Preschool Lung Function Research Articles

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

BackgroundThe 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.AimTo review the use of preschool lung function testing in children in LMIC, with particular reference to feasibility and clinical applications.MethodsElectronic 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.ResultA 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.ConclusionPreschool 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.

Malignant pleural effusions

may have already occurred, thus providing a rich environment for growth of P. aeruginosa. Nevertheless, the lack of improvement in lung function measures, despite aggressive treatment and apparent eradiation of P. aeruginosa, is concerning. This finding emphasizes the importance of employing preventative therapy before the development of airway inflammation and infection. Driven by detailed work performed in laboratories such as that described in this issue of the Journal, infant lung function testing has now entered a new stage and can be considered a clinical outcome measure, similar to spirometry in the older child. The raised-volume technique has been standardized (12), published reference values are available (14), procedural risks are acceptable, and studies have clearly demonstrated that this technique is suitable to discriminate lung disease from health (3–5). Results from a recently completed trial performed in infants with CF in the United States are encouraging as they demonstrate the feasibility of studying infant lung function in a multicenter setting when strict quality assurance and training is implemented (15). The tremendous progress in this area of measuring infant physiology will naturally lead to intervention studies using these parameters as outcome measures. Over the next decade, we expect that techniques such as infant and preschool lung function testing will not only improve our understanding of the once ‘‘silent’’ and mysterious young CF lung but will also help us to develop stronger evidence for potential early intervention strategies in this vulnerable age group (16).

Prenatal exposure to VOCs and NOx and lung function in preschoolers.

Several studies have shown that exposure to air pollutants affects lung growth and development and can result in poor respiratory health in early life. We included a subsample of 772 Mexican preschoolers whose mothers participated in a Prenatal Omega-3 fatty acid Supplements, GRowth, And Development birth cohort study with the aim to evaluate the impact of prenatal exposure to volatile organic compounds and nitrogen oxides on lung function measured by oscillation tests. The preschoolers were followed until 5 years of age. Anthropometric measurements and forced oscillation tests were performed at 36, 48, and 60 months of age. Information on sociodemographic and health characteristics was obtained during follow up. Prenatal exposure to volatile organic compounds and nitrogen oxides was evaluated using a land use regression models and the association between them was tested using a lineal regression and longitudinal linear mixed effect models adjusting for potential confounders. Overall, the mean (standard deviation) of the measurements of respiratory system resistance and respiratory system reactance at 6, 8, and 10 Hz during the follow-up period was 11.3 (2.4), 11.1 (2.4), 10.3 (2.2) and -5.2 (1.6), -4.8 (1.7), and -4.6 hPa s L-1 (1.6), respectively. We found a significantly positive association between respiratory resistance (βRrs6 = 0.011; 95%CI: 0.001, 0.023) (P < .05) and prenatal exposure to nitrogen dioxide and a marginally negatively association between respiratory reactance (βXrs6 = -11.40 95%CI: -25.26, 1.17 and βXrs8 = -11.91 95%CI: -26.51, 1.43) (P = .07) and prenatal exposure to xylene. Prenatal exposure to air pollutants was significantly associated with the alteration of lung function measured by oscillation tests in these preschool children.

WS06.3 Lung Clearance Index in infants with cystic fibrosis may predict lung function in preschoolers

WS06.3 Lung Clearance Index in infants with cystic fibrosis may predict lung function in preschoolers

Cadherin-related family member 3 gene impacts childhood asthma in Chinese children.

