An official American Thoracic Society/European Respiratory Society statement: pulmonary function testing in preschool children

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.

Longitudinal lung function and structural changes in children with primary ciliary dyskinesia

BACKGROUND AND OBJECTIVES

Functional and structural lung evaluations are part of the follow-up of patients with primary ciliary dyskinesia (PCD). We aimed to evaluate transversal and longitudinal relationships between lung function test (LFT) and chest computed tomography (CT) in children with PCD, in stable clinical condition.

MATERIALS AND METHODS

Data from children followed in the French National Center were retrospectively collected. Inclusion criteria were (i) definitive diagnosis of PCD, (ii) age less than 15 years at the beginning of follow-up, (iii) at least 8 years of follow-up, (iv) at least two couples of concurrent CT and LFT available in a phase of clinical stability of the lung disease without modification of the treatment regimen in the last 4 weeks. Twenty children (median age at entry 4.6 years, median follow-up 15.4 years) were included. Concurrent LFT (blood gas and spirometry) and CT (score) results were recorded.

RESULTS

LFT indices (PaO(2) (n = 210), FVC, FEV(1) , FEF(2575%) (n = 195)) significantly decreased with age, and the mean annual decrease (z-score (% predicted)) was -0.17 (-0.49%), -0.09 (-0.50%), -0.10 (-0.89%), and -0.07 (-1.73%), respectively. First CT (median age 8.7 years) revealed bronchiectasis (70%), mucous plugging (70%), peribronchial thickening (90%), parenchymal abnormalities (65%), and hyperinflation (50%). CT scores (n = 74) significantly increased with age, and was negatively correlated to PaO(2), FVC, FEV(1), and FEF(2575%) longitudinal changes.

CONCLUSION

In stable clinical condition, functional, and structural progressive impairments significantly correlated in children with PCD. Further prospective studies, including large populations of patients with various levels of disease severity, are needed to confirm whether lung function follow-up can be used to adjust CT frequency and help at minimizing the radiation burden in children with a good life expectancy.

Early termination of exhalation: effect on spirometric parameters in healthy preschool children

OBJECTIVE

To evaluate the acceptability and reproducibility of spirometry in preschool children; to estimate the effect size of early termination of exhalation (ETE) on FVC, FEV(1) and FEV(0.5); and to evaluate the validity of FEV(0.5) in curves with ETE.

METHODS

Spirometric data were obtained from 240 healthy preschool children, who were selected by simple sampling. On the basis of the best curve from each child according to the end of exhalation, three groups were formed: no ETE (nETE); ETE and flow ≤ 10% of the highest PEF (ETE≤10); and ETE and flow > 10% of the highest PEF value (ETE>10). The reproducibility of FVC, FEV(1) and FEV(0.5) was compared among the three groups. The effect of ETE on FVC, FEV(1), and FEV(0.5) was assessed.

RESULTS

Of the 240 children tested, 112 (46.5%)-82 (34.0%) of those in the nETE group and 30 (12.5%) of those in the ETE≤10 group--had acceptable curves for all the parameters. In 64 (27.0%) of those in the ETE>10 group, the curves were acceptable only for FEV(0.5), increasing the proportion of children with valid FEV(0.5) to 73.0%. There were no significant differences between the nETE and ETE≤10 groups in terms of the mean values of the parameters assessed.

CONCLUSIONS

Maneuvers with ETE and flow ≤ 10% of the highest PEF are valid. In individuals with a flow > 10% of the highest PEF value, these maneuvers are only valid for FEV(0.5).

Feasibility and variability of measuring the Lung Clearance Index in a multi-center setting

The Lung Clearance Index (LCI) is superior to spirometry in detecting early lung disease in cystic fibrosis (CF) and correlates with structural lung changes seen on CT scans. The LCI has the potential to become a novel outcome parameter for clinical and research purposes. However longitudinal studies are required to further prove its prognostic value. Multi-center design is likely to facilitate realization of such studies. Therefore the aim of the present study was to assess multi-center feasibility and inter-center variability of LCI measurements in healthy children and adolescents. Comparative measurements were performed in unselected patients with CF to confirm previous single-center results. LCI measurements were performed in eight centers using the EasyOne Pro, MBW Module (ndd Medical Technologies, Zurich, Switzerland). The overall success rate for LCI measurements was 75.5%, leaving 102/151 measurements in healthy volunteers and 139/183 measurements in patients with CF for final analysis. Age ranged between 4 and 24 years. Mean LCI (range of means among centers) was 6.3 (6.0-6.5) in healthy volunteers and thus normal. Inter-center variability of center means was 2.9%, ANOVA including Schffé procedure demonstrated no significant inter-center differences (P > 0.05). Mean LCI (range of means among centers) was 8.2 (7.4-8.9) in CF and thus abnormal. Our study demonstrates good multi-center feasibility and low inter-center variability of the LCI in healthy volunteers when measured with the EasyOne Pro MBW module. Our data confirm published LCI data in CF. However, central coordination, quality control, regular training, and supervision during the entire study appear essential for successfully performing multi-center trials.

Farming environments and childhood atopy, wheeze, lung function, and exhaled nitric oxide

BACKGROUND

Previous studies have demonstrated that children raised on farms are protected from asthma and allergies. It is unknown whether the farming effect is solely mediated by atopy or also affects nonatopic wheeze phenotypes.

OBJECTIVE

We sought to study the farm effect on wheeze phenotypes and objective markers, such as lung function and exhaled nitric oxide, and their interrelation with atopy in children.

METHODS

The GABRIEL Advanced Studies are cross-sectional, multiphase, population-based surveys of the farm effect on asthma and allergic disease in children aged 6 to 12 years. Detailed data on wheeze, farming exposure, and IgE levels were collected from a random sample of 8023 children stratified for farm exposure. Of those, another random subsample of 858 children was invited for spirometry, including bronchodilator tests and exhaled nitric oxide measurements.

RESULTS

We found effects of exposure to farming environments on the prevalence and degree of atopy, on the prevalence of transient wheeze (adjusted odds ratio, 0.78; 95% CI, 0.64-0.96), and on the prevalence of current wheeze among nonatopic subjects (adjusted odds ratio, 0.45; 95% CI, 0.32-0.63). There was no farm effect on lung function and exhaled nitric oxide levels in the general study population.

CONCLUSIONS

Children living on farms are protected against wheeze independently of atopy. This farm effect is not attributable to improved airway size and lung mechanics. These findings imply as yet unknown protective mechanisms. They might include alterations of immune response and susceptibility to triggers of wheeze, such as viral infections.

Lung function distinguishes preschool children with CF from healthy controls in a multi-center setting

RATIONALE

Conducting clinical trials in cystic fibrosis (CF) preschoolers has been limited by lack of sensitive lung function measures performed across sites.

OBJECTIVES

(1) Assess feasibility and short-term reproducibility of spirometry, forced oscillometry (FO), and inductance plethysmography (IP) in a multi-center preschool population; (2) compare ability of each technique to differentiate lung function of CF preschoolers and controls; (3) evaluate longitudinal changes in lung function; (4) estimate sample sizes for future trials.

