Lung clearance index: clinical and research applications in children

Lung Clearance Index as a Screening Parameter of Pulmonary Impairment in Patients under Immune Checkpoint Therapy: A Pilot Study

Background: Immune checkpoint blockade (ICB) has presented a breakthrough in the treatment of malignant tumors and increased the overall survival of patients with various tumor entities. ICB may also cause immune-related adverse events, such as pneumonitis or interstitial lung disease. The lung clearance index (LCI) is a multiple-breath washout technique offering information on lung pathology in addition to conventional spirometry. It measures the degree of pulmonary ventilation inhomogeneity and allows early detection of pulmonary damage, especially that to peripheral airways. Methods: This cross-sectional study compared the lung function of patients with melanoma or metastatic cutaneous squamous cell carcinoma who received programmed cell death 1 (PD-1) and cytotoxic T-Lymphocyte-associated Protein 4 (CTLA-4) antibodies, alone or in combination, to age- and sex-matched controls. Lung function was assessed using spirometry, according to American Thoracic Society and European Respiratory Society standards, the LCI, and a diffusion capacity of carbon monoxide (DLCO) measurement. Results: Sixty-one screened patients and thirty-eight screened controls led to nineteen successfully included pairs. The LCI in the ICB-treated patients was 8.41 ± 1.15 (mean ± SD), which was 0.32 higher compared to 8.07 ± 1.17 in the control group, but the difference was not significant (p = 0.452). The patients receiving their ICB therapy for under five months showed a significantly lower LCI (7.98 ± 0.77) compared to the ICB patients undergoing therapy for over five months (9.63 ± 1.22) at the point of testing (p = 0.014). Spirometric analysis revealed that the forced expiratory volume between 25 and 75% of the forced vital capacity (FEF25-75%) in the ICB-treated patients was significantly reduced (p = 0.047) compared to the control group. DLCO (%predicted and adjusted for hemoglobin) was 94.4 ± 19.7 in the ICB patients and 93.4 ± 21.7 in the control group (p = 0.734). Conclusions: The patients undergoing ICB therapy showed slightly impaired lung function compared to the controls. Longer periods of ICB treatment led to deterioration of the LCI, which may be a sign of a subclinical inflammatory process. The LCI is feasible and may be easily integrated into the clinical daily routine and could contribute to early detection of pulmonary (auto-)inflammation.

Pulmonary function after lobectomy in children: a systematic review and meta-analysis

BACKGROUND

The influence of lobectomy on pulmonary function in children was still controversial. A systematic review and meta-analysis were essential to explore whether pulmonary function was impaired after lobectomy in children.

METHODS

PubMed, Embase and Web of Science were searched from 1 January 1946 to 1 July 2022. Forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), FEV1/FVC and total lung capacity were extracted from the studies as the primary analysis indicators. Subgroup analyses were performed between the congenital lung malformation (CLM) group and other diseases group, early surgery and late surgery group (1 year old as the dividing line).

RESULTS

A total of 5302 articles were identified through the search strategy; finally, 10 studies met the inclusion criteria. Through the meta-analysis, we found a mild obstructive ventilatory disorder in children who underwent lobectomy. However, a normal pulmonary function could be found in young children with CLM who underwent lobectomy, and the time of operation had no significant influence on their pulmonary function.

CONCLUSIONS

The overall result of pulmonary function after lobectomy in children was good. Surgeons may not need to be excessively concerned about the possibility of lung surgery affecting pulmonary function in children, particularly in patients with CLM.

PROSPERO REGISTRATION NUMBER

CRD42022342243.

Effect of Dornase Alfa on the Lung Clearance Index in Children with Cystic Fibrosis: A Lesson from a Case Series

BACKGROUND

Dornase alfa (DNase) is the only mucus-degrading agent that has proven efficacy in cystic fibrosis (CF). Few studies have evaluated the effects of DNase on the lung clearance index (LCI). We report the experience of two CF centers in which LCI monitoring was used to evaluate the efficacy of DNase therapy.

METHODS

This is a prospective and observational study, evaluating the effects of DNase therapy on LCI values in three CF children followed at CF centers in Florence and Catania, Italy. In both centers, LCI was performed routinely, every 3-6 months, based on the clinical picture and severity of the lung disease. In this study, we evaluated the LCI before and after long-term DNase therapy.

RESULTS

DNase improved LCI values in the absence of respiratory exacerbations: in case n. 1 LCI decreased by 39% in 16 months (from 11.1 to 6.8); in case n. 2 by 20% in 12 months (from 9.3 to 7.4); in case n. 3 by 24% in 16 months (from 9.3 to 7.0).

CONCLUSIONS

This case series confirms the efficacy of DNase therapy in CF children, as demonstrated by the LCI reduction in treated patients. Furthermore, our results suggest that LCI is a sensitive marker of disease and can be used for the evaluation of response to treatment.

Chest X-rays are less sensitive than multiple breath washout examinations when it comes to detecting early cystic fibrosis lung disease

AIM

Annual chest X-ray is recommended as routine surveillance to track cystic fibrosis (CF) lung disease. The aim of this study was to investigate the clinical utility of chest X-rays to track CF lung disease.

