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

Short-term effects of positive expiratory pressure mask on ventilation inhomogeneity in children with cystic fibrosis: A randomized, sham-controlled crossover study

BACKGROUND

Can physiotherapy with a positive expiratory pressure (PEP) mask improve peripheral ventilation inhomogeneity, a typical feature of children with cystic fibrosis (cwCF)? To answer this question, we used the nitrogen multiple-breath washout (N2MBW) test to measure diffusion-convection-dependent inhomogeneity arising within the intracinar compartment (Sacin*VT).

METHODS

For this randomized, sham-controlled crossover trial, two N2MBW tests were performed near the hospital discharge date: one before and the other after PEP mask therapy (1 min of breathing through a flow-dependent PEP device attached to a face mask, followed by three huffs and one cough repeated 10 times) by either a standard (10-15 cmH20) or a sham (<5 cmH20) procedure on two consecutive mornings. Deception entailed misinforming the subjects about the nature of the study; also the N2MBW operators were blinded to treatment allocation. Study outcomes were assessed with mixed-effect models.

RESULTS

The study sample was 19 cwCF (ten girls), aged 11.4 (2.7) years. The adjusted Sacin*VT mean difference between the standard and the sham procedure was -0.015 (90% confidence interval [CI]: -∞ to 0.025) L-1. There was no statistically significant difference in Scond*VT and lung clearance index between the two procedures: -0.005 (95% CI: -0.019 to 0.01) L-1 and 0.49 (95% CI: -0.05 to 1.03) turnovers, respectively.

CONCLUSION

Our findings do not support evidence for an immediate effect of PEP mask physiotherapy on Sacin*VT with pressure range 10-15 cmH20. Measurement with the N2MBW and the crossover design were found to be time-consuming and unsuitable for a short-term study of airway clearance techniques.

Isolated abnormal FEF75% detects unsuspected bronchiolar obstruction in CF children

BACKGROUND

Physiologic detection of bronchiolar obstruction in children with cystic fibrosis (CF) may be clinically unsuspected because of normal routine spirometry despite bronchiectasis on lung CT.

METHODS

Children from two accredited CF facilities had spirometry obtained every 3 months when clinically stable. Pre-bronchodilator maximum expiratory flow volume curves were retrospectively analyzed over 16 years to detect an isolated abnormal FEF75%, despite normal routine spirometry.

RESULTS

At Miller Children's and Women's Hospital (MCWH), an abnormal FEF75% was initially detected in 26 CF children at age 7.5 ± 4 (SD) years despite normal routine spirometry initially. FEF75% remained an isolated abnormality for 2.5 ± 1.5 years after it was initially detected in these 26 CF children. At Cohen Children's Medical Center (CCMC), despite normal routine spirometry initially, abnormal FEF75% occurred in 13 children at age 11.7 ± 4.5 years, and abnormal FEF25-75% in 10 children at age 11.8 ± 5.3 years.

CONCLUSIONS

FEF75% was most sensitive spirometric test for diagnosing both early and isolated progressive bronchiolar obstruction. Data from CCMC in older children demonstrated the simultaneous detection of abnormal FEF75% and FEF25-75% values consistent with greater bronchiolar obstruction when serial spirometry was initiated at an older age.

IMPACT

There is very little published spirometric data regarding diagnosis of isolated small airways obstruction in CF children. FEF75% can easily detect unsuspected small airways obstruction in CF children with normal routine spirometry and bronchiectasis on lung CT and optimize targeted modulatory therapies.

Pulmonary Function Tests in the Evaluation of Early Lung Disease in Cystic Fibrosis

BACKGROUND

Properly evaluating respiratory system dysfunction is essential in children with cystic fibrosis (CF). This prospective study aimed to assess the course of early lung disease based on multiple breath nitrogen washout (MBNW), impulse oscillometry (IOS), and conventional techniques, such as spirometry and body plethysmography.

METHODS

Over a 2 year recruitment period, subjects with CF aged 7-18 performed pulmonary function tests (PFTs). Moreover, the nutritional and microbiological status, frequency of pulmonary exacerbations (PExs), and patients' health-related quality of life (HRQoL) were assessed.