METHODS

A longitudinal, multi-center study of CF preschoolers was conducted utilizing standardized equipment, rigorous site training, and centralized lung function data review. CF subjects participated in up to four study visits 6 months apart, plus a 2-week reproducibility visit. Controls had one study visit.

RESULTS

Ninety-three CF subjects and 87 controls participated. Acceptability rates were lowest for spirometry (55%) and highest for IP (77%). Spirometry success increased with age and having a prior acceptable measurement. FEV(1) , FEV(0.5) , and FEF(25-75) were lower for CF subjects than for controls; spirometric z-scores declined with age. IP measures of thoracoabdominal asynchrony were greater for CF subjects than for controls. FO indices did not distinguish CF from controls. FEV(1) and FEV(0.5) are able to detect the smallest treatment effect for a given sample size.

CONCLUSIONS

Spirometry appears more sensitive than IP or FO for detecting lung disease in CF preschoolers; spirometric indices decline with age. Future trials using spirometry should include a run-in period for training and require acceptable data prior to enrollment. However, near-normal spirometric measurements in CF preschoolers may lead to difficulty detecting a treatment effect.

Analysis of the associations between lung function and clinical features in preschool children with cystic fibrosis

OBJECTIVE

To analyze cross-sectional and longitudinal associations between lung function measures and clinical features in a cohort of preschool children with cystic fibrosis (CF).

METHODS

Longitudinal eight-center observational study of children with CF aged 36-60 months at enrollment, who underwent semiannual pulmonary function tests (PFTs) for up to 2 years consisting of spirometry (all 8 sites), forced oscillometry (FO, 5 sites), and measures of thoracoabdominal asynchrony using respiratory inductive plethysmography (IP, 5 sites).

RESULTS

Ninety-three subjects were enrolled; 181 acceptable spirometry measurements from 71 subjects, 128 FO from 47 subjects, and 142 IP from 50 subjects were available for analysis. Cross sectional analyses did not detect an association between any PFT parameter at enrollment and Pseudomonas aeruginosa (Pa) status, CF gene mutation class, Wisconsin cough score, Shwachman score, environmental tobacco smoke exposure, family history of asthma, or nutritional indices. In longitudinal analyses, Pa infection within 6 months preceding enrollment was associated with a significantly greater rate of decline in z-scores for forced expiratory flow between 25 and 75% of forced vital capacity (FEF(25-75) ) (-1.3 vs. -0.4 Z scores/year, P = 0.024) and greater thoracoabdominal asynchrony measured by IP (mean phase angle difference 4.6°, P = 0.004). No other significant longitudinal associations were observed.

CONCLUSIONS

Prior Pa infection is associated with a greater rate of decline in FEF(25-75) z-score and mild thoracoabdominal asynchrony in preschool children with CF. In this multicenter US study, significant associations between other lung function measures and clinical features were not detected.

Salmeterol and fluticasone in young children with multiple-trigger wheeze

BACKGROUND

Treatment guidelines recommend using an inhaled corticosteroid (ICS) plus a long-acting β(2)-agonist (LABA) for childhood asthma when the symptoms are not controlled by ICS alone, but the appropriate use of LABAs in children continues to be debated.

OBJECTIVE

To compare the efficacy of an inhaled salmeterol and fluticasone propionate combination, 50/100 μg twice daily, with fluticasone propionate, 100 μg twice daily, or salmeterol, 50 μg twice daily, in children with multiple-trigger wheeze.

METHODS

A total of 105 children 4 to 7 years of age with multiple-trigger wheezing based on respiratory symptoms and bronchodilator responsiveness and/or exercise-induced bronchoconstriction without a viral cold were randomized to salmeterol-fluticasone, fluticasone propionate alone, or salmeterol alone via a metered-dose inhaler and a spacer device for 8 weeks. The primary efficacy outcome was exhaled nitric oxide level. Secondary outcomes were lung function measurements via impulse oscillometry, respiratory symptoms, and rescue medication use.

RESULTS

The exhaled nitric oxide levels decreased after all treatments, significantly more so after salmeterol-fluticasone and fluticasone than with salmeterol (adjusted geometric means at 8 weeks: salmeterol-fluticasone, 9.4 ppb; fluticasone, 9.3 ppb; salmeterol, 13.9 ppb; salmeterol-fluticasone vs salmeterol, P = .02; fluticasone vs salmeterol, P = .01). No treatment differences were found with respect to respiratory symptoms or median rescue use. Salmeterol-fluticasone resulted in a small but statistically significant improvement in baseline lung function compared with fluticasone. All treatments were equally well tolerated.

CONCLUSION

The effects of salmeterol-fluticasone and fluticasone were comparable, although lung function improvement was better with salmeterol-fluticasone than with fluticasone alone. There is no obvious benefit in initiation therapy with salmeterol-fluticasone rather than fluticasone alone in the treatment of steroid-naive children with multiple-trigger wheeze.

TRIAL REGISTRATION

Pathway of clinical trial registry of Helsinki University:http://www.hus.fi/?Path=1;28;2530;9899;9900;23618;23903;33578.

Elevated inflammatory markers at preschool age precede persistent wheezing at school age

BACKGROUND

  Wheeze is a heterogeneous symptom in preschool children. At preschool age it is hard to predict whether symptoms will pass or persist and develop into asthma. Our objective is to prospectively study whether inflammatory markers in exhaled breath condensate (EBC) and pre- and post-bronchodilator interrupter resistance (Rint) assessed at preschool age, are associated with wheezing phenotypes at school age.

METHODS

  Children (N = 230) were recruited from the Asthma DEtection and Monitoring (ADEM) study. At preschool age [mean (SE): 3.3 (0.1) yr], pre- and post-bronchodilator Rint was assessed. EBC was collected using a closed glass condenser. Inflammatory markers (IL-2, IL-4, IL-8, IL-10, sICAM) were measured using multiplex immunoassay. Wheezing phenotypes at 5 yr of age were determined based on longitudinal assessment. Children were classified as: never (N = 47), early-transient (N = 89) or persistent wheezers (N = 94).

RESULTS

  Persistent wheezers had elevated levels of all interleukins at preschool age compared to children who never wheezed (p < 0.05). EBC markers did not differ between the persistent and transient wheezers. There was no marked difference in Rint between wheezing phenotypes.

CONCLUSIONS

  We demonstrated that 5 yr old children with persistent wheeze already had elevated exhaled inflammatory markers at preschool age compared to never wheezers, indicating augmented airway inflammation in these children.

Comparison of online single-breath vs. online multiple-breath exhaled nitric oxide in school-age children

INTRODUCTION

Standards for online multiple-breath (mb) exhaled nitric oxide (eNO) measurements and studies comparing them with online single-breath (sb) eNO measurements are lacking, although eNOmb requires less cooperation in children at school age or younger.

METHODS

Online eNOmb and eNOsb were measured in 99 healthy children and (in order to observe higher values) in 21 children with suspected asthma at a median age of 6.1 and 11.7 y, respectively. For eNOmb, we aimed for 20 tidal breathing maneuvers; eNOsb was measured according to standards. The two techniques were compared by standard methods after computing NO output or extrapolating eNOmb to the standard flow of 50 ml/s (eNOmb(50)).