METHODS

Children at Gothenburg's CF centre who underwent chest X-rays, multiple breath washouts and chest computed tomography examinations between 1996 and 2016 were included in the study. Chest X-rays were interpreted with Northern Score (NS). We compared NS to lung clearance index (LCI) and structural lung damage measured by computed tomography using a logistic regression model.

RESULTS

A total of 75 children were included over a median period of 13 years (range: 3.0-18.0 years). The proportion of children with abnormal NS was significantly lower than the proportion of abnormal LCI up to the age of 4 years (p < 0.05). A normal NS and a normal LCI at age 6 years were associated with a median (10-90th percentile) total airway disease of 1.8% (0.4-4.7%) and bronchiectasis of 0.2% (0.0-1.5%).

CONCLUSION

Chest X-rays were less sensitive than multiple breath washout examinations to detect early CF lung disease. The combined results from both methods can be used as an indicator to perform chest computed tomography less frequently.

Multiple Breath Washout for Early Assessment of Pulmonary Complications in Patients With Primary Antibody Deficiencies: An Observational Study in Pediatric Age

BACKGROUND

In primary antibody deficiencies (PADs), pulmonary complications are the main cause of morbidity, despite immunoglobulin substitutive therapy, antibiotic treatment of exacerbations, and respiratory physiotherapy. Current Italian recommendations for surveillance of PADs respiratory complications include an annual assessment of spirometry and execution of chest high-resolution computed tomography (HRCT) every 4 years.

OBJECTIVE

This study aimed to evaluate the effectiveness of the lung clearance index (LCI) as an early marker of lung damage in patients with PADs. LCI is measured by multiple breath washout (MBW), a non-invasive and highly specific test widely used in patients with cystic fibrosis (CF).

METHODS

Pediatric patients with PADs (n = 17, 10 male, 7 female, and age range 5-15 years) underwent baseline assessment of lung involvement with chest HRCT, spirometry, and multiple breath nitrogen washout. Among them, 13 patients were followed up to repeat HRCT after 4 years, while performing pulmonary function tests annually. Their baseline and follow-up LCI and forced expiratory volume at 1 s (FEV1) values were compared, taking HRCT as the gold standard, using logistic regression analysis.

RESULTS

Lung clearance index [odds ratio (OR) 2.3 (confidence interval (CI) 0.1-52) at baseline, OR 3.9 (CI 0.2-191) at follow-up] has a stronger discriminating power between altered and normal HRCT rather than FEV1 [OR 0.6 (CI 0.2-2) at baseline, OR 1.6 (CI 0.1-13.6) at follow-up].

CONCLUSION

Within the context of a limited sample size, LCI seems to be more predictive of HRCT alterations than FEV1 and more sensitive than HRCT in detecting non-uniform ventilation in the absence of bronchiectasis. A study of a larger cohort of pediatric patients followed longitudinally in adulthood is needed to challenge these findings.

Long-term respiratory outcomes of post-op congenital lung malformations

BACKGROUND

Congenital lung malformations (CLM) are rare disorders and surgical intervention is the definitive treatment. Our aim is to evaluate the long-term lung function of patients with CLM after surgery compared to healthy children.

METHODS

Sixteen children with CLM (M/F: 9/7) and 30 age-matched, healthy controls (M/F: 13/17) were included in the study. Demographic data were recorded and both groups were compared by spirometry and the nitrogen-based Lung Clearance Index (LCI).

RESULTS

Mean ± SD age of the patients was 12.0 ± 5.4 years. The mean forced expiratory volume in 1 s (FEV₁ ), forced vital capacity (FVC), FEV₁ /FVC, and forced expiratory flow between 25% and 75% of force expiration (FEF_25-75 ) predicted was, 86.68 ± 16.65, 88.00 ± 14.58, 97.44 ± 9.89, and 79.00 ± 26.41, respectively in the patient group. Patients with CLM had significantly lower values in FEV₁ , FVC, FEF_25-75 than healthy controls (P = 0.002, P 0.007, P 0.045). While the mean LCI_2,5% value in patients' group was 8.33 ± 1.52, it was 7.28 ± 0.80 in healthy controls (P = 0.023). Strong inverse correlation between LCI and FEV₁ , FEV₁ /FVC was detected in the patient group (P = 0.023; r: -0.581, P 0.017; r: -0.606 respectively).

CONCLUSION

This study revealed that, in long-term follow-up, patients who had surgery because of CLM have impairment in the pulmonary function compared to healthy children and LCI may be more accurate in detecting airway diseases early than spirometry.

Lung clearance index and diffusion capacity for CO to detect early functional pulmonary impairment in children with rheumatic diseases

BACKGROUND

In adults with rheumatic diseases pulmonary complications are relevant contributors to morbidity and mortality. In these patients diffusion capacity for CO (DLCO) is an established method to detect early pulmonary impairment. Pilot studies using DLCO indicate that early functional pulmonary impairment is present even in children with rheumatic disease albeit not detectable by spirometry and without clinical signs of pulmonary disease. Since the lung clearance index (LCI) is also a non-invasive, feasible and established method to detect early functional pulmonary impairment especially in children and because it requires less cooperation (tidal breathing), we compared LCI versus DLCO (forced breathing and breath-holding manoeuvre) in children with rheumatic diseases.

