Interrupter resistance in preschool children: measurement characteristics and reference values

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.

Small airway dysfunction is an independent dimension of wheezing disease in preschool children

BACKGROUND

Whether small airway dysfunction (SAD), which is prevalent in asthma, helps to characterize wheezing phenotypes is undetermined. The objective was to assess whether SAD parameters obtained from impedance measurement and asthma probability are linked.

METHODS

One hundred and thirty-nine preschool children (mean age 4.7 years, 68% boys) suffering from recurrent wheezing underwent impulse oscillometry that allowed calculating peripheral resistance and compliance of the respiratory system (markers of SAD) using the extended RIC model (central and peripheral resistance, inertance, and peripheral compliance). Children were classified using the probability-based approach of GINA guidelines (few, some, and most having asthma). A principal component analysis (PCA) that determined the dimensions of wheezing disease evaluated the links between SAD and asthma probability.

RESULTS

Forty-seven children belonged to the few, 28 to the some, and 64 to the most having asthma groups. Whereas their anthropometrics and measured parameters were similar, the most having asthma group exhibited the lowest mean value of airway inertance after bronchodilator probably due to airway inhomogeneities. PCA characterized four independent dimensions including a peripheral resistance (constituted by baseline peripheral compliance, Frs, R5Hz, R5-20Hz, X5Hz, and AX), a central resistance (baseline central resistance, R20Hz), anthropometrics (age and height), and asthma probability (wheezing patterns and therapeutic steps). Thus, PCA showed that the SAD markers were independent from clinical dimensions and were unable to differentiate wheezing phenotypes.

CONCLUSIONS

Lung function parameters obtained from impulse oscillometry and asthma probability were belonging to independent dimensions of the wheezing disease.

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.

Interrupter technique in infancy: Higher airway resistance and lower short-term variability in preterm versus term infants

BACKGROUND

In preschool children, measurement of airway resistance using interrupter technique (Rint) is feasible to assess the degree of bronchial obstruction. Although some studies measured Rint in infancy, values of Rint and its variability in preterm infants are unknown. In this study, Rint and its variability was measured at infancy and compared between healthy term and preterm infants.

METHODS

High quality Rint measurements in term (n = 50) and preterm (n = 48) infants were obtained at postmenstrual age of 42-50 weeks in two study centers in Switzerland. Intra-measurement variability of Rint in one measurement and inter-measurement variability between two subsequent measurements was assessed by coefficient of variation (CV).

RESULTS

Mean Rint in term infants was 4.2 ± (SD; 1.9) kPa · s · L^-1 and in preterm infants was 5.6 ± (2.8) kPa · s · L^-1 . Mean CV in term infants was 29.6 ± (14.9)% and in preterm infants was 20.2 ± (8.4)%. Rint was significantly lower (95%CI -2.31 to -0.38; P = 0.007) and CV significantly higher (95%CI 4.53-14.3; P < 0.001) in term compared to preterm infants. There were no differences in mean Rint and mean CV between the first and the second measurement obtained in a subgroup of term (n = 24, 48%) and preterm (n = 22, 45%) infants.

CONCLUSIONS

Our results suggest that differences in airway mechanics between term and preterm infants can be assessed with the interrupter technique during early infancy. Before clinical application of Rint measurements in this age group, reasons underlying the variability of measurements should be further investigated.

25-Hydroxyvitamin D concentrations, asthma and eczema in childhood: The generation R study

BACKGROUND & AIMS

A role of vitamin D in the development of respiratory and allergic disease in children remains unclear. It may be likely that vitamin D has an effect on airway inflammation, but only few studies examined the effect in children. We aimed to examine whether serum 25-hydroxyvitamin D (25(OH) vitamin D) concentrations are associated with the fraction of exhaled nitric oxide (FeNO), airway interrupter resistance (Rint), physician diagnosed asthma ever, wheezing and eczema in a population-based cohort study in 6 year old children.

METHODS

Serum 25(OH) vitamin D concentration was assessed in 3815 children. 25(OH) vitamin D concentrations ≥75 nmol/L were considered as sufficient, between 50 and 75 nmol/L as insufficient, and <50 nmol/L as deficient. FeNO and Rint were measured at the research center. Data on physician diagnosed asthma, wheezing, and eczema were obtained by parent-reported questionnaires.

RESULTS

In comparison with sufficient 25(OH) vitamin D concentration, deficient concentrations were associated with elevated FeNO of ≥25 ppb (OR: 2.54; 95% CI: 1.34-4.80). In addition, deficient and insufficient 25(OH) vitamin D concentrations were associated with a lower Rint (Z-score: -1.26; 95% CI: -1.66 to -0.85) (ß: -0.75; 95% CI: -1.08 to -0.42), and increased risks of eczema (OR: 1.65; 95% CI: 1.13-2.41) (OR: 1.44; 95% CI: 1.06-1.95). Insufficient 25(OH) vitamin D concentration were associated with a decreased risk of physician diagnosed asthma ever (OR: 0.59; 95% CI: 0.38-0.94).

CONCLUSIONS

Our results indicate that lower 25(OH) vitamin D levels are associated with elevated FeNO levels, but lower Rint values. Lower 25(OH) vitamin D levels are also associated with a decreased risk for asthma diagnoses but an increased risk for eczema.

Breastfeeding and asthma outcomes at the age of 6 years: The Generation R Study

BACKGROUND

Breastfeeding is associated with a lower risk of asthma symptoms in early childhood, but its effect at older ages remains unclear. We examined the associations of duration and exclusiveness of breastfeeding with asthma outcomes in children aged 6 years, and whether these associations were explained by atopic or infectious mechanisms.

METHODS

We performed a population-based prospective cohort study among 5675 children. Information about breastfeeding was collected by questionnaires. At age 6 years, we measured interrupter resistance (Rint) and fractional exhaled nitric oxide (FeNO). Information about wheezing patterns (early (≤3 years only), late (>3 years only), persistent (≤3 and >3 years)), and current asthma at 6 years was derived from repeated questionnaires.

