Multiple breath washout: measuring early manifestations of lung pathology

Assessing Pulmonary Function in Children and Adolescents After Cancer Treatment: Protocol for a Multicenter Cohort Study (Swiss Childhood Cancer Survivor Study FollowUp-Pulmo)

BACKGROUND

Childhood cancer survivors (CCS) are at risk of pulmonary dysfunction due to cancer treatments, but evidence on prevalence and risk factors remains limited. Most previous studies had small sample sizes or retrospective study designs, little information about treatments, or a lack of standardization of pulmonary function tests (PFTs) or limited their investigation to certain PFTs. Since spirometry mainly assesses the large airways but cancer therapy also affects peripheral airways, additional functional tests are needed. The nitrogen multiple breath washout test (N2MBW) is sensitive to peripheral airway damage in other patient populations, but its benefit in CCS is unknown. Therefore, comprehensive and standardized evaluation of pulmonary function after cancer treatment in childhood, using different PFTs that include N2MBW, is needed to address these knowledge gaps and provide insights into possible early stages of pulmonary dysfunction.

OBJECTIVE

In the Swiss Childhood Cancer Survivor Study (SCCSS) FollowUp-Pulmo, we will comprehensively assess lung function in children and adolescents after treatment for cancer to identify risk factors for pulmonary dysfunction, assess the ability of N2MBW to detect pulmonary dysfunction compared to other PFTs, and investigate the association of functional outcomes from PFTs with self-reported respiratory symptoms.

METHODS

SCCSS FollowUp-Pulmo is a prospective multicenter longitudinal cohort study embedded in routine clinical care that enrolls CCS aged 6-20 years for whom at least 1 year has passed since a childhood cancer diagnosis, who have completed treatment, and who attend regular pediatric oncological follow-up care. Inclusion criteria comprise any of the following: systemic anticancer treatment (chemotherapy, immunotherapy, or targeted agents), thoracic surgery, thoracic radiotherapy, or hematopoietic stem cell transplantation (HSCT). CCS undergo a standardized pulmonary assessment, including spirometry, body plethysmography, diffusing capacity of the lung for carbon monoxide (DLCO), and N2MBW, and complete a questionnaire on respiratory symptoms and lifestyle. Data from previous and subsequent routine care PFTs will be included in this study.

RESULTS

Recruitment started in June 2022 at the University Children's Hospital Bern, Switzerland. Subsequently, patient recruitment expanded to the University Children's Hospitals in Basel and Geneva, Switzerland. By October 2024, we had invited 220 patients, of which 201 have already participated in this study, resulting in a response rate of 91%. Their median age at the time of the study was 14 years (IQR 10-17), and the median time since diagnosis was 7 years (IQR 4-10). The study will continuously enroll new CCS.

CONCLUSIONS

This study will contribute to a comprehensive understanding of pulmonary function in CCS and assess related risk factors, as well as the utility of N2MBW compared to other PFTs. The results will assist in the development of more targeted screening and risk-stratified follow-up care.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04732273; https://clinicaltrials.gov/study/NCT04732273.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/69743.

Global Lung Function Initiative reference values for multiple breath washout indices

BACKGROUND

Multiple breath washout is a lung function test based on tidal breathing that assesses lung volume and ventilation distribution. The aim of this analysis was to use the Global Lung Function Initiative methodology to develop all-age reference equations for the multiple breath washout indices lung clearance index (LCI) and functional residual capacity (FRC).

METHODS

Multiple breath washout data from healthy individuals were collated from sites. Data were re-analysed using the latest software versions. Reference equations were derived using the lambda-mu-sigma method using the generalised additive models of location shape and scale programme in R. The impact of equipment type, inert tracer gas and equipment dead space volume on the derived reference ranges were investigated.