RESULTS

The mean age of the children (n = 69) was 14.09 ± 3.26 years; F/M 37/32. Spirometry-based diagnoses of normal lung function (forced expiratory volume in 1 s, FEV₁ ≥ 90%pred), mild (FEV₁ 70-89%pred) and moderate (FEV₁ 40-69%pred) lung diseases were established in 34 (49.3%), 25 (36.2%), and 10 (14.5%) patients, respectively. An elevated lung clearance index (LCI > 6.98) was observed in 85% of the subjects with normal FEV₁. The presence of Pseudomonas aeruginosa infection (n = 16) and the number of PExs treated with IV antibiotics were associated with significantly worse PFT results.

CONCLUSIONS

MBNW and IOS are more helpful tools than conventional techniques in assessing early lung disease in CF. LCI is a more useful parameter for detecting functional abnormalities than FEV₁ in school-age children.

Evaluation of clinically relevant changes in the lung clearance index in children with cystic fibrosis and healthy controls

BACKGROUND

The limits of reproducibility of the lung clearance index (LCI) are higher in children with cystic fibrosis (CF) compared with healthy children, and it is currently unclear what defines a clinically meaningful change.

METHODS

In a prospective multisite observational study of children with CF and healthy controls (HCs), we measured LCI, FEV₁% predicted and symptom scores at quarterly visits over 2 years. Two reviewers performed a detailed review of visits to evaluate the frequency that between visit LCI changes outside ±10%, ±15%, ±20% represented a clinically relevant signal. In the setting of acute respiratory symptoms, we used a generalised estimating equation model, with a logit link function to determine the ability of LCI worsening at different thresholds to predict failure of lung function recovery at follow-up.

RESULTS

Clinically relevant LCI changes outside ±10%, ±15% and ±20% were observed at 25.7%, 15.0% and 8.3% of CF visits (n=744), respectively. The proportions of LCI changes categorised as noise, reflecting biological variability, were comparable between CF and HC at the 10% (CF 9.9% vs HC 13.0%), 15% (CF 4.3% vs HC 3.1%) and 20% (CF 2.4% vs HC 1.0%) thresholds. Compared with symptomatic CF visits without a worsening in LCI, events with ≥10% LCI increase were more likely to fail to recover baseline LCI at follow-up.

CONCLUSION

The limits of reproducibility of the LCI in healthy children can be used to detect clinically relevant changes and thus inform clinical care in children with CF.

Variability of clinically measured lung clearance index in children with cystic fibrosis

RATIONALE

The lung clearance index (LCI) is increasingly being used in the clinical surveillance of patients with cystic fibrosis (CF). However, there are limited data on long-term variability and physiologically relevant changes in LCI during routine clinical surveillance.

OBJECTIVES

To evaluate the long-term variability of LCI and propose a threshold for a physiologically relevant change.

METHODS

In children aged 4-18 years with CF, LCI was measured every 3 months as part of routine clinical surveillance during 2011-2020 in two centers. The variability of LCI during periods of clinical stability was assessed using mixed-effects models and was used to identify thresholds for physiologically relevant changes.

RESULTS

Repeated LCI measurements of acceptable quality (N = 858) were available in 100 patients with CF; for 74 patients, 399 visits at clinical stability were available. The variability of repeated LCI measurements over time expressed as the coefficient of variation (CV%) was 7.4%. The upper limit of normal (ULN) for relative changes in LCI between visits was 19%.

CONCLUSION

We report the variability of LCI in children and adolescents with CF during routine clinical surveillance. According to our data, a change in LCI beyond 19% may be considered physiologically relevant. These findings will help guide clinical decisions according to LCI changes.

Pulmonary exacerbations, airway pathogens, and long-term course of lung clearance index in children and young adults with cystic fibrosis

BACKGROUND

Pulmonary exacerbations (PEx), pathogens colonizing the respiratory tract, and patients' age are associated with progressive worsening of lung function among patients with cystic fibrosis (CF). However, the effect of these factors on longitudinal changes of Lung Clearance Index (LCI) remains unclear.

AIM

To assess the role of age, different types of bronchial infection, and PEx on LCI deterioration.

