Impulse oscillometry in the evaluation of diseases of the airways in children

Advances in Pediatric Lung Function Testing Techniques

For decades spirometry has been the benchmark test for capturing lung function in children but its recognized limitations required the development of other techniques. This article introduces novel techniques in lung function assessment for pediatric patients, including multiple breath washout, impulse oscillometry, structured light plethysmography, and electrical impedance tomography, and common themes in interpreting the results. Challenges include standardization, reference data, and clinical integration of these innovative tools. Further research is ongoing to optimize these tests for clinical use, especially in diverse populations and pediatric settings.

Pediatric pulmonology year in review 2023: Physiology

Application of the principles of pulmonary physiology and lung development to the care and management of respiratory disease in children is a distinguishing feature of pediatric pulmonology. In 2023, this was evident in numerous publications in Pediatric Pulmonology and other journals. This review will highlight some of the papers in this area.

Inflammatory imbalance in tracheal aspirate of very preterm newborns is associated with airway obstruction and lung function deficiencies at school age: a cohort study

OBJECTIVE

A low expression of club cell secretory protein (CC16) and high levels of proinflammatory cytokines at preterm birth are associated with airway inflammation and more severe neonatal lung disease. The present study aimed to investigate if low levels of CC16, proinflammatory cytokines and vascular endothelial growth factors (VEGF) in tracheal aspirate early after birth were associated with lung function impairment at school age.

PATIENTS AND METHODS

Participants were 20 children, born very preterm (median gestational age 25+3 weeks+days, IQR: 24+1-27+0 weeks+days), who had tracheal aspirates collected during mechanical ventilation in their first day of life. CC16, cytokines, VEGF and matrix metalloproteinase-9 were measured in the tracheal aspirate and later correlated to results from advanced lung function measurements at 12 years of age.

RESULTS

Low levels of CC16 and high levels of the proinflammatory cytokines IL-1β and TNF-α in tracheal aspirate were associated with airway obstruction at school age but not with other lung function parameters. The correlation with airway obstruction was even stronger when the ratio between the respective proinflammatory cytokine and CC16 was used. In addition, low levels of VEGF and CC16 were associated with impaired diffusion capacity of the lung.

CONCLUSIONS

An imbalance in inflammatory mediators and growth factors in the lungs at birth may have consequences for airway function and vasculature at school age in preterm born children.

Impulse oscillometry assessment of respiratory function in pediatric patients with a history of COVID-19

OBJECTIVE

While coronavirus disease 2019 (COVID-19) is generally considered to exhibit a less severe clinical course in children than in adults, studies have demonstrated that respiratory symptoms can endure for more than 3 months following infection in at least one-third of pediatric cases. The present study evaluates the respiratory functions of children aged 3-15 years within 3-6 months of their recovery from COVID-19 using impulse oscillometry (IOS) and compares them with the values of healthy children.

METHODS

Included in this prospective cross-sectional study were 63 patients (patient group) aged 3-15 years who contracted COVID-19 between December 2021 and May 2022, as well as 57 healthy children as a control group, matched for age and sex. The demographic, clinical, and laboratory data of the patients were recorded, and respiratory function was assessed based on airway resistance (zR5, zR20, R5-20) and reactance (zX5, zX20, reactance area [AX], resonant frequency [Fres]) using an IOS device.

RESULTS

There were no significant differences in the age, weight, height, and body weight z score values of the two groups (p > .05). While the zR5 and R5-20 levels of the patient group were higher (p = .008 and p < .001, respectively) than those of the controls, the zR20, AX, and Fres values did not differ significantly between the groups (p > .05). The parameters indicating the reactance, including zX5 and zX20, were significantly lower in the patient group than in the control group (p = .028 and p < .001, respectively).

CONCLUSION

Total and peripheral airway resistances were found to be elevated in children who had recovered from COVID-19 in the preceding 3-6 months.

Using Machine Learning with Impulse Oscillometry Data to Develop a Predictive Model for Chronic Obstructive Pulmonary Disease and Asthma

We aimed to develop and validate a machine learning model using impulse oscillometry system (IOS) profiles for accurately classifying patients into three assessment-based categories: no airflow obstruction, asthma, and chronic obstructive pulmonary disease (COPD). Our research questions were as follows: (1) Can machine learning methods accurately classify obstructive disease states based solely on multidimensional IOS data? (2) Which IOS parameters and modeling algorithms provide the best discrimination? We used data for 480 patients (240 with COPD and 240 with asthma) and 84 healthy individuals for training. Physiological and IOS parameters were combined into six feature combinations. The classification algorithms tested were logistic regression, random forest, neural network, k-nearest neighbor, and support vector machine. The optimal feature combination for identifying individuals without pulmonary obstruction, with asthma, or with COPD included 15 IOS and physiological features. The neural network classifier achieved the highest accuracy (0.786). For discriminating between healthy and unhealthy individuals, two combinations of twenty-three features performed best in the neural network algorithm (accuracy of 0.929). When distinguishing COPD from asthma, the best combination included 15 features and the neural network algorithm achieved an accuracy of 0.854. This study provides compelling technical evidence and clinical justifications for advancing IOS data-driven models to aid in COPD and asthma management.

The influence of body mass index on airway resistance in children with sickle cell disease: A longitudinal study based on impulse oscillometry

BACKGROUND

Impulse oscillometry (IOS) is an effective tool for assessing airway mechanics and diagnosing obstructive airway disease (OAD) in children with sickle cell disease (C-SCD). Obesity is known to be associated with OAD, and untreated OAD often leads to hypoxia-related complications in C-SCD. Considering the increasing prevalence of obesity in C-SCD, it is important to explore the influence of body mass index (BMI) on OAD in this disease population.

METHODS

A longitudinal retrospective chart review was conducted on 55 C-SCD (161 IOS observations) and 35 non-SCD asthmatic children (C-Asthma) (58 observations), primarily to investigate the association between BMI and airway resistance in C-SCD and C-Asthma. We conducted generalized linear mixed models (GLMM), adjusted for pharmacotherapies, to demonstrate the influence of BMI on total (R5), central (R20), and peripheral (R5-20) airway resistance and reactance (X5, resonant frequency (Fres)). We further compared age, BMI, and IOS indices between C-SCD and C-Asthma using the Mann-Whitney test.

RESULTS

Age and BMI were not statistically different between the two groups. In C-SCD, BMI was associated with R5 (GLMM t-statistics:3.75, 95%CI:1.01,3.27, p-value<0.001*) and R20 (t-statistics:4.01, 95%CI:1.04,1.15, p-value<0.001*), but not with R5-20 or airway reactance. In asthmatics, BMI was not associated with IOS estimates except Fres (t-statistics: 3.93, 95%CI: -0.06, -0.02, p-value<0.001*). C-SCD demonstrated higher airway resistances (R5 and R20) and reactance (Fres) compared to C-Asthma (Mann-Whitney: p-values<0.05).

CONCLUSION

BMI significantly influenced total and central airway resistance in C-SCD. While higher airway resistances reflected increased OAD in C-SCD than asthmatics, higher Fres perhaps indicated progressive pulmonary involvement in C-SCD.

Impulse oscillometry in patients with pulmonary arterial hypertension: an exploratory study

INTRODUCTION

Studies suggest peripheral airway abnormalities in Pulmonary Arterial Hypertension (PAH). Impulse Oscillometry (IOS) is a noninvasive and sensitive technique for assessing the small airways. It evaluates the impedance of the respiratory system ‒ Resistance (R) and reactance (X) ‒ to a pulse of sound waves sent to the lungs, in a range of frequencies (5‒20 Hz).

METHOD

Resistance variables: R5, R20, R5-R20 and reactance variables: AX (reactance area) and Fres (resonance frequency). The aim is to evaluate R and X in patients with idiopathic PAH (IPAH) and to investigate whether there is a correlation between IOS and spirometry.

RESULTS

Thirteen IPAH patients and 11 healthy subjects matched for sex and age underwent IOS and spirometry. IPAH patients had lower FVC and FEV1 values (p < 0.001), VEF1/CVF (p = 0.049) and FEF 25-75 (p = 0.006) than healthy patients. At IOS, IPAH patients showed lower tidal volumes and higher AX (p < 0.05) compared to healthy individuals, and 53.8 of patients had R5-R20 values ≥ 0.07 kPa/L/s. Correlation analysis: X5, AX, R5-R20 and Fres showed moderate correlation with FVC (p = 0.036 r = 0.585, p = 0.001 r = -0.687, p = 0.005 r = -0.726 and p = 0.027 r = -0.610); Fres (p = 0.012 r = -0.669) and AX (p = 0.006 r = -0.711) correlated with FEV1; [R5 and R20, (R5-R20)] also correlated with FEV1 (p < 0.001 r = -0.573, p = 0.020 r = -0.634 and p = 0.010 r = -0.683, respectively) in the IPAH group. There were also moderate correlations of FEF 25-75 % with Z5 (p = 0.041), R5 (p = 0.018), Fres (p = 0.043) and AX (p = 0.023).

