CFTR-function and ventilation inhomogeneity in individuals with cystic fibrosis

BACKGROUND

Increased (abnormal) ventilation inhomogeneity in individuals with mild Cystic Fibrosis (CF) lung disease may become a treatable trait for small-molecule therapeutics improving Cystic Fibrosis Transmembrane Regulator (CFTR) function. The relationship between CFTR function and ventilation inhomogeneity is unknown. We aimed to identify and quantify increased ventilation inhomogeneity in relation to CFTR function.

METHODS

This was an international, multi-center, cross-sectional study. We collated data from individuals aged 3-25 years with minimal (CFTR-MF) or residual (CFTR-RF) function of a variety of CFTR genotypes and FEV₁ ≥ 70% predicted. We measured lung function using nitrogen multiple-breath washout and spirometry. We compared lung clearance index (LCI) and FEV₁ between individuals with CFTR-MF vs CFTR-RF using a mixed effects multi-variable linear regression model to account for study differences and a logistic model based on propensity-score matching to adjust for possible confounding.

RESULTS

We included 141 with CFTR-MF and 35 with CFTR-RF. LCI (> 1.96 z-score) was elevated in 71.6% individuals with CFTR-MF and in 40.0% with CFTR-RF. FEV₁ (< -1.96 z-score) was reduced in 11.3% individuals with CFTR-MF and in 5.7% with CFTR-RF. The mean difference (95% CI) of LCI and FEV₁ between CFTR-MF and CFTR-RF was 3.71 (1.63 to 5.79) and -0.40 (-0.83 to 0.02) z-score. The LCI differences were similar after adjustment for confounders and in individuals with normal FEV₁.

CONCLUSION

Increased ventilation inhomogeneity is associated with less CFTR function. In individuals with mild CF lung disease, LCI can identify and quantify increased ventilation inhomogeneity, a candidate treatable trait.

Diagnosis of asthma in children: findings from the Swiss Paediatric Airway Cohort

INTRODUCTION

Diagnosing asthma in children remains a challenge because respiratory symptoms are not specific and vary over time.

AIM

In a real-life observational study, we assessed the diagnostic accuracy of respiratory symptoms, objective tests and two paediatric diagnostic algorithms (proposed by the Global Initiative for Asthma (GINA) and the National Institute for Health and Care Excellence (NICE)) in the diagnosis of asthma in school-aged children.

METHODS

We studied children aged 5-17 years who were referred consecutively to pulmonary outpatient clinics for evaluation of suspected asthma. Symptoms were assessed by parental questionnaire. The investigations included specific IgE measurement or skin prick tests, measurement of exhaled nitric oxide fraction (F _eNO), spirometry, body plethysmography and bronchodilator reversibility (BDR). Asthma was diagnosed by paediatric pulmonologists based on all available data. We assessed diagnostic accuracy of symptoms, tests and diagnostic algorithms by calculating sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and area under the curve (AUC).

RESULTS

Among 514 participants, 357 (70%) were diagnosed with asthma. The combined sensitivity and specificity was highest for any wheeze (sensitivity=75%, specificity=65%), dyspnoea (sensitivity=56%, specificity=76%) and wheeze triggered by colds (sensitivity=58%, specificity=78%) or by exercise (sensitivity=55%, specificity=74%). Of the diagnostic tests, the AUC was highest for specific total airway resistance (sR_tot; AUC=0.73) and lowest for the residual volume (RV)/total lung capacity (TLC) ratio (AUC=0.56). The NICE algorithm had sensitivity=69% and specificity=67%, whereas the GINA algorithm had sensitivity=42% and specificity=90%.

CONCLUSION

This study confirms the limited usefulness of single tests and existing algorithms for the diagnosis of asthma. It highlights the need for new and more appropriate evidence-based guidance.

Cigarette, shisha, and electronic smoking and respiratory symptoms in Swiss children: The LUIS study

BACKGROUND

Smoking habits in adolescents are changing. We assessed active smoking of conventional cigarettes, e-cigarettes and shishas in Swiss schoolchildren, studied risk factors and compared respiratory problems between smokers and non-smokers.

METHODS

We used data from LuftiBus in the school (LUIS), a school-based survey of respiratory health of children carried out 2013 to 2016 in the canton of Zurich, Switzerland. Participants were asked about use of cigarettes, shishas, and electronic smoking devices (ESD), and current respiratory symptoms. We studied associations between smoking and risk factors using logistic regression.

