Forced expiratory flow between 25% and 75% of vital capacity and FEV1/forced vital capacity ratio in relation to clinical and physiological parameters in asthmatic children with normal FEV1 values

A 12-week double-blind randomised controlled trial investigating the effect of dietary supplementation with 125 μg/d vitamin D in adults with asthma

Vitamin D deficiency has previously been linked to higher rates of exacerbation and reduced lung function in asthmatics. Previous randomised controlled trials investigating the effect of vitamin D supplementation have mainly focused on children with asthma. Trials involving adults have typically used bolus dosing regimens, and the main outcomes have been patient-focused without investigating underlying inflammation. The present study aimed to conduct a 12-week placebo-controlled randomised controlled trials administering a daily 125 µg vitamin D3 supplement to adults with mild to moderate asthma. A total of 32 participants were randomised to receive either the 125 μg vitamin D3 supplement or an identical matching placebo. The primary outcome of the study was lung function measured by the ratio of FEV1:FVC (effect size 2·5) with secondary outcomes including asthma symptoms and inflammatory biomarkers. There was a small but statistically significant higher increase in the mean (±sd) ratio of FEV1:FVC from baseline to post-intervention in the vitamin D group (+0·05 ± 0·06) compared with the placebo group (+0·006 ± 0·04, P = 0·04). There was no effect of the intervention on asthma control test scores, or the inflammatory biomarkers measured. There was a moderate, significant association between baseline plasma 25(OH)D concentration and baseline plasma IL-10 (r = 0·527, P = 0·005) and TNF-α (r = −0·498. P = 0·008) concentrations. A daily vitamin D3 supplement led to slightly improved lung function in adult asthmatics and may be a useful adjunct to existing asthma control strategies, particularly for individuals with suboptimal vitamin D status.

Covert airflow obstruction dominates the overt ones in interstitial lung disease: An appraisal

Background & objectives The co-presence of non-emphysematous airflow obstruction in interstitial Lung disease (ILD) is not elaborated. The present study aims the job with spirometry. Methods ILD affected individuals with or without airflow obstruction (FEV1/FVC<0.7 or >0.7) on spirometry were compared in terms of FEV1 and FEF25-75 derived variables [FEF25-75 (%-predicted), FEV1-FEF25-75 distance, reversibility of FEV1 and FEF25-75 to salbutamol and change in FEV1 and FEF25-75 in %-predicted values]. Those showing significant difference (P=0.0001) suggesting obstruction were selected to draw respective receiver operating curve (ROC) curves to identify the best cut-off value for individual parameters. The efficacy of each surrogate was tested to identify airflow obstruction in both the initial 'overlap' as well as the 'unmixed' ILD affected individual for the presence of airflow obstruction. Results FEV1/FVC identified 30 overlap from 235 ILDs. The FEF25-75 (%-predicted), FEV1-FEF25-75 distance, FEF25-75 reversibility (in ml) and FEV1 (%-predicted) were significantly (P<0.0001) different between the two groups. Of these, the FEF25-75 (%-predicted) had high specificity and sensitivity (93.33 and 79.47%) to identify airflow limitation in the initial unmixed ILD-group. The surrogates with their cut off values identified 92 extra individuals making it 122/235 (51.91%) of ILD having airflow obstruction. The 'unmixed' group showed higher frequency and degree of FEV1 reversibility. Interpretation & conclusions The findings of this study suggest that the airflow obstruction in ILD involves both the intrathoracic large and small airways. Although seemingly parallel, their relative status (qualitative and quantitative) needs research especially in light of the a etio pathology and the extent of involvement of ILD.

Alveolar nitric oxide concentration plays an important role in identifying cough variant asthma and assessing asthma control in children

OBJECTIVE

To study the value of alveolar nitric oxide concentration (CaNO) in the identification and disease control of cough variant asthma.

METHODS

A retrospective study was conducted on cough variant asthma (CVA-Group), nonasthmatic cough (NAC-Group) and healthy control children (C-Group) aged 5-12 years. The exhaled nitric oxide and spirometry test results of the three groups were collected and compared.

RESULTS

A total of 410 children were included in this study, including 190 in the CVA-Group, 183 in the NAC-Group, and 37 in the C-Group. The CaNO values of the CVA-Group [11.40 ppb (8.48-14.25)] were significantly higher than those of the NAC-Group and C-Group (all p values <.05). The MMEF %pred values of the CVA-Group [63.65 (56.28-73.58)] were significantly lower than those of the NAC-Group and C-Group (all p values <.05). FeNO50, JawNO and other spirometry indices (FVC %pred, FEV1%pred, FEV1/FVC %pred) showed no significant difference among the three groups. ROC curve analysis showed that the optimal cutoff point value of CaNO was 9.45 ppb, corresponding to 0.816 sensitivity and 0.736 specificity. Spearman correlation analysis showed a significant negative correlation between the CaNO measurement and CVA control score.

CONCLUSIONS

CaNO can not only help identify CVA early in children aged 5-12 years with chronic cough but is also significantly negatively correlated with the CVA control score.

Establishment and application of reference equations for FEF50 and FEF75 in the Chinese population

Background

Reference equations for forced expiratory flow at 50% and 75% of forced vital capacity (FVC) (FEF50 and FEF75) in the Chinese population are lacking. It is of great importance to establish equations covering most age groups and to study their applicability in clinical practice.

Methods

Using the lambda-mu-sigma (LMS) method, reference equations for FEF50 and FEF75 were constructed based on pulmonary function data from healthy subjects collected from January 2007 to June 2010 at 24 centers throughout China. Differences between the established equations and extraneous equations were compared using standardized means (Z values) and percentage errors (PE). The proportion of small airway dysfunction (SAD) defined by the present equations was calculated. The Fisher precision probability test and the Mann-Whitney test were used to analyze the magnitude of changes in small and large airway indices after bronchodilator inhalation in patients with suspected asthma and chronic obstructive pulmonary disease (COPD).

Results

Reference equations for FEF50 and FEF75 were established based on data from 7,115 healthy individuals (aged 4 to 80 years, 50.9% female, height between 95 and 190 cm). The present equations (all Z values were -0.0 and PE ranged from 2.0% to 4.2%) showed advantages over the European Community for Steel and Coal (ECSC) equations in 1993 (with Z values ranging from -0.7 to -0.2 and PE ranged from -23.4% to -4.5%). A total of 4,356 patients with suspected asthma (51.1% female; a mean age of 45.4 years) and 6,558 patients with suspected COPD (10.1% female; a mean age of 65.0 years) were included. The present equations defined 95.7% and 99.9% of SAD in these patients. After bronchodilator inhalation, greater mean improvement rates in small airway indices were observed both in patients with suspected asthma [mean ± standard deviation (SD) =48%±47%] and in patients with suspected COPD (mean ± SD =20%±30%) (P<0.05).

Conclusions

The reference equations for FEF50 and FEF75 established in this study should be considered for use in China. Further studies are needed to validate their value in the diagnosis of some chronic respiratory diseases.

A Longitudinal Study of a Selected Pediatric Asthmatic Population with Normal and Abnormal Spirometry at Baseline: An Emphasis on Treatment Outcomes

Purpose

It is still unclear whether considering abnormal spirometry as a marker for disease control can help physicians adjust asthma controllers in children because of the scarcity of pediatric studies. We aimed to investigate the prevalence of abnormal spirometry in a selected pediatric asthmatic population and its effect on longitudinal outcomes.

Patients and Methods

This retrospective cohort study was conducted at the Songklanagarind Hospital, Thailand. Children with asthma aged <18 years were recruited for review if they attended the clinic and underwent acceptable spirometry with bronchodilator responsiveness (BDR) tests after receiving asthma treatment for at least 3 months between January 2011 and June 2022. Differences in baseline characteristics, atopic factors, asthma treatment, and outcomes were analyzed between the normal and abnormal spirometry groups over a 12-month post-spirometry period.

Results

The mean age of the 203 enrolled patients was 10.9 ± 2.6 years. Abnormal spirometry, defined as airflow limitation or the presence of BDR, was observed in 58.1% of patients. No significant differences were observed in baseline characteristics, atopic factors, asthma treatment, or outcomes between the normal and abnormal spirometry groups. Further analysis of 107 patients with abnormal spirometry with symptom control revealed that physicians adjusted the asthma controller based on spirometry and symptoms in 84 and 23 patients, respectively. There was no significant difference in the loss of disease control over the 12-month post-spirometry period between the two groups.

Conclusion

Abnormal spirometry was found in 58.1% of treated school-aged patients with asthma. Abnormal spirometry results were not associated with poor asthma outcomes during the 12-month follow-up. Both symptom-based and spirometry-based adjustments of asthma controllers resulted in comparable symptom control over a 12-month follow-up period in the selected population.

Role of FEF25-75 in characterizing outpatients with asthma in clinical practice

BACKGROUND

Asthma is characterized by variable airflow limitation. FEF25-75 has been proposed as a reliable marker for bronchial obstruction, especially when FEV1 and FEV1/FVC are normal.

OBJECTIVES

To investigate the role of FEF25-75 in patients with asthma seen in clinical settings.

MATERIALS AND METHODS

The cross-sectional study included 439 (181 females and 255 males; mean age 39 years) outpatients with asthma who consecutively visited an allergy clinic for a routine assessment. History, physical examination, asthma control, and spirometry were evaluated.

RESULTS

FEF25-75 was impaired (< 65% of predicted) in 136 (31%) outpatients. Considering only subjects with normal FEV1 and FEV1/FVC, FEF25-75 was impaired in 71 (19.6%) subjects. In this subset, impaired FEF25-75 was associated with low FEV1 and FEV1/FVC values (OR 0.91 and 0.85, respectively), and presence of asthma symptoms (OR 2.19).

CONCLUSION

FEF25-75 deserves adequate and careful consideration in patients with asthma and normal FEV1 and FEV1/FVC, as the presence of impaired FEF25-75 in this subset suggests a more specific approach.