DISCUSSION

Patients showed changes suggestive of increased resistance and reactance in the IOS compared to healthy individuals, and the IOS findings showed a good correlation with spirometry variables.

Adding oscillometry to spirometry in guidelines better identifies uncontrolled asthma, future exacerbations, and potential targeted therapy

The objective of this review is to provide new advances in our understanding of the clinical importance of establishing peripheral airway impairment (PAI) by impulse oscillometry (IOS) and targeted therapy, which could result in better asthma outcomes. Data sources include PubMed and Google search, limited to English language and human disease, with key words IOS and asthma. Key findings include PAI being consistently associated with uncontrolled asthma across ethnicities, using IOS reference equations factoring Hispanic and White reference algorithms. It is noted that PAI is common even in patients considered well-controlled by asthma guidelines. In a large longitudinal analysis (Assessment of Small Airways Involved in Asthma or ATLANTIS study), a composite of R5-R20, AX, and X5 ordinal scores were independently predictive of asthma control and exacerbation in a multivariate analysis, but forced expiratory volume in 1 second was not significantly predictive of morbidities. However, combining forced expiratory volume in 1 second less than 80% with PAI resulted in greater odds of identifying uncontrolled asthma and exacerbations, than either alone. Applying an external validation method in children with asthma offers the clinician the IOS reference equations best fit for their own specific population. Several clinical phenotypes can also identify PAI with high probability, useful when IOS is not available. Poor asthma outcomes for obese patients with asthma are associated with dysanapsis and PAI, not obesity alone. Extrafine inhaled corticosteroids achieve better asthma control and improve peripheral airway function with fewer exacerbations at lower dosages than nonextrafine inhaled corticosteroid aerosols. In conclusion, these data support the benefit of adding IOS to spirometry in future asthma guidelines and suggest the potential benefit from targeted therapy.

Respiratory system parameters in children with low severity cystic fibrosis: is there early involvement in relation to healthy peers?

OBJECTIVE

To compare and analyze pulmonary function and respiratory mechanics parameters between healthy children and children with cystic fibrosis.

METHODS

This cross-sectional analytical study included healthy children (HSG) and children with cystic fibrosis (CFG), aged 6-13 years, from teaching institutions and a reference center for cystic fibrosis in Florianópolis/SC, Brazil. The patients were paired by age and sex. Initially, an anthropometric evaluation was undertaken to pair the sample characteristics in both groups; the medical records of CFG were consulted for bacterial colonization, genotype, and disease severity (Schwachman-Doershuk Score - SDS) data. Spirometry and impulse oscillometry were used to assess pulmonary function.

RESULTS

In total, 110 children were included, 55 in each group. In the CFG group, 58.2% were classified as excellent by SDS, 49.1% showed the ΔF508 heterozygotic genotype, and 67.3% were colonized by some pathogens. Statistical analysis revealed significant differences between both groups (p<0.05) in most pulmonary function parameters and respiratory mechanics.

CONCLUSIONS

Children with cystic fibrosis showed obstructive ventilatory disorders and compromised peripheral airways compared with healthy children. These findings reinforce the early changes in pulmonary function and mechanics associated with this disease.

Diagnostic accuracy of peripheral lung function measurements in paediatric asthma control assessment: a pilot study

Introduction

Recent studies have indicated the significance of the peripheral airways in asthma control. Methods estimating airway resistance, air trapping, and ventilation inhomogeneity are useful for assessing this area of the lung and have proven utility in the evaluation of asthma; however, it is unclear which method is most effective at characterising uncontrolled asthma.

Aim

To evaluate the diagnostic accuracy of various peripheral airway function measurements in the assessment of asthma control in children.

Material and methods

Children with controlled (n = 35) and uncontrolled (n = 29) asthma performed a sequence of pulmonary function tests (i.e. spirometry, body plethysmography, oscillometry, nitrogen washout test, and exhaled nitric oxide). The diagnostic accuracy of each peripheral airway measure was evaluated by an area under the receiver operating characteristic curve (AUC).

Results

Most peripheral airway parameters were significantly increased in children with uncontrolled asthma compared with children with controlled asthma. The measures with the highest diagnostic accuracy for asthma control were lung clearance index (LCI) (AUC = 0.76), with high specificity (0.97) and modest sensitivity (0.46), acinar ventilation heterogeneity (Sacin) (AUC = 0.73), with high sensitivity (0.85) and modest specificity (0.54), and resonance frequency (Fres) (AUC= 0.74), with perfect specificity (1.0) but low sensitivity (0.38).

Conclusions

LCI, Sacin and Fres had the highest discriminative capacity for distinguishing children with controlled and uncontrolled asthma among all evaluated peripheral airways measures. Discrepancies in the performance (i.e. sensitivity and specificity) of each parameter suggest that a combination may be most effective in determining asthma control status.

The Role of Small Airway Disease in Pulmonary Fibrotic Diseases

Small airway disease (SAD) is a pathological condition that affects the bronchioles and non-cartilaginous airways 2 mm or less in diameter. These airways play a crucial role in respiratory function and are often implicated in various pulmonary disorders. Pulmonary fibrotic diseases are characterized by the thickening and scarring of lung tissue, leading to progressive respiratory failure. We aimed to present the link between SAD and fibrotic lung conditions. The evidence suggests that SAD may act as a precursor or exacerbating factor in the progression of fibrotic diseases. Patients with fibrotic conditions often exhibit signs of small airway dysfunction, which can contribute to worsening respiratory symptoms and decreased lung function. Moreover, individuals with advanced SAD are at a heightened risk of developing fibrotic changes in the lung. The interplay between inflammation, environmental factors, and genetic predisposition further complicates this association. The early detection and management of SAD can potentially mitigate the progression of fibrotic diseases, highlighting the need for comprehensive clinical evaluation and research. This review emphasizes the need to understand the evolving connection between SAD and pulmonary fibrosis, urging further detailed research to clarify the causes and potential treatment between the two entities.

An experimental study on lung deposition of inhaled 2 μm particles in relation to lung characteristics and deposition models

BACKGROUND

The understanding of inhaled particle respiratory tract deposition is a key link to understand the health effects of particles or the efficiency for medical drug delivery via the lung. However, there are few experimental data on particle respiratory tract deposition, and the existing data deviates considerably when comparing results for particles > 1 μm.

METHODS

We designed an experimental set-up to measure deposition in the respiratory tract for particles > 1 μm, more specifically 2.3 μm, with careful consideration to minimise foreseen errors. We measured the deposition in seventeen healthy adults (21-68 years). The measurements were performed at tidal breathing, during three consecutive 5-minute periods while logging breathing patterns. Pulmonary function tests were performed, including the new airspace dimension assessment (AiDA) method measuring distal lung airspace radius (rAiDA). The lung characteristics and breathing variables were used in statistical models to investigate to what extent they can explain individual variations in measured deposited particle fraction. The measured particle deposition was compared to values predicted with whole lung models. Model calculations were made for each subject using measured variables as input (e.g., breathing pattern and functional residual capacity).

RESULTS

The measured fractional deposition for 2.3 μm particles was 0.60 ± 0.14, which is significantly higher than predicted by any of the models tested, ranging from 0.37 ± 0.08 to 0.53 ± 0.09. The multiple-path particle dosimetry (MPPD) model most closely predicted the measured deposition when using the new PNNL lung model. The individual variability in measured particle deposition was best explained by breathing pattern and distal airspace radius (rAiDA) at half inflation from AiDA. All models underestimated inter-subject variability even though the individual breathing pattern and functional residual capacity for each participant was used in the model.

CONCLUSIONS

Whole lung models need to be tuned and improved to predict the respiratory tract particle deposition of micron-sized particles, and to capture individual variations - a variation that is known to be higher for aged and diseased lungs. Further, the results support the hypothesis that the AiDA method measures dimensions in the peripheral lung and that rAiDA, as measured by the AiDA, can be used to better understand the individual variation in the dose to healthy and diseased lungs.