RESULTS

Compared to children who were ever breastfed, those who were never breastfed had lower FeNO levels (sympercent (95% CI): -16.0 (-24.5, -7.5)) and increased risks of late and persistent wheezing (OR(95% CI): 1.69 (1.06, 2.69) and 1.44 (1.00, 2.07), respectively). Shorter duration of breastfeeding was associated with early wheezing and current asthma (1.40 (1.14, 1.73) and 2.19 (1.29, 3.71), respectively). Less exclusive breastfeeding was associated with early wheezing (1.28 (1.08, 1.53)). Breastfeeding duration and exclusiveness were not associated with FeNO or Rint. The associations were not explained by inhalant allergies, partly by lower respiratory tract infections in early life, and to a lesser extent by lower respiratory tract infections in later life.

CONCLUSIONS

Breastfeeding patterns may influence wheezing and asthma in childhood, which seems to be partly explained by infectious mechanisms.

Tidal flow variability measured by impedance pneumography relates to childhood asthma risk

Lung function variability is a fundamental feature of asthma but has been difficult to quantify in children due to methodological limitations. We assessed the feasibility and clinical implications of overnight flow variability measurement at home using impedance pneumography in young children.44 children aged 3-7 years with recurrent or persistent lower airway symptoms were recruited. Patients were divided into high- or lower-risk groups (HR and LR groups) based on their risk of asthma (modified Asthma Predictive Index), and a third group was formed of children who had a history of wheeze and who were treated with inhaled corticosteroids (ICS group). Tidal volume and the derived flow were recorded through skin electrodes using impedance pneumography at home during sleep. Quantities describing overnight change in expiratory flow-volume minimum curve shape correlation (CSRmin) and respiratory chaoticity (minimum noise limit (NLmin)) were derived.Recordings were successful in 34 children. CSRmin differed between the HR and LR groups (p=0.002) and between the HR and ICS groups (p=0.003), indicating a stronger change in flow profile shape in the HR group. NLmin differed between the HR and LR groups (p=0.014), indicating momentarily lowered chaoticity in the HR group.Impedance pneumography was found feasible for quantifying nocturnal lung function variability and the measured variability was associated with risk of asthma in young children.

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.

[Respiratory outcome of bronchopulmonary dysplasia in school-age children]

BACKGROUND

Bronchopulmonary dysplasia (BPD) is the most common chronic lung disease of infancy. The influence of its initial severity on long-term respiratory outcome remains uncertain.

OBJECTIVES

The purpose of this study was to examine the impact of "new BPD" on respiratory morbidity as well as respiratory function at rest and during exercise in school-age children.

METHODS

The 93 preterm newborns (<33 weeks gestation) presenting with BPD between 1997 and 2004 at the Rennes University Hospital had been proposed for a specific follow-up program. The children included in this cohort and presenting without severe handicap or motor deficit were eligible for this observational retrospective study. Their standardized clinical evaluation and the results of the pulmonary function tests and cardiopulmonary exercise tests performed between the ages of 7 and 14 years were studied. BPD was considered to be moderate when respiratory or oxygen support continued at 36 weeks gestation with an FiO2 less than 30% and severe when FiO2 was greater than 30%.

RESULTS

Among the 36 children assessed, the initial severity of the BPD was mild in 12 cases, moderate in 12 cases, and severe in 12 cases. The mean age at the time of the pulmonary function test (PFT) was 9.9 (±1.9) years, 19 children (53%) had respiratory symptoms during the year before the test, and six (17%) underwent long-term treatment. The PFT was abnormal for 32 children (89%): 23 showed airway obstruction, 16 hyperinflation, three increases in bronchial reactivity, and two restrictions. The residual volume/total lung capacity ratio was the only parameter related to the severity of BPD (P<0.05). The cardiopulmonary exercise test was given to 35 children: 15 of them had normal exercise ability but with a limited ventilatory reserve.

CONCLUSIONS

Half of the children included in this "new-BPD" follow-up cohort had clinical respiratory morbidity and most of the children followed presented with persistent alterations in pulmonary function tests at school age, which were not associated with significant alterations in the maximum aerobic performance.

Foetal and infant growth patterns, airway resistance and school-age asthma

BACKGROUND AND OBJECTIVE

Preterm birth, low birth weight and rapid infant weight gain are associated with increased risks of asthma symptoms in childhood. The underlying mechanism may include persistently higher airway resistance (Rint). The aim of our study was to examine the associations of longitudinally measured foetal and infant growth characteristics with Rint and asthma outcomes in school-age children.

METHODS

This study was embedded in a population-based prospective cohort study in Rotterdam, The Netherlands. Foetal growth was estimated by ultrasound in the second and third trimesters. Infant growth was measured at birth, 3, 6 and 12 months. At age 6 years, Rint was measured, and information about wheezing and asthma was obtained by questionnaires. The number of subjects per analysis differed per available outcome (3954-5066 subjects).

RESULTS

Longitudinal growth analyses showed that school-age children with increased Rint had lower foetal length growth and weight gain, and lower infant length growth. Children with persistent wheezing until age 6 years and physician-diagnosed asthma had a higher Rint compared with children who never wheezed or without asthma (difference z-scores Rint: 0.58 (0.19, 0.97) and 0.55 (0.15, 0.95), respectively).

CONCLUSION

Rint in school-age children is influenced by foetal growth restriction and is associated with asthma outcomes. See article, page 574.

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.

The Tools of the Trade - Physiological Measurements of the Lungs

Pulmonary function assessment plays an integral part in the clinical management of school-aged children with respiratory disease. Pulmonary function tests (PFTs) are being increasingly applied in infants and preschool children too, albeit only in specialised centres. PFTs, when performed and interpreted accurately, provide objective outcome measures which can be used clinically to guide management, for prognostic purposes and in epidemiological research studies. They can be used to determine the nature and severity of lung disease, to ascertain response to treatment and to monitor disease progression. PFTs are rarely diagnostic in their own right with the exception of asthma, but are valuable adjuncts and before clinicians select a PFT they must know what the results are likely to be in the disease being considered. Spirometry and tests of airway calibre and function are the most widely used PFTs, as diseases in children commonly affect airway function. As such, spirometry should be a standard part of the assessment of school-age children who present to the pediatrician with chronic respiratory symptoms. This review will provide a bird's eye view of currently available PFTs in children to assist in the diagnosis and management of respiratory disorders.

