Preschool impulse oscillometry predicts active asthma and impaired lung function at school age.

BACKGROUND: Asthmatic symptoms often start during early childhood. Impulse oscillometry (IOS) is feasible in preschool children who may be unable to reliably perform spirometry measurements. OBJECTIVE: We sought to evaluate the use of IOS in a multicenter, multiethnic high-risk asthma cohort titled the Vitamin D Antenatal Asthma Reduction Trial. METHODS: The trial recruited pregnant women whose children were followed from birth to age 8 years. Lung function was assessed with IOS at ages 4, 5, and 6 years and spirometry at ages 5, 6, 7, and 8 years. Asthma status, respiratory symptoms, and medication use were assessed with repeated questionnaires from birth to age 8 years. RESULTS: In total, 220 children were included in this secondary analysis. Recent respiratory symptoms and short-acting ß2-agonist use were associated with increased respiratory resistance at 5 Hz at age 4 years (ß = 2.6; 95% CI, 1.0 to 4.4; P = .002 and ß = 3.4; 95% CI, 0.7 to 6.2; P = .015, respectively). Increased respiratory resistance at 5 Hz at age 4 years was also associated with decreased lung function from ages 5 to 8 years (ß = -0.3; 95% CI, -0.5 to -0.1; P < .001 for FEV1 at 8 years) and active asthma at age 8 years (ß = 2.0; 95% CI, 0.2 to 3.8; P = .029). CONCLUSIONS: Increased respiratory resistance in preschool IOS is associated with frequent respiratory symptoms as well as school-age asthma and lung function impairment. Our findings suggest that IOS may serve as a potential objective measure for early identification of children who are at high risk of respiratory morbidity.

Relationships between lung function, allergy, and wheezing in urban children.

BACKGROUND: Allergic sensitization and low lung function in early childhood are risk factors for subsequent wheezing and asthma. However, it is unclear how allergic sensitization affects lung function over time. OBJECTIVE: We sought to test whether allergy influences lung function and whether these factors synergistically increase the risk of continued wheezing in childhood. METHODS: We analyzed longitudinal measurements of lung function (spirometry and impulse oscillometry) and allergic sensitization (aeroallergen skin tests and serum allergen-specific IgE) throughout early childhood in the Urban Environmental and Childhood Asthma study, which included high-risk urban children living in disadvantaged neighborhoods. Intraclass correlation coefficients were calculated to assess lung function stability. Cluster analysis identified low, medium, and high allergy trajectories, which were compared with lung function and wheezing episodes in linear regression models. A variable selection model assessed predictors at age 5 years for continued wheezing through age 12 years. RESULTS: Lung function adjusted for growth was stable (intraclass correlation coefficient, 0.5-0.7) from age 5 to 12 years and unrelated to allergy trajectory. Lung function and allergic sensitization were associated with wheezing episodes in an additive fashion. In children with asthma, measuring lung function at age 5 years added little to the medical history for predicting future wheezing episodes through age 12 years. CONCLUSIONS: In high-risk urban children, age-related trajectories of allergic sensitization were not associated with lung function development; however, both indicators were related to continued wheezing. These results underscore the importance of understanding early-life factors that negatively affect lung development and suggest that treating allergic sensitization may not alter lung function development in early to mid-childhood.

Clinical characterization and outcomes of impulse oscillometry-defined bronchodilator response: an ECOPD cohort-based study.

BACKGROUND: The clinical significance of the impulse oscillometry-defined small airway bronchodilator response (IOS-BDR) is not well-known. Accordingly, this study investigated the clinical characteristics of IOS-BDR and explored the association between lung function decline, acute respiratory exacerbations, and IOS-BDR. METHODS: Participants were recruited from an Early Chronic Obstructive Pulmonary Disease (ECOPD) cohort subset and were followed up for two years with visits at baseline, 12 months, and 24 months. Chronic obstructive pulmonary disease (COPD) was defined as a post-bronchodilator forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) ratio < 0.70. IOS-BDR was defined as meeting any one of the following criteria: an absolute change in respiratory system resistance at 5 Hz ≤ - 0.137 kPa/L/s, an absolute change in respiratory system reactance at 5 Hz ≥ 0.055 kPa/L/s, or an absolute change in reactance area ≤ - 0.390 kPa/L. The association between IOS-BDR and a decline in lung function was explored with linear mixed-effects model. The association between IOS-BDR and the risk of acute respiratory exacerbations at the two-year follow-up was analyzed with the logistic regression model. RESULTS: This study involved 466 participants (92 participants with IOS-BDR and 374 participants without IOS-BDR). Participants with IOS-BDR had higher COPD assessment test and modified Medical Research Council dyspnea scale scores, more severe emphysema, air trapping, and rapid decline in FVC than those without IOS-BDR over 2-year follow-up. IOS-BDR was not associated with the risk of acute respiratory exacerbations at the 2-year follow-up. CONCLUSIONS: The participants with IOS-BDR had more respiratory symptoms, radiographic structural changes, and had an increase in decline in lung function than those without IOS-BDR. TRIAL REGISTRATION: Chinese Clinical Trial Registry, ChiCTR1900024643. Registered on 19 July, 2019.