Oscillometry in Lung Function Assessment: A Comprehensive Review of Current Insights and Challenges

Oscillometry, a non-invasive technique for assessing lung function, has gained significant recognition and importance in modern pulmonary medicine. This comprehensive review thoroughly explores its principles, applications, advantages, limitations, recent innovations, and future directions. Oscillometry's primary strength lies in its ability to offer a holistic assessment of lung mechanics. Unlike traditional spirometry, oscillometry captures the natural airflow during quiet breathing, making it suitable for patients of all ages and those with severe respiratory conditions. It provides a comprehensive evaluation of airway resistance, reactance, and compliance, offering insights into lung function that were previously challenging to obtain. In clinical practice, oscillometry finds extensive application in diagnosing and managing respiratory diseases. It plays a pivotal role in asthma, chronic obstructive pulmonary disease (COPD), and interstitial lung diseases. By detecting subtle changes in lung function before symptoms manifest, oscillometry facilitates early interventions, improving disease management and patient outcomes. Oscillometry's non-invasive and patient-friendly nature is precious in pediatric care, where traditional spirometry may be challenging for young patients. It aids in diagnosing and monitoring pediatric respiratory disorders, ensuring that children receive the care they need from an early age. Despite its many advantages, oscillometry faces challenges, such as the need for standardized protocols and the complexity of data interpretation. However, ongoing efforts to establish global standards and provide education and training for healthcare professionals aim to address these issues. Looking ahead, oscillometry holds great promise in the field of personalized medicine. With its ability to tailor treatment plans based on individualized lung function data, healthcare providers can optimize therapy selection and dosing, ultimately improving patient care and quality of life. In conclusion, oscillometry is poised to play an increasingly pivotal role in modern pulmonary medicine. As standardization efforts continue and technology evolves, it is an indispensable tool in the clinician's arsenal for diagnosing, managing, and personalizing respiratory care, ultimately leading to improved patient outcomes and better respiratory health.

Window of opportunity for respiratory oscillometry: A review of recent research

Oscillometry has been around for almost 70 years, but there are still many unknowns. The test is performed during tidal breathing and is therefore free from patient-dependent factors that could influence the results. The Forced Oscillation Technique (FOT), which requires minimal patient cooperation, is gaining ground, particularly with elderly patients and children. In pulmonology, it is a valuable tool for assessing obstructive conditions (with a distinction between central and peripheral obstruction) and restrictive disorders (intrapulmonary and extrapulmonary). Its sensitivity allows the assessment of bronchodilator and bronchoconstrictor responses. Different lung diseases show different patterns of changes in FOT, especially studied in asthma and chronic obstructive pulmonary disease. Because of these differences, many studies have analysed the usefulness of this technique in different areas of medicine. In this paper, the authors would like to present the basics of oscillometry with the areas of its most recent clinical applications.

Impulse oscillometry indices in relation to respiratory symptoms and spirometry in the Swedish Cardiopulmonary Bioimage Study

Background

Impulse oscillometry (IOS) is sensitive in detecting lung function impairment. In small studies, impaired IOS relates better to respiratory symptoms than spirometry. We studied how IOS related to spirometry and respiratory symptoms in a large population of individuals (n=10 360) in a cross-sectional analysis.

Methods

Normal values for IOS and spirometry were defined in healthy, never-smoking individuals, aged 50-64 years, from the Swedish CArdioPulmonary bioImage Study (n=3664 for IOS and 3608 for spirometry). For IOS, abnormal values for resistance at 5 Hz (R5) and at 20 Hz and area of reactance were defined using the 95th percentile. Abnormal reactance at 5 Hz for IOS and abnormal conventional spirometry indices (forced expiratory volume in 1 s (FEV1), forced and slow vital capacity and their ratios) were defined using the 5th percentile.

Results

Abnormal IOS parameters were found in 16% of individuals and were associated with increased odds ratios for nearly all respiratory symptoms when adjusted for age, gender and smoking. In individuals with normal spirometry, abnormal IOS resistance was related to cough and dyspnoea, while abnormal reactance was related to wheeze. In these individuals, the combination of abnormal R5 with abnormal reactance resulted in approximately two-fold higher likelihood for having cough, chronic bronchitis and dyspnoea, even when further adjusting for FEV1, expressed as % predicted.

Conclusions

Abnormal IOS is related to increased respiratory burden in middle-aged individuals with normal spirometry, especially when resistance and reactance parameters are combined. The different relationships between respiratory symptoms and reactance and resistance warrant further research.

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.

A Longitudinal Study of Respiratory Mechanics in Pregnant Women with Obesity and Overweight

PURPOSE

Respiratory mechanics and the role of sex hormones in pregnancy are not well elucidated. We examined longitudinal and positional changes in lung mechanics in pregnancy and investigated the role of sex hormones.

METHODS

A longitudinal study enrolled 135 women with obesity in early pregnancy. Fifty-nine percent of women identified as White; median body mass index at enrollment was 34.4 kg/m2. Women with respiratory disease were excluded. We obtained measurements of airway resistance and respiratory system reactance in various positions using impedance oscillometry and sex hormones in early and late pregnancy.

RESULTS

With pregnancy progression, there was a significant increase in resonant frequency (Fres) (p = 0.012), integrated area of low frequency reactance (AX) (p = 0.0012) and R5-R20Hz (p = 0.038) in the seated position, and a significant increase in R5Hz (p = 0.000), Fres (p = 0.001), AX (p < 0.001 = 0.000), and R5-R20Hz (p = 0.014) in the supine position. Compared to the seated position, the supine position was associated with a significant increase in R5Hz, R20Hz, X5Hz, Fres, and AX in early (p-values < 0.026) and late pregnancy (p-values ≤ 0.001). Changes in progesterone levels between early and late pregnancy predicted the change in R5, Fres, and AX (p-values ≤ 0.043).

CONCLUSION

Resistive and elastic loads increase with pregnancy progression and a change in body position from seated to supine increases resistive and elastic loads in both early and late pregnancies. The increase in airway resistance is primarily related to an increase in peripheral rather than central airways resistance. There was an association between the change in progesterone levels and airway resistance.

Impulse oscillometry system for assessing small airway dysfunction in pediatric bronchiolitis obliterans; association with conventional pulmonary function tests

Impulse oscillometry system (IOS) is a simple, and less invasive method for assessing small to total airway resistance in children. We analyzed the correlation between IOS, spirometry, and plethysmographic parameters performed for the diagnosis of pediatric BO patients. A total of 89 IOS assessments of pediatric BO patients or children without lung disease were included, and the relationship between pulmonary function tests (PFTs) and diagnostic performance was analyzed. R5, R5-20, X5, and AX were statistically significantly worse in the BO group. In general linear correlation analysis, R5% (adjusted β [aβ], -0.59; p < 0.001) and AX % (aβ, -0.9; p < 0.001) showed the strongest correlation with conventional PFT parameters. R5% and AX % also showed the highest correlation with FEF25-75% (aβ, -0.48; p < 0.001 and aβ, -0.83; p < 0.001), and sRaw % (aβ, -0.73; p = 0.003 and aβ, -0.59; p = 0.008, respectively). Multivariate logistic regression analysis showed that R5 Z-score showed the highest ORs with FEV1 (OR = 3.94, p = 0.006), FEF25-75% (OR = 5.96, p = 0.005), and sRaw % (OR = 4.85, p = 0.022). Receiver operating curve analysis suggested AX % and R5% as the most optimal IOS parameters for BO diagnostic performance with the area under the curve of 0.915 and 0.882, respectively. In conclusion, R5 and AX are the parameters that can independently identify the severity of airway obstruction in pediatric BO patients without conventional lung function tests. IOS is an easy-to-perform, and reliable diagnostic method capable of detecting pathological obliteration of the small airways in children with BO.

Role of impulse oscillometry in diagnosis and follow-up in bronchial asthma

Background

Asthma is defined as a chronic inflammatory disorder of the airways, characterized by bronchial hyper-responsiveness and variable airflow obstruction, that is often reversible either spontaneously or with treatment. Impulse oscillometry is a newer diagnostic modality for asthma. It is based on the measurement of sound waves reflected by airway resistance.

Objectives

The aim of this article is to study the role of impulse oscillometry in diagnosis and follow-up of bronchial asthma.

Methods

Fifty-five clinically diagnosed bronchial asthma patients were evaluated with spirometry and impulse oscillometry before and after 3 months of inhaled treatment. The sensitivity to diagnose and follow-up was compared using proper statistical tests.

Results

Impulse oscillometry was superior to spirometry in diagnosing bronchial asthma and also in accessing the treatment response after 3 months.

Conclusion

Impulse oscillometry is superior in predicting bronchial asthma and its parameters are also more sensitive in accessing treatment response. It can replace spirometry as it is easy to perform and effort independent.

External validation can provide the clinician with IOS equations that best predict the risk of uncontrolled asthma in their population

BACKGROUND

Peripheral airway impairment (PAI) has been shown to have a close association to risk of uncontrolled asthma in children. However, clear methods have not been established for the clinician to select impulse oscillometry (IOS) reference equations best suited for their population. Our study aimed to develop a practical external validation analytic approach for the clinician to determine which of the available reference equations best predicts uncontrolled asthma for their patients.

METHODS

This is a post hoc analyses of data collected at baseline in a randomized controlled study that occurred from March 2016 to 2018. The study population consisted of 227 children, ages 4-18 years, with moderate to severe asthma. Discrimination and calibration predictive performance of available and suitable IOS equations were assessed by using uncontrolled asthma as the criterion outcome. Discrimination statistics of accuracy, sensitivity, and specificity served as the primary performance indicators. Rank scores were determined by the number of acceptable limit thresholds met for these measures (≥60%, ≥50%, and ≥60%, respectively) across IOS metrics (R5, R5-R20, AX, and X5) resulting in a total possible score of 12.

