Reference values for spirometry in preschool children

Development and validation of predictive equations for spirometry in Portuguese children

Background

There are no data on lung function reference values for Portuguese children, and the contribution from the Portuguese data set in the Global Lung Function Initiative (GLI) is scant.

Objectives

We aimed to estimate new up-to-date reference values for Portuguese children by fitting a multivariable regression model to a general population sample. Further, we intended to assess the external validity of the obtained reference values and to compare them to the GLI reference values.

Methods

A random sample of 858 children from 20 primary schools were screened by health questionnaire, physical examination, and spirometry. Spirometric parameters recorded were FVC, FEV1, and FEF25-75. Multiple regression models were used to derive reference equations.

Results

Overall, 481 children, aged between 7 and 12 years, 267 boys (55.5%), were included. Boys had higher values for FVC and FEV1 than girls (P < .05). The strongest correlation was found for FVC with height (r = 0.71 for boys and 0.70 for girls), while the lowest correlation was observed in both sexes for FEF25-75 with age (r = 0.23). Height was the most significant predictor of FVC, FEV1, and FEF25-75 in our models. Weight and body mass index were not significant predictors for boys but had a significant effect on girls' equations for all spirometry parameters. Compared to obtained reference equations with GLI, they performed better for FVC in boys, FEV1 in girls, and FEF25-75 in both boys and girls.

Conclusion

We offer up-to-date reference values of spirometry for Portuguese children that can be used in clinical practice and research.

Lung Function in Preschool Children in Low and Middle Income Countries: An Under-Represented Potential Tool to Strengthen Child Health

BACKGROUND

The burden of respiratory disease is high in low-middle income countries (LMIC). Pulmonary function tests are useful as an objective measure of lung health and to track progression. Spirometry is the commonest test, but its use is limited in preschool children. Other lung function methods have been developed but their use in LMIC has not been well described.

AIM

To review the use of preschool lung function testing in children in LMIC, with particular reference to feasibility and clinical applications.

METHODS

Electronic databases "PubMed", "Scopus"," Web of Science", and "EBSCO host" were searched for publications in low and middle income countries on preschool lung function testing, including spirometry, fractional exhaled nitric oxide (FeNO), oscillometry, interrupter technique, tidal breathing and multiple breath washout (MBW), from 1 January 2011 to 31 January 2022. Papers in English were included and those including only children ≥6 years were excluded.

RESULT

A total of 61 papers from LMIC in Asia, South America, Africa, Eurasia or the Middle East were included. Of these, 40 included spirometry, 7 FeNO, 15 oscillometry, 2 interrupter technique, and 2 tidal breathing. The papers covered test feasibility (19/61), clinical application (46/61) or epidemiological studies (13/61). Lung function testing was successful in preschool children from LMIC. Spirometry was the most technically demanding and success gradually increased with age.

CONCLUSION

Preschool lung function testing is under-represented in LMIC for the burden of respiratory disease. These tests have the potential to strengthen respiratory care in LMIC, however access needs to be improved.

Which factors can influence the number of forced expiratory manoeuvres on spirometry in schoolchildren?

INTRODUCTION

Spirometry is of great value for understanding respiratory function and management of lung diseases. Adaptations in the exam were made to meet paediatric population since the forced expiratory manoeuvres (FEM) present in the exam require effort and cooperation; therefore, its use should be reconsidered.

OBJECTIVE

To analyse factors that may influence the number of FEM required for successful spirometry in schoolchildren.

METHOD

Healthy children aged between 6 and 12 years were tested. FEM were conducted according to the American Thoracic Society/European Respiratory Society guideline. The children were divided into three groups according to the number of attempts: G3M if child completed the test in three FEM; G4M if child completed in four attempts FEM; and G5/8M if child completed the test in five to eight FEM. Factors that potentially influenced the number of FEM included: age; impulse oscillometry parameters; slow vital capacity; respiratory muscle strength; orofacial motor function, school performance, physical activity level and quality of life. The Kolmogorov-Smirnov test was performed, followed by the Chi-Square, repeated measures ANOVA and Kruskal-Wallis tests; thereafter, a multinomial logistic regression was applied.

RESULTS

One hundred and forty-nine schoolchildren (80 girls) with mean age of 9.13 years (±1.98) were included, age was related to the required number of FEM (F = 3.38(2), P = .03) and children with poor school performance had a 2.84-fold greater chance of completing the exam in more than five attempts.

CONCLUSION

Age and school performance influenced the number of FEM required for a successful spirometry in schoolchildren.