FINDINGS

Nineteen patients (age 9-17 years) with rheumatic disease and no clinical signs of pulmonary disease successfully completed LCI and DLCO during annual check-up. In 2 patients LCI and DLCO were within physiological limits. By contrast, elevated LCI combined with physiological results for DLCO were seen in 8 patients and in 9 patients both, the LCI and DLCO indicate early functional pulmonary changes. Overall, LCI was more sensitive than DLCO to detect early functional pulmonary impairment (p = 0.0128).

CONCLUSIONS

Our findings suggest that early functional pulmonary impairment is already present in children with rheumatic diseases. LCI is a very feasible and non-invasive alternative for detection of early functional pulmonary impairment in children. It is more sensitive and less cooperation dependent than DLCO. Therefore, we suggest to integrate LCI in routine follow-up of rheumatic diseases in children.

Multiple breath washout quality control in the clinical setting

BACKGROUND

Multiple breath washout (MBW) is increasingly used in the clinical assessment of patients with cystic fibrosis (CF). Guidelines for MBW quality control (QC) were developed primarily for retrospective assessment and central overreading. We assessed whether real-time QC of MBW data during the measurement improves test acceptability in the clinical setting.

METHODS

We implemented standardized real-time QC and reporting of MBW data at the time of the measurement in the clinical pediatric lung function laboratory in Bern, Switzerland, in children with CF aged 4-18 years. We assessed MBW test acceptability before (31 tests; 89 trials) and after (32 tests; 96 trials) implementation of real-time QC and compared agreement between reviewers. Further, we assessed the implementation of real-time QC at a secondary center in Zurich, Switzerland.

RESULTS

Before the implementation of real-time QC in Bern, only 58% of clinical MBW tests were deemed acceptable following retrospective QC by an experienced reviewer. After the implementation of real-time QC, MBW test acceptability improved to 75% in Bern. In Zurich, after the implementation of real-time QC, test acceptability improved from 38% to 70%. Further, the agreement between MBW operators and an experienced reviewer for test acceptability was 84% in Bern and 93% in Zurich.

CONCLUSION

Real-time QC of MBW data at the time of measurement is feasible in the clinical setting and results in improved test acceptability.

Does Pseudomonas aeruginosa Colonization Affect Exercise Capacity in CF?

Introduction

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

Aim

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

Subjects

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

Results

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

Conclusion

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

Lung clearance index: assessment and utility in children with asthma

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

Ventilation efficiency to exercise in patients with cystic fibrosis

INTRODUCTION

Exercise ventilation efficiency index in cardiopulmonary exercise testing (CPET) is elevated in patients with heart failure providing useful information on disease progression and prognosis. Few data, however, exist for ventilation efficiency index among cystic fibrosis (CF) patients.

AIMS

To assess ventilation efficiency index (ΔVE/ΔVCO₂ or V'E/V'CO₂ slope) and intercept of ventilation (VE-intercept) in CF patients with mild, moderate, and severe cystic fibrosis (CF) lung disease. To assess possible correlations with ventilation inhomogeneity and structural damages as seen on high resolution computed tomography (HRCT).

METHODS

CF patients with mild (FEV₁  > 80%, n = 47), moderate (60% < FEV₁  < 80%, n = 21), and severe (FEV₁  < 60%, n = 9) lung disease, mean age 14.9 years participated. Peak oxygen uptake (VO₂ peak), pulmonary ventilation at peak exercise (VE), respiratory equivalent ratios for oxygen and carbon dioxide at peak exercise (VE/VO₂ , VE/VCO₂ ), end-tidal CO₂ (PetCO₂ ), and ΔVE/ΔVCO₂ , ΔVE/ΔVO₂ in a maximal CPET along with spirometry and multiple breath washout indices were examined. HRCT scans were performed and scored using Bhalla score.

RESULTS

Mean ΔVE/ΔVCO₂ showed no significant differences among the three groups (P = .503). Mean VE_int discriminated significantly among the different groups (p ² < 0.001). Ventilation efficiency index did not correlate either with LCI or Bhalla score. However, VE together with ΔVE/ΔVCO₂ slope could predict Bhalla score (r ²  = 0.869, P = .006).

CONCLUSION

No significant differences were found regarding ΔVE/ΔVCO₂ slope levels between the three groups. Ventilation intercept (VE_int ) was elevated significantly as disease progresses reflecting increased dead space ventilation. CF patients retain their ventilation efficiency to exercise even as lung function deteriorates by adopting a higher respiratory rate along with increased dead space ventilation.

Lung Function and Relevant Clinical Factors in Very Low Birth Weight Preterm Infants with Chronic Lung Disease: An Observational Study

Background

Chronic lung disease (CLD), most commonly seen in premature infants who required mechanical ventilation, is associated with functional consequences on lungs and respiratory morbidity. This study aimed to evaluate the lung function of premature infants before discharge and their relevant factors related to the lung function.

Methods

Very low birth weight (VLBW) preterm infants, who required respiratory support soon after birth and were admitted to a hospital in Taiwan, were enrolled. Infants with a need for supplemental oxygen or positive-pressure ventilation support at the postmenstrual age (PMA) of 36 weeks were diagnosed with CLD. Lung function was examined once using EXHALYZER® D before infants were ready for discharge.