A missense variant (rs6967330) of the gene encoding cadherin-related family member 3 (CDHR3) was associated with recurrent severe exacerbations in pre-schoolers. However, there were limited data on its relationship with pre-school lung function and school-age asthma. This study replicated the association between polymorphic markers at the region of CDHR3 around rs6967330 and wheezing phenotypes in two independent cohorts of Chinese children. Ten tagging SNPs located 10kb around rs6967330 were selected by HaploView 5.0 based on 1000 Genomes database for Southern Han Chinese. Their associations with wheezing and lung function were examined in 1341 Chinese pre-school children, while those for asthma phenotypes were examined in an independent group of 2079 school-age children. Genotypic and haplotypic associations were analyzed by multivariate regression, and generalized multifactor dimensionality reduction was used to examine epistatic interactions for wheezing traits. The mean (SD) age of pre-school cohort was 4.7 (1.0) years. Rs6967330 was associated with current wheeze (odds ratio [OR] 1.63, 95% confidence interval [CI] 1.09-2.43) and its severity (OR 1.64, 95% CI 1.10-2.44) among pre-school children. This SNP was also associated with school-age asthma (OR 1.32, 95% CI 1.04-1.69). The minor allele of rs408223 was associated with lower FEV0.5 (β=-2.411, P=.004) and FEV0.5 /FVC (β=-1.292, P=.015). Lower spirometric indices were also associated with minor allele of rs140154310. GAC haplotype from rs4730125, rs6967330, and rs408223 was associated with pre-school current wheeze and school-age asthma. Epistatic interaction was found between unrelated CDHR3 SNPs for FEV0.5 among pre-schoolers. CDHR3 is a candidate gene for early-life wheezing, school-age asthma, and lung function in Chinese children.

Effect of omega-3 fatty acids supplementation during pregnancy on lung function in preschoolers: a clinical trial

ABSTRACTRationale: Prenatal omega-3 fatty acids improve alveolarization, diminish inflammation, and improve pulmonary growth, but it is unclear whether these outcomes translate into improved postnatal lung function. Objective: We assessed the effect of prenatal supplementation with docosahexaenoic acid (DHA) on offspring lung function through 60 months of age. Methods: We included a cohort of 772 Mexican preschoolers whose mothers participated in a clinical trial (NCT00646360) of supplementation with DHA or a placebo from week 18–22 of gestation through delivery. Measurements: The children were followed after birth and anthropometric measurements and forced oscillation tests were performed at 36, 48, and 60 months of age. The effect of DHA was tested using a longitudinal mixed effect models. Results: Overall, mean (Standard Deviation) of the measurements of respiratory system resistance and respiratory system reactance at 6, 8, and 10 Hz during follow up period were 11.3 (2.4), 11.1 (2.4), 10.3 (2.2) and –5.2 (1.6), –4.8 (1.7), –4.6 (1.6), respectively. There were no significant differences in pulmonary function by treatment group. DHA did not affect the average lung function or the trajectories through 60 months. Conclusions: Prenatal DHA supplementation did not influence pulmonary function in this cohort of Mexican preschoolers.

Validation of Global Lung Function Initiative and All Ages Reference Equations for Forced Spirometry in Healthy Spanish Preschoolers

IntroductionRecent publication of multi-ethnic spirometry reference equations for subjects aged from 3 to 95 years aim to avoid age-related discontinuities and provide a worldwide standard for interpreting spirometric test results. ObjectivesTo assess the agreement of the Global Lung Function Initiative (GLI-2012) and All ages (FEV0.5) reference equations with the Spanish preschool lung function data. To verify the appropriateness of these reference values for clinical use in Spanish preschool children. MethodsSpirometric measurements were obtained from children aged 3–6 years attending 10 randomly selected schools in Barcelona (Spain). Stanojevic's quality control criteria were applied. z-Scores were calculated for the spirometry outcomes based on the GLI equations. If the z-score (mean) of each parameter was close to 0, with a maximum difference of ±0.5 from the mean and a standard deviation of 1, the GLI-2012 equations would be applicable in our population. ResultsOf 543 children recruited, 405 (74.6%) were ‘healthy’, and of these, 380 were Caucasians. Of these 380, 81.6% (169 females, 141 males) performed technically acceptable and reproducible maneuvers to assess FEVt, and 69.5% achieved a clear end-expiratory plateau. z-Scores for FVC, FEV1, FEV1/FVC, FEV0.75, FEV0.75/FVC, FEV0.5, FEF75 and FEF25–75 all fell within ±0.5, except for FEV1/FVC (0.53 z-scores). ConclusionsGLI equations are appropriate for Spanish preschool children. These data provide further evidence to support widespread application of the GLI reference equations.

