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

Non-invasive forced oscillometry to quantify respiratory mechanics in term neonates

BACKGROUND

To determine normative data by forced oscillation technique (FOT) in non-sedated normal term neonates and test the hypothesis that infants with transient tachypnea of the newborn (TTN) have higher resistance (R) and lower reactance (X) on day 1.

METHODS

Healthy term infants (n = 138) and infants with TTN (n = 17) were evaluated on postnatal days 1 through 3 (NCT03346343). FOT was measured with a mask using a TremoFlo C-100 Airwave System™. R, X, and area under the reactance curve (AX) were measured at prime frequencies 7-41 Hz for 8 s.

RESULTS

In all, 86% of control infants had adequate measurements (coherence >0.8, CV < 0.25) on day 1. Infants with TTN had higher resistance at 13 Hz (TTN 32.5 cm H₂O·s/L [95% CI 25.5-39.4]; controls 23.8 cm H₂O·s/L [95% CI 22.2 to 25.3], P = 0.007) and lower reactance from 17 to 37 Hz (TTN -35.1 to -10.5; controls -26.3 to -6.1, P < 0.05). In healthy controls, lung mechanics were unchanged from days 1 to 3. In TTN, lung mechanics normalized on days 2 and 3.

CONCLUSIONS

FOT is feasible in neonates and distinguishes normal control infants from those with TTN on postnatal day 1. Oscillometry offers a non-invasive, longitudinal technique to assess lung mechanics in newborns.

Pulmonary function testing in children's interstitial lung disease

The use of pulmonary function tests (PFTs) has been widely described in airway diseases like asthma and cystic fibrosis, but for children's interstitial lung disease (chILD), which encompasses a broad spectrum of pathologies, the usefulness of PFTs is still undetermined, despite widespread use in adult interstitial lung disease. A literature review was initiated by the COST/Enter chILD working group aiming to describe published studies, to identify gaps in knowledge and to propose future research goals in regard to spirometry, whole-body plethysmography, infant and pre-school PFTs, measurement of diffusing capacity, multiple breath washout and cardiopulmonary exercise tests in chILD. The search revealed a limited number of papers published in the past three decades, of which the majority were descriptive and did not report pulmonary function as the main outcome.PFTs may be useful in different stages of management of children with suspected or confirmed chILD, but the chILD spectrum is diverse and includes a heterogeneous patient group in all ages. Research studies in well-defined patient cohorts are needed to establish which PFT and outcomes are most relevant for diagnosis, evaluation of disease severity and course, and monitoring individual conditions both for improvement in clinical care and as end-points in future randomised controlled trials.

Bronchial challenge test in patients with a history suggestive of bronchial asthma with normal spirometric studies

Background

Bronchial hyper-responsiveness (BHR) is the hallmark of bronchial asthma, characterized by clinical features of cough, wheeze, breathlessness and chest tightness which are confirmed by spirometry showing obstructive pattern and reversibility to bronchodilators. In individuals having features of bronchial asthma but normal spirometry, demonstration of BHR with bronchial challenge test (direct or indirect) confirms/ rules out the diagnosis. The aim of this study was to assess BHR in patients (methacholine challenge) with a history suggestive of bronchial asthma but normal spirometry and its role in diagnosis of bronchial asthma.

Methods

This study was conducted at tertiary care respiratory center. Patients having clinical features of bronchial asthma but spirometry not confirming obstructive disorder and or reversibility were included in the study. After written consent, methacholine challenge test with methacholine chloride and exercise spirometry was done in all patients as per the American Thoracic Society protocol.

Results

A total of 50 (n) patients were included in the study. Among them, 42 patients had clinical features suggestive of bronchial asthma but having normal spirometry and eight patients were diagnosed as they had bronchial asthma in the past but asymptomatic and off drugs were included in the study. At PC20 4mg/ml 32 (64%) patients had a positive test, 28(66%) symptomatic patients and four (50%) asymptomatic asthmatics. There were no significant side effects with methacholine test.

Conclusion

Airway hyper-responsiveness is an important aspect of bronchial asthma and its demonstration with bronchial challenge (direct and indirect) test is an important diagnostic tool. Methacholine challenge test is a safe procedure to perform under supervision.

Fluctuation-based clustering reveals phenotypes of patients with different asthma severity

Serial peak expiratory flow (PEF) measurements can identify phenotypes in severe adult asthma, enabling more targeted treatment. The feasibility of this approach in children has not been investigated.

Overall, 105 children (67% male, median age 12.4 years) with a range of asthma severities were recruited and followed up over a median of 92 days. PEF was measured twice daily. Fluctuation-based clustering (FBC) was used to identify clusters based on PEF fluctuations. The patients’ clinical characteristics were compared between clusters.

Three PEF clusters were identified in 44 children with sufficient measurements. Cluster 1 (27% of patients: n=12) had impaired spirometry (mean forced expiratory volume in 1 s (FEV₁) 71% predicted), significantly higher exhaled nitric oxide (≥35 ppb) and uncontrolled asthma (asthma control test (ACT) score <20 of 25).

Cluster 2 (45%: n=20) had normal spirometry, the highest proportion of difficult asthma and significantly more patients on a high dose of inhaled corticosteroids (≥800 µg budesonide).

Cluster 3 (27%: n=12) had mean FEV₁ 92% predicted, the highest proportion of patients with no bronchodilator reversibility, a low ICS dose (≤400 µg budesonide), and controlled asthma (ACT scores ≥20 of 25).

Three clinically relevant paediatric asthma clusters were identified using FBC analysis on PEF measurements, which could improve telemonitoring diagnostics. The method remains robust even when 80% of measurements were removed. Further research will determine clinical applicability.

Fluctuation-based clustering is a robust method that identifies clinically relevant subgroups of patients with asthma to refine referral strategies to a tertiary centrehttps://bit.ly/35g1ldb

Residential greenspace and lung function up to 24 years of age: The ALSPAC birth cohort

BACKGROUND

Residing in greener areas is increasingly linked to beneficial health outcomes, but little is known about its effect on respiratory health.

OBJECTIVE

We examined associations between residential greenness and nearby green spaces with lung function up to 24 years in the UK Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort.

METHODS

Lung function was measured by spirometry at eight, 15 and 24 years of age. Greenness levels within circular buffers (100-1000 m) around the birth, eight-, 15- and 24-year home addresses were calculated using the satellite-derived Normalized Difference Vegetation Index and averaged (lifetime greenness). The presence and proportion of green spaces (urban green spaces, forests and agricultural land) within a 300 m buffer was determined. First, associations between repeated greenness and green space variables and repeated lung function parameters were assessed using generalized estimation equations (N = 7094, 47.9% male). Second, associations between lifetime average greenness and lifetime average proportion of green spaces with lung function at 24-years were assessed using linear regression models (N = 1763, 39.6% male). All models were adjusted for individual and environmental covariates.

RESULTS

Using repeated greenspace and lung function data at eight, 15 and 24 years, greenness in a 100 m buffer was associated with higher FEV₁ and FVC (11.4 ml [2.6, 20.3] and 12.2 ml [1.8, 22.7], respectively, per interquartile range increase), as was the presence of urban green spaces in a 300 m buffer (20.3 ml [-0.1, 40.7] and 23.1 ml [-0.3, 46.5] for FEV₁ and FVC, respectively). These associations were independent of air pollution, urbanicity and socio-economic status. Lifetime average greenness within a 100 m buffer and proportion of agricultural land within a 300 m buffer were associated with better lung function at 24 years but adjusting for asthma attenuated these associations.

DISCUSSION

This study provides suggestive evidence that children whose homes are in more vegetated places or are in close proximity of green spaces have better lung function up to 24 years of age.

Respiratory health profile of Indigenous Australian children and young adults

AIM

National data report respiratory illness to be the most common chronic illness in Australian Indigenous people aged <35 years but multi-centre data on specific diseases is sparse. Respiratory health is now known to be an independent predictor of future all-cause mortality and cardiovascular disease. We aimed to describe the respiratory health profile (clinical and spirometry data) of randomly recruited Indigenous Australian children and young adults from several sites.