RESULTS

We included 3488 schoolchildren. Among 6 to 12-year-olds, 90/1905 (5%) had smoked occasionally (<once/week). Among 13 to 17-year-olds, 563/1583 (36%) had smoked occasionally of whom 414 smoked ESDs, 409 shishas, and 276 cigarettes. Among 13 to 17-year-olds who smoked frequently (≥once/week), 41/54 (76%) smoked cigarettes. A 22% of 15 to 17-year-olds (104/477) had used all three products. Smoking was more common in adolescents who were male (adjusted OR, 2.1; 95% CI, 1.7-2.6), lived in rural areas (1.8, 95% CI, 1.2-2.9 vs small urban), and whose mother (1.7, 95% CI, 1.3-2.3) or father (1.5, 95% CI, 1.2-1.9) smoked. Current respiratory symptoms like rhinitis, dyspnea, and wheeze were more common among frequent smokers (44%, 30%, 12%, respectively) and occasional smokers (32%, 22%, 13%) than in never smokers (29%,19%, 8%, P for trend <.05).

CONCLUSION

Smoking of shishas and ESDs is common among Swiss adolescents and often combined with smoking cigarettes. Adolescent smokers reported more respiratory symptoms than never smokers. We recommend smoking preventive strategies that include all forms of smoking.

Reported Symptoms Differentiate Diagnoses in Children with Exercise-Induced Respiratory Problems: Findings from the Swiss Paediatric Airway Cohort (SPAC)

BACKGROUND

Exercise-induced breathing problems with similar clinical presentations can have different etiologies. This makes distinguishing common diagnoses such as asthma, extrathoracic and thoracic dysfunctional breathing (DB), insufficient fitness, and chronic cough difficult.

OBJECTIVE

We studied which parent-reported, exercise-induced symptoms can help distinguish diagnoses in children seen in respiratory outpatient clinics.

METHODS

This study was nested in the Swiss Paediatric Airway Cohort, an observational study of children aged 0 to 17 years referred to pediatric respiratory outpatient clinics in Switzerland. We studied children aged 6 to 17 years and compared information on exercise-induced symptoms from parent-completed questionnaires between children with different diagnoses. We used multinomial regression to analyze whether parent-reported symptoms differed between diagnoses (asthma as base).

RESULTS

Among 1109 children, exercise-induced symptoms were reported for 732 (66%) (mean age: 11 years, 318 of 732 [43%] female). Among the symptoms, dyspnea best distinguished thoracic DB (relative risk ratio [RRR]: 5.4, 95% confidence interval [CI]: 1.3-22) from asthma. Among exercise triggers, swimming best distinguished thoracic DB (RRR: 2.4, 95% CI: 1.3-6.2) and asthma plus DB (RRR: 1.8, 95% CI: 0.9-3.4) from asthma only. Late onset of symptoms was less common for extrathoracic DB (RRR: 0.1, 95% CI: 0.03-0.5) and thoracic DB (RRR: 0.4, 95% CI: 0.1-1.2) compared with asthma. Localization of dyspnea (throat vs chest) differed between extrathoracic DB (RRR: 2.3, 95% CI: 0.9-5.8) and asthma. Reported respiration phase (inspiration or expiration) did not help distinguish diagnoses.

CONCLUSION

Parent-reported symptoms help distinguish different diagnoses in children with exercise-induced symptoms. This highlights the importance of physicians obtaining detailed patient histories.

Evaluation of a multiple breath nitrogen washout system in children

INTRODUCTION

The multiple breath nitrogen washout (MBW) test offers a sensitive measure of airway function. In this study we aim to (a) assess the validity of the EasyOne Pro LAB (MBW_ndd ) in an in vitro lung model, (b) assess the feasibility, repeatability, and reproducibility of MBW_ndd and (c) compare outcomes with the Exhalyzer D (MBW_EM ) and body plethysmography.

METHODS

In vitro, functional residual capacity (FRC) measurements were assessed using a lung model under quasi-physiological conditions and compared to measured FRC. In vivo plethysmography and MBW were performed in a prospective study of children at two visits (n = 45 healthy; n = 41 cystic fibrosis [CF]). Bland-Altman plots were used to compare agreement between FRC and lung clearance index (LCI) measurements.