Validación de las ecuaciones propuestas por la Iniciativa Global de Función Pulmonar (GLI) y las de Todas las Edades para espirometría forzada en preescolares sanos españoles

IntroductionRecent publication of multi-ethnic spirometry reference equations for subjects aged from 3-95 years aim to avoid age-related discontinuities and provide a worldwide standard for interpreting spirometric test results. ObjectivesTo assess the agreement of the Global Lung Function Initiative (GLI-2012) and All ages (FEV0.5) reference equations with the Spanish preschool lung function data. To verify the appropriateness of these reference values for clinical use in Spanish preschool children. MethodsSpirometric measurements were obtained from children aged 3 to 6 years attending 10 randomly selected schools in Barcelona (Spain). Stanojevic's quality control criteria were applied. Z-scores were calculated for the spirometry outcomes based on the GLI equations. If the z-score (mean) of each parameter was close to 0, with a maximum variance of ± 0.5 from the mean and a standard deviation of 1, the GLI-2012 equations would be applicable in our population. ResultsOf 543 children recruited, 405 (74.6%) were ‘healthy’, and of these, 380 were Caucasians. Of these 380, 81.6% (169 females, 141 males) performed technically acceptable and reproducible maneuvers to assess FEVt, and 69.5% achieved a clear end-expiratory plateau. Z-scores for FVC, FEV1, FEV1/FVC, FEV0.75, FEV0.75/FVC, FEV0.5, FEF75 and FEF25-75 all fell within ± 0.5, except for FEV1/FVC (0.53 z-scores). ConclusionsGLI equations are appropriate for Spanish preschool children. These data provide further evidence to support widespread application of the GLI reference equations.

Malignant Pleural Effusions.

may have already occurred, thus providing a rich environment for growth of P. aeruginosa. Nevertheless, the lack of improvement in lung function measures, despite aggressive treatment and apparent eradiation of P. aeruginosa, is concerning. This finding emphasizes the importance of employing preventative therapy before the development of airway inflammation and infection. Driven by detailed work performed in laboratories such as that described in this issue of the Journal, infant lung function testing has now entered a new stage and can be considered a clinical outcome measure, similar to spirometry in the older child. The raised-volume technique has been standardized (12), published reference values are available (14), procedural risks are acceptable, and studies have clearly demonstrated that this technique is suitable to discriminate lung disease from health (3–5). Results from a recently completed trial performed in infants with CF in the United States are encouraging as they demonstrate the feasibility of studying infant lung function in a multicenter setting when strict quality assurance and training is implemented (15). The tremendous progress in this area of measuring infant physiology will naturally lead to intervention studies using these parameters as outcome measures. Over the next decade, we expect that techniques such as infant and preschool lung function testing will not only improve our understanding of the once ‘‘silent’’ and mysterious young CF lung but will also help us to develop stronger evidence for potential early intervention strategies in this vulnerable age group (16).

Evolution of cystic fibrosis lung function in the early years.

Most treatment of newborn screening-diagnosed cystic fibrosis is not evidence-based; there are very few randomized controlled trials (RCTs). Furthermore, the advent of novel molecular therapies, which could be started at diagnosis, mandates performing RCTs in very young children. However, unless the natural history of early cystic fibrosis lung disease is known, RCTs are impossible. Here, we review the results of two large prospective cohorts of these infants - London Cystic Fibrosis Collaboration (LCFC) (London, UK) and Australian Respiratory Early Surveillance Team for Cystic Fibrosis (AREST-CF) (Australia). Nutritional status remained excellent in both the cohorts. Both cohorts reported abnormal lung function aged at 3 months. AREST-CF, which previously reported rapidly declining preschool lung function, now report good conventional school-age spirometry. LCFC reported improvement between 3 months and 1 year, and stability in the second year. AREST-CF also reported a high prevalence of high resolution computed tomographic abnormalities related to free neutrophil elastase in bronchoalveolar lavage; LCFC reported high resolution computed tomographic changes at 1 year, which were too mild to be scored reproducibly. At least in the first 2 years of life, lung function is not a good end-point for RCTs; routine bronchoalveolar lavage and HRCT cannot be justified. Newborn screening has greatly improved outcomes, but we need better point-of-care biomarkers.

