Lung Clearance Index to Track Acute Respiratory Events in School-Age Children with Cystic Fibrosis.

Rationale: The lung clearance index (LCI) is responsive to acute respiratory events in preschool children with cystic fibrosis (CF), but its utility to identify and manage these events in school-age children with CF is not well defined.Objectives: To describe changes in LCI with acute respiratory events in school-age children with CF.Methods: In a multisite prospective observational study, the LCI and FEV1 were measured quarterly and during acute respiratory events. Linear regression was used to compare relative changes in LCI and FEV1% predicted at acute respiratory events. Logistic regression was used to compare the odds of a significant worsening in LCI and FEV1% predicted at acute respiratory events. Generalized estimating equation models were used to account for repeated events in the same subject.Measurements and Main Results: A total of 98 children with CF were followed for 2 years. There were 265 acute respiratory events. Relative to a stable baseline measure, LCI (+8.9%; 95% confidence interval, 6.5 to 11.3) and FEV1% predicted (-6.6%; 95% confidence interval, -8.3 to -5.0) worsened with acute respiratory events. A greater proportion of events had a worsening in LCI compared with a decline in FEV1% predicted (41.7% vs. 30.0%; P = 0.012); 53.9% of events were associated with worsening in LCI or FEV1. Neither LCI nor FEV1 recovered to baseline values at the next follow-up visit.Conclusions: In school-age children with CF, the LCI is a sensitive measure to assess lung function worsening with acute respiratory events and incomplete recovery at follow-up. In combination, the LCI and FEV1 capture a higher proportion of events with functional impairment.

Determinants of lung disease progression measured by lung clearance index in children with cystic fibrosis.

The lung clearance index (LCI) measured by the multiple breath washout (MBW) test is sensitive to early lung disease in children with cystic fibrosis. While LCI worsens during the preschool years in cystic fibrosis, there is limited evidence to clarify whether this continues during the early school age years, and whether the trajectory of disease progression as measured by LCI is modifiable.A cohort of children (healthy and cystic fibrosis) previously studied for 12 months as preschoolers were followed during school age (5-10 years). LCI was measured every 3 months for a period of 24 months using the Exhalyzer D MBW nitrogen washout device. Linear mixed effects regression was used to model changes in LCI over time.A total of 582 MBW measurements in 48 healthy subjects and 845 measurements in 64 cystic fibrosis subjects were available. The majority of children with cystic fibrosis had elevated LCI at the first preschool and first school age visits (57.8% (37 out of 64)), whereas all but six had normal forced expiratory volume in 1 s (FEV1) values at the first school age visit. During school age years, the course of disease was stable (-0.02 units·year-1 (95% CI -0.14-0.10). LCI measured during preschool years, as well as the rate of LCI change during this time period, were important determinants of LCI and FEV1, at school age.Preschool LCI was a major determinant of school age LCI; these findings further support that the preschool years are critical for early intervention strategies.

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.

Progression of Lung Disease in Preschool Patients with Cystic Fibrosis.

RATIONALE: Implementation of intervention strategies to prevent lung damage in early cystic fibrosis (CF) requires objective outcome measures that capture and track lung disease. OBJECTIVES: To define the utility of the Lung Clearance Index (LCI), measured by multiple breath washout, as a means to track disease progression in preschool children with CF. METHODS: Children with CF between the ages of 2.5 and 6 years with a confirmed diagnosis of CF and age-matched healthy control subjects were enrolled at three North American CF centers. Multiple breath washout tests were performed at baseline, 1, 3, 6, and 12 months to mimic time points chosen in clinical care and interventional trials; spirometry was also conducted. A generalized linear mixed-effects model was used to distinguish LCI changes associated with normal growth and development (i.e., healthy children) from the progression of CF lung disease. MEASUREMENTS AND MAIN RESULTS: Data were collected on 156 participants with 800 LCI measurements. Although both LCI and spirometry discriminated health from disease, only the LCI identified significant deterioration of lung function in CF over time. The LCI worsened during cough episodes and pulmonary exacerbations, whereas similar symptoms in healthy children were not associated with increased LCI values. CONCLUSIONS: LCI is a useful marker to track early disease progression and may serve as a tool to guide therapies in young patients with CF.

