Reactance Curve Research Articles

Early Respiratory Mechanics Alterations in Smokers: Correlative Analysis of the Forced Oscillation Technique and Computerized Spirometry.

Smoking remains a significant public health concern, associated with a myriad of diseases, including chronic obstructive pulmonary disease, cardiovascular diseases, and various cancers. While spirometry is the gold standard for assessing lung function, it may lack sensitivity in detecting early changes in respiratory mechanics induced by smoking. This study aims to evaluate the clinical potential of the forced oscillation technique (FOT) in detecting early changes in the respiratory mechanics of smokers and its correlation with computerized spirometry. This study aims to bridge this gap by investigating the utility of FOT, a noninvasive method requiring less patient cooperation, in detecting early changes in respiratory mechanics among smokers. The study was conducted on 36 healthy nonsmokers and 36 healthy smokers. We conducted FOT and computerized spirometry, comparing these parameters between the two groups and finding correlations between FOT and spirometry parameters. A statistically significant difference was found across different smoking indices for computerized spirometer parameters forced vital capacity (FVC) and forced expiratory volume in one second (FEV1), marginal significance for peak expiratory flow, and no statistically significant for FEV1/FVC ratio andforced expiratory flow between 25 and 75% of vital capacity. We did not find statistically significant differences across different smoking indexes for FOT parameters,resistance at 5 Hz (R5), resistance at 20 Hz (R20),resistance difference between 5 and 20 Hz (R5-20), reactance at 5 Hz, reactance at 20 Hz (X20), area under the reactance curve (AX), resonance frequency (Fres), and resistance at resonance. However, Fres had shown marginal significance. The study revealed notable negative correlations between airway resistance parameters (such as R5 and R5-20) and the FEV1/FVC ratio, and significant negative correlations were also identified between airway reactance parameters (AX and Fres) and FEV1. The results emphasize that FVC and FEV1 appear to be early markers of damage. The smoking index (1-70) did not significantly influence the FOT parameters in the examined population with the Quark i2m FOT machine (COSMED, Italy). Nevertheless, marginal significance in FOT Fres parameters suggests potential alterations with longer smoking durations, warranting further investigation. Also, significant negative correlations were found between the FOT and pulmonary function test parameters.

Peripheral Airways Dysfunction Measured by Oscillometry Differentiates Asthma from Inducible Laryngeal Obstruction

Inducible laryngeal obstruction (ILO, also called vocal cord dysfunction) can be difficult to distinguish clinically from asthma. Limited studies have explored the use of respiratory oscillometry to detect changes unique to ILO, but more study is needed to determine if routine oscillometry can differentiate these two clinical entities. Determine if impedance variables measured on routine oscillometry over tidal breathing vary between individuals with asthma and ILO. Subjects with asthma and ILO were recruited to participate in a single-center, observational study at the University of Rochester Medical Center. Oscillometry measurements were obtained over tidal breathing according to technical standards. Exploratory oscillometry variables were analyzed, as well as standard oscillometry variables including measures of peripheral airways dysfunction. 25 subjects (12 with asthma and 13 with ILO) were recruited and included in the analysis. Measures of peripheral airways dysfunction including frequency dependence of resistance (R5-R20), area under the reactance curve (AX), and reactance at 5Hz (X5) were significantly more abnormal in asthma subjects compared to ILO subjects (p=0.039, p=0.008, and p=0.0327 respectively). Resistance at 5Hz (R5) was not statistically different between asthma and ILO (p=0.301). Exploratory variables, including inspiratory impedance and the standard deviation of impedance, were not significantly different between asthma and ILO. Measures of peripheral airways dysfunction by oscillometry were significantly different in subjects with asthma compared to ILO and more significant in subjects with poor asthma control. There were no exploratory oscillometry variables that were significantly different between ILO and asthma.

Correlation of Impulse oscillometry system indices with conventional pulmonary function tests in patients with obstructive pulmonary ventilation dysfunction