Results

Forty-five VLBW preterm infants received the lung function test before discharge, 27 of whom were diagnosed with CLD. The gestational age (p=0.001) and birth weight (p < 0.001) were smaller in the CLD group than in the no-CLD group. Furthermore, infants with CLD required a longer duration of respiratory support (p < 0.001). The postnatal age and PMA were higher and body size was bigger in infants with CLD on lung function measurement. However, lung function was comparable between the groups. The functional residual capacity and tidal volume were associated with body size upon measuring lung function among all VLBW premature infants. FRC was positively correlated with the body length on measuring lung function in those with CLD.

Conclusion

In our study, we showed FRC was positively related to the PMA and body length and tidal volume was positively correlated with the body weight and length on lung function measurement in VLBW preterm infants before discharge. Moreover, FRC was positively correlated with the body length on measuring lung function in those with CLD. The lung volume, ventilation, and respiratory mechanics on discharge were comparable between CLD and no-CLD groups.

Effect of late preterm birth on lung clearance index and respiratory physiology in school-age children

BACKGROUND

We hypothesized that former late preterm (LP) children have abnormal pulmonary physiology parameters, including uneven ventilation distribution, due to premature disruption of normal lung development.

METHODS

A cross-sectional study evaluating former LP children at the age of 6 to 12 years as compared to term controls. Demographics and child's and family history of asthma/atopy/smoking were recorded. The outcome parameters were spirometry, multiple breath washout (MBW) measurement by lung clearance index (LCI), 6-minute walk test (6MWT), symptoms related to asthma and allergy, and Godin Leisure-Time Exercise Questionnaire.

RESULTS

Twenty-nine former LP were compared to 30 term-control children (mean age, 8.2 ± 1.7 and 8.8 ± 1.8 years, respectively). LP had reduced forced expiratory volume in the first second (FEV1) and forced vital capacity (FVC) compared to term controls (FEV1 1.59 ± 0.48 vs 1.80 ± 0.39 L, P = 0.005 and FVC 1.73 ± 0.45 vs 1.99 ± 0.49 L, P = 0.009). There were no differences between the two groups regarding FEV1/FVC, forced expiratory flow between 25 and 75 (FEF25-75), LCI (7.10 ± 0.79 vs 6.96 ± 0.75, P = 0.50), 6MW distance, and weekly leisure-activity score. Former LP children had more episodes of wheezing and greater use of asthma medication.

CONCLUSIONS

This pilot study suggests that LP have lower pulmonary function tests (PFTs) but not ventilation inhomogeneity measured by LCI or functional disturbance. It is unclear if the differences in PFTs are due to late prematurity by itself or are the consequence of maternal and neonatal factors associated with LP. Further larger studies are required to assess the long-term respiratory consequences of LP birth.

Ventilation inhomogeneity is associated with OGTT-derived insulin secretory defects in cystic fibrosis

Progressive deterioration of β-cell function is the main mechanism underlying diabetes in cystic fibrosis (CF). Diabetes negatively impacts the clinical status of CF patients years before its onset. We aimed to evaluate if OGTT-derived indices of β-cell function are associated with early markers of lung disease. We carried out a cross-sectional study on 80 CF patients who performed OGTT, spirometry, and nitrogen-multiple breath washout test. β-cell glucose sensitivity and the insulinogenic indices were used as markers of β-cell function and first-phase insulin response to glucose stimulus. We used sex- and age-adjusted multiple linear regression models to estimate the association between OGTT-derived indices and lung function measures. An increment of β-cell glucose sensitivity equal to its interquartile range was associated with an increase in ppFEV₁ of 7.6 points (95%CI: 0.8; 14.4) as well as with a decrease in LCI of -1.96 units (95%CI: -3.40; -0.51) and in S_cond of -0.016 L^-1 (95%CI: -0.026; -0.007). The corresponding figures for insulinogenic index were: 8.6 (95%CI: 3.4; 13.9) for ppFEV₁ , -2.03 (95%CI: -3.13; -0.94) for LCI, and -0.014 L^-1 (95%CI: -0.021; -0.071) for S_cond . When adjusting also for 2-h plasma glucose, both β-cell glucose sensitivity and insulinogenic index remained inversely associated with S_cond . Deterioration of β-cell function is related to early lung disease in young patients with mild to normal pulmonary function. This relationship is independent from hyperglycemia and mainly involves conductive airways.

[Lung clearance index in cystic fibrosis]

INTRODUCTION

Small airways' involvement in cystic fibrosis (CF) pulmonary disease is a very early event, which can progress sub-clinically and insidiously since it is poorly reflected by commonly used lung function tests.

STATE OF ART

Sensitive and discriminative tools are available to investigate small airways function. However their complexity and/or invasiveness has confined their use to research purposes and to some specialized research teams. By contrast, the multiple breath washout (MBW) test is more affordable and non-invasive. Lung clearance index (LCI), which is the most used derived parameter, is reproducible and much more sensitive than spirometry in detecting small airways disease. However, MBW is operator dependent.

PERSPECTIVES

The recent commercialization of devices assessing LCI launches MBW as a potential tool in routine clinical care, although its use currently remains mostly dedicated to research purposes. However, important differences in LCI between various equipment settings raise a number of theoretical questions. Specific algorithms should be refined and more transparent. Standardization of MBW is still an ongoing process. Whether other MBW derived indices can prove superior over LCI deserves further study.