Effect of equipment dead space on multiple breath washout measures.

BACKGROUND AND OBJECTIVE: Multiple breath inert gas washout (MBW) systems are designed to minimize equipment dead space volume (Vd). Animal and infant studies have demonstrated the impact of increased Vd on MBW measurements. In this study, we investigate the effect of Vd of a nitrogen (N2 ) MBW system on MBW measurements in preschool children. METHODS: N2 MBW measurements were performed in healthy adults under standard conditions; Vd was added to match the relationship between Vd and lung volumes observed in preschool children. Subsequently, subjects were measured on a sulfur hexafluoride (SF6 ) MBW system under standard conditions and with Vd added to match that of the N2 MBW system. Healthy preschool children and children with cystic fibrosis were tested on both the N2 MBW and SF6 MBW in random order on the same day. A correction equation was derived based on the adult experiments and tested on the preschool data. RESULTS: Increasing the Vd of the N2 MBW system resulted in a higher lung clearance index (LCI). A strong non-linear relationship between N2 LCI and the Vd/tidal volume was observed. When the Vd was equivalent between systems, LCI measured by the SF6 MBW system was similar to that measured by the N2 MBW. LCI was higher on the N2 MBW than the SF6 MBW in preschool children. Correcting for the equipment Vd of the N2 MBW resulted in better agreement. CONCLUSIONS: Equipment Vd affects LCI measurements especially in young children where Vd is large relative to lung volumes.

Lung clearance index as an outcome measure for clinical trials in young children with cystic fibrosis. A pilot study using inhaled hypertonic saline.

RATIONALE: Lung clearance index (LCI), measured by multiple breath washout (MBW), is a noninvasive measure of ventilation inhomogeneity that holds promise as an objective physiologic endpoint for clinical trials in infants and preschool children with cystic fibrosis (CF). OBJECTIVES: To study the feasibility of using LCI to assess treatment effect outcomes in CF trials of infants and preschoolers. METHODS: The Infant Study of Inhaled Saline trial was a multicenter, randomized, controlled trial of hypertonic (7%) versus isotonic (0.9%) saline inhaled twice daily for 48 weeks in children with CF under 6 years of age. LCI measurements were performed in a single-center pilot substudy at baseline and 48 weeks using a respiratory mass spectrometer and sulfur hexafluoride as the tracer gas. LCI measurements were standardized using published normative data (zLCI) to account for height-related changes in LCI during early childhood. A generalized estimating equation model with an interaction between treatment group and test occasion was used to estimate a treatment effect. MEASUREMENTS AND MAIN RESULTS: A total of 27 participants were randomized; 25 participants, aged (median [range]) 2.6 (0.34-4.95) years, had acceptable baseline and follow-up LCI measures. On average, LCI decreased in the hypertonic saline group (n = 12) by 1.19 z-scores units (95% confidence interval [CI] = -2.46 to 0.06), and remained stable in the isotonic saline group (n = 13) at 0.81 (95% CI = -0.40 to 2.02). A significant treatment effect was observed for zLCI (2.01; 95% CI = 0.26 to 3.76; P = 0.025). CONCLUSIONS: MBW testing is feasible in an interventional study in infants and preschool children with CF. These pilot findings support the development of MBW and LCI as an objective outcome measure in interventional trials in young children with CF, and provide estimates for sample size calculations for future studies.

Riociguat for the treatment of Phe508del homozygous adults with cystic fibrosis.