Objective: To investigate the correlation between impulse oscillometry system examination indicators and conventional pulmonary ventilation function. Methods: The pulmonary ventilation function data of 10 883 patients from January 1, 2020 to December 31, 2022 at Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology were included. The one-second rate [ratio of forced expiratory volume in the first second (FEV1) to forced vital capacity (FVC)] measured as a percentage of the predicted value was ≥92% for the control group (n=3 478) and <92% for the pulmonary obstruction group (n=7 405). The obstruction group was subdivided into five groups according to the degree of pulmonary dysfunction: mild group (n=3 938),moderate group (n=1 142),oderate-severe group (n=917),severe group (n=737),and extremely severe group (n=671). Conventional pulmonary ventilatory function FVC, FEV1, one-second rate, and forced expired flow at 50% of FVC (MEF50%), forced expired flow at 75% FVC (MEF25%), maximal mid-expiratory flow (MMEF), peak expiratory flow (PEF), and pulsed oscillation pulmonary function test were detected in both groups of patients. Impedance at 5 Hz (Z5) means total respiratory resistance, resistance at 5 Hz (R5) means total airway resistance, reactance at 5 Hz (X5) indicates the elastic recoil of the peripheral airways, and resistance at 20 Hz (R20) represents resistance of the central airways. R5-R20 reflects resistance in the small airways. Additionally, peripheral resistance (Rp), respiratory resonance frequency (Frex), and area under the reactance curve (Ax) were also measured. Correlation between the indicators of the two groups and the sensitivity and specificity of the impulse oscillometry system parameters for the diagnosis of obstructive pulmonary ventilation dysfunction were analyzed. Results: Pulmonary function force expiratory volume in the first second as a percentage of predicted value (FEV1%Pre) [80.10 (54.95,97.10)%],one-second rate [62.43(48.67, 67.02)%],MEF50% [1.33 (0.62,1.97)L/s],MEF25% [0.28 (0.17,0.41)L/s], MMEF [0.85 (0.43,1.29)L/s],and PEF [5.64 (3.73,7.50)]L/s in the obstruction group were significantly lower than those in the control group (P<0.05). The differences within the subgroups of the obstruction group were also significant (P<0.05). Pulsed oscillation Z5 [0.42 (0.33,0.55)kPa·L-1·s-1],Rp [0.25 (0.20,0.45)kPa·L-1·s-1], R5 [0.39 (0.31,0.49)kPa·L-1·s-1], R20 [0.28 (0.24,0.34)kPa·L-1·s-1], R5-R20 [0.09 (0.05,0.17)kPa·L-1·s-1],Frex [16.32 (13.07,20.84)Hz], and Ax [0.67 (0.28,1.64)] indices in the obstruction group were significantly higher than those in the control group. X5 [-0.14 (-0.23, -0.10)kPa·L-1·s-1] was significantly lower than that in the control group (P<0.05). Z5, Rp, X5, R5, R5-R20, Frex, and Ax were statistically significant between different degrees of obstruction in the obstruction group (P<0.05). The impulse oscillometry system parameters Z5, Rp, R5, R20, R5-20, Frex, and Ax were negatively correlated with the indices of conventional pulmonary ventilation (r=-0.21-0.68, P<0.05), and the parameter X5 was positively correlated with the indices of conventional pulmonary ventilation (r=0.41-0.68, P<0.05). The pulsed oscillation pulmonary function test parameters X5 (58.60%-95.68%) and Ax (57.08%-98.06%) presented the best sensitivity; X5 (86.29%-98.82%), Frex (86.69%-94.71%), and Ax (88.10%-98.53%) displayed the best specificity; and R20 presented the worst sensitivity and specificity. The sensitivity and specificity were slightly better in female patients than in male patients. Conclusion: The technical parameters of the impulse oscillometry system showed significant correlation with relevant indices of conventional pulmonary ventilation function detection. These well reflect the changes of different degrees of pulmonary ventilation function and have greater significance for reference in evaluating the degree of pulmonary function impairment.

A Comparative Observational Study of the Diagnostic Utility of Impulse Oscillometry Versus Spirometry in Obstructive Airway Diseases.

Background Obstructive airway diseases, including asthma and chronic obstructive pulmonary disease (COPD), significantly impact respiratory function, making accurate diagnosis and differentiation essential for proper management. While spirometry is the gold standard for assessing lung function, impulse oscillometry (IOS) has emerged as a complementary tool, especially when spirometry results are inconclusive. This study aimed to compare the diagnostic utility of IOS with spirometry in patients with obstructive airway diseases and evaluate the correlation between these two methods. Methods A comparative observational study was conducted over 18 months at a tertiary care hospital in central India, including 130 patients (65 with asthma and 65 with COPD). Diagnostic evaluations using spirometry and IOS were performed before and after bronchodilator administration. Spirometry parameters assessed were forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and FEV1/FVC ratio, while IOS parameters evaluated included resistance at 5 Hz (R5), resistance at20Hz (R20), resonant frequency(Fres), reactance at 5 Hz (X5), and the area under the reactance curve (AX). Statistical analysis was conducted using IBM SPSS version 27.0 (IBM Corp., Armonk, USA) and GraphPad Prism version 7.0 (Dotmatics, Boston, USA). Results Significant differences were observed in spirometry parameters between asthma and COPD groups, with asthma patients showing better lung function (FEV1, FVC, and FEV1/FVC; p<0.05). No significant differences were found in IOS parameters between the groupsexcept for a correlation between FEV1 (%) and IOS measurements in the asthma group. Spirometry demonstrated superior sensitivity in identifying airway obstruction compared to IOS. However, IOS was more effective in detecting peripheral airway obstruction in asthma patients, with 22 out of 65 (33.85%) asthma patients showing peripheral airway obstruction compared to six out of 65 (9.23%) COPD patients (p=0.001). Conclusion While spirometry remains the primary diagnostic tool for assessing obstructive airway diseases, IOS is a valuable adjunct, particularly for detecting peripheral airway involvement in asthma patients. Combining spirometry and IOS enhances diagnostic accuracy and provides a more comprehensive assessment of lung function in patients with asthma and COPD.