Novel Artificial Intelligence-Based Technology to Diagnose Asthma Using Methacholine Challenge Tests

PURPOSE

The methacholine challenge test (MCT) has high sensitivity but relatively low specificity for asthma diagnosis. This study aimed to develop and validate machine learning (ML) models to improve the diagnostic performance of MCT for asthma.

METHODS

Data from 1,501 patients with asthma symptoms who underwent MCT between 2015 and 2020 were analyzed. The patients were grouped as either the training (80%, n = 1,265) and test sets (20%, n = 236) depending on the time of referral. The conventional model (provocative concentration that causes a 20% decrease in forced expiratory volume in one second [FEV1]; PC20 ≤ 16 mg/mL) was compared with the prediction models derived from five ML methods: logistic regression, support vector machine, random forest, extreme gradient boosting, and artificial neural network. The area under the receiver operator characteristic curves (AUROC) and area under the precision-recall curves (AUPRC) of each model were compared. The prediction models were further analyzed using different input combinations of FEV1, forced vital capacity (FVC), and forced expiratory flow at 25%-75% of forced vital capacity (FEF25%-75%) values obtained during MCT.

RESULTS

In total, 545 patients (36.3%) were diagnosed with asthma. The AUROC of the conventional model was 0.856 (95% confidence interval [CI], 0.852-0.861), and the AUPRC was 0.759 (95% CI, 0.751-0.766). All the five ML prediction models had higher AUROC and AUPRC values than those of the conventional model, and random forest showed both highest AUROC (0.950; 95% CI, 0.948-0.952) and AUROC (0.909; 95% CI, 0.905-0.914) when FEV1, FVC, and FEF25%-75% were included as inputs.

CONCLUSIONS

Artificial intelligence-based models showed excellent performance in asthma prediction compared to using PC20 ≤ 16 mg/mL. The novel technology could be used to enhance the clinical diagnosis of asthma.

Sex-Linked Differences in Pulmonary Functions of COVID-19 Patients After a Six-Minute Walk Test

Coronavirus disease 2019 (COVID-19) predominantly impacts the respiratory system. Historically, numerous lung diseases have shown sex-related differences throughout their progression. This study aimed to identify sex-linked disparities in pulmonary function tests (PFTs) among individuals who have recovered from COVID-19 when subjected to a six-minute walk test (6MWT). In this observational cross-sectional study, we analyzed 61 participants, consisting of 39 (64%) males and 22 (36%) females, all of whom previously contracted COVID-19 three months or more prior. We measured vitals such as blood pressure, pulse, oxygen saturation, and PFT values before and after the 6MWT. The post-6MWT evaluation revealed notable mean differences between males and females in parameters systolic blood pressure (SBP) (p = 0.003), diastolic blood pressure (DBP) (p = 0.026), forced expiratory volume in the first second (FEV1) (p = 0.038), forced vital capacity (FVC) (p = 0.041), and maximum voluntary ventilation (MVV) index (p = 0.011). PFT outcomes indicated sex-based variations among post-COVID-19 subjects. Specifically, post-stress values for FEV1, FVC, MVV index, SBP, and DBP were more elevated in males than in females. However, females presented with higher oxygen saturation levels post-COVID-19 compared to males. Using multiple linear regression modeling, sex was not found to be a strong predictor of PFT results. However, individual regression analyses for FEV1, FVC, and MVV index consistently showcased higher values in males. In conclusion, significant PFT differences exist between males and females after recovery from COVID-19 when exposed to stress induction via the 6MWT.

Comparison of Pulmonary Functions After Induction of Stress Between Post-COVID and Healthy Adults

Since the emergence of COVID in 2019, it has spread worldwide. COVID has affected all the systems of the human body. The present research aimed to assess the effects of COVID-19 on the pulmonary system after stress induction. Healthy and affected individuals between the age of 18 and 40 years were made to perform the 6-minute walk test and their pulmonary functions were compared before and after the stressor. Individuals who were three months post-COVID-19 infection were included as cases. Healthy individuals with no history of COVID were included as controls. The pulmonary functions were performed and noted both at baseline and after the 6-minute walk test. The forced expiratory flow 25 (FEF 25) and peak expiratory flow (PEF) showed statistical significance between both groups (p=0.033 and p=0.007, respectively). FEF 25, 50, and 75, maximum voluntary ventilation (MVV) index, and PEF were positively correlated with all respiratory parameters. Forced expiratory volume % (FEV%) was negatively correlated with vital capacity (VC) and forced vital capacity (FVC). This research helped us establish that the effect on the lungs due to COVID is not due to airway restriction or obstruction but reduced lung volume.

The role of small airway function parameters in preschool asthmatic children

BACKGROUND

Small airways are the major sites of inflammation and airway remodeling in all severities of asthma patients. However, whether small airway function parameters could reflect the airway dysfunction feature in preschool asthmatic children remain unclear. We aim to investigate the role of small airway function parameters in evaluating airway dysfunction, airflow limitation and airway hyperresponsiveness (AHR).

METHODS

Eight hundred and fifty-one preschool children diagnosed with asthma were enrolled retrospectively to investigate the characteristics of small airway function parameters. Curve estimation analysis was applied to clarify the correlation between small and large airway dysfunction. Spearman's correlation and receiver-operating characteristic (ROC) curves were employed to evaluate the relationship between small airway dysfunction (SAD) and AHR.

RESULTS

The prevalence of SAD was 19.5% (166 of 851) in this cross-sectional cohort study. Small airway function parameters (FEF25-75%, FEF50%, FEF75%) showed strong correlations with FEV₁% (r = 0.670, 0.658, 0.609, p<0.001, respectively), FEV₁/FVC% (r = 0.812, 0.751, 0.871, p<0.001, respectively) and PEF% (r = 0.626, 0.635, 0.530, p<0.01, respectively). Moreover, small airway function parameters and large airway function parameters (FEV₁%, FEV₁/FVC%, PEF%) were curve-associated rather than linear-related (p<0.001). FEF25-75%, FEF50%, FEF75% and FEV₁% demonstrated a positive correlation with PC₂₀ (r = 0.282, 0.291, 0.251, 0.224, p<0.001, respectively). Interestingly, FEF25-75% and FEF50% exhibited a higher correlation coefficient with PC₂₀ than FEV₁% (0.282 vs. 0.224, p = 0.031 and 0.291 vs. 0.224, p = 0.014, respectively). ROC curve analysis for predicting moderate to severe AHR showed that the area under the curve (AUC) was 0.796, 0.783, 0.738, and 0.802 for FEF25-75%, FEF50%, FEF75%, and the combination of FEF25-75% and FEF75%, respectively. When Compared to children with normal lung function, patients with SAD were slightly older, more likely to have a family history of asthma and airflow obstruction with lower FEV₁% and FEV₁/FVC%, lower PEF% and more severe AHR with lower PC₂₀ ( all p<0.05).

CONCLUSION

Small airway dysfunction is highly correlated with large airway function impairment, severe airflow obstruction and AHR in preschool asthmatic children. Small airway function parameters should be utilized in the management of preschool asthma.

The potential role of plasma miR-4301 in PM2.5 exposure-associated lung function reduction

The effect of PM_2.5 exposure on lung function reduction has been well-documented, but the underlying mechanism remains unclear. MiR-4301 may be involved in regulating pathways related to lung injury/repairment, and this study aimed to explore the potential role of miR-4301 in PM_2.5 exposure-associated lung function reduction. A total of 167 Wuhan community nonsmokers were included in this study. Lung function was measured and personal PM_2.5 exposure moving averages were evaluated for each participant. Plasma miRNA was determined by real-time polymerase chain reaction. A generalized linear model was conducted to assess the relationships among personal PM_2.5 moving average concentrations, lung function, and plasma miRNA. The mediation effect of miRNA on the association of personal PM_2.5 exposure with lung function reduction was estimated. Finally, we performed pathway enrichment analysis to predict the underlying pathways of miRNA in lung function reduction from PM_2.5 exposure. We found that each 10 μg/m³ increase in the 7-day personal PM_2.5 moving average concentration (Lag0-7) was related to a 46.71 mL, 1.15%, 157.06 mL/s, and 188.13 mL/s reductions in FEV₁, FEV₁/FVC, PEF, and MMF, respectively. PM_2.5 exposure was negatively associated with plasma miR-4301 expression levels in a dose‒response manner. Additionally, each 1% increase in miR-4301 expression level was significantly associated with a 0.36 mL, 0.01%, 1.14 mL/s, and 1.28 mL/s increases in FEV₁, FEV₁/FVC, MMF, and PEF, respectively. Mediation analysis further revealed that decreased miR-4301 mediated 15.6% and 16.8% of PM_2.5 exposure-associated reductions in FEV₁/FVC and MMF, respectively. Pathway enrichment analyses suggested that the wingless related-integration site (Wnt) signaling pathway might be one of the pathways regulated by miR-4301 in the reduction of lung function from PM_2.5 exposure. In brief, personal PM_2.5 exposure was negatively associated with plasma miR-4301 or lung function in a dose‒response manner. Moreover, miR-4301 partially mediated the lung function reduction associated with PM_2.5 exposure.

Deep Learning Utilizing Suboptimal Spirometry Data to Improve Lung Function and Mortality Prediction in the UK Biobank

Background

Spirometry measures lung function by selecting the best of multiple efforts meeting pre-specified quality control (QC), and reporting two key metrics: forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC). We hypothesize that discarded submaximal and QC-failing data meaningfully contribute to the prediction of airflow obstruction and all-cause mortality.

Methods

We evaluated volume-time spirometry data from the UK Biobank. We identified "best" spirometry efforts as those passing QC with the maximum FVC. "Discarded" efforts were either submaximal or failed QC. To create a combined representation of lung function we implemented a contrastive learning approach, Spirogram-based Contrastive Learning Framework (Spiro-CLF), which utilized all recorded volume-time curves per participant and applied different transformations (e.g. flow-volume, flow-time). In a held-out 20% testing subset we applied the Spiro-CLF representation of a participant's overall lung function to 1) binary predictions of FEV1/FVC < 0.7 and FEV1 Percent Predicted (FEV1PP) < 80%, indicative of airflow obstruction, and 2) Cox regression for all-cause mortality.

