Lung clearance index is elevated in young children with symptom-controlled asthma

A Pilot Study of Lung Clearance Index as a Useful Outcome Marker in the Follow-Up of Pediatric Patients with Non-Cystic Fibrosis Bronchiectasis?

The forced expiratory volume in one second (FEV1) is regularly used for the follow-up of patients with non-cystic fibrosis bronchiectasis (nCF-BE). The lung clearance index (LCI), measured by the multiple breath washout test, has been recently proposed as a lung function measure and a potential tool more sensitive than the FEV1 measured by spirometry in assessing airway changes seen on imaging. While several data have been endorsed as a useful endpoint in clinical trials of patients with early or mild CF lung disease and as the main outcome measure in clinical trials with CFTR modulators in children and adolescents with CF, few data are available in the context of non-CF bronchiectasis. The aim of this pilot study was to compare the LCI with the FEV1 as well as the forced vital capacity (FVC), the forced expiratory flow at 25-75% of the FVC (FEF 25-75%), and chest imaging based on the modified Reiff score in patients with primary ciliary dyskinesia (PCD) and non-CF, non-PCD bronchiectasis (PCD-BE and nCFnPCD-BE). Additionally, we compared each test's duration and the preferred technique. Twenty children were included; nine had PCD-BE and eleven had nCFnPCD-BE. The median age was twelve years (ages ranging between five and eighteen years). The median LCI was seven while the median z-scores of the FEV1, FVC, and FEF 25-75% were -0.6, 0, and -0.9, respectively. No significant associations or correlations were observed between LCI, spirometric parameters, or the modified Reiff score. However, nearly half of the population (n = 9) had an abnormal LCI, while only 10% had an abnormal FEV1. A total of 75% of children preferred MBW, despite it lasting five times longer than spirometry. In this paper, the authors suggest that LCI might be useful in a cohort of pediatric patients with PCD-BE and nCFnPCD-BE for detecting early lung function changes during their follow-up. Additionally, MBW seems to be preferred by patients. These data may encourage further studies on this topic.

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.

Lung clearance index predicts persistence of preschool wheeze

BACKGROUND

The lung clearance index (LCI) is a measure of pulmonary function. Variable feasibility (50->80%) in preschool children has been reported. There are limited studies exploring its relationship to respiratory symptoms and how it predicts persistent wheeze. We aimed to assess the association with respiratory symptoms in preschool-aged children with LCI and determine its utility in predicting persistent wheeze.

METHODS

LCI was measured in a subcohort of the CHILD Cohort Study at age 3 years using SF₆  multiple breath washout test mass spectrometry. Respiratory symptom phenotypes at age 3 were derived from children's respiratory symptoms reported by their parents. Responses were used to categorize children into 4 symptom groups: recurrent wheeze (3RW), recurrent cough (3RC), infrequent symptoms (IS), and no current symptoms (NCS). At age 5 years, these children were seen by a specialist clinician and assessed for persistent wheeze (PW).

RESULTS

At age 3 years, 69% (234/340) had feasible LCI. Excluding two children with missing data, 232 participants were categorized as follows: 33 (14%) 3RW; 28 (12%) 3RC; 17 (7%) IS; and 154 (66%) NCS. LCI z-score at age 3 years was highest in children with 3RW compared to 3RC (mean (SD): 1.14 (1.56) vs. 0.09 (0.95), p < .01), IS (mean (SD): -0.14 (0.59), p < .01), and NCS (mean (SD): -0.08 (1.06), p < .01). LCI z-score at age 3 was predictive of persistent wheeze at age 5 (PW) (AUROC: 0.87).

CONCLUSIONS

LCI at age 3 was strongly associated with recurrent wheeze at age 3, and predictive of its persistence to age 5.

Peripheral airways involvement in children with asthma exacerbation

Objective

The literature provides some evidence of peripheral airways key role in the pathogenesis of asthma. However, the extent to which lung periphery including acinar zone contribute to asthma activity and control in pediatric population is unclear. Therefore, the aim of the study was to estimate peripheral airways involvement in children with asthma exacerbation and stable asthma simultaneously via different pulmonary function tests.

Methods

Children with asthma exacerbation (n = 20) and stable asthma (n = 22) performed spirometry, body plethysmography, exhaled nitric oxide, impulse oscillometry (IOS), and multiple‐breath washout (MBW).

Results

Peripheral airway's function indexes were increased in children with asthma, particularly in group with asthma exacerbation when compared with stable asthma group. The prevalence of abnormal results was significantly higher in asthma exacerbation. All children with asthma exacerbation had conductive ventilation inhomogeneity; 76% had acinar ventilation inhomogeneity. According to IOS measurements, resistance and reactance were within normal range, but other IOS parameters were significantly higher in children with asthma exacerbation compared with stable asthma group. The 36% of children with acute asthma had air trapping.