Pico de fluxo da tosse em pré-escolares: taxa de sucesso e reprodutibilidade teste-reteste

It is important to evaluate lung function in preschoolers. There are few studies related to pulmonary function tests with this part of the population. The purpose of this study was to evaluate the success rate and test-retest reproducibility of the cough peak flow (CPF) in a sample with children between four and six years old. The CPF was tested in 44 healthy children (26 boys, 18 girls), selected according to the ATS-DLD-78-C questionnaire, used to detect the presence of common respiratory diseases or induced by environmental exposure. An expiratory peak flow meter (Piko-I Electronic Peak Flow Meter, Pulmonary Data Services, USA) was used to measure CPF. The success rate was defined as the percentage of children able to perform the test according to the acceptability and reproducibility criteria. To evaluate the test-retest reproducibility, 10 children (according with the sample calculation) were reevaluated after three weeks. The study was approved by the Ethics Research Committee of the Institution. The test-retest reproducibility was evaluated by the paired t-test, considering a significance of p<0.05 and intraclass correlation coefficient (ICC). The results showed a success rate of 91% for CPF, with 80%, 88% and 100% for children with four, five and six years, respectively. Regarding the test-retest reproducibility, there was no significant difference between data of the first assessment and reassessment (p=0.39) and an ICC of 0.84 was observed. These results suggest an elevated success rate in the performance of CPF and an excellent test-retest reproducibility for this variable in healthy preschoolers.

VEGFA variants are associated with pre-school lung function, but not neonatal lung function

Vascular endothelial growth factor (VEGF) is implicated in airway remodelling and asthma development. We studied VEGFA gene variants and plasma levels and the development of lung function, bronchial hyperresponsiveness and asthma in childhood. We analysed 13 SNPs in the VEGFA gene in 411 children from the COPSAC2000 high-risk birth cohort. Asthma was diagnosed prospectively, and lung function measurements were obtained at birth and 6years of age. Plasma VEGF levels were measured at 18months of age. We used a Bonferroni adjusted significance level. Findings were replicated in the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort at age 8. At age six, three SNPs from the same linkage block were associated with FEV1 (rs699947, P=1.31E-05), independent of asthma, and there were suggestive associations between FEV1/FVC ratio and rs833052 and maximal mid-expiratory flow and rs6900017. Replication in the PIAMA cohort showed borderline association between FEV1 and rs699947 and significant meta-analysis result. SNPs upstream and nearby rs699947 were nominally associated with VEGF plasma levels. VEGF levels were not associated with asthmatic symptoms or lung function measures. VEGF gene variants are associated with lung function at school age, but not at birth, suggesting a role of VEGF in post-natal lung function development.

Novel end points for clinical trials in young children with cystic fibrosis

Cystic fibrosis (CF) lung disease commences early in the disease progression and is the most common cause of mortality. While new CF disease-modifying agents are currently undergoing clinical trial evaluation, the implementation of such trials in young children is limited by the lack of age-appropriate clinical trial end points. Advances in infant and preschool lung function testing, imaging of the chest and the development of biochemical biomarkers have led to increased possibility of quantifying mild lung disease in young children with CF and objectively monitoring disease progression over the course of an intervention. Despite this, further standardization and development of these techniques is required to provide robust objective measures for clinical trials in this age group.

Exhaled breath condensate purines correlate with lung function in infants and preschoolers

Exhaled breath condensate purines correlate with lung function in infants and preschoolers

Evaluation and use of childhood lung function tests in cystic fibrosis

Lung disease begins early in life in cystic fibrosis (CF), yet our understanding of CF lung abnormalities in the first years of life remains limited. By facilitating earlier diagnosis, newborn screening for CF provides the opportunity to understand and characterize presymptomatic lung disease in infants and young children. This could lead to earlier interventions to mitigate disease progression at a time when therapeutic intervention or prevention may be most effective. This article reviews lung function tests that can be used during the first 5 years of life and discusses their potential applications as objective outcomes for clinical monitoring or research. During the past decade, commercial equipment for assessing a wide range of lung function tests in infants and preschool children has become available together with international guidelines and improved reference equations with which to interpret results. The lung clearance index, derived from multiple breath washout, has been shown to be far more sensitive to early CF lung disease than conventional spirometric assessments. Although limited evidence exists as to whether incorporating lung function tests into routine clinical care can improve patient outcomes during the early years, this is likely to be helpful in preschool children if more sensitive tests such as the multiple breath washout become more widely available. There is an urgent need to assess which infant and preschool lung function outcomes will provide the most robust outcome measures in collaborative multicenter studies, so that they can be incorporated into early therapeutic intervention studies.