CONCLUSIONS

In CF, LCI is now a well-established outcome in research settings to detect early lung function abnormalities and new treatment effects, especially in patients with mild lung disease. In these patients, LCI seems an attractive tool for clinicians too. Yet, further investigation is needed to define clinically significant changes in LCI and to which extent this index can be useful in guiding clinical decisions remains to be studied.

Novel approach to computerized breath detection in lung function diagnostics

BACKGROUND

Breath detection, i.e. its precise delineation in time is a crucial step in lung function data analysis as obtaining any clinically relevant index is based on the proper localization of breath ends. Current threshold or smoothing algorithms suffer from severe inaccuracy in cases of suboptimal data quality. Especially in infants, the precise analysis is of utmost importance. The key objective of our work is to design an algorithm for accurate breath detection in severely distorted data.

METHODS

Flow and gas concentration data from multiple breath washout test were the input information. Based on universal physiological characteristics of the respiratory tract we designed an algorithm for breath detection. Its accuracy was tested on severely distorted data from 19 patients with different types of breathing disorders. Its performance was compared to the performance of currently used algorithms and to the breath counts estimated by human experts.

RESULTS

The novel algorithm outperformed the threshold algorithms with respect to their accuracy and had similar performance to human experts. It proved to be a highly robust and efficient approach in severely distorted data. This was demonstrated on patients with different pulmonary disorders.

CONCLUSION

Our newly proposed algorithm is highly robust and universal. It works accurately even on severely distorted data, where the other tested algorithms failed. It does not require any pre-set thresholds or other patient-specific inputs. Consequently, it may be used with a broad spectrum of patients. It has the potential to replace current approaches to the breath detection in pulmonary function diagnostics.

Small airway function in children with mild to moderate asthmatic symptoms

BACKGROUND

Clinical significance of small airway obstruction in mild pediatric asthma is unclear.

OBJECTIVE

To evaluate small airway properties in children with mild to moderate asthmatic symptoms and the association of small airway function with asthma control and exercise-induced bronchoconstriction (EIB).

METHODS

Children (5-10 years old) with recurrent wheezing (n = 42) or persistent troublesome cough (n = 16) and healthy controls (n = 19) performed impulse oscillometry (IOS), spirometry, and a multiple-breath nitrogen washout (MBNW) test. Exhaled nitric oxide (NO) was measured at multiple flow rates to determine alveolar NO concentration (Calv). Asthma control was evaluated with the Childhood Asthma Control Test (C-ACT), short-acting β₂-agonist (SABA) use within the past month, and asthma exacerbations within the past year.

RESULTS

IOS, spirometry, and exhaled NO indexes that are related to small airway function differed between children with recurrent wheezing and healthy controls, whereas only forced expiratory flow at 25% to 75% of the forced vital capacity was associated with persistent cough. The MBNW indexes showed no difference between the groups. Among symptomatic children, conducting airway ventilation inhomogeneity and Calv were associated with asthma exacerbations (P = .03 and P = .002, respectively), and lung clearance index and Calv were associated with EIB (P = .04 and P = .004, respectively). None of the proposed small airway indexes was associated with the C-ACT score or SABA use.

CONCLUSION

Subtle changes were observed in the proposed small airway indexes of IOS, spirometry, and exhaled NO among children with mild to moderate recurrent wheezing. Small airway dysfunction, expressed as ventilation inhomogeneity indexes and Calv, was also associated with asthma exacerbations and EIB.

Pathogenesis, imaging and clinical characteristics of CF and non-CF bronchiectasis

Bronchiectasis is a common feature of severe inherited and acquired pulmonary disease conditions. Among inherited diseases, cystic fibrosis (CF) is the major disorder associated with bronchiectasis, while acquired conditions frequently featuring bronchiectasis include post-infective bronchiectasis and chronic obstructive pulmonary disease (COPD). Mechanistically, bronchiectasis is driven by a complex interplay of inflammation and infection with neutrophilic inflammation playing a predominant role. The clinical characterization and management of bronchiectasis should involve a precise diagnostic workup, tailored therapeutic strategies and pulmonary imaging that has become an essential tool for the diagnosis and follow-up of bronchiectasis. Prospective future studies are required to optimize the diagnostic and therapeutic management of bronchiectasis, particularly in heterogeneous non-CF bronchiectasis populations.

Technological strategies to estimate and control diffusive passage times through the mucus barrier in mucosal drug delivery