Respiratory disease and respiratory physiology: putting lung function into perspective: paediatric asthma

Dealing with paediatric asthma in daily practice, we are mostly interested in the airway function: the hallmark of asthma is the variability of airway patency. Various pulmonary function tests (PFT) can be used to quantify airway caliber in asthmatic children. The choice of the test is based on the developmental age of the child, knowledge of the diagnosis/underlying pathophysiology, clinical questions and reasoning, and treatment. PFT is performed to monitor the severity of asthma and the response to therapy, but can also be used as a diagnostic tool, and to study growth and development of the lungs and airways. This review aims to provide clinicians an overview of the differences in assessing PFT in infants and preschool children compared with older cooperative children, which tests are feasible in infants and young children, the limitations of and usefulness of these tests, and of their interpretation in these age groups.

Evaluation of Airway Resistance in Children with Juvenile Idiopathic Arthritis

Background: Pneumonitis, pleuritis, and pulmonary interstitial infiltration have been described in patients with juvenile idiopathic arthritis (JIA). However, the pulmonary involvement of JIA is not often clinically apparent. There are few studies based on pulmonary function in children having only a diagnosis of JIA. The aim of the present study is to determine whether children with JIA have airway resistance and flow impairments measured by easily applied interrupter technique. Method: We performed interrupter resistance (Rint) measurements in children with JIA and in healthy control subjects who had no respiratory symptoms or diseases. Results: Fifty-eight children with the diagnosis of JIA (Mean age=12.5±2.75 years; range 7-17 years) and 33 healthy subjects (Mean age=11.8±2.62 years; range 6-16 years) were included in the study. The mean value of tidal peak flow during expiration measured by the interrupter technique was significantly lower in the JIA study group (0.73±0.11 L/s) compared to the healthy control group (0.79±0.08 L/s; p=0.01). Rint values measured during inspiration (Rint_insp) and during expiration (Rint_exp) were higher in the JIA study group (Rint_insp=0.28±0.16 Kpa/L/s; Rint_exp=0.30±0.50 Kpa/L/s) compared to the healthy control group (Rint_insp=0.26±0.11 Kpa/L/s; Rint_exp=0.23±0.08 Kpa/L/s; p>0.05). There was also a positive correlation between C-reactive protein level and median expiratory interrupter resistance (Rint_exp; r=0.50, p=0.005). Conclusion: The interrupter technique is a noninvasive and feasible technique and can be used to assess airway abnormalities in children with JIA who cannot successfully complete spirometry.

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.

An official American Thoracic Society workshop report: optimal lung function tests for monitoring cystic fibrosis, bronchopulmonary dysplasia, and recurrent wheezing in children less than 6 years of age

Although pulmonary function testing plays a key role in the diagnosis and management of chronic pulmonary conditions in children under 6 years of age, objective physiologic assessment is limited in the clinical care of infants and children less than 6 years old, due to the challenges of measuring lung function in this age range. Ongoing research in lung function testing in infants, toddlers, and preschoolers has resulted in techniques that show promise as safe, feasible, and potentially clinically useful tests. Official American Thoracic Society workshops were convened in 2009 and 2010 to review six lung function tests based on a comprehensive review of the literature (infant raised-volume rapid thoracic compression and plethysmography, preschool spirometry, specific airway resistance, forced oscillation, the interrupter technique, and multiple-breath washout). In these proceedings, the current state of the art for each of these tests is reviewed as it applies to the clinical management of infants and children under 6 years of age with cystic fibrosis, bronchopulmonary dysplasia, and recurrent wheeze, using a standardized format that allows easy comparison between the measures. Although insufficient evidence exists to recommend incorporation of these tests into the routine diagnostic evaluation and clinical monitoring of infants and young children with cystic fibrosis, bronchopulmonary dysplasia, or recurrent wheeze, they may be valuable tools with which to address specific concerns, such as ongoing symptoms or monitoring response to treatment, and as outcome measures in clinical research studies.

Opening interrupter technique in pre-school children with chronic respiratory diseases: a perspective case-control study in the diagnosis of airway hyperesponsiveness

BACKGROUND

Optimal treatment for pediatric respiratory diseases is strictly related to follow-up evaluations of lung function. The aim of our study was to show the efficacy of the Opening Interrupter Technique in diagnosing the presence of airway obstruction in pre-school children.

MATERIALS AND METHODS

Our study was a prospective case-control study, evaluating 82 patients affected by asthma and/or cystic fibrosis (CF) and 50 healthy pre-school children, as control group. All patients were 3- to 5-years old and they were followed by our Pediatric Department, University of Catania, Italy, from February 2011 to June 2012. Measurements of respiratory resistance (o-Rint) by the opening interrupter technique were made with the MasterScreen PFT device, Jaeger GmbH, Würzburg, Germany, during quiet breathing. The presence of airway obstruction was detected as a value of o-Rint higher than two standard deviations (SD) compared with the theoretical data.

RESULTS

We found higher values of o-Rint in asthmatic patients than in the control group, with a high statistical difference (p < 0.0001). The same results were found when we compared patients with CF and the control group (p < 0.0001). Nevertheless, we did not find any significant statistical difference between respiratory resistances measured in asthmatic and patients with CF (p > 0.05). There was a significant inverse correlation between o-Rint and height only in asthmatic and patients with CF, but not in healthy controls (p < 0.05).

CONCLUSIONS

In our study, the opening interrupter technique was efficient in detecting the presence of obstruction in chronic patients affected by asthma and CF.

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.