Applicability of GLI 2012 spirometry equation among preschool aged Jordanian

OBJECTIVES

The Validation of Global Lung Initiative (GLI 2012) equations is required prior to their application in clinical practice in different regions. This study validated the GLI 2012 equations in Middle Eastern preschool aged children, which was not previously conducted.

STUDY DESIGN

Spirometry measures were collected from 765 (54% males) healthy 3 to 5-year-old Jordanian children. z scores, percent predicted values, and frequency of measures below lower limit than normal (LLN) were calculated using GLI 2012 equations for Caucasians and Other or Mixed.

RESULTS

The mean of z-scores produced by GLI 2012 equation for Caucasians in FEV_0.75, FEV₁, FVC, FEV₁/FVC% and FEF25-75 in boys were 0.03, 0.02, -0.13, 0.26 and -0.08 respectively, while in girls it was -0.03, 0.01, 0.02, -0.01 and -0.04 respectively, and the mean of z-scores produced by GLI-2012 Other or Mixed equations in FEV₁, FVC, FEV₁/FVC% and FEF25-75 in boys were 0.56, 0.51, 0.09 and 0.12 respectively, and in girls it was 0.56, 0.67, -0.22 and 0.18 respectively. The frequency of measures below LLN as produced by Caucasians equation were not significantly different from the expected 5% in any of the spirometry parameters.

CONCLUSION

The GLI 2012 for Caucasians is a reasonable fit for Jordanian preschool aged children.

RELATIONS BETWEEN ASTHMA AND OBESITY: AN ANALYSIS OF MULTIPLE FACTORS

OBJECTIVE

Asthma and obesity are prevalent and interrelated diseases. In the pediatric population, the effect of systemic inflammation associated to obesity, leading to inflammation of the airways, is currently controversial. Our aim was to compare inflammatory, clinical and spirometric patterns between children with asthma and obesity and those within the normal weight status range.

METHODS

A total of 79 boys and girls from 6 to 10 years old were selected and divided into four groups: obese asthmatics, non-obese asthmatics, obese non-asthmatics, and non-obese non-asthmatics. In addition to collecting clinical and anthropometric data, all children underwent spirometry and skin prick tests for inhalant allergens. Blood samples for measurement of cytokines and adipokines were also collected.

RESULTS

Obese asthmatics had significantly worse control of asthma than non-obese asthmatics (OR 4.9; 95%CI 1.1‒22.1), regardless of sex, physical activity and atopy. No differences in spirometry, Th1 and Th2 cytokines and adipokines levels were observed among the four groups. The prick tests were positive in 81.8 and 80% of non-obese asthmatics and obese asthmatics, respectively.

CONCLUSIONS

The degree of control of asthma was significantly lower in the obese group, regardless of the findings of no differences in spirometry. Extra-pulmonary factors could be responsible for this symptomatic profile. High positivity of skin test in both groups, which is considered a good marker of atopy, shows a preponderant atopic component in the genesis of asthma, both in children with obesity and in those within the normal weight status.

Reference values for spirometry in Brazilian children

Objective:

To generate reference values for spirometry in Brazilian children 3-12 years of age and to compare those values with the values employed in the equations currently in use in Brazil.

Methods:

This study involved healthy children, 3-12 years of age, recruited from 14 centers (primary data) and spirometry results from children with the same characteristics in six databases (secondary data). Reference equations by quantile regressions were generated after log transformation of the spirometric and anthropometric data. Skin color was classified as self-reported by the participants. To determine the suitability of the results obtained, they were compared with those predicted by the equations currently in use in Brazil.

Results:

We included 1,990 individuals from a total of 21 primary and secondary data sources. Of those, 1,059 (53%) were female. Equations for FEV₁, FVC, the FEV₁/FVC ratio, FEF between 25% and 75% of the FVC (FEF_25-75%) and the FEF_25-75%/FVC ratio were generated for white-, black-, and brown-skinned children. The logarithms for height and age, together with skin color, were the best predictors of FEV₁ and FVC. The reference values obtained were significantly higher than those employed in the equations currently in use in Brazil, for predicted values, as well as for the lower limit of normality, particularly in children with self-reported black or brown skin.

Conclusions:

New spirometric equations were generated for Brazilian children 3-12 years of age, in the three skin-color categories defined. The equations currently in use in Brazil seem to underestimate the lung function of Brazilian children 3-12 years of age and should be replaced by the equations proposed in this study.