METHODS

We conducted a retrospective study assessing multiple-breath washout (MBW) and spirometry changes among CF patients evaluated at quarterly outpatient clinic visits over 8 years. MBW and spirometry were performed at each visit, sputum samples and/or cough swabs were obtained for culture, whereas respiratory symptoms and clinical examination findings were recorded. Patients who had ≥5 serial MBW measurements, one of which coincided with a pulmonary exacerbation, were reviewed.

RESULTS

Seventy-six patients were included in the study: mean age of 10.61 years (range 1.75-23.75). A total of 1152 MBW tests and 1047 spirometry tests were performed. LCI was significantly higher among CF patients aged 11-15, 16-20, and over 20 years than those under 5 years of age; ΔLCI: 1.16 (confidence interval [CI] 0.43-1.90) and 3.25 (CI 2.33-4.17), respectively. Furthermore, LCI was significantly elevated in CF patients with positive cultures for Pseudomonas aeruginosa (0.52 LCI [CI -0.12 to 0.71]) and Stenotrophomonas Maltophilia (1.41 LCI [CI 0.61-2.21]). Moreover, increased values of LCI in CF patients were significantly associated with increased risk of PEx (odds ratio [OR] 1.19, CI [1.14-1.25], p < 0.001).

CONCLUSION

LCI demonstrates a progression of lung disease and corresponds to changes in bacterial infections and PEx among patients with CF. LCI may be a valuable marker for tracking disease deterioration and may have a role in the routine clinical care of patients with CF.

Estimating the minimum sample size for interventional and observational studies using the lung clearance index as an endpoint✰

BACKGROUND

With the increasing availability of highly effective modulators for people living with cystic fibrosis (CF), there is a need to re-design research studies to reflect the changing epidemiology of the CF population. The lung clearance index (LCI), a sensitive physiological measure of lung function, may be ideally suited as an endpoint in the era of CF modulator therapies. In this study we describe study design considerations for implementing LCI into interventional and observational research.

METHODS

Simulations were used to estimate the required sample size to detect a range of treatment effects for interventional studies (including cross-over trials) and to track lung disease progression in observational studies.

RESULTS

Using published treatment effects to inform the design of prospective studies can lead to inefficient study designs. Large improvements in LCI for a few individuals can skew results and can influence interpretations of treatment effects. Adjusting for baseline LCI can help to improve the efficiency of a study. Compared to the forced expiratory volume in 1 second (FEV₁), analysis using LCI as an endpoint requires as little as one third of the total sample size.

CONCLUSIONS

Planning of prospective studies that include LCI as an endpoint need to consider baseline LCI and disease severity of the study population; whereas interpretation of results needs to consider whether a few individuals skew the overall treatment effect.

Comparative analysis of respiratory symptom scores to detect acute respiratory events in children with cystic fibrosis

BACKGROUND

Patient-reported outcomes (PROs) are important outcome measures in research and clinical practice. This study describes the longitudinal variability the Cystic Fibrosis Questionnaire-Revised (CFQ-R) Respiratory score and the Chronic Respiratory Infection Symptom Score (CRISS), as well as their ability to identify acute respiratory events in children with CF.

METHODS

In this prospective observational study, the parent-proxy (6 -13 years) and self-reported (6-18 years) CFQ-R Respiratory score and CRISS (6-18 years) were measured every 3 months over 2 years. The lung clearance index (LCI) and FEV₁ were also measured. We compared the diagnostic accuracy of the PROs in distinguishing acute respiratory events and clinically stable visits, using the minimal important difference of each PRO as the threshold.

RESULTS

A total of 98 children with CF were included. On average, the symptom scores did not change between clinically stable visits. The positive predictive value (PPV) and negative predictive value (NPV) of a ≥8.5-point worsening in the parent-proxy CFQ-R score to identify acute respiratory events (n=119) (PPV 70.2% and NPV 87.0%) were higher than for the self-reported CFQ-R score (PPV 58.9% and NPV 72.2%). The PPV and NPV of an ≥11-point change in the CRISS for acute respiratory events (n=137) was 56.5% and 79.6%, respectively. The PPV and NPV of all PROs were increased when combined with the LCI and/or FEV₁pp.

