demonstrated in some, but not all studies. Techniques such as interrupter resistance, oscillometry, and plethysmography were more consistently successfully completed than spirometry. Between study heterogeneity precluded determination of an optimum technique.

INTERPRETATION

There is little evidence to suggest spirometry-based BDR can be used in the clinical assessment of preschool children who wheeze. Further evaluation of simple alternative techniques is required. Future studies should recruit children in whom airways disease is suspected and should evaluate the ability of BDR testing to predict treatment response. Pediatr Pulmonol. 2016;51:1242-1250. © 2016 Wiley Periodicals, Inc.

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.

Feasibility of spirometry testing in preschool children

RATIONALE

The primary purpose of this study was to evaluate the feasibility of obtaining acceptable and reproducible spirometry data in preschool aged children (3-5 years) by technicians without prior experience with spirometry.

METHODS

Two technicians were trained to perform spirometry testing (ndd Easy on-PC) and to administer standardized questionnaires. Preschool aged children were enrolled from two Head Start centers and a local primary care clinic. Subjects were trained in proper spirometry technique and tested until at least two acceptable efforts were obtained or the subject no longer produced acceptable efforts.

RESULTS

200 subjects were enrolled: mean age 4.0 years (± 0.7 SD); age distribution: 51 (25.5%) 3 years old, 103 (51.5%) 4 years old, and 46 (23%) 5 years old. Fifty-six percent male and 75% Hispanic. One hundred thirty (65%) subjects produced at least one acceptable effort on their first visit: 23 (45%) for 3 years old, 67 (65%) for 4 years old, and 40 (87%) for 5 years old. The number of acceptable efforts correlated with age (r = 0.29, P < 0.001) but not gender. The mean number of acceptable efforts on the first visit was 2.66 (± 2.54 SD; range 0-10). One hundred twenty subjects (60%) had two acceptable efforts; 102 had FEV0.5 within 10% or 0.1 L and 104 had FVC within 10% or 0.1 L of best effort. The Asthma Health Screening Survey (AHSS) was 78% sensitive when compared to a specialist exam and 86% compared to a self-reported prior diagnosis of asthma.

CONCLUSIONS

Technicians without prior experience were able to obtain acceptable and reproducible spirometry results from the preschool aged children; the number of acceptable efforts correlated significantly with age.

Lung Function Tests in Preschool Children

The measurement of lung function by spirometry is routinely used to monitor and adequately treat children with asthma. The assessment and evaluation of lung function in children aged 3-5 years has been neglected for a long time because of the difficulty to perform forced expiratory maneuvers. However, the use of techniques such as the interrupter technique and the forced oscillation technique, which only require passive collaboration and where the only request to the child is to breathe at tidal volume, has overcome this limitation. Other techniques such as the measurement of specific airway resistance by plethysmography or the measurement of the lung clearance index using the multiple-breath washout might be helpful in this regard, although these techniques are less standardized in preschool 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.

Measurement of Interrupter Respiratory Resistance and Spirometry in Preschool Children: Influence of Respiratory Symptoms

Pulmonary function tests play an important role in the diagnosis and management of respiratory diseases in children. The purpose of the study was to evaluate lung function using the interrupter resistance technique (Rint) and spirometry (flow-volume and volume-time) in preschool children and to correlate the findings with respiratory symptoms. We studied 103 children (65 males, 38 females; mean age 5.2±0.7 years; range 3.6–5.8). For each child we collected family history concerning: respiratory diseases, skin prick tests, smoking during maternal pregnancy, history of gestational and neonatal period. All children performed lung function tests (Rint and spirometry) and skin prick test for inhalant and food allergens. Twenty-eight subjects (27.2%) had respiratory symptoms (RS). Expiratory Rint were performed in all subjects and spirometry was carried out on 76 children (73.8%). Spirometric indices were not statistically different between subjects without respiratory symptoms (controls) and RS children except for FEF25–75 expressed as a percentage of the predicted value (RS: 81.5±13.7% vs controls: 94.5±15.8%; p <0.001). Rint mean values were significantly higher in RS children than in controls (RS: 135.6 ±24.8% vs controls: 102.4 ±21.7%; p< 0.0001). We found a statistically negative correlation between Rint and the following Spirometric indices: FEV0.5 (R= −0.696; p < 0.0001), FEV, (R= − 0.728; p < 0.0001) and FEF25–75 (R= −0.681; p < 0.0001). In preschool children with respiratory disease we found significantly higher mean values of Rint and lower FEF25-75 than in the control group and a significant negative relationship between Rint and Spirometric indices.