Advances in infant and preschool lung function testing

Background: Infant lung function tests are currently performed in more than 100 centres worldwide. Increasingly, centres in the AsiaPacific region are purchasing expensive and specialized equipment for this purpose. Equipment for testing preschool equipment is generally less expensive than equipment required for testing infants but assessing preschool children is tricky and requires investment in both time and human resources to get the right people for the job of working with such single-minded individuals. Pulmonary function testing in research: Infant and preschool lung function testing is being used in several research contexts. Recent studies that have used these tests have helped advance our knowledge on the early pathophysiology of diverse respiratory conditions such as cystic fibrosis, infant and preschool wheezing, childhood asthma, broncho-pulmonary dysplasia, as well as providing insights into aspects of lung growth and development. Pulmonary function testing in clinical practice: Infant and preschool lung function tests are also widely used (rightly or wrongly) for clinical evaluation. To be of benefit in clinical practice pulmonary function testing needs to be able to identify diminished lung function that may require a clinical response (this depends on good healthy control or reference data), to monitor disease status over time (depends on data on repeatability in both health and disease) and the response to therapeutic interventions (data on short-term repeatability required). Interpretation is currently limited in all these areas but general consensus is that the tests are on the cusp of being used routinely in clinical practice. Tests used in infants: The most popular tests in infants are those assessing forced expiratory flows and volumes (such as the raised volume and tidal rapid thoraco-abdominal compression techniques), plethysmography to measure functional residual capacity, and tests of ventilation inhomogeneity (such as the multiple breath inert gas washout). Limitations include the need for sedation, labour costs, lack of reference data and lack of longer-term repeatability data. Commercial equipment for each of these tests is, however, available. Tests used in preschool children: Popular tests in preschool children include those performed during tidal breathing such as the forced oscillation technique, resistance interrupter technique and multiple breath washout. Forced expiration using spirometry, with or without incentive, is also possible and widely used in preschool children. The technique of measuring the specific airways resistance is widely used in Europe and is in the process of undergoing standardization. Intervention studies and clinical trial networks: One outcome of lung function testing in infants and preschool children over the past few decades has been the insight gained into this crucial period of lung development where early insults to the developing lung architecture may have life-long effects in both chronic respiratory disorders and health. In the future, it is crucial that interventions are targeted early in life in order to prevent, rather than limit or reverse, the development of lung disease or maldevelopment of the lung. Infant and preschool lung function tests have been proposed as potential outcomes of such early intervention studies and have been used recently in this context. Multi-centre clinical trial networks are being developed for such studies that necessitate ongoing efforts to standardise the tests, develop quality assurance programs and facilitate better interchange of data between centres. Summary: Disappointingly, some of the limitations that have hindered interpretation of the results of infant (in particular), but also preschool, lung function tests over the past three decades are still to be overcome. However, advances in knowledge through research studies that have incorporated these tests, the commercial availability of several tests, the increasing number of centres gaining experience in their use and the recognition of the crucial role of early lung development in life-long lung health have served to highlight the importance of overcoming the limitations so that infant and preschool lung function tests can be used routinely in clinical practice.

Lung function from infancy to preschool in a cohort of children with cystic fibrosis