Conclusion

Significant involvement of peripheral airways was observed in children with asthma, particularly in asthma exacerbation, which determine lung periphery as important additional target for therapy and provide new insights into pathophysiological process of pediatric asthma.

Cord blood group 2 innate lymphoid cells are associated with lung function at 6 weeks of age

Objective

Offspring born to mothers with asthma in pregnancy are known to have lower lung function which tracks with age. Human group 2 innate lymphoid cells (ILC2) accumulate in foetal lungs, at 10‐fold higher levels compared to adult lungs. However, there are no data on foetal ILC2 numbers and the association with respiratory health outcomes such as lung function in early life. We aimed to investigate cord blood immune cell populations from babies born to mothers with asthma in pregnancy.

Methods

Cord blood from babies born to asthmatic mothers was collected, and cells were stained in whole cord blood. Analyses were done using traditional gating approaches and computational methodologies (t‐distributed stochastic neighbour embedding and PhenoGraph algorithms). At 6 weeks of age, the time to peak tidal expiratory flow as a percentage of total expiratory flow time (tPTEF/tE%) was determined as well as Lung Clearance Index (LCI), during quiet natural sleep.

Results

Of 110 eligible infants (March 2017 to November 2019), 91 were successfully immunophenotyped (82.7%). Lung function was attempted in 61 infants (67.0%), and 43 of those infants (70.5% of attempted) had technically acceptable tPTEF/tE% measurements. Thirty‐four infants (55.7% of attempted) had acceptable LCI measurements. Foetal ILC2 numbers with increased expression of chemoattractant receptor‐homologous molecule (CRTh2), characterised by two distinct analysis methodologies, were associated with poorer infant lung function at 6 weeks of age.”

Conclusion

Foetal immune responses may be a surrogate variable for or directly influence lung function outcomes in early life.

Small-airway dysfunction in paediatric asthma

PURPOSE OF REVIEW

Asthma is a chronic inflammatory airway disorder that can involve the entire bronchial tree. Increasing evidence shows that ventilation heterogeneity and small airway dysfunction are relevant factors in the pathogenesis of asthma and represent a hallmark in adults with persistent asthma. Little is known about the contribution of peripheral airway impairment in paediatric asthma, mainly due to the inaccessibility to evaluation by noninvasive techniques, which have only been widely available in recent years.

RECENT FINDINGS

Emerging evidence suggests that small airways are affected from the early stages of the disease in childhood-onset asthma. Conventional lung function measurement, using spirometry, is unable to sensitively evaluate small airway function and may become abnormal only once there is a significant burden of disease. Recent studies suggest that chronic inflammation and dysfunction in the small airways, as detected with new advanced techniques, are risk factors for asthma persistence, asthma severity, worse asthma control and loss of pulmonary function with age, both in adults and children. Knowing the extent of central and peripheral airway involvement is clinically relevant to achieve asthma control, reduce bronchial hyper-responsiveness and monitor response to asthma treatment.

SUMMARY

This review outlines the recent evidence on the role of small airway dysfunction in paediatric asthma development and control, and addresses how the use of new diagnostic techniques available in outpatient clinical settings, namely impulse oscillometry and multiple breath washout, could help in the early detection of small airway impairment in children with preschool wheezing and school-age asthma and potentially guide asthma treatment.

Assessment of bronchial obstruction and its reversibility by shape indexes of the flow-volume loop in asthmatic children

Asthma assessment by spirometry is challenging in children as forced expiratory volume in 1 s (FEV1) is frequently normal at baseline. Bronchodilator (BD) reversibility testing may reinforce asthma diagnosis but FEV1 sensitivity in children is controversial. Ventilation inhomogeneity, an early sign of airway obstruction, is described by the upward concavity of the descending limb of the forced expiratory flow-volume loop (FVL), not detected by FEV1. The aim was to test the sensitivity and specificity of FVL shape indexes as β-angle and forced expiratory flow at 50% of the forced vital capacity (FEF50)/peak expiratory flow (PEF) ratio, to identify asthmatics from healthy children in comparison to "usual" spirometric parameters. Seventy-two school-aged asthmatic children and 29 controls were prospectively included. Children performed forced spirometry at baseline and after BD inhalation. Parameters were expressed at baseline as z-scores and BD reversibility as percentage of change reported to baseline value (Δ%). Receiver operating characteristic curves were generated and sensitivity and specificity at respective thresholds reported. Asthmatics presented significantly smaller zβ-angle, zFEF50/PEF and zFEV1 (p ≤ .04) and higher BD reversibility, significant for Δ%FEF50/PEF (p = .02) with no difference for Δ%FEV1. zβ-angle and zFEF50/PEF exhibited better sensitivity (0.58, respectively 0.60) than zFEV1 (0.50), and similar specificity (0.72). Δ%β-angle showed higher sensitivity compared to Δ%FEV1 (0.72 vs. 0.42), but low specificity (0.52 vs. 0.86). Quantitative and qualitative assessment of FVL by adding shape indexes to spirometry interpretation may improve the ability to detect an airway obstruction, FEV1 reflecting more proximal while shape indexes peripheral bronchial obstruction.

