Sputum proteomics and airway cell transcripts of current and ex-smokers with severe asthma in U-BIOPRED: an exploratory analysis

Severe asthma patients with a significant smoking history have airflow obstruction with reported neutrophilia. We hypothesise that multi-omic analysis will enable the definition of smoking and ex-smoking severe asthma molecular phenotypes.The U-BIOPRED cohort of severe asthma patients, containing current-smokers (CSA), ex-smokers (ESA), nonsmokers and healthy nonsmokers was examined. Blood and sputum cell counts, fractional exhaled nitric oxide and spirometry were obtained. Exploratory proteomic analysis of sputum supernatants and transcriptomic analysis of bronchial brushings, biopsies and sputum cells was performed.Colony-stimulating factor (CSF)2 protein levels were increased in CSA sputum supernatants, with azurocidin 1, neutrophil elastase and CXCL8 upregulated in ESA. Phagocytosis and innate immune pathways were associated with neutrophilic inflammation in ESA. Gene set variation analysis of bronchial epithelial cell transcriptome from CSA showed enrichment of xenobiotic metabolism, oxidative stress and endoplasmic reticulum stress compared to other groups. CXCL5 and matrix metallopeptidase 12 genes were upregulated in ESA and the epithelial protective genes, mucin 2 and cystatin SN, were downregulated.Despite little difference in clinical characteristics, CSA were distinguishable from ESA subjects at the sputum proteomic level, with CSA patients having increased CSF2 expression and ESA patients showing sustained loss of epithelial barrier processes.

Infant multiple breath washout using a new commercially available device: Ready to replace the previous setup?

INTRODUCTION

Multiple breath washout (MBW) is a sensitive test to measure lung volumes and ventilation inhomogeneity from infancy on. The commonly used setup for infant MBW, based on ultrasonic flowmeter, requires extensive signal processing, which may reduce robustness. A new setup may overcome some previous limitations but formal validation is lacking.

AIM

We assessed the feasibility of infant MBW testing with the new setup and compared functional residual capacity (FRC) values of the old and the new setup in vivo and in vitro.

METHODS

We performed MBW in four healthy infants and four infants with cystic fibrosis, as well as in a Plexiglas lung simulator using realistic lung volumes and breathing patterns, with the new (Exhalyzer D, Spiroware 3.2.0, Ecomedics) and the old setup (Exhalyzer D, WBreath 3.18.0, ndd) in random sequence.

RESULTS

The technical feasibility of MBW with the new device-setup was 100%. Intra-subject variability in FRC was low in both setups, but differences in FRC between the setups were considerable (mean relative difference 39.7%, range 18.9; 65.7, P = 0.008). Corrections of software settings decreased FRC differences (14.0%, -6.4; 42.3, P = 0.08). Results were confirmed in vitro.

CONCLUSION

MBW measurements with the new setup were feasible in infants. However, despite attempts to correct software settings, outcomes between setups were not interchangeable. Further work is needed before widespread application of the new setup can be recommended.

Leaks during multiple-breath washout: characterisation and influence on outcomes

Nitrogen multiple-breath washout (N₂MBW) is increasingly used in patients with cystic fibrosis. The current European Respiratory Society/American Thoracic Society consensus statement for MBW recommends the rejection of measurements with leaks. However, it is unclear whether this is necessary for all types of leaks. Here, our aim was to 1) model and 2) apply air leaks, and 3) to assess their influence on the primary MBW outcomes of lung clearance index and functional residual capacity.

We investigated the influence of air leaks at various locations (pre-, intra- and post-capillary), sizes, durations and stages of the washout. Modelled leaks were applied to existing N₂MBW data from 10 children by modifying breath tables. In addition, leaks were applied to the equipment during N₂MBW measurements performed by one healthy adolescent.

All modelled and applied leaks resulted in statistically significant but heterogeneous effects on lung clearance index and functional residual capacity. In all types of continuous inspiratory leaks exceeding a certain size, the end of the washout was not reached. For practical application, we illustrated six different “red flags”, i.e. signs that enable easy identification of leaks during measurements.

Air leaks during measurement significantly influence N₂MBW outcomes. The influence of leaks on MBW outcomes is dependent on the location, relation to breath cycle, duration, stage of washout and size of the leak. We identified a range of signs to help distinguish leaks from physiological noise.

