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

Comparison of phenotypes of childhood wheeze and cough in 2 independent cohorts

BACKGROUND

Among children with wheeze and recurrent cough there is great variation in clinical presentation and time course of the disease. We previously distinguished 5 phenotypes of wheeze and cough in early childhood by applying latent class analysis to longitudinal data from a population-based cohort (original cohort).

OBJECTIVE

To validate previously identified phenotypes of childhood cough and wheeze in an independent cohort.

METHODS

We included 903 children reporting wheeze or recurrent cough from an independent population-based cohort (validation cohort). As in the original cohort, we used latent class analysis to identify phenotypes on the basis of symptoms of wheeze and cough at 2 time points (preschool and school age) and objective measurements of atopy, lung function, and airway responsiveness (school age). Prognostic outcomes (wheeze, bronchodilator use, cough apart from colds) 5 years later were compared across phenotypes.

RESULTS

When using a 5-phenotype model, the analysis distinguished 3 phenotypes of wheeze and 2 of cough as in the original cohort. Two phenotypes were closely similar in both cohorts: Atopic persistent wheeze (persistent multiple trigger wheeze and chronic cough, atopy and reduced lung function, poor prognosis) and transient viral wheeze (early-onset transient wheeze with viral triggers, favorable prognosis). The other phenotypes differed more between cohorts. These differences might be explained by differences in age at measurements.

CONCLUSIONS

Applying the same method to 2 different cohorts, we consistently identified 2 phenotypes of wheeze (atopic persistent wheeze, transient viral wheeze), suggesting that these represent distinct disease processes. Differences found in other phenotypes suggest that the age when features are assessed is critical and should be considered carefully when defining phenotypes.

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.

Office-based exhaled nitric oxide measurement in children 4 years of age and older

BACKGROUND

Fractional exhaled nitric oxide (FENO) is increasingly being used in the office-based management of asthma, but data in children are limited.

OBJECTIVES

To report FENO values in 4- to 7-year-old children with suspected asthma and characterize their relation to clinical variables and describe the relation among FENO levels, age, and sex in 4- to 18-year-old children with suspected asthma.

METHODS

Retrospective data in 4- to 18-year-old children (n = 825) who underwent FENO testing using the NIOX MINO device were collected and analyzed. Chart reviews were performed for the 4- to 7-year-old children (n = 75).

RESULTS

FENO values ranged from less than or equal to 5 to 89 ppb in 75 4- to 7-year-old children and less than or equal to 5 to 300 ppb in 750 > 7 to 18-year-old children. Approximately one tenth of 4- to 7-year-old children and one third of > 7 to 18-year-old children had FENO values indicative of eosinophilic/allergic inflammation (>35 ppb). In regression analysis of the 4- to 7-year-old children, increasing age (P = .03) and asthma severity (P = .01) were associated with higher FENO levels. Atopic dermatitis was significantly associated (P = .03), whereas allergic rhinitis was marginally associated (P = .06), with higher FENO levels. Inhaled corticosteroid use was associated with lower FENO levels (P = .02).

CONCLUSION

This study characterizes the largest cohort of 4- to 7-year-old children to undergo FENO testing in ambulatory asthma management. Correlations between FENO levels and clinical variables were consistent with established findings in older children. This preliminary real-world study suggests that FENO assessment may be feasible and useful in the office-based asthma management of children as young as 4 years.

Practicability of nitrogen multiple-breath washout measurements in a pediatric cystic fibrosis outpatient setting

BACKGROUND

Although lung clearance index (LCI) is a sensitive indicator of mild cystic fibrosis (CF) lung disease, it is rarely measured due to lengthy protocols and the commercial unavailability of multiple-breath washout (MBW) setups and tracer gases. We used a newly validated, commercially available nitrogen (N2 ) MBW setup to assess success rate, duration, and variability of LCI within a 20 min timeframe, during clinical routine. We also evaluated the relationship between LCI and other clinical markers of CF lung disease.

METHODS

One hundred thirty six children (83 with CF) between 4 and 16 years were studied in a pediatric CF outpatient setting. One hundred eighteen out of 136 children were naïve to MBW. Within 20 min, each child was trained, N2 MBW was performed, and LCI was analyzed. We assessed intra- and between-test reproducibility in a subgroup of children.

RESULTS

At least one LCI was feasible in 123 (90%) children, with a mean (range) of 3.3 (1.2-6.4) min per test. Two or more measurements were feasible in 56 (41%) children. Comparing LCI in CF versus controls, LCI mean (SD) was 12.0 (3.9) versus 6.1 (0.9), and the intra- and inter-test coefficient of repeatability was 1.00 versus 0.81 and 0.96 versus 0.62, respectively. LCI was correlated with spirometry, blood gases, and Pseudomonas aeruginosa infection.

CONCLUSIONS

Using available N2 MBW equipment, LCI measurements are practical and fast in children. LCI is correlated with markers of CF lung disease. Longer timeframes would be required for triplicate N2 MBW tests in inexperienced children.

Joint modeling of parentally reported and physician-confirmed wheeze identifies children with persistent troublesome wheezing

BACKGROUND

Previous studies have suggested the presence of different childhood wheeze phenotypes through statistical modeling based on parentally reported wheezing.

OBJECTIVE

We sought to investigate whether joint modeling of observations from both medical records and parental reports helps to more accurately define wheezing disorders during childhood and whether incorporating information from medical records better characterizes severity.

METHODS

In a population-based birth cohort (n = 1184), we analyzed data from 2 sources (parentally reported current wheeze at 4 follow-ups and physician-confirmed wheeze from medical records in each year from birth to age 8 years) to determine classes of children who differ in wheeze trajectories. We tested the validity of these classes by examining their relationships with objective outcomes (lung function, airway hyperreactivity, and atopy), asthma medication, and severe exacerbations.

RESULTS

Longitudinal latent class modeling identified a 5-class model that best described the data. We assigned classes as follows: no wheezing (53.3%), transient early wheeze (13.7%), late-onset wheeze (16.7%), persistent controlled wheeze (13.1%), and persistent troublesome wheeze (PTW; 3.2%). Longitudinal trajectories of atopy and lung function differed significantly between classes. Patients in the PTW class had diminished lung function and more hyperreactive airways compared with all other classes. We observed striking differences in exacerbations, hospitalizations, and unscheduled visits, all of which were markedly higher in patients in the PTW class compared with those in the other classes. For example, the risk of exacerbation was much higher in patients in the PTW class compared with patients with persistent controlled wheeze (odds ratio [OR], 3.58; 95% CI, 1.27-10.09), late-onset wheeze (OR, 15.92; 95% CI, 5.61-45.15), and transient early wheeze (OR, 12.24; 95% CI, 4.28-35.03).

CONCLUSION

We identified a novel group of children with persistent troublesome wheezing, who have markedly different outcomes compared with persistent wheezers with controlled disease.

Feasibility and reproducibility of spirometry and inductance plethysmography in healthy Brazilian preschoolers

RATIONALE

Preschoolers show peculiarities that reinforce the importance of assessing their pulmonary function. However, there are few data on the success rate and between-occasions reproducibility of pulmonary function tests in preschoolers, particularly in the Brazilian population.

OBJECTIVE

To assess the success rate and between-occasions reproducibility of the variables obtained by spirometry and respiratory inductive plethysmography in healthy children aged 4-6 years.