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

In children unable to perform reliable spirometry, the interrupter resistance (R(int) ) technique for assessing respiratory resistance is easy to perform. However, few data are available on the possibility to use R(int) as a surrogate for spirometry. We aimed at comparing R(int) and spirometry at baseline and after bronchodilator administration in a large population of asthmatic children. We collected retrospectively R(int) and spirometry results measured in 695 children [median age 7.8 (range 4.8-13.9) years] referred to our lab for routine assessment of asthma disease. Correlations between R(int) and spirometry were studied using data expressed as z-scores. Receiver operator characteristic curves for the baseline R(int) value (z-score) and the bronchodilator effect (percentage predicted value and z-score) were generated to assess diagnostic performance. At baseline, the relationship between raw values of R(int) and FEV(1) was not linear. Despite a highly significant inverse correlation between R(int) and all of the spirometry indices (FEV(1) , FVC, FEV(1) /FVC, FEF(25-75%) ; P < 0.0001), R(int) could detect baseline obstruction (FEV(1) z-score ≤ -2) with only 42% sensitivity and 95% specificity. Post-bronchodilator changes in R(int) and FEV(1) were inversely correlated (rhô = -0.50, P < 0.0001), and R(int) (≥35% predicted value decrease) detected FEV(1) reversibility (>12% baseline increase) with 70% sensitivity and 69% specificity (AUC = 0.79). R(int) measurements fitted a one-compartment model that explained the relationship between flows and airway resistance. We found that R(int) had poor sensitivity to detect baseline obstruction, but fairly good sensitivity and specificity to detect reversibility. However, in order to implement asthma guidelines for children unable to produce reliable spirometry, bronchodilator response measured by R(int) should be systematically studied and further assessed in conjunction with clinical outcomes.

Reference values for airway resistance in newborns, infants and preschoolers from a Latin American population

BACKGROUND AND OBJECTIVE

Several studies have determined reference values for airway resistance measured by the interrupter technique (Rint) in paediatric populations, but only one has been done on Latin American children, and no studies have been performed on Mexican children. Moreover, these previous studies mostly included children aged 3 years and older; therefore, information regarding Rint reference values for newborns and infants is scarce.

METHODS

Rint measurements were performed on preschool children attending eight kindergartens (Group 1) and also on sedated newborns, infants and preschool children admitted to a tertiary-level paediatric hospital due to non-cardiopulmonary disorders (Group 2).

RESULTS

In both groups, Rint values were inversely associated with age, weight and height, but the strongest association was with height. The linear regression equation for Group 1 (n = 209, height 86-129 cm) was Rint = 2.153 - 0.012 × height (cm) (standard deviation of residuals 0.181 kPa/L/s). The linear regression equation for Group 2 (n = 55, height 52-113 cm) was Rint = 4.575 - 0.035 × height (cm) (standard deviation of residuals 0.567 kPa/L/s). Girls tended to have slightly higher Rint values than boys, a difference that diminished with increasing height.

CONCLUSIONS

In this study, Rint reference values applicable to Mexican children were determined, and these values are probably also applicable to other paediatric populations with similar Spanish-Amerindian ancestries. There was an inverse relationship between Rint and height, with relatively large between-subject variability.

Wearable interrupter module for home-based applications in a telemedical system dedicated to respiratory mechanics measurements

The mobile interrupter module, dedicated to the enhanced interrupter (EIT) measurement of respiratory mechanics in a home environment and capable of cooperation with a telemedical system, is presented. Characterized by noninvasiveness and minimal requirements regarding patient cooperation, the EIT algorithm is especially suitable for newborns, preschool children, and patients suffering from respiratory muscle impairment. Furthermore, this device enables access to raw data--without initial preprocessing--in a fully flexible measurement protocol (which is not available in any commercial apparatus), and the EIT procedure improves insight (the number and precision of assessed parameters) into the physiological system with respect to the classical occlusive methods.