Intra-breath changes in respiratory mechanics are sensitive to history of respiratory illness in preschool children: the SEPAGES cohort

BackgroundIntra-breath oscillometry has been proposed as a sensitive means of detecting airway obstruction in young children. We aimed to assess the impact of early life wheezing and lower respiratory tract illness on lung function, using both standard and intra-breath oscillometry in 3 year old children.MethodsHistory of doctor-diagnosed asthma, wheezing, bronchiolitis and bronchitis and hospitalisation for respiratory problems were assessed by questionnaires in 384 population-based children. Association of respiratory history with standard and intra-breath oscillometry parameters, including resistance at 7 Hz (R7), frequency-dependence of resistance (R7 − 19), reactance at 7 Hz (X7), area of the reactance curve (AX), end-inspiratory and end-expiratory R (ReI, ReE) and X (XeI, XeE), and volume-dependence of resistance (ΔR = ReE-ReI) was estimated by linear regression adjusted on confounders.ResultsAmong the 320 children who accepted the oscillometry test, 281 (88%) performed 3 technically acceptable and reproducible standard oscillometry measurements and 251 children also performed one intra-breath oscillometry measurement. Asthma was associated with higher ReI, ReE, ΔR and R7 and wheezing was associated with higher ΔR. Bronchiolitis was associated with higher R7 and AX and lower XeI and bronchitis with higher ReI. No statistically significant association was observed for hospitalisation.ConclusionsOur findings confirm the good success rate of oscillometry in 3-year-old children and indicate an association between a history of early-life wheezing and lower respiratory tract illness and lower lung function as assessed by both standard and intra-breath oscillometry. Our study supports the relevance of using intra-breath oscillometry parameters as sensitive outcome measures in preschool children in epidemiological cohorts.

Lung function changes in children exposed to mine fire smoke in infancy.

Chronic, low-intensity air pollution exposure has been consistently associated with reduced lung function throughout childhood. However, there is limited research regarding the implications of acute, high-intensity air pollution exposure. We aimed to determine whether there were any associations between early life exposure to such an episode and lung growth trajectories. We conducted a prospective cohort study of children who lived in the vicinity of the Hazelwood coalmine fire. Lung function was measured using respiratory oscillometry. Z-scores were calculated for resistance (R5 ) and reactance at 5 Hz (X5 ) and area under the reactance curve (AX). Two sets of analyses were conducted: (i) linear regression to assess the cross-sectional relationship between post-natal exposure to mine fire-related particulate matter with an aerodynamic diameter of less than 2.5 micrometres (PM2.5 ) and lung function at the 7-year follow-up and (ii) linear mixed-effects models to determine whether there was any association between exposure and changes in lung function between the 3- and 7-year follow-ups. There were no associations between mine fire-related PM2.5 and any of the lung function measures, 7-years later. There were moderate improvements in X5 (β: -0.37 [-0.64, -0.10] p = 0.009) and AX (β: -0.40 [-0.72, -0.08] p = 0.014), between the 3- and 7-year follow-ups that were associated with mean PM2.5 , in the unadjusted and covariance-adjusted models. Similar trends were observed with maximum PM2.5 . There was a moderate improvement in lung stiffness of children exposed to PM2.5 from a local coalmine fire in infancy, consistent with an early deficit in lung function at 3-years after the fire that had resolved by 7-years.

Small airway dysfunction measured by impulse oscillometry is associated with exacerbations and poor symptom control in patients with asthma treated in a tertiary hospital subspecialist airways disease clinic.