Forced oscillation technique and childhood asthma

Most infants and preschool children are not able to voluntarily perform the physiological maneuvers required to complete the pulmonary function tests that are used in adults and older children. Recently, commercial devices using forced oscillation technique (FOT) suitable for young children have become available. In devices with FOT, an oscillation pressure wave is generated by a loud speaker, is applied to the respiratory system, usually at the mouth, and the resulting pressure-flow relationship is analyzed in terms of impedance (Zrs). Zrs encompasses both resistance (Rrs) and reactance (Xrs). Rrs is calculated from pressure and flow signals, and is a measure of central and peripheral airway caliber. Xrs is derived from the pressure in the phase with volume and is related to compliance (Crs) and inertance (Irs). These parameters individually indicate the condition of the small and large airways in each patient and indirectly suggest the presence of airway inflammation. It is agreed that the clinical diagnostic capacity of FOT is comparable to that of spirometry. One of the advantages of FOT is that minimal cooperation of the patient is needed and no respiratory maneuvers are required. The use of FOT should be considered in patients in whom spirometry or other pulmonary function tests cannot be performed or in cases where the results of other tests appear to be unreliable. In addition, this approach is effective in assessing bronchial hyperresponsiveness. Considering these qualities, FOT is a useful method to study pulmonary function in preschool children with asthma.

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.

A new approach to the determination of airway resistance: interrupter technique vs. plethysmography

OBJECTIVE

To determine the agreement between interrupter resistance (Rint) and airway resistance (Raw) by plethysmography in order to verify the clinical applicability of the interrupter technique.

METHODS

The Rint technique was performed with the patients in a sitting position, during exhalation, with a nose clip and cheek support. Plethysmography was carried out in accordance with standard protocols. All measurements were taken prior to and after the administration of an inhaled bronchodilator via a metered dose inhaler with a spacer.

RESULTS

The study comprised 99 consecutive patients referred to the Porto Alegre Hospital de Clínicas, located in the city of Porto Alegre, Brazil, for pulmonary function testing. Patient ages ranged from 18 to 82 years, and 52 of the patients were women. In the patients with FEV1 ≥ 60% of predicted, there was good agreement between the methods (r = 0.8; intraclass correlation coefficient = 0.8). The Rint values were lower than were those of Raw by plethysmography in the patients with more severe disease. However, there was good agreement between Rint ≥ 4 cmH2O L(-1) s(-1) and Raw by plethysmography > 2.5 cmH2O L(-1) s(-1) (likelihood ratio > 8; kappa coefficient = 0.73).

CONCLUSIONS

In the patients with less severe disease, there was good agreement between Rint and Raw by plethysmography. The agreement between the two methods was also strong regarding the detection of an increase in Raw. The Rint technique is a potentially useful method for the evaluation of adult patients.

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

OBJECTIVE

To determine and validate a cut-off value for bronchodilation using the interrupter resistance (Rint) in preschool children.

PATIENTS AND METHODS

Rint was measured in 60 healthy children (age range 2.7-6.4 years) before and after salbutamol inhalation (200 microg). Four potential methods for assessing BDR were evaluated: percent change from baseline, percent change of predicted values, absolute change in Rint, and change in Z-score. These cut-off values, determined as the fifth percentile of the healthy group, were applied to children referred for the assessment of recurrent wheezing, classified on the basis of acute symptoms and/or abnormal chest examination into symptomatic (n = 60, age range 2.9-6.1 years) and asymptomatic (n = 60, age range 2.5-5.7 years) groups.

RESULTS

The cut-off values for bronchodilation calculated in healthy children were: -32% baseline; -33% predicted; -0.26 kPa L(-1) sec; and -1.25 Z-scores. Assessing BDR in children with a history of wheezing by either a decrease in absolute Rint or a decrease in Z-score gave sensitivity, specificity, negative predictive value, and positive predictive value all >80% for detecting children with current respiratory symptoms.

CONCLUSIONS

Both a decrease in Rint > or =0.26 kPa L(-1) sec and a decrease in Z-score of > or =1.25 are appropriate for assessing BDR in preschool children with a history of recurrent wheezing. As Z-score is a more general solution, we recommend using a change in Z-score to determine BDR in preschool children. Further longitudinal studies will be required to determine the clinical utility of measuring BDR in managing lung disease in such children.

Lung function testing in preschool-aged children with cystic fibrosis in the clinical setting

In cystic fibrosis (CF) lung function testing is a means of monitoring progression of lung disease. The preschool years have often been referred to as the "silent years" due to the previous lack suitable measures of lung function testing in this age group. This review outlines the various techniques of lung function testing in preschool children with CF in the clinical setting. This includes measures requiring tidal breathing including the forced oscillation technique, the interrupter technique, plethysmography, and multiple breath washout, as well as spirometry that requires respiratory maneuvers. We describe the feasibility and variability of different lung function methods used in preschoolers and report measurements made during tidal breathing have greater feasibility, although greater variability compared to spirometry. We also report associations with lung function and markers of CF lung disease. In the preschool age group measurements made during tidal breathing may be more appropriate in the clinic setting than those that require a higher degree of cooperation and specific respiratory maneuvers.maneuvers.

Recombinant human DNase in children with airway malacia and lower respiratory tract infection

BACKGROUND

Children with airway malacia often have protracted courses of airway infections, because dynamic airway collapse during coughing results in impaired mucociliary clearance. The aim of this study was to determine the effect of the mucolytic drug recombinant human deoxyribonuclease (rhDNase) on the recovery of respiratory symptoms in children with airway malacia and lower respiratory tract infection (LRTI).

METHODS

In a randomized double-blind controlled clinical trial, 40 children with airway malacia and LRTI were randomly assigned to receive either 2.5 mg nebulized rhDNase or placebo twice daily for 2 weeks. The primary endpoint was the change in the cough diary score (CDS) (scale 0-5) from baseline to the second week of treatment. Secondary endpoints were VAS symptom scores for cough, dyspnea, and difficulty in expectorating sputum, need for an antibiotic course, and lung function data (FVC, FEV(1), FEF(75), R(int(e))).

RESULTS

There was no significant difference in the mean change in CDSs from baseline between the rhDNase group and the placebo group (mean difference for daytime 0.19 (95% CI -0.53 to 0.90); for nighttime 0.38 (95% CI -0.30 to 1.05). Proportions of patients requiring antibiotics, and the mean changes in symptom scores and lung function from baseline did not significantly differ between both groups.