In mucosal drug delivery, two design goals are desirable: 1) insure drug passage through the mucosal barrier to the epithelium prior to drug removal from the respective organ via mucus clearance; and 2) design carrier particles to achieve a prescribed arrival time and drug uptake schedule at the epithelium. Both goals are achievable if one can control "one-sided" diffusive passage times of drug carrier particles: from deposition at the mucus interface, through the mucosal barrier, to the epithelium. The passage time distribution must be, with high confidence, shorter than the timescales of mucus clearance to maximize drug uptake. For 100nm and smaller drug-loaded nanoparticulates, as well as pure drug powders or drug solutions, diffusion is normal (i.e., Brownian) and rapid, easily passing through the mucosal barrier prior to clearance. Major challenges in quantitative control over mucosal drug delivery lie with larger drug-loaded nanoparticulates that are comparable to or larger than the pores within the mucus gel network, for which diffusion is not simple Brownian motion and typically much less rapid; in these scenarios, a timescale competition ensues between particle passage through the mucus barrier and mucus clearance from the organ. In the lung, as a primary example, coordinated cilia and air drag continuously transport mucus toward the trachea, where mucus and trapped cargo are swallowed into the digestive tract. Mucus clearance times in lung airways range from minutes to hours or significantly longer depending on deposition in the upper, middle, lower airways and on lung health, giving a wide time window for drug-loaded particle design to achieve controlled delivery to the epithelium. We review the physical and chemical factors (of both particles and mucus) that dictate particle diffusion in mucus, and the technological strategies (theoretical and experimental) required to achieve the design goals. First we describe an idealized scenario - a homogeneous viscous fluid of uniform depth with a particle undergoing passive normal diffusion - where the theory of Brownian motion affords the ability to rigorously specify particle size distributions to meet a prescribed, one-sided, diffusive passage time distribution. Furthermore, we describe how the theory of Brownian motion provides the scaling of one-sided diffusive passage times with respect to mucus viscosity and layer depth, and under reasonable caveats, one can also prescribe passage time scaling due to heterogeneity in viscosity and layer depth. Small-molecule drugs and muco-inert, drug-loaded carrier particles 100nm and smaller fall into this class of rigorously controllable passage times for drug delivery. Second we describe the prevalent scenarios in which drug-loaded carrier particles in mucus violate simple Brownian motion, instead exhibiting anomalous sub-diffusion, for which all theoretical control over diffusive passage times is lost, and experiments are prohibitive if not impossible to measure one-sided passage times. We then discuss strategies to overcome these roadblocks, requiring new particle-tracking experiments and emerging advances in theory and computation of anomalous, sub-diffusive processes that are necessary to predict and control one-sided particle passage times from deposition at the mucosal interface to epithelial uptake. We highlight progress to date, remaining hurdles, and prospects for achieving the two design goals for 200nm and larger, drug-loaded, non-dissolving, nanoparticulates.

Lung clearance index (LCI) as a predictor of exercise limitation among CF patients

INTRODUCTION

FEV₁ is often considered the gold standard to monitor lung disease in cystic fibrosis (CF). Recently, there has been increasing interest in multiple breath washout (MBW) and cardiopulmonary exercise testing (CPET) as alternative or even more sensitive techniques. However, limited data exist on associations among the above methods.

AIM

To evaluate the correlations between outcome measures of MBW and CPET and to examine if ventilation inhomogeneity can predict exercise intolerance.

SUBJECTS AND METHODS

Ninety-seven children and adults with CF (47 males, mean [range] age 14.9 (6.6; 26.7) years, mean FEV₁ : 90.8% predicted, mean lung clearance index [LCI]: 11.4, and mean peak oxygen uptake [VO₂ peak]: 82.4% predicted) performed spirometry, MBW, and CPET on the same day during their admission or outpatient visit.

RESULTS

LCI, m₁ /m₀ , and m₂ /m₀ (P < 0.001) as well as VO₂ peak%, breathing reserve (BR), minute ventilation (VE)/VO₂ (P < 0.001), and VE/carbon dioxide release (VCO₂ ) (P = 0.006) correlated significantly with FEV₁ %. LCI, m₁ /m₀ , and m₂ /m₀ correlated with VO₂ peak (P ≤ 0.001), VE (L/min) (P < 0.05), BR (P < 0.01), VE/VO₂ (P < 0.001), and VE/VCO₂ (P < 0.01). Multiple regression analysis showed that LCI could predict BR% (P < 0.001, r² :0.272) and VE/VO₂ (P < 0.001, r² : 0.207) while LCI and FRC could predict VO₂ peak% P < 0.001, r² : 0.216) and VE/VCO₂ (P < 0.001, r² : 0.226).

CONCLUSION

Ventilation inhomogeneity as indicated by increased LCI is associated with less efficient ventilation during strenuous exercise and negatively impacts exercise capacity in CF.

Lung Clearance Index and Quantitative Computed Tomography of Post-Infectious Bronchiolitis Obliterans in Infants

Post-infectious bronchiolitis obliterans (BO) could be diagnosed via spirometry and chest computed tomography (CT); however, these tests are limited in infants. We aimed to evaluate the utility of lung clearance index (LCI) and air-trapping lung volume from chest CT in infants. This prospective study included 20 infants (mean age, 10.9 ± 6.3 months) diagnosed with post-infectious BO between 2009 and 2016. All subjects underwent multiple breath washout tests. For quantitative analysis of chest CT, the mean lung area attenuation value was used as an individual cutoff to determine the air-trapping lung volume. The mean cutoff lung attenuation value was −659 Hounsfield units, the mean total lung volume was 265 ml, and the mean air-trapping lung volume percentage was 22.9%. Functional residual capacity correlated with total lung volume and normal attenuation lung volume (p < 0.02). LCI (p < 0.02) and moment ratio (MR) 1 (p < 0.05) correlated with the air-trapping lung volume percentage. The concordance indices of LCI (0.659, p = 0.025) and MR1 (0.642, p = 0.046) were significantly correlated with the air-trapping lung volume percentage from CT. LCI and quantitative air-trapping lung volume from chest CT are feasible, complimentary tools for assessing infants with post-infectious BO.