METHODS

Breathing pattern was assessed by plethysmography (tidal volume-V(T), respiratory rate-f, inspiratory duty cycle-Ti/Ttot, mean respiratory flow-V(T)/Ti, displacement of the rib cage-RC and phase relation during the total breath-PhRTB) and spirometry (forced vital capacity-FVC, forced expiratory volume in 0.5 sec-FEV0.5 and forced expiratory volume in first second-FEV1) in 47 healthy children, aged 4-6 years. To evaluate between-occasions reproducibility, 10 children (according to the sample size calculation) were reassessed after 3 weeks. Between-occasions reproducibility was evaluated by paired t-test, considering significant P < 0.05, Intraclass Correlation Coefficient (ICC) and coefficient of variation of method error (CV(ME)).

RESULTS

The results showed an 83% success rate for spirometry and a 98% success rate for plethysmography. Regarding reproducibility, there were no significant differences between the variables of any test. Spirometry ICC was above 0.80 and the CV(ME) was lower than 10%. The plethysmography ICC was between 0.61 and 0.95, and the CV(ME) was between 2% and 31%.

CONCLUSIONS

These results suggest a high success rate in performing the pulmonary function tests and good between-occasions reproducibility for spirometry and plethysmography in healthy preschoolers.

Validation of novel wheeze phenotypes using longitudinal airway function and atopic sensitization data in the first 6 years of life: evidence from the Southampton Women's survey

BACKGROUND

In 1995 the Tucson Children's Respiratory Study (TCRS) identified clinically distinct phenotypes amongst early wheezers; the Avon Longitudinal Study of Parents And Children (ALSPAC) has recently re-examined these.

OBJECTIVES

To validate statistically derived ALSPAC phenotypes in the Southampton Women's Survey (SWS) using infant and 6-year lung function, and allergic sensitization at 1, 3, and 6 years, comparing these with TCRS phenotypes.

METHODS

Complete 6-year follow-up data were available for 926 children, selected from 1,973 infants born to 12,579 women characterized pre-conception. Ninety-five children had V'maxFRC and FEV0.4 measured age 5-14 weeks using rapid compression/raised volume techniques. At 6 years we performed spirometry (n = 791), fractional exhaled nitric oxide (FeNO, n = 589) and methacholine challenge (n = 234). Skin prick testing was performed at 12m, 3 and 6 years (n = 1,494, 1,255, 699, respectively). Using wheeze status questionnaire data at 6m, 12m, 2, 3 and 6 years we classified children into TCRS (never, transient early, persistent, late-onset) and ALSPAC based groups (never, early, transient, intermediate-onset, late-onset, persistent).

RESULTS

Amongst ALSPAC groups, persistent and late-onset wheeze were associated with atopy at 3 and 6 years, whilst intermediate-onset wheeze showed earlier atopic association at 1 year; all three were associated with FeNO at 6 years. Persistent wheezers had lower infant (V'maxFRC P < 0.05) and 6-year lung function (FEV1, FEV1/FVC, and FEF(25-75), P < 0.05), whilst late and intermediate-onset wheezers showed no lung function deficits. Transient wheezers were non-atopic but showed persistent lung function deficits (V'maxFRC in infancy, FEV1 and FEF(25-75) at 6 years, all P < 0.05). Those who wheezed only in the first year (early phenotype) showed no lung function deficits. No associations were seen with 6 years bronchial hyper-responsiveness or infancy FEV0.4.

CONCLUSION

SWS cohort data validates the statistically derived ALSPAC six-class model. In particular, lung function and atopy successfully differentiate persistent, late-onset and intermediate-onset wheeze, whilst the Tucson "transient early" wheeze phenotype can be sub-classified into groups that reflect early lung function. Since the 4-class model fails to adequately differentiate phenotypes based on lung function and atopy, we propose that strong consideration be given to using the 6-class paradigm for longitudinal outcome work in wheezing with onset in early life.

Reference values for spirometry in preschool children

OBJECTIVES

Reference values for lung function tests differ in samples from different countries, including values for preschoolers. The main objective of this study was to derive reference values in this population.

METHODS

A prospective study was conducted through a questionnaire applied to 425 preschool children aged 3 to 6 years, from schools and day-care centers in a metropolitan city in Brazil. Children were selected by simple random sampling from the aforementioned schools. Peak expiratory flow (PEF), forced vital capacity (FVC), forced expiratory volumes (FEV1, FEV0.50), forced expiratory flow (FEF25-75) and FEV1/FVC, FEV0.5/FVC and FEF25-75/FVC ratios were evaluated.

RESULTS

Of the 425 children enrolled, 321 (75.6%) underwent the tests. Of these, 135 (42.0%) showed acceptable results with full expiratory curves and thus were included in the regression analysis to define the reference values. Height and gender significantly influenced FVC values through linear and logarithmic regression analysis. In males, R(2) increased with the logarithmic model for FVC and FEV1, but the linear model was retained for its simplicity. The lower limits were calculated by measuring the fifth percentile residues.

CONCLUSION

Full expiratory curves are more difficult to obtain in preschoolers. In addition to height, gender also influences the measures of FVC and FEV1. Reference values were defined for spirometry in preschool children in this population, which are applicable to similar populations.

Respiratory impedance and bronchodilator responsiveness in healthy children aged 2-13 years

BACKGROUND

The forced oscillation technique (FOT) can be used in children as young as 2 years of age and in those unable to perform routine spirometry. There is limited information on changes in FOT outcomes in healthy children beyond the preschool years and the level of bronchodilator responsiveness (BDR) in healthy children. We aimed to create reference ranges for respiratory impedance outcomes collated from multiple centers. Outcomes included respiratory system resistance (R(rs)) and reactance (X(rs)), resonant frequency (Fres), frequency dependence of R(rs) (Fdep), and the area under the reactance curve (AX). We also aimed to define the physiological effects of bronchodilators in a large population of healthy children using the FOT.

METHODS

Respiratory impedance was measured in 760 healthy children, aged 2-13 years, from Australia and Italy. Stepwise linear regression identified anthropometric predictors of transformed R(rs) and X(rs) at 6, 8, and 10 Hz, Fres, Fdep, and AX. Bronchodilator response (BDR) was assessed in 508 children after 200 µg of inhaled salbutamol.

RESULTS

Regression analysis showed that R(rs), X(rs), and AX outcomes were dependent on height and sex. The BDR cut-offs by absolute change in R(rs8), X(rs8), and AX were -2.74 hPa s L(-1), 1.93 hPa s L(-1), and -33 hPa s L(-1), respectively. These corresponded to relative and Z-score changes of -32%; -1.85 for R(rs8), 65%; 1.95 for X(rs8), and -82%; -2.04 for AX.

CONCLUSIONS

We have established generalizable reference ranges for respiratory impedance and defined cut-offs for a positive bronchodilator response using the FOT in healthy children.

Vocal cord dysfunction as demonstrated by impulse oscillometry

BACKGROUND

Vocal cord dysfunction (VCD) is a respiratory disorder characterized by inappropriate vocal cord adduction during inspiration. The diagnosis of VCD is challenging, because expected flow volume loop abnormalities are uncommonly noted, and laryngoscopy must be timed to coincide with symptoms.

OBJECTIVE

We wanted to determine the potential role of impulse oscillometry (IOS) in the diagnosis of VCD.

METHODS

We conducted an analysis of six patients in which the diagnosis of VCD was being considered as well as seven healthy subjects and five subjects with asthma. All were evaluated with IOS and spirometry, and patients underwent laryngoscopy. Two patients with suspected VCD who did not exhibit symptoms or abnormal pulmonary function at baseline underwent exercise challenge and repeat studies. One patient with suspected VCD underwent an additional irritant challenge.