CONCLUSION

Treatment with 2 weeks of nebulized rhDNase does not enhance recovery or reduce the need for antibiotics in children with airway malacia and LRTI. (Controlled-trials.com number, ISRCTN85366144).

[Lung function testing and assessment of distal airways in asthma]

INTRODUCTION

Small airways are defined (in humans) as those<2mm in diameter.

BACKGROUND

They were originally described as the "quiet zone" of the lungs contributing less than 10% of the total resistance to airflow. Pulmonary function tests remain the most used method to assess distal airway flow limitation.

VIEWPOINTS

However, these tests are limited in adults and also in children because MEF25-75% and FEF50% are highly variable spirometric indices and they depend on vital capacity, which increases with expiratory time in obstructed subjects. There is a need for promising non invasive new tools like the forced oscillation technique to measure resistance. The increased availability of the exhaled fraction of nitric oxide (FeNO) measurement means that this method is accessible and attractive.

CONCLUSION

The production of nitric oxide (NO) can be assessed by measuring the fraction of NO during a prolonged expiration (FENO) or by estimating other parameters of NO exchange including the alveolar NO concentration (CalvNO) and may provide information about small airway inflammation and assist the optimal control of the disease.

Airway resistance in children measured using the interrupter technique: reference values

OBJECTIVE

The interrupter technique is used for determining interrupter resistance (Rint) during quiet breathing. This noninvasive method requires minimal cooperation and can therefore be useful in evaluating airway obstruction in uncooperative children. To date, no reference values have been determined for Rint in a Brazilian population. The objective of this study was to define a prediction equation for airway resistance using the interrupter technique for healthy children aged 3-13 years.

METHODS

This was a prospective, cross-sectional study involving preschool and school children in Porto Alegre, Brazil, in whom Rint was measured during peak expiratory flow.

RESULTS

One-hundred and ninety-three children were evaluated. Univariate analysis using linear regression showed that height, weight and age correlated significantly and independently with Rint. Multiple regression with height, weight, age and gender as variables resulted in a model in which only height and weight were significant, independent predictors of Rint. Collinearity was identified among height, weight and age.

CONCLUSIONS

Reference values and an equation for calculating Rint in healthy children were obtained and are adjusted for height.

Depressed children with asthma evidence increased airway resistance: "vagal bias" as a mechanism?

BACKGROUND

Depression is prevalent in pediatric asthma, and implicated in asthma morbidity and mortality. Pathways linking stress, depression, and asthma are unknown.

OBJECTIVES

To examine, under controlled laboratory conditions, pathways by which depressive states affect airway function via autonomic dysregulation.

METHODS

Participants were 171 children with asthma, age 7 to 17 years, presenting to an emergency department for asthma exacerbation. Forty-five children with asthma and high depressive symptoms (D) were contrasted with 45 with low/no depressive symptoms (ND). Depressive symptoms, asthma disease severity, vagal and sympathetic reactivity to film stressors, airflow (FEV1), and airway resistance were compared between the groups. A subgroup with greater airway reactivity (nonmedicated FEV1<80% predicted) was also studied. Correlations among variables were examined for the entire sample.

RESULTS

Groups did not differ in demographics, disease severity, medications, or adherence. The D group with FEV1<80% predicted showed greater airway resistance throughout all conditions (P = .03), and vagal bias in the film stressors. The D group's vagal response was significant for the sad stimuli: family distress/loss (P = .03), dying (P = .003), and death (P = .03). The ND group showed sympathetic activation to sad stimuli: lonely (P = .04) and dying (P = .04). Depressive symptoms were correlated with respiratory resistance (r = .43; P = .001) and vagal bias in scene 3 (r = .24; P = .03), and vagal bias (scene 3) was correlated with postmovie airway resistance (r = 0.39; P = .004).

CONCLUSIONS

Children with asthma and depressive symptoms manifest vagal bias when emotionally stressed. Those with depressive symptoms and FEV1<80% manifest greater airway resistance. Depression, vagal bias, and airway resistance were intercorrelated for the full sample.

Smoke exposure interacts with ADAM33 polymorphisms in the development of lung function and hyperresponsiveness

INTRODUCTION

ADAM33 is the first identified asthma gene by positional cloning, especially asthma combined with bronchial hyperresponsiveness (BHR). Moreover, ADAM33 is associated with early-life lung function and decline of forced expiratory volume in 1 s (FEV(1)) in the general population. In utero and postnatal cigarette smoke exposure (CSE) are associated with reduced lung function, and development of BHR and asthma. We hypothesized that this may occur via interaction with ADAM33.

AIM

To replicate the role of ADAM33 in childhood lung function and development of BHR and asthma. Furthermore, we investigated gene-environment interaction of ADAM33 with in utero and postnatal CSE in the Dutch PIAMA cohort.

METHODS

Six ADAM33 single-nucleotide polymorphisms (SNPs) were genotyped. Rint was measured at age 4 and 8 years, FEV(1) and BHR at age 8 years; asthma was based on questionnaire data at age 8.

RESULTS

In the total cohort, the rs511898 A, rs528557 C, and rs2280090 A alleles increased the risk to develop asthma (+BHR). There existed interaction between in utero but not postnatal CSE and the rs528557 and rs3918396 SNPs with respect to development of BHR, the rs3918396 SNP with Rint at age 8 and the rs528557 SNP with FEV(1)% predicted.

CONCLUSIONS

We confirm associations between ADAM33 and the development of asthma (+BHR). This is the first study suggesting that interaction of in utero CSE with ADAM33 results in reduced lung function and the development of BHR, which needs further confirmation.