RESULTS

External validity assessment determined the rank order of best to worst equations as being Gochicoa-Rangel (rank score = 10) > Nowowiejska (rank score = 9) > Assumapcao (rank score = 6) > Amra (rank score = 2). Gochicoa-Rangel reference equations provided the best option for universal application with accuracy of 73.1%, 72.2%, 76.7%, and 66.2% for R5, R5-R20, AX, and X5, respectively.

CONCLUSIONS

External validation, particularly discrimination in asthmatic children, offers the clinician a practical approach to selecting the most suitable predictive equations for their patients.

Increased airway resistance among exclusive waterpipe smokers detected using impulse oscillometry

INTRODUCTION

Waterpipe smoking is increasing in popularity, yet the evidence implicating waterpipe smoking in lung disease is limited. We hypothesized that impulse oscillometry (IOS) would detect airway abnormalities in waterpipe smokers (WPS).

METHODS

We studied 210 participants, 40 years or older, from the community, of whom 92 were exclusive WPS and 118 were never-smokers. Waterpipe smoking history was assessed using a validated questionnaire. All participants underwent spirometry, and IOS and absolute and percentage predicted results (for age, sex, height, and weight) were compared between WPS and nonsmokers. The association of IOS parameters with waterpipe smoking duration and extent (waterpipe smoked/day * smoking duration) was evaluated using linear regression.

RESULTS

WPS smoked on average 1.8 ± 1.2 waterpipes/day, over an average duration of 23.3 ± 39.8 years. WPS and nonsmokers were largely asymptomatic and had similar age, body mass index, sex distribution, and spirometric values. Nevertheless, WPS had higher IOS measured resistance at 5Hz compared to nonsmokers, (0.53 ± 0.2 vs. 0.48 ± 0.2 kPa/L/s, P = 0.03) and higher percentage-predicted resistance (124.5 ± 36.3 vs. 115.7% ± 35.6%, P = 0.04). Waterpipe smoking duration was also associated with resistance (β = 0.04 kPa/L/s/year, P = 0.01) and with percentage-predicted resistance (β = 0.05/year, P = 0.02). Waterpipe smoking extent was associated with resistance (β = 0.009 kPa/L/s/waterpipe-year, P = 0.04), while the association with percentage-predicted resistance was near significance (β = 0.009/waterpipe-year, P = 0.07).

CONCLUSIONS

Waterpipe smoking is associated with increased airway resistance assessed by IOS but not by spirometry in largely asymptomatic individuals from the community.

Utility of biomarkers in the diagnosis and monitoring of asthmatic children

Asthma imposes a heavy morbidity burden during childhood; it affects over 10% of children in Europe and North America and it is estimated to exceed 400 million people worldwide by the year 2025. In clinical practice, diagnosis of asthma in children is mostly based on clinical criteria; nevertheless, assessment of both physiological and pathological processes through biomarkers, support asthma diagnosis, aid monitoring, and further lead to better treatment outcomes and reduced morbidity. Recently, identification and validation of biomarkers in pediatric asthma has emerged as a top priority across leading experts, researchers, and clinicians. Moreover, the implementation of non-invasive biomarkers for the assessment and monitoring of paediatric patients with asthma, has been prioritized; however, only a proportion of them are currently included in the clinical practise. Although, the use of non-invasive biomarkers is highly supported in recent asthma guidelines for documenting diagnosis and supporting monitoring of asthmatic patients, data on the Pediatric population are limited. In the present report, the Pediatric Asthma Committee of the World Allergy Organization (WAO), aims to summarize and discuss available data for the implementation of non-invasive biomarkers in the diagnosis and monitoring in children with asthma. Information on the most studied biomarkers, including spirometry, oscillometry, markers of allergic sensitization, fractional exhaled nitric oxide, and the most recent exhaled breath markers and "omic" approaches, will be reviewed. Practical limitations and considerations based on both experts' opinion and critical review of the literature, on the utility of all "well-known" and newly introduced non-invasive biomarkers will be presented. A critical commentary on biomarkers' use in diagnosing and monitoring asthma during the COVID-19 pandemic, cost and availability of biomarkers in different settings and in developing countries, the differences on the biomarkers use between Primary Practitioners, Pediatricians, and Specialists and their role on the longitudinal aspect of asthma is provided.

Mechanical effects of obesity on central and peripheral airway resistance in nonasthmatic early pubescent children

BACKGROUND

In children, obesity typically reduces functional residual capacity (FRC), which reduces airway caliber and increases airway resistance. Whether these obesity-related changes in respiratory function can alter bronchodilator responsiveness is unknown.

OBJECTIVE

To investigate bronchodilator responsiveness in nonasthmatic children with and without obesity.

METHODS

Seventy nonasthmatic children, 8-12 years old, without (n = 19) and with (n = 51) obesity, completed spirometry, impulse oscillometry, and airway resistance measurements through plethysmography pre/post 360 µg of inhaled albuterol. FRC was assessed pre albuterol. A two-way analysis of variance determined the effects of obesity (group) and inhaled albuterol (pre-post) on outcome measures.

RESULTS

FRC (%total lung capacity) was 16% lower in children with obesity compared with those without obesity. There was no significant group by pre-post albuterol interaction on any outcome variables. Albuterol inhalation reduced total, central and peripheral airway resistance and increased airway reactance (i.e., less negative) to a similar degree in children with and without obesity. In children with obesity, airway resistance was increased whether measured by impulse oscillometry or plethysmography. However, once airway resistance was adjusted for lung volumes (i.e., specific airway resistance or sRaw ), there were no differences between children with and without obesity. In addition, significant but moderate associations were detected between chest mass and FRC (r = -0.566; p < 0.001), FRC and total airway resistance (i.e., Raw ; r = -0.445; p < 0.001).

CONCLUSIONS

In nonasthmatic early pubescent children, obesity increases total, central, and peripheral respiratory system resistance. However, the added respiratory system resistance and low lung volume breathing with obesity are not sufficient to reduce bronchodilator responsiveness.

Pulmonary Function in Paediatric Patients with Inflammatory Bowel Disease

BACKGROUND

Among the extraintestinal manifestations of inflammatory bowel disease (IBD), those involving the lungs are relatively rare and often overlooked. There are only scarce data on the prevalence of IBD-associated lung involvement in children.

OBJECTIVES

The aim of our study was to assess pulmonary function in IBD children by different methods and to evaluate the influence of immunosuppressive therapy on disease severity.

METHODS

Seventy-two children with IBD (mean age of 14.45 ± 2.27 years) and 40 age-matched healthy controls (mean age of 14.17 ± 2.82) were included in the study. Pulmonary function tests (PFTs) were carried out by means of spirometry, oscillometry (IOS) and fractional exhaled nitric oxide (FeNO) to assess the pulmonary involvement.

RESULTS

Certain differences were observed between the study group and the control group, regarding the spirometric and oscillometry parameters. The fractions of exhaled nitric oxide did not differ between the group with IBD patients and the control group with regards to disease activity, the duration of illness and the administered immunosuppressive treatment.

CONCLUSIONS

The mean spirometry results were significantly different in the study group compared to the controls, although they were still within the normal limits. The pulmonary function abnormalities did not depend on either the disease activity or the immunosuppressive therapy. Oscillometry could be a supplementary method to assess pulmonary resistance. In turn, FeNO does not appear to be useful either in screening IBD children for pulmonary involvement or for the evaluation of disease activity. It appears then that only general screening of asymptomatic patients is a suitable method and a necessary recommendation in this population, prompting a revision of the current diagnostic approach.

Outdoor pollen concentration is not associated with exercise-induced bronchoconstriction in children

BACKGROUND

Free running exercise test outdoors is an important method to diagnose asthma in children. However, the extent of how much exposure to pollens of outdoor air affects the results of the test is not known.

METHODS

We analyzed all reliable exercise challenge tests with impulse oscillometry in children (n = 799) between January 2012 and December 2014 in Tampere University Hospital. Pollen concentrations at the time of the test were collected from the register of Biodiversity Unit of the University of Turku. We compared the frequency of exercise-induced bronchoconstriction and pollen concentrations.

RESULTS

The analyses were restricted to birch and alder pollen as high counts of grass and mugwort pollen were so infrequent. The relative change in resistance at 5 Hz after exercise or the frequency of exercise-induced bronchoconstriction were not related to alder or birch pollen concentrations over 10 grains/m³ (p = 0.125-0.398). In logistic regression analysis comparing the effects of alder or birch pollen concentrations, immunoglobulin E (IgE)-mediated alder or birch allergy and absolute humidity over 10 g/m³ only absolute humidity was independently associated with change in airway resistance (odds ratio [OR]: 0.32, confidence interval [CI]: 0.13-0.67, p: 0.006).