Comparison of breath sampling methods: a post hoc analysis from observational cohort studies

In this report, we present a post hoc analysis from two observational cohorts, comparing the global breath volatile profile captured when using polymer sampling bags (mixed breath) versus Bio-VOC™ (alveolar breath). The cohorts were originally designed to characterize the breath volatile profiles of Malawian children with and without uncomplicated falciparum malaria. Children aged 3-15 years were recruited from ambulatory pediatric centers in Lilongwe, Malawi. Breath sampling was carried out two months apart (one study using a Bio-VOC™ and the second using sampling bags), and all samples were analyzed by gas chromatography/mass spectrometry. The efficacy of breath collection was assessed by quantifying levels of two high prevalence breath compounds, acetone and isoprene, as well as determining the overall number of breath compounds collected and their abundance. We found that the mean number of volatiles detected using sampling bags was substantially higher than when using the Bio-VOC™ (137 vs. 47). Breath collection by Bio-VOC™ also yielded reduced levels of endogenous breath volatiles, isoprene and acetone, even after breath volume correction. This suggests that the Bio-VOC™ dilutes the volatiles and introduces dead air or ambient air. Our results suggest that sampling bags are better suited for biomarker discovery and untargeted search of volatiles in pediatric populations, as evidenced by superior breath volatile detection.

Lung function growth trajectories in non-asthmatic children aged 4-9 in relation to prenatal exposure to airborne particulate matter and polycyclic aromatic hydrocarbons - Krakow birth cohort study

BACKGROUND

Patterns of lung function development during childhood can be helpful in understanding the pathogenesis of respiratory diseases. A variety of environmental and lifestyle factors, present from the prenatal period to adulthood, may affect or modulate lung function growth. The aim of this study was to investigate, the associations between individual growth trajectories of children's lung function during childhood and prenatal exposure to airborne fine particulate matter (PM_2.5) and polycyclic aromatic hydrocarbons (PAH), which were hypothesized to adversely affect spirometry parameters.

MATERIAL AND METHODS

The study group comprised 294 non-asthmatic, full term children from the Krakow birth cohort, who underwent annual spirometry testing at the ages of 4-9 years. Individual personal air monitoring of PM_2.5 and PAH were performed over 48 h in the second trimester of pregnancy. Possible confounders or modifiers such as child's gender, height, atopic status and exposure to environmental tobacco smoke (ETS) were considered. Polynomial multilevel mixed models were used to assess the growth rates of children's lung functions.

RESULTS

Lung function trajectories differed significantly for boys and girls for FVC, FEV1 and FEF25-75. Girls had lower rates of increase than boys: - 20.5 (95%CI: - 32.4; - 8.6) ml/year (FVC); - 19.9 (95%CI: -30.7;-9.0) ml/year (FEV1); and - 32.5 (95%CI: - 56.9; - 8.2) ml/year (FEF25-75). Spirometry functions increased with age; however the growth rate decelerated over time. Significant lung function impairment (lower FVC and FEV1 levels) was observed from 4 to 9 years among subjects prenatally exposed to higher levels of PM_2.5 as well as PAH, but not in the case of FEF25-75. No significant differences were observed in the rates of increase over time in relation to prenatal PM_2.5 and PAH exposure.

CONCLUSION

Our results indicate that in non-asthmatic children high prenatal exposure to airborne PM_2.5 and PAH is associated with lower trajectories of FVC and FEV1, but not the rate of increase over time, suggesting that the initial effect is not diminishing in time.

SPIROMETRY IN SCHOOLCHILDREN FOR FIELD STUDIES: DOES TESTING ON DIFFERENT DAYS CHANGE THE RESULT OF THE EXAM?

OBJECTIVE

To analyze if there is variation in the results of spirometry performed by healthy schoolchildren on different days.

METHODS

Cross-sectional study with healthy schoolchildren aged 7 to 12 years old, in Florianópolis, Santa Catarina, Southern Brazil. Prepubescent children, non-athletes, born at full term, without cardiorespiratory, rheumatic, musculoskeletal, neurological and visual or hearing deficit were included. The child's health was assessed by a health questionnaire and by the survey International Study of Asthma and Allergies in Childhood. The spirometric test was performed on 3 different days, not exceeding the interval of 15 days between the first and last exams, following the guidelines of the American Thoracic Society. The absolute values and percentages of predicted values of forced vital capacity, forced volume in the first second and peak expiratory flow were analyzed. Statistical analysis was performed using the Shapiro-Wilk normality test followed by one-way analysis of variance or Friedman test and by Bonferroni's post-hoc test for multiple parametric comparisons. Also, the intraclass correlation coefficient was applied to compare results on the same patients on the different tested days.

RESULTS

Twenty-two children were analyzed, with a mean age of 9.3±1.1 years. All the spirometric parameters showed a reduction in absolute value after the first exam, but without significant difference. Regarding reproducibility of spirometry results, the tests presented intraclass correlation coefficient >0.70.