METHODS

As part of the Indigenous Respiratory Reference Values study, 1278 Australian Indigenous children and young adults (aged 3-25 years) were recruited from nine communities (Queensland, n = 8; Northern Territory, n = 1). Self-reported and medical records were used to ascertain respiratory history. Participants were classified as 'healthy' if there was no current/previous respiratory disease history. Spirometry was performed on all participants and assessed according to forced expiratory volume at 1 s impairment.

RESULTS

Medical history data were available for 1245 (97.4%) and spirometry for 1106 participants (86.5%). Asthma and bronchitis were the most commonly reported respiratory conditions (city/regional 19.5% and rural/remote 16.8%, respectively). Participants with a history of any respiratory disease or those living in rural/remote communities had lower lung function compared to the 'healthy' group. Almost 52.0% of the entire cohort had mild-moderate forced expiratory volume at 1 s impairment (47.7% in 'healthy' group, 58.5% in 'respiratory history' group).

CONCLUSION

The high prevalence of poor respiratory health among Indigenous Australian children/young adults places them at increased risk of future all-cause mortality and cardiovascular disease. Respiratory assessments including spirometry should be part of the routine evaluation of Indigenous Australians.

Predicting the outcome of respiratory disease in wheezing infants using tidal flow-volume loop shape

INTRODUCTION AND OBJECTIVES

Wheezing (RW) infants with a positive asthma predictive index (API+) have a lower lung function as measured by forced expiratory techniques. Tidal flow-volume loops (TFVL) are easy to perform in infants, and sedation is not necessary.

MATERIALS AND METHODS

A total of 216 wheezing infants were successfully measured, and 183 of them were followed for over a year. TFVL loops were classified into one of three categories depending of their geometric shape (symmetric, convex, and concave). Respiratory rate (Rr), presence of API+, and the number of exacerbations during the following year were also recorded.

RESULTS

Children with concave loops had more exacerbations in the following year (OR = 6.8 [IC95% 3.33;13.91]). Infants API + were also significantly more related to concave loops (OR = 10.02 [IC 95% 4.53; 22.15]). Rr was higher in infants with concave loops (44+/-15.5 vs. 36.6 +/-12.6; p < 0.01).

CONCLUSION

Infants with a concave TFVL have a higher probability of experiencing exacerbations in the following year, and are at a higher risk of suffering asthma.

Predicting asthma exacerbation by impulse oscillometry evaluation of small airway function and fractional exhaled nitric oxide in preschool children

OBJECTIVE

To study impulse oscillometry (IOS) indices of peripheral airway function and FeNO as predictors of future loss of asthma control in preschool children.

METHODS

Patients aged 3 to 6 years who were actively being treated for asthma and children without asthma were enrolled in the study. Participants had no change in medication on visit 1 and returned for a follow-up visit within 8 to 12 weeks. At the first visit, nursing assessment, symptom history, IOS analysis, FeNO, and physician evaluation were repeated.

RESULTS

Fifty-one (64.6%) subjects had lost asthma control (UC-Group) and 28 (35.4%) subjects had maintained asthma control (C-Group) at their follow-up visit. Thirty-two children without asthma were enrolled in the study as a normal control group (N-Group). R5, R5-20, AX, and Z5 values were all significantly higher in subjects whose symptoms remained uncontrolled compared with those in the controlled asthma group (P < .01) and also significantly higher than those in the normal control group (P < .01). FeNO showed no significant difference between the UC-Group and C-Group (P = .399). Four indices-R5, R5-20, AX, and Z5-had an estimated area under the curve (AUC) of greater than 0.8 and were thus easily able to distinguish the UC-Group from the C-Group.

CONCLUSIONS

AX had the highest overall AUC (0.884) of the investigated parameters, and the optimal cut-off point of 37.435 cm H₂ O/L was able to predict future loss of asthma control in preschool children.

Impact of a supervised training course on spirometry competency for primary care pediatricians

Objective: Spirometry is the most commonly performed lung function test, and performance, adherence to acceptability and repeatability criteria, and accurate interpretation of results help optimize the test's usefulness. This study aimed to measure the effects of spirometry training courses supported by the Italian Pediatric Respiratory Society (IPRS) on primary care pediatricians' (PCP) knowledge of spirometry test quality, ability to interpret results, and overall degree of satisfaction with the course.Methods: Of the six face-to-face courses, four lasted two days and two lasted one day: mean duration of theoretical lessons was five and four hours respectively; and practical sessions lasted eight and six hours, respectively. At the end of each course, participants took a learning test consisting of evaluating six flow-volume curves. Degree of satisfaction was assessed by asking participants to rank the relevance, quality, and usefulness of the course.Results: 261 PCPs were involved, with most (67.43%) taking two-day courses. Nearly all participants correctly identified normal and restrictive patterns. Intrathoracic large-airway obstruction was the pattern most difficult to identify correctly (70.5% overall), whereas > 80% of the participants correctly classified artifacts, obstructive-restrictive, and obstructive patterns. Participants in longer courses reported significantly higher values on the learning score. The overall degree of satisfaction average ranged between "good" and "excellent".Conclusions: This pilot study showed the greater impact of two-day courses than one-day courses for training PCPs to properly interpret spirometry, confirming that a practical module lasting at least six hours is sufficient to deliver adequate training on spirometry for healthcare professionals.

Children with uncontrolled asthma and significant reversibility might show hypoxaemia

Asthmatic children free of exacerbation with airway obstruction may have low partial pressure of oxygen (PaO₂) which can be a marker for future risk, but PaO₂ is scarcely measured during pulmonary function testing. We prospectively included asthmatic children with airway obstruction referred for pulmonary function testing, including blood gas analysis (n = 51). Hypoxaemia, defined as a value lower than - 2 z-score, was present in 15 (29%) children, and 37 (72%) children had a significant reversibility after bronchodilator administration. The multivariable model showed a positive influence of baseline forced expiratory volume in 1 s (FEV₁) on PaO₂ (β coefficient 0.69, [95% CI: 0.07; 1.30]; P = 0.03), whereas uncontrolled asthma and FEV₁ reversibility negatively influenced it (β coefficient - 1.59 [95% CI: - 2.74; - 0.44]; P = 0.01; and - 0.07 [95% CI: - 0.13; - 0.02]; P = 0.01, respectively). As a consequence, children with uncontrolled symptoms of asthma and FEV₁ reversibility ≥ 12% were significantly more at risk of having hypoxaemia compared to children with well/partly controlled asthma or no significant reversibility of FEV₁.Conclusion: Among obstructive asthmatic children without current exacerbation, hypoxaemia is more likely to be seen in children with uncontrolled asthma and a significant post-bronchodilator FEV₁ reversibility, in favour of different pathophysiology and treatment requirements of their airway obstruction.What is Known:• Recommendations are to treat asthmatic children in order to control respiratory symptom and maintain normal pulmonary function.• Asthmatic children free of exacerbation may have different pathophysiology for airway obstruction (central, peripheral, inflammatory, spasticity, remodelling) and should be treated according the pathophysiology of their airway disease.What is New:• In obstructive asthmatic children free of current exacerbation, the presence of hypoxaemia (ventilation-perfusion mismatch) is influenced by asthma control and post-bronchodilator reversibility, independently of the level of baseline airway obstruction.• The presence of hypoxaemia in obstructive asthmatic children free of current exacerbation can be highly suspected by the composite index "uncontrolled asthma + FEV₁reversibility ≥ 12%" which may guide treatment.

Effect of breastfeeding duration on lung function, respiratory symptoms and allergic diseases in school-age children

BACKGROUND

A positive effect of breastfeeding on lung function has been demonstrated in cohorts of children with asthma or risk for asthma. We assessed the impact of breastfeeding on lung function and symptoms at the age of 6 years in an unselected, healthy birth cohort.