Findings

We included 940,705 volume-time curves from 352,684 UK Biobank participants with 2-3 spirometry efforts per individual (66.7% with 3 efforts) and at least one QC-passing spirometry effort. Of all spirometry efforts, 24.1% failed QC and 37.5% were submaximal. Spiro-CLF prediction of FEV1/FVC < 0.7 utilizing discarded spirometry efforts had an Area under the Receiver Operating Characteristics (AUROC) of 0.981 (0.863 for FEV1PP prediction). Incorporating discarded spirometry efforts in all-cause mortality prediction was associated with a concordance index (c-index) of 0.654, which exceeded the c-indices from FEV1 (0.590), FVC (0.559), or FEV1/FVC (0.599) from each participant's single best effort.

Interpretation

A contrastive learning model using raw spirometry curves can accurately predict lung function using submaximal and QC-failing efforts. This model also has superior prediction of all-cause mortality compared to standard lung function measurements.

Funding

MHC is supported by NIH R01HL137927, R01HL135142, HL147148, and HL089856.BDH is supported by NIH K08HL136928, U01 HL089856, and an Alpha-1 Foundation Research Grant.DH is supported by NIH 2T32HL007427-41EKS is supported by NIH R01 HL152728, R01 HL147148, U01 HL089856, R01 HL133135, P01 HL132825, and P01 HL114501.PJC is supported by NIH R01HL124233 and R01HL147326.SPB is supported by NIH R01HL151421 and UH3HL155806.TY, FH, and CYM are employees of Google LLC.

Bronchodilator Response in FEF25-75 for the Diagnosis of Asthma in Children

BACKGROUND

Spirometry tests with a bronchodilator response (BDR) in FEV1, a methacholine concentration that produces a 20% drop in FEV1 (PC20) ≤ 2 mg/mL, and a positive exercise test have high specificity for the diagnosis of asthma in children. However, the value of forced expiratory flow during the middle half of the FVC maneuver (FEF25-75) in spirometry has been questioned. The objective of this study was to relate the BDR in FEF25-75 of spirometry tests with normal FEV1 and FEV1/FVC to airway hyper-responsiveness (AHR) to methacholine or exercise in children age 5-15 y with clinical suspicion of asthma.

METHODS

This was a cross-sectional study of spirometry tests performed between January 2017-December 2019 in children age 5-15 y with diagnostic suspicion of asthma who had a methacholine and/or exercise testing within a period not exceeding 60 d between exams.

RESULTS

The mean (± SD) age of the children was 9.04 ± 2.67 y, with a range of 5-15 y, and 56.17% were male. Of the 324 spirometry tests with normal FEV1 and FEV1/FVC, 66 (20.4%) tests showed BDR in FEF25-75. A total of 46.9% and 33.3% of the children with and without BDR in FEF25-75, respectively, had a PC20 value ≤ 2 mg/mL and/or a positive exercise testing (P = .039).

CONCLUSIONS

Children with suspected asthma and normal spirometry, other than BDR in FEF25-75, had greater AHR than those without BDR in FEF25-75. BDR in FEF25-75 was not always accompanied by AHR to confirm the diagnosis of asthma, so this study suggests that assessment of FEF25-75 alone is not always reliable for ruling in or ruling out AHR in the setting of otherwise normal spirometry results in children with suspected asthma.

Small airway disease and asthma control

AIM

Maximum mid-expiratory flow (MMEF) is one of the pulmonary function tests that report small airway disease. Our study aimed to investigate the role of MMEF values in asthma control, the prevalence of small airway disease, and their effect on asthma control in patients with asthma with normal forced expiratory volume in one second (FEV₁) values.

MATERIAL AND METHOD

Patients who presented to the Chest Diseases outpatient clinic of our hospital between 2018 and 2019 and were diagnosed as having asthma were included in the study. The characteristics of the patients, pulmonary function tests, their asthma treatment, and asthma control test (ACT) scores were recorded. Patients with FEV₁ <80 in the pulmonary function test, those with additional lung disease, those who had an attack in the last 4 weeks, and patients who smoked were excluded from the study. MMEF <65 was defined as small airway disease.

RESULTS

The MMEF% and MMEF (L/s) values of the group with uncontrolled asthma were found to be statistically significantly lower than those of the controlled asthma group (p = 0.016 and p = 0.003, respectively). MMEF% and MMEF (L/s) values in those with wheezing were found to be significantly lower compared with those without wheezing (p = 0.025 and p = 0.049, respectively). The MMEF% and MMEF (L/s) values of the patients with nocturnal symptoms were found to be statistically significantly lower than in patients without nocturnal symptoms (p = 0.023 and p = 0.041, respectively). ACT values of patients with MMEF <65 were found to be statistically lower than those of patients with MMEF >65 (0.047).

CONCLUSION

Considering small airway disease in patients with asthma may be beneficial in clinical practice.

Sensitivity of FEV1 and Clinical Parameters in Children With a Suspected Asthma Diagnosis

BACKGROUND

Asthma is the most common chronic disease in children and a robust diagnosis is crucial to optimize patient care and reduce its burden. To diagnose asthma in children, the Global Initiative for Asthma (GINA) recommendations propose a 12% improvement in forced expiratory volume in 1 second (FEV₁) after a bronchodilation test. Nevertheless, such a criterion is rarely confirmed in these patients in clinical practice.

OBJECTIVE

The objective of this study was to evaluate the sensitivity of spirometric and clinical parameters in identifying children with possible asthma.

METHODS

The VERI-VEMS Study is a multicenter international retrospective cohort study. Data were collected, from January 2008 until January 2019, for all consecutive children (aged 5-18 years), with a diagnosis of asthma, who performed a spirometry at the time of the diagnosis. We compared the sensitivity of the reversibility criterion proposed by GINA guidelines, with other spirometric and clinical variables, using physician-diagnosed asthma and response to treatment as the standard.

RESULTS

The study included 871 children. The reversibility criterion of 12% of FEV₁ showed a sensitivity of 30.4%. The 3 best spirometric or clinical criteria were the presence of dry cough, or wheezing or atopy and dry cough, or wheezing or exercise-induced dyspnea, with a sensitivity reaching 99.5%, with no added value of the spirometric parameters in the calculation of the cumulated sensitivity for the diagnosis of pediatric asthma.

CONCLUSIONS

Postbronchodilator reversibility of 12%, although essential for patients' follow-up, has an insufficient low sensitivity in reaching a diagnosis of asthma in pediatric patients, compared with a combination of clinical symptoms, that show a better sensitivity. Further studies on specificity will help clarify the role of this change in the diagnostic paradigm in formally diagnosing children with asthma.

The predictive value of pulmonary function test before transplantation for chronic pulmonary graft-versus-host-disease after allogeneic hematopoietic stem cell transplantation

BACKGROUND

Pulmonary chronic graft-versus-host disease (cGVHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a devastating complication and often diagnosed at a late stage when lung dysfunction is irreversible. Identifying patients before transplant who are at risk may offer improved strategies to decrease the mortality. Bronchiolitis obliterans syndrome (BOS) is the typical manifestation of pulmonary cGVHD, which is clinically diagnosed by pulmonary function test (PFT). This study aimed to evaluate the predictive value of PFT pre-HSCT for BOS.

METHODS

A single center cohort of 923 allo-HSCT recipients was analyzed, including 15 patients who developed pulmonary cGVHD. Kaplan-Meier method was used to analyze the 3 year progression free survival and 3 year overall survival (OS). A Cox regression model was applied for univariate and multivariate models.

RESULTS

The 3 year cumulative incidence of pulmonary cGVHD was 2.04% (95% CI 1.00-3.08%). According to the cut-off values determined by receiver operator characteristic curve, higher ratio of forced expiratory volume during one second to forced vital capacity (FEV1/FVC) pre-HSCT was correlated to a lower incidence of pulmonary cGVHD [0.91% (95% CI 0.01-1.81%) vs. 3.61% (95% CI 1.30-5.92%), P < 0.01], and so as peak expiratory flow to predictive value (PEF/pred) [0.72% (95% CI 0-1.54%) vs. 3.74% (95% CI 1.47-6.01%), P < 0.01]. Multivariate analysis showed that FEV1/FVC (HR = 3.383, P = 0.047) and PEF/pred (HR = 4.426, P = 0.027) were independent risk factors for onset of BOS. Higher FEV1/FVC and PEF/pred level were related to a significantly decreased 3 year non-relapse mortality. The 3 year OS was superior in patients with higher PEF/pred [78.17% (95% CI 74.50-81.84%) vs. 71.14% (95% CI 66.08-76.20%), P = 0.01], while FEV1/FVC did not show significance difference.

CONCLUSION

Our results suggested that PFT parameters such as PEF/pred and FEV1/FVC could be predictors for pulmonary cGVHD and even transplant outcomes before HSCT.

Pulmonary Function Tests in Childhood Asthma: Which indices are Better for Assessment of Severity?

OBJECTIVE

To study pulmonary function tests in childhood asthma and to determine which indices are better for assessment of severity.

METHODS

This was a hospital-based, cross-sectional study. All consecutive children aged between 5 and 15 y with mild and severe persistent asthma were enrolled. Children in whom diagnosis of asthma was doubtful and those with chronic lung disease or suppurative lung disease were excluded. Diagnosis and classification was based on GINA guidelines. Age-/sex-matched controls who did not have history of wheezing any time in the past were selected. Detailed spirometry was performed on all children enrolled using RMS HELIOS 401.