The influence of leaks on nitrogen MBW outcomes is complex, dynamic and dependent on the size, duration, location and position of leaks during the washout and breathing cyclehttp://ow.ly/PbHV30hB91H

Multiple breath washout in pediatric patients after lung transplantation

Forced expiratory volume in 1 second (FEV₁ ) from spirometry is the most commonly used parameter to detect early allograft dysfunction after lung transplantation (LTx). There are concerns regarding its sensitivity. Nitrogen-multiple breath washout (N₂ -MBW) is sensitive at detecting early global (lung clearance index [LCI]) and acinar (S_acin ) airway inhomogeneity. We investigated whether N₂ -MBW indices indicate small airways pathology after LTx in children with stable spirometry. Thirty-seven children without bronchiolitis obliterans syndrome [BOS] at a median of 1.6 (0.6-3.0) years after LTx underwent N₂ -MBW and spirometry, 28 of those on 2 occasions (≤6 months apart) during clinically stable periods. Additional longitudinal data (11 and 8 measurements, respectively) are provided from 2 patients with BOS. In patients without BOS, LCI and S_acin were significantly elevated compared with healthy controls. LCI was abnormal at the 2 test occasions in 81% and 71% of patients, respectively, compared with 30% and 39% of patients with abnormal FEV₁ /forced vital capacity (FVC). Correlations of LCI with FEV₁ /FVC (r = 0.1, P = .4) and FEV₁ (r = -0.1, P = .6) were poor. N₂ -MBW represents a sensitive and reproducible tool for the early detection of airways pathology in stable transplant recipients. Moreover, indices were highly elevated in both patients with BOS. Spirometry and LCI showed poor correlation, indicating distinct and complementary physiologic measures.

Inert Gas Washout in Bronchiolitis Obliterans Following Hematopoietic Cell Transplantation

BACKGROUND

Bronchiolitis obliterans syndrome (BOS) is a leading cause of chronic graft-vs-host disease (cGvHD) and is associated with mortality after allogeneic hematopoietic stem cell transplantation (alloHSCT). The nitrogen multiple breath washout test (N₂-MBW) measures ventilation inhomogeneity, a biomarker of central and peripheral airway obstruction. The aim of this study was to examine ventilation inhomogeneity according to cGvHD score and histologically defined bronchiolitis obliterans (BO).

METHODS

This single-center prospective cross-sectional study included 225 adults (mean age, 52.8 years; median, 5.4 years [interquartile range, 2.0-11 years]) after alloHSCT. Outcomes were global (lung clearance index [LCI]) and acinar ventilation inhomogeneity index (S_ACIN) from N₂-MBW. Patients were categorized into five groups: (1) no cGvHD and no obstruction (cGvHD overall score 0 and FEV₁/FVC ≥ 70) (2) cGvHD and no obstruction (cGvHD overall score 1-3 and FEV₁/FVC ≥ 70), (3) BOS with or without cGvHD (if available, no BO on histologic examination, and FEV₁/FVC < 70), (4) histologically proven BO, and (5) diffuse parenchymal lung disease other than BO.

RESULTS

The LCI and S_ACIN differed significantly between groups (P < .001) and increased progressively according to cGvHD score. In BO, the LCI and S_ACIN were elevated in 95.5% and 81.8% of patients, respectively, whereas FEV₁/FVC was abnormal in only 56.5% of patients, respectively.

CONCLUSIONS

N₂-MBW is highly sensitive for detecting abnormal lung function in patients following alloHSCT. LCI and S_ACIN seem to be promising biomarkers of lung involvement in cGvHD.

Novel magnetic resonance technique for functional imaging of cystic fibrosis lung disease

Lung function tests are commonly used to monitor lung disease in cystic fibrosis (CF). While practical, they cannot locate the exact origin of functional impairment. Contemporary magnetic resonance imaging (MRI) techniques provide information on the location of disease but the need for contrast agents constrains their repeated application. We examined the correlation between functional MRI, performed without administration of contrast agent, and lung clearance index (LCI) from nitrogen multiple-breath washout (N2-MBW).

40 children with CF (median (range) age 12.0 (6–18) years) and 12 healthy age-matched controls underwent functional and structural MRI and lung function tests on the same day. Functional MRI provided semiquantitative measures of perfusion (RQ) and ventilation (RFV) impairment as percentages of affected lung volume. Morphological MRI was evaluated using CF-specific scores. LCI measured global ventilation inhomogeneity.

MRI detected functional impairment in CF:RFV19–38% andRQ16–35%.RFVandRQcorrelated strongly with LCI (r=0.76, p<0.0001 and r=0.85, p<0.0001, respectively), as did total morphology score (r=0.81, p<0.0001). All indices differed significantly between patients with CF and healthy controls (p<0.001).

Noninvasive functional MRI is a promising method to detect and visualise perfusion and ventilation impairment in CF without the need for contrast agents.