RESULTS

In vitro FRC_ndd measurements were repeatable but lung volumes were underestimated (mean relative difference -5.4% (limits of agreement [LA] -9.6%; -1.1%), 95% confidence interval (CI) -6.27; -4.45). In vivo, compared to plethysmography, FRC_ndd was consistently lower (-19.3% [-40.5; 1.9], 95% CI [-23.9; -14.7]), and showed a volume dependency. LCI_ndd values were also higher in children with smaller lung volumes. The within-test coefficient of variation of the FRC_ndd and LCI_ndd were 4.9% in health, and 5.6% and 6.9% in CF respectively. LCI_ndd was reproducible between-visits (mean relative difference [LA] -3.7% [-14.8, -7.5; 95% CI -6.6; -0.73] in health [n = 17] and 0.34% [-13.2, 22.8; 95% CI -5.0; 5.69] in CF [n = 23]). When calculated using the same algorithm, LCI_ndd was similar to LCI_EM in health.

CONCLUSIONS

MBW_ndd measurements are feasible, repeatable, and reproducible, however, MBW-derived outcomes are not interchangeable with MBW_EM .

eNose breath prints as a surrogate biomarker for classifying patients with asthma by atopy

BACKGROUND

Electronic noses (eNoses) are emerging point-of-care tools that may help in the subphenotyping of chronic respiratory diseases such as asthma.

OBJECTIVE

We aimed to investigate whether eNoses can classify atopy in pediatric and adult patients with asthma.

METHODS

Participants with asthma and/or wheezing from 4 independent cohorts were included; BreathCloud participants (n = 429), Unbiased Biomarkers in Prediction of Respiratory Disease Outcomes adults (n = 96), Unbiased Biomarkers in Prediction of Respiratory Disease Outcomes pediatric participants (n = 100), and Pharmacogenetics of Asthma Medication in Children: Medication with Anti-Inflammatory Effects 2 participants (n = 30). Atopy was defined as a positive skin prick test result (≥3 mm) and/or a positive specific IgE level (≥0.35 kU/L) for common allergens. Exhaled breath profiles were measured by using either an integrated eNose platform or the SpiroNose. Data were divided into 2 training and 2 validation sets according to the technology used. Supervised data analysis involved the use of 3 different machine learning algorithms to classify patients with atopic versus nonatopic asthma with reporting of areas under the receiver operating characteristic curves as a measure of model performance. In addition, an unsupervised approach was performed by using a bayesian network to reveal data-driven relationships between eNose volatile organic compound profiles and asthma characteristics.

RESULTS

Breath profiles of 655 participants (n = 601 adults and school-aged children with asthma and 54 preschool children with wheezing [68.2% of whom were atopic]) were included in this study. Machine learning models utilizing volatile organic compound profiles discriminated between atopic and nonatopic participants with areas under the receiver operating characteristic curves of at least 0.84 and 0.72 in the training and validation sets, respectively. The unsupervised approach revealed that breath profiles classifying atopy are not confounded by other patient characteristics.

CONCLUSION

eNoses accurately detect atopy in individuals with asthma and wheezing in cohorts with different age groups and could be used in asthma phenotyping.

Connectivity patterns between multiple allergen specific IgE antibodies and their association with severe asthma

BACKGROUND

Allergic sensitization is associated with severe asthma, but assessment of sensitization is not recommended by most guidelines.

OBJECTIVE

We hypothesized that patterns of IgE responses to multiple allergenic proteins differ between sensitized participants with mild/moderate and severe asthma.

METHODS

IgE to 112 allergenic molecules (components, c-sIgE) was measured using multiplex array among 509 adults and 140 school-age and 131 preschool children with asthma/wheeze from the Unbiased BIOmarkers for the PREDiction of respiratory diseases outcomes cohort, of whom 595 had severe disease. We applied clustering methods to identify co-occurrence patterns of components (component clusters) and patterns of sensitization among participants (sensitization clusters). Network analysis techniques explored the connectivity structure of c-sIgE, and differential network analysis looked for differences in c-sIgE interactions between severe and mild/moderate asthma.

RESULTS

Four sensitization clusters were identified, but with no difference between disease severity groups. Similarly, component clusters were not associated with asthma severity. None of the c-sIgE were identified as associates of severe asthma. The key difference between school children and adults with mild/moderate compared with those with severe asthma was in the network of connections between c-sIgE. Participants with severe asthma had higher connectivity among components, but these connections were weaker. The mild/moderate network had fewer connections, but the connections were stronger. Connectivity between components with no structural homology tended to co-occur among participants with severe asthma. Results were independent from the different sample sizes of mild/moderate and severe groups.