RESULTS

A total of 144 children were enrolled in the study (48 children in each group, i.e., control, mild and severe). Mean age of the study population was 9.06 ± 2.604 y with M:F ratio of 1.9:1. Mean percent of predicted values of FEV1, FVC, FEV1/FVC, FEF_25-75, and PEFR in the control group was 94.83, 92.63, 103.25, 73.90, and 93.60; in the mild group was 90.58, 83.52, 111.10, 76.50, and 92.00; and in the severe group 57.56, 62.83, 92.85, 40.15, and 62.12, respectively. Values of all the indices decreased with increase in severity. FEV1 (95% CI: 0.884 to 0.971) having the highest correlation coefficient (-0.652) with respect to severity of asthma and FEV1/FVC having the least (-0.202). FEF_25-75 (95% CI: 0.652 to 0.803) having a higher area under the curve, was a better spirometric parameter in predicting mild asthma.

CONCLUSION

FEV1 was better index for assessing severity of asthma and FEF_25-75 better in predicting mild asthma.

Lung Function Tests, Quality of Life and Telemedicine: Three Windows on the Multifaceted World of Asthma in Adolescents

Asthma is a heterogeneous disease usually characterized by chronic airway inflammation and recognized as the most prevalent chronic illness among children. Despite this, the knowledge as to how asthma affects adolescents is still scarce. One of the main management problems of asthmatic adolescents is the poor adherence to pharmacological and non-pharmacological treatments. The assessment of respiratory function and the impact on quality of life are still two crucial challenges in the management of asthmatic adolescents. Additionally, the COVID-19 pandemic has prompted physicians to explore complementary management strategies including telemedicine technologies. This review aims to provide an update on the contribution of respiratory functional tests, how asthma affects quality of life of adolescents and, finally, how telemedicine contributes to the management of adolescent asthmatics during the COVID-19 pandemic.

MMEF25-75 may predict significant BDR and future risk of exacerbations in asthmatic children with normal baseline FEV1

(1) Background: Several recent studies on the clinical value of spirometry indexes demonstrated high sensitivity of FEF25-75 as a marker of bronchial obstruction in asthmatics with normal baseline spirometry. Our study aims to evaluate the clinical value of maximal mid-expiratory flow in children with asthma. (2) Methods: For two years, 257 children were included - 211 with asthma and 46 healthy controls. Pre- and post-bronchodilator spirometry, atopic status determination and asthma control assessment were performed. (3) Results: The small airway obstruction (SAO) group (FEV1≥80%, ММEF25/75<65%) demonstrated significantly lower values for FEV1, FEV1/FVC, PEFR, МMMF25/75 and a significant higher bronchodilator response (BDR, ΔFEV1% init. ≥12%) compared to normal baseline spirometry group (FEV1>80%, MMEF25/75≥65%) (Р<0.0001). In addition, we found a statistically significant difference in FEF25-75/FVC median between asthmatics and healthy controls (Р<0.0001) regardless of the FEV1 value. Children with SAO have a 2.338-fold higher risk of poor asthma outcome (OR 95% CI [1.077-5.294]) and a 6.171-fold (OR 95% CI [2.523-15.096]) greater probability of demonstrating positive BDR, compared to children with normal baseline spirometry. MMEF25/75 was found to be a good predictor for positive BDR with AUC 0.843 (CI 0.781-0.845) and a best cut-off value of 58.1% (77.8% sensitivity and 78.8% specificity). (4) Conclusion: Our results confirmed that a small but substantial group of asthmatic children with normal baseline FEV1 and low MMEF25-75 are at higher risk for poor asthma outcomes.

Carbocysteine Modifies Circulating miR-21, IL-8, sRAGE, and fAGEs Levels in Mild Acute Exacerbated COPD Patients: A Pilot Study

Patients with Chronic Obstructive Pulmonary Disease (COPD) periodically experience acute exacerbation (AECOPD). Carbocysteine represents a valid add on therapy in COPD by exerting antioxidant and anti-inflammatory activities. The in vivo effects of carbocysteine on inflammatory markers are not yet fully understood. The aims of this study were to assess: (i) miR-21, IL-8, soluble Receptor for Advanced Glycation End Products (sRAGE), and fluorescent Advanced Glycation End Products (fAGEs) in control subjects (n = 9), stable (n = 9), and AECOPD patients (n = 24); and (ii) whether carbocysteine modifies these markers and the functional parameters in mild AECOPD patients. Mild AECOPD patients received or not carbocysteine along with background inhalation therapy for 20 days. At the onset and at the end of the observation period, the following parameters were evaluated: FEV1, FEF25–75%, CAT questionnaire; miR-21 by Real Time PCR; IL-8 and sRAGE by ELISA; and fAGEs by spectro-fluorescence method. COPD patients showed higher levels of miR-21, IL-8, fAGEs and lower levels of sRAGE compared to that of controls. miR-21 inversely correlated with FEV1. IL-8 and fAGEs were significantly different in stable and exacerbated COPD patients. Carbocysteine improved symptoms, FEV1 and FEF25–75%, increased sRAGE, and reduced miR-21, IL-8, and fAGEs in mild AECOPD patients. The present study provides compelling evidence that carbocysteine may help to manage mild AECOPD by downregulating some parameters of systemic inflammation.

Role of FEF25-75 in managing children with newly-diagnosed asthma in clinical practice

Background Reversible bronchial obstruction characterizes asthma. Spirometry is the gold standard to assess airflow, and FEV1 is the most reliable parameter in this regard. However, many children with asthma have FEV1 within the normal range despite uncontrolled asthma and worsening. Therefore, FEF25-75 has been proposed as a valuable marker of early airflow impairment. This study aimed at investigating FEF25-75 in a cohort of children with newly diagnosed asthma. Methods 381 children (122 females, mean age 11.6 years) were consecutively visited and had a new asthma diagnosis. In addition, Spirometry, type-2 phenotyping, asthma control assessment, and ACT were performed. Results 72 (18.9%) asthmatic children had impaired FEF25-75, such as <65% of predicted. Low FEF25-75 was associated with lower FVC and FEV1/FVC values (OR 1.11 and 1.32, respectively). Children with normal FEV1 but impaired FEF25-75 had more frequently uncontrolled asthma (15.8% vs. 32.4%) than children with both parameters within the normal range. Conclusions FEF25-75 deserves adequate and careful consideration in children with asthma, and the presence of impaired FEF25-75 values suggests a more compelling approach.

Short-term effects of real-time individual fine particulate matter exposure on lung function: a panel study in Zhuhai, China

Fine particulate matter (PM_2.5) is still the primary air pollutant in most Chinese cities and its adverse effects on lung function have been widely reported. However, short-term effects of individual exposure to PM_2.5 on pulmonary expiration flow indices remain largely unknown. In this study, we examined the short-term effects of real-time individual exposure to PM_2.5 on lung function in a panel of 115 healthy adults. We measured individual real-time PM_2.5 exposure and lung function. Environmental PM_2.5 concentrations in the same period were collected from the nearest monitoring station. Generalized linear model was used to assess the effects of individual PM_2.5 exposure on lung function after adjusting for potential confounders. Individual PM_2.5 exposure ranged from 18.5 to 42.4 μg/m³ with fluctuations over time and ambient PM_2.5 concentrations presented a moderate trend of fluctuation at the same day. Except forced expiratory volume in 1 s (FEV₁) decline related to 2-h moving average PM_2.5 exposure, no significant associations between individual PM_2.5 exposure and other volume indices including forced vital capacity (FVC) and FEV₁/FVC ratio were observed. The adverse effects of individual PM_2.5 exposure on pulmonary expiration flow indices including peak expiratory flow (PEF), maximal mid-expiratory flow (MMF) and forced expiratory flow at 50%, and 75% of vital capacity (FEF_50% and FEF_75%) were observed to be strongest at 2 moving average hours and could last for 24 h. Stratified analysis showed greater and longer effects among participants who were aged over 40 years, males, or smokers. These findings suggested that individual PM_2.5 exposure was significantly associated with altered lung function, especially with pulmonary expiration flow indices decline, which was strongest at 2 moving average hours and could last for 24 h.

Small-airway disease and its reversibility in human immunodeficiency virus-infected children on highly active antiretroviral therapy: A cross-sectional study in an African setting

BACKGROUND:

Lung function abnormalities may occur in children with human immunodeficiency virus (HIV) infection. Small-airway disease (SAD) precedes abnormalities in forced expiratory volume in 1 s (FEV ₁).

OBJECTIVE:

This study aims to assess the presence and reversibility of SAD in HIV-infected children using the Global Lung Function Initiative standards.

METHODS:

A cross-sectional study was conducted over 6 months at the Paediatric HIV Clinic of the University of Nigeria Teaching Hospital in Enugu, Southeast Nigeria. Eligible consenting children with HIV infection were recruited. Lung function was measured, and the reversibility of FEV₁ and forced vital capacity (FVC) was assessed at 12% while that of forced expiratory flow between 25% and 75% (FEF_25-75) was assessed at 12%, 15%, and 20%. Predictors of abnormal Z-score values were determined by multivariate linear and logistic regressions. Statistically significant values were set at P < 0.05.

RESULTS:

The mean Z-score for FEV₁, FVC, and FEF_25-75 was − 2.19, −1.86, and − 1.60, respectively. Most patients (73%) had abnormal FEV₁, while 52% had abnormal FEF_25-75. Significant changes in FEV₁ (P = 0.001) and FEF_25-75 (P < 0.001) occurred after the bronchodilator response (BDR) test. Of the children whose FEV₁ showed positive BDR, 70.9% had low zFEV_1; 50% had low zFEF_25-75, while all had low FEV_1. Nutritional status (Z-score for body mass index) was significantly associated with low FEV_1.

CONCLUSIONS:

Abnormal FEF_25-75 as a marker of SAD and FEV₁ with a positive BDR are common in HIV-infected children. These lung function abnormalities justify long-term follow-up for these patients.