RESULTS

VCD was diagnosed by laryngoscopy in three of the six patients in whom the diagnosis of VCD was entertained. These three patients as a group all exhibited higher amplitude (mean, 9.3 cm H20/L/second) and more variable spikes (SD, 4.8 cm H20/L/second) on IOS impedance during inspiration, whereas the three patients in whom the diagnosis was not confirmed by endoscopy did not show these findings (mean, 2.0 cm H20/L/second; P < .0002; SD, 0.8 cm H20/L/second; P < .0001). This pattern was also not observed in the healthy volunteers (mean ± SD, 1.8 ± 0.7 cm H20/L/second) and patients with asthma at baseline (mean, 4.2 ± 1.2 cm H20/L/second) or after exercise challenge (mean, 1.5 ± 0.5 cm H20/L/second).

CONCLUSIONS

These findings support the conclusion that IOS displays a characteristic pattern in patients with VCD and thus may offer a rapid and noninvasive adjunct to the assessment and diagnosis of patients suspected to have this disorder.

Prenatal vitamin d supplementation and child respiratory health: a randomised controlled trial

BACKGROUND

Observational studies suggest high prenatal vitamin D intake may be associated with reduced childhood wheezing. We examined the effect of prenatal vitamin D on childhood wheezing in an interventional study.

METHODS

We randomised 180 pregnant women at 27 weeks gestation to either no vitamin D, 800 IU ergocalciferol daily until delivery or single oral bolus of 200,000 IU cholecalciferol, in an ethnically stratified, randomised controlled trial. Supplementation improved but did not optimise vitamin D status. Researchers blind to allocation assessed offspring at 3 years. Primary outcome was any history of wheeze assessed by validated questionnaire. Secondary outcomes included atopy, respiratory infection, impulse oscillometry and exhaled nitric oxide. Primary analyses used logistic and linear regression.

RESULTS

We evaluated 158 of 180 (88%) offspring at age 3 years for the primary outcome. Atopy was assessed by skin test for 95 children (53%), serum IgE for 86 (48%), exhaled nitric oxide for 62 (34%) and impulse oscillometry of acceptable quality for 51 (28%). We found no difference between supplemented and control groups in risk of wheeze [no vitamin D: 14/50 (28%); any vitamin D: 26/108 (24%) (risk ratio 0.86; 95% confidence interval 0.49, 1.50; P = 0.69)]. There was no significant difference in atopy, eczema risk, lung function or exhaled nitric oxide between supplemented groups and controls.

CONCLUSION

Prenatal vitamin D supplementation in late pregnancy that had a modest effect on cord blood vitamin D level, was not associated with decreased wheezing in offspring at age three years.

TRIAL REGISTRATION

Controlled-Trials.com ISRCTN68645785.

Effect of paracetamol use on the modification of the development of asthma by reactive oxygen species genes

BACKGROUND

Recent studies have identified an increase in the prevalence of asthma associated with paracetamol use.

OBJECTIVE

To identify the relationship among asthma, biomarkers, genes, and paracetamol use in preschool children.

METHODS

We undertook a population-based, cross-sectional survey of 933 preschool children. Asthma status was classified according to medical history and asthmatic symptoms. History of paracetamol use in infancy was recorded. Impulse oscillometry, blood tests for eosinophils and total IgE, and genotyping of NAT2, Nrf2, and GSTP1 polymorphisms by TaqMan assay were conducted.

RESULT

Paracetamol use in infancy was associated with an increased risk of treatment for asthma within the previous 12 months. Paracetamol use together with a family history of asthma increased the risk of asthma diagnosis ever, current asthma, and treatment for asthma within the previous 12 months. Gene polymorphisms in NAT2 (rs4271002), Nrf2 (rd6726395), and GSTP1 (rd1695) increased the risk of treatment for asthma within the last 12 months. Eosinophils were significantly elevated in the group with paracetamol use and a family history of asthma; however, the serum total IgE level and IOS did not show any significant difference.

CONCLUSION

Paracetamol use in infancy was significantly associated with increased risk of asthma. The association is more significant in genetically susceptible children, related to antioxidant genes, and the effect may be mediated by eosinophilic inflammation.

Fraction of exhaled nitric oxide and wheezing phenotypes in preschool children

BACKGROUND

Asthma is a chronic lower airway inflammatory disease. Nitric oxide is an inflammatory mediator produced endogenously in the airway. Previous studies have demonstrated that the fractional concentration of exhaled nitric oxide (FeNO) is increased in asthma.

OBJECTIVES

To investigate if FeNO concentrations were correlated with wheezing phenotypes in preschool children and to compare the FeNO results with airway hyperresponsiveness (AHR) and pulmonary function test (PFT) results.

METHODS

We performed skin prick tests, methacholine provocation tests, PFT, impulse oscillometry bronchodilator response (IOS BDR) tests, and FeNO measurements in 372 preschool children between the ages of 4 and 6 years. Wheezing phenotypes were defined according to the age of onset and persistency.

RESULTS

Persistent wheezers had higher FeNO levels than transient wheezers and non-wheezers. Among persistent wheezers, those with atopy and AHR had significantly higher FeNO levels than those without atopy or AHR. FeNO levels were significantly higher in late-onset wheezers than early-onset wheezers and non-wheezers. Among late-onset wheezers, those with atopy and AHR had a significantly higher FeNO concentration than those without atopy or AHR as well as those with either atopy or AHR. However, there were no significant differences in AHR, PFT, or IOS BDR between persistent and transient wheezers or between late-onset wheezers and early-onset wheezers.

CONCLUSION

FeNO may be a better marker for asthma phenotypes in preschool children than AHR and PFT results.

Spirometry. Spanish Society of Pulmonology and Thoracic Surgery (SEPAR)

Spirometry is the main pulmonary function test and is essential for the evaluation and monitoring of respiratory diseases. Its utility transcends the field of Respiratory Medicine, is becoming increasingly important in primary care and applications have even been described outside the field of respiratory diseases. This document is therefore intended to serve as support for all health professionals who use spirometry, providing recommendations based on the best scientific evidence available. An update of the indications and contraindications of the test is proposed. The document sets out recommendations on the requirements necessary for conventional spirometers and portable office equipment, as well as on spirometer hygiene and quality control measures. Spirometric parameters that must be considered, performance of manoeuvres, criteria for acceptability and repeatability of measurements and their quality control are defined. A proposal is also established for presentation of the results and an evaluation and interpretation is proposed according to information generated in recent years. Finally, lines of adaptation and integration of spirometry in the field of new technologies are considered.

Forced expiratory decay in asthmatic preschool children--is it adult type?

BACKGROUND

The forced expiratory decay in healthy preschool children portrays a convex shape that differs from the linear decay in the older healthy population. The "adult-type" expiratory decay during airway obstruction is concave. The study objective was to determine if the expiratory decay in young asthmatic children is "adult-type".

METHODS

Among 245 children (age 3-7 yrs), 178 had asthma (asthmatics) and 67 were non-asthmatic (controls). The expiratory flow decay was inspected by FEF25-75/FVC ratio (=1.0 when linear). Values were compared to those of our formerly studied (n = 108) healthy children. A meaningful obstruction in FEF25-75/FVC ratio was defined as 2-zScores from healthy. A meaningful response to bronchodilators was related to non-asthmatics.

RESULTS

In healthy subjects FEF25-75/FVC ratio declined with age from 1.73 ± 0.17 to 1.28 ± 0.11. Non-asthmatics portrayed ratio values similar to those of healthy subjects. In asthmatics, 118/178 displayed a convex to linear expiratory decay (FEF25-75/FVC = 1.33 ± 0.22). Sixty/178 asthmatics portrayed concavity (FEF25-75/FVC-0.79 ± 0.16) that appeared when FEF50 was 43.4 ± 12%healthy. Concavity appearance was also age-dependent (30.4% of 3-4 y old and 59.1% of 6-7 y). Vital-Capacity decreased in either decays, forming a visually petit curve. Most asthmatic children respond to bronchodilators by a meaningful elevation in FEF25-75/FVC values and by a visual change in the shape of the curve. Other common spirometry indices also increased meaningfully.