BACKGROUND: Riociguat is a first-in-class soluble guanylate cyclase stimulator for which preclinical data suggested improvements in cystic fibrosis transmembrane conductance regulator (CFTR) function. METHODS: This international, multicenter, two-part, Phase II study of riociguat enrolled adults with cystic fibrosis (CF) homozygous for Phe508del CFTR. Part 1 was a 28-day, randomized, double-blind, placebo-controlled study in participants not receiving CFTR modulator therapy. Twenty-one participants were randomized 1:2 to placebo or oral riociguat (0.5 mg three times daily [tid] for 14 days, increased to 1.0 mg tid for the subsequent 14 days). The primary and secondary efficacy endpoints were change in sweat chloride concentration and percent predicted forced expiratory volume in 1 second (ppFEV1), respectively, from baseline to Day 14 and Day 28 with riociguat compared with placebo. RESULTS: Riociguat did not alter CFTR activity (change in sweat chloride) or lung function (change in ppFEV1) at doses up to 1.0 mg tid after 28 days. The most common drug-related adverse event (AE) was headache occurring in three participants (21%); serious AEs occurred in one participant receiving riociguat (7%) and one participant receiving placebo (14%). This safety profile was consistent with the underlying disease and the known safety of riociguat for its approved indications. CONCLUSIONS: The Rio-CF study was terminated due to lack of efficacy and the changing landscape of CF therapeutic development. The current study⁠, within its limits of a small sample size, did not provide evidence that riociguat could be a valid treatment option for CF. CLINICAL TRIAL REGISTRATION NUMBER: NCT02170025.

Hypertonic saline improves the LCI in paediatric patients with CF with normal lung function.

BACKGROUND AND AIMS Sensitive outcome measures to assess the efficacy of therapeutic interventions in patients with cystic fibrosis (CF) with mild lung disease are currently lacking. Our objective was to study the ability of the lung clearance index (LCI), a measure of ventilation inhomogeneity, to detect a treatment response to hypertonic saline inhalation in paediatric patients with CF with normal spirometry. METHODS In a crossover trial, 20 patients with CF received 4 weeks of hypertonic saline (HS) and isotonic saline (IS) in a randomised sequence separated by a 4 week washout period. The primary end point was the change in the LCI due to HS versus IS. RESULTS Baseline characteristics including the LCI were not significantly different between both study periods. Four weeks of twice-daily HS inhalation significantly improved the LCI compared with IS (1.16, 95% CI 0.26 to 2.05; p=0.016), whereas other outcome measures such as spirometry and quality of life failed to reach statistical significance. Randomisation order had no significant impact on the treatment effect. CONCLUSIONS The LCI, but not spirometry was able to detect a treatment effect from HS inhalation in patients with CF with mild disease and may be a suitable tool to assess early intervention strategies in this patient population. Clinical trial number NCT00635141.

Lung compartment analysis assessed from N2 multiple-breath washout in children with cystic fibrosis.

BACKGROUND: Compartment analysis (CA) based on nitrogen multiple-breath washout (N2 MBW) has been shown to allow the assessment of specific volume and ventilation of faster- and slower-ventilating lung compartments of the lung in adults with cystic fibrosis (CF). The aim of this study was to extend previous findings into the pediatric age range. METHODS: Cross-sectional multicenter observational study in children with CF and healthy controls (HC) was done with the assessment of N2 MBW and spirometry. A two-lung compartment model-based analysis (CA) was used to estimate size and function of faster- and slower-ventilating lung compartments from N2 MBW. RESULTS: A total of 125 children with CF and 177 HC, median age 10.8 (range, 2.8-18.9) years, were included in the analysis. CA could be calculated in 66 (53%) children with CF compared with 48 (27%) HC (P < .0001). The proportion of the slower-ventilating lung compartment was significantly smaller in children with CF (53.5%; 95% confidence interval [CI]: 51.9%-55.7%) compared with HC (62.2%; 95% CI: 59.0%-65.0%) The regional specific ventilation of the slower compartment (rVT ,slow/rFRC,slow, %) was significantly lower in children with CF (4.9%; 95% CI: 4.5-5.9) compared with HC (9.7%, 95% CI: 9.2-10.9), and showed inverse correlation to lung clearance index (r2 = -.65; P < .0001), Sacin × VT (r2 = -.36; P = .003) and Scond × VT (r2 = -.51; P < .0001). There was no significant difference in pulmonary parameters between children with CF with and without feasible CA. CONCLUSION: CA is less feasible in children than in adults and correlated to other MBW parameters. The clinical value of CA is still unclear and is yet to be established.