"Reactance inversion" at low frequencies during lung function measurement by impulse oscillometry in children with persistent asthma. J Asthma 2021;59:1597-1603. [PMID: 34255601 DOI: 10.1080/02770903.2021.1955376]

BACKGROUND

Small airway dysfunction (SAD) in asthma can be measured by impulse oscillometry (IOS). Usually, the reactance should decrease with decreases in frequency oscillation. Sometimes an upward shift of the curve at low frequencies can be observed together with lower than expected reactance values. The actual value of the reactance at 5 Hz (X5) is calculated by the Sentry Suite application of the Jaeger Master screen iOS system™, providing the corrected X5 parameter (CX5). Our hypothesis is that correction of X5 is common in persistent asthma and it correlates better than X5 with the IOS parameters for evaluating SAD.

METHODS

In this transversal study, we evaluated 507 children (3-18 years old) using IOS-spirometry (Sentry Suite, Vyntus®). Resistance of all airways (R5), reactance area (AX), resonant frequency (Fres), X5, CX5, difference between R5 and R20 (D5-20), and spirometry parameters were analyzed. Reactance inversion and CX5 prevalence by age range was determined. The mean IOS-Spyrometry values in children with and without CX5 were compared, and correlations with each IOS-spirometry parameter in the age groups were performed.

RESULTS

CX5 was found in 83.5% of preschool children, 66.2% of schoolchildren, and 43.3% of adolescents (p < 0.001). The means of R5, AX, and D5-20 were significantly higher and FEV1 was significantly lower in children with CX5 (p < 0.05). In all ages, CX5 correlated better than X5 with IOS-spirometry parameters.

CONCLUSION

Reactance inversion and CX5 are frequent in asthmatic children, decrease with age, and correlate more closely than X5 with other IOS-spirometry parameters for evaluating SAD.

Assessment of Metal Concentrations and Associations with Pulmonary Function among Children with Asthma in Chicago, Illinois

Individuals living in areas with the potential for elevated metal exposure from industrial sources may have reduced pulmonary function. We evaluated cross-sectional associations of toenail concentrations of 17 metals within a community area of residence and asthma control in 75 children, and pulmonary function measures [forced expiratory volume in one second (FEV1; liters), forced vital capacity (FVC; liters), FEV1 to FVC ratio (FEV1:FVC), and mid-exhalation forced expiratory flow rate (FEF 25-75%; liters/second)], in a subsample of 39 children with diagnosed asthma in Chicago, Illinois. Linear regression models were used to estimate adjusted regression coefficients and standard errors (SE) for the associations between ≥ median versus Collapse

Key Words

• asthma
• children
• metals
• pulmonary function
• respiratory function

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MESH Headings

• Asthma/epidemiology
• Chicago/epidemiology
• Child
• Cross-Sectional Studies
• Forced Expiratory Volume
• Humans
• Lung
• Vital Capacity

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Grants

• T42 OH008672 NIOSH CDC HHS
• P42 ES007373 NIEHS NIH HHS
• P30 CA023108 NCI NIH HHS
• R01 ES02442304 NIEHS NIH HHS
• P30 ES027792 NIEHS NIH HHS

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Affiliation(s)

Jessica M. Madrigal Division of Epidemiology and Biostatistics, School of Public Health, University of Illinois Chicago, Chicago, IL 60612, USA; (J.M.M.); (V.P.)
Victoria Persky Division of Epidemiology and Biostatistics, School of Public Health, University of Illinois Chicago, Chicago, IL 60612, USA; (J.M.M.); (V.P.)
Brian P. Jackson Department of Earth Sciences, Dartmouth College, Hanover, NH 03755, USA;
Amy Bain Mobile Care Chicago, Chicago, IL 60609, USA; (A.B.); (M.S.)
Matt Siemer Mobile Care Chicago, Chicago, IL 60609, USA; (A.B.); (M.S.)
Andrea A. Pappalardo Department of Pediatrics, College of Medicine, University of Illinois Chicago, Chicago, IL 60612, USA; Department of Medicine, College of Medicine, University of Illinois Chicago, Chicago, IL 60612, USA
Maria Argos Division of Epidemiology and Biostatistics, School of Public Health, University of Illinois Chicago, Chicago, IL 60612, USA; (J.M.M.); (V.P.)

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Impact of Payor-Initiated Switching of Inhaled Corticosteroids on Lung Function

OBJECTIVES

To evaluate the impact of a payor-initiated formulary change in inhaled corticosteroid coverage on lung function in patients with asthma and on provider prescribing practices. This formulary change, undertaken in August 2016 by a Medicaid payor in Kentucky, eliminated coverage of beclomethasone dipropionate, a metered dose inhaler (MDI), in favor of mometasone furoate, available as MDI and dry powder inhaler (DPI).

STUDY DESIGN

A retrospective chart review was conducted on children with asthma ages 6-18 years covered by the relevant payor from a university-based pediatric practice who were seen before the formulary change (February to July 2016) and after (February to July 2017). Spirometry data from each visit was compared using the paired Student t test.

RESULTS

Fifty-eight patients were identified who were initially on beclomethasone dipropionate and had spirometry available at both visits. Those who switched from an MDI to a DPI (n = 24) saw a decline in median predicted forced expiratory volume in 1 second from 98.5% to 91% (P = .013). A decline was also seen in forced expiratory flow at 25%-75%, from 89.5% predicted to 76% predicted (P = .041). No significant changes were observed in children remaining on an MDI. Seven patients discontinued inhaled corticosteroid therapy.

CONCLUSIONS

This study suggests insurance formulary changes leading to use of a different inhaler device may have a detrimental impact on pediatric lung function, which may be a surrogate measure for overall asthma control. This could be due to a lack of adequate timely educational intervention as well as the inability of some children to use DPIs.

A compendium and review of pediatric pulmonary function testing assessment opportunities for asthma

OBJECTIVE

Standard spirograms are widely used in the respiratory disease management community to help diagnosis asthma and provide longitudinal information. Surprisingly, basic information obtained on the spirogram, beyond the FEV₁ and change in FEV₁ after bronchodilator is underutilized. We reviewed information on pulmonary function and bronchodilator response in children since 2016. We present here a discussion of other element of the standard spirogram that can be used for pediatric asthma management.Methods: Medline search of pulmonary function, children, adolescents, bronchodilator reversibility, small airway disease, small airway function, asthma, airflow limitation, bronchodilator response. Studies since 2016 that provide information on normal or asthmatic children bronchodilator response, and/or small airway or pulmonary function values after albuterol.

RESULTS

Limited data has been published on FEV₁ bronchodilator response in children since 2016. Other parameters of the pulmonary function test in children have had recent documentation.

CONCLUSIONS

New data on FEV₁ bronchodilator response in normal children is limited since 2016. However, other details of pulmonary function interpretation in asthmatic children has had considerable attention, and are reviewed here.

FEF25-75% Is a More Sensitive Measure Reflecting Airway Dysfunction in Patients with Asthma: A Comparison Study Using FEF25-75% and FEV1

BACKGROUND

Reduced forced expiratory flow between 25% and 75% of vital capacity percent predicted (FEF_25-75%) representing small airway dysfunction (SAD) was associated with asthma development and progression.

OBJECTIVE

To investigate whether FEF_25-75% was superior to forced expiratory volume in 1 second in predicted (FEV₁%) in reflecting asthma features in adult patients.

METHODS

A retrospective spirometry dataset comprising 1801 adult patients with confirmed asthma and a subgroup of 332 patients having detailed clinical data were used to explore the association of FEF_25-75% and/or FEV₁% with clinical features of asthma.

RESULTS

Of the 1801 subjects, FEV₁% and FEF_25-75% ranged from 136.8% to 10.2% and 127.3% to 3.1%, respectively. FEF_25-75% < 65% was present in 1,478 (82.07%) of patients. FEF_25-75% was strongly correlated with matched FEV₁% (r = 0.900, P < .001). FEF_25-75% and FEV₁% were both correlated with airway hyperresponsiveness (r = 0.436, P < .001; r = 0.367, P < .001), asthma control test score (r = 0.329, P < .001; r = 0.335, P < .001), and sputum eosinophil count (r = -0.306, P < .001; r = -0.307, P < .001). Receiver-operating characteristic curves showed that FEF_25-75% had greater value in predicting severe asthma (area under the curve: 0.84 vs 0.81, P = .018), airflow obstruction (0.97 vs 0.89, P < .001), and severe bronchial hyperresponsiveness (0.74 vs 0.69, P = .012) as compared with FEV₁%. Patients with SAD (FEF_25-75% < 65%) in the presence of normal FEV₁% exhibited higher sputum eosinophil counts and had an increased dosage of daily inhaled corticosteroids (P < .001 and P = .010) than patients with normal lung function and their FEF_25-75% values correlated with sputum eosinophil count (r = -0.419, P = .015), but not FEV₁%.

CONCLUSION

FEF_25-75% represented small airway function and was more sensitive at reflecting airway hyperresponsiveness, inflammation, and disease severity as compared with FEV₁% in patients with asthma. Our data suggest further assessment of FEF_25-75% in asthma management, particularly for those with SAD who present normal FEV₁%.

Dysanapsis in men and women with obesity

Obesity alters chest wall mechanics, reduces lung volumes, and increases airway resistance. In addition, the luminal area of the larger conducting airways is smaller in women than in men when matched for lung size. We examined whether differences in pulmonary mechanics with obesity and sex were associated with the dysanapsis ratio (DR), an estimate of airway size when the expiratory flow is maximal, in men and women with and without obesity. In addition, we examined the ability to estimate DR using predicted versus measured static recoil pressure at 50% forced vital capacity (FVC; Pst_50FVC). Participants completed pulmonary function testing and measurements of pulmonary mechanics. Flow, volume, and transpulmonary pressure were recorded while completing forced vital capacity (FVC) maneuvers in a body plethysmograph. Static compliance curves were collected using the occlusion technique. DR was calculated using measured values of forced midexpiratory flow and Pst_50FVC. DR was also calculated using Pst predicted from previously reported data. There was no significant group (lean vs. obese) by sex interaction or main effect of group on DR. However, women displayed significantly larger DR compared with men. Predicted Pst_50FVC was significantly greater than measured Pst_50FVC. DR calculated from measured Pst was significantly greater than when using predicted Pst. In conclusion, although obesity does not appear to alter airway size, women may have larger airways compared with men when midexpiratory flow is maximal. In addition, DR estimated using predicted Pst should be used with caution.NEW & NOTEWORTHY It is unclear whether obesity in combination with sex influences the dysanapsis ratio (DR). These data indicate that DR is unaltered in adults with obesity and is greater in women than in men but similar between sexes when matched for lung volume. We also report a significant difference between predicted and measured static recoil pressure. Thus, we caution against predicting static recoil pressure in the calculation of DR.