METHODS

We prospectively studied healthy term infants from the Bern-Basel Infant Lung Development (BILD) cohort from birth up to 6 years. Any breastfeeding was assessed by weekly phone calls during the first year of life. Risk factors (eg, smoking exposure, parental history of allergic conditions, and education) were obtained using standardized questionnaires. The primary outcomes were lung function parameters measured at 6 years of age by spirometry forced expiratory volume in 1 second, body plethysmography (functional residual capacity [FRCpleth ], the total lung capacity [TLCpleth ], and the effective respiratory airway resistance [Reff ]) and fractional exhaled nitric oxide (FeNO). Secondary outcomes included ever wheeze (between birth and 6 years), wheeze in the past 12 months, asthma, presence of allergic conditions, atopic dermatitis, rhinitis, and positive skin prick test at the age of 6 years.

RESULTS

In 377 children the mean breastfeeding duration was 36 weeks (SD 14.4). We found no association of breastfeeding duration with obstructive or restrictive lung function and FeNO. After adjustment for confounders, we found no associations of breastfeeding duration with respiratory symptoms or the presence of allergic conditions.

CONCLUSION

This study found no evidence of an association between breastfeeding and comprehensive lung function in unselected healthy children with long-term breastfeeding. Our findings do not support the hypothesis that the duration of breastfeeding has a direct impact on lung function in a healthy population with low asthmatic risk.

Multiple Breath Washout for Diagnosing Asthma and Persistent Wheeze in Young Children

Rationale: There is an unmet need for sensitive lung function tests for young children to aid in the diagnosis of asthma and wheezy disorders. We hypothesized that multiple breath washout (MBW) could be a valuable tool for such a purpose. Objectives: To compare the ability of MBW lung clearance index with traditional lung function measurements to discriminate between preschool children with well-controlled asthma/persistent wheeze and healthy children. Methods: We investigated 646 children from the COPSAC₂₀₁₀ (Copenhagen Prospective Studies on Asthma in Childhood 2010) mother-child cohort, who completed MBW testing with nitrogen, spirometry, and plethysmography before age 6 years. Asthma/persistent wheeze was prospectively diagnosed according to a validated symptom-based algorithm at the COPSAC clinic. Student's t tests and receiver operating characteristic curves were applied to analyze the discriminative ability of the lung function indices. Results: A total of 144 (22.3%) children were diagnosed with asthma/persistent wheeze during their first 6 years of life. Lung clearance index from MBW was not significantly different in children with versus those without asthma/persistent wheeze (mean standard deviation [SD] = 6.96 [1.14] vs. 6.95 [0.93], mean difference [95% confidence interval] = 0.02 [-0.18 to 0.22], P = 0.86, area under the curve [AUC] = 0.48), whereas significant differences were observed for specific airway resistance from plethysmography (1.21 kPa/s [0.31] vs. 1.14 kPa/s [0.25]; +0.07 kPa/s [0.02-0.13]; P < 0.01; AUC = 0.56) and spirometry forced expiratory volume in 1 second (FEV₁) % predicted (99.4% [12.0] vs. 102.6% [12.5]; -3.2% [-5.6 to -0.9]; P < 0.01; AUC = 0.56) and forced expiratory flow at 25-75% (1.55 L/s [0.44] vs. 1.68 L/s [0.46]; -0.14 L/s [-0.22 to -0.05]; P < 0.01; AUC = 0.58). FEV₁ (L/s) and FEV₁/forced vital capacity ratio were not significantly different (P > 0.4). Conclusions: MBW, spirometry, and plethysmography are not sensitive tools for diagnosing mild asthmatic disease in young children.

Early inhaled budesonide in extremely preterm infants decreases long-term respiratory morbidity

BACKGROUND

There is no strict correlation between early bronchopulmonary dysplasia and long-term respiratory disease. Early inhaled corticosteroids seem to reduce the incidence of bronchopulmonary dysplasia, but the long-term outcome remains unknown.

RESEARCH QUESTION

The aim of this study was to evaluate the effect of early inhaled corticosteroids on chronic respiratory morbidity.

METHODS

Fifty-nine survivors from the Prague cohort included in Neonatal European Study of Inhaled Steroids underwent further follow-up comprising of respiratory morbidity monitoring during the first 2 years of life followed by objective lung function testing performed at the age of 5.9 years (range 5-7 years). Both outcomes were pursued and finalized before the unblinding of budesonide subgroups.

RESULTS

Fifty randomized (budesonide vs placebo group, 56% vs 44%) survivors were included in the study. Spirometry was successfully performed in 48 children. No statistically significant differences were found in the lung function test (forced expiratory flow [FEF] - FEF₇₅ , FEF_50, FEF₂₅ , and FEF_25-75; FEV₁ , forced vital capacity [FVC], FEV₁ /FVC) although mild trend to the improvement of expiratory flow pattern was observed in the budesonide group (median z-score of FEV₁ /FVC -0.376 vs -0.983, P = .13; median z-score of FEF_25-75 -1.004 vs -1.458, P = .13; median z-score of FEF₇₅ -0.527 vs -0.996, P = .17). Children assigned to budesonide had a significantly lower rate of symptoms of chronic lung disease (34.6% vs 68.2%; P = .04) than children assigned to placebo.

INTERPRETATION

Our study suggests that early inhaled budesonide was associated with the trend to the improvement of functional lung parameters and with a lower rate of symptoms of chronic lung disease within the first 2 years of life.

Rectal Organoids Enable Personalized Treatment of Cystic Fibrosis

In vitro drug tests using patient-derived stem cell cultures offer opportunities to individually select efficacious treatments. Here, we provide a study that demonstrates that in vitro drug responses in rectal organoids from individual patients with cystic fibrosis (CF) correlate with changes in two in vivo therapeutic endpoints. We measured individual in vitro efficaciousness using a functional assay in rectum-derived organoids based on forskolin-induced swelling and studied the correlation with in vivo effects. The in vitro organoid responses correlated with both change in pulmonary response and change in sweat chloride concentration. Receiver operating characteristic curves indicated good-to-excellent accuracy of the organoid-based test for defining clinical responses. This study indicates that an in vitro assay using stem cell cultures can prospectively select efficacious treatments for patients and suggests that biobanked stem cell resources can be used to tailor individual treatments in a cost-effective and patient-friendly manner.

Diffusing Capacity of the Lung for Carbon Monoxide in Mexican/Latino Children. Quality Control and Reference Values

RATIONALE

Single-breath diffusing capacity of the lung for carbon monoxide (Dl_COsb) values are used to evaluate gas exchange; however, the quality of maneuvers performed by children has not been evaluated, and reference values for young people living at moderate altitudes are not well established.

OBJECTIVES

Our objectives were 1) to determine whether Dl_COsb maneuvers performed by a pediatric population would meet 2017 European Respiratory Society/American Thoracic Society (ERS/ATS) quality control standards; and 2) to report normal Dl_COsb values for Mexican/Latino children and adolescents living at moderate altitudes.

METHODS

This study involved healthy young people 4-20 years of age from the metropolitan area of Mexico City (2,240 m above sea level) who were recruited in schools from July 2014 to August 2017. Dl_COsb testing was performed according to the 2005 ATS/ERS standards, and the quality control of each maneuver was analyzed according to the 2017 ERS/ATS standards. We constructed models for Dl_COsb with linear and quadratic terms for weight, height, and age as independent variables using shrinkage statistics, variance inflation factors, the Akaike information criterion, and R² to compare the results of different models.

RESULTS

Results were obtained for 420 individuals (53% boys) with a mean age of 11.7 ± 4.5 standard deviation (SD) years; 47% of maneuvers from children age 4-6 years were grade A (13% grade B), and 90% of those in children older than 13 years were grade A or B. Forty-six percent of the subjects had a Dl_COsb repeatability of <1 ml/min/mm Hg. The mean Dl_COsb was higher for boys than for girls (32.4 ± 13.6 [SD] vs. 24.1 ± 7.5 ml/min/mm Hg, respectively). The reference equation for boys was Dl_COsb = exp(1.63469 + [0.03251 × age] + [0.00846 × height] + [0.00304 × weight]), R² = 0.87; for girls, the best equation was Dl_COsb = exp(1.56516 + [0.0193 × age] + [0.00893 × height] + [0.00273 × weight]), R² = 0.75. The single-breath transfer coefficient of the lung for carbon monoxide remained constant with age and height, with a lower limit of normal of 6.5 ml/min/mm Hg/L in boys and 5.4 ml/min/mm Hg/L in girls. Measured Dl_COsb was higher than predicted by other authors (P < 0.001 by paired t test).