The effects of paced breathing on respiratory resistance are minimal in healthy individuals

Paced breathing has been criticized for its presumed influences on autonomic and respiratory regulation, among that on respiratory resistance. It has been speculated that excessive pulmonary stretch receptor activation through high tidal volume (V(T)) would be the mechanism underlying such influences. However, the idea of airway dilation by paced breathing has remained untested. We analyzed inspiratory and expiratory resistance measured by forced oscillations in 26 healthy participants during baseline and two paced breathing conditions, regular pacing with instructions to alter rate only and pacing with additional instructions to alter volume randomly throughout the task. In each condition, four 3-min paced breathing trials at 8, 10.5, 13, and 18 breaths/min were administered. Despite pronounced changes in respiration rates and V(T) across pacing trials, neither inspiratory nor expiratory resistance were changed significantly under the regular paced breathing condition. A small reduction in resistance was only observed under conditions of variable volume at 18 breaths/min. Thus, regular paced breathing at different speeds across a range of naturally occurring breathing frequencies has only minimal effects on resistance of the airway passages.

Early detection of lung disease in children with cystic fibrosis using lung function

Measurement of lung function is routine in older children and adults with cystic fibrosis (CF) but not in infants and preschool children. Pulmonary infection, neutrophil-dominated inflammation and clinical exacerbations in young children similar to those seen in older subjects have been identified and highlight the urgent need to evaluate lung function in early life. Mounting evidence suggests lung function techniques sensitive to changes in peripheral lung function may be required to detect the early functional abnormalities in infants and preschool children with CF. In addition, the majority of studies in young children with CF have not reported longitudinal data and therefore the prognostic potential of existing lung function methods to track disease progression is poorly understood. This review aims to describe recent research findings in infants and preschool children and to outline currently available lung function techniques, issues around their standardization and their relative advantages and disadvantages in young children with CF.

Effect of bacterial filter on measurement of interrupter resistance in preschool and school-aged children

BACKGROUND

The interrupter technique is increasingly used in preschool children to assess airway resistance (Rint). Use of a bacterial filter is essential for prevention of cross-infection in a clinical setting. It is not known how large an effect this extra resistance and compliance exert upon interrupter measurements, especially on obstructive airways and in smaller children. We aim to determine the contribution of the filter to Rint, in a sample of children attending lung function testing at an asthma clinic.

METHODS

Interrupter measurements were performed according to ATS/ERS guidelines during quiet normal breathing at an expiratory flow trigger of 200 ml s(-1), with the child seated upright with cheeks supported and wearing a nose clip. A minimum of 10 interrupter measurements was made with and without a bacterial filter. Spirometric and plethysmographic tests were also performed.

RESULTS

A small but significant difference (0.12 (95% CI 0.06-0.17) kPa s L(-1), P = 0.0002) with 2x SD of 0.34 kPa s L(-1) was observed between Rint with and without filter in 39 children, with a large spread. This difference was not dependent on Rint magnitude, age or height, nor on lung function parameters (effective resistance, forced expiratory volume in 1 sec, and maximal expiratory flow at 50% of expired vital capacity).

CONCLUSIONS

A bacterial filter causes a small difference but is not clinically significant, with a wide spread comparable to the variability of the technique and recommended cut-offs for assessing repeatability and bronchodilation. Age, height or severity of obstruction need not be corrected for in general.

Fluticasone or montelukast for preschool children with asthma-like symptoms: Randomized controlled trial

RATIONALE

Beneficial effects of anti-inflammatory therapy such as fluticasone propionate (FP) and montelukast (Mk) have been demonstrated in preschool children with asthma. However, comparative studies are lacking in this age group. Therefore, we conducted a study to evaluate and compare the effect of FP and Mk in preschool children with asthma-like symptoms.

METHODS

In this multicenter, randomized, placebo-controlled, double-blind, double-dummy trial, children aged 2-6 years with asthma-like symptoms were included. In total, 63 children were randomly allocated to receive FP (25), Mk (18) or placebo (20) for 3 months. The primary outcome was the daily symptom score (wheeze, cough, shortness of breath) as recorded by caregivers in a symptom diary card. Secondary endpoints were rescue medication free days, blood eosinophils and lung function (interrupter technique and forced oscillation technique (FOT)).

RESULTS

During the 3 months study period, symptoms improved in all 3 groups, with a statistically significant difference between FP and placebo in favor of the FP group (p=0.021). A significant reduction in circulating eosinophils after 3 months of treatment was found in the Mk group only (p=0.008), which was significantly different from the change found in the placebo group (p=0.045). With the exception of frequency dependence (measured by FOT), which showed a difference between FP and Mk after 3 months of treatment in favor of the FP group (p=0.048), no differences in lung function within or between groups were found.

CONCLUSIONS

In spite of a lack of power, our results suggest that FP has a beneficial effect on symptoms and Mk on blood eosinophil level as compared to placebo. Except for a difference in one lung function parameter after 3 months between FP and Mk in favor of the FP group, this study revealed no differences between FP and Mk.

Lung function measurement in prematurely born preschool children with and without chronic lung disease

OBJECTIVE

Prematurely born infants often have recurrent wheeze and long-term respiratory morbidity at follow-up. Assessment of airways obstruction in preschool children is feasible using the interrupter resistance (Rint) but has rarely been examined in preterm children with and without chronic lung disease (CLD). The objective of this study was to determine lung function measured by the interrupter technique, its feasibility in the ambulatory setting and respiratory health in prematurely born preschool children with and without CLD.

STUDY DESIGN

Preterm children of 2 to 4 years with severe CLD (>30% oxygen at 36 weeks and discharged home receiving supplemental oxygen) (n=43, median gestational age 27 weeks and median birth weight 995 g) and without CLD (n=33, median gestational age 29 weeks and median birth weight 1366 g) attempting lung function test for the first time were enrolled. Respiratory symptoms score was calculated using a questionnaire. A single set of 10 consecutive Rint measurements was obtained using a portable device (MicroRint). Median of at least five occlusions with consistent shape of mouth pressure-time curves was taken to be a Rint measurement. To assess feasibility the children were categorized as 'satisfactory', 'failure' and 'rejected' depending on the outcome of the test. Outcome variables were respiratory symptoms score and Rint.