RESULTS

Data from 23 sites (n=3647 test occasions) were submitted. Reference equations were derived from 1579 unique observations from participants between the ages of 2 and 81 years. Equipment type, inert tracer gas and equipment dead space volume did not significantly affect the prediction equations for either LCI or FRC. Reference equations for LCI include age as the only predictor, whereas sex-specific reference equations for FRC included height and age.

CONCLUSIONS

Global Lung Function Initiative reference equations for multiple breath washout variables provide a standard for reporting and interpretation of LCI and FRC.

Ventilation heterogeneity is increased in adults exposed to coal mine fire-related PM2.5

BACKGROUND AND OBJECTIVES

The Hazelwood Health Study was set up to study long-term health effects of a mine fire that blanketed residents of the Latrobe Valley with smoke for 45 days in 2014. The Respiratory Stream specifically assessed the impact of fine particulate matter <2.5 μm diameter (PM2.5) exposure from mine fire smoke on lung health. The multiple breath nitrogen washout (MBW) test assesses ventilation heterogeneity, which may detect sub-clinical airways dysfunction not identified using standard tests such as spirometry. This analysis assessed the association of PM2.5 exposure with measures of ventilation heterogeneity.

METHODS

Exposed (Morwell) and unexposed (Sale) participants were recruited 3.5-4 years after the fire from those who had participated in an Adult Survey. MBW was performed to measure lung clearance index (LCI), functional residual capacity (FRC), acinar (Sacin) and conductive (Scond) ventilation heterogeneity. PM2.5 exposure was estimated with emission and chemical transport models. Multivariable linear regression models were fitted controlling for confounders.

RESULTS

We recruited 519 participants. MBW tests were conducted on 504 participants with 479 acceptable test results (40% male; 313 exposed, 166 unexposed). Exposure to mine fire-related PM2.5 was associated with increasing Scond (β = 1.57/kL, 95%CI: 0.20-2.95, p = 0.025), which was comparable to the estimated effect on Scond of 4.7 years of aging. No other MBW outcomes were statistically different.

CONCLUSION

Increasing exposure to PM2.5 was associated with increased ventilation heterogeneity in the conductive region of the lungs 4 years after the event.

Sensitive outcome measures to detect the association between PM2.5 and lung function impairment

See related article

Small airways disease in chronic obstructive pulmonary disease

INTRODUCTION

Small airway disease (SAD) represents a common and critical feature of Chronic Obstructive Pulmonary Disease (COPD). Introduced in the '60s, SAD has gradually gained increasing interest as assessment methodologies have improved. Chronic exposure to smoking and noxious particles or gases induces inflammation and remodeling, leading to airway obstruction and SAD, eventually resulting in complete airway loss.

AREAS COVERED

A literature search up to June 2024 was performed in PubMed to identify articles on SAD and airway diseases mainly COPD, but also to the extent that it seemed relevant in the uncontrolled/severe asthma field, where SAD is better studied. We provide clinicians and translational scientists with a comprehensive analysis of the existing literature on SAD in COPD, concentrating on the underlying pathophysiological mechanisms, diagnostic techniques, and current pharmacological approaches targeting airflow obstruction in small airways.

EXPERT OPINION

Small airways are the primary site for the onset and progression of airflow obstruction in patients with COPD, with significant clinical consequences associated with poor lung function, hyperinflation, and impaired quality of life. The early identification of individuals with subclinical SAD may allow us to prevent its further progress from airway loss and potential development of emphysema and choose the appropriate therapeutic approach.