Ventilation heterogeneity in children with severe asthma

Small airway disease, characterised by ventilation heterogeneity (VH), is present in a subgroup of patients with asthma. Ventilation heterogeneity can be measured using multiple breath washout testing. Few studies have been reported in children. We studied the relationship between VH, asthma severity, and spirometry in a cross-sectional observational cohort study involving children with stable mild-moderate and severe asthma by GINA classification and a group of healthy controls. Thirty-seven participants aged 5-16 years completed multiple breath nitrogen washout (MBNW) testing (seven controls, seven mild-moderate asthma, 23 severe asthma). The lung clearance index (LCI) was normal in control and mild-moderate asthmatics. LCI was abnormal in 5/23 (21%) of severe asthmatics. The LCI negatively correlated with FEV₁ z-score.Conclusion: VH is present in asthmatic children and appears to be more common in severe asthma. The LCI was significantly higher in the cohort of children with severe asthma, despite no difference in FEV₁ between the groups. This supports previous evidence that LCI is a more sensitive marker of airway disease than FEV₁. MBNW shows potential as a useful tool to assess children with severe asthma and may help inform clinical decisions. What is Known: • Increased ventilation heterogeneity is present in some children with asthma • Spirometry is not sensitive enough to detect small airway involvement in asthma What is New • Lung clearance index is abnormal in a significant subgroup of children with severe asthma but rarely in children with mild-moderate asthma • Our data suggests that LCI monitoring should be considered in children with severe asthma.

Lung clearance index: A new measure of late lung complications of cancer therapy in children

INTRODUCTION

Childhood cancer survivors (CSs) might face an increased lifelong risk of lung function impairment. The lung clearance index (LCI) has been described as being more sensitive than spirometry in the early stages of some lung diseases. The aim of this study was to evaluate this index in a cohort of patients with a history of childhood cancer for the first time.

MATERIALS AND METHODS

We evaluated 57 off-treatment CSs aged 0-18 years old and 50 healthy controls (HCs). We used the multiple-breath washout method to study LCI and spirometry.

RESULTS

CSs did not show any differences from the controls in ventilation homogeneity (LCI 6.78 ± 1.35 vs. 6.32 ± 0.44; p: not significant [ns]) or lung function (FEV1 99.9 ± 11.3% vs. 103.0 ± 5.9% of predicted; p: ns; FVC 98.2 ± 10.3% vs. 101.1 ± 3.3% of predicted). LCI significantly correlated with the number of years since the last chemotherapy (r = .35, p < .05).

CONCLUSIONS

Our study describes the trend of LCI in a cohort of CSs and compares it with the results obtained from HCs. The results show that patients maintain both good values of respiratory function and good homogeneity of ventilation during childhood. Moreover, as LCI increases and worsens as the years pass after the end of the treatment could identify the tendency toward pulmonary fibrosis, which is typical of adult CSs, at an earlier time than spirometry.

Asthma and Lung Mechanics

This article will discuss in detail the pathophysiology of asthma from the point of view of lung mechanics. In particular, we will explain how asthma is more than just airflow limitation resulting from airway narrowing but in fact involves multiple consequences of airway narrowing, including ventilation heterogeneity, airway closure, and airway hyperresponsiveness. In addition, the relationship between the airway and surrounding lung parenchyma is thought to be critically important in asthma, especially as related to the response to deep inspiration. Furthermore, dynamic changes in lung mechanics over time may yield important information about asthma stability, as well as potentially provide a window into future disease control. All of these features of mechanical properties of the lung in asthma will be explained by providing evidence from multiple investigative methods, including not only traditional pulmonary function testing but also more sophisticated techniques such as forced oscillation, multiple breath nitrogen washout, and different imaging modalities. Throughout the article, we will link the lung mechanical features of asthma to clinical manifestations of asthma symptoms, severity, and control. © 2020 American Physiological Society. Compr Physiol 10:975-1007, 2020.