CONCLUSIONS

In our large clinical sample, outdoor air pollen concentration was not associated with the probability of exercise-induced bronchoconstriction in free running test in children while low absolute humidity was the best predictor of airway obstruction.

Advances in the Diagnosis of Equine Respiratory Diseases: A Review of Novel Imaging and Functional Techniques

The horse, as a flight animal with a survival strategy involving rapid escape from predators, is a natural-born athlete with enormous functional plasticity of the respiratory system. Any respiratory dysfunction can cause a decline in ventilation and gas exchange. Therefore, respiratory diseases often lead to exercise intolerance and poor performance. This is one of the most frequent problems encountered by equine internists. Routine techniques used to evaluate respiratory tract diseases include clinical examination, endoscopic examination, radiographic and ultrasonographic imaging, cytological evaluation, and bacterial culture of respiratory secretions. New diagnostic challenges and the growing development of equine medicine has led to the implementation of advanced diagnostic techniques successfully used in human medicine. Among them, the use of computed tomography (CT) and magnetic resonance (MR) imaging significantly broadened the possibilities of anatomical imaging, especially in the diagnosis of upper respiratory tract diseases. Moreover, the implementation of spirometry, electrical impedance tomography (EIT), and impulse oscillation system (IOS) sheds new light on functional diagnostics of respiratory tract diseases, especially those affecting the lower part. Therefore, this review aimed to familiarize the clinicians with the advantages and disadvantages of the advanced diagnostic techniques of the equine respiratory tract and introduce their recent clinical applications in equine medicine.

Association of Dyslipidemia and Respiratory Resistance Assessed by the Forced Oscillation Technique in Asthmatic Children

PURPOSE

This study aimed to evaluate the associations between dyslipidemia and pulmonary function parameters assessed by spirometry and the forced oscillation technique in asthmatic children.

METHODS

Asthmatic children (5-18 years old) had fasting serum lipid profiles including low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), triglyceride (TG), and high-density lipoprotein cholesterol (HDL-C) concentrations, and C-reactive protein (CRP) measured. Pulmonary function tests were assessed by spirometry and the forced oscillation technique (FOT).

RESULTS

One hundred forty-one asthmatic children were enrolled with a mean (SD) age of 11.82 (3.38) years. Eighty-eight (62.4%) children were boys, 64 (45.4%) had dyslipidemia, and 20 (14.2%) were obese. Among the children with dyslipidemia, a high LDL-C concentration (65.6%) was the most common form of dyslipidemia, followed by high TC (57.8%), high TG (35.9%), and low HDL-C concentrations (15.6%). Multivariable analysis showed significant associations between HDL-C concentrations and respiratory resistance at 5 Hz (R₅) and respiratory resistance at 20 Hz (R₂₀), and TC concentrations were modestly associated with reactance at 5 Hz (X₅), the frequency of resonance (Fres), and the area of reactance (ALX). Asthmatic children who had high LDL-C concentrations had a significantly higher expiratory phase R₅, whole breath R₂₀, and expiratory phase R₂₀ than those in children with normal LDL-C concentrations.

CONCLUSION

This study suggests an association of blood cholesterol, especially HDL-C and LDL-C, and respiratory resistance measured by the FOT, irrespective of the obesity status. An intervention for improving LDL-C and HDL-C concentrations may be beneficial on lung function parameters in asthmatic children.

CLINICAL TRIAL REGISTRATION

TCTR20200305005; date of registration: 03-04-2020 (retrospectively registered).

Respiratory function in children with nephrotic syndrome: Comparative evaluation of impulse oscillometry and spirometry

AIM

To evaluate the respiratory functions of children with nephrotic syndrome (NS) by impulse oscillometry (IOS) and its correlation with spirometry.

METHODS

Fifty-five NS patients aged 3-18 years were included as the study group and 40 healthy children of the same age formed the control group. Patients were divided into nephrotic phase (first attack and relapse) and remission. Demographic, anthropometric, and laboratory data of the children were recorded. Respiratory functions were evaluated by IOS and spirometry. Children over 6-years old performed both IOS and spirometry while children under 6 years performed only IOS.

RESULTS

The R (R5%, R10%, R5-20), AX and Z5% values of IOS in patients with nephrotic phase were higher than remission patients and control group while spirometry indices of PEF% and MEF25-75% were lower. Z scores of MEF25-75 were significantly negatively correlated with z scores of R5, R10, Z5, and Fres while they were significantly positively correlated with z scores of X values (5, 10, 15, and 20 Hz). Z scores of forced expiratory volume in 1 /forced vital capacity significantly negatively correlated with z scores of R values (R5, R10), Z5 and AX and positively correlated with z scores of X values (X5, X10, X15 Hz).

CONCLUSION

Our study demonstrated that respiratory functions measured by IOS and spirometry were affected at the time of nephrotic phase in NS patients. IOS, a novel method easily applicable even in small children, is a potentially valuable tool to detect this condition; given its good correlation with spirometry.

Impulse Oscillometry as a measure of airway dysfunction in Sarcoidosis

BACKGROUND

Sarcoidosis is a systemic inflammatory granulomatous disease which commonly affects intrathoracic lymph nodes, lung parenchyma and airways.

OBJECTIVES

To measure respiratory impedance using Impulse Oscillometry (IOS) in patients with pulmonary sarcoidosis and compare the parameters with healthy controls.

METHODS

Patients diagnosed with sarcoidosis (n=28); and age and gender matched healthy controls (n=17) were recruited. Lung volumes and capacities were measured by spirometry and respiratory system impedance was assessed using Impulse Oscillometry System (IOS). Measurements were performed before and 15 minutes after inhalation of a short acting bronchodilator. The IOS and spirometric parameters were compared between two groups and correlated. ROC curve analysis was also performed to identify the IOS parameters which can discriminate between sarcoidosis and healthy controls.

RESULTS

Resistance at 5 and 20 Hz (R5 and R20), small airway resistance (R5-R20), resonant frequency (FRes) and area of reactance (AX) were significantly higher in Sarcoidosis subjects compared with controls. Reactance at 5 and 20 Hz (X5 and X20) were significantly lower in sarcoidosis. FEV1 (% predicted) and FVC (% predicted) were significantly lower in patients with sarcoidosis while FEV1/FVC ratio and peak expiratory flow rate (PEF) values were comparable. Post bronchodilator inhalation, there was improvement in airway resistance and reactance, but no significant changes observed in spirometric parameters. R5, X5 and R5-R20 are promising parameters to discriminate sarcoidosis from healthy controls.

CONCLUSION

Increased airway resistance is a better indicator of airway involvement than airflow limitation by spirometry in pulmonary sarcoidosis.

Peripheral Airway Impairment and Dysanapsis Define Risk of Uncontrolled Asthma in Obese Asthmatic Children

BACKGROUND

Factors that determine the relationship between obesity and poor outcomes in asthmatic children are not well understood. Dysanapsis and peripheral airway impairment (PAI) could provide an explanation in the obese asthmatic patient.

OBJECTIVES

To determine the effect of obesity on increased dysanapsis and PAI and establish the effect of obesity, dysanapsis, and PAI on increased risk of uncontrolled asthma.

METHODS

We evaluated 206 children with moderate to severe asthma, aged 4-18 years, to determine the relationship of body mass index (BMI) to increased dysanapsis and PAI, using reference values. We examined the probability of obesity, dysanapsis, and PAI increasing the risk of uncontrolled asthma by BMI categorically and BMI z scores using generalized linear model analyses.

RESULTS

Compared with normal-weight children, overweight and obese children had increased forced vital capacity % predicted and obesity increased odds of dysanapsis by 2.32 (P = .04), while PAI showed an age-dependent effect, with increased odds of 2.09 for children younger than 12 years (P = .08) and 54.14 for those 12 years and older (P = .003). For each unit increase in BMI z score, there was an increased odds ratio of 1.57 for dysanapsis (P = .009), greater in males, OR of 3.10, P = .009, and of 1.39 for PAI for those younger than 12 years (P = .042) and of 4.60 for those 12 years and older (P = .002). Obesity's relationship to uncontrolled asthma was indirect, as not significant when adjusted for the direct effect of dysanapsis and PAI, which were highly significant predictors, with increased odds of 28.01 for dysanapsis for those younger than 12 years (P < .001) and of 3.09 for PAI (P = .005).

CONCLUSIONS

Overweight and obesity significantly increase odds of dysanapsis and PAI, in an age and gender-specific manner, increasing the probability of uncontrolled asthma.