Flexible bronchoscopy in pediatric lung transplantation

Pediatric lung transplantation represents a treatment option for children with advanced lung disease or pulmonary vascular disorders who are deemed an appropriate candidate. Pediatric flexible bronchoscopy is an important and evolving field that is highly relevant in the pediatric lung transplant population. It is thus important to advance our knowledge to better understand how care for children after lung transplant can be maximally optimized using pediatric bronchoscopy. Our goals are to continually improve procedural skills when performing bronchoscopy and to decrease the complication rate while acquiring adequate samples for diagnostic evaluation. Attainment of these goals is critical since allograft assessment by bronchoscopic biopsy is required for histological diagnosis of acute cellular rejection and is an important contributor to establishing chronic lung allograft dysfunction, a common complication after lung transplant. Flexible bronchoscopy with bronchoalveolar lavage and transbronchial lung biopsy plays a key role in lung transplant graft assessment. In this article, we discuss the application of bronchoscopy in pediatric lung transplant evaluation including historical approaches, our experience, and future directions not only in bronchoscopy but also in the evolving pediatric lung transplantation field. Pediatric flexible bronchoscopy has become a vital modality for diagnosing lung transplant complications in children as well as assessing therapeutic responses. Herein, we review the value of flexible bronchoscopy in the management of children after lung transplant and discuss the application of novel techniques to improve care for this complex pediatric patient population and we provide a brief update about new diagnostic techniques applied in the growing lung transplantation field.

Cell Therapy Transplant Canada (CTTC) Consensus-Based Guideline 2024 for Management and Treatment of Chronic Graft-Versus-Host Disease and Future Directions for Development

This is a consensus-based Canadian guideline whose primary purpose is to standardize and facilitate the management of chronic graft-versus-host disease (cGvHD) across the country. Creating uniform healthcare guidance in Canada is a challenge for a number of reasons including the differences in healthcare authority structure, funding and access to healthcare resources between provinces and territories, as well as the geographic size. These differences can lead to variable and unequal access to effective therapies for GvHD. This document will provide comprehensive and practical guidance that can be applied across Canada by healthcare professionals caring for patients with cGvHD. Hopefully, this guideline, based on input from GvHD treaters across the country, will aid in standardizing cGvHD care and facilitate access to much-needed novel therapies. This consensus paper aims to discuss the optimal approach to the initial assessment of cGvHD, review the severity scoring and global grading system, discuss systemic and topical treatments, as well as supportive therapies, and propose a therapeutic algorithm for frontline and subsequent lines of cGvHD treatment in adults and pediatric patients. Finally, we will make suggestions about the future direction of cGvHD treatment development such as (1) a mode-of-action-based cGvHD drug selection, according to the pathogenesis of cGvHD, (2) a combination strategy with the introduction of newer targeted drugs, (3) a steroid-free regimen, particularly for front line therapy for cGvHD treatment, and (4) a pre-emptive approach which can prevent the progression of cGvHD in high-risk patients destined to develop severe and highly morbid forms of cGvHD.

Respiratory function after 30+ years following sulfur mustard exposure in survivors in Sweden

Background

Sulfur mustard (SM) exposure causes acute and chronic respiratory diseases. The extent of small airway dysfunction (SAD) in individuals exposed to SM is unclear. This study evaluated and compared SAD in SM-exposed and SM-unexposed participants using noninvasive lung function tests assessing small airway function.

Methods

This retrospective cohort study involved SM-exposed (n = 15, mean age: 53 ± 8 years) and SM-unexposed (n = 15, mean age: 53 ± 7 years) Kurdish-Swedish individuals in Sweden. Small airway resistance and reactance were assessed using impulse oscillometry (IOS). Nitrogen (N2) multiple breath washout (MBW) was employed to assess lung ventilation heterogeneity. The gas-exchanging capacity of the lungs was assessed using the diffusing capacity of the lungs for the carbon monoxide (DLCO) test. Lung function outcomes were reported as absolute values and z-scores. Group comparisons were performed using the Mann-Whitney U test.

Results

No statistically significant differences in age, height, or body mass index were observed between the two groups. IOS showed significantly increased small airway resistance, while N2MBW exhibited significantly increased global and acinar ventilation heterogeneity in SM-exposed individuals compared to that in unexposed individuals. SAD was identified in 14 of 15 SM-exposed individuals, defined as at least one abnormal IOS difference between resistance at 5 and 20 Hz (R5-R20) and/or area of reactance (AX) or N2MBW lung's acinar zone (Sacin), and DLCO adjusted to the alveolar volume (DLCO/VA) outcome. Of these 14 individuals, only 5 demonstrated concordant findings across the IOS and N2MBW tests.