RESULTS

Measurements were acceptable in 82 (eNOmb) and 81 (eNOsb) children. Paired data were available for 65 children. On a log-log scale, eNOmb(50) (geometric mean ± SD 13.1 ± 15.5 parts per billion, ppb) was correlated with eNOsb (12.5 ± 15.8 ppb), with r(2) = 0.87. The mean difference between eNOsb and eNOmb(50) was -0.7 ppb, with limits of agreement (LOAs) of 4.0 and -5.3 ppb.

DISCUSSION

Despite its correlation with eNOsb, the LOA range hampers eNOmb use in research, where exact values across the whole range are warranted. However, eNOmb might be an alternative tool especially at preschool age, when cooperation during measurements is crucial.

Domestic airborne black carbon and exhaled nitric oxide in children in NYC

Differential exposure to combustion by-products and allergens may partially explain the marked disparity in asthma prevalence (3-18%) among New York City neighborhoods. Subclinical changes in airway inflammation can be measured by fractional exhaled nitric oxide (FeNO). FeNO could be used to test independent effects of these environmental exposures on airway inflammation. Seven- and eight-year-old children from neighborhoods with lower (range 3-9%, n=119) and higher (range 11-18%, n=121) asthma prevalence participated in an asthma case-control study. During home visits, FeNO was measured, and samples of bed dust (allergens) and air (black carbon; BC) were collected. Neighborhood built-environment characteristics were assessed for the 500 m surrounding participants' homes. Airborne BC concentrations in homes correlated with neighborhood asthma prevalence (P<0.001) and neighborhood densities of truck routes (P<0.001) and buildings burning residual oil (P<0.001). FeNO concentrations were higher among asthmatics with than in those without frequent wheeze (≥4 times/year) (P=0.002). FeNO concentrations correlated with domestic BC among children without seroatopy (P=0.012) and with dust mite allergen among children with seroatopy (P=0.020). The association between airborne BC in homes and both neighborhood asthma prevalence and FeNO suggest that further public health interventions on truck emissions standards and residual oil use are warranted.

Genetic variation in vascular endothelial growth factor-a and lung function

RATIONALE

Given the role of vascular endothelial growth factor (VEGF) in lung development, we hypothesized that polymorphisms in VEGF-A may be associated with lung function.

OBJECTIVES

The current study was designed to assess the role of genetic variants in VEGF-A as determinants of airway function from infancy through early adulthood.

METHODS

Association between five single-nucleotide polymorphisms (SNPs) in VEGF-A and lung function were assessed longitudinally in two unselected birth cohorts and cross-sectionally among infants. Replication with two SNPs was conducted in adults and children with asthma. We investigated the functionality of the SNP most consistently associated with lung function (rs3025028) using Western blotting to measure the ratio of plasma VEGF-A(165b)/panVEGF-A(165) among homozygotes.

MEASUREMENTS AND MAIN RESULTS

In two populations in infancy, C-allele homozygotes of rs3025028 had significantly higher VmaxFRC, forced expiratory flow(50), and forced expiratory flow(25-75) compared with other genotype groups. Among preschool children (age 3 yr), C allele of rs3025028 was associated with significantly higher specific airway conductance, with similar findings observed for lung function in school-age children. For FEV(1)/FVC ratio similar findings were observed among adolescents and young adults (birth cohort), and then replicated in adults and schoolchildren with asthma (cross-sectional studies). For rs3025038, plasma VEGF-A(165b)/panVEGF-A(165) was significantly higher among CC versus GG homozygotes (P ≤ 0.02) at birth, in school-age children, and in adults.

CONCLUSIONS

We report significant associations between VEGF-A SNP rs3025028 and parameters of airway function measured throughout childhood, with the effect persisting into adulthood. We propose that the mechanism may be mediated through the ratios of active and inhibitory isoforms of VEGF-A(165), which may be determined by alternative splicing.

Pulmonary function testing in young children

Pulmonary function testing (PFT) is of great importance in the evaluation and treatment of respiratory diseases. Spirometry is simple, noninvasive, and has been the most commonly used technique in cooperative children, obtaining reliable data in only a few minutes. The development of commercially available equipment as well as the simplification of previous techniques that now require minimal patient cooperation applied during tidal breathing have significantly stimulated the use of PFT in younger children. Tidal breathing techniques such as impulse oscillometry, gas dilution, and plethysmography have permitted previously unobtainable PFT in children 2 to 5 years of age. The purpose of this review is to help clinicians become familiar with available PFT techniques used in young children by discussing their general principles, clinical applications, and limitations.

[Bronchiolitis obliterans: outcome in the medium term]

BACKGROUND

Bronchiolitis obliterans is a chronic obstructive lung disease that follows a severe insult to the lower respiratory tract. Severity and outcome are different depending on the geographic area. The aim of this study was to communicate the results of our sample.

METHODS

A retrospective study was performed in a sample of boys and girls with a medical diagnosis of bronchiolitis obliterans (BO) between December 1994 and February 2011. The diagnosis was made by high-resolution computed tomography (HRCT) scan and lung function. Lung biopsy was performed in one case. Pulmonary function testing included; forced spirometry (≥ 3 years old), plethysmography (≥ 5 years), bronchodilator tests (BDT), single-breath determination of carbon monoxide uptake in the lung (D(LCO)) (≥ 6 years) and measurement of exhaled lower respiratory nitric oxide (FE(NO)). Quantitative variables were; age at diagnosis, respiratory morbidity before the diagnosis, time from the start of the symptomatology until the diagnosis, follow-up time, respiratory morbidity after the diagnosis, airway specific resistance (sR(eff)), airway specific conductance (sG(eff)), residual volume, total lung capacity, thoracic gas volume, FEV(1), FVC, FEV(1)/FVC, FEF(25-75), D(LCO) and FE(NO). Qualitative variables were; sex, reason for consulting, viral infections, atopy, smoke exposure, HRCT scan and current treatment. Descriptive analysis was performed and pulmonary function before and after BDT was studied using paired-sample Wilcoxon and Student́s t-test.

RESULTS

We studied a cohort of 22 cases, 10 (45.4%) boys and 12 (54.5%) girls. The mean age at the diagnosis was 4.87 ± 3, 27 years old. The follow-up period was 5 years (range 1 to 8 years). Related virus were; influenza 2 (9.09%), parainfluenza 2 (9.09%), adenovirus 3 (13.69%), syncytial respiratory virus 1 (4.5%) and rhinovirus 1 (4.54%). HRCT scan: mosaic pattern of lung attenuation 22 (100%) and bronchiectasis 8 (36.36%). Lung function at diagnosis showed fixed airflow obstruction and increased lung volumes. The global analysis showed a progressive decrease in FEV(1), FVC, FVC/FEV(1,) FEF(25-75) and increase in sR(eff) and residual volume with decrease in sG(eff). Individually, there was a tendency to stabilise the lung function comparing with initial values at diagnosis. Respiratory morbidity was low after the diagnosis.