CONCLUSIONS

The patterns of interactions between IgE to multiple allergenic proteins are predictors of asthma severity among school children and adults with allergic asthma.

Normative data for multiple breath washout outcomes in school-aged Caucasian children

Background

The multiple breath nitrogen washout (N2MBW) technique is increasingly used to assess the degree of ventilation inhomogeneity in school-aged children with lung disease. However, reference values for healthy children are currently not available. The aim of this study was to generate reference values for N2MBW outcomes in a cohort of healthy Caucasian school-aged children.

Methods

N2MBW data from healthy Caucasian school-age children between 6 and 18 years old were collected from four experienced centres. Measurements were performed using an ultrasonic flowmeter (Exhalyzer D, Eco Medics AG, Duernten, Switzerland) and were analysed with commercial software (Spiroware version 3.2.1, Eco Medics AG). Normative values and upper limits of normal (ULN) were generated for lung clearance index (LCI) at 2.5% (LCI2.5%) and at 5% (LCI5%) of the initial nitrogen concentration and for moment ratios (M1/M0 and M2/M0). A prediction equation was generated for functional residual capacity (FRC).

Results

Analysis used 485 trials from 180 healthy Caucasian children aged from 6 to 18 years old. While LCI increased with age, this increase was negligible (0.04 units·year–1 for LCI2.5%) and therefore fixed ULN were defined for this age group. These limits were 7.91 for LCI2.5%, 5.73 for LCI5%, 1.75 for M1/M0 and 6.15 for M2/M0, respectively. Height and weight were found to be independent predictors of FRC.

Conclusion

We report reference values for N2MBW outcomes measured on a commercially available ultrasonic flowmeter device (Exhalyzer D, Eco Medics AG) in healthy school-aged children to allow accurate interpretation of ventilation distribution outcomes and FRC in children with lung disease.

Preschool Multiple-Breath Washout Testing. An Official American Thoracic Society Technical Statement

BACKGROUND

Obstructive airway disease is nonuniformly distributed throughout the bronchial tree, although the extent to which this occurs can vary among conditions. The multiple-breath washout (MBW) test offers important insights into pediatric lung disease, not available through spirometry or resistance measurements. The European Respiratory Society/American Thoracic Society inert gas washout consensus statement led to the emergence of validated commercial equipment for the age group 6 years and above; specific recommendations for preschool children were beyond the scope of the document. Subsequently, the focus has shifted to MBW applications within preschool subjects (aged 2-6 yr), where a "window of opportunity" exists for early diagnosis of obstructive lung disease and intervention.

METHODS

This preschool-specific technical standards document was developed by an international group of experts, with expertise in both custom-built and commercial MBW equipment. A comprehensive review of published evidence was performed.

RESULTS

Recommendations were devised across areas that place specific age-related demands on MBW systems. Citing evidence where available in the literature, recommendations are made regarding procedures that should be used to achieve robust MBW results in the preschool age range. The present work also highlights the important unanswered questions that need to be addressed in future work.

CONCLUSIONS

Consensus recommendations are outlined to direct interested groups of manufacturers, researchers, and clinicians in preschool device design, test performance, and data analysis for the MBW technique.

An innovative lung model for multiple breath washout testing in health and disease

BACKGROUND

Multiple breath washout (MBW) is a lung function test that identifies the degree of ventilation inhomogeneity (VI) in the lungs. In vitro validation of MBW devices is recommended. So far, plastic lung models for MBW validation ignored variable degrees of VI. Our primary aim was to create a plastic lung model applicable for physiological lung volumes and variable VI.

METHODS

A plastic box divided in two chambers was filled with water and ventilated in various lung volumes and respiratory rates. A ventilator was used for efficient gas distribution (model with low VI). An additional divider was inserted to create a model with high VI. The model was connected to commercial MBW devices and measurements were performed using different tracer gases and conditions. Primary outcome was the precision of generated functional residual capacity (FRC) and the ability to generate variable VI. The latter was estimated by lung clearance index (LCI) and expiratory phase III slopes (SIII). LCI was also compared to a mathematical model.

FINDINGS

The intra-test variability for FRC was minimal, mean(SD) coefficient of variation 0.96(0.63)%, using different tracer gases under different conditions. Compared to the model with low VI, in the model with high VI LCI and washout SIII were significantly increased. LCI compared well to the mathematical model.