Small airways dysfunction contributes to asthma pathophysiology and clinical outcomes including exacerbations and asthma control. Respiratory oscillometry is a simple, non-invasive and effort independent lung function test that provides vital information about small airway function. However, interpretation and clinical utility of respiratory oscillometry has been in part limited by lack of agreed parameters and the respective cutoffs. The aim of this study was to determine the prevalence of small airways dysfunction based on published impulse oscillometry (IOS) definition in patients with asthma referred to a tertiary asthma clinic and the extent to which it correlates with asthma clinical outcomes. We retrospectively reviewed the medical records of all patients with asthma managed in the severe asthma clinic between January 2019 and December 2022 who underwent routine lung function tests with oscillometry and spirometry. Small airways dysfunction was determined from various published IOS parameter cutoffs, and the data were analysed to determine correlations between IOS parameters and asthma outcomes. Amongst the 148 patients, the prevalence of small airways dysfunction ranged from 53% to 78% depending on the defining oscillometry parameter. All oscillometry parameters correlated with the severity of airflow obstruction (FEV1% predicted, p < 0.001). Several oscillometry parameters correlated with asthma symptom burden, the strongest correlation was seen for frequency dependent resistance (R5-R20) with scores of Asthma Control Questionnaire (ACQ6) (Spearman's rank coefficient 0.213, p = 0.028) and Asthma Control Test (ACT) (Spearman's rank coefficient -0.248, p = 0.012). R5-R20 was predictive of poor asthma control defined by ACQ6 >1.5 (OR 2.97, p = 0.022) or ACT <20 (OR 2.44, p = 0.055). Small airways dysfunction defined by R5-R20 and area under the reactance curve (AX) also significantly increases asthma exacerbation risk (OR 2.60, p = 0.02 and OR 2.31, p = 0.03 respectively). Respiratory oscillometry is a sensitive measure of small airways dysfunction that should complement spirometry in the routine assessment of asthma. Small airways dysfunction is highly prevalent in patients with asthma referred to a tertiary asthma clinic. R5-R20 was the metric most predictive in identifying patients at risk of asthma exacerbations and poor asthma control.

Post-COVID changes in lung function 6 months after veno-venous extracorporeal membrane oxygenation: a prospective observational clinical trial.

Severe coronavirus disease 2019 (COVID-19) may require veno-venous extracorporeal membrane oxygenation (V-V ECMO). While V-V ECMO is offered in severe lung injury to COVID-19, long-term respiratory follow-up in these patients is missing. Therefore, we aimed at providing comprehensive data on the long-term respiratory effects of COVID-19 requiring V-V ECMO support during the acute phase of infection. In prospective observational cohort study design, patients with severe COVID-19 receiving invasive mechanical ventilation and V-V ECMO (COVID group, n = 9) and healthy matched controls (n = 9) were evaluated 6 months after hospital discharge. Respiratory system resistance at 5 and 19 Hz (R5, R19), and the area under the reactance curve (AX5) was evaluated using oscillometry characterizing total and central airway resistances, and tissue elasticity, respectively. R5 and R19 difference (R5-R19) reflecting small airway function was also calculated. Forced expired volume in seconds (FEV1), forced expiratory vital capacity (FVC), functional residual capacity (FRC), carbon monoxide diffusion capacity (DLCO) and transfer coefficient (KCO) were measured. The COVID group had a higher AX5 and R5-R19 than the healthy matched control group. However, there was no significant difference in terms of R5 or R19. The COVID group had a lower FEV1 and FVC on spirometry than the healthy matched control group. Further, the COVID group had a lower FRC on plethysmography than the healthy matched control group. Meanwhile, the COVID group had a lower DLCO than healthy matched control group. Nevertheless, its KCO was within the normal range. Severe acute COVID-19 requiring V-V ECMO persistently impairs small airway function and reduces respiratory tissue elasticity, primarily attributed to lung restriction. These findings also suggest that even severe pulmonary pathologies of acute COVID-19 can manifest in a moderate but still persistent lung function impairment 6 months after hospital discharge. NCT05812196.

Clinical impact of obesity on oscillometry lung mechanics in adults with asthma

BackgroundIn the year 2035, projections have estimated that 5% of the Scottish population will be morbidly obese defined as a body mass index (BMI) greater than or equal to 40 kg/m2. Airway oscillometry is an effort-independent test akin to bronchial sonar which measures resistance and compliance. ObjectiveTo evaluate the impact of obesity on lung mechanics using oscillometry. MethodsClinical data for 188 patients with respiratory physician–diagnosed moderate-to-severe asthma were retrospectively collected and analyzed. ResultsObesity (BMI 30-39.9 kg/m2) and morbid obesity (BMI ≥ 40 kg/m2) were associated with a significantly worse heterogeneity of peripheral resistance between 5 Hz and 20 Hz and peripheral compliance as low-frequency reactance at 5 Hz and area under the reactance curve, as compared with normal weight (BMI 18.5-24.9 kg/m2). Cluster analysis incorporating oscillometry identified a patient cohort who was older, obese, and female with combined impairment of spirometry and oscillometry coupled with more frequent severe exacerbations. ConclusionObesity is associated with worse peripheral airway dysfunction in moderate-to-severe asthma, including a patient cluster who was older, obese, and female with more frequent exacerbations.