CONCLUSION

Most asthmatic preschool children portray convex to linear expiratory decay with diminished vital-capacity, resulting in a visually smaller than healthy curve, with seemingly normal expiratory decay. These curves may be misinterpreted as "normal" or as "no-cooperation" and may lead to misinterpretation. In response to bronchodilators, FEF25-75/FVC value increases in asthmatics and the curve changes from concave to linear or from linear to convex contour.

Lung transplantation for childhood diffuse lung disease

BACKGROUND

Pediatric diffuse lung diseases comprise a heterogeneous group of rare lung disorders which may lead to end stage lung disease and referral for lung transplantation. Previous studies are limited by small numbers of patients with specific forms of diffuse lung disease. Children with all forms of diffuse lung disease who underwent lung transplantation at two pediatric centers were evaluated in terms of several pre- and post-transplant factors and compared to children with other end stage lung disorders.

METHODS

A retrospective chart review was performed on all patients transplanted between October 1, 2002 and June 15, 2007 at Texas Children's Hospital and St. Louis Children's Hospital. Multiple pre-transplant characteristics and post-transplant morbidities and mortality were compared between diffuse lung disease, cystic fibrosis, and pulmonary vascular disease groups.

RESULTS

There were 31 diffuse lung disease (DLD), 57 cystic fibrosis (CF), and 16 pulmonary vascular disease (PVD) patients included in our analysis. Patients with DLD had significantly higher pre-transplant morbidity including lower percent predicted of forced expiratory volume in first second (P = 0.013) and more patients with pulmonary hypertension (P = 0.001) and hypercapnia (P = 0.031). Compared to CF patients, more DLD and PVD patients required invasive ventilation (P = 0.001) and care in the pediatric intensive care unit (P = 0.001). After transplant, there was a difference among the three groups with regards to number of acute allograft rejections but statistical limitations preclude knowing between which group the difference lies. A difference in time to bronchiolitis obliterans was found between the PVD and CF groups but not when compared to the DLD patients. The three groups had similar time to post-transplant lymphoproliferative disease, rate of infections, and survival.

CONCLUSION

Lung transplantation is as successful for patients with end stage diffuse lung disease as compared to other lung transplant candidates.

Vitamin A deficiency alters airway resistance in children with acute upper respiratory infection

OBJECTIVE

To assess whether vitamin A deficiency alters the recovery of total respiratory resistance (TRR) following acute upper respiratory tract infection (URI).

METHODS

This is a case control study of children, age 4-6 years and grouped as: URI, (n = 74), URI and wheezing, (URI-wheezing, n = 52), and healthy controls (n = 51). Vitamin A and total respiratory resistance (TRR) were assessed using the modified relative dose response (MRDR) and forced oscillometry, respectively.

RESULTS

Children with URI and URI-wheezing had lower retinol, 32.4 ± 13.12 and 18.3 ± 6.83 µg/dl respectively, compared to controls, 56.9 ± 29.82 µg/dl (ANOVA, P < 0.001). The MRDR was elevated in children in the URI or URI-wheezing groups 0.066 ± 0.045 and 0.021 ± 0.021, respectively, compared to controls 0.007 ± 0.006 (ANOVA, P < 0.0001). The TRR in the URI and URI-wheezing groups differed from controls. During convalescence, the TRR failed to decline in the URI-group only when the MRDR was >0.06. In the URI-wheezing group, TRR declined independently of retinol and MRDR.

CONCLUSION

Vitamin A contributes to preservation of airway function during and in recovery after upper respiratory infection in children.

Outpatient management of asthma in children

The principal aims of asthma management in childhood are to obtain symptom control that allows individuals to engage in unrestricted physical activities and to normalize lung function. These aims should be achieved using the fewest possible medications. Ensuring a correct diagnosis is the first priority. The mainstay of asthma management remains pharmacotherapy. Various treatment options are discussed. Asthma monitoring includes the regular assessment of asthma severity and asthma control, which then informs decisions regarding the stepping up or stepping down of therapy. Delivery systems and devices for inhaled therapy are discussed, as are the factors influencing adherence to prescribed treatment. The role of the pediatric health care provider is to establish a functional partnership with the child and their family in order to minimize the impact of asthma symptoms and exacerbations during childhood.

Reference ranges for Mexican preschool-aged children using the forced oscillation technique

INTRODUCTION

Recently, multi-ethnic reference ranges for spirometry have been created for use worldwide. In comparison, forced oscillation technique (FOT) reference values are limited to specific equipment and study populations, with current FOT reference ranges created in a Caucasian population. We aimed to develop FOT reference ranges for preschool-aged Mexican children and to compare these with current FOT reference ranges.

PATIENTS AND METHODS

Respiratory resistance (Rrs) and reactance (Xrs) was measured in healthy Mexican children three to five years of age using commercial FOT equipment. The relationship between height and Rrs and Xrs was determined using regression analyses, taking into account age, weight, sex, and exposure to tobacco smoke. Reference equations were calculated for the Mexican children and Z-scores determined for Rrs and Xrs at 6 and 8Hz. A paired t-test assessed the difference in Z-scores between the Australian reference values and those created for the Mexican cohort.

RESULTS

FOT was successfully measured in 584 children. Height was a significant predictor of Rrs and Xrs at 6 and 8Hz (P<.05). Z-scores calculated using the Australian reference equations overestimated lung function in Mexican children for both Rrs and Xrs at 6 and 8Hz (P<.001).

CONCLUSION

The development of FOT reference ranges specific to Mexican preschool-aged children will allow for the correct interpretation of FOT measurements. This study also showed that current FOT reference ranges overestimate lung function in Mexican children. Highlighting, the importance of using ethnic appropriate reference ranges for interpreting lung function.

Oscillometric and spirometric bronchodilator response in preschool children with and without asthma

BACKGROUND

Bronchodilator responses (BDR) are routinely used in the diagnosis and management of asthma; however, their acceptability and repeatability have not been evaluated using quality control criteria for preschool children.

OBJECTIVES

To compare conventional spirometry with an impulse oscillometry system (IOS) in healthy and asthmatic preschool children.

METHODS

Data from 30 asthmatic children and 29 controls (two to six years of age) who underwent IOS and spirometry before and after salbutamol administration were analyzed.

RESULTS

Stable asthmatic subjects significantly differed versus controls in their spirometry-assessed BDR (forced expiratory volume in 1 s [FEV1], forced vital capacity and forced expiratory flow at 25% to 75% of forced vital capacity) as well as their IOS-assessed BDR (respiratory resistance at 5 Hz [Rrs5], respiratory reactance at 5 Hz and area under the reactance curve). However, comparisons based on the area under the ROC curve for &Delta;FEV1 %initial versus &Delta;Rrs5 % initial were 0.82 (95% CI 0.71 to 0.93) and 0.75 (95% CI 0.62 to 0.87), respectively. Moreover, the sensitivity and specificity for &Delta;FEV1 >=9% were 0.53 and 0.93, respectively. Importantly, sensitivity increased to 0.63 when either &Delta;FEV1 >=9% or &Delta;Rrs5 >=29% was considered as an additional criterion for the diagnosis of asthma.

CONCLUSION

The accuracy of asthma diagnosis in preschool children may be increased by combining spirometry with IOS when measuring BDR.

Abbreviated multi-breath washout for calculation of lung clearance index

INTRODUCTION

Various functional residual capacity (FRC) repeatability criteria have been proposed for lung clearance index (LCI) measurement by multiple breath washout (MBW). Adult guidelines recommend three technically acceptable tests with FRC values within 10%, whilst preschool guidelines recommend two such tests. Feasibility of and need for recommendations in children is unclear.