Allergy and Lung Injury Among Rescue Workers Exposed to the World Trade Center Disaster Assessed 17 Years After Exposure to Ground Zero

OBJECTIVE

Investigate the following in rescue and cleanup workers exposed to the World Trade Center (WTC) disaster 17 years post-fallout: (1) allergic hypersensitivity; (2) spirometry; (3) impulse oscillometry; and (4) the reversibility of airway hyperresponsiveness and distal airways narrowing pre- and post-bronchodilator.

METHODS

In subjects (n = 54) referred to our clinic from the WTC Health Program for management of allergy-immunology services, environmental allergy testing, impulse oscillometry (IOS), and spirometry results were retrospectively reviewed to determine the long-term impact of exposure to the WTC fallout.

RESULTS

Rescue and cleanup workers exposed to the WTC fallout had a high incidence of allergic hypersensitivity and had evidence of permanent small airways dysfunction characterized by distal airways narrowing and airway hyperresponsiveness.

CONCLUSION

Following exposure to the WTC disaster, the patients in our cohort developed allergic hypersensitivity and severe lung injury with only partial reversibility.

The effects of increasing fruit and vegetable intake in children with asthma: A randomized controlled trial

BACKGROUND

A high fruit and vegetable (F&V) diet reduces asthma exacerbations in adults; this has not been examined in children to date.

OBJECTIVE

To investigate the effect of a 6-month, high F&V diet on the time to first asthma exacerbation in children with asthma, in a parallel-group, randomized, controlled trial.

METHODS

Children (aged 3-11 years) with asthma, history of exacerbations and usual low F&V intake (≤3 serves/day) were randomized to the intervention (high F&V diet) or control group (usual diet) for 6 months. The primary outcome was time to first exacerbation requiring medical intervention. Secondary outcomes included exacerbation rate, lung function, plasma TNF-α, CRP, and IL-6, faecal microbiota and peripheral blood mononuclear cell (PBMC) histone deacetylase (HDAC) activity and G-protein coupled receptor (GPR) 41/43 and HDAC (1-11) expression.

RESULTS

67 children were randomized between September 2015 and July 2018. F&V intake (difference in change (∆): 3.5 serves/day, 95% CI: [2.6, 4.4] p < 0.001) and plasma total carotenoids (∆: 0.44 µg/ml [0.19, 0.70] p = 0.001) increased after 6 months (intervention vs control). Time to first exacerbation (HR: 0.81, 95% CI: [0.38, 1.69], p = 0.569) and exacerbation rate (IRR: 0.84, [0.47, 1.49], p = 0.553) were similar between groups. In per-protocol analysis, airway reactance z-scores increased (X₅ ∆: 0.76 [0.04, 1.48] p = 0.038, X₂₀ ∆: 0.93 [0.23, 1.64] p = 0.009) and changes in faecal microbiota were observed, both in the intervention versus control group, though there was no difference between groups in systemic inflammation or molecular mechanisms. In the control group, CRP and HDAC enzyme activity increased, while GPR41 expression decreased. No adverse events attributable to the interventions were observed.

CONCLUSION & CLINICAL RELEVANCE

A high F&V diet did not affect asthma exacerbations over the 6-month intervention, though warrants further investigation as a strategy for improving lung function and protecting against systemic inflammation in children with asthma.

129Xe MRI as a measure of clinical disease severity for pediatric asthma

BACKGROUND

Measurement of regional lung ventilation with hyperpolarized ¹²⁹Xe magnetic resonance imaging (¹²⁹Xe MRI) in pediatric asthma is poised to advance our understanding of disease mechanisms and pathophysiology in a disorder with diverse clinical phenotypes. ¹²⁹Xe MRI has not been investigated in a pediatric asthma cohort.

OBJECTIVE

We hypothesized that ¹²⁹Xe MRI is feasible and can demonstrate ventilation defects that relate to and predict clinical severity in a pediatric asthma cohort.

METHODS

Thirty-seven children (13 with severe asthma, 8 with mild/moderate asthma, 16 age-matched healthy controls) aged 6 to 17 years old were imaged with ¹²⁹Xe MRI. Ventilation defect percentage (VDP) and image reader score were calculated and compared with clinical measures at baseline and at follow-up.

RESULTS

Children with asthma had higher VDP (P = .002) and number of defects per image slice (defects/slice) (P = .0001) than children without asthma. Children with clinically severe asthma had significantly higher VDP and number of defects/slice than healthy controls. Children with asthma who had a higher number of defects/slice had a higher rate of health care utilization (r = 0.48; P = .03) and oral corticosteroid use (r = 0.43; P = .05) at baseline. Receiver-operating characteristic analysis demonstrated that the VDP and number of defects/slice were predictive of increased health care utilization, asthma, and severe asthma. VDP correlated with FEV₁ (r = -0.35; P = .04) and FEV₁/forced vital capacity ratio (r = -0.41; P = .01).

CONCLUSIONS

¹²⁹Xe MRI correlates with asthma severity, health care utilization, and oral corticosteroid use. Because delineation of clinical severity is often difficult in children, ¹²⁹Xe MRI may be an important biomarker for severity, with potential to identify children at higher risk for exacerbations and improve outcomes.

Small airway dysfunction and poor asthma control: a dangerous liaison

Asthma is a common chronic condition, affecting approximately 339 million people worldwide. The main goal of the current asthma treatment guidelines is to achieve clinical control, encompassing both the patient symptoms and limitations and the future risk of adverse asthma outcomes. Despite randomized controlled trials showing that asthma control is an achievable target, a substantial proportion of asthmatics remain poorly controlled in real life. The involvement of peripheral small airways has recently gained greater recognition in asthma, and many studies suggest that the persistent inflammation at these sites leads to small airway dysfunction (SAD), strongly contributing to a worse asthma control. Overall, the impulse oscillometry (IOS), introduced in the recent years, seems to be able to sensitively assess small airways, while conventional spirometry does not. Therefore, IOS may be of great help in characterizing SAD and guiding therapy choice. The aim of this article is to review the literature on SAD and its influence on asthma control, emphasizing the most recent evidence.

Prediction of postinfectious bronchiolitis obliterans prognosis in children

INTRODUCTION

The prognosis of postinfectious bronchiolitis obliterans (PIBO) has many implications, ranging between reduced quality of life and life-threatening complications. We evaluated the prognostic factors for PIBO using the baseline clinical characteristics of patients and built a prediction model for determining the prognoses of PIBO patients using the identified parameters.

METHODS

We included 47 PIBO patients who underwent spirometry and impulse oscillometry and followed them up for at least 1 year. A patient's prognosis was classified as poor if the patient experienced at least one of the following: persistent respiratory symptoms for more than 1 year, two or more instances of hospitalizations due to respiratory symptoms, or more than one intensive care unit admission.

RESULTS

The prognoses of 32/47 (68.1%) patients was good, while that of 15/47 (31.9%) was poor. Spirometry results showed significantly lower forced vital capacity (FVC), forced expiratory volume in the first second (FEV₁ ), forced expiratory flow at 25%-75% of FVC, and post-bronchodilator (BD) FEV₁ values in the poor prognosis group; chest computed tomography (CT) demonstrated more inflammatory bronchiolitis findings. We created a nomogram for predicting prognoses using post-BD FEV₁ and inflammatory bronchiolitis on chest CT. The area under the curve for the nomogram was 84.6% (95% confidence interval: 72.8%-96.4%).

CONCLUSIONS

PIBO patients with lower pulmonary function values and more findings of inflammatory bronchiolitis on initial examination have poor prognoses. The nomogram for predicting PIBO prognosis is easy to use and can be applied at the time of diagnosis.

The Case of a Janitorial Supervisor With Occupational Asthma Complicated by the Mixed Colonization of the Respiratory Tract by Candida albicans and Alternaria spp

Patients on immunosuppressant agents, including oral corticosteroids, are susceptible to fungal colonization despite being otherwise immunologically intact. This case report highlights a state-of-the-art biological modifier therapy for the complex care of a patient with refractory occupational asthma, allergic rhinitis, and mixed fungal colonization.

A dyspneic 38-year-old male janitor with steroid-dependent occupational asthma refractory to omalizumab therapy was colonized with Candida and Alternaria following a promotion to a managerial position in a moldy office. He was treated with itraconazole and systemic steroids. Pulmonary workup revealed moderate obstructive ventilatory defect, peripheral airway hyperresponsiveness, and eosinophilic airway inflammation. Three additional biological modifiers (reslizumab, benralizumab, and dupilumab) were administered to this patient. His asthma was ultimately controlled with reslizumab and dupilumab. Fractional exhaled nitric oxide (FeNO) normalized after dupilumab monotherapy, enabling the patient to taper off chronic prednisone therapy.

Various occupational exposures are crucial epidemiologic factors related to infection and go hand-in-glove with long-term prednisone treatment towards increasing susceptibility to fungal colonization. Steroid-sparing anti-interleukin-5 (IL-5) agents and dupilumab should be considered as alternative treatment options for patients, such as ours, with eosinophilic, prednisone-dependent asthma refractory to omalizumab therapy.