Prenatal exposure to synthetic phenols and phthalates and child respiratory health from 2 to 36 months of life

Exposure to phthalates and synthetic phenols is ubiquitous. Some of them are suspected to impact child respiratory health, although evidence still remains insufficient. This study investigated the associations between prenatal exposure to phthalates and phenols, individually and as a mixture, and child respiratory health assessed by objective lung function measures since 2 months of age. Among 479 mother-child pairs from the SEPAGES cohort, 12 phenols, 13 phthalate and 2 non-phthalate plasticizer metabolites were measured in 2 pools including each 21 urine samples collected at the 2nd and 3rd pregnancy trimesters. Lung function was measured at 2 months using tidal breathing flow-volume loops and nitrogen multiple-breath washout, and at 3 years using oscillometry. Asthma, wheezing, bronchitis and bronchiolitis were assessed by repeated questionnaires. A cluster-based analysis was applied to identify exposure patterns to phenols and phthalates. Adjusted associations between clusters as well as each individual exposure biomarker and child respiratory health were estimated by regression models. We identified four prenatal exposure patterns: 1) low concentrations of all biomarkers (reference, n = 106), 2) low phenols–moderate phthalates (n = 162), 3) high concentrations of all biomarkers except bisphenol S (n = 109), 4) high parabens–moderate other phenols–low phthalates (n = 102). At 2 months, cluster 2 infants had lower functional residual capacity and tidal volume and higher ratio of time to peak tidal expiratory flow to expiratory time (tPTEF/tE) and cluster 3 had lower lung clearance index and higher tPTEF/tE. Clusters were not associated with respiratory health at 3 years but in the single-pollutant models, parabens were associated with increased area of the reactance curve, bronchitis (methyl, ethyl parabens) and bronchiolitis (propyl paraben). Our results suggested that prenatal exposure to mixtures of phthalates reduced lung volume in early life. Single exposure analyses suggested associations of parabens with impaired lung function and increased risk of respiratory diseases.

No association between in utero exposure to emissions from a coalmine fire and post-natal lung function

Background and objectiveStudies linking early life exposure to air pollution and subsequent impaired lung health have focused on chronic, low-level exposures in urban settings. We aimed to determine whether in utero exposure to an acute, high-intensity air pollution episode impaired lung function 7-years later.MethodWe conducted a prospective cohort study of children who lived in the vicinity of a coalmine fire. Respiratory function was measured using the forced oscillation technique (FOT). Z-scores for resistance at 5 Hz (R5), reactance at 5 Hz (X5) and area under the reactance curve (AX) were calculated. Two sets of analyses were conducted to address two separate questions: (1) whether mine fire exposure (a binary indicator; conceived after the mine fire vs in utero exposed) was associated with the respiratory Z-scores; (2) whether there was any dose–response relationship between fire-related PM2.5 exposure and respiratory outcomes among those exposed.ResultsAcceptable lung function measurements were obtained from 79 children; 25 unexposed and 54 exposed in utero. Median (interquartile range) for daily average and peak PM2.5 for the exposed children were 4.2 (2.6 – 14.2) and 88 (52—225) µg/m3 respectively. There were no detectable differences in Z-scores between unexposed and exposed children. There were no associations between respiratory Z-scores and in utero exposure to PM2.5 (daily average or peak).ConclusionThere was no detectable effect of in utero exposure to PM2.5 from a local coalmine fire on post-natal lung function 7-years later. However, statistical power was limited.