INTERPRETATION

This novel lung model shows excellent precision in lung volumes and VI estimates independent of tracer gases and conditions. The model can mimic the lungs of patients with uneven gas distribution.

Obstructive Sleep Apnoea in Children and Adolescents with Ehlers-Danlos Syndrome

BACKGROUND

In Ehlers-Danlos syndrome (EDS), a group of monogenic disorders affecting connective tissues, obstructive sleep apnoea (OSA) is highly prevalent in adults. The prevalence of OSA in children with EDS is unknown.

OBJECTIVES

This prospective cross-sectional study aimed at determining the prevalence of OSA in paediatric EDS patients.

METHODS

Children with EDS (n = 24) were recruited from the Children's Hospital Zurich and matched to healthy controls. Participants completed home respiratory polygraphy and questionnaires (Sleep-Related Breathing Disorder Scale [SRBD], Epworth Sleepiness Scale [ESS], and Child Health Questionnaire [CHQ]). The American Academy of Sleep Medicine criteria were applied for OSA diagnosis (obstructive apnoea-hypopnoea index [oAHI] ≥1/h). Conditional logistic regression was used to compare the prevalence of OSA and to adjust for possible confounding.

RESULTS

OSA was found in 42% of paediatric EDS patients and in 13% of matched controls (OR = 4.5, 95% CI = 0.97-20.83, p = 0.054). The median oAHI was higher in EDS patients than in controls (0.77/h, IQR = 0.19-1.76, vs. 0.24/h, IQR = 0.0-0.60, p < 0.001 adjusted for age, sex, and BMI z-score). EDS patients had lower scores in most CHQ scales and higher SRBD and ESS scores than controls (0.26, IQR = 0.1-0.35, vs. 0.07, IQR = 0-0.19, p = 0.004); 7 ± 4 vs. 5 ± 4, p = 0.033, respectively).

CONCLUSION

OSA is a previously underestimated EDS-related complication increasing disease burden.

The Swiss Paediatric Airway Cohort (SPAC)

Chronic respiratory symptoms, such as cough, wheeze and dyspnoea, are common in children; however, most research has, with the exception of a few large-scale clinical cohort studies, been performed in the general population or in small, highly-selected samples.

The Swiss Paediatric Airway Cohort (SPAC) is a national, prospective clinical cohort of children and adolescents who visit physicians for recurrent conditions, such as wheeze and cough, and exercise-related respiratory problems. The SPAC is an observational study and baseline assessment includes standardised questionnaires for families and data extracted from hospital records, including results of clinically indicated investigations, diagnoses and treatments. Outcomes are assessed through annual questionnaires, monthly symptom reporting via mobile phone and follow-up visits.

The SPAC will address important questions about clinical phenotypes, diagnosis, treatment, and the short- and long-term prognosis of common respiratory problems in children. The cohort currently consists of 347 patients from four major hospitals (Bern, Zurich, Basel and Lucerne), with 70–80 additional patients joining each month. More centres will join and the target sample size is a minimum of 3000 patients.

The SPAC will provide real-life data on children visiting the Swiss healthcare system for common respiratory problems and will provide a research platform for health services research and nested clinical and translational studies.

The Swiss Paediatric Airway Cohort (SPAC) is a unique research platform for common respiratory problems in childrenhttp://ow.ly/Y1v030lDnji

Alternate gas washout indices: Assessment of ventilation inhomogeneity in mild to moderate pediatric cystic fibrosis lung disease

INTRODUCTION

Normalized phase III slope (Sn_III ) indices from multiple breath washout (MBW) estimate ventilation inhomogeneity. Alternate (*) protocols for Sn_III indices exist, however the utility of these outcomes in children with mild-to-moderate cystic fibrosis (CF) is unknown.

METHODS

We measured nitrogen MBW and spirometry in 135 children (43 controls) aged 4-18 years. We assessed validity, practicability, and reliability of Sn_III protocols. Outcomes included the ability to detect abnormal lung function, test agreement, measurement duration, intra-test repeatability, and quality.

RESULTS

Lung clearance index (LCI) was abnormal in 80 (87%), Scond in 55 (60%), Scond* in 17 (19%), Sacin in 10 (11%), Sacin* in 11 (12%), and FEV₁ in 28 (30%). Alternate protocols reduced measurement duration. Agreement of indices to detect abnormal lung function was poor. The quality of analysis and repeatability deteriorated with the alternate technique compared to standard.