Respiratory Difficulties in Children With Underlying Asthma During Immunotherapy for High-risk Neuroblastoma

Treatment of high-risk neuroblastoma now includes antibody based antitumor immunotherapy as part of standard care. Although this therapy has resulted in dramatic improvements in survival, it is associated with significant side effects. Children with underlying respiratory issues, and in particular asthma, may be more susceptible to immunotherapy associated respiratory compromise and pulmonary complications. Early routine involvement of pulmonology care is warranted for these patients in an effort to allow maximal delivery of immunotherapy and minimize acute and long-term complications.

Inter-test reproducibility of the lung clearance index measured by multiple breath washout

The lung clearance index (LCI) has strong intra-test repeatability; however, the inter-test reproducibility of the LCI is poorly defined.

The aim of the present study was to define a physiologically meaningful change in LCI in preschool children, which discriminates changes associated with disease progression from biological variability.

Repeated LCI measurements from a longitudinal cohort study of children with cystic fibrosis and age-matched controls were collected to define the inter-visit reproducibility of the LCI. Absolute change, the coefficient of variation, Bland–Altman limits of agreement, the coefficient of repeatability, intra-class correlation coefficient, and percentage changes were calculated.

LCI measurements (n=505) from 71 healthy and 77 cystic fibrosis participants (aged 2.6–6 years) were analysed. LCI variability was proportional to its magnitude, such that reproducibility defined by absolute changes is biased. A physiologically relevant change for quarterly LCI measurements in health was defined as exceeding ±15%. In clinically stable cystic fibrosis participants, the threshold was higher (±25%); however, for measurements made 24 h apart, the threshold was similar to that observed in health (±17%).

A percentage change in LCI greater than ±15% in preschool children can be considered physiologically relevant and greater than the biological variability of the test.

Biological variability of lung clearance index is dependent on magnitude; % change is better for tracking patientshttp://ow.ly/tgbX30dBbCX

Developments in multiple breath washout testing in children with cystic fibrosis

BACKGROUND

Lung clearance index (LCI) is becoming recognized as an important addition in the monitoring of pediatric cystic fibrosis (CF). The non-invasive technique is easy to perform in all ages, reproducible and increasingly being used in clinical trials. There is interest in utilizing it within the clinic setting but its current use is mostly as a research tool. The procedure is highly dependent on skilled operators and a relaxed testing environment is key to obtaining good quality measurements.

CONCLUSIONS

Standardization of LCI is part of an ongoing collaborative, multicenter process. This review describes the background to LCI, discusses technical issues and limitations and provides examples of its utility in clinical and research contexts.

A new infant hybrid respiratory simulator: preliminary evaluation based on clinical data

A new hybrid (numerical-physical) simulator of the respiratory system, designed to simulate spontaneous and artificial/assisted ventilation of preterm and full-term infants underwent preliminary evaluation. A numerical, seven-compartmental model of the respiratory system mechanics allows the operator to simulate global and peripheral obstruction and restriction of the lungs. The physical part of the simulator is a piston-based construction of impedance transformer. LabVIEW real-time software coordinates the work of both parts of the simulator and its interaction with a ventilator. Using clinical data, five groups of "artificial infants" were examined: healthy full-term infants, very low-birth-weight preterm infants successfully (VLBW) and unsuccessfully extubated (VLBWun) and extremely low-birth-weight preterm infants without (ELBW) and with bronchopulmonary dysplasia (ELBW_BPD). Pressure-controlled ventilation was simulated to measure peak inspiratory pressure, mean airway pressure, total (patient + endotracheal tube) airway resistance (R), total dynamic compliance of the respiratory system (C), and total work of breathing by the ventilator (WOB). The differences between simulation and clinical parameters were not significant. High correlation coefficients between both types of data were obtained for R, C, and WOB (γ _R  = 0.99, P < 0.0005; γ _C  = 0.85, P < 0.005; γ_WOB = 0.96, P < 0.05, respectively). Thus, the simulator accurately reproduces infant respiratory system mechanics.

Functional residual capacity and lung clearance index in infants treated for esophageal atresia and tracheoesophageal fistula

BACKGROUND

Newborn babies with esophageal atresia/tracheoesophageal fistula (EA/TEF) are prone to respiratory tract disorders. Functional residual capacity (FRC) and lung clearance index (LCI) are commonly considered useful and sensitive tools to investigate lung function and early detecting airways diseases. The aim of the present study is to report the first series of EA/TEF infants prospectively evaluated for FRC and LCI.

METHODS

Prospective observational cohort study of all patients treated for EA/TEF. Lung volume and ventilation inhomogeneity were measured by helium gas dilution technique using an ultrasonic flow meter. Babies were studied both in assisted controlled ventilation (sedated) and in spontaneous breathing (quiet sleep). Three consecutive FRC and LCI measurements were collected for each test at three different time points: before surgery (T0), 24hours after surgery (T1) and after extubation (T2).

RESULTS

16 EA newborns were eligible for the study between December 2011 and July 2013. Three were excluded because of technical problems. At T0 FRC values were in the normal range regardless the presence of TEF but worsened afterwards at T1, with a subsequent recovering after extubation; a significant improvement after surgery was observed concerning LCI while no differences were found in tidal volume.

CONCLUSION

Helium gas dilution technique is a suitable method to measure the effect of surgery on lung physiology, even in ventilated infants with EA. The changes observed could be related to the ventilatory management and lung compression during surgical procedure.