CONCLUSION

Symptoms scores differ in their ability to identify acute respiratory events in children with CF; PPV and NPV of all PROs were improved when combined with lung function outcomes.

ERS International Congress 2021: highlights from the Paediatric Assembly

In this review, Early Career Members of the European Respiratory Society (ERS) and the Chairs of the ERS Assembly 7: Paediatrics present the highlights in paediatric respiratory medicine from the ERS International Congress 2021. The eight scientific Groups of this Assembly cover respiratory physiology and sleep, asthma and allergy, cystic fibrosis (CF), respiratory infection and immunology, neonatology and intensive care, respiratory epidemiology, bronchology, and lung and airway development. We here describe new developments in lung function testing and sleep-disordered breathing diagnosis, early life exposures affecting pulmonary function in children and effect of COVID-19 on sleep and lung function. In paediatric asthma, we present the important role of the exposome in asthma development, and how biologics can provide better outcomes. We discuss new methods to assess distal airways in children with CF, as some details remain blind when using the lung clearance index. Moreover, we summarise the new ERS guidelines for bronchiectasis management in children and adolescents. We present interventions to reduce morbidity and monitor pulmonary function in newborns at risk of bronchopulmonary dysplasia and long-term chronic respiratory morbidity of this disease. In respiratory epidemiology, we characterise primary ciliary dyskinesia, identify early life determinants of respiratory health and describe the effect of COVID-19 preventive measures on respiratory symptoms. Also, we describe the epidemiology of interstitial lung diseases, possible consequences of tracheomalacia and a classification of diffuse alveolar haemorrhage in children. Finally, we highlight that the characterisation of genes and pathways involved in the development of a disease is essential to identify new biomarkers and therapeutic targets.

Clinical utility of preoperative pulmonary function testing in pediatrics

Perioperative respiratory adverse events pose a significant risk in pediatric anesthesia, and identifying these risks is vital. Traditionally, this is assessed using history and examination. However, the perioperative risk is multifactorial, and children with complex medical backgrounds such as chronic lung disease or obesity may benefit from additional objective preoperative pulmonary function tests. This article summarizes the utility of available pulmonary function assessment tools as preoperative tests in improving post-anesthetic outcomes. Currently, there is no evidence to support or discourage any pulmonary function assessment as a routine preoperative test for children undergoing anesthesia. In addition, there is uncertainty about which patients with the known or suspected respiratory disease require preoperative pulmonary function tests, what time period prior to surgery these are required, and whether spirometry or more sophisticated tests are indicated. Therefore, the need for any test should be based on information obtained from the history and examination, the child's age, and the complexity of the surgery.

Multiple breath washout: measuring early manifestations of lung pathology

The multiple breath washout (MBW) test measures the efficiency of gas mixing in the lungs and has gained significant interest over the past 20 years. MBW outcomes detect early lung function impairment and peripheral airway pathology, through its main outcome measure lung clearance index (LCI). LCI measures the number of lung turnovers required to washout an inert tracer gas. MBW is performed during normal (tidal) breathing, making it particularly suitable for young children or those who have trouble performing forced manoeuvres. Additionally, research in chronic respiratory disease populations has shown that MBW can detect acute clinically relevant changes before conventional lung function tests, such as spirometry, thus enabling early intervention. The development of technical standards for MBW and commercial devices have allowed MBW to be implemented in clinical research and potentially routine clinical practice. Although studies have summarised clinimetric properties of MBW indices, additional research is required to establish the clinical utility of MBW and, if possible, shorten testing time. Sensitive, feasible measures of early lung function decline will play an important role in early intervention for people living with respiratory diseases.

Educational aim

To describe the multiple breath washout test, its applications to lung pathology and respiratory disease, as well as directions for future research.