129Xe MRI as a measure of clinical disease severity for pediatric asthma

BACKGROUND

Measurement of regional lung ventilation with hyperpolarized ¹²⁹Xe magnetic resonance imaging (¹²⁹Xe MRI) in pediatric asthma is poised to advance our understanding of disease mechanisms and pathophysiology in a disorder with diverse clinical phenotypes. ¹²⁹Xe MRI has not been investigated in a pediatric asthma cohort.

OBJECTIVE

We hypothesized that ¹²⁹Xe MRI is feasible and can demonstrate ventilation defects that relate to and predict clinical severity in a pediatric asthma cohort.

METHODS

Thirty-seven children (13 with severe asthma, 8 with mild/moderate asthma, 16 age-matched healthy controls) aged 6 to 17 years old were imaged with ¹²⁹Xe MRI. Ventilation defect percentage (VDP) and image reader score were calculated and compared with clinical measures at baseline and at follow-up.

RESULTS

Children with asthma had higher VDP (P = .002) and number of defects per image slice (defects/slice) (P = .0001) than children without asthma. Children with clinically severe asthma had significantly higher VDP and number of defects/slice than healthy controls. Children with asthma who had a higher number of defects/slice had a higher rate of health care utilization (r = 0.48; P = .03) and oral corticosteroid use (r = 0.43; P = .05) at baseline. Receiver-operating characteristic analysis demonstrated that the VDP and number of defects/slice were predictive of increased health care utilization, asthma, and severe asthma. VDP correlated with FEV₁ (r = -0.35; P = .04) and FEV₁/forced vital capacity ratio (r = -0.41; P = .01).

CONCLUSIONS

¹²⁹Xe MRI correlates with asthma severity, health care utilization, and oral corticosteroid use. Because delineation of clinical severity is often difficult in children, ¹²⁹Xe MRI may be an important biomarker for severity, with potential to identify children at higher risk for exacerbations and improve outcomes.

Small Airway Dysfunction Links Asthma Severity with Physical Activity and Symptom Control

BACKGROUND

Little is known about the role of small airway dysfunction (SAD) and its complex relation with asthma control and physical activity (PA).

OBJECTIVE

To investigate the interrelations among SAD, risk factors for asthma severity, symptom control, and PA.

METHODS

We assessed SAD by impulse oscillometry and other sophisticated lung function measures including inert gas washout in adults with asthma (mild to moderate, n = 140; severe, n = 128) and 69 healthy controls from the All Age Asthma Cohort. We evaluated SAD prevalence and its interrelation with risk factors for asthma severity (older age, obesity, and smoking), type 2 inflammation (sputum and blood eosinophils, fractional exhaled nitric oxide), systemic inflammation (high-sensitivity C-reactive protein), asthma control (AC), and PA (accelerometer for 1 week). We applied a clinical model based on structural equation modeling that integrated causal pathways among these clinical variables.

RESULTS

The prevalence of SAD ranged from 75% to 90% in patients with severe asthma and from 53% to 64% in mild to moderate asthma. Severe SAD was associated with poor AC and low PA. Structural equation modeling indicated that age, obesity, obesity-related systemic inflammation, T2 inflammation, and smoking are independent predictors of SAD. Small airway dysfunction was the main determinant factor of AC, which in turn affected PA. Obesity affected AC directly and through its contribution to SAD and low PA. In addition, PA had bidirectional associations with obesity, SAD, and AC. Structural equation modeling also indicated interrelations among distal airflow limitation, air trapping, and ventilation heterogeneity.

CONCLUSIONS

Small airway dysfunction is a highly prevalent key feature of asthma that interrelates a spectrum of distal lung function abnormalities with risk factors for asthma severity, asthma control, and physical activity.

Small-airway dysfunction in paediatric asthma

PURPOSE OF REVIEW

Asthma is a chronic inflammatory airway disorder that can involve the entire bronchial tree. Increasing evidence shows that ventilation heterogeneity and small airway dysfunction are relevant factors in the pathogenesis of asthma and represent a hallmark in adults with persistent asthma. Little is known about the contribution of peripheral airway impairment in paediatric asthma, mainly due to the inaccessibility to evaluation by noninvasive techniques, which have only been widely available in recent years.

RECENT FINDINGS

Emerging evidence suggests that small airways are affected from the early stages of the disease in childhood-onset asthma. Conventional lung function measurement, using spirometry, is unable to sensitively evaluate small airway function and may become abnormal only once there is a significant burden of disease. Recent studies suggest that chronic inflammation and dysfunction in the small airways, as detected with new advanced techniques, are risk factors for asthma persistence, asthma severity, worse asthma control and loss of pulmonary function with age, both in adults and children. Knowing the extent of central and peripheral airway involvement is clinically relevant to achieve asthma control, reduce bronchial hyper-responsiveness and monitor response to asthma treatment.

SUMMARY

This review outlines the recent evidence on the role of small airway dysfunction in paediatric asthma development and control, and addresses how the use of new diagnostic techniques available in outpatient clinical settings, namely impulse oscillometry and multiple breath washout, could help in the early detection of small airway impairment in children with preschool wheezing and school-age asthma and potentially guide asthma treatment.

The Relationship Between Indicators of Nasal Respiratory Function and Spirometric Parameters in Children With Bronchial Asthma

Introduction: The relationship between objective indicators of nasal obstruction and airflow limitation in children with bronchial asthma (BA) and allergic rhinitis (AR) has not yet been studied. Objective: To study the relationship between objective parameters of nasal obstruction and airflow limitation, determined using the methods of anterior active rhinomanometry (AARM) and spirometry in children with BA and AR. Materials and Methods: Eighty eight children and adolescents with BA and AR, boys-65.9% (58/88), were examined. The median age was 11.09 [10.42; 11.76] years. To determine airflow limitation, the following spirometric parameters were evaluated: forced vital capacity of the lungs (FVC), forced expiratory volume in 1 s (FEV1), the ratio of FEV1/FVC, and maximum expiratory flow at the point 25% of the flow-volume loop (MEF25). Data were recorded both in absolute values and in relative units (% pred). Nasal respiratory function was determined by AARM based on the total nasal airflow (TNAF) in absolute (Pa/cm3/s) and relative units (RTNAF, % pred). Results: In the general cohort and in boys but not in girls, a statistically significant direct correlation was found between TNAF (Pa/cm3/s) and absolute spirometry parameters of bronchial patency-all had p < 0.01. Also, RTNAF and relative MEF25 values (% pred) in the general cohort were R = 0.22, p = 0.04, and in boys, R = 0.28, p = 0.03. In girls, there was no statistically significant correlation between nasal respiratory function and spirometric parameters, all p > 0.05. Additional analysis of literature was conducted to ascertain that the identified gender differences were not occasional. Conclusion: The significant positive correlation of absolute values of AARM and spirometric parameters in children with BA and AR was established, which apparently reflects the physical development of children. Of all the relative indicators of spirometry, only MEF25 (% pred), which indirectly reflects the patency of small bronchi, had a distinct direct correlation with RTNAF. These patterns are clearly expressed in boys with BA. In girls with this disease, however, the relationship between nasal respiratory function and spirometric indicators seems to be more complex and requires further study.

Inhaled albuterol increases estimated ventilatory capacity in nonasthmatic children without and with obesity

Forced mid-expiratory flow (i.e., isoFEF_25-75) may increase with a short-acting β₂-agonist in nonasthmatic children without bronchodilator responsiveness. This could also increase estimated ventilatory capacity along mid-expiration (V̇Ecap_25-75), especially in vulnerable children with obesity who exhibit altered breathing mechanics. We estimated V̇Ecap_25-75 pre- and post-albuterol treatment in 8-12yo children without (n = 28) and with (n = 46) obesity. A two-way ANOVA was performed to determine effects of an inhaled bronchodilator (pre-post) and obesity (group) on isoFEF_25-75 and V̇Ecap_25-75. There was no group by bronchodilator interaction or main group effect on outcome variables. However, a significant main effect of the bronchodilator was detected in spirometry parameters, including a substantial increase in isoFEF_25-75 (17.1 ± 18.0 %) and only a slight (non-clinical) but significant increase in FEV₁ (2.4 ± 4.3 %). V̇Ecap_25-75 significantly increased with albuterol (+11.7 ± 10.6 L/min; +15.8 ± 13.9 %). These findings imply potentially important increases in ventilatory reserve with a bronchodilator in nonasthmatic children without and with obesity, which could potentially influence respiratory function at rest and during exercise.

Small Airway Disease in Pediatric Asthma: the Who, What, When, Where, Why, and How to Remediate. A Review and Commentary

Asthma affects all portions of the airways. Small airways, however, comprise a substantial component of the conducting lung air flow. In asthma, inflammatory processes can affect the whole respiratory tract, from central to peripheral/small airways. The emphasis in adult and pediatric respiratory disease clinics is to focus on large airway obstruction and reversibility. This information, although valuable, underemphasizes a large portion of the conduction airway of asthmatics. Standard descriptions of asthma management focus on a multiple medication approaches. We particularly focused on the management of asthma in the international guidelines for the Global Initiative for Asthma (GINA). Overall, however, minimal attention is placed on the small airway pool in asthma medical management. We took the opportunity to thoroughly review and present specific data from the adult asthma literature which supported the concept that small airway abnormalities may play a role in the pathogenesis and clinical expression of asthma. Based on the conclusions of the adult asthma literature, we here present a thorough review of the literature as it relates to small airway disease in children with asthma. We used, collectively, individual data sources of data to expand the information available from standard diagnostic techniques, especially spirometry, in the evaluation of small airway disease. As the pharmacological approaches to moderate to severe asthma are advancing rapidly into the realm of biologics, we sought to present potential pharmacological options for small airway dysfunction in pediatrics prior to biological modifier intervention.