CONCLUSIONS

In most cases, fixed air-flow obstruction and lung function stability with low respiratory morbidity were observed. HRCT scan and lung function testing supported the diagnosis.

Lung function in children born after foetal growth restriction and very preterm birth

AIMS

To assess lung function at early school age in children delivered at very early gestation owing to intrauterine growth restriction and abnormal foetal blood flow (IUGR).

METHODS

Spirometry was performed at median age 8.4 (range 6.5-10.7) years in 31 children born preterm with IUGR (PT-IUGR) with a median (range) birth weight (BW) of 650 (395-976) g and median (range) gestational age 27 (24-29) weeks. Control groups were matched for gender and age and had BW appropriate for gestational age (AGA); 31 children born preterm (PT-AGA) with BW of 1010 (660-1790) g matched for gestational age at birth, and 31 children born at term (T-AGA) with BW of 3530 (3000-4390) g.

RESULTS

The PT-IUGR group had lower mean (SD) values of z-scores for FEV(1), FEV(1)/FVC and forced mid-expiratory flow rate (FEF(25-75%)) compared to the T-AGA group, p = 0.003, p = 0.032 and p < 0.001, respectively, but did not differ from the PT-AGA group. PT-IUGR children delivered at ≥26 gestational weeks (GW) had lower FEF(25-75%) than PT-AGA children of corresponding GA, p = 0.014.

CONCLUSION

Lung function was reduced in the PT-IUGR group at early school age compared to controls born at term. The influence of IUGR on later lung function was only apparent in children born preterm after 26 GW.

Clinical investigation of respiratory system admittance in preschool children

INTRODUCTION

The upper airway shunt attenuates measurements of respiratory system impedance (Zrs), with greater impact in young children. Changes in respiratory system admittance, Ars (or Zrs(-1)), are theoretically independent of the shunt. This study compared the ability of Ars, to standard oscillatory outcomes, to determine respiratory disease and differentiate responses to inhaled bronchial challenges in the clinical setting.

METHODS

The forced oscillation technique (FOT) was used to establish reference equations for Ars in healthy preschool children, compare the change in Ars to standard oscillatory outcomes during bronchial challenge with inhaled adenosine-5'-monophosphate (AMP) and to inhaled bronchodilator in healthy children and those with respiratory disease.

RESULTS

Children with respiratory disease had lower baseline Ars than healthy children (P < 0.05). However, there was no improved ability for Ars to differentiate between bronchodilator responses in healthy and disease populations. In contrast, the response to inhaled AMP occurred at a lower concentration, [25 (3.12-400) mg ml(-1); median (10th-90th centile)], as measured by Ars when compared to respiratory system resistance [225 (6.25-400) mg ml(-1); P = 0.016].

CONCLUSION

This study supports the use of Ars during inhaled challenges, but not in response to bronchodilation.

A study of the use of impulse oscillometry in the evaluation of children with asthma: analysis of lung parameters, order effect, and utility compared with spirometry

BACKGROUND

The ability to objectively measure lung function in children is critical in the assessment and treatment of asthma in this age group. We thus determined the effectiveness of impulse oscillometry (IOS) as a non-invasive technique to assess lung function in children and in comparison to spirometry for sensitivity and specificity, testing variability, and the order effect of sequential testing of IOS and spirometry.

METHODS

One hundred seventeen children sequentially evaluated in a pediatric clinic and under medical care for disease, were asked to perform IOS and spirometry. The utility of IOS and spirometry in differentiating children that had asthma versus those children who did not was then analyzed.

RESULTS

In the primary analysis (n = 117), bronchodilator response using IOS distinguished asthmatics from non-asthmatics, P = 0.0008 for R10. Receiver-operator characteristic curve (ROC) analysis of R10 bronchodilator response at the best cut-off (-8.6% change) correctly identified 77% of patients with asthma and excluded 76% of non-asthmatics. Amongst those children able to perform spirometry (asthmatics, n = 66; non-asthmatics, n = 16), FEV(1) did not reveal a difference between these two groups, while area of reactance (AX) did distinguish these groups (P = 0.0092). Sequential testing of IOS and then spirometry (n = 47) showed a significant decrement in lung function as determined by IOS following performance of spirometry (P = 0.0309).

CONCLUSION

In the diagnosis and management of children with lung disease, IOS is a non-invasive approach that easily and objectively measures lung impedance and should be considered as both an adjunct, and in some situations, an alternative to standard spirometry.

The multiple meanings of "wheezing": a questionnaire survey in Portuguese for parents and health professionals

Background

Most epidemiological studies on pediatric asthma rely on the report of "wheezing" in questionnaires. Our aim was to investigate the understanding of this term by parents and health professionals.

Methods

A cross-sectional survey was carried out in hospital and community settings within the south of Portugal. Parents or caregivers self-completed a written questionnaire with information on social characteristics and respiratory history. Multiple choice questions assessed their understanding of "wheezing". Health professionals (physicians, nurses and physiotherapists) were given an adapted version. We used bivariate analysis and multivariate models to study associations between definitions of "wheezing" and participants' characteristics.

Results

Questionnaires from 425 parents and 299 health professionals were included. The term "wheezing" was not recognized by 34% of parents, more frequently those who were younger (OR 0.4 per 10-year increment, 95% CI 0.3-0.7), had lower education (OR 3.3, 95% CI 1.5-7.4), and whose children had no history of respiratory disease (OR 4.6, 95% CI 2.5-8.7) (all ORs adjusted). 31% of parents familiar with "wheezing" either did not identify it as a sound, or did not locate it to the chest, while tactile (40%) and visual (34%) cues to identify "wheezing" were frequently used. Nurses reported using visual stimuli and overall assessments more often than physicians (p < 0.01). The geographical location was independently associated with how parents recognized and described "wheezing".

Conclusions

Different meanings for "wheezing" are recognized in Portuguese language and may be influenced by education, respiratory history and regional terminology. These findings are likely applicable to other non-English languages, and suggest the need for more accurate questionnaires and additional objective measurement instruments to study the epidemiology of wheezing disorders.

Cutting edge technologies in respiratory research: lung function testing

Pulmonary function testing is part of routine clinical practice in respiratory medicine. It is based around spirometry, which will remain the central measurement of lung function given its prognostic significance and its integral role in defining severity of airways disease. However, there is an increasing body of evidence from studies using new methods of lung function measurement which are providing new insights into pathophysiology of disease. This body of data is forming a basis for their future clinical role, once the economics of producing the relevant devices becomes attractive. The forced oscillation technique and multiple breath nitrogen washout are currently the most commonly used of the newer lung function techniques, which are refinements of long-established techniques. Optical coherence tomography, optical reflection, electrical impedance and vibration response imaging have arisen by development of novel devices. The recent use of these techniques is reviewed.