CONCLUSIONS

Individuals 4-20 years of age can complete high-quality Dl_COsb tests. Children and adolescents living at 2,240 m have higher Dl_COsb values than those living at sea level. Reference equations for Dl_COsb obtained at sea level are poor predictors of the values measured at moderate altitude.

How applicable are GLI 2012 equations to a sample of Middle Eastern school-age children?

BACKGROUND

The Global Lung Function Initiative attempted to formulate global all-age lung function equations. The suitability of these equations to Middle Eastern children was never evaluated; this study will evaluate these equations in addition to other regional ones.

METHODS

Spirometry was conducted for 582 (311 boys) healthy 6- to 13-year-old Jordanian children. z scores, predicted values, percent predicted values, and frequency of records below lower limit than normal (LLN) were calculated for each child using the studied equations.

RESULTS

Although none of the studied equations produced a perfect representation of the study data, the GLI 2012 equations for Caucasians were the most suitable.

CONCLUSION

GLI 2012 equations for Caucasians are a reasonable fit for Jordanian school-aged children.

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.

Standardization of Spirometry 2019 Update. An Official American Thoracic Society and European Respiratory Society Technical Statement

Background: Spirometry is the most common pulmonary function test. It is widely used in the assessment of lung function to provide objective information used in the diagnosis of lung diseases and monitoring lung health. In 2005, the American Thoracic Society and the European Respiratory Society jointly adopted technical standards for conducting spirometry. Improvements in instrumentation and computational capabilities, together with new research studies and enhanced quality assurance approaches, have led to the need to update the 2005 technical standards for spirometry to take full advantage of current technical capabilities.Methods: This spirometry technical standards document was developed by an international joint task force, appointed by the American Thoracic Society and the European Respiratory Society, with expertise in conducting and analyzing pulmonary function tests, laboratory quality assurance, and developing international standards. A comprehensive review of published evidence was performed. A patient survey was developed to capture patients' experiences.Results: Revisions to the 2005 technical standards for spirometry were made, including the addition of factors that were not previously considered. Evidence to support the revisions was cited when applicable. The experience and expertise of task force members were used to develop recommended best practices.Conclusions: Standards and consensus recommendations are presented for manufacturers, clinicians, operators, and researchers with the aims of increasing the accuracy, precision, and quality of spirometric measurements and improving the patient experience. A comprehensive guide to aid in the implementation of these standards was developed as an online supplement.

Obesity may enhance the adverse effects of NO2 exposure in urban schools on asthma symptoms in children

BACKGROUND

Sparse data address the effects of nitrogen dioxide (NO₂) exposure in inner-city schools on obese students with asthma.

OBJECTIVE

We sought to evaluate relationships between classroom NO₂ exposure and asthma symptoms and morbidity by body mass index (BMI) category.

METHODS

The School Inner-City Asthma Study enrolled students aged 4 to 13 years with asthma from 37 inner-city schools. Students had baseline determination of BMI percentile. Asthma symptoms, morbidity, pulmonary inflammation, and lung function were monitored throughout the subsequent academic year. Classroom NO₂ data, linked to enrolled students, were collected twice per year. We determined the relationship between classroom NO₂ levels and asthma outcomes by BMI stratification.

RESULTS

A total of 271 predominantly black (35%) or Hispanic students (35%) were included in analyses. Fifty percent were normal weight (5-84th BMI percentile), 15% overweight (≥85-94th BMI percentile), and 35% obese (≥95th BMI percentile). For each 10-parts per billion increase in NO₂, obese students had a significant increase in the odds of having an asthma symptom day (odds ratio [OR], 1.86; 95% CI, 1.15-3.02) and in days caregiver changed plans (OR, 4.24; 95% CI, 2.33-7.70), which was significantly different than normal weight students who exhibited no relationship between NO₂ exposure and symptom days (OR, 0.90; 95% CI, 0.57-1.42; pairwise interaction P = .03) and change in caregiver plans (OR, 1.37; 95% CI, 0.67-2.82; pairwise interaction P = .02). Relationships between NO₂ levels and lung function and fractional exhaled nitric oxide did not differ by BMI category. If we applied a conservative Holm-Bonferroni correction for 16 comparisons (obese vs normal weight and overweight vs normal weight for 8 outcomes), these findings would not meet statistical significance (all P > .003).

CONCLUSIONS

Obese BMI status appears to increase susceptibility to classroom NO₂ exposure effects on asthma symptoms in inner-city children. Environmental interventions targeting indoor school NO₂ levels may improve asthma health for obese children. Although our findings would not remain statistically significant after adjustment for multiple comparisons, the large effect sizes warrant future study of the interaction of obesity and pollution in pediatric asthma.

THERAPEUTIC BLOWING TOYS: DOES THE OVERLAP OF VENTILATORY STIMULI ALTER THE RESPIRATORY MECHANICS OF HEALTHY SCHOOLCHILDREN?

Objective:

To verify whether the overlapping of ventilatory stimuli, resulting from playing with blowing toys, changes the respiratory mechanics of healthy schoolchildren.

Methods:

Cross-sectional study with healthy schoolchildren aged seven to 14 years old from Florianópolis, Santa Catarina, Southern Brazil. Spirometric data were obtained, a health questionnaire and the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire were also applied. The procedure consisted of playing with the following blow toys in a random order: soap bubbles, party whistles and balloon. Before and after the intervention, the assessment of respiratory mechanics was carried out by impulse oscillometry - IOS (Erich Jaeger, Germany^®). The ANOVA for repeated measures test was applied.

Results:

71 students of both genders with mean age of 9.7±2.1 years participated in the study. Results showed a progressive decrease of impedance (Z5), total airway resistance (R5) and resonance frequency (Fres) when the moment before the use of the first toy was compared with the moment after the third toy (Z5/p=0.048; R5/p=0.049; Fres/p=0.004). Fres also differed between the moment before the first and the second toy (p=0.048). After the use of each of the three blowing toys, the oscillometric parameters did not differ.

Conclusions:

The difference in oscillometric parameters of R5 before the use of each toy indicates that the overlap of ventilatory stimuli produced by them provided a reduction in the R5.

Changes in the parent cystic fibrosis questionnaire-revised (CFQ-R) with respiratory symptoms in preschool children with cystic fibrosis

INTRODUCTION

The Cystic Fibrosis Questionnaire-Revised (CFQ-R) Respiratory score is a validated and widely used patient-reported outcome. This study aimed to establish changes in the score with acute respiratory events in preschool children with CF and to investigate its' relationship with physiological outcomes.

METHODS

The Parent CFQ-R, multiple breath washout test and spirometry were performed at six study visits over one year. The clinical status of participants, stable or symptomatic, was defined by the patient's physician. Linear regression and distribution-based statistical methods were used to examine the changes in the CFQ-R from the last stable visit and to investigate its relationship with physiological outcomes.

RESULTS

There were 272 stable and 115 symptomatic visits from 78 participants. The mean CFQ-R Respiratory score did not change between consecutive stable visits (-0.73, SD 20.4). The mean (SD) score deteriorated by 15.5 (20.7) points between stable and symptomatic visits and improved by 14.8 (20.1) points between symptomatic and stable follow-up visits. When a clinically important change is defined as 0.5SD change (10-points), the positive predictive value (PPV) was 45% and the negative predictive value (NPV) was 84%. For visits with a 10-point worsening in the CFQ-R Respiratory score and a 15% increase in LCI, the PPV was better (81%) than using either measure alone.

CONCLUSION

The CFQ-R Respiratory score is responsive to acute respiratory events in preschool children with CF and its utility to monitor individual patients is improved when combined with LCI.