This study aimed to describe lung function in a cohort of children with cystic fibrosis (CF) who underwent infant pulmonary function tests (IPFTs) and preschool spirometry. Children performed up to four IPFTs (raised volume rapid thoracic compression technique) over 1 yr and five preschool spirometry tests over up to 2 yrs during participation in prospective, multicentre studies of infant and preschool lung function. All lung function data were reviewed centrally for measurement acceptability. 45 children had 252 acceptable measurements (137 IPFTs and 115 preschool spirometries) at ages 0.3-6.5 yrs. The median number of measurements per participant was 6 (range 3-9). Recent Pseudomonas aeruginosa infection was associated with 5.1% (95% CI 0.01-9.9%) lower forced expiratory volume in 0.5 s (FEV(0.5)) and 16.4% (95% CI 7.0-24.9%) lower forced expiratory flow at 25-25% of forced vital capacity (FEF(25-75%)), after adjustment for length, test type and centre. Recent cough was associated with 5.7% (95% CI 1.1-10.1%) lower FEV(0.5) and 10.1% (95% CI 0.6-18.7%) lower FEF(25-75%). Even after accounting for infection status, cough, sex, length, test type and centre, there was significant inter-individual variability in lung function (p<0.01 for each of FEV(0.5), FEF(25-75%) and forced vital capacity). Recent P. aeruginosa infection and cough are associated with lower lung function in children with CF. Significant inter-individual variability in lung function remains to be explained.

Exhaled breath condensate purines correlate with lung function in infants and preschoolers

Although airway inflammation begins early in life in children with chronic respiratory diseases, current methods to assess this inflammation are invasive and entail significant risk. Measurement of exhaled breath condensate (EBC) purines and other biomarkers offers a less invasive method to assess airway inflammation; however, the feasibility and utility of EBC biomarkers in young children has not been established. EBC was collected from children <3 years old with cystic fibrosis or other lung diseases during clinically indicated infant pulmonary function tests (iPFTs). EBC concentrations of the purine biomarkers adenosine (Ado), adenosine monophosphate (AMP), and the dilution marker urea were measured using mass spectrometry. EBC was successfully collected (average volume 330 ± 170 µl) from preschool children (age 2.3 ± 0.8 years) in 15 of 17 iPFTs. No significant changes in oxygen saturation (96.9 ± 1.6 start, 96.8 ± 1.7 end, P = 0.389) or respiratory rate (35.2 ± 7.5 start, 34.6 ± 7.9 end, P = 0.443) were observed during collection. Ado and AMP were successfully measured in 13/15 samples [8 cystic fibrosis (CF)]. EBC AMP to Ado ratio (AMP/Ado) negatively correlated with forced expiratory volume at 0.5 sec (FEV(0.5) , r = -0.71, P < 0.01) and positively with the ratio of residual volume to total lung capacity (RV/TLC, r = 0.66, P = 0.015). These correlations remained statistically significant in the subset with CF. EBC can be safely collected and analyzed in preschool children using commercially available equipment. The EBC AMP/Ado ratio correlates with measures of infant lung function and may be a less invasive means of monitoring airway inflammation in this population.

Monitoring of Structure and Function in Early Cystic Fibrosis Lung Disease.

Concurrent with improving survival in cystic fibrosis (CF), lung function has also steadily improved. Forced expiratory volume in one second (FEV1), the measure of airway obstruction most widely monitored in patients with CF, often does not fall below the normal range until late adolescence. Clearly, FEV1 is losing relevance for clinicians monitoring lung disease in children with CF, as it is frequently normal, declines slowly, and cannot be measured by conventional techniques in children <6 years of age. As clinicians increasingly aim to identify and treat early CF lung disease before irreversible structural airway damage occurs, there is a compelling need for better tools with which to monitor for early lung structural and physiologic abnormalities in our youngest CF patients. Three promising measures are infant and preschool lung function testing, chest computed tomography, and multiple breath washout measures of the lung clearance index. The current state of these tests as they relate to the clinical monitoring of early CF lung disease is reviewed, and improvements on the horizon that may allow them to be adopted in clinical practice explained.

Residential proximity to main roads and lung function in healthy young children: Table 1–

To the Editors: In preschool children, exposure to traffic-related emissions is associated with increased prevalence of respiratory symptoms [1–3] and, in school-aged children, with reduced lung function growth [4]. However, to date, the association between air pollution and preschool lung function remains unclear. In a cross-sectional study, we investigated the effects of residential proximity to main roads and air pollutants on lung function in healthy preschool children. Spirometric forced vital capacity, forced expiratory volume in 1 s and 0.5 s, lung clearance index (LCI) by multiple breath washout, plethysmographic specific airway resistance (s R aw) and exhaled nitric oxide fraction ( F eNO) were measured in healthy preschool children as part of another study protocol [5 …