Lung clearance index: clinical and research applications in children

Multiple breath washout (MBW) has been demonstrated to be sensitive for assessing ventilation inhomogeneity (VI). VI is supposed to reflect changes in peripheral airways which are not apparent using spirometry. The lung clearance index (LCI) is the most robust parameter to quantify VI, and is largely independent of age; therefore, it potentially qualifies as a surrogate outcome parameter for clinical and research purposes, particularly during childhood. This review summarizes the current evidence regarding the clinical value of measuring LCI in children. Feasibility, reproducibility and diagnostic accuracy have been demonstrated; available data confirm that LCI is superior to spirometry in detecting small air way disease. However, there is little information regarding the value in the individual patient, and sparse longitudinal data looking at its prognostic value. Currently, only in patients with Cystic Fibrosis, it appears likely that knowledge of LCI will be useful for routine clinical management.

Equações preditivas e valores de normalidade para pressões respiratórias máximas na infância e adolescência

OBJETIVO: Pesquisar equações preditivas e valores de normalidade para pressões respiratórias máximas disponíveis na literatura para a faixa etária compreendida entre a infância e a adolescência. FONTES DE DADOS: Estudos publicados em inglês e em português no período entre 1980 e 2009. As bases de dados eletrônicas Lilacs e Medline foram consultadas utilizando-se as palavras-chave "capacidade respiratória máxima", "músculos respiratórios", "valores de referência", "adolescente" e "criança". SÍNTESE DOS DADOS: Foram incluídos oito artigos na revisão, totalizando 1.463 crianças e adolescentes avaliados. A faixa etária da população estudada variou de sete a 18 anos. Geralmente o indivíduo é avaliado na posição sentada e com um clipe nasal. Os esforços máximos são realizados a partir do volume residual e da capacidade pulmonar total e sustentados por um a três segundos. Valores de normalidade e equações de predição foram propostos em oito e dois estudos, respectivamente. Nestes, demonstra-se incremento nas pressões respiratórias máximas desde a infância à adolescência e a ocorrência de maiores valores de pressão expiratória máxima quando comparados à pressão inspiratória máxima em crianças e adolescentes de ambos os sexos. CONCLUSÕES: As pressões respiratórias máximas constituem um meio efetivo para avaliar a força muscular respiratória e diversos fatores contribuem para a grande variedade de equações preditivas e de valores de normalidade disponíveis. É preciso buscar um consenso para normatizar os métodos requeridos ao avaliar a força muscular respiratória em crianças e adolescentes.

Decreased lung function after preschool wheezing rhinovirus illnesses in children at risk to develop asthma

Background

Preschool rhinovirus (RV) wheezing illnesses predict an increased risk of childhood asthma; however, it is not clear how specific viral illnesses in early life relate to lung function later on in childhood.

Objective

To determine the relationship of virus-specific wheezing illnesses and lung function in a longitudinal cohort of children at risk for asthma.

Methods

Two hundred thirty-eight children were followed prospectively from birth to 8 years of age. Early life viral wheezing respiratory illnesses were assessed by using standard techniques, and lung function was assessed annually by using spirometry and impulse oscillometry. The relationships of these virus-specific wheezing illnesses and lung function were assessed by using mixed-effect linear regression.

Results

Children with RV wheezing illness demonstrated significantly decreased spirometry values, FEV₁ (P = .001), FEV_0.5 (P < .001), FEF_25-75 (P < .001), and also had abnormal impulse oscillometry measures—more negative reactance at 5 Hz (P < .001)—compared with those who did not wheeze with RV. Children who wheezed with respiratory syncytial virus or other viral illnesses did not have any significant differences in spirometric or impulse oscillometry indices when compared with children who did not. Children diagnosed with asthma at ages 6 or 8 years had significantly decreased FEF_25-75 (P = .05) compared with children without asthma.

Conclusion

Among outpatient viral wheezing illnesses in early childhood, those caused by RV infections are the most significant predictors of decreased lung function up to age 8 years in a high-risk birth cohort. Whether low lung function is a cause and/or effect of RV wheezing illnesses is yet to be determined.

Update of respiratory tract disease in children with primary ciliary dyskinesia

Primary ciliary dyskinesia (PCD) is a rare genetic disease characterized by abnormal ciliary structure and function leading to impaired mucociliary clearance and chronic progressive sinopulmonary disease. Upper and lower respiratory tract manifestations are cardinal features of PCD. This review summarizes the current state of knowledge of respiratory tract disease in individuals with PCD and highlights the challenges in identifying and quantifying lung disease in very young children with PCD. No specific therapies are available to correct ciliary dysfunction in PCD. Treatment is not evidence based, and recommendations are largely extrapolated from cystic fibrosis and other conditions with impaired mucociliary clearance. There is a pressing need to develop and validate outcome measures, including patient-reported outcomes, that could be used to evaluate potential therapies in PCD. This review concludes with recommendations for clinical endpoints and outcome measures and a prioritized list of treatments to study in PCD clinical trials.

The GABRIEL Advanced Surveys: study design, participation and evaluation of bias

Exposure to farming environments has been shown to protect substantially against asthma and atopic disease across Europe and in other parts of the world. The GABRIEL Advanced Surveys (GABRIELA) were conducted to determine factors in farming environments which are fundamental to protecting against asthma and atopic disease. The GABRIEL Advanced Surveys have a multi-phase stratified design. In a first-screening phase, a comprehensive population-based survey was conducted to assess the prevalence of exposure to farming environments and of asthma and atopic diseases (n = 103,219). The second phase was designed to ascertain detailed exposure to farming environments and to collect biomaterial and environmental samples in a stratified random sample of phase 1 participants (n = 15,255). A third phase was carried out in a further stratified sample only in Bavaria, southern Germany, aiming at in-depth respiratory disease and exposure assessment including extensive environmental sampling (n = 895). Participation rates in phase 1 were around 60% but only about half of the participating study population consented to further study modules in phase 2. We found that consenting behaviour was related to familial allergies, high parental education, wheeze, doctor diagnosed asthma and rhinoconjunctivitis, and to a lesser extent to exposure to farming environments. The association of exposure to farm environments with asthma or rhinoconjunctivitis was not biased by participation or consenting behaviour. The GABRIEL Advanced Surveys are one of the largest studies to shed light on the protective 'farm effect' on asthma and atopic disease. Bias with regard to the main study question was able to be ruled out by representativeness and high participation rates in phases 2 and 3. The GABRIEL Advanced Surveys have created extensive collections of questionnaire data, biomaterial and environmental samples promising new insights into this area of research.

Comparative efficacy and safety of 4 randomized regimens to treat early Pseudomonas aeruginosa infection in children with cystic fibrosis

OBJECTIVE

To investigate the efficacy and safety of 4 antipseudomonal treatments in children with cystic fibrosis with recently acquired Pseudomonas aeruginosa infection.

DESIGN

Randomized controlled trial.

SETTING

Multicenter trial in the United States.

PARTICIPANTS

Three hundred four children with cystic fibrosis aged 1 to 12 years within 6 months of P aeruginosa detection.

INTERVENTIONS

Participants were randomized to 1 of 4 antibiotic regimens for 18 months (six 12-week quarters) between December 2004 and June 2009. Participants randomized to cycled therapy received tobramycin inhalation solution (300 mg twice a day) for 28 days, with oral ciprofloxacin (15-20 mg/kg twice a day) or oral placebo for 14 days every quarter, while participants randomized to culture-based therapy received the same treatments only during quarters with positive P aeruginosa cultures.