METHODS

Retrospective analysis of MBW data was undertaken in healthy control (n = 90) and cystic fibrosis (CF) subjects (n = 108) encompassing infancy, pre-school and school age ranges. Feasibility of FRC repeatability recommendations was investigated in those with three technically acceptable tests. Validity of mean LCI from the first two tests alone (vs. all three) was investigated by comparing mean data and sensitivity to detect abnormal peripheral airway function in CF.

RESULTS

LCI coefficient of variation (CoV) was related to FRC CoV (P < 0.001) and disease category (P = 0.002). Application of adult repeatability criteria decreased LCI CoV (4.7 vs. 8.5%, P < 0.001), but had poor feasibility beyond infancy (62/150, 41%). Preschool recommendations increased feasibility but only to 70% overall. There was no difference in mean LCI (All three minus 1st two tests) in healthy controls [mean (95% CI) difference: 0.02 (-0.01, 0.06; P = 0.15)], this difference being statistically but not clinically significant in CF subjects [0.07 (0.00,0.13; P = 0.04)]. Sensitivity in CF subjects was unaffected.

CONCLUSION

Adult FRC repeatability recommendations improved LCI repeatability in pediatric subjects, but poor feasibility limited utility. In an experienced pediatric MBW center, recent preschool recommendations can be extended to two technically acceptable tests, irrespective of FRC repeatability, without significantly affecting mean LCI or compromising sensitivity.

Psychosocial factors and behavioral medicine interventions in asthma

OBJECTIVE

This review examines the evidence for psychosocial influences in asthma and behavioral medicine approaches to its treatment.

METHOD

We conducted a systematic review of the literature on psychosocial influences and the evidence for behavioral interventions in asthma with a focus on research in the past 10 years and clinical trials. Additional attention was directed at promising new developments in the field.

RESULTS

Psychosocial factors can influence the pathogenesis and pathophysiology of asthma, either directly through autonomic, endocrine, immunological, and central nervous system mechanisms or indirectly through lifestyle factors, health behaviors, illness cognitions, and disease management, including medication adherence and trigger avoidance. The recent decade has witnessed surging interest in behavioral interventions that target the various pathways of influence. Among these, self-management training, breathing training, and exercise or physical activation programs have proved particularly useful, whereas other essential or promising interventions, such as smoking cessation, dietary programs, perception and biofeedback training, and suggestive or expressive psychotherapy, require further, more rigorous evaluation. Given the high comorbidity with anxiety and mood disorders, further evaluation of illness-specific cognitive behavior therapy is of particular importance. Progress has also been made in devising community-based and culturally tailored intervention programs.

CONCLUSION

In concert with an essential medication treatment, behavioral medicine treatment of asthma is moving closer toward an integrated biopsychosocial approach to disease management.

Exhaled nitric oxide in symptomatic children at preschool age predicts later asthma

BACKGROUND

Prediction of asthma in young children with respiratory symptoms is hampered by the lack of objective measures applicable in clinical routine. In this prospective study in a preschool children cohort, we assessed whether the fraction of exhaled nitric oxide (FeNO), a biomarker of airway inflammation, is associated with asthma at school age.

METHODS

At baseline, IgE and eosinophils were measured in the blood, and FeNO was measured offline in 391 children aged 3-47 months with lower airway symptoms. We developed an asthma predictive index (API) including high FeNO as major criterion. At follow-up, primary outcome was physician-diagnosed asthma based on standardized interviews in those children reaching school age (n = 166).

RESULTS

FeNO was significantly elevated in those children with later asthma (68/166) as compared to children not developing asthma. Median (IQR) FeNO was 10.5 (6.6-17.2) vs. 7.4 (5.3-10.3) ppb. Per 5 ppb FeNO increase, the odds ratio (95% CI) for asthma increased by 2.44 (1.61-3.70) without changing when adjusting for confounders. Using the new API, children scored at risk had 58.0% probability for later asthma, whereas the negative predictive value was 78.2%, which was comparable to the classical API.

CONCLUSIONS

In this cohort of high-risk preschool children, elevated FeNO is associated with increased risk for school-age asthma. The new API including FeNO identifies children at risk of later asthma comparably to the classical API, but does not require blood sampling.

The relationship between maternal adiposity and infant weight gain, and childhood wheeze and atopy

BACKGROUND

Obesity and asthma have increased in westernised countries. Maternal obesity may increase childhood asthma risk. If this relation is causal, it may be mediated through factors associated with maternal adiposity, such as fetal development, pregnancy complications or infant adiposity. We investigated the relationships of maternal body mass index (BMI) and fat mass with childhood wheeze, and examined the influences of infant weight gain and childhood obesity.

METHODS

Maternal prepregnancy BMI and estimated fat mass (from skinfold thicknesses) were related to asthma, wheeze and atopy in 940 children. Transient or persistent/late wheeze was classified using questionnaire data collected at ages 6, 12, 24 and 36 months and 6 years. At 6 years, skin-prick testing was conducted and exhaled nitric oxide and spirometry measured. Infant adiposity gain was calculated from skinfold thickness at birth and 6 months.

RESULTS

Greater maternal BMI and fat mass were associated with increased childhood wheeze (relative risk (RR) 1.08 per 5 kg/m(2), p=0.006; RR 1.09 per 10 kg, p=0.003); these reflected associations with transient wheeze (RR 1.11, p=0.003; RR 1.13, p=0.002, respectively), but not with persistent wheeze or asthma. Infant adiposity gain was associated with persistent wheeze, but not significantly. Adjusting for infant adiposity gain or BMI at 3 or 6 years did not reduce the association between maternal adiposity and transient wheeze. Maternal adiposity was not associated with offspring atopy, exhaled nitric oxide, or spirometry.

DISCUSSION

Greater maternal adiposity is associated with transient wheeze but not asthma or atopy, suggesting effects upon airway structure/function but not allergic predisposition.

Assessment of exercise-induced bronchoconstriction in adolescents and young children

Recent research shows important differences in exercise-induced bronchoconstriction (EIB) between children and adults, suggesting a different pathophysiology of EIB in children. Although exercise can trigger classic symptoms of asthma, in children symptoms can be subtle and nonspecific; parents, children, and clinicians often do not recognize EIB. With an age-adjusted protocol, an exercise challenge test can be performed in children as young as 3 years of age. However, an alternative challenge test is sometimes necessary to assess potential for EIB in children. This review summarizes age-related features of EIB and recommendations for assessing EIB in young children and adolescents.

Early lung disease in cystic fibrosis

Lung disease in patients with cystic fibrosis is characterised by inflammation and recurrent and chronic infections leading to progressive loss in pulmonary function and respiratory failure. Early management of disease results in substantially improved pulmonary function at first testing (at roughly 6 years of age), but the annual decline in pulmonary function tests in older patients has remained unchanged showing how important the early years are in the disease process. Treatment regimens for patients with cystic fibrosis have changed from predominantly symptomatic treatment to preventive or causal (ie, treatments that address the underlying mechanisms of disease) therapeutic interventions. The infant and preschool age (2-5 years) could represent a unique period of opportunity to postpone or even prevent the onset of cystic fibrosis lung disease. We summarise the current knowledge and the methods used to characterise and quantify early lung disease. We discuss treatment strategies including new drugs that are being developed and their potential role in the treatment of early lung disease in patients with cystic fibrosis.