Elevated lung clearance index in infants with cystic fibrosis shortly after birth

It is not known at what age lung function impairment may arise in children with cystic fibrosis (CF). We assessed lung function shortly after birth in infants with CF diagnosed by newborn screening.We performed infant lung function measurements in a prospective cohort of infants with CF and healthy controls. We assessed lung clearance index (LCI), functional residual capacity (FRC) and tidal breathing parameters. The primary outcome was prevalence and severity of abnormal lung function (±1.64 z-scores) in CF.We enrolled 53 infants with CF (mean age 7.8 weeks) and 57 controls (mean age 5.2 weeks). Compared to controls, LCI and FRC were elevated (mean difference 0.30, 95% CI 0.02-0.60; p=0.034 and 14.5 mL, 95% CI 7.7-21.3 mL; p<0.001, respectively), while ratio of time to peak tidal expiratory flow to expiratory time was decreased in infants with CF. In 22 (41.5%) infants with CF, either LCI or FRC exceeded 1.64 z-scores; three infants had both elevated LCI and FRC.Shortly after birth, abnormal lung function is prevalent in CF infants. Ventilation inhomogeneity or hyperinflation may serve as noninvasive markers to monitor CF lung disease and specific treatment effects, and could thus be used as outcome parameters for future intervention studies in this age group.

Inert gas washout: background and application in various lung diseases

Multiple breath inert gas washout (MBW) is a lung function technique to measure ventilation inhomogeneity. The technique was developed more than 60 years ago, but not much used for many decades. Technical improvements, easy protocols and higher sensitivity compared with standard lung function tests in some disease groups have led to a recent renaissance of MBW. The lung clearance index (LCI) is a common measure derived from MBW tests, and offers information on lung pathology complementary to that from conventional lung function tests such as spirometry. The LCI measures the overall degree of pulmonary ventilation inhomogeneity. There are other MBW-derived parameters, which describe more regional airway ventilation and enable specific information on conductive or acinar ventilation inhomogeneity. How this specific ventilation distribution is exactly related to different disease processes has not entirely been examined yet. MBW measurements are performed during tidal breathing, making this technique attractive for children, even young children and infants. These benefits and the additional physiological information on ventilation inhomogeneity early in the course of lung diseases have led to increasing research activities and clinical application of MBW, especially in paediatric lung diseases such as cystic fibrosis (CF). In these patients, LCI detects early airway damage and enables monitoring of disease progression and treatment response. Guidelines for the standardisation of the MBW technique were recently published. These guidelines will, hopefully, increase comparability of LCI data obtained in different centres or intervention trials in children and adults. In this non-systematic review article, we provide an overview of recent developments in MBW, with a special focus on children. We first explain the physiological and technical background to this technique with a short explanation of several methodological aspects that are important for understanding the principle behind the technique and enable high quality measurements. We then provide examples of MBW application in different lung diseases of children and adults, with regards to both clinical application and research activities. Lastly, we report on ongoing clinical trials using MBW as outcome and give an outlook on possible future developments.

A simple method to reconstruct the molar mass signal of respiratory gas to assess small airways with a double-tracer gas single-breath washout

For the assessment of small airway diseases, a noninvasive double-tracer gas single-breath washout (DTG-SBW) with sulfur hexafluoride (SF₆) and helium (He) as tracer components has been proposed. It is assumed that small airway diseases may produce typical ventilation inhomogeneities which can be detected within one single tidal breath, when using two tracer components. Characteristic parameters calculated from a relative molar mass (MM) signal of the airflow during the washout expiration phase are analyzed. The DTG-SBW signal is acquired by subtracting a reconstructed MM signal without tracer gas from the signal measured with an ultrasonic sensor during in- and exhalation of the double-tracer gas for one tidal breath. In this paper, a simple method to determine the reconstructed MM signal is presented. Measurements on subjects with and without obstructive lung diseases including the small airways have shown high reliability and reproducibility of this method.

Alternative inert gas washout outcomes in patients with primary ciliary dyskinesia

The lung clearance index (LCI) derived from a nitrogen multiple breath washout test (N2-MBW) is a promising tool to assess small airways disease in primary ciliary dyskinesia, but it is difficult to apply in routine clinical settings because of its long measuring time. In this study, we aimed to assess alternative indices derived from shorter washout protocols.

49 patients with primary ciliary dyskinesia (mean age 14.7±6.6 years) and 37 controls (mean age 14.3±1.4 years) performed N2-MBW and double-tracer gas (DTG) single-breath washout tests. Global (LCI and moment ratio (M2/M0)), conductive (Scond) and acinar ventilation inhomogeneity (DTG Slope III (SIII-DTG)) were determined for each individual. The main outcomes were 1) the ability to detect abnormal lung function from washout indices (>1.64 z-scores) and 2) measurement duration.

The prevalence of abnormal values for LCI2.5% was 37 out of 47 (79%), for LCI5% was 34 out of 47 (72%), for M2/M0 was 34 out of 47 (72%), for Scond was 36 out of 46 (78%) and for SIII-DTG was 12 out of 35 (34%). Mean±sd duration of measurement was 19.8±11.2 min for LCI2.5%, 10.8±4.6 min for LCI5% and 8.6±2.3 min for Scond.