MAIN OUTCOME MEASURES

The primary end points were time to pulmonary exacerbation requiring intravenous antibiotics and proportion of P aeruginosa -positive cultures.

RESULTS

The intention-to-treat analysis included 304 participants. There was no interaction between treatments. There were no statistically significant differences in exacerbation rates between cycled and culture-based groups (hazard ratio, 0.95; 95% confidence interval [CI], 0.54-1.66) or ciprofloxacin and placebo (hazard ratio, 1.45; 95% CI, 0.82-2.54). The odds ratios of P aeruginosa- positive culture comparing the cycled vs culture-based group were 0.78 (95% CI, 0.49-1.23) and 1.10 (95% CI, 0.71-1.71) comparing ciprofloxacin vs placebo. Adverse events were similar across groups.

CONCLUSIONS

No difference in the rate of exacerbation or prevalence of P aeruginosa positivity was detected between cycled and culture-based therapies. Adding ciprofloxacin produced no benefits.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00097773.

Use of specific airway resistance to assess bronchodilator response in children

BACKGROUND AND OBJECTIVE

Changes in specific airway resistance (ΔsRaw) after bronchodilation, as measured by plethysmography and FEV(1) , are frequently considered to be interchangeable indices of airway obstruction. However, the baseline relationship between these two indices is weak, and the value of ΔsRaw that best predicts FEV(1) reversibility in children has yet to be determined. The aim of this study was (i) to establish the sRaw cut-off value that best distinguishes between positive and negative bronchodilator responses, as measured by FEV(1) reversibility; (ii) to determine whether the discrepancy between ΔsRaw and ΔFEV(1) might be explained by independent correlations between ΔFEV(1) and both ΔsRaw (mainly airway obstruction) and ΔFVC (airway closure); and (iii) to assess the effect of height and age on the relationship between ΔsRaw and ΔFEV(1) .

METHODS

A retrospective study was performed in 481 children (median age 10.5years, range 6.1-17.6) with actual or suspected asthma, for whom sRaw and spirometry data were obtained at baseline and after administration of a bronchodilator.

RESULTS

The sRaw cut-off value that best predicted FEV(1) reversibility was a 42% decrease from baseline (P=0.0001, area under the curve 0.70, sensitivity 55%, specificity 77%) and was independent of height and age. Changes in FEV(1) were significantly but independently related to ΔsRaw and ΔFVC (index of air trapping) (r=0.40, P<0.0001 and r=0.39, P<0.0001, respectively).

CONCLUSIONS

A 42% decrease in sRaw predicted FEV(1) reversibility reasonably well, whereas a smaller decrease in sRaw failed to detect approximately one out of two positive responses detected by FEV(1) , with no influence of height or age.

Impulse oscillometry in preschool children and association with body mass index

BACKGROUND AND OBJECTIVE

The use of the impulse oscillometry system (IOS) allows differentiated lung function testing with a minimum of cooperation at normal tidal breathing. The aim of this cross-sectional study was to assess the association of body mass (overweight and obese) with oscillometric parameters in preschool children.

METHODS

A preschool medical check of 518 children (age 6.01 ± 0.25 years) included IOS recordings of airway resistance and lung reactance (MasterScreen IOS, CareFusion, Höchberg, Germany). Measured values of respiratory resistance (R5) and reactance (X5) at 5 Hz were correlated with BMI. In addition, data were compared with recently published reference equations.

RESULTS

In this young age group of 241 boys and 277 girls there was no significant association between oscillometric parameters and BMI. When compared with current IOS reference values of healthy subjects the relationship of R5 (109 ± 25%) and X5 (105.5 ± 35%) suggested mildly elevated peripheral resistance in this unselected group of preschool children.

CONCLUSIONS

IOS is ideally suited to obtain measurements of respiratory function in preschool children. At the age of 6 years, standard oscillometric values do not indicate impaired respiratory function associated with increased BMI.

Time lag between oscillatory pressure and flow affecting accuracy of forced oscillation technique

Background

The forced oscillation technique (FOT) is a simple method for assessing the oscillatory mechanics of the respiratory system. The oscillatory properties, respiratory system resistance (Rrs) and reactance (Xrs), are calculated from the oscillatory pressure/flow relationship. Although the FOT has been a well-established technique, some detailed experimental conditions would be different among institutions.

Methods

We evaluated whether time lags produced by the experimental conditions such as different positions of the sensors can affect the accuracy of the FOT. If the position of the pressure sensor is different from the flow sensor, a time lag may occur in the measurements. The effect of the time lag was studied by numerical analysis.

Results

Rrs was estimated to be increased and Xrs decreased with an increase in the time lag, especially at a high oscillatory frequency of the medium-frequency range (5-35 Hz). At the high-frequency range (10-500 Hz), Rrs and Xrs were strikingly different in the values of the time lag.

Conclusion

A time lag between the oscillatory pressure and flow may be involved in the accuracy of the FOT, suggesting that it needs to be minimized or compensated for with signal processing. Researchers should pay attention to such detailed experimental conditions of the FOT apparatus.

Resonant frequency does not predict high-frequency chest compression settings that maximize airflow or volume

High-frequency chest compression (HFCC) is a therapy for cystic fibrosis (CF). We hypothesized that the resonant frequency (f(res)), as measured by impulse oscillometry, could be used to determine what HFCC vest settings produce maximal airflow or volume in pediatric CF patients. In 45 subjects, we studied: f(res), HFCC vest frequencies that subjects used (f(used)), and the HFCC vest frequencies that generated the greatest volume (f(vol)) and airflow (f(flow)) changes as measured by pneumotachometer. Median f(used) for 32 subjects was 14 Hz (range, 6-30). The rank order of the three most common f(used) was 15 Hz (28%) and 12 Hz (21%); three frequencies tied for third: 10, 11, and 14 Hz (5% each). Median f(res) for 43 subjects was 20.30 Hz (range, 7.85-33.65). Nineteen subjects underwent vest-tuning to determine f(vol) and f(flow). Median f(vol) was 8 Hz (range, 6-30). The rank order of the three most common f(vol) was: 8 Hz (42%), 6 Hz (32%), and 10 Hz (21%). Median f(flow) was 26 Hz (range, 8-30). The rank order of the three most common f(flow) was: 30 Hz (26%) and 28 Hz (21%); three frequencies tied for third: 8, 14, and 18 Hz (11% each). There was no correlation between f(used) and f(flow) (r(2)  = -0.12) or f(vol) (r(2) = 0.031). There was no correlation between f(res) and f(flow) (r(2)  = 0.19) or f(vol) (r(2) = 0.023). Multivariable analysis showed no independent variables were predictive of f(flow) or f(vol). Vest-tuning may be required to optimize clinical utility of HFCC. Multiple HFCC frequencies may need to be used to incorporate f(flow) and f(vol).