CONCLUSION

In children with mild-to-moderate CF lung disease, alternate protocols seem practical but clinimetric properties of standard Sn_III protocols are preferable.

Ventilation and perfusion assessed by functional MRI in children with CF: reproducibility in comparison to lung function

BACKGROUND

Chronic lung diseases such as cystic fibrosis (CF) can be monitored by imaging and lung function modalities. Magnetic resonance imaging (MRI) techniques such as matrix pencil (MP) decomposition allows for evaluation of regional impairment of fractional ventilation (R_FV) and relative perfusion (R_Q). However, reproducibility of MP MRI outcomes in children with CF is unknown. We examined short-term variability of ventilation and perfusion impairment from MP MRI and compared this to lung function outcomes.

METHOD

Twenty-threeCF and 12 healthy school-aged children underwent MRI and lung function tests on the same day on two occasions 24 h apart. Global ventilation inhomogeneity was assessed by the lung clearance index (LCI) from nitrogen-multiple breath washout (N₂-MBW) technique. Intra-class-coefficient (ICC), percentage change, and Bland-Altman limits of agreement were evaluated to assess reproducibility.

RESULTS

Sixty-nine measurements from MP MRI and N₂-MBW were performed. The ICC between two visits for R_FV, R_Q and LCI ranged between 0.60 and 0.90 in individuals with CF and healthy controls. In individuals with CF, percentage of change between the visits was 0.02% for R_FV, -1.11% for R_Q and 2.91% for LCI and limits of agreement between visits were - 4.3% and 3.9% for R_FV, -4.4% and 3.7% for R_Q, and -2.6 and 3.0 for LCI.

CONCLUSIONS

Functional imaging is reproducible and short-term changes in R_FV and R_Q greater than ±4.4% can be considered clinical meaningful. Very good short-term reproducibility, and easy application without the need for breathing maneuvers or contrast agent, makes MP MRI a promising surveillance method for CF.

Monitoring pulmonary health in Swiss childhood cancer survivors

BACKGROUND

Childhood cancer survivors are at increased risk for pulmonary morbidity and mortality. International guidelines recommend pulmonary function tests (PFT) during follow-up care. This nationwide study assessed how many children received PFT within 5 years after pulmotoxic treatment in Switzerland, types of tests, and predictors for testing.

METHODS

We included all children from the Swiss Childhood Cancer Registry who were diagnosed with cancer from 1990 to 2013 at age 0-16 years, survived for ≥2 years from diagnosis, and had pulmotoxic chemotherapy with bleomycin, busulfan, nitrosoureas, and/or chest radiotherapy. We searched medical records in all Swiss pediatric oncology clinics for PFT (spirometry, plethysmography, diffusion capacity of carbon monoxide [DLCO]) and treatment details.

RESULTS

We found medical records for 372 children, of whom 147 had pulmotoxic chemotherapy and 323 chest radiotherapy. Only 185 had plethysmography and/or spirometry (50%), 122 had DLCO (33%). Testing varied by cancer center from 3% to 79% (P = 0.001). Central nervous system tumor survivors and those not treated according to study protocols had less plethysmography and/or spirometry (odds ratio (OR) 0.3 and 0.3), lymphoma survivors and those who were symptomatic had more PFT (plethysmography and/or spirometry: OR 5.9 and 8.7; DLCO: OR 3.4 and 2.3). Cumulative incidence (CuI) of PFT was 52% in the first 5 years after pulmotoxic treatment; most of the tests were done in the first 2 years after treatment (CuI 44%).

CONCLUSION

Only half of the survivors exposed to pulmotoxic treatment have been followed up with PFT in Switzerland. We need to optimize, update, and implement monitoring guidelines.

Effect of intermittent inspiratory leaks on measurement of lung clearance index using nitrogen and sulfur hexafluoride

Nitrogen MBW is susceptible to leaks; effects of leaks on sulfur hexafluoride MBW require further study http://ow.ly/iY6o30lGchV.