Lung function testing and inflammation markers for wheezing preschool children: A systematic review for the EAACI Clinical Practice Recommendations on Diagnostics of Preschool Wheeze

BACKGROUND

Preschool wheeze is highly prevalent; 30%-50% of children have wheezed at least once before age six. Wheezing is not a disorder; it is a symptom of obstruction in the airways, and it is essential to identify the correct diagnosis behind this symptom. An increasing number of studies provide evidence for novel diagnostic tools for monitoring and predicting asthma in the pediatric population. Several techniques are available to measure airway obstruction and airway inflammation, including spirometry, impulse oscillometry, whole-body plethysmography, bronchial hyperresponsiveness test, multiple breath washout test, measurements of exhaled NO, and analyses of various other biomarkers.

METHODS

We systematically reviewed all the existing techniques available for measuring lung function and airway inflammation in preschool children to assess their potential and clinical value in the routine diagnostics and monitoring of airway obstruction.

RESULTS

If applicable, measuring FEV1 using spirometry is considered useful. For those unable to perform spirometry, whole-body plethysmography and IOS may be useful. Bronchial reversibility to beta2-agonist and hyperresponsiveness test with running exercise challenge may improve the sensitivity of these tests.

CONCLUSIONS

The difficulty of measuring lung function and the lack of large randomized controlled trials makes it difficult to establish guidelines for monitoring asthma in preschool children.

Reliability of impulse oscillometry parameters in healthy children and in children with cystic fibrosis

INTRODUCTION & AIMS

Impulse oscillometry system (IOS) is an instrument developed to evaluate the mechanical lung properties. It has been reported that to analyse the exam in a proper way it is necessary to carry out more than one measure. However, studies addressing the standardisation are still scarce. The objective was to determine within trial reliability of three measures in IOS parameters in healthy children and children with cystic fibrosis (CF).

METHOD

Weight, height, body mass index, forced spirometric and the oscillometric parameters (resistance, respiratory impedance, respiratory reactance and resonance frequency) data were collected, in a way that all participants performed three IOS measures. To evaluate, the reproducibility was used the intraclass correlation coefficient [two-way mixed model, absolute agreement definition, ICC]. The response stability was appraised using the standard error of measurements (SEM) in three repetitions of the IOS in the healthy children group (HCG) and in the cystic fibrosis group (CFG).

RESULTS

About 95 subjects participated, in each group with a mean age of 10.89 ± 2.21 years old in the HCG and 9.73 ± 2.43 years old in the CFG, having been 41 and 43 boys and 54 and 52 girls, in the respectively group. In both groups, all IOS parameters evaluated in the three measures presented an ICC of 0.9, which is a high reproducibility.

CONCLUSION

The IOS parameters are reproducible for healthy children and CF children in three measures. However, according to the population studied, the performance of only one measure is sufficient to assess respiratory mechanics, whereas the SEM were low, except for Fres, in both groups.

Is Impulse Oscillometry System a Useful Method for the Evaluation and Follow-Up of Patients with Cystic Fibrosis?

Background: Although the impulse oscillometry system (IOS) is a noninvasive, easily accessible, well-tolerated, and alternative test, routine use of IOS in cystic fibrosis (CF) patients is not widespread. In our unit, IOS is routinely used for the evaluation and follow-up of patients with CF. We aimed to show that IOS may be utilized as a complement for measuring pulmonary function in CF patients. Materials and Methods: Retrospective data collection and analysis of pulmonary function tests on CF patients followed at our center between January 1, 2018 and February 1, 2019. IOS and spirometry data were compared as correlated with patients' clinical exacerbation, treatment response, bronchodilator response, and trends during follow-up intervals. Results: There was a significant correlation between spirometry and IOS parameters in 70 patients. In exacerbation, Z5, R5-R10, AX, Fres, and delta R5-R20 were significantly increased and X5-X20 was significantly decreased compared with baseline in 25 patients. After treatment, IOS parameters were observed to return to baseline values. In the evaluation of bronchodilator response in 33 patients, significant changes in IOS (decrease in Z5, R5-R10, AX, Fres, and delta R5-R20, and increase in X5-X10) and in spirometry [increase in forced expiratory volume in 1 s (FEV1) and forced expiratory flow during the middle half of forced vital capacity (FEF_25-75)] were found after bronchodilator. While there was no significant difference between spirometry values in follow-up visits in 31 patients, there was a significant increase in Z5% and R5%-R20%. Unlike other studies, there was a significant correlation between clinical scores and IOS. Conclusions: These results show that although IOS is not the gold standard method such as spirometry, it is an alternative method that can be used successfully in the evaluation and follow-up of CF patients. Clinical Trials.gov ID: 99166796-050.06.04.

Impact of prenatal and postnatal household air pollution exposure on lung function of 2-year old Nigerian children by oscillometry

RATIONALE

Lung function is adversely affected by exposure to household air pollution (HAP). Studies investigating the impact of prenatal and postnatal HAP exposure on early childhood lung development are limited, especially from Sub-Saharan Africa.

OBJECTIVE

We used oscillometry to investigate the impact on lung function of prenatal and postnatal HAP exposure of children born to Nigerian women who participated in a randomized controlled cookstove intervention trial.

METHODS

We performed oscillometric measurements (R: airway resistance; X: airway reactance; Fres: resonant frequency; AX: reactance area) in 223 children starting at age of 2 years (ethanol stove, n = 113; firewood/kerosene, n = 110). Personal exposure monitoring assessed mothers' prenatal exposure to particulate matter less than 2.5 μm in aerodynamic diameter (PM_2.5). Postnatal HAP exposure was measured by determining household PM_2.5 levels. We employed linear regression analysis to examine the association of prenatal and postnatal HAP exposures with children's lung function. Models were adjusted for age, gender, weight, height, group (intervention or control), birthweight and gestational age.

RESULTS

Mean age of the children was 2.9 years (standard deviation = 0.3); 120 were boys (53.8%) and 103 were girls (46.2%). Higher postnatal PM_2.5 exposures were significantly associated with higher airway reactance at 5 Hz (X5 Hz; p = 0.04) in adjusted models. There were no significant associations between prenatal or postnatal PM_2.5 exposure levels and other oscillometry parameters in adjusted regression analysis.

CONCLUSIONS

This is the first study to use oscillometry to explore the relationship between HAP exposure and lung function in children as young as 2 years. The findings provide some evidence that increased postnatal HAP exposure may result in poorer lung function in children, although larger studies are needed to confirm observed results. This study indicates that oscillometry is a low-cost and effective method to determine lung function in early childhood.

The diagnosis of asthma. Can physiological tests of small airways function help?

Asthma is a common, chronic, and heterogeneous disease with a global impact and substantial economic costs. It is also associated with significant mortality and morbidity and the burden of undiagnosed asthma is significant. Asthma can be difficult to diagnose as there is no gold standard test and, while spirometry is central in diagnosing asthma, it may not be sufficient to confirm or exclude the diagnosis. The most commonly reported spirometric measures (forced expiratory volume in one second (FEV₁) and forced vital capacity assess function in the larger airways. However, small airway dysfunction is highly prevalent in asthma and some studies suggest small airway involvement is one of the earliest disease manifestations. Moreover, there are new inhaled therapies with ultrafine particles that are specifically designed to target the small airways. Potentially, tests of small airways may more accurately diagnose early or mild asthma and assess the response to treatment than spirometry. Furthermore, some assessment techniques do not rely on forced ventilatory manoeuvres and may, therefore, be easier for certain groups to perform. This review discusses the current evidence of small airways tests in asthma and future research that may be needed to further assess their utility.

What Is Most Suitable for Children With Cystic Fibrosis-The Relationship Between Spirometry, Oscillometry, and Multiple Breath Nitrogen Washout

INTRODUCTION

In cystic fibrosis (CF), pathological lung changes begin early in life. The technological progress currently gives many diagnostic possibilities. However, pulmonary function testing in children remains problematic.

OBJECTIVES

Our study aimed to correlate the results of impulse oscillometry (IOS) with those of multiple breath nitrogen washout (MBNW) in our pediatric CF population. We also compared those parameters between the groups with and without spirometric features of obturation.

METHODS

We collected 150 pulmonary function test sets, including spirometry, IOS, and MBNW in patients with CF aged 12.08 ± 3.85 years [6-18]. The study group was divided into two subgroups: IA (without obturation) and IB (with obturation). We also compared Sacin, Scond, and oscillometry parameters of 20 patients aged 14-18 years who reached the appropriate tidal volume (VT) during MBNW.

RESULTS

Statistical analysis showed a negative correlation between lung clearance index (LCI) and spimoetric parameters. Comparison of subgroups IA (n = 102) and IB (n = 48) indicated a statistically significant difference in LCI (p < 0.001) and FEV1z-score (p < 0.001), FEV1% pred (p < 0.001), MEF25z-score (p < 0.001), MEF50 z-score (p < 0.001), MEF75 z-score (p < 0.001), R5% pred (p < 0.05), and R20% pred (p < 0.01). LCI higher than 7.91 was found in 75.33% of the study group, in subgroup IB-91.67%, and IA-67.6%.