Peripheral Airway Dysfunction in Obesity and Obese Asthma

The purpose of this study was to investigate physiological phenotypes of asthma in obesity. Do physiological responses during bronchoconstriction distinguish different groups of asthma in people with obesity, and also differentiate from responses simply related to obesity? Cross-sectional study of people with obesity (31 with asthma and 22 without lung disease). Participants underwent methacholine challenge testing with measurement of spirometry and respiratory system impedance by oscillometry. Participants had class III obesity (BMI, 46.7 ± 6.6kg/m2 in control subjects and 47.2 ± 8.2kg/m2 in people with asthma). Most participants had significant changes in peripheral airway impedance in response to methacholine: in control subjects, resistance at 5Hz measured by oscillometry increased by 45%± 27%and area under the reactance curve (AX) by 268%± 236%in response to 16mg/mL methacholine; in people with asthma, resistance at 5Hz measured by oscillometry increased by 52%± 38%and AX by 361%± 295%in response to provocation concentration producing a 20% fall in FEV1 dose of methacholine. These responses suggest that obesity predisposes to peripheral airway reactivity. Two distinct groups of asthma emerged based on respiratory system impedance: one with lower reactance (baseline AX, 11.8; interquartile range, 9.9-23.4cm H2O/L) and more concordant bronchoconstriction in central and peripheral airways; the other with high reactance (baseline AX, 46.7; interquartile range, 23.2-53.7cm H2O/L) and discordant bronchoconstriction responses in central and peripheral airways. The high reactance asthma group included only women, and reported significantly more gastroesophageal reflux disease, worse chest tightness, more wheeze, and more asthma exacerbations than the low reactance group. Peripheral airway reactivity detected by oscillometry is common in obese control subjects and obese people with asthma. There is a subgroup of obese asthma characterized by significant peripheral airway dysfunction by oscillometry out of proportion to spirometric airway dysfunction. This peripheral dysfunction represents clinically significant respiratory disease not readily assessed by spirometry.

Study on environmental corrosion performance of hot dip galvanizing coating

In order to analyze the influence of environmental factors on the corrosion resistance of hot-dip galvanized coating, a naturally clean environment and thermal shock treatment were used to simulate the service conditions of products. The surface state and zinc layer thickness of hot-dip galvanized coating under two process conditions were detected. Salt spray corrosion and electrochemical corrosion tests were carried out on hot-dip galvanized coatings. The phase and microstructure of the coating were analyzed by XRD, OM, and SEM. The results show that the hot-dip galvanized coating has a good corrosion protection effect in a naturally clean environment. After thermal shock treatment, cracks in the coating are more likely to occur. With the increase of thermal shock time, the depth of crack on the surface of the coating increases, so the corrosion protection effect of the coating decreases obviously. For the thermal shock treatment of 10-30 days, the coating performance enters the corrosion stability period, and the thickness decreases very little, but when the time exceeds 30 days, the corrosion of the coating accelerates sharply. Electrochemical corrosion shows that the hot-dip galvanized coating has typical coating protection double capacitive reactance curve, and the polar protection effect is good. When the thermal shock treatment time is 30 days, the dense oxide on the coating surface has the best protection effect against corrosion. At this time, the self corrosion current is the smallest and the impedance radius is the largest. When the thermal shock treatment time exceeds 40 days, the cracks on the coating surface will expand to the substrate, and the corrosion protection effect of the coating may fail. So, the corrosion protection effect of hot-dip galvanized coating is limited in the current situation of frequent extreme environments and intensified environmental pollution.

Airwave oscillometry and spirometry in children with asthma or wheeze

Objective Lung function testing is used in diagnosing asthma and assessing asthma control. Spirometry is most commonly used, but younger children can find performing this test challenging. Non-volitional tests such as airwave oscillometry (AOS) may be helpful in that population. We compared the success of spirometry and AOS in assessing bronchodilator responsiveness in children. Methods AOS was conducted alongside routine lung function testing. Resistance at 5 Hz (R5), the difference between the resistance at 5 and 20 Hz (R5-20) and the area under the reactance curve (AX) were assessed. Patients between 5 and 16 years old attending clinic with wheeze or asthma were assessed. Patients performed AOS, followed by spirometry and were then given 400 µg salbutamol; the tests were repeated 15 minutes later. Results Lung function testing was performed in 47 children of whom 46 (98%) and 32 (68%) performed acceptable baseline oscillometry and spirometry, respectively (p < 0.001). Children unable to perform acceptable spirometry were younger (7.35, range: 5.4–10.3 years) than those who could (10.4, range: 5.5–16.9 years), p < 0.001. The baseline z-scores of AOS R5 correlated with FEV1 (r = 0.499, p = 0.004), FEF75 (r = 0.617, p < 0.001), and FEV1/FVC (r = 0.618, p < 0.001). There was a positive bronchodilator response assessed by spirometry (change in FEV1 ≥ 12%) in eight children which corresponded to a change in R5 of 36% (range: 30%–50%) and a change in X5 of 39% (range: 15%–54%). Conclusions Oscillometry is a useful adjunct to spirometry in assessing young asthmatic children’s lung function. The degree of airway obstruction, however, might affect the comparability of the results of the two techniques.

Characterization of chronic lung allograft dysfunction phenotypes using spectral and intrabreath oscillometry.