The utility of moment ratios and abbreviated endpoints of the multiple breath washout test in preschool children with cystic fibrosis.

BACKGROUND: The multiple breath washout (MBW) test may be most useful in tracking disease progression over time to inform treatment decisions. In the clinical setting, alternative outcomes, which can be obtained quickly and easily, may facilitate interpretation of clinically relevant changes in lung function. METHODS: In this secondary analysis of data from 78 cystic fibrosis (CF) and 72 healthy control (HC) subjects between the ages of 2.6 and 5.9 years, MBW was performed at enrollment, 1, 3, 6, 9, and 12 months, as well as during symptomatic visits using the Exhalyzer D (EcoMedics AG, Duernten, Switzerland). The lung clearance index, LCI2.5, was compared to moment ratios (M1 /M0 and M2 /M0 ) at the standard cutoff (1/40th of starting tracer gas concentration) as well as LCI5 and moment ratios at 1/20th of the starting concentration (M1 /M0 at LCI5 , and M2 /M0 at LCI5 ). RESULTS: All outcomes were able to distinguish between health and disease. LCI5 reduced testing time by 40% and increased feasibility by more than 10%. The limits of biological reproducibility in healthy children were similar between LCI2.5 (15%), LCI5 (12%), M1 /M0 at LCI2.5 (14%), and M1 /M0 at LCI5 (12%), but markedly larger for M2 /M0 at LCI2.5 (30%) and M2 /M0 at LCI5 (25%). Each outcome deteriorated significantly with worsening pulmonary symptoms, the magnitude of deterioration was greatest for M2 /M0 . CONCLUSIONS: In preschool children with CF, LCI5 was more feasible to obtain and track disease progression. The second moment ratio was most sensitive to pulmonary symptoms, but had the greatest variability both within and between subjects.

Integrating the multiple breath washout test into international multicentre trials.

BACKGROUND: The lung clearance index (LCI), derived from the Multiple Breath Washout (MBW) test, is sensitive to treatment effects and compared with spirometry has higher feasibility in younger children and requires smaller sample sizes. As a result, the LCI has been endorsed by the European CF Society Clinical Trials Network for use as a primary outcome measure in CF clinical trials. METHODS: Here we describe the implementation of standardised protocols for MBW test performance, data collection and quality control to successfully incorporate LCI as a novel outcome measure in a large multicentre phase III clinical trial. RESULTS: Three regional (North America (NA), Europe (EU), Australia (AUS)) central over-reading centres (CORC) were established to provide a collaborative platform for MBW training, certification and quality control of data. One hundred and thirty-two naïve operators from 53 sites across NA, EU and AUS were successfully trained and certified to perform MBW testing.  Incorporation of a re-screening opportunity in the study protocol resulted a final screening feasibility rate of 93%, success remained high throughout the study resulting in an overall feasibility of MBW study data of 88.1% (1107/1257). MBW test acceptability was similar between geographical regions: NA (88%), EU (89%) and AUS (89%). CONCLUSION: With this approach we achieved high MBW test feasibility and sustained collection of good quality data, demonstrating the utility of LCI as an effective primary endpoint in the first international phase III clinical trial to report LCI as the primary outcome.

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 (MBWndd ) in an in vitro lung model, (b) assess the feasibility, repeatability, and reproducibility of MBWndd and (c) compare outcomes with the Exhalyzer D (MBWEM ) 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 FRCndd 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, FRCndd was consistently lower (-19.3% [-40.5; 1.9], 95% CI [-23.9; -14.7]), and showed a volume dependency. LCIndd values were also higher in children with smaller lung volumes. The within-test coefficient of variation of the FRCndd and LCIndd were 4.9% in health, and 5.6% and 6.9% in CF respectively. LCIndd 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, LCIndd was similar to LCIEM in health. CONCLUSIONS: MBWndd measurements are feasible, repeatable, and reproducible, however, MBW-derived outcomes are not interchangeable with MBWEM .