Conclusion

Exposure to SM was positively associated with long-term impairment of respiratory tract function in the small airways in the majority of the previously SM-exposed individuals in the present study. Furthermore, both IOS and N2MBW should be employed to detect SAD in SM-exposed survivors as they provide complementary information. Identifying and characterizing the remaining pathology of the small airways in survivors of SM exposure is a first step toward improved treatment and follow-up.

Lung Function Tests in Infants and Children

Lung function testing is an essential modality of investigation in children as it provides objective evidence of lung disease/health. With advances in technology, various tests are available that can aid in the diagnosis of lung disease, assess the progression and response to therapy and document the lung development and evolving lung diseases in infants. This narrative review discusses lung function tests in infants and children. Currently, lung function tests can be performed in every age group, from neonates to the elderly. Spirometry and peak expiratory flow rate (PEFR) are the most employed tests in children more than six years of age. Spirometry helps diagnose and monitoring of both obstructive and restrictive diseases. There is a need for expertise to perform and interpret spirometry correctly. The forced oscillation technique (FOT) or impulse oscillometry (IOS) is done with tidal volume breathing and is feasible even in preschool children. Their utility is mainly restricted to asthma in children at present. Lung function tests can be performed in neonates, infants and children using infant pulmonary function test (PFT) equipment, although their availability is limited. Diffusion capacity for carbon monoxide (DLCO) is a valuable tool in restrictive lung diseases. Lung volumes can be assessed by body plethysmography and multiple washout technique. The latter can also assess lung clearance index. It is essential to perform and interpret the lung function test results correctly and correlate them with the clinical condition for optimum treatment and outcome.

Lung clearance index in children with cystic fibrosis previously diagnosed with CRMS/CFSPID: A monocentric prospective experience

INTRODUCTION

No data are available on the values and role of lung clearance index (LCI) in cystic fibrosis (CF) Screen Positive Inconclusive Diagnosis (CFSPID) progressed to CF diagnosis (CFSPID > CF). This study aimed to assess the value of the LCI in correctly predicting the progression of CFSPID to CF.

METHODS

This is a prospective study carried out at the CF Regional Center of Florence, Italy from September 1, 2019. We compared LCI values in children with CF diagnosed for positive newborn screening (NBS), CFSPID or CFSPID > CF for pathological sweat chloride (SC). The Exhalyzer-D (EcoMedics AG, Duernten, Switzerland, software version 3.3.1) was used to conduct the LCI tests, every 6 months on stable children.

RESULTS

Forty-two cooperating children were enrolled (mean age at LCI tests: 5.4 years, range: 2.7-8.7): 26 (62%) had CF, 8 (19%) were CFSPID > CF for positive SC, while 8 (19%) kept the CFSPID label at last LCI test. The mean LCI value for patients with CF (7.39; 5.98-10.24) was statistically higher compared to both the mean LCI in the CFSPID > CF (6.62; 5.69-7.58) and in CFSPID (6.56; 5.64-7.21).

CONCLUSIONS

Most of asymptomatic CFSPID or progressed to CF have normal LCI. Further data on the longitudinal course of LCI during follow up of CFSPID and on larger cohorts is needed.

Acute Rejection and Chronic Lung Allograft Dysfunction: Obstructive and Restrictive Allograft Dysfunction

Lung transplantation is an established treatment of well-selected patients with end-stage respiratory diseases. However, lung transplant recipients have the highest rates of acute and chronic rejection among transplanted solid organs. Owing to ongoing alloimmune recognition and associated immune-driven airway/vascular remodeling, precipitated by multifactorial, endogenous or exogenous, post-transplant injuries to the bronchovascular axis of the secondary pulmonary lobule, most lung transplant recipients will suffer from a pathophysiological decline of their allograft, either functionally and/or structurally. This review discusses current knowledge, barriers, and gaps in acute cellular rejection and chronic lung allograft dysfunction-the greatest impediment to long-term post-transplant survival.