Background: Chronic lung allograft dysfunction (CLAD) is the major cause of death beyond 2 years after lung transplantation and develops in 50% of all patients by 5 years post-transplant. CLAD is diagnosed on the basis of a sustained drop of 20% for at least 3 months in the forced expiratory volume (FEV1), compared to the best baseline value achieved post-transplant. CLAD presents as two main phenotypes: bronchiolitis obliterans syndrome (BOS) is more common and has better prognosis than restrictive allograft syndrome (RAS). Respiratory oscillometry is a different modality of lung function testing that is highly sensitive to lung mechanics. The current study investigated whether spectral and intrabreath oscillometry can differentiate between CLAD-free, BOS- and RAS-CLAD at CLAD onset, i.e., at the time of the initial 20% drop in the FEV1. Methods: A retrospective, cross-sectional analysis of 263 double lung transplant recipients who underwent paired testing with oscillometry and spirometry at the Toronto General Pulmonary Function Laboratory from 2017 to 2022 was conducted. All pulmonary function testing and CLAD diagnostics were performed following international guidelines. Statistical analysis was conducted using multiple comparisons. Findings: The RAS (n = 6) spectral oscillometry pattern differs from CLAD-free (n = 225) by right-ward shift of reactance curve similar to idiopathic pulmonary fibrosis whereas BOS (n = 32) has a pattern similar to obstructive lung disease. Significant differences were found in most spectral and intrabreath parameters between BOS, RAS, and time-matched CLAD-free patients. Post-hoc analysis revealed these differences were primarily driven by BOS instead of RAS. While no differences were found between CLAD-free and RAS patients with regards to spectral oscillometry, the intrabreath metric of reactance at end-inspiration (XeI) was significantly different (p < 0.05). BOS and RAS were differentiated by spectral oscillometry measure R5, and intrabreath resistance at end expiration, ReE (p < 0.05 for both). Conclusion: Both spectral and intrabreath oscillometry can differentiate BOS-CLAD from CLAD-free states while intrabreath oscillometry, specifically XeI, can uniquely distinguish RAS-CLAD from CLAD-free. Spectral and intrabreath oscillometry offer complementary information regarding lung mechanics in CLAD patients to help distinguish the two phenotypes and could prove useful in prognostication.

Potentiality of impulse oscillometry to evaluate bronchodilator reversibility in untreated adult patients with newly diagnosed asthma.

Identifying positive bronchodilator reversibility (BDR) helps the diagnosis of asthma. However, not all patients can adequately perform the forced expiration during the spirometry test. An alternative test is required. Impulse oscillometry (IOS) is an effort-independent technique that enables the measurement of lung mechanics during quiet tidal breathing. We investigated the potentiality of IOS to evaluate BDR in untreated adult patients with newly diagnosed asthma (UAPNDS). All UAPNDS (aged 20-80 years) who never smoke and underwent IOS and spirometry before and after salbutamol inhalation at their initial visit to the hospital from March 22, 2017, to December 31, 2019, were identified. A total of 323 patients were enrolled. Data from the medical record, including demographic characteristics, laboratory examination, spirometric data, and IOS parameters, were retrospectively reviewed. The associations of parameters with the positive BDR and the performance of parameters in predicting the positive BDR were evaluated by statistical methods. Patients (n = 323) had a median age of 64 years and were mostly female (67.5%). Several variables, including serum total immunoglobulin level, blood eosinophil counts, blood eosinophil percentage (%), and two IOS parameters, were found to be different between the positive (n = 93) and negative BDR (n = 230) groups. Multivariate logistic regression analyses after adjustment by cofactors revealed that the percentage change of the area under the reactance curve between 5 Hz and resonant frequency [ΔAx (%)] after salbutamol inhalation was the only independent factor for the positive BDR. The area under the receiver operating characteristic curve of ΔAx (%) in predicting the positive BDR was 0.614 ( p = 0.0013), and its optimal cutoff value was -53.8% (sensitivity, 39.78% and specificity, 80.43%). In addition to spirometry, ΔAx (%), an IOS parameter, may serve as a novel indicator to evaluate BDR in UAPNDS.

Reference values for respiratory sinusoidal oscillometry in children aged 3 to 17 years.