Technical standards for respiratory oscillometry

Oscillometry (also known as the forced oscillation technique) measures the mechanical properties of the respiratory system (upper and intrathoracic airways, lung tissue and chest wall) during quiet tidal breathing, by the application of an oscillating pressure signal (input or forcing signal), most commonly at the mouth. With increased clinical and research use, it is critical that all technical details of the hardware design, signal processing and analyses, and testing protocols are transparent and clearly reported to allow standardisation, comparison and replication of clinical and research studies. Because of this need, an update of the 2003 European Respiratory Society (ERS) technical standards document was produced by an ERS task force of experts who are active in clinical oscillometry research.The aim of the task force was to provide technical recommendations regarding oscillometry measurement including hardware, software, testing protocols and quality control.The main changes in this update, compared with the 2003 ERS task force document are 1) new quality control procedures which reflect use of "within-breath" analysis, and methods of handling artefacts; 2) recommendation to disclose signal processing, quality control, artefact handling and breathing protocols (e.g. number and duration of acquisitions) in reports and publications to allow comparability and replication between devices and laboratories; 3) a summary review of new data to support threshold values for bronchodilator and bronchial challenge tests; and 4) updated list of predicted impedance values in adults and children.

The 95% effective dose of intranasal dexmedetomidine sedation for pulmonary function testing in children aged 1-3 years: A biased coin design up-and-down sequential method

STUDY OBJECTIVE

Intranasal dexmedetomidine (DEX) can provide adequate sedation during short examinations in children. However, we found no data regarding the 95% effective dose (ED₉₅) of intranasal DEX for children's pulmonary function testing (PFT).

DESIGN

Prospective study and a biased coin design up-and-down sequential method.

SETTING

Sedation center of Children's Hospital of Chongqing Medical University.

PATIENTS

Children aged 1-3 years undergoing pulmonary function testing.

INTERVENTION

The dose of DEX for each subsequent patient was determined by the response of the previous patient with the biased coin design up-and-down sequential method with an interval of 0.25 μg∙kg^-1.

MEASUREMENTS

Children aged 1-3 years who received pulmonary function testing were involved in this dose-finding trial. Intranasal DEX started at a dose of 2 μg∙kg^-1 on the first patient. The dose of DEX for each subsequent patient was determined by the response of the previous patient with the biased coin design up-and-down sequential method with an interval of 0.25 μg∙kg^-1. The sedation was assessed by the Modified Observer Assessment of Alertness and Sedation (MOAA/S) scale, and recovery was assessed by the modified Aldrete recovery score. The ED₉₅ was calculated using isotonic regression. Other variables, including the sedation onset time, examination time, wake-up time, blood pressure (BP), heart rate (HR), respiratory rate (RR), and oxyhaemoglobin desaturation (SpO₂), were recorded. Adverse events such as hypotension, bradycardia, respiration depression, oxyhaemoglobin desaturation, regurgitation and vomiting were recorded.

MAIN RESULTS

A total of 68 children were enrolled for the study; 62 children had successful sedation, and 6 had failed sedation. The ED₉₅ of intranasal DEX was estimated to be 2.64 μg∙kg^-1 [95% confidence interval (CI), 2.49-2.87 μg∙kg^-1]. The sedation onset time for all patients was 15.0 (12.3-19.0) min. The sedation onset time of successful sedation patients was 15.0 (12.0-19.0) min, the sedation onset time of failed sedation patients was 16.0 (15.0-27.8) min, the examination time was 8 (7-10) min, and the wake-up time was 40 (35-43) min. There were no adverse events during the whole procedure.

CONCLUSION

The ED₉₅ of intranasal DEX sedation in children aged 1-3 years undergoing PFT was 2.64 μg∙kg^-1.

Effect of acute respiratory infections in infancy on pulmonary function test at 3 years of age: a prospective birth cohort study

INTRODUCTION

Acute respiratory infections (ARIs) in infancy may have a long-term impact on the developing respiratory system. We planned a prospective cohort study to determine the impact of ARI during infancy on the pulmonary function test indices at 3 years of age.

METHODS

A cohort of normal, full-term newborns were followed up 6 monthly and during ARI episodes. Infant pulmonary function tests (IPFTs) were performed at baseline and each follow-up visit using tidal breathing flow-volume loop, rapid thoracoabdominal compression (RTC) and raised volume RTC manoeuvres. During each ARI episode, nasopharyngeal aspirates were tested for respiratory pathogens by real-time PCR.

RESULTS

We screened 3421 neonates; 310 were enrolled; IPFT was performed in 225 (boys: 125 (55.6%)) at 3 years. During infancy, 470 ARI episodes were documented in 173 infants. At 3 years, children with history of any ARI episode during infancy had lower forced expiratory volume in 1 s (FEV_1.0), forced expiratory volume in 0.75 s (FEV_0.75), forced expiratory volume in 0.5 s (FEV_0.5), forced expiratory flow between 25% and 75% of FVC (FEF_25-75), and maximal expiratory flow at 25% of FVC (MEF₂₅) as compared with those without any ARI episode during infancy. The ratio of tidal expiratory flow (TEF) at 25% or 50% of tidal expiratory volume to peak TEF (TEF₅₀ or TEF₂₅/peak TEF) at 3 years was significantly increased in children who had ARI in infancy.

CONCLUSIONS

ARI during infancy is associated with impaired pulmonary function indices such as increased resistance and decreased forced expiratory flow and volume at 3 years of age.

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

BACKGROUND

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.

METHODS

Ten tagging SNPs located 10 kb 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.

RESULTS

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 FEV_0.5 (β = -2.411, P = .004) and FEV_0.5 /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 FEV_0.5 among pre-schoolers.

CONCLUSION

CDHR3 is a candidate gene for early-life wheezing, school-age asthma, and lung function in Chinese children.

Post-discharge respiratory outcomes of children with acute respiratory distress syndrome

OBJECTIVES

While long-term sequelae of acute respiratory distress syndrome (ARDS) are well-documented in adults, few studies reported post-discharge respiratory complications in pediatric ARDS (PARDS) and none used the recent Pediatric Acute Lung Injury Consensus Conference (PALICC) diagnostic criteria. This study describes the respiratory symptoms, pulmonary function, and health resource use of PARDS survivors at 3 months post-discharge.

DESIGN

Retrospective study.

PATIENT SELECTION

Children less than 18 years admitted to the intensive care unit of Sainte-Justine University Health Center from 1st September 2015 to 1st July 2017, and meeting PALICC diagnostic criteria for PARDS.

METHODS

We evaluated 38 of the 44 children with PARDS in the follow-up clinic at a mean (SD) of 3.4 (2.0) months post-discharge for respiratory symptoms, age-appropriate pulmonary function tests (spirometry or oscillometry, maximal respiratory pressures), and all-cause emergency department (ED) visits or rehospitalizations since discharge.

RESULTS

Fourteen (36.8%) had abnormal respiratory symptoms (most commonly cough between respiratory infections and wheezing), 7 of whom (18.4%) presented new respiratory symptoms since PARDS diagnosis. A mild-to-moderate restrictive pattern was observed in 3 of 10 patients who performed spirometry and mildly decreased maximal inspiratory pressures were noted in 2 of 8 patients who performed these maneuvers. Nine (23.7%) patients consulted in the ED and 4 (10.5%) were rehospitalized post-discharge.

CONCLUSIONS

Despite our cohort's limited sample size, our findings suggest that a significant proportion of PARDS survivors experience abnormal respiratory symptoms, pulmonary function deficits, and recurrent problems requiring medical attention. Larger, multicenter studies are required to identify risk factors associated with poor post-discharge outcomes among PARDS survivors.

Recurrent wheezing during the first 3 years of life in a birth cohort of moderate-to-late preterm infants

BACKGROUND

Data addressing short- and long-term respiratory morbidity in moderate-late preterm infants are limited. We aim to determine the incidence of recurrent wheezing and associated risk and protective factors in these infants during the first 3 years of life.

METHODS

Prospective, multicenter birth cohort study of infants born at 32⁺⁰ to 35⁺⁰  weeks' gestation and followed for 3 years to assess the incidence of physician-diagnosed recurrent wheezing. Allergen sensitization and pulmonary function were also studied. We used multivariate mixed-effects models to identify risk factors associated with recurrent wheezing.