Enhanced oxidative stress in smoking and ex-smoking severe asthma in the U-BIOPRED cohort

Oxidative stress is believed to be a major driver of inflammation in smoking asthmatics. The U-BIOPRED project recruited a cohort of Severe Asthma smokers/ex-smokers (SAs/ex) and non-smokers (SAn) with extensive clinical and biomarker information enabling characterization of these subjects. We investigated oxidative stress in severe asthma subjects by analysing urinary 8-iso-PGF2α and the mRNA-expression of the main pro-oxidant (NOX2; NOSs) and anti-oxidant (SODs; CAT; GPX1) enzymes in the airways of SAs/ex and SAn. All the severe asthma U-BIOPRED subjects were further divided into current smokers with severe asthma (CSA), ex-smokers with severe asthma (ESA) and non-smokers with severe asthma (NSA) to deepen the effect of active smoking. Clinical data, urine and sputum were obtained from severe asthma subjects. A bronchoscopy to obtain bronchial biopsy and brushing was performed in a subset of subjects. The main clinical data were analysed for each subset of subjects (urine-8-iso-PGF2α; IS-transcriptomics; BB-transcriptomics; BBr-transcriptomics). Urinary 8-iso-PGF2α was quantified using mass spectrometry. Sputum, bronchial biopsy and bronchial brushing were processed for mRNA expression microarray analysis. Urinary 8-iso-PGF2α was increased in SAs/ex, median (IQR) = 31.7 (24.5-44.7) ng/mmol creatinine, compared to SAn, median (IQR) = 26.6 (19.6-36.6) ng/mmol creatinine (p< 0.001), and in CSA, median (IQR) = 34.25 (24.4-47.7), vs. ESA, median (IQR) = 29.4 (22.3-40.5), and NSA, median (IQR) = 26.5 (19.6-16.6) ng/mmol creatinine (p = 0.004). Sputum mRNA expression of NOX2 was increased in SAs/ex compared to SAn (probe sets 203922_PM_s_at fold-change = 1.05 p = 0.006; 203923_PM_s_at fold-change = 1.06, p = 0.003; 233538_PM_s_at fold-change = 1.06, p = 0.014). The mRNA expression of antioxidant enzymes were similar between the two severe asthma cohorts in all airway samples. NOS2 mRNA expression was decreased in bronchial brushing of SAs/ex compared to SAn (fold-change = -1.10; p = 0.029). NOS2 mRNA expression in bronchial brushing correlated with FeNO (Kendal's Tau = 0.535; p< 0.001). From clinical and inflammatory analysis, FeNO was lower in CSA than in ESA in all the analysed subject subsets (p< 0.01) indicating an effect of active smoking. Results about FeNO suggest its clinical limitation, as inflammation biomarker, in severe asthma active smokers. These data provide evidence of greater systemic oxidative stress in severe asthma smokers as reflected by a significant changes of NOX2 mRNA expression in the airways, together with elevated urinary 8-iso-PGF2α in the smokers/ex-smokers group. Trial registration ClinicalTrials.gov-Identifier: NCT01976767.

Lipid phenotyping of lung epithelial lining fluid in healthy human volunteers

BACKGROUND

Lung epithelial lining fluid (ELF)-sampled through sputum induction-is a medium rich in cells, proteins and lipids. However, despite its key role in maintaining lung function, homeostasis and defences, the composition and biology of ELF, especially in respect of lipids, remain incompletely understood.

OBJECTIVES

To characterise the induced sputum lipidome of healthy adult individuals, and to examine associations between different ELF lipid phenotypes and the demographic characteristics within the study cohort.

METHODS

Induced sputum samples were obtained from 41 healthy non-smoking adults, and their lipid compositions analysed using a combination of untargeted shotgun and liquid chromatography mass spectrometry methods. Topological data analysis (TDA) was used to group subjects with comparable sputum lipidomes in order to identify distinct ELF phenotypes.

RESULTS

The induced sputum lipidome was diverse, comprising a range of different molecular classes, including at least 75 glycerophospholipids, 13 sphingolipids, 5 sterol lipids and 12 neutral glycerolipids. TDA identified two distinct phenotypes differentiated by a higher total lipid content and specific enrichments of diacyl-glycerophosphocholines, -inositols and -glycerols in one group, with enrichments of sterols, glycolipids and sphingolipids in the other. Subjects presenting the lipid-rich ELF phenotype also had significantly higher BMI, but did not differ in respect of other demographic characteristics such as age or gender.

CONCLUSIONS

We provide the first evidence that the ELF lipidome varies significantly between healthy individuals and propose that such differences are related to weight status, highlighting the potential impact of (over)nutrition on lung lipid metabolism.