CONCLUSIONS

LCI derived from MBNW may be a better tool than IOS for assessing pulmonary function in patients with CF, particularly those who cannot perform spirometry.

Assessment of pulmonary function by impulse oscillometry and spirometry in children with type 1 diabetes mellitus

AIM

To assess the lung functions with impulse oscillometry (IOS) and spirometry in children with type 1 diabetes mellitus (T1DM).

METHODS

Fifty-one children with T1DM, and sex- and age-matched 53 healthy control (HC) subjects were included in this study. Demographic, clinical, and laboratory characteristics of the subjects were recorded and their pulmonary functions were analyzed by IOS and spirometry.

RESULTS

In IOS, zR5, zR10, and zR20 levels were higher in children with T1DM compared with HCs (P = .019, P = .017, and P = .002, respectively). In spirometry, zFEF75 and zFEF25-75 were lower in children with T1DM compared with HCs (P = .025, P = .001, respectively). In IOS, zR5-20 (P = .008, P = .005, respectively) and zAX (P = .013, P = .009, respectively) were significantly lower in good-controlled group compared with moderate- and poor-controlled group. In spirometry, zFEF25-75 was significantly higher in good-controlled group compared with moderate- and poor-controlled group (P = .005, P = .009, respectively). HbA1c was positively correlated with zR5-20 value (r = .339; P = .017) in male children with T1DM. The duration of the disease was positively correlated with zR5-20 (r = .290; P = .043) and zFres (r = .358; P = .010). According to the receiver operating characteristic curve analysis to estimate optimal cut-offs to discriminate good control level of T1DM (HbA1c < 7%), a zR5-20 ≤ 2.28 demonstrated a 75.0% sensitivity and 82.9% specificity, with an area under the curve of 0.805 ([confidence interval, 0.615-0.995]; P = .007).

CONCLUSIONS

This study showed subclinical impairment of lung functions which is associated with disease duration and the degree of metabolic control in children with T1DM.

Airway mechanics after withdrawal of a leukotriene receptor antagonist in children with mild persistent asthma: Double-blind, randomized, cross-over study

BACKGROUND

To determine the response of airway mechanics and the changes in asthma symptoms to stepping down of leukotriene receptor antagonist (LTRA) therapy.

METHODS

Thirty children (mean age: 7.1 years) with mild, well-controlled, and persistent asthma who took LTRA as maintenance treatment were randomized into a double-blind, placebo-controlled, cross-over study. Each group received an LTRA (montelukast) or placebo daily for 2 weeks, followed by a 1-week washout period, and then the alternate treatment for 2 weeks. Spirometry and impulse oscillation system (IOS) measurements before and after four puffs of salbutamol inhalation, fractional exhaled nitric oxide (FeNO), and the childhood asthma control test (C-ACT) were evaluated at baseline, the end of placebo treatment, and the end of LTRA treatment.

RESULTS

Changes of FEV₁ /FVC (p = .113) and FEV₁ (p = .109) from baseline to posttreatment did not differ significantly between the placebo and montelukast groups. In the placebo group, prebronchodilator (pre-) FEV₁ /FVC was decreased (83% vs. 86%) and bronchodilator response (BDR) in FEV₁ was diminished (10.7% vs. 6.4%) at posttreatment compared with baseline. However, the montelukast group had no significant changes in pre-FEV₁ /FVC (p = .865) and BDR in FEV₁ (p = .461). In addition, compared with the montelukast group, the placebo group showed no significant changes in Rrs5 (total airway resistance), Rrs5-20 (peripheral airway resistance), FeNO, and symptoms by the C-ACT.

CONCLUSION

In children with well-controlled mild persistent asthma, changes in spirometry, IOS, FeNO, and C-ACT results did not differ between the placebo and montelukast groups within 2 weeks.

Physiological tests of small airways function in diagnosing asthma: a systematic review

BACKGROUND

Asthma is a common, heterogeneous disease that is characterised by chronic airway inflammation and variable expiratory airflow limitation. Current guidelines use spirometric measures for asthma assessment. This systematic review aimed to assess whether the most commonly reported tests of small airways function could contribute to the diagnosis of asthma.

METHODS

Standard systematic review methodology was used, and a range of electronic databases was searched (Embase, MEDLINE, CINAHL, CENTRAL, Web of Science, DARE). Studies that included physiological tests of small airways function to diagnose asthma in adults were included, with no restrictions on language or date. The risk of bias and quality assessment tools used were Agency for Healthcare Research and Quality tool for cross-sectional studies and Quality Assessment of Diagnostic Accuracy Studies 2 for diagnostic test accuracy (DTA) studies.

RESULTS

7072 studies were identified and 10 studies met review criteria. 7 included oscillation techniques and 5 included maximal mid-expiratory flow (MMEF). Studies were small and of variable quality. In oscillometry, total resistance (R5) and reactance at 5 Hz (X5) was altered in asthma compared with healthy controls. The percentage predicted of MMEF was lower in patients with asthma compared with controls in all studies and lower than the % predicted forced expiratory volume in 1 s. In DTA of oscillometry, R5 showed a sensitivity between 69% and 72% and specificity between 61% and 86%.

CONCLUSION

There were differences in the results of physiological tests of small airway function in patients with asthma compared with controls. However, studies are small and heterogeneous. Further studies are needed to assess the effectiveness of these tests on a larger scale, including studies to determine which test methodology is the most useful in asthma.

Small Airway Disease in Pediatric Asthma: the Who, What, When, Where, Why, and How to Remediate. A Review and Commentary

Asthma affects all portions of the airways. Small airways, however, comprise a substantial component of the conducting lung air flow. In asthma, inflammatory processes can affect the whole respiratory tract, from central to peripheral/small airways. The emphasis in adult and pediatric respiratory disease clinics is to focus on large airway obstruction and reversibility. This information, although valuable, underemphasizes a large portion of the conduction airway of asthmatics. Standard descriptions of asthma management focus on a multiple medication approaches. We particularly focused on the management of asthma in the international guidelines for the Global Initiative for Asthma (GINA). Overall, however, minimal attention is placed on the small airway pool in asthma medical management. We took the opportunity to thoroughly review and present specific data from the adult asthma literature which supported the concept that small airway abnormalities may play a role in the pathogenesis and clinical expression of asthma. Based on the conclusions of the adult asthma literature, we here present a thorough review of the literature as it relates to small airway disease in children with asthma. We used, collectively, individual data sources of data to expand the information available from standard diagnostic techniques, especially spirometry, in the evaluation of small airway disease. As the pharmacological approaches to moderate to severe asthma are advancing rapidly into the realm of biologics, we sought to present potential pharmacological options for small airway dysfunction in pediatrics prior to biological modifier intervention.

Oral Immunotherapy for Food Allergy-a US Regulatory Perspective

The recent approval of Palforzia for treatment of peanut allergy by the US Food and Drug Administration (USFDA) predicts that additional products for oral immunotherapy (OIT) are on the horizon. In this article, the authors review the legal framework by which the USFDA regulates products for OIT of food allergy and the clinical data that demonstrated that the safety and effectiveness profile of Palforzia supported approval and conclude with a discussion of oral food challenge (OFC) as a clinical endpoint to demonstrate safety and effectiveness of OIT products.

Investigating outcome measures for assessing airway clearance techniques in adults with cystic fibrosis: protocol of a single-centre randomised controlled crossover trial

Introduction

Airway clearance techniques (ACTs) are a gold standard of cystic fibrosis management; however, the majority of research evidence for their efficacy is of low standard; often attributed to the lack of sensitivity from outcome measures (OMs) used historically. This randomised controlled trial (RCT) investigates these standard OMs (sputum weight, forced expiratory volume in 1 s) and new OMs (electrical impedance tomography (EIT), multiple breath washout (MBW) and impulse oscillometry (IOS)) to determine the most useful measures of ACT.

Methods and analysis

This is a single-centre RCT with crossover design. Participants perform MBW, IOS and spirometry, and then are randomised to either rest or supervised ACT lasting 30–60 min. MBW, IOS and spirometry are repeated immediately afterwards. EIT and sputum are collected during rest/ACT. On a separate day, the OMs are performed with the other intervention. Primary endpoint is difference in change in OMs before and after ACT/rest. Sample size was calculated with 80% power and significance of 5% for each OM (target n=64).

Ethics and dissemination

Ethics approval was gained from the London–Chelsea Research Ethics Committee (reference 16/LO/0995, project ID 154635). Dissemination will involve scientific conference presentation and publication in a peer-reviewed journal.

Trial registration numbers

ISRCTN11220163 and NCT02721498.