In children with primary ciliary dyskinesia, which type of lung function test is the earliest determinant of decline in lung health: A systematic review

BACKGROUND

Primary ciliary dyskinesia is a rare genetic disorder characterized by recurrent sinopulmonary infections and worsening obstructive lung disease. Kidney and brain involvement is less common and is associated with overlapping ciliopathies/syndromes. The lungs are impacted early in the course of the disease, so it is vital to monitor lung function and recognize any decline by doing appropriate lung function tests. This systematic review compares different lung function tests and analyzes which one becomes abnormal earlier in the disease.

METHODS

A systematic review was conducted following the methodology in the "Cochrane Handbook on Systematic Reviews for diagnostic tests." The Preferred Reporting Items for Systematic Review and Meta-Analyses were used to report the results. The risk of bias assessment was done using "The Cochrane Handbook for Systematic Reviews tool for interventional studies." A meta-analysis was not performed due to the small sample size. All studies were analyzed by using Joanna Briggs Institute's critical appraisal tool.

RESULTS

After screening for the duplication of results and applying inclusion and exclusion criteria, 14 studies were assessed by reading the full texts. Out of these, eight were finally included in this systematic review. The total sample size from all studies was 165, including 80 males. All the studies used spirometry as a lung function test, whereas multiple breath washout was used in five studies. Other tests used for comparison were computed tomography (CT), magnetic resonance imaging (MRI), cardiopulmonary exercise testing, 6-min walk test, DLCO, maximal inspiratory pressure, maximal expiratory pressure, and PaO₂ . Lung clearance index (LCI) by multiple breath washout had a stronger association with the structural changes on CT/MRI than spirometry indices like forced expiratory volume in 1 s (FEV1) and forced expiratory flow at 25% to 75% of lung volume (FEF 25-75).

CONCLUSIONS

Based on the evidence from this systematic review, LCI becomes abnormal earlier than FEV1 or FEF 25-75 and positively correlates with the findings on high-resolution CT. It has limitations like the lack of reference values and a complex technique to perform the test.

Model analysis of multiple breath nitrogen washout data: robustness to variations in breathing pattern

We recently developed a model-based method for analyzing multiple breath nitrogen washout data that does not require identification of Phase-III. In the present study, we assessed the effect of irregular breathing patterns on the intra-subject variabilities of the model parameters. Nitrogen fraction at the mouth was measured in 18 healthy and 20 asthmatic subjects during triplicate performances of multiple breath nitrogen washout, during controlled (target tidal volume 1 L at 8-12 breaths per minute) and free (unrestricted) breathing. The parameters S_cond, S_acin and functional residual capacity (FRC) were obtained by conventional analysis of the slope of Phase-III. Fitting the model to the washout data provided functional residual capacity (FRC_M), dead space volume (V_D), the coefficient of variation of regional specific ventilation ([Formula: see text]), and the model equivalent of S_acin (S_acin-M). Intra-participant coefficients of variation for the model parameters for both health and asthma were FRC_M < 5.2%, V_D < 5.4%, [Formula: see text] < 9.0%, and S_acin-M < 45.6% for controlled breathing, and FRC_M < 4.6%, V_D < 5.3%, [Formula: see text] < 13.2%, and S_acin-M < 103.2% for free breathing. The coefficients of variation limits for conventional parameters were FRC < 6.1%, with S_cond < 73.6% and S_acin < 49.2% for controlled breathing and S_cond < 35.0% and S_acin < 74.4% for free breathing. The model-fitting approach to multiple breath nitrogen washout analysis provides a measure of regional ventilation heterogeneity in [Formula: see text] that is less affected by irregularities in the breathing pattern than its corresponding Phase-III slope analysis parameter S_cond.