Short-Term Effects of Elastic Chest Wall Restriction on Pulmonary Function in Children with Cystic Fibrosis

BACKGROUND

Elastic chest wall restriction introduced by Chevaillier is thought to reduce existing hyperinflation and improve mucus clearance from peripheral airways. In healthy adults, restriction decreases the functional residual capacity (FRC) and forced vital capacity (FVC), while ventilation inhomogeneity (lung clearance index [LCI]) increases. Pulmonary function response to restriction is unknown in individuals with cystic fibrosis (CF).

OBJECTIVES

To examine short-term effects of elastic chest wall restriction on pulmonary function in children with CF.

METHODS

Pulmonary function was first assessed twice 15 min apart at baseline and then again following 15 min of elastic chest wall restriction in 20 school-aged children with CF (12.3 ± 3.4 years). Primary outcomes were LCI from nitrogen multiple-breath washout, residual volume (RV), and FRC from plethysmography. Secondary outcomes were FVC and end-expiratory lung impedance (EELI) from electrical impedance tomography. Endpoints were test-retest reliability at baseline and lung function response to restriction, both on group and individual levels.

RESULTS

Test-retest reliability was excellent (intra-class correlation coefficients range 0.84-0.99). Following restriction, FRC significantly declined on average (95% CI) by -0.09 (-0.17 to -0.02) L. Similarly, FVC declined while LCI did not change. RV and EELI declined, but this did not reach statistical significance. On the individuals' level, heterogeneous changes in pulmonary function occurred following elastic chest wall restriction.

CONCLUSIONS

These findings indicate that the application of elastic chest wall restriction is safe, induces the intended decline in resting lung volume but does not systematically alter ventilation inhomogeneity in children with CF.

Comparison of different analysis algorithms to calculate multiple-breath washout outcomes

Lung clearance index (LCI) is the main outcome of the multiple-breath washout (MBW) test. Current recommendations for LCI acquisition are based on low-grade evidence. The aim of this study was to challenge those recommendations using alternative methods for LCI analysis. Nitrogen MBW measurements from school-aged children, 20 healthy controls, 20 with cystic fibrosis (CF) and 17 with primary ciliary dyskinesia (PCD), were analysed using 1) current algorithms (standard), 2) three alternative algorithms to detect with higher precision the end of MBW testing and 3) two alternative algorithms to determine exhaled tracer gas concentrations. LCI values, intra-test repeatability, and ability to discriminate between health and lung disease were compared between these methods. The analysis methods strongly influenced LCI (mean±sd overall differences (%) between standard and alternative analysis methods: -4.9±5.7%; range: -66-19%), but did not improve intra-test variability. Discrimination between health and disease was comparable as areas under the receiver operator curves were not greater than that from standard analysis. This study supports current recommendations for LCI calculation in children. Alternative methods influence LCI estimates and hamper comparability between MBW setups. Alternative algorithms, whenever used, should be carefully reported.

Large-Scale Label-Free Quantitative Mapping of the Sputum Proteome

Analysis of induced sputum supernatant is a minimally invasive approach to study the epithelial lining fluid and, thereby, provide insight into normal lung biology and the pathobiology of lung diseases. We present here a novel proteomics approach to sputum analysis developed within the U-BIOPRED (unbiased biomarkers predictive of respiratory disease outcomes) international project. We present practical and analytical techniques to optimize the detection of robust biomarkers in proteomic studies. The normal sputum proteome was derived using data-independent HDMS^E applied to 40 healthy nonsmoking participants, which provides an essential baseline from which to compare modulation of protein expression in respiratory diseases. The "core" sputum proteome (proteins detected in ≥40% of participants) was composed of 284 proteins, and the extended proteome (proteins detected in ≥3 participants) contained 1666 proteins. Quality control procedures were developed to optimize the accuracy and consistency of measurement of sputum proteins and analyze the distribution of sputum proteins in the healthy population. The analysis showed that quantitation of proteins by HDMS^E is influenced by several factors, with some proteins being measured in all participants' samples and with low measurement variance between samples from the same patient. The measurement of some proteins is highly variable between repeat analyses, susceptible to sample processing effects, or difficult to accurately quantify by mass spectrometry. Other proteins show high interindividual variance. We also highlight that the sputum proteome of healthy individuals is related to sputum neutrophil levels, but not gender or allergic sensitization. We illustrate the importance of design and interpretation of disease biomarker studies considering such protein population and technical measurement variance.