RESULT

Satisfactory Rint measurement was obtained in 46 (61%) children, 9 (36%) 2-year olds, 17 (65%) 3-year olds and 20 (80%) 4-year olds. As compared with the preterm control children (n=18), CLD children (n=28) had significantly higher respiratory symptoms score (18.5 vs 6, P<0.01) and Rint expressed as absolute values (kPa l(-1)) and z-scores (1.33 vs 1.16 and 1.42 vs 1.0, P<0.01), respectively.

CONCLUSION

Rint measurement is feasible in prematurely born children of preschool age in the ambulatory setup. Preschool children with severe CLD may be identified from preterm children without CLD by increased Rint that may be used as a screening tool and as an outcome measure for interventions.

Reference equations for pulmonary function tests in preschool children: a review

Recent developments in pulmonary function tests (PFTs) in preschool children (2-5 years of age) have meant that objective assessments of respiratory function are now possible for this age group. However, the application and interpretation of these tests may be limited by the relative paucity of appropriate reference equations. This review summarizes available preschool reference equations, identifies the current gaps and limitations in the methodologies and statistics used and proposes future directions for improving reference data. A PubMed search which included the MeSH terms (preschool [2-5years]), (respiratory function test), and (reference value) yielded 214 publications which were screened to identify 34 publications presenting 36 reference equations for seven techniques. There were considerable differences with respect to population characteristics, recruitment strategies, equipment and methodologies and reported parameters both within and between each measurement technique. Despite an increasing number of reference equations for PFT for preschool children, the extent to which these can be generalized to other populations may be limited in some cases by inclusion of relatively few children less than 5 years of age, a lack of details regarding the sample populations and measurement techniques and/or inappropriate statistical analysis. A fresh approach based on large sample sizes, clearly documented population characteristics, equipment and protocols, and more rigorous modern statistical methods both for developing reference equations and interpreting results could enhance clinical application of these tests. This in turn would maximize the tremendous opportunities to detect early lung disease offered by the recent surge in developing suitable tests for preschool children.

How should we estimate driving pressure to measure interrupter resistance in children?

Interrupter resistance (R(int)) is a widely used measure of airway caliber, but concerns remain about repeatability and sensitivity. Some R(int) variability may derive from the linear back-extrapolation algorithm (LBE 30/70) usually used to estimate driving pressure. To investigate whether other methods of estimating driving pressure could improve repeatability and sensitivity, we studied 39 children with asthma. Two measurements of R(int)-each the median of 10 interruptions-were made 5 min apart, and 14 children had a third measurement after bronchodilator (R(int)BD). Mouth pressure transients were analyzed using several algorithms, to compare the magnitude, repeatability, and sensitivity to bronchodilator change of R(int) values yielded. Algorithms taking driving pressure from later in the transient, predictably, yielded higher values of R(int) than those which back-extrapolated to time of valve closure. Algorithms which did not rely on back-extrapolation, including mean oscillation pressure (MOP) and mean plateau pressure (MP 30/70) had better repeatability. Sensitivity to detect change, calculated as ratio of bronchodilator response to repeatability coefficient (DeltaR(int)/CR), was also better for non-extrapolating algorithms: MP 30/70 1.67, LBE 30/70 1.28 (P = 0.0004). Measuring R(int) using techniques other than conventional back-extrapolation may give more consistent and clinically useful results, and these approaches merit further exploration.

Interrupter resistance short-term repeatability and bronchodilator response in preschool children

Interrupter resistance (Rint) technique can be easily and successfully performed in preschool children. The establishment of Rint short-term repeatability is essential to interpret any Rint change after a pharmacological intervention.

AIMS OF THE STUDY

In preschool children with asthma or chronic cough: (1) to assess two indices of short-term repeatability: (a) intra-measurement and (b) within-occasion between-test repeatability; (2) to study the relationship between short-term repeatability and bronchodilator response (BDR).

RESULTS

Rint intra-measurement repeatability assessed by the coefficient of variation was similar at baseline and after bronchodilator in asthmatics and in coughers (median 10% and 12%, respectively). There was no significant difference between asthmatics and coughers for both coefficient of repeatability (CR) (0.25 kPa L(-1)s and 32% of predicted vs 0.16 kPa L(-1) s and 21% of predicted, respectively) and BDR (median -14.7% vs -21.1% of predicted, respectively). However, in 20% of the study children, baseline variability of Rint modified the significance of the BDR.

CONCLUSION

In the present study, Rint short-term repeatability was similar to that of previous studies. Similar Rint repeatability in coughers and in asthmatic children favored the use of asthmatic CR for both populations, and a -35% cut-off as a positive BDR. In 20% of study children, baseline Rint variability could influence the significance of the BDR. In order to improve assessment of BDR using Rint, further studies are needed (1) to compare the variability of Rint to other resistance measurement techniques and (2) to define the best method for Rint calculation and for expression of BDR.

Endpoints for clinical trials in young children with cystic fibrosis

The availability of sensitive, reproducible, and feasible outcome measures for quantifying lung disease in children with cystic fibrosis (CF) younger than 6 years is critical to the conduct of clinical trials in this important population. Historically, identifying and quantifying the presence of lung disease in very young children with CF was hampered by a lack of reproducible measures of lung function or lung pathology. Over the past 10 years, significant progress has led to physiologic, anatomic, and bronchoscopic measures that may serve as endpoints for future intervention trials. These endpoints include infant and preschool lung function testing, computed tomography of the chest, and bronchoalveolar lavage markers of inflammation and infection. Much progress has occurred in standardizing lung function testing, which is essential for multicenter collaboration. Pulmonary exacerbation has the potential to serve as a clinical endpoint; however, there is currently no standardized definition in children with CF younger than 6 years. Further development of these outcomes measures will enable clinical trials in the youngest CF population with the objective of improving long-term prognosis.

RhDNase before airway clearance therapy improves airway patency in children with CF

INTRODUCTION

Little is known about the optimal timing of rhDNase nebulization in relation to airway clearance therapy (ACT).

OBJECTIVE

To compare the effects of rhDNase before ACT versus rhDNase after ACT in children with CF.

DESIGN

randomized, double blind, double dummy, cross over study.