RESULTS

A total of 977 preterm infants were enrolled. Rates of recurrent wheezing during year (Y)1 and Y2 were similar (19%) but decreased to 13.3% in Y3. Related hospitalizations significantly declined from 6.3% in Y1 to 0.75% in Y3. Independent risk factors for recurrent wheezing during Y2 and Y3 included the following: day care attendance, acetaminophen use during pregnancy, and need for mechanical ventilation. Atopic dermatitis on Y2 and male sex on Y3 were also independently associated with recurrent wheezing. Palivizumab prophylaxis for RSV during the first year of life decreased the risk or recurrent wheezing on Y3. While there were no differences in rates of allergen sensitization, pulmonary function tests (FEV_0.5 ) were significantly lower in children who developed recurrent wheezing.

CONCLUSIONS

In moderate-to-late premature infants, respiratory symptoms were associated with lung morbidity persisted during the first 3 years of life and were associated with abnormal pulmonary function tests. Only anti-RSV prophylaxis exerted a protective effect in the development of recurrent wheezing.

Cross-sectional phenotyping of small airway dysfunction in preschool asthma using the impulse oscillometry system

Objective. Asthma is a chronic inflammatory airway disorder known to induce small airways dysfunction (SAD). It is important to develop tools to assess the presence and extent of SAD in daily clinical practice. An Impulse Oscillometry System (IOS) might detect SAD, but the validity of the underlying model (serial Resistive airway and Compliant tissue model: RC model) in diseased lungs remains questionable.Methods. Our objective was to evaluate the usefulness of parameters obtained from six electrical circuit models that were fitted to the measurements of impedance obtained with IOS in asthmatic children characterized by an abnormal lung function defined by an increased baseline interrupter resistance (Rint, z-score > +1.645).Results. The six models were tested in 102 asthmatic children (median age: 5.5 years). Two models allowed the description of 92/102 (90%) children: 74 by the extended RIC model (central and peripheral Resistance, Inertance and peripheral airway Compliance) and 18 by the Mead₁₉₆₉ model (extended RIC plus lung compliance). Thus, peripheral airway compliance and resistance were essential to describe lung function abnormalities of these asthmatic children. Parenchyma impairment (increased lung compliance) which was responsive to salbutamol was present in 18% of asthmatic children. After salbutamol, peripheral airway resistance decreased while peripheral airway compliance increased, arguing for asthma-related SAD. R5-20Hz independently correlated with the two latter parameters but was increased in two thirds of children with increased Rint only.Conclusion. Additional modeling of IOS results can be a reliable tool to assess the presence and extent of SAD in young asthmatic children.

Longitudinal trajectories of severe wheeze exacerbations from infancy to school age and their association with early-life risk factors and late asthma outcomes

INTRODUCTION

Exacerbation-prone asthma subtype has been reported in studies using data-driven methodologies. However, patterns of severe exacerbations have not been studied.

OBJECTIVE

To investigate longitudinal trajectories of severe wheeze exacerbations from infancy to school age.

METHODS

We applied longitudinal k-means clustering to derive exacerbation trajectories among 887 participants from a population-based birth cohort with severe wheeze exacerbations confirmed in healthcare records. We examined early-life risk factors of the derived trajectories, and their asthma-related outcomes and lung function in adolescence.

RESULTS

498/887 children (56%) had physician-confirmed wheeze by age 8 years, of whom 160 had at least one severe exacerbation. A two-cluster model provided the optimal solution for severe exacerbation trajectories among these 160 children: "Infrequent exacerbations (IE)" (n = 150, 93.7%) and "Early-onset frequent exacerbations (FE)" (n = 10, 6.3%). Shorter duration of breastfeeding was the strongest early-life risk factor for FE (weeks, median [IQR]: FE, 0 [0-1.75] vs. IE, 6 [0-20], P < .001). Specific airway resistance (sR_aw ) was significantly higher in FE compared with IE trajectory throughout childhood. We then compared children in the two exacerbation trajectories with those who have never wheezed (NW, n = 389) or have wheezed but had no severe exacerbations (WNE, n = 338). At age 8 years, FEV₁ /FVC was significantly lower and FeNO significantly higher among FE children compared with all other groups. By adolescence (age 16), subjects in FE trajectory were significantly more likely to have current asthma (67% FE vs. 30% IE vs. 13% WNE, P < .001) and use inhaled corticosteroids (77% FE vs. 15% IE vs. 18% WNE, P < .001). Lung function was significantly diminished in the FE trajectory (FEV₁ /FVC, mean [95%CI]: 89.9% [89.3-90.5] vs. 88.1% [87.3-88.8] vs. 85.1% [83.4-86.7] vs. 74.7% [61.5-87.8], NW, WNE, IE, FE respectively, P < .001).

CONCLUSION

We have identified two distinct trajectories of severe exacerbations during childhood with different early-life risk factors and asthma-related outcomes in adolescence.

Preoperative Pulmonary Function Test Results Are Not Associated With Postoperative Intubation in Children Undergoing Posterior Spinal Fusion for Scoliosis: A Retrospective Observational Study

BACKGROUND

Preoperative pulmonary function tests are routinely obtained in children with scoliosis undergoing posterior spinal fusion despite unclear benefits as a perioperative risk assessment tool and frequent inability of patients to provide acceptable results. The goal of this study was to determine whether preoperative pulmonary function test results are associated with the need for postoperative intubation or intensive care unit admission after posterior spinal fusion.

METHODS

The electronic medical records of patients who underwent posterior spinal fusion at a pediatric tertiary hospital between June 2012 and August 2017 were reviewed. Pulmonary function tests were consistently ordered for all patients, unless the patient was deemed unable to perform the test due to cognitive disability. Cases were categorized as primary or secondary scoliosis.Demographic data, preoperative bilevel positive airway pressure use, Cobb angle, intraoperative allogeneic blood transfusion, and ability to produce acceptable pulmonary function test results were collected for each patient. In patients with satisfactory pulmonary function test results, forced vital capacity and maximum inspiratory pressure were collected. Primary outcomes for analysis were postoperative intubation and intensive care unit admission. Univariable logistic regression models were used to assess the association between each variable of interest and the primary outcomes.

RESULTS

The study sample included 433 patients, 288 with primary scoliosis and 145 with secondary scoliosis. Among patients with primary scoliosis, 90% were able to produce acceptable pulmonary function test results, zero remained intubated postoperatively, and 6 were admitted to the intensive care unit. Among patients with secondary scoliosis, 44% could not attempt pulmonary function tests. Among those who did attempt the test, 30% were unable to produce meaningful results. Forced vital capacity and maximum inspiratory pressure were not found to be associated with postoperative intubation or intensive care unit admission. Weight, Cobb angle, intraoperative blood transfusion, American Society of Anesthesiologists physical status classification, and preoperative bilevel positive airway pressure use were associated with patient outcomes. Among 357 total patients who attempted pulmonary function tests, 37 had high-risk results. Only 1 of these 37 patients remained intubated postoperatively.

CONCLUSIONS

Patients undergoing posterior spinal fusion, especially those with secondary scoliosis, are frequently unable to adequately perform pulmonary function tests. Among patients with interpretable pulmonary function tests, there was no association between results and postoperative intubation or intensive care unit admission. Routine pulmonary function testing for all patients with scoliosis may not be indicated for purposes of risk assessment before posterior spinal fusion. Clinicians should consider a targeted approach and limit pulmonary function tests to patients for whom results may guide preoperative optimization as this may improve outcomes and reduce inefficiencies and costs.

Evolution and Determinants of Lung Function until Late Infancy among Infants Born Preterm

To investigate the evolution of lung function in preterm infants with and without bronchopulmonary dysplasia (BPD) and to determine the perinatal characteristics associated with indexes of lung function in later infancy. Longitudinal lung function assessments were performed at approximately 6, 12, 18, and 24 months of corrected age in preterm infants. Perinatal characteristics were further analyzed to ascertain the determinants of lung function indexes. Although all preterm infants (n = 121; 61 without BPD and 60 with BPD) exhibited decreased lung function in early infancy (6 months of age), after body length was adjusted for, only infants with BPD exhibited poor performance. Furthermore, the lung function of infants with mild to moderate BPD caught up gradually, but the generally poor lung function performance of infants with severe BPD, especially in forced expiratory flow, persisted until later age (24 months). Regarding perinatal characteristics, the z-score of body length at the time of examination and total number of days on positive-pressure ventilation are the major determinants of lung function in later infancy.