Compared to standard LCI2.5%, ventilation inhomogeneity was detected by LCI5%, moment ratio and Scond with comparable sensitivity while measurement duration was significantly shorter. Longitudinal studies will show which outcome is most suitable and practical in terms of sensitivity, duration and variability within the course of primary ciliary dyskinesia lung disease.

Agreement between multiple-breath nitrogen washout systems in children and adults

BACKGROUND

Comparability of multiple breath washout (MBW) systems has been little explored. We assessed agreement in lung clearance index (LCI) from two similar, commercial nitrogen MBW setups in patients with Cystic Fibrosis (CF) and controls.

METHODS

The EasyOne Pro (NDD) and Exhalyzer D (EM) were randomly applied in 85 adults (34 with CF) and 97 children (47 with CF and normal forced expiratory volume in one second). We assessed differences between setups in LCI, lung volumes and breathing pattern and diagnostic performance for detecting abnormal lung function.

RESULTS

Compared to NDD, EM measured higher LCI, functional residual capacity and cumulative expired volume while respiratory rate was lower. Mean difference (limits of agreement) in LCI was 1.30 (-2.34 to 4.94). In CF, prevalence of abnormal LCI was greater in children and similar in adults using EM compared to NDD.

CONCLUSIONS

Agreement of MBW outcomes between setups is poor and explained by nitrogen measurement techniques and breathing pattern.

Lung clearance index and moment ratios at different cut-off values in infant multiple-breath washout measurements

BACKGROUND

Multiple-breath washout (MBW) is increasingly used for infant lung function testing. Current guidelines recommend calculating lung clearance index (LCI) and functional residual capacity (FRC) at 2.5% of normalized tracer gas concentration, without clear recommendation for moment ratios (MR). Whether the 2.5% cut-off has the highest discriminative power to detect ventilation inhomogeneity in infants with lung diseases is unknown.

METHODS

We used sulfur-hexafluoride MBW measurements from 32 infants with cystic fibrosis, 32 preterm infants, and 32 healthy controls at postmenstrual age of 41-54 weeks. We compared the discriminative power to detect pathological values above the upper limit of normal for 12 different cut-offs between 20% and 1.5% for first and second MR (MR1, MR2), LCI, and FRC.

RESULTS

MR and LCI results changed significantly at different cut-offs. Mean MR2 in infants with cystic fibrosis increased from 2.4 to 7.2 units between 20% and 1.5% SF₆ . The ability of MR and LCI to discriminate between health and disease increased significantly with lower cut-offs. The 1.5% cut-off showed highest discriminative power: in infants with cystic fibrosis pathological MR2 values were found in 27 out of 89 (30%) and for LCI in 28/89 (32%). In preterm infants, pathological MR2 values were detected in 39 out of 73 (53%), and for LCI in 35/73 (48%). FRC remained stable throughout the washout.

CONCLUSION

In infants, the diagnostic performance of MBW strongly depends on the point of analysis. The cut-off with the highest discriminative power to detect ventilation inhomogeneity in infants with cystic fibrosis and after preterm birth was at 1.5% tracer gas concentration. Pediatr Pulmonol. 2016;51:1373-1381. © 2016 Wiley Periodicals, Inc.

Feasibility of nitrogen multiple-breath washout in inexperienced children younger than 7 years

BACKGROUND

Multiple breath washout (MBW) is an attractive test to assess ventilation inhomogeneity, a marker of peripheral lung disease. Systematic research on MBW feasibility in preschool children is scanty.

OBJECTIVES

We assessed feasibility of nitrogen MBW in children aged 3-7 years in a clinical setting applying current ERS/ATS consensus.

METHODS

Sixty-two children with asthma were enrolled in the Swiss rehabilitation center Hochgebirgsklinik Davos without MBW experience and prior to consensus release. Age range was 3.1-6.7 years. All children were naïve to MBW, received training, and then aimed for triplicate nitrogen MBW within 20 min. We afterward assessed the number of MBW attempts and successful tests according to consensus asking for three technically acceptable trials with functional residual capacity (FRC) measurements within 25% of median FRC. Secondly, factors related to success rate and FRC variability were assessed.

RESULTS

Out of 205 MBW attempts in 62 children, 103 trials (50%) in 51 children were successful. Only 15 children (24%) achieved three valid trials as suggested by consensus. At least two valid trials were obtained in 37 children (60%). Age was positively correlated with success rate. FRC variability was inversely correlated with variability of tidal volume.

CONCLUSIONS

MBW was only feasible in one quarter of inexperienced children <7 years applying strict consensus criteria. Low FRC variability and low breathing variability seem to be mutually exclusive at this age group. Specific consensus recommendations for MBW in preschool children seem, thus, warranted. Pediatr Pulmonol. 2016;51:1183-1190. © 2016 Wiley Periodicals, Inc.