Management of respiratory tract exacerbations in people with cystic fibrosis: Focus on imaging

Respiratory tract exacerbations play a crucial role in progressive lung damage of people with cystic fibrosis, representing a major determinant in the loss of functional lung tissue, quality of life and patient survival. Detection and monitoring of respiratory tract exacerbations are challenging for clinicians, since under- and over-treatment convey several risks for the patient. Although various diagnostic and monitoring tools are available, their implementation is hampered by the current definition of respiratory tract exacerbation, which lacks objective "cut-offs" for clinical and lung function parameters. In particular, the latter shows a large variability, making the current 10% change in spirometry outcomes an unreliable threshold to detect exacerbation. Moreover, spirometry cannot be reliably performed in preschool children and new emerging tools, such as the forced oscillation technique, are still complementary and need more validation. Therefore, lung imaging is a key in providing respiratory tract exacerbation-related structural and functional information. However, imaging encompasses several diagnostic options, each with different advantages and limitations; for instance, conventional chest radiography, the most used radiological technique, may lack sensitivity and specificity in respiratory tract exacerbations diagnosis. Other methods, including computed tomography, positron emission tomography and magnetic resonance imaging, are limited by either radiation safety issues or the need for anesthesia in uncooperative patients. Finally, lung ultrasound has been proposed as a safe bedside option but it is highly operator-dependent and there is no strong evidence of its possible use during respiratory tract exacerbation. This review summarizes the clinical challenges of respiratory tract exacerbations in patients with cystic fibrosis with a special focus on imaging. Firstly, the definition of respiratory tract exacerbation is examined, while diagnostic and monitoring tools are briefly described to set the scene. This is followed by advantages and disadvantages of each imaging technique, concluding with a diagnostic imaging algorithm for disease monitoring during respiratory tract exacerbation in the cystic fibrosis patient.

Lung Clearance Index in Children with Cystic Fibrosis during Pulmonary Exacerbation

(1) Background: Pulmonary exacerbation (PEx) is one of the main factors affecting the quality of life and life expectancy in patients with cystic fibrosis (CF). Our study aimed to evaluate the change in selected pulmonary function parameters, including lung clearance index (LCI), in patients with CF diagnosed with PEx. (2) Methods: We enrolled 40 children with CF aged 6–17. They performed spirometry and multiple breath nitrogen washout (MBNW) tests during a stable condition period at the beginning and the end of intravenous antibiotic treatment. (3) Results: LCI increased by 65% and FEV₁ decreased by ≥10% in 40% of patients with CF during PEx. An absolute change in LCI between a stable condition period and PEx was 1.05 (±1.92) units, which corresponds to a relative change of 11.48% (±18.61) of the baseline. The relative decrease in FEV₁ was −9.22% (±12.00) and the z-score was −0.67 (±1.13). After the PEx treatment, FEV₁ increased by 11.05% (±9.04) on average, whereas LCI decreased by 1.21 ± 1.59 units on average, which represented 9.42% ± 11.40 compared to the value at the beginning of PEx. (4) Conclusions: The change in LCI captures a higher proportion of events with functional impairment than FEV₁ in school-age children with CF.

Longitudinal assessment of lung clearance index to monitor disease progression in children and adults with cystic fibrosis

Background

Lung clearance index (LCI) is a valuable research tool in cystic fibrosis (CF) but clinical application has been limited by technical challenges and uncertainty about how to interpret longitudinal change. In order to help inform clinical practice, this study aimed to assess feasibility, repeatability and longitudinal LCI change in children and adults with CF with predominantly mild baseline disease.

Methods

Prospective, 3-year, multicentre, observational study of repeated LCI measurement at time of clinical review in patients with CF >5 years, delivered using a rapid wash-in system.

Results

112 patients completed at least one LCI assessment and 98 (90%) were still under follow-up at study end. The median (IQR) age was 14.7 (8.6–22.2) years and the mean (SD) FEV₁ z-score was −1.2 (1.3). Of 81 subjects with normal FEV₁ (>−2 z-scores), 63% had raised LCI (indicating worse lung function). For repeat stable measurements within 6 months, the mean (limits of agreement) change in LCI was 0.9% (−18.8% to 20.7%). A latent class growth model analysis identified four discrete clusters with high accuracy, differentiated by baseline LCI and FEV₁. Baseline LCI was the strongest factor associated with longitudinal change. The median total test time was under 19 min.

Conclusions

Most patients with CF with well-preserved lung function show stable LCI over time. Cluster behaviours can be identified and baseline LCI is a risk factor for future progression. These results support the use of LCI in clinical practice in identifying patients at risk of lung function decline.