Appropriate Pediatric Spirometry Reference Equations and Interpretation

Spirometry is an important tool in the diagnosis and management of pediatric pulmonary diseases. Reference equations enable the comparison of an individual's lung function to that of a healthy reference population of the same age, sex, height, and race/ethnicity. This comparison is important both in distinguishing health from disease and in monitoring the lung function of a growing child over time. A range of reference equations exist, and no single equation is ideal for all situations. However, there are important considerations to understand when choosing an equation. This article reviews how reference equations are created, how to use them to interpret lung function measurements, and how to choose appropriate reference equations, highlights current limitations, and suggests areas for future research and collaboration.

Relation between partial and raised volume forced expiratory flows in sick infants

RATIONALE

The maximal expiratory flow-volume (MEFV) and the partial expiratory flow-volume (PEFV) maneuvers are interchangeably performed when testing infant lung function. In recent years, the MEFV has gained popularity over the PEFV as it offers the investigator various forced expiratory flow and volume variables in addition to the sole, maximal flow at functional residual capacity (Vmax FRC) available from the PEFV maneuver. Both types of measure are considered to provide information on airway function.

OBJECTIVES

To compare Vmax FRC values by PEFV to flows at low lung volumes by MEFV in infants suffering from a variety of illnesses.

METHODS

Retrospective analysis of records of 175 infants attending a tertiary out-patient clinic (age range 2-234 weeks). Comparisons between parameters derived from the PEFV and MEFV curves were made by linear regression and by Bland-Altman plots.

MEASUREMENTS AND MAIN RESULTS

Vmax FRC highly correlated with forced expiratory flows at 85% of forced vital capacity (FEF85; r = 0.87, P < 0.0001) with a mean bias of 20 ml/sec, and at 75% (FEF75; r = 0.83, P < 0.0001) with a greater mean bias of -72 ml/sec, but less with forced expired volume in 0.5 sec (FEV0.5; r = 0.66, P < 0.0001) showing a much wider scatter especially in infants with more severe obstruction. Same agreement between Vmax FRC and FEF85 or FEF75 was seen when presented as z-scores (r = 0.77 and 0.76; respectively).

CONCLUSIONS

Regardless of the maneuver performed, PEFV or MEFV, Vmax FRC and FEF85, and FEF75 show high agreement in sick infants. As they both describe small airways function, both maneuvers may be interchangeable.

Reference values for paediatric pulmonary function testing: The Utrecht dataset

BACKGROUND

Since populations evolve, measurement protocols and equipment improve and analysis techniques progress, there is an ongoing need to reassess reference data for pulmonary function tests. Furthermore, reference values for total lung capacity and carbon monoxide diffusion capacity are scarcely available in children. We aimed to provide updated reference equations for most commonly used pulmonary function indices in Caucasian children.

METHODS

In the 'Utrecht Pulmonary Function Reference Data Study' we collected data in Caucasian children aged 2-18 years. We analyzed them using the 'Generalized Additive Models for Location Scale and Shape' (GAMLSS) statistical method.

RESULTS

Measurements of interrupter resistance (R(int)) (n = 877), spirometry (n = 1042), body plethysmography (n = 723) and carbon monoxide diffusion/helium dilution (n = 543) were obtained in healthy children. Height (or the natural logarithm of height) and age (or the natural logarithm of age) were both significantly related to most outcome measures. Also sex was a significant determinant, except for RV, RV/TLC, FRC(pleth), Raw(0,5), Raw(tot), R(int) and FEF values. The application of previously published reference equations on the study population resulted in misinterpretation of pulmonary function.

CONCLUSION

These new paediatric reference equations provide accurate estimates of the range of normality for most commonly used pulmonary function indices, resulting in less underdiagnosis and overdiagnosis of pulmonary diseases.

Analysis of impulse oscillometric measures of lung function and respiratory system model parameters in small airway-impaired and healthy children over a 2-year period

BACKGROUND

Is Impulse Oscillometry System (IOS) a valuable tool to measure respiratory system function in Children? Asthma (A) is the most prevalent chronic respiratory disease in children. Therefore, early and accurate assessment of respiratory function is of tremendous clinical interest in diagnosis, monitoring and treatment of respiratory conditions in this subpopulation. IOS has been successfully used to measure lung function in children with a high degree of sensitivity and specificity to small airway impairments (SAI) and asthma. IOS measures of airway function and equivalent electrical circuit models of the human respiratory system have been developed to quantify the severity of these conditions. Previously, we have evaluated several known respiratory models based on the Mead's model and more parsimonious versions based on fitting IOS data known as extended RIC (eRIC) and augmented RIC (aRIC) models have emerged, which offer advantages over earlier models.

METHODS

IOS data from twenty-six children were collected and compared during pre-bronchodilation (pre-B) and post- bronchodilation (post-B) conditions over a period of 2 years.

RESULTS AND DISCUSSION

Are the IOS and model parameters capable of differentiating between healthy children and children with respiratory system distress? Children were classified into two main categories: Healthy (H) and Small Airway-Impaired (SAI). The IOS measures and respiratory model parameters analyzed differed consistently between H and SAI children. SAI children showed smaller trend of "growth" and larger trend of bronchodilator responses than H children.The two model parameters: peripheral compliance (Cp) and peripheral resistance (Rp) tracked IOS indices of small airway function well. Cp was a more sensitive index than Rp. Both eRIC and aRIC Cps and the IOS Reactance Area, AX, (also known as the "Goldman Triangle") showed good correlations.

CONCLUSIONS

What are the most useful IOS and model parameters? In this work we demonstrate that IOS parameters such as resistance at 5 Hz (R5), frequency-dependence of resistance (fdR: R5-R20), reactance area (AX), and parameter estimates of respiratory system such as Cp and Rp provide sensitive indicators of lung function and have the capacity to differentiate between obstructed and non-obstructed airway conditions. They are also capable of demonstrating airway growth-related changes over a two-year period. We conclude that the IOS parameters AX and the eRIC model derived parameter Cp are the most reliable parameters to track lung function in children before and after bronchodilator and over a time period (2 years). Which model is more suitable for interpreting IOS data? IOS data are equally well-modelled by eRIC and aRIC models, based on the close correlations of their corresponding parameters - excluding upper airway shunt compliance. The eRIC model is a more parsimonious and equally powerful model in capturing the differences in IOS indices between SAI and H children. Therefore, it may be considered a clinically-preferred model of lung function.

Impulse oscillometry in the evaluation of diseases of the airways in children

OBJECTIVE

To provide an overview of impulse oscillometry and its application to the evaluation of children with diseases of the airways.

DATA SOURCES

Medline and PubMed search, limited to English language and human disease, with keywords forced oscillation, impulse oscillometry, and asthma.

STUDY SELECTIONS

The opinions of the authors were used to select studies for inclusion in this review.

RESULTS

Impulse oscillometry is a noninvasive and rapid technique requiring only passive cooperation by the patient. Pressure oscillations are applied at the mouth to measure pulmonary resistance and reactance. It is employed by health care professionals to help diagnose pediatric pulmonary diseases such asthma and cystic fibrosis; assess therapeutic responses; and measure airway resistance during provocation testing.

CONCLUSIONS

Impulse oscillometry provides a rapid, noninvasive measure of airway impedance. It may be easily employed in the diagnosis and management of diseases of the airways in children.