INCLUSION CRITERIA

CF, stable clinical condition, rhDNase maintenance therapy. Children in Group I inhaled rhDNase 30 minutes before ACT, and placebo directly after ACT in week 1-3. The protocol was reversed during week 4-6. Group II performed the reversed sequence. Patients continued their daily routine ACT. Primary endpoint: MEF(25) %pred. Pulmonary functions tests were performed on days 0, 14, 21, 35 and 42. In weeks 3 and 6 children scored cough and sputum production on daily diary cards.

RESULTS

24 patients completed the study. Mean age = 12 years (range 7-19). Mean MEF(25) %pred was 5.8% higher after 3 weeks of rhDNase before ACT, compared to rhDNase after ACT (58.3% vs 52.5%, p=0.01). There were no significant differences for any of the other variables.

CONCLUSION

Inhalation of rhDNase before ACT improves peripheral airway patency in children with cystic fibrosis. Since all children were already on maintenance rhDNase therapy before the study, this effect is additional to any existing effect of regular rhDNase.

Reference values of Forced Expiratory Volumes and pulmonary flows in 3-6 year children: a cross-sectional study

BACKGROUND

The aims of this study were to verify the feasibility of respiratory function tests and to assess their validity in the diagnosis of respiratory disorders in young children.

METHODS

We performed spirometry and collected information on health and parents' lifestyle on a sample of 960 children aged 3-6.

RESULTS

The cooperation rate was 95.3%. Among the valid tests, 3 or more acceptable curves were present in 93% of cases. The variability was 5% within subjects in 90.8% of cases in all the parameters. We propose regression equations for FVC (Forced Vital Capacity), FEV1, FEV0.5, FEV0.75 (Forced Expiratory Volume in one second, in half a second and in 3/4 of a second), and for Maximum Expiratory Flows at different lung volume levels (MEF75, 50, 25). All parameters are consistent with the main reference values reported in literature. The discriminating ability of respiratory parameters versus symptoms always shows a high specificity (>95%) and a low sensitivity (<20%) with the highest OR (10.55; CI 95% 4.42-25.19) for MEF75. The ability of FEV0.75 to predict FEV1 was higher than that of FEV0.50: FEV0.75 predicts FEV1 with a determination coefficient of 0.95.

CONCLUSION

Our study confirms the feasibility of spirometry in young children; however some of the current standards are not well suited to this age group. Moreover, in this restricted age group the various reference values have similar behaviour.

Inhaled corticosteroids for recurrent respiratory symptoms in preschool children in general practice: randomized controlled trial

BACKGROUND

Therapy with inhaled corticosteroids (ICS) is beneficial in patients with asthma. However, in preschool children with symptoms like cough, wheeze, or shortness of breath diagnosing asthma is difficult. Therefore, the role of ICS in the management of preschool children with recurrent respiratory symptoms is unclear. We assessed the effectiveness of ICS in preschool children with recurrent respiratory symptoms in general practice.

METHODS

In this multicenter, randomized, double blind, placebo controlled trial, 96 children aged 1-5 years consulting their general practitioners for recurrent respiratory symptoms and in whom treatment with ICS was considered by the general practitioner were randomly allocated to receive ICS (fluticasone propionate 200 mcg/day by metered dose inhaler/spacer combination) or placebo for 6 months. Outcome assessments were carried out 1, 3, and 6 months after randomization. The primary outcome measure was the symptom score (cough, shortness of breath and wheeze during day and night) as measured by a symptom diary card. Secondary endpoints were symptom-free days, use of rescue medication, adverse events, and lung function variables as measured by the interrupter technique and forced oscillation technique.

RESULTS

During the 6 months treatment period, symptoms improved in both groups, with no differences between ICS and placebo. In addition, none of the secondary outcome parameters showed differences between both treatment groups.

CONCLUSION

ICS treatment has no beneficial effect in preschool children with recurrent respiratory symptoms in general practice. We therefore recommend a watchful waiting policy with only symptomatic treatment in these children. General practitioners and pediatricians should be aware of the high probability of overtreatment when prescribing ICS in these children.

Interrupter resistance: what's feasible?

Interrupter resistance (Rint) is one of the easiest ways to assess respiratory resistance during tidal breathing with minimal subject cooperation. This article enclosed current knowledge on technical and practical aspects such as how to measure Rint, and how to calculate Rint. Issues on repeatability of the technique and bronchial responsiveness are discussed. Recommendations on Rint technique are provided on behalf of the Interrupter Technique Subcommittee of the ATS/ERS Working Group on Infant and Young Children Pulmonary Function Testing.

A randomized, double-blind trial of the effect of anti-asthma treatment on lung function in children with asthma

BACKGROUND

Pulmonary function tests (PFTs) and especially spirometry measures are useful tools in evaluating early response to treatment of asthma in children mainly due to their worldwide availability. The aim of our study was to determine the effects of anti-asthma treatment in children, equally on FEV(1), FEF25-75%, R(int) and SR(aw) values.

METHODS

Children 6-18 years of age with moderate atopic asthma were randomized to 4-week, placebo-controlled, double-blind trial. Patients were randomly allocated to receive 200 microg budesonide (B) (n=29), 5 or 10 mg (according to age) montelukast (M) (n=29), 200 microg B + 5 or 10 mg M (n=29), 200 microg B + 9 microg formoterol (F) (n=29) or placebo (n=27). FEV(1,) FEF25-75%, R(int), SR(aw) were measured before and after treatment.

RESULTS

R(int), SR(aw), FEV(1) improved significantly in all active treatment groups while FEF25-75% improved significantly only in BM group and M group. Combination therapy, showed significantly greater effects on R(int) than monotherapy: BM group compared to B group (P=0.01) and M group (P=0.03) and BF group compared to B group (P=0.01) and M group (P=0.04).

CONCLUSION

This study shows that using single parameter for monitoring asthma can be misleading. Using combination of lung function techniques provides better assessment of treatment. Results of our study confirm this hypothesis. The best effect on large and small airways was achieved with combined anti-inflammatory therapy.