Recurrent respiratory infections caused by a double aortic arch: The diagnostic role of spirometry

A young woman with a clinical history characterized by recurrent respiratory infections, occurring since early infancy, was referred to our hospital. When the patient was a young girl, she underwent sweat chloride test, serum analysis of immunoglobulins, and evaluation of blood lymphocyte subsets; all these diagnostic tests were normal, as well as chest X ray aside from pneumonia episodes. Skin prick tests were positive for several different allergens, and a diagnosis of allergic rhinitis was made. At the age of 11 years, she started to complain of gastroesophageal reflux disease (GERD) symptoms, and a gastroscopy detected a hiatal hernia with esophagitis. Despite pharmacologic treatments for allergic rhinitis and GERD, the patient continued to complain of chronic cough, associated with choking and recurrent respiratory infections treated with antibiotic therapy. For the first time in her life, we performed a spirometry that showed a flow-volume curve characterized by a plateau in the expiratory phase, suggestive of an central airway obstruction. Bronchoscopy demonstrated a compression of the distal portion of trachea. Computed tomography (CT) angiogram revealed a double aortic arch. Barium enhancement evidenced an esophageal compression. A surgical division of the smaller of the two arches was then performed. Therefore, we strongly suggest to perform lung function tests in all cases of unexplained respiratory complaints.

Lower-limb endurance training program influences thoracoabdominal motion of patients with COPD?

INTRODUCTION: Thoracoabdominal-TA asynchrony is an important sign of Chronic Obstructive Pulmonary Disease (COPD). Studies investigating the influence of endurance training on TA asynchrony have not been found. OBJECTIVE: To analyze lower-limb endurance training effects on TA asynchrony in patients with COPD. MATERIALS AND METHODS: Two patients with severe COPD were evaluated in a single-subject design AB (A-baseline for six weeks, B-training on cycle ergometer with intensity of 70% of baseline peak load, for 12 weeks) with repeated measures of variables: phase inspiratory relation (PhRIB), phase expiratory relation (PhREB) and phase angle (PhAng). These variables were assessed by respiratory inductive plethysmography during incremental exercise tests on a cycle ergometer (same load and peak load of each test). Statistical methods included visual analysis, two-standard deviation band test and split middle line test, considering significant p < 0.05. It was considered the results for variables with agreement of at least two analyses. Data are presented as mean ± SD for phases A and B. RESULTS: During phase B, Patient 1 presented significant decrease of PhRIB (22.7 ± 3.4 x 17.0 ± 4.9) and PhAng (16.5 ± 5.1 x 13.2 ± 2.1) for same load and PhREB (16.8 ± 3.1 x 13.3 ± 3.1) and PhAng (23.4 ± 1.7 x 20.1 ± 2.3) at peak load. Patient 2 showed significant decrease of PhRIB for same load and (14.4 ± 3.8 x 13.9 ± 3.9) at peak load (19.1 ± 2.5 x 15.7 ± 2.7). CONCLUSIONS: These results suggest that lower-limb endurance training reduced TA asynchrony in patients with severe COPD. The findings may be related, according to the literature, to the lower ventilatory demand and greater exercise capacity of patients with COPD undergoing endurance training.

Comparison of Reference Values and Short-Term Variability for Oscillatory and Spirometric Lung Function in Healthy Korean Preschool Children

Respiratory function measurements are important in the diagnosis and follow-up assessment of respiratory diseases. The aims of this study were to establish reference values for spirometry, to compare them with respiratory resistance and impedance by an impulse oscillometry system (IOS), and to analyze 3-month follow-up studies in healthy Korean preschool children. Six hundred seven questionnaires were distributed and 497 (82%) were returned. Lung function tests were performed in 183 healthy children of the age of 3-6 years. The 3-month follow-up studies were conducted from 19 children who visited our clinic twice. Of the 183 children who underwent both IOS and spirometry, 164 (90%) and 150 (82%) met the quality-control criteria for IOS and spirometry, respectively. The regression equations of each spirometric parameter were obtained. Height was the most consistently correlated measurement in both boys and girls. All spirometry parameters, except for FEF_25-75/FVC, were significantly correlated with IOS parameters. There were no significant differences in respiratory resistance at 5 Hz measured by IOS (Rrs_IOS5), forced vital capacity (FVC), and forced expiratory volume in 1 s (FEV₁) between the first and second sets. The intraclass correlation coefficients and relative coefficients of repeatability for FEV₁, Rrs_IOS5, and respiratory system reactance (Xrs)_IOS5 were 0.90 (95% CI 0.73-0.96), 0.82 (95% CI 0.53-0.93), and 0.55 (95% CI -0.17-0.83) and 22.6%, 35.5%, and 91.8%, respectively. The obtained values and regression equations provide a reference for Korean preschool children and may be of importance in evaluating lung function of preschool children with pulmonary problems. Respiratory resistance and FEV₁ for healthy young Korean children are lower than literature reported reference values for Caucasian children. Rrs_IOS5 appears to be more stable on repeat testing than Xrs_IOS5.

Predicting persistence of asthma in preschool wheezers: crystal balls or muddy waters?

Since preschool wheezing is the common expression of several heterogeneous disorders, identification of children at risk for persistent asthma is particularly challenging. To date, efforts to predict the outcome of preschool wheeze have mainly relied on predictive rules consisting of simple clinical and laboratory parameters. Among these tools, the asthma predictive index (API) has been introduced in international guidelines and position papers and is recommended for use in clinical practice. This article reviews the currently available asthma predictive models focusing on their validity and performance characteristics. Although these tools are generally simple and easy to apply, they suffer important intrinsic and practical limitations and they have been insufficiently validated to allow for widespread use in clinical settings. We also present evidence that their ability to predict the long-term outcome of preschool wheeze is limited in general populations, and even poorer in high-risk children in which prediction of asthma persistence might have important clinical and prognostic implications. Due to the complex and multifactorial nature of asthma, prediction of asthma persistence based on simple clinical models is practically impossible.

Multiple breath nitrogen washout: a feasible alternative to mass spectrometry

BACKGROUND

The lung clearance index (LCI), measured by multiple breath washout (MBW), reflects global ventilation inhomogeneity and is a sensitive marker of early cystic fibrosis (CF) lung disease. Current evidence is based on a customized mass spectrometry system that uses sulfur hexafluoride (SF6) as a tracer gas, which is not widely available. Nitrogen (N2) washout may be better suited for clinical use and multi-center trials.

OBJECTIVE

To compare the results obtained from a N2 washout system to those generated by the SF6 based system in healthy children and children with CF.

METHODS

Children with CF were recruited from outpatient clinics; healthy children were recruited from the Research4Kids online portal. Participants performed MBWSF6 (Amis 2000, Innovision, Denmark) and MBWN2 (ExhalyzerD, EcoMedics, Switzerland) in triplicate, in random order on the same day. Agreement between systems was assessed by Bland-Altman plot.

RESULTS

Sixty-two healthy and 61 children with CF completed measurements on both systems. In health there was good agreement between systems (limits of agreement -0.7 to 1.9); on average N2 produced higher values of LCI (mean difference 0.58 (95% CI 0.42 to 0.74)). In CF the difference between systems was double that in health with a clear bias towards disproportionately higher LCIN2 compared to LCISF6 at higher mean values of LCI.

CONCLUSION

LCIN2 and LCISF6 have similar discriminative power and intra-session repeatability but are not interchangeable. MBWN2 offers a valid new tool to investigate early obstructive lung disease in CF, but requires independent normative values.

Use of impulse oscillometry system in assessment of asthma severity for preschool children

OBJECTIVE

The National Asthma Education and Prevention Program/Expert Panel Report (NAEPP/EPR)-3 Guidelines for asthma treatment categorize asthma severity based on impairment and risks and on medications administered. The objective of this study was to determine whether impulse oscillometry system (IOS) measures in preschool children are consistent with asthma severity as defined by NAEPP/EPR-3 Guidelines.