Relationship between baseline and post-bronchodilator interrupter resistance and specific airway resistance in preschool children

BACKGROUND

The assessment of airway function in preschool children can be done using simple measurement techniques such as interrupter resistance (Rint) or specific airway resistance (sRaw).

OBJECTIVE

The aim of the study was to assess the relationship and the agreement between Rint and sRaw baseline measurements expressed in z-score and bronchodilator response (BDR) in accordance with the latest reference equations and recommended procedures.

METHODS

One hundred thirty children aged 3 to 6 years old, referred to our pediatric pulmonary function test unit for assessment of airway function were consecutively included. Children performed baseline and post-bronchodilator measurements of Rint and sRaw.

RESULTS

One hundred twenty baseline measurements were obtained (98.7%) with both techniques. At baseline there was a strong correlation between Rint and sRaw z-score (r = 0.5, P < .01) despite the poor agreement (Cohen Kappa coefficient 0.09 [-0.08; 0.26]). The agreement for BDR was fair, with Cohen Kappa coefficient (95% IC) = 0.33 (0.13; 0.54). Children with poorly or partially controlled asthma had both higher baseline Rint and sRaw (P < .01), and higher post-bronchodilator mean change (P < .01), than children with well-controlled asthma.

CONCLUSION

The poor agreement between the Rint and sRaw reference measurements demonstrates the lack of reliability of sole Rint or sRaw technique for airway obstruction diagnosis and the need to perform each technique concomitantly with BDR test. Other longitudinal and larger sample studies are needed to confirm the threshold value for a positive BDR, especially for sRaw.

Proximity to major roadways and asthma symptoms in the School Inner-City Asthma Study

BACKGROUND

Traffic proximity has been associated with adverse respiratory health outcomes. Less is known about the combined impact of residential and school exposures on pediatric asthma.

OBJECTIVE

We sought to use spatial analysis methodology to analyze residential and school proximity to major roadways and pediatric asthma morbidity.

METHODS

The School Inner-City Asthma Study (n = 350) recruited school-aged children with asthma. Each participant's school and home addresses were geocoded, and distances from major roadways were measured to calculate a composite measure accounting for both home and school traffic exposure. Generalized estimating equation models were clustered by subject and adjusted for age, race/ethnicity, sex, income, environmental tobacco smoke, controller medication, upper respiratory tract infections, and seasonality.

RESULTS

The majority of participants (62%) attended schools within 100 m from major roadways, and 40% also resided within 100 m of major roadways. In multivariate analyses major roadway proximity was independently associated with increased asthma symptom days. At greater than the threshold of 100 m, children had 29% less odds of a symptom day over the past 2 weeks for each 100-m increase in distance from a major roadway (odds ratio, 0.71; 95% CI, 0.58-0.87; P < .01). Children farther from a major roadway also had significantly less reported health care use (odds ratio, 0.63; 95% CI, 0.47-0.85; P < .01) and were significantly less likely to have poor asthma control (odds ratio, 0.80; 95% CI, 0.69-0.94; P < .01). There was not a meaningful association between distance to a major roadway and lung function outcomes.

CONCLUSIONS

Proximity to a major roadway, a composite measure of home and school exposure but primarily driven by home exposure, was associated with greater asthma morbidity. More studies are needed to evaluate the independent effect of school distance to a roadway on asthma morbidity.

Longitudinal Analysis of Pulmonary Function in Survivors of Congenital Diaphragmatic Hernia

OBJECTIVE

To analyze longitudinal trends of pulmonary function testing in patients with congenital diaphragmatic hernia (CDH) followed in our multidisciplinary clinic.

STUDY DESIGN

This was a retrospective cohort study of CDH patients born between 1991 and 2013. A linear mixed effects model was fitted to estimate the trends of percent predicted forced expiratory volume in 1 second (FEV₁pp), percent predicted forced vital capacity (FVCpp), and FEV₁/FVC over time.

RESULTS

Of 268 patients with CDH who survived to discharge, 119 had at least 1 pulmonary function test study. The FEV₁pp (P < .001), FVCpp (P = .017), and FEV₁/FVC (P = .001) decreased with age. Compared with defect size A/B, those with defect size C/D had lower FEV₁pp by an average of 11.5% (95% CI, 2.9%-20.1%; P = .010). A history of oxygen use at initial hospital discharge also correlated with decreased FEV₁pp by an average of 8.0% (95% CI, 1.2%-15.0%; P = .023).

CONCLUSIONS

In a select cohort of CDH survivors, average pulmonary function declines with age relative to expected population normative values. Those with severe CDH represent a population at risk for worsening pulmonary function test measurements who may benefit from recognition and monitoring for complications.

Forced expiratory flows and volumes in a Swedish cohort of healthy term infants

BACKGROUND

The use of pulmonary function tests (PFTs) in infants has increased during the last decades, making the need for equipment- and ethnic-specific reference data mandatory for appropriate interpretation of the results.

AIM

Our aim was to investigate how well the already published reference equations for infant spirometry fit a healthy population of Swedish infants.

METHOD

We performed forced tidal and raised volume expiratory maneuvers in healthy infants using Jaeger BabyBody equipment.

RESULTS

PFT data were collected from 91 healthy infants aged between 3 months to 2 years at 143 occasions. Mean (standard deviation) z-scores were 0.68(1.33) for maximal flow at functional residual capacity (V'_max FRC), -0.15(0.96) for forced vital capacity (FVC), 0.40(1.33) for the forced expired volume in the initial 0.5 seconds (FEV_0.5 ) and 0.52(0.93) for the ratio FEV_0.5 /FVC, respectively. Z-scores for all indices but FEV_0.5 /FVC were highly dependent on length.

CONCLUSIONS

We have shown that the use of previously published reference equations may result in an age-related misinterpretation of lung function measure in a Swedish infant population.

Comparison of oscillometry devices using active mechanical test loads

Noninvasiveness, low cooperation demand and the potential for detailed physiological characterisation have promoted the use of oscillometry in the assessment of lung function. However, concerns have been raised about the comparability of measurement outcomes delivered by the different oscillometry devices. The present study compares the performances of oscillometers in the measurement of mechanical test loads with and without simulated breathing.

Six devices (five were commercially available and one was custom made) were tested with mechanical test loads combining resistors (R), gas compliances (C) and a tube inertance (L), to mimic respiratory resistance (R_rs) and reactance (X_rs) spectra encountered in clinical practice. A ventilator was used to simulate breathing at tidal volumes of 300 and 700 mL at frequencies of 30 and 15 min⁻¹, respectively. Measurements were evaluated in terms of R, C, L, resonance frequency (f_res), reactance area (A_X) and resistance change between 5 and 20 or 19 Hz (R_5–20(19)).

Increasing test loads caused progressive deviations in R_rs and X_rs from calculated values at various degrees in the different oscillometers. While mean values of R_rs were recovered acceptably, some devices exhibited serious distortions in the frequency dependences of R_rs and X_rs, leading to large errors in C, L, f_res, A_X and R_5–20(19). The results were largely independent of the simulated breathing.

Simplistic calibration procedures and mouthpiece corrections, in addition to unknown instrumental and signal processing factors, may be responsible for the large differences in oscillometry measures. Rigorous testing and ongoing harmonisation efforts are necessary to better exploit the diagnostic and scientific potential of oscillometry.

The clinical utility of oscillometry is limited by the lack of standardisation of devices. This study tested six oscillometers, and reveals very different performances at higher mechanical impedances observed in children and adults with lung disease.http://bit.ly/317sfjH

The sensitivity and specificity of the forced oscillation technique in the diagnosis of bronchoconstriction in children

OBJECTIVE

The forced oscillation technique (FOT) is a useful diagnostic respiratory system for children. However, the final value of the FOT in the diagnosis of bronchoconstriction is still open. The aim of the study was to evaluate the sensitivity and specificity of the FOT vs. body plethysmography tests in the measure of bronchoconstriction in asthmatic children.