The reproducibility and responsiveness of the lung clearance index in bronchiectasis

Lung clearance index (LCI) is a potential clinical outcome marker in bronchiectasis. Its responsiveness to therapeutic intervention has not been determined. This study evaluates its responsiveness to a session of physiotherapy and intravenous antibiotic treatment of an exacerbation.

32 stable and 32 exacerbating bronchiectasis patients and 26 healthy controls were recruited. Patients had LCI and lung function performed before and after physiotherapy on two separate occasions in the stable patients and at the beginning and end of an intravenous antibiotic course in the exacerbating patients.

LCI was reproducible between visits in 25 stable patients, with an intraclass correlation of 0.978 (0.948, 0.991; p<0.001). There was no significant difference in LCI (mean±sd) between stable 11.91±3.39 and exacerbating patients 12.76±3.47, but LCI was significantly higher in both bronchiectasis groups compared with healthy controls (7.36±0.99) (p<0.001). Forced expiratory volume in 1 s improved after physiotherapy, as did alveolar volume after intravenous antibiotics, but LCI did not change significantly.

LCI is reproducible in stable bronchiectasis but unlike conventional lung function tests, is unresponsive to two short-term interventions and hence is unlikely to be a useful clinical tool for short-term acute assessment in these patients. Further evaluation is required to establish its role in milder disease and in the evaluation of long-term interventions.

Novel outcome measures for clinical trials in cystic fibrosis

Cystic fibrosis (CF) is a common inherited condition caused by mutations in the gene encoding the CF transmembrane regulator protein. With increased understanding of the molecular mechanisms underlying CF and the development of new therapies there comes the need to develop new outcome measures to assess the disease, its progression and response to treatment. As there are limitations to the current endpoints accepted for regulatory purposes, a workshop to discuss novel endpoints for clinical trials in CF was held in Anaheim, California in November 2011. The pros and cons of novel outcome measures with potential utility for evaluation of novel treatments in CF were critically evaluated. The highlights of the 2011 workshop and subsequent advances in technologies and techniques that could be used to inform the development of clinical trial endpoints are summarized in this review. Pediatr Pulmonol. © 2014 The Authors. Pediatric Pulmonology published by Wiley Periodicals, Inc.

How to avoid misinterpreting lung function tests in children: a few practical tips

Assessments of pulmonary function play an integral part in the clinical management of school age children as well as providing objective outcome measures in clinical and epidemiological research studies. Pulmonary function tests (PFTs) can also be undertaken in sleeping infants and in awake young children from 3 years of age. However, the clinical utility of such assessments, which are generally confined to specialist centres, has yet to be established. Whether requesting or undertaking paediatric PFTs, or simply reading about how these tests have been applied in research studies, it is essential to question whether results have been interpreted in a meaningful way. This review summarises some of the issues that need to be considered, including: why the tests are being performed; which tests are most likely to detect the suspected pathophysiology; how often such tests should be repeated; whether results are likely to be reliable (in terms of data quality, repeatability and the availability of suitable reference equations with which to distinguish the effects of disease from those of growth and development), and whether the selected tests are likely to be feasible in the individual child or study group under investigation.

Pulmonary function testing in children and infants

Pulmonary function testing is performed in children and infants with the aim of documenting lung development with age and making diagnoses of lung diseases. In children and infants with an established lung disease, pulmonary function is tested to assess the disease progression and the efficacy of therapy. It is difficult to carry out the measurements in this age group without disturbances, so obtaining results of good quality and reproducibility is challenging. Young children are often uncooperative during the examinations. This is partly related to their young age but also due to the long testing duration and the unpopular equipment. We address a variety of examination techniques for lung function assessment in children and infants in this review. We describe the measuring principles, examination procedures, clinical findings and their interpretation, as well as advantages and limitations of these methods. The comparability between devices and centres as well as the availability of reference values are still considered a challenge in many of these techniques. In recent years, new technologies have emerged allowing the assessment of lung function not only on the global level but also on the regional level. This opens new possibilities for detecting regional lung function heterogeneity that might lead to a better understanding of respiratory pathophysiology in children.

Lung clearance index: evidence for use in clinical trials in cystic fibrosis

The ECFS-CTN Standardisation Committee has undertaken this review of lung clearance index as part of the group's work on evaluation of clinical endpoints with regard to their use in multicentre clinical trials in CF. The aims were 1) to review the literature on reliability, validity and responsiveness of LCI in patients with CF, 2) to gain consensus of the group on feasibility of LCI and 3) to gain consensus on answers to key questions regarding the promotion of LCI to surrogate endpoint status. It was concluded that LCI has an attractive feasibility and clinimetric properties profile and is particularly indicated for multicentre trials in young children with CF and patients with early or mild CF lung disease. This is the first article to collate the literature in this manner and support the use of LCI in clinical trials in CF.

Lungenfunktionsdiagnostik

Lungenfunktionsdiagnostik beinhaltet eine Vielzahl von Messmethoden, mit denen jeweils bestimmte Qualitten der Lungen in verschiedenen Altersgruppen überwiegend nichtinvasiv untersucht werden können.

The impact of newborn screening and earlier intervention on the clinical course of cystic fibrosis

Cystic fibrosis is a life-limiting condition which is readily diagnosed in the vast majority of cases on newborn screening [NBS]. A diagnosis made on newborn screening translates into earlier initiation of therapies, improved growth, better lung function into the adult years and culminates in better survival.