METHODS

Asthma severity of the 162 subjects (aged 2-5 years) was classified by impairment and risks for exacerbations requiring oral systemic corticosteroids, by medication usage, and by combination classification (higher severity of impairment and risks or medication usage). An experienced pediatrician determined the appropriate medications for each child and parents completed structured questionnaires regarding day and night symptoms and interference with normal activity over the preceding 4 weeks. All children were tested by IOS.

RESULTS

The mean age was 3.7 ± 0.9 years and 91 (56%) of the total patients were males. When asthma severity was based on (1) impairment and risks and (2) medication usage, asthma was "intermittent" in 17.9% and 11.1% of the total patients, "mild persistent" in 42.0% and 50.6% of total patients, and "moderate-severe persistent" in 40.1% and 38.3% of total patients, respectively. The agreement between severity based on impairment and risks and medication usage was not significant. Xrs(5) z-scores differed between intermittent asthma and mild/moderate-severe persistent asthma, as determined by medication usage and combination classification, but not by impairment and risks. As asthma severity (assessed by medication usage) increased, the duration of asthma increased.

CONCLUSIONS

Xrs(5) can be used to discriminate intermittent and persistent asthma in preschool children. Further studies with larger sample sizes are warranted to confirm this finding and to determine the underlying mechanism.

An approach to preschool wheezing: to label as asthma?

Asthma is considered a chronic disease, but not all preschool wheezing is asthma since most will eventually grow out of their symptoms. Although still a matter of debate, preschool wheezing can be classified in 2 major groups: virus-induced wheezing and multitrigger wheezing, having a different prognosis and a different treatment approach. Virus-induced wheezing is the most common phenotype of preschool wheezing and is usually associated with a good prognosis. Treatment should be conservative, but if preventive treatment is required, leukotriene-receptor antagonists might be the first choice treatment. Multitrigger wheezing is associated with an allergic disposition and has a higher risk of persistent symptoms. Inhaled corticosteroids may give short-term reduction in exacerbations, but the beneficial effect of long-term use of inhaled corticosteroids and other anti-inflammatory agents have not yet been established. This review aims to give an opinion on preschool wheezing, and its association with asthma.

Interpretation of pediatric lung function: impact of ethnicity

RATIONALE

To evaluate the appropriateness of spirometric and plethysmographic reference equations in healthy young children according to ethnic origin.

METHODS

Spirometry data were collated in 400 healthy children (214 Black and 186 White) aged 6-12 years. Of these children, 68 Black and 115 White children also undertook plethysmography. Results were expressed as percent predicted according to commonly used equations for spirometry and plethysmography.

RESULTS

Black children had lower lung function for a given height compared to White children. The magnitude and direction of these differences varied according to specific outcome. In the studied age range (6-12 years) the ethnic-specific Wang equations were adequate for spirometry (mean results approximating 100% predicted in both ethnic groups). By contrast, significant differences were found between observed and % predicted plethysmographic lung volumes according to published equations derived from White children: Among the Black children, function residual capacity (FRC) and total lung capacity (TLC) were on average, 14 and 6% lower than predicted, whereas mean residual volume (RV) and RV/TLC were 4 and 10% higher. Among White children, the Rosenthal equations gave the best fit, with the exception of FRC which was, on average, 9% lower than predicted.

CONCLUSION

Spirometry equations may suffice in Black children; however, interpretation of static lung volumes in Black children is limited due to inappropriate reference equations. More appropriate plethysmographic reference equations that are applicable to all ethnic groups across the entire age range are urgently needed.

Lungenfunktionsdiagnostik

Lungenfunktionsdiagnostik beinhaltet eine Vielzahl von Messmethoden, mit denen jeweils bestimmte Qualitten der Lungen in verschiedenen Altersgruppen überwiegend nichtinvasiv untersucht werden können.

Pulmonary function tests in emergency department pediatric patients with acute wheezing/asthma exacerbation

Background. Pulmonary function tests (PFT) have been developed to analyze tidal breathing in patients who are minimally cooperative due to age and respiratory status. This study used tidal breathing tests in the ED to measure asthma severity. Design/Method. A prospective pilot study in pediatric patients (3 to 18 yrs) with asthma/wheezing was conducted in an ED setting using respiratory inductance plethysmography and pneumotachography. The main outcome measures were testing feasibility, compliance, and predictive value for admission versus discharge. Results. Forty patients were studied, of which, 14 (35%) were admitted. Fifty-five percent of the patients were classified as a mild-intermittent asthmatic, 30% were mild-persistent asthmatics, 12.5% were moderate-persistent asthmatics, and 2.5% were severe-persistent. Heart rate was higher in admitted patients as was labored breathing index, phase angle, and asthma score. Conclusions. Tidal breathing tests provide feasible, objective assessment of patient status in the enrolled age group and may assist in the evaluation of acute asthma exacerbation in the ED. Our results demonstrate that PFT measurements, in addition to asthma scores, may be useful in indicating the severity of wheezing/asthma and the need for admission.

Pressões respiratórias máximas de pico e sustentada na avaliação da força muscular respiratória de crianças

OBJETIVOS: comparar os valores de PImax e PEmax de pico e sustentado em uma população de crianças em idade escolar. MÉTODOS: estudo observacional descritivo de caráter transversal. Foram avaliadas 144 crianças saudáveis de 7 a 11 anos de ambos os gêneros. Foirealizada avaliação antropométrica e mensuraçãodas pressões respiratórias máximas, de pico e sustentada, através do manovacuômetro digital. A criança sorteou qual pressão respiratória iria realizar inicialmente. A medida da PImax foi realizada a partir da capacidade pulmonar total e a medida da PEmax a partir do volume residual. Os dados foram analisados através do programa SPSS 17.0 atribuindose o nível de significância de 5%. RESULTADOS: os achados obtidos foram: 78,53 ± 22,53 cmH2O para PIpico ; 91,11 ± 23,0 cmH2O para a PEpico e 72,95 ± 21,22 cmH2O e 86,25 ± 21,8 cmH2O para PIsust e PEsust, respectivamente. Osvalores obtidos através das pressões respiratórias de pico (PIpico e PEpico) foram significativamente superiores as medidas obtidas para as pressões respiratórias sustentadas (PIsust e PEsust) independentemente do gênero ou idade avaliada (p=0,001). CONCLUSÕES: a utilização de medidas de pico na avaliação das pressões respiratórias máximas, mais facilmente obtidas na prática clínica, pode comprometer a real mensuração da força muscular respiratória em crianças de 7 a 11 anos.

Variability of a closed, rebreathing setup for multiple breath wash-out testing in children

OBJECTIVE

The multiple breath wash-out technique (MBW) that measures lung clearance index (LCI) and functional residual capacity (FRC) may be more sensitive than spirometry for identification of early obstructive airways disease. The open MBW setup using mass spectrometry referenced in previous publications is not readily available in the U.S. Our objective was to assess validity and sensitivity of a commercially available device that uses a closed (rebreathing) setup with photoacoustic spectroscopy for MBW testing.

STUDY DESIGN AND METHODS

Subjects aged 5-21 who were either healthy or had a history of cystic fibrosis were enrolled. Subjects completed MBW (Innocor device; Innovision, Denmark) and spirometry; measures obtained included LCI, FRC, and forced expiratory volume in 1 sec, as well as changes in end-tidal carbon dioxide levels (CO(2) ) and tidal volume during MBW testing.

RESULTS

Seventeen subjects attempted a total of 76 MBW maneuvers; 80% were completed and 60% met criteria for acceptability; most were unacceptable due to errors in the tracer gas curve. Substantial intra-subject variability for LCI and FRC were noted (mean 26% ± 55 and 36% ± 63, respectively). Subjects were also noted to have significant increases in exhaled CO(2) and tidal volume during MBW testing.