Multiple-Breath Washout Outcome Measures in Adults with Bronchiectasis

Rationale: Lung clearance index (LCI) has good intravisit repeatability with better sensitivity in detecting lung disease on computed tomography scan compared with forced expiratory volume in 1 second (FEV₁) in adults with bronchiectasis. Alternative multiple-breath washout parameters have not been systematically studied in bronchiectasis. Objectives: To determine the validity, repeatability, sensitivity, specificity, and feasibility of standard LCI (LCI^2.5), shortened LCI (LCI^5.0), ventilation heterogeneity arising within proximal conducting airways (S_condVT), and ventilation heterogeneity arising within the acinar airways (S_acinVT) in a cross-sectional observational cohort of adults with bronchiectasis. Methods: Cross-sectional multiple-breath nitrogen washout data (Exhalyzer D; Eco Medics AG) from 132 patients with bronchiectasis across five United Kingdom centers (BronchUK Clinimetrics study) and 88 healthy control subjects were analyzed. Results: Within-test repeatability (mean coefficient of variation) was <5% for both LCI^2.5 and LCI^5.0 in patients with bronchiectasis, and there was no difference in mean coefficient of variation for LCI^2.5 and LCI^5.0 in patients with bronchiectasis compared with healthy volunteers. Moderate-strength correlations were seen between FEV₁ and LCI^2.5 (r = -0.54), LCI^5.0 (r = -0.53), S_condVT (r = -0.35), and S_acinVT (r = -0.38) z-scores. The proportion of subjects with abnormal multiple-breath washout (z-score > 2) but in normal FEV₁ (z-score < -2) was 42% (LCI^2.5) and 36% (LCI^5.0). Overall results from the receiver operating characteristic curve analysis indicated that LCI^2.5 had the greatest combined sensitivity and specificity to discriminate between bronchiectasis and control subjects, followed by LCI^5.0, FEV₁, and S_condVT z-scores. There was a 57% time saving with LCI^5.0. Conclusions: LCI^2.5 and LCI^5.0 had good within-test repeatability and superior sensitivity compared with spirometry measures in differentiating between health and bronchiectasis disease. LCI^5.0 is quicker and more feasible than LCI^2.5. Clinical trial registered with www.clinicaltrials.gov (NCT02468271).

Respiratory Follow Up of the Premature Neonates-Rationale and Practical Issues

The aim of the review was to present the state of knowledge about the respiratory pathology in former premature neonates (children that were born preterm-before 37 weeks of gestation-and are examined and evaluated after 40 weeks corrected age) other than chronic lung disease, in order to provide reasons for a respiratory follow-up program for this category of patients. After a search of the current evidence, we found that premature infants are prone to long-term respiratory consequences due to several reasons: development of the lung outside of the uterus, leading to dysmaturation of the structures, pulmonary pathology due to immaturity, infectious agents or mechanical ventilation and deficient control of breathing. The medium- to long-term respiratory consequences of being born before term are represented by an increased risk of respiratory infections (especially viral) during the first years of life, a risk of recurrent wheezing and asthma and a decrease in pulmonary volumes and airway flows. Late preterm infants have risks of pulmonary long-term consequences similar to other former premature infants. Due to all the above risks, premature neonates should be followed in an organized fashion, being examined at regular time intervals from discharge from the maternity hospital until adulthood-this could lead to an early detection of the risks and preventive therapies in order to improve their prognosis and assure a normal and productive life. The difficulties related to establishing such programs are represented by the insufficient standardization of the data gathering forms, clinical examinations and lung function tests, but it is our belief that if more premature infants are followed, the experience will allow standards to be established in these fields and the methods of data gathering and evaluation to be unified.