Evaluation of interrupter resistance in methacholine challenge testing in children

Bronchial hyperresponsiveness (BHR) is a key feature of asthma and is assessed using bronchial provocation tests. The primary outcome in such tests (a 20% decrease in forced expiratory volume in 1 sec (FEV1)) is difficult to measure in young patients. This study evaluated the sensitivity and specificity of the interrupter resistance (Rint ) technique, which does not require active patient participation, by comparing it to the primary outcome measure. Methacholine challenge tests were performed in children with a history of moderate asthma and BHR. Mean and individual changes in Rint and FEV1 were studied. A receiver operating characteristic (ROC) curve was used to describe sensitivity and specificity of Rint . Seventy-three children (median age: 9.2 years; range: 6.3-13.4 years) participated. There was a significant (P < 0.01) increase in mean Rint with increasing methacholine doses. However, individual changes of Rint showed large fluctuations. There was great overlap in change of Rint between children who did and did not reach the FEV1 endpoint. A ROC curve showed an area under the curve of 0.65. Because of low sensitivity and specificity, the use of Rint to diagnose BHR in individual patients seems limited.

Viabilidade da realização de espirometria em pré-escolares

OBJETIVO: Determinar a taxa de sucesso na obtenção de resultados adequados de espirometria em pacientes pré-escolares. MÉTODOS: Foram analisados os resultados de espirometrias de crianças menores que 6 anos. Todos os testes foram realizados no Laboratório de Função Pulmonar do Hospital Infantil Jeser Amarante Faria, em Joinville (SC) entre junho de 2009 e fevereiro de 2010. O programa utilizado continha um incentivo de animação (bolhas de sabão).Os procedimentos foram realizados por um pneumologista infantil e obedeceram aos critérios de reprodutibilidade e aceitabilidade preconizados pela American Thoracic Society. Buscou-se atingir um tempo expiratório de pelo menos 1 s. Os seguintes parâmetros foram registrados: CVF, VEF0,5, VEF1 e relação VEF1/CVF. RESULTADOS: Nossa amostra consistiu de 74 crianças. A taxa de sucesso foi de 82%, com melhora no desempenho do teste em idades mais avançadas, mas sem significado estatístico (p > 0,05). Em média, foram necessárias 6,6 tentativas durante o exame para a obtenção de curvas aceitáveis e reprodutíveis. Todos os 61 testes bem sucedidos tiveram resultados de VEF0,5 e VEF1 satisfatórios. Através de escore Z, constatou-se que 21,6 % das crianças apresentavam com padrão obstrutivo. CONCLUSÕES: A taxa de sucesso da espirometria foi alta em nossa amostra, mostrando que esse é um método válido de avaliação da função pulmonar em pré-escolares. O uso de métodos de incentivo e a realização do teste por profissionais treinados no trabalho com crianças podem estar associados à elevada taxa de sucesso em nossa amostra

Reference values for respiratory system impedance using impulse oscillometry in healthy preschool children

PURPOSE

The normal values for lung resistance and lung capacity of children, as determined by impulse oscillometry (IOS), are different for children of different ethnicities. However, reference values there is no available reference value for Korean preschool children have yet to be determined. The aim of the present study was to determine the normal ranges of IOS parameters in Korean preschool children.

METHODS

A total of 133 healthy Korean preschool children were selected from 639 children (aged 3 to 6 years) who attended kindergarten in Seongnam, Gyeonggi province, Korea. Healthy children were defined according to the European Respiratory Society (ERS) criteria. All subjects underwent lung function tests using IOS. The relationships between IOS value (respiratory resistance (Rrs) and reactance (Xrs) at 5 and 10 Hz and resonance frequency (RF)) and age, height, and weight were analyzed by simple linear and multiple linear regression analyses.

RESULTS

The IOS success rate was 89.5%, yielding data on 119 children. Linear regression identified height as the best predictor of Rrs and Xrs. Using stepwise multiple linear regressions based on age, height, and weight, we determined regression equations and coefficients of determination (R(2)) for boys (Rrs(5)=1.934-0.009×Height, R(2)=12.1%; Xrs(5)=0.774+0.006×Height-0.002×Age, R(2)=20.2% and for girls (Rrs(5)=2.201-0.012×Height, R(2)=18.2%; Xrs(5)=-0.674+0.004×Height, R(2)=10.5%).

CONCLUSION

This study provides reference values for IOS measurements of normal Korean preschool children. These provide a basis for the diagnosis and monitoring of preschool children with a variety of respiratory diseases.

The opening interrupter technique for respiratory resistance measurements in children

BACKGROUND AND OBJECTIVE

The interrupter resistance (Rint) can be calculated from various estimates of alveolar pressure based on mouth pressure during occlusion. We compared Rint, as measured by the opening interrupter technique (Rint1), and the linear back-extrapolation method (Rint2), with the 'gold standard' airway resistance measured by plethysmography (Raw).

METHODS

The study included 32 asthmatic children and 11 children with cystic fibrosis, aged 5 to 18 years, who were categorized into non-obstructed (NObs) (n = 27) and obstructed (Obs) (n = 16) groups. Spirometry and the three different resistance measurements were performed on all children. Rint1 and Raw were assessed after a bronchodilator (BD) test in 16 and nine children, respectively, in the Obs group.

RESULTS

Raw (0.48 ± 0.20 kPa.s/L) was lower than Rint1 (1.04 ± 0.34 kPa.s/L) and Rint2 (0.63 ± 0.18 kPa.s/L) (P < 0.001). Raw, but neither Rint1 nor Rint2, was significantly higher in the Obs group than in the NObs group (0.57 ± 0.23 vs 0.42 ± 0.16 kPa.s/L, P < 0.05). The differences Rint1-Raw and Rint2-Raw were correlated with FEV(1) /VC (P < 0.01 and P < 0.001), and Rint1-Raw was correlated with height (P < 0.001). After BD significant changes in Rint1 and Raw were observed in 5/9 and 7/9 children, respectively.

CONCLUSIONS

Rint2, as well as Rint1, may be underestimated in the most Obs children and may therefore fail to detect severe obstruction. Rint1 is likely to include a non-negligible contribution from the tissue component, especially in the youngest children. Although not different between Obs and NObs children at baseline, Rint1 did detect bronchodilation in some Obs children.

Preterm birth and respiratory disease in later life

Chronic respiratory diseases are a common complication of preterm birth, particularly among very immature infants or those suffering from bronchopulmonary dysplasia. Major progress in the treatment of preterm newborns has changed the pattern of late respiratory complications. The major respiratory problem in infancy and early childhood is respiratory exacerbations caused by infections (particularly viral ones), which need hospitalization. The symptoms become mild in school-age children; however, a group of children still present with chronic airway obstruction defined by recurrent episodes of wheezing and decreased lung function tests (decreased forced expiratory volume). For some preterm infants, particularly those with bronchopulmonary dysplasia, obstructive lung disease persists into adulthood. They are very likely to develop chronic obstructive pulmonary disease or similar disease later in life. In these patients, a program of lung function monitoring and pulmonary prophylaxis by means of elimination of specific risk factors in adulthood is advisable.