Effects of STIP1 and GLCCI1 polymorphisms on the risk of childhood asthma and inhaled corticosteroid response in Chinese asthmatic children

Background

Asthma is a common chronic lung disease in children. We aimed to determine the associations between stress-induced phosphoprotein 1 (STIP1) and glucocorticoid-induced transcript 1 (GLCCI1) polymorphisms and susceptibility of childhood asthma and inhaled corticosteroid (ICS) response in children.

Methods

A total of 263 Chinese Han asthmatic children were recruited from the Xiangya Hospital, Central South University. Pulmonary function tests were performed before the treatment and 3 months after the treatment. One hundred fifty non-asthmatic children were recruited. Each participant’s DNA was extracted from the peripheral blood and Method of MassARRAY was used to genotype the single-nucleotide polymorphisms (SNPs).

Results

STIP1 rs2236647 wild-type homozygote (CC) was associated with increased asthma risk of children (OR = 1.858, 95% CI:1.205–2.864), but not associated with the ICS response. GLCCI1 rs37969, rs37972 and rs37973 polymorphisms were not associated with the risk of childhood asthma. However, rs37969 mutant genotypes (TT/GT) were significantly associated with less improvement in PD20 (p = 0.028). We also found significant associations between rs37969, rs37972 and rs37973 mutant genotypes and less improvement in maximal midexpiratory flow (MMEF) after ICS treatment for 3 months (p = 0.036, p = 0.010 and p = 0.003, respectively).

Conclusions

STIP1 rs2236647 was associated with asthma risk of children and GLCCI1 rs37969 mutant genotypes were associated with less improvement in airway hyper-responsiveness. GLCCI1 rs37969, rs37972 and rs37973 polymorphisms might be associated with pulmonary function in childhood asthma patients after ICS treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-020-01332-2.

Lung function in obese children and adolescents without respiratory disease: a systematic review

BACKGROUND

Obesity in children and adolescents is associated with increased morbidity and mortality due to multisystemic impairment, including deleterious changes in lung function, which are poorly understood.

OBJECTIVES

To perform a systematic review to assess lung function in children and adolescents affected by obesity and to verify the presence of pulmonary changes due to obesity in individuals without previous or current respiratory diseases.

METHODS

A systematic search was performed in the MEDLINE-PubMed (Medical Literature Analysis and Retrieval System Online), Embase (Excerpta Medica Database) and VHL (Virtual Health Library/Brazil) databases using the terms "Lung Function" and "Pediatric Obesity" and their corresponding synonyms in each database. A period of 10 years was considered, starting in February/2008. After the application of the filters, 33 articles were selected. Using the PICOS strategy, the following information was achieved: (Patient) children and adolescents; (Intervention/exposure) obesity; (Control) healthy children and adolescents; (Outcome) pulmonary function alterations; (Studies) randomized controlled trial, longitudinal studies (prospective and retrospective studies), cross-over studies and cross-sectional studies.

RESULTS

Articles from 18 countries were included. Spirometry was the most widely used tool to assess lung function. There was high variability in lung function values, with a trend towards reduced lung function markers (FEV1/FVC, FRC, ERV and RV) in obese children and adolescents.

CONCLUSION

Lung function, measured by several tools, shows numerous markers with contradictory alterations. Differences concerning the reported results of lung function do not allow us to reach a consensus on lung function changes in children and adolescents with obesity, highlighting the need for more publications on this topic with a standardized methodology.

Respiratory Function and Voice: The Role for Airflow Measures

OBJECTIVE

To clarify the relationship between voice and respiratory function, and to understand the role for airflow measures in the evaluation of voice patients.

METHODS

Literature searches of MEDLINE (Ovid) and Web of Science were performed on April 6, 2020, to include articles written in English that both discussed voice in relation to lower respiratory function and reported evaluation of airflow. Search strategies included the keywords voice, respiratory, airflow, and aerodynamic measures. Data were extracted from articles that met inclusion criteria.

RESULTS

Twenty studies were included for review. Fourteen (70%) studies evaluated at least 1 spirometric respiratory measure, including Forced Vital Capacity, Forced Expiratory Volume in 1 second, and Forced Expiratory Flow. Other measures assessed included mean flow rate, mean peak airflow, phonatory airflow, inspiratory airflow, expiratory airflow, and phonation quotient. Notably, four studies which included pulmonary function tests (PFTs) as part of voice evaluation discovered previously undiagnosed respiratory disease in their study populations.

CONCLUSION

This review confirms that respiratory function contributes significantly to voice and reveals that few studies have explored the role for airflow measures in clarifying this relationship. Including airflow measures such as PFTs in standard voice evaluation may allow recognition of underlying respiratory disease contributing to voice dysfunction. Further research is recommended to establish indications and diagnostic criteria for the use of PFTs in voice patients.

Pragmatic Markers in the Management of Asthma: A Real-World-Based Approach

Bronchial hyperreactivity, reversible airflow limitation and chronic airway inflammation characterize asthma pathophysiology. Personalized medicine, i.e., a tailored management approach, is appropriate for asthma management and is based on the identification of peculiar phenotypes and endotypes. Biomarkers are necessary for defining phenotypes and endotypes. Several biomarkers have been described in asthma, but most of them are experimental and/or not commonly available. The current paper will, therefore, present pragmatic biomarkers useful for asthma management that are available in daily clinical practice. In this regard, eosinophil assessment and serum allergen-specific IgE assay are the most reliable biomarkers. Lung function, mainly concerning forced expiratory flow at 25-755 of vital capacity (FEF_25-75), and nasal cytology may be envisaged as ancillary biomarkers in asthma management. In conclusion, biomarkers have clinical relevance in asthma concerning both the endotype definition and the personalization of the therapy.

Forced Expiratory Flow (FEF25-75%) as a Clinical Endpoint in Children and Adolescents with Symptomatic Asthma Receiving Tiotropium: A Post Hoc Analysis

Introduction

In pediatric patients with asthma, measurements of forced expiratory volume in 1 s (FEV₁) may be normal or may not correlate with symptom severity. Forced expiratory flow at 25–75% of the vital capacity (FEF_25–75%) is a potentially more sensitive parameter for assessing peripheral airway function. This post hoc analysis compared FEF_25–75% with FEV₁ as an endpoint to assess bronchodilator responsiveness in children with asthma.

Methods

Change from baseline in trough FEF_25–75% and trough FEV₁ following treatment with either tiotropium (5 µg or 2.5 µg) or placebo Respimat^® was analyzed in four phase III trials in children (aged 6–11 years) and adolescents (aged 12–17 years) with symptomatic moderate (VivaTinA-asthma^® and PensieTinA-asthma^®) and mild (CanoTinA-asthma^® and RubaTinA-asthma^®) asthma. Data from all treatment arms were pooled and correlations between FEF_25–75% and FEV₁ were calculated and analyzed.

Results

A total of 1590 patients were included in the analysis. Tiotropium Respimat^® consistently improved FEF_25–75% and FEV₁ versus placebo, although in adolescents with severe asthma, the observed improvements were not statistically significant. Improvements in FEF_25–75% response with tiotropium versus placebo were largely more pronounced than improvements in FEV₁. Statistical assessment of the correlation of FEV₁ and FEF_25–75% showed moderate-to-high correlations (Pearson’s correlation coefficients 0.73–0.80).

Conclusions

In pediatric patients, FEF_25–75% may be a more sensitive measure to detect treatment response, certainly to tiotropium, than FEV₁ and should be evaluated as an additional lung function measurement.

Electronic Supplementary Material

The online version of this article (10.1007/s41030-020-00117-6) contains supplementary material, which is available to authorized users.

Small airways in children with allergic rhinoconjunctivitis: the potential role of a multicomponent nutraceutical

Allergic rhinitis and asthma are closely linked. A progression from rhinitis to overt asthma is common. FEF_25-75 is a spirometry parameter that could reflect small airways patency and could reliably predict early bronchial involvement in allergic rhinitis patients. MEF₅₀ very strongly correlates with FEF_25-75. The aim of this study was to evaluate possible spirometry change in two groups of children suffering from AR over time. The first group took a course of a nutraceutical (Lertal®) before the observation (active group, AG); a second one was considered as control (control group, CG). The children were visited at baseline, at the end of the nutraceutical course, and after 1 year. FEV₁, FVC, and MEF₅₀ were the primary outcomes. After one year, children in AG had significantly higher MEF₅₀ than CG children (p=0.009). In conclusion, the present study showed that a course with a multicomponent nutraceutical could prevent the MEF₅₀ decline in children with allergic rhinoconjunctivitis. (www.actabiomedica.it)

Correlation between fractional exhaled nitric oxide and Asthma Control Test score and spirometry parameters in on-treatment-asthmatics in Ho Chi Minh City

Background

Although fractional exhaled nitric oxide (FeNO) is a reliable and easily applied marker of airway inflammation in asthma, the relationship between FeNO and indicators of asthma control [Asthma Control Test (ACT) score] and/or severity (spirometry parameters) remains unclear. This study aims to determine possible correlations between FeNO and ACT score; and between FeNO and spirometry parameters.

Methods

A cross-sectional study with convenience sampling was conducted among ambulatory patients in the Asthma & COPD clinic at the University Medical Center, Ho Chi Minh City from March 2016 to March 2017. Using measurement of FeNO, the ACT questionnaire and a spirometry test, correlations were determined between FeNO and the ACT score and spirometry parameters.