CONCLUSIONS

There was no change in the results of spirometry performed by healthy schoolchildren on three different days.

Bronchodilator response cut-off points and FEV 0.75 reference values for spirometry in preschoolers

OBJECTIVE:

To determine the cut-off points for FEV1, FEV0.75, FEV0.5, and FEF25-75% bronchodilator responses in healthy preschool children and to generate reference values for FEV0.75.

METHODS:

This was a cross-sectional community-based study involving children 3-5 years of age. Healthy preschool children were selected by a standardized questionnaire. Spirometry was performed before and after bronchodilator use. The cut-off point of the response was defined as the 95th percentile of the change in each parameter.

RESULTS:

We recruited 266 children, 160 (60%) of whom were able to perform acceptable, reproducible expiratory maneuvers before and after bronchodilator use. The mean age and height were 57.78 ± 7.86 months and 106.56 ± 6.43 cm, respectively. The success rate for FEV0.5 was 35%, 68%, and 70% in the 3-, 4-, and 5-year-olds, respectively. The 95th percentile of the change in the percentage of the predicted value in response to bronchodilator use was 11.6%, 16.0%, 8.5%, and 35.5% for FEV1, FEV0.75, FEV0.5, and FEF25-75%, respectively.

CONCLUSIONS:

Our results provide cut-off points for bronchodilator responsiveness for FEV1, FEV0.75, FEV0.5, and FEF25-75% in healthy preschool children. In addition, we proposed gender-specific reference equations for FEV0.75. Our findings could improve the physiological assessment of respiratory function in preschool children.

OBJETIVO:

Determinar os pontos de corte de resposta ao broncodilatador do VEF1, VEF0,75, VEF0,5 e FEF25-75% em crianças pré-escolares saudáveis e gerar valores de referência para o VEF0,75.

MÉTODOS:

Foi realizado um estudo transversal de base comunitária em crianças de 3-5 anos de idade. Pré-escolares saudáveis foram selecionados por um questionário padronizado. Foi realizada espirometria antes e depois do uso de broncodilatador. Foram definidos os pontos de corte dessa resposta como o percentil 95 de variação em cada parâmetro.

RESULTADOS:

Foram recrutadas 266 crianças, e 160 (60,0%) foram capazes de gerar manobras expiratórias aceitáveis e reprodutíveis antes e depois do uso de broncodilatador. As médias de idade e estatura dos participantes foram 57,78 ± 7,86 meses e 106,56 ± 6,43 cm, respectivamente. A taxa de sucesso para o VEF0,5 foi de 35%, 68% e 70%, respectivamente, nos participantes com 3, 4 e 5 anos de idade. O percentil 95 de variação percentual do valor previsto na resposta ao broncodilatador foram, respectivamente, de 11,6%, 16,0%, 8,5% e 35,5%, para VEF1, VEF0,75, VEF0,5 e FEF25-75%.

CONCLUSÕES:

Nossos resultados definiram pontos de corte de resposta ao broncodilatador para o VEF1, VEF0,75, VEF0,5 e FEF25-75 em crianças pré-escolares saudáveis. Adicionalmente, foram propostas equações de referência para o VEF0,75, separadas por sexo. Os achados deste estudo podem melhorar a avaliação fisiológica da função respiratória em pré-escolares.

Prediction equations for spirometry in four- to six-year-old children

OBJECTIVE

To generate prediction equations for spirometry in 4- to 6-year-old children.

METHODS

Forced vital capacity, forced expiratory volume in 0.5s, forced expiratory volume in one second, peak expiratory flow, and forced expiratory flow at 25-75% of the forced vital capacity were assessed in 195 healthy children residing in the town of Sete Lagoas, state of Minas Gerais, Southeastern Brazil. The least mean squares method was used to derive the prediction equations. The level of significance was established as p<0.05.

RESULTS

Overall, 85% of the children succeeded in performing the spirometric maneuvers. In the prediction equation, height was the single predictor of the spirometric variables as follows: forced vital capacity=exponential [(-2.255)+(0.022×height)], forced expiratory volume in 0.5s=exponential [(-2.288)+(0.019×height)], forced expiratory volume in one second=exponential [(-2.767)+(0.026×height)], peak expiratory flow=exponential [(-2.908)+(0.019×height)], and forced expiratory flow at 25-75% of the forced vital capacity=exponential [(-1.404)+(0.016×height)]. Neither age nor weight influenced the regression equations. No significant differences in the predicted values for boys and girls were observed.

CONCLUSION

The predicted values obtained in the present study are comparable to those reported for preschoolers from both Brazil and other countries.