CONCLUSIONS

In our initial experience using a commercially available closed setup for MBW testing, we found a significant degree of intra-subject variability leading us to suspend testing. Variability could be due to hypercapnea and instability of tidal breathing secondary to the rebreathing setup. Further studies are needed to better understand the closed system MBW setup.

Assessment of airflow limitation, airway inflammation, and symptoms during virus-induced wheezing episodes in 4- to 6-year-old children

Background

It is disputed whether recurrent episodes of wheeze in preschool-aged children comprise a distinct asthma phenotype.

Objective

We sought to prospectively assess airflow limitation and airway inflammation in children 4 to 6 years old with episodic virus-induced wheeze.

Methods

Ninety-three children 4 to 6 years old with a history of mild, virus-induced episodes of wheeze who were able to perform acceptable fraction of exhaled nitric oxide (Feno) maneuvers and spirometry (with forced expiratory time ≥0.5 seconds) were followed prospectively. Lung function and Feno values were measured every 6 weeks (baseline) within the first 48 hours of an acute wheezing episode (day 0) and 10 and 30 days later. Symptom scores and peak flow measurement were recorded daily.

Results

Forty-three children experienced a wheezing episode. At day 0, Feno values were significantly increased, whereas forced expiratory volume at 0.5 seconds (FEV_0.5) significantly decreased compared with baseline (16 ppb [interquartile range {IQR}, 13-20 ppb] vs 9 ppb IQR, 7-11 ppb] and 0.84 L [IQR, 0.75-0.99 L] vs 0.99 L [IQR, 0.9-1.07 L], respectively; both P < .001). Airflow limitation at day 0 was reversible after bronchodilation. FEV_0.5 and Feno values were significantly associated with each other and with lower and upper respiratory tract symptoms when assessed longitudinally but not cross-sectionally at all time points independently of atopy. Feno and FEV_0.5 values returned to baseline levels within 10 days.

Conclusions

Mild episodes of wheeze in preschoolers are characterized by enhanced airway inflammation, reversible airflow limitation, and asthma-related symptoms. Feno values increase significantly during the first 48 hours and return to personal baseline within 10 days from the initiation of the episode. Longitudinal follow-up suggests that symptoms, inflammation, and lung function correlate well in this phenotype of asthma.

The importance of imaging and physiology measurements in assessing the delivery of peripherally targeted aerosolized drugs

Considerable recent effort has been directed towards developing new aerosol formulations and delivery devices that can target drugs to the lung periphery. In order to determine the efficacy of targeted drug therapy, it is essential that the peripheral lung region be adequately assessed. Imaging of the airways structure and pathology has greatly advanced in the last decade and this rate of growth is accelerating as new technologies become available. Lung imaging continues to play an important role in the study of the peripheral airways and, when combined with state-of-the-art lung function measurements and computational modeling, can be a powerful tool for investigating the effects of inhaled medication. This article focuses on recent strategies in imaging and physiological measurements of the lungs that allow the assessment of inhaled medication delivered to the periphery and discusses how these methods may help to further optimize and refine future aerosol delivery technology.

Increased airway smooth muscle in preschool wheezers who have asthma at school age

BACKGROUND

Increased airway smooth muscle (ASM) is a feature of established asthma in schoolchildren, but nothing is known about ASM in preschool wheezers.

OBJECTIVE

We sought to determine endobronchial biopsy specimen ASM area fraction in preschool wheezers and its association with asthma at school age.

METHODS

ASM area, reticular basement membrane thickness, and mucosal eosinophil and ASM mast cell values were quantified in endobronchial biopsy specimens previously obtained from preschool children undergoing clinically indicated bronchoscopy: severe recurrent wheezers (n=47; median age, 26 months) and nonwheezing control subjects (n=21; median age, 15 months). Children were followed up, and asthma status was established at age 6 to 11 years. Preschool airway pathology was examined in relation to asthma at school age.

RESULTS

Forty-two (62%) of 68 children had 1 or more evaluable biopsy specimens for ASM. At school age, 51 of 68 children were followed up, and 15 (40%) of 37 preschool wheezers had asthma. Children who had asthma and an evaluable biopsy specimen had increased preschool ASM area fraction (n=8; median age, 8.2 years [range, 6-10.4 years]; median ASM, 0.12 [range, 0.08-0.16]) compared with that seen in children without asthma (n=24; median age, 7.3 years [range, 5.9-11 years]; median ASM, 0.07 [range, 0.02-0.23]; P=.007). However, preschool reticular basement membrane thickness and mucosal eosinophil or ASM mast cell values were not different between those who did or did not have asthma at school age.

CONCLUSION

Increased preschool ASM is associated with those children who have asthma at school age. Thus a focus on early changes in ASM might be important in understanding the subsequent development of childhood asthma.

Spirometry and forced oscillations in the detection of airway hyperreactivity in asthmatic children

BACKGROUND

Provocation tests are routinely used to detect airway hyperreactivity (AH) in the diagnosis of asthma. We compared the sensitivities of the forced oscillation technique (FOT) and spirometry in the detection of AH in asthmatic children.

METHODS

FOT and spirometry were performed in 20 asthmatic children (aged 5-18 years) following aerosolized histamine and methacholine at an interval of 2 weeks. The respiratory system input impedance was measured by FOT; the resistance at 6 Hz (R(6) ), the average resistance between 4 and 24 Hz, the area under the reactance curve (AX) and the resonant frequency were extracted from these recordings. Spirometry was used to obtain forced expiratory volumes and flow parameters.

RESULTS

Following provocation with the two agonists, the FOT detected the airway response as early as spirometry. When the greater variability of the impedance parameters was taken into account, the two methods were observed to have similar sensitivities. Among the lung function parameters studied, AX and R(6) were the most sensitive for the demonstration of AH.

CONCLUSIONS

Our findings demonstrate that FOT is as suitable as spirometry for the measurement of bronchoconstriction and thus it may be considered for the detection of AH in asthmatic children. Since its application requires minimal cooperation, this approach imposes less stress and may be particularly favorable in the diagnosis of asthma at a young age.

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.

Maternal plasma phosphatidylcholine fatty acids and atopy and wheeze in the offspring at age of 6 years

Variation in exposure to polyunsaturated fatty acids (PUFAs) might influence the development of atopy, asthma, and wheeze. This study aimed to determine whether differences in PUFA concentrations in maternal plasma phosphatidylcholine are associated with the risk of childhood wheeze or atopy. For 865 term-born children, we measured phosphatidylcholine fatty acid composition in maternal plasma collected at 34 weeks' gestation. Wheezing was classified using questionnaires at 6, 12, 24, and 36 months and 6 years. At age of 6 years, the children underwent skin prick testing, fractional exhaled nitric oxide (FENO) measurement, and spirometry. Maternal n-6 fatty acids and the ratio of n-3 to n-6 fatty acids were not associated with childhood wheeze. However, higher maternal eicosapentaenoic acid, docosahexaenoic acid, and total n-3 fatty acids were associated with reduced risk of non-atopic persistent/late wheeze (RR 0.57, 0.67 and 0.69, resp. P = 0.01, 0.015, and 0.021, resp.). Maternal arachidonic acid was positively associated with FENO (P = 0.024). A higher ratio of linoleic acid to its unsaturated metabolic products was associated with reduced risk of skin sensitisation (RR 0.82, P = 0.013). These associations provide some support for the hypothesis that variation in exposure to n-6 and n-3 fatty acids during pregnancy influences the risk of childhood wheeze and atopy.