New oscillometry devices allowing quantification of respiratory function using tidal breathing are commercially available, but reference equations are lacking for the multiethnic Canadian pediatric population. We conducted a prospective cross-sectional study of healthy children carefully selected for absence of asthma, atopy, tobacco smoke, obesity, prematurity, and recent respiratory infection. Triplicate measures were obtained of respiratory system resistance (Rrs) and reactance (Xrs), area under the reactance curve (AX) and resonant frequency (Fres) on four signals, whose testing order was randomized: two signals on the Resmon Pro Full (8 Hz and 5-11-19 Hz) and two signals on the tremoflo C-100 (5-37 Hz and 7-41 Hz). Feasibility was defined as the ability to obtain valid reproducible results. Prediction equations and 95% confidence intervals were derived for whole- and within-breath Rrs and Xrs and for AX and Fres, using linear regression or Generalized Additive Models for Location, Scale and Shape. Of 306 children randomized, valid and reproducible results on ≥1 signal were obtained in 299 (98%) multiethnic (69% Caucasians: 8% Black: 23% Others) children aged 3-17 years, 91-189 cm tall. Standing height was the strongest predictor with no significant effect of sex, age, body mass index or ethnicity. Significant within-patient differences were observed between Resmon Pro and tremoflo C-100 measurements, justifying the derivation of device-specific reference equations. Valid reproducible oscillometry measurements are highly feasible in children aged 3 years and older. Device-specific reference equations, valid for our multiethnic population, are derived.

A positive effect of a short period stay in Alpine environment on lung function in asthmatic children.

Lung function is a central issue in diagnosis and determination of asthma severity and asthma control has been previously reported to improve after a stay in mountain environment for at least 2 weeks. No data are available for shorter periods of stay, in particular for small airways during a stay at altitude. The aim of this study is to focus on changes in respiratory function, regarding both the central airways and the peripheral airways in the first 2 weeks of stay in a mountain environment in asthmatic children. In this study, 66 asthmatic children (age: 14 ± 2.8 years) were evaluated through spirometric and oscillometric tests at the time of arrival at the Istituto Pio XII, Misurina (BL), Italy, 1756 m above sea level (T0), after 24 h (T1), and 168 h (T2) of stay. FEV1%, FEF25%–75%, and FEV1/FVC increased significantly from T0 value both at T1 and T2 (respectively, p = 0.0002, p < 0.0001, p = 0.0002). Oscillometry showed a significant improvement in R5, R20, and R5–20 at both T1 and T2 as compared to T0 (respectively, p = 0.0001, p = 0.0002, and p = 0.049). Reactance at 5 Hz (X5) improved significantly at T2 versus T0, p = 0.0022. The area under reactance curve between Fres and 5 Hz (AX) was significantly reduced (p = 0.0001) both at T1 and T2 as compared to T0. This study shows an improvement in respiratory indices as soon as after 24 h of stay at altitude, persisting in the following week.

Forced Vital Capacity and Low Frequency Reactance Area Measurements Are Associated with Asthma Control and Exacerbations

IntroductionForced vital capacity (FVC) is often preserved in severe asthma unless there is evidence of either airway remodelling or air trapping. Area under the reactance curve (AX) can be used to assess small airways dysfunction related lung stiffness and is related to disease control in severe asthma.MethodsWe explore if there may be a potential synergistic interaction between FVC and AX in terms of impaired asthma control as ACQ and exacerbations requiring oral corticosteroids (OCS). We pragmatically defined < 100% and ≥ 1.0 kPa/L/s as impaired FVC or AX, respectively. ResultsPatients with combined impairment of FVC and AX had significantly worse asthma control as higher ACQ, more severe exacerbations requiring OCS and worse spirometry (FEV1 and FEF25–75) than those with impaired FVC but preserved AX.ConclusionThis in turn supports using both spirometry and oscillometry to characterise airway physiology more comprehensively in patients with more severe asthma.

Reference equations of the impulse oscillatory in healthy Thai adults.

BackgroundThe ethnicity is significantly under-reported and this may limit the applicability of current impulse oscillometry (IOS) equations to heterogeneous patient populations. Establishing predictive equations for the IOS in the Thai adult population is still required. Therefore, this study aimed to establish reference equations for the IOS in the Thai adult population.MethodsThis retrospective cross-sectional study of IOS parameters in healthy adults aged greater than 20 years old with normal spirometry and who had no chronic respiratory diseases. Pre-bronchodilator (BD) IOS was performed in all subjects. Reference equations were calculated separately for men and women using multivariable linear regression analysis.ResultsA total of 127 subjects (87 men and 40 women) with a mean age of 48.7±17.2 (range, 22–92) years were included. The resistance at 5 Hz (R5), resistance at 20 Hz (R20), and area under reactance curve between 5 Hz and resonant frequency (AX) were significantly higher in women compared to men. The reference equations of the IOS parameters were established for men and women. Age, height, and bodyweight were shown to be the influential predictor as they contributed to the most of IOS indices except for the R5–R20 in men equations. Bodyweight was shown to be the influential predictor as it contributed to the most IOS indices except for the X5 in women’s equations.ConclusionsWe provided the reference equations for the IOS indices in Thai adults. IOS indices including R5, R20, and AX were significantly higher in women compared to men.