MATERIALS AND METHODS

A total of 102 children aged 2 to 6 years diagnosed with early-onset asthma and 52 healthy controls were included in this prospective, randomized study. All asthmatic patients and healthy controls underwent a basic FOT as one measurement, according to the recommendation of the Resmon Pro FOT. Then, the reversibility test was performed 20 min after the administration of 200 mg salbutamol using the FOT and body plethysmography in all patients.

RESULTS

The mean basic Rrs, Xrs and sRaw in asthmatic patients were, respectively, 11.13 ± 1.28 kPa sL^-1, -4.6 ± 1.18 kPa sL^-1 and 1.72 ± 0.58 kPa s. Similar parameters were significantly better in the control group (p < 0.05). A total of 73 (71.6%) asthmatic patients had a positive test using the FOT according to Calogero. In 4 (7.7%) patients in the control group, a positive test was obtained. In body plethysmography, similar results were reached, with a positive test in 76 (74.5%) study patients and 5 (9.6%) control patients.

CONCLUSIONS

A bronchial reversibility test with the use of the FOT is useful for the diagnosis of bronchial asthma, especially with the use of an Rrs parameter, such as the body plethysmography test.

Recent Diagnosis Techniques in Pediatric Asthma: Impulse Oscillometry in Preschool Asthma and Use of Exhaled Nitric Oxide

Objective measures of lung function are important in the diagnosis and management of asthma. Spirometry, the pulmonary function test most widely used in asthma, requires respiratory maneuvers that may be difficult for preschoolers. Impulse oscillometry (IOS) is a noninvasive method of measuring lung function during tidal breathing; hence, IOS is an ideal test for use in preschool asthma. Fractional exhaled nitric oxide (FeNO) levels correspond to eosinophilic inflammation and predict responsiveness to corticosteroids. Basic concepts of IOS, methodology, and interpretation, including available normative values, and recent findings regarding FeNO are reviewed in this article.

Severe Asthma in Childhood

Severe asthma is broadly defined as asthma requiring a high level of therapy, usually high doses of inhaled corticosteroids, to bring under control. Children who remain symptomatic despite such treatment are a heterogeneous population, and bear a high burden of disease and require high resource utilization. Children with severe asthma require a comprehensive evaluation, careful consideration of alternative diagnoses and comorbid conditions, assessment of medication adherence and environmental conditions, and frequent disease monitoring.

Does Pseudomonas aeruginosa Colonization Affect Exercise Capacity in CF?

Introduction

Cardio-Pulmonary Exercise Testing (CPET) has been recognized as a valuable method in assessing disease burden and exercise capacity among CF patients.

Aim

To evaluate whether Pseudomonas aeruginosa colonization status affects Exercise Capacity, LCI and High-Resolution Computed Tomography (HRCT) indices among patients with CF; to check if Pseudomonas colonization can predict exercise intolerance.

Subjects

Seventy-eight (78) children and adults with CF (31 males) mean (range) age 17.08 (6.75; 24.25) performed spirometry, Multiple Breath Washout (MBW) and CPET along with HRCT on the same day during their admission or follow up visit.

Results

78 CF patients (mean FEV1: 83.3% mean LCI: 10.9 and mean VO₂ peak: 79.1%) were evaluated: 33 were chronically colonized with Pseudomonas aeruginosa, 24 were intermittently colonized whereas 21 were Pseudomonas free. Statistically significant differences were observed among the three groups in: peak oxygen uptake % predicted (VO₂ peak% (p < 0.001), LCI (p < 0.001), as well as FEV1% (p < 0.001) and FVC% (p < 0.001). Pseudomonas colonization could predict VO₂ peak% (p < 0.001, r²: −0.395).

Conclusion

Exercise capacity as reflected by peak oxygen uptake is reduced in Pseudomonas colonized patients and reflects lung structural damages as shown on HRCT. Pseudomonas colonization could predict exercise limitation among CF patients.

Serum chitinase-like protein YKL-40 is linked to small airway function in children with asthmatic symptoms

BACKGROUND

Lung function impairment among asthmatic children begins in early life, and biomarkers for identifying this impairment are needed. The chitinase-like protein YKL-40 has been associated with asthma and lung function in adults, but studies in children have yielded conflicting results. We evaluated the potential of YKL-40 and other systemic biomarkers for identifying lung function deficits in children with asthmatic symptoms.

METHODS

We determined the levels of serum YKL-40, periostin, and high-sensitivity C-reactive protein (hs-CRP) from the blood samples of 49 children with asthmatic symptoms. Lung function was assessed with impulse oscillometry (IOS) and spirometry, combined with an exercise challenge and a bronchodilator test. Fractional exhaled nitric oxide was measured at multiple flow rates.

RESULTS

Serum levels of YKL-40 showed significant correlations with most IOS indices at baseline (P = .008-.039), but there was no association between YKL-40 and spirometry parameters. Neither periostin nor hs-CRP were associated with baseline lung function. Children with a significant response in either the exercise challenge or the bronchodilator test had increased serum levels of YKL-40 (P = .003) and periostin (P = .035). YKL-40 correlated significantly with the blood neutrophil count (r_s  = .397, P = .005) but was not associated with biomarkers of eosinophilic inflammation.

CONCLUSION

Serum YKL-40 is a potential biomarker for lung function deficits in children with asthmatic symptoms. These deficits appear to be focused on small airways and may remain undetected with spirometry.

Lung clearance index: assessment and utility in children with asthma

There is increasing evidence that ventilation heterogeneity and small airway disease are significant factors in asthma, with evidence suggesting that the small airways are involved from an early stage in childhood asthma. Spirometry is commonly used to monitor lung function in asthmatics; however, it is not sensitive to small airway disease. There has been renewed interest in multibreath washout (MBW) tests, with recognition of the lung clearance index (LCI) as a global index of abnormality in gas mixing of the lungs that therefore also reflects small airway disease. This review summarises the technical and practical aspects of the MBW/LCI in children, and the differences between commercially available equipment. Children with severe asthma are more likely to have an abnormal LCI, whereas most children with mild-to-moderate asthma have an LCI within the normal range, but slightly higher than age-matched healthy controls. Monitoring children with asthma with MBW alongside standard spirometry may provide useful additional information.

Association between prenatal exposure to perfluoroalkyl substances and asthma in 5-year-old children in the Odense Child Cohort

BACKGROUND

Asthma is the most common non-communicable disease in children. Prenatal exposure to perfluoroalkyl substances (PFASs), a group of persistent environmental chemicals with endocrine disrupting abilities, has been associated with immunomodulation and may contribute to the aetiology of asthma. We investigated the associations between prenatal exposure to five PFASs and asthma in 5-year-old children.

METHODS

We studied 981 mother-child pairs within the Odense Child Cohort (OCC), Denmark. We measured perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonic acid (PFHxS), perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA) in maternal serum donated in early pregnancy. A standardized questionnaire based on the International Study of Asthma and Allergies in Childhood (ISAAC) was used to assess wheeze, self-reported asthma and doctor-diagnosed asthma among children at age 5 years. Associations were examined using logistic regression analyses adjusting for parity, maternal educational level, maternal pre-pregnancy BMI, asthma predisposition and child sex.

RESULTS

Among the 5-year-old children 18.6% reported wheeze and 7.1% reported asthma. We found no association between prenatal exposure to PFAS and doctor-diagnosed asthma or wheeze. Prenatal PFAS exposure was associated with self-reported asthma, although only significant for PFNA (OR = 1.84, 95% CI 1.03,3.23).

CONCLUSION

Our findings support the suggested immunomodulatory effects of PFASs, however, additional studies are warranted. In order to verify our findings, it is important to re-examine the children with postnatal measurements of serum PFAS concentrations and additional clinical diagnostic testing at an older age where an asthma diagnosis is more valid.