Results

Four hundred and ten asthmatic patients (mean age 42 years; 65% female) were included and analyzed; their mean time since onset of asthma was 9.5 years. All patients were treated following step 2 to 4 of GINA guidelines. Mean (SD) FeNO was 29.5 (24.4) parts per billion (ppb) and mean (SD) ACT score was 20.5 (40). A significant difference in FeNO values was found among the three groups with different asthma control levels categorized according to the ACT score (P=0.001) but was not found among the three groups with different asthma treatment levels (P=0.425). FeNO was significantly inversely correlated with the ACT score (Spearman’s r =−0.224, P<0.001) and with spirometry parameters indicate airway obstruction such as predicted FEV1, FEV1/FVC, predicted PEF and predicted FEF25–75% with Spearman’s r were −0.187; −0.143; −0.091 and −0.195, respectively (all P<0.05), whereas no correlation between FeNO and FVC—an indicator of airway restriction—was found.

Conclusions

In these asthmatic patients in Vietnam, an inverse correlation was found between FeNO and the ACT score and between FeNO and spirometry indicators of airway obstruction. Therefore, FeNO may be a useful tool in asthma management.

Value of bronchial reversibility to salbutamol, exhaled nitric oxide and responsiveness to methacholine to corroborate the diagnosis of asthma in children

INTRODUCTION AND OBJECTIVES

Functional and inflammatory measures have been recommended to corroborate asthma diagnosis in schoolchildren, but the evidence in this regard is conflicting. We aimed to determine, in real-life clinical situation, the value of spirometry, spirometric bronchial reversibility to salbutamol (BDR), bronchial responsiveness to methacholine (MCT) and fractional exhaled nitric oxide (FENO), to corroborate the diagnosis of asthma in children on regular inhaled corticosteroids (ICS) referred from primary care.

METHODS

One hundred and seventy-seven schoolchildren with mild-moderate persistent asthma, on treatment with regular ICS, participated in the study. Abnormal tests were defined as FENO ≥ 27 ppb, BDR (FEV1 ≥ 12%) and methacholine PC20 ≤ 4 mg/mL.

RESULTS

The proportions of positive BDR, FENO and MCT, were 16.4%, 33.3%, and 87.0%, respectively. MCT was associated with FENO (p < 0.03) and BDR (p = 0.001); FENO was associated with BDR (p = 0.045), family history of asthma (p = 0.003) and use of asthma medication in the first two years of life (p = 0.004). BDR was significantly related with passive tobacco exposure (p = 0.003).

CONCLUSIONS

Spirometry, BDR and BDR had a poor performance for corroborating diagnosis in our asthmatic children on ICS treatment; on the contrary, MCT was positive in most of them, which agrees with previous reports. Although asthma tests are useful to corroborate asthma when positive, clinical diagnosis remains the best current approach for asthma diagnosis, at least while better objective and feasible measurements at the daily practice are available. At present, these tests may have a better role for assessing the management and progression of the condition.

Quantitative CT analysis for bronchiolitis obliterans in perinatally HIV-infected adolescents-comparison with controls and lung function data

OBJECTIVE

To compare quantitative chest CT parameters in perinatally HIV-infected adolescents with and without bronchiolitis obliterans compared with HIV-uninfected controls and their association with lung function measurements.

MATERIALS AND METHODS

Seventy-eight (41 girls) HIV-infected adolescents with a mean age of 13.8 ± 1.65 years and abnormal pulmonary function tests in the prospective Cape Town Adolescent Antiretroviral Cohort underwent contrast-enhanced chest CT on inspiration and expiration. Sixteen age-, sex-, and height-matched non-infected controls were identified retrospectively. Fifty-one HIV-infected adolescents (28 girls) displayed mosaic attenuation on expiration suggesting bronchiolitis obliterans. Pulmonary function tests were collected. The following parameters were obtained: low- and high-attenuation areas, mean lung density, kurtosis, skewness, ventilation heterogeneity, lung mass, and volume.

RESULTS

HIV-infected adolescents showed a significantly higher mean lung density, ventilation heterogeneity, mass, and high- and low-attenuation areas compared with non-infected individuals. Kurtosis and skewness were significantly lower as well. HIV-infected adolescents with bronchiolitis obliterans had a significantly lower kurtosis and skewness compared with those without bronchiolitis obliterans. Lung mass and volume showed the strongest correlations with forced expiratory volume in 1 s (FEV₁), forced vital capacity (FVC), and alveolar volume. Low-attenuation areas below - 950 HU and ventilation heterogeneity showed the strongest correlation with FEV₁/FVC (range, - 0.51 to - 0.34) and forced expiratory flow between 25 and 75% of FVC (range, - 0.50 to - 0.35).

CONCLUSION

Quantitative chest CT on inspiration is a feasible technique to differentiate perinatally HIV-infected adolescents with and without bronchiolitis obliterans. Quantitative CT parameters correlate with spirometric measurements of small-airway disease.

KEY POINTS

• Perinatally HIV-infected adolescents showed a more heterogeneous attenuation of the lung parenchyma with a higher percentage of low- and high-attenuation areas compared with non-infected patients. • Kurtosis and skewness are able to differentiate between HIV-infected adolescents with and without bronchiolitis obliterans using an inspiratory chest CT. • Quantitative CT parameters of the chest correlate significantly with pulmonary function test. Low-attenuation areas and ventilation heterogeneity are particularly associated with spirometric parameters related to airway obstruction.

Combining spirometry and fractional exhaled nitric oxide improves diagnostic accuracy for childhood asthma

OBJECTIVES

There are insufficient evidences supporting the use of spirometric indices along with tests for airway inflammation to improve diagnostic accuracy for asthma. We aimed to study the utility of combination of spirometric indices and fractional exhaled nitric oxide (FeNO) measured at the initial visit in diagnosing asthma.

METHODS

Consecutive children aged 8-16 years who were referred for evaluation of possible asthma were included. At referral, all participants completed FeNO measurements and spirometry. The diagnosis of asthma was established with conventional criteria. Diagnostic performance of the spirometric indices and FeNO was determined using receiver-operator characteristic (ROC) curve analyses.

RESULTS

Of 275 participants, 191 children were diagnosed with asthma and showed lower spirometric indices and higher FeNO than non-asthmatics. In the ROC curve analyses, forced expiratory flow between 25% and 75% of vital capacity (FEF_25-75 ) percent predicted demonstrated diagnostic performance with the area under the ROC curve (AUC) value of 0.81 (95% CI: 0.76-0.87) which was significantly higher than those for forced expiratory volume in the first second (FEV₁ ) percent predicted and FEV₁ /forced vital capacity. The combined use of FEF_25-75 percent predicted and FeNO improved the AUC to 0.90 (95% CI: 0.86-0.93). In addition, compared to FEF_25-75 percent predicted or FeNO alone, this combination improved sensitivity with comparable specificity.

CONCLUSIONS

FEF_25-75 percent predicted had a better diagnostic value in detection of childhood asthma than other standard spirometric indices and its combination with FeNO improves the diagnostic accuracy for childhood asthma.

The pragmatic role of FEF25-75 in asymptomatic subjects, allergic rhinitis, asthma, and in military setting

Introduction: The forced expiratory flow between 25% and 75% of forced vital capacity (FEF_25-75) is a spirometry parameter that may be useful in many clinical settings. Values <65% of predicted have been defined as abnormal.Areas covered: The current report discusses the clinical value of FEF_25-75 in different settingv, namely military medicine, primary care, and specialized clinic. Moreover, the predictive role of FEF_25-75 was discussed considering different patients' populations, including patients suffering from allergic rhinitis and/or asthma, as well as normal subjects. The most recent literature concerning the assessment of FEF_25-75 in these covered areas was searched.Expert opinion: In clinical practice, impaired values have been defined as a reliable surrogate marker for bronchial airflow limitation associated with early onset of asthma, bronchial hyperresponsiveness, lower airway inflammation, reversibility to bronchodilation testing, allergic sensitization, and uncontrolled asthma. In the military medicine setting, simple spirometry, including FEF_25-75, may suggest a series of fruitful information.

Indoor particulate matter and lung function in children

People generally spend more time indoors than outdoors resulting in a higher proportion of exposure to particulate matter (PM) occurring indoors. Consequently, indoor PM levels, in contrast to outdoor PM levels, may have a stronger relationship with lung function. To test this hypothesis, indoor and outdoor PM_2.5 and fungal spore data were simultaneously collected from the homes of forty-four asthmatic children aged 10-16 years. An optical absorption technique was utilized on the collected PM_2.5 mass to obtain concentrations of black carbon (BC) and ultraviolet light absorbing particulate matter, (UVPM; a marker of light absorbing PM_2.5 emitted from smoldering organics). Enrolled children completed spirometry after environmental measurements were made. Given the high correlation between PM_2.5, BC, and UVPM, principal component analysis was used to obtain uncorrelated summaries of the measured PM. Separate linear mixed-effect models were developed to estimate the association between principal components of the PM variables and spirometry values, as well as the uncorrelated original PM variables and spirometry values. A one-unit increase in the first principal component variable representing indoor PM (predominantly composed of UVPM and PM_2.5) was associated with 4.1% decrease (99% CI = -6.9, -1.4) in FEV₁/FVC ratio. 11.3 μg/m³ increase in indoor UVPM was associated with 6.4% and 14.7% decrease (99% CI = -10.4, -2.4 and 99% CI = -26.3, -2.9, respectively) in percent predicted FEV₁/FVC ratio and FEF_25-75 respectively. Additionally, 17.7 μg/m³ increase in indoor PM_2.5 was associated with 6.1% and 12.9% decrease (99% CI = -10.2, -1.9 and 99% CI = -24.9, -1.0, respectively) in percent predicted FEV₁/FVC ratio and FEF_25-75, respectively. Outdoor PM, indoor BC, and indoor fungal spores were not significantly associated with lung function. The results indicate that indoor PM is more strongly associated with lung function in children with asthma as compared with outdoor PM.