Multiple breath washout in bronchiectasis clinical trials: is it feasible?

BACKGROUND: Evaluation of multiple breath washout (MBW) set-up including staff training, certification and central "over-reading" for data quality control is essential to determine the feasibility of MBW in future bronchiectasis studies. AIMS: To assess the outcomes of a MBW training, certification and central over-reading programme. METHODS: MBW training and certification was conducted in European sites collecting lung clearance index (LCI) data in the BronchUK Clinimetrics and/or i-BEST-1 studies. The blended training programme included the use of an eLearning tool and a 1-day face-to-face session. Sites submitted MBW data to trained central over-readers who determined validity and quality. RESULTS: Thirteen training days were delivered to 56 participants from 22 sites. Of 22 sites, 18 (82%) were MBW naïve. Participant knowledge and confidence increased significantly (p<0.001). By the end of the study recruitment, 15 of 22 sites (68%) had completed certification with a mean (range) time since training of 6.2 (3-14) months. In the BronchUK Clinimetrics study, 468 of 589 (79%) tests met the quality criteria following central over-reading, compared with 137 of 236 (58%) tests in the i-BEST-1 study. CONCLUSIONS: LCI is feasible in a bronchiectasis multicentre clinical trial setting; however, consideration of site experience in terms of training as well as assessment of skill drift and the need for re-training may be important to reduce time to certification and optimise data quality. Longer times to certification, a higher percentage of naïve sites and patients with worse lung function may have contributed to the lower success rate in the i-BEST-1 study.

Effect of changes in tidal volume on multiple breath washout outcomes.

The lung clearance index (LCI), measured by multiple breath washout (MBW), reflects global ventilation inhomogeneity and is a sensitive marker of early obstructive airway disease. For the MBW test to accurately reflect a subject's gas mixing within the lungs, the breathing pattern should represent physiologically appropriate tidal volumes (VT) and respiratory rate (RR). We aimed to assess whether changes in VT impact MBW outcome measures with a series of prospective and retrospective studies. MBW testing was performed using the Exhalyzer ® D (EcoMedics AG, Switzerland). Healthy adult subjects performed MBW with uninstructed tidal breathing and a series of instructed tidal breathing tests, designed to isolate specific features of the breathing pattern. In addition, we retrospectively analyzed MBW data from two pediatric multi-centre interventional studies of cystic fibrosis (CF) subjects to determine the range of VT observed during uninstructed breathing, and whether breathing outside this range impacted results. The LCI was lower, but not significantly different between deep breathing at 20 ml/kg body weight and uninstructed tidal breathing; whereas LCI was significantly higher during shallow breathing compared with normal tidal breathing. For the majority of subjects with CF (80%), VT ranged from 9-15mL/kg. Within the observed VT range, LCI was similar in trials with mean VT /kg below this range compared to trials with VT /kg within the range. If subjects breathe naturally and are not instructed to use specific targets, the range of VT is within physiologically appropriate limits and normal variations observed do not impact MBW outcomes.

Crystal structures of methyl 3,5-di-bromo-4-cyano-benzoate and methyl 3,5-di-bromo-4-iso-cyano-benzoate.

The title crystals, C9H5Br2NO2, are the first reported 2,6-dihalophenyl cyanide-isocyanide pair that have neither three- nor two-dimensional isomorphism. Both crystals contain contacts between the carbonyl O atom and a Br atom. In the crystal of the cyanide, R22(10) inversion dimers form based on C≡N⋯Br contacts, a common packing feature in this series of crystals. In the isocyanide, the corresponding N≡C⋯Br contacts are not observed. Instead, the iso-cyano C atom forms contacts with the meth-oxy C atom. RNC was refined as a two-component pseudo-merohedral twin.