Machine learning for accurate detection of small airway dysfunction-related respiratory changes: an observational study.

BACKGROUND: The use of machine learning(ML) methods would improve the diagnosis of small airway dysfunction(SAD) in subjects with chronic respiratory symptoms and preserved pulmonary function(PPF). This paper evaluated the performance of several ML algorithms associated with the impulse oscillometry(IOS) analysis to aid in the diagnostic of respiratory changes in SAD. We also find out the best configuration for this task. METHODS: IOS and spirometry were measured in 280 subjects, including a healthy control group (n = 78), a group with normal spirometry (n = 158) and a group with abnormal spirometry (n = 44). Various supervised machine learning (ML) algorithms and feature selection strategies were examined, such as Support Vector Machines (SVM), Random Forests (RF), Adaptive Boosting (ADABOOST), Navie Bayesian (BAYES), and K-Nearest Neighbors (KNN). RESULTS: The first experiment of this study demonstrated that the best oscillometric parameter (BOP) was R5, with an AUC value of 0.642, when comparing a healthy control group(CG) with patients in the group without lung volume-defined SAD(PPFN). The AUC value of BOP in the control group was 0.769 compared with patients with spirometry defined SAD(PPFA) in the PPF population. In the second experiment, the ML technique was used. In CGvsPPFN, RF and ADABOOST had the best diagnostic results (AUC = 0.914, 0.915), with significantly higher accuracy compared to BOP (p < 0.01). In CGvsPPFA, RF and ADABOOST had the best diagnostic results (AUC = 0.951, 0.971) and significantly higher diagnostic accuracy (p < 0.01). In the third, fourth and fifth experiments, different feature selection techniques allowed us to find the best IOS parameters (R5, (R5-R20)/R5 and Fres). The results demonstrate that the performance of ADABOOST remained essentially unaltered following the application of the feature selector, whereas the diagnostic accuracy of the remaining four classifiers (RF, SVM, BAYES, and KNN) is marginally enhanced. CONCLUSIONS: IOS combined with ML algorithms provide a new method for diagnosing SAD in subjects with chronic respiratory symptoms and PPF. The present study's findings provide evidence that this combination may help in the early diagnosis of respiratory changes in these patients.

Therapeutic effect of long-acting muscarinic antagonist for treating uncontrolled asthma assessed using impulse oscillometry.

BACKGROUND: In recent years, the incorporation of LAMAs into asthma therapy has been expected to enhance symptom control. However, a significant number of patients with asthma continue to experience poorly managed symptoms. There have been limited investigations on LAMA-induced airway alterations in asthma treatment employing IOS. In this study, we administered a LAMA to patients with poorly controlled asthma, evaluated clinical responses and respiratory function, and investigated airway changes facilitated by LAMA treatments using the IOS. METHODS: Of a total of 1282 consecutive patients with asthma, 118 exhibited uncontrolled symptoms. Among them, 42 switched their treatment to high-dose fluticasone furoate/umeclidinium/vilanterol (FF/UMEC/VI) (ICS/LABA/LAMA). The patients were then assessed using AHQ-33 or LCQ and ACT. Spirometry parameters (such as FEV1 or MMEF) and IOS parameters (such as R20 or AX) were measured and compared before and after exacerbations and the addition of LAMA. RESULTS: Of the 42 patients, 17 who switched to FF/UMEC/VI caused by dyspnea exhibited decreased pulmonary function between period 1 and baseline, followed by an increase in pulmonary function between baseline and period 2. Significant differences were observed in IOS parameters such as R20, R5-R20, Fres, or AX between period 1 and baseline as well as between baseline and period 2. Among the patients who switched to inhaler due to cough, 25 were classified as responders (n = 17) and nonresponders (n = 8) based on treatment outcomes. Among nonresponders, there were no significant differences in spirometry parameters such as FEV1 or PEF and IOS parameters such as R20 or AX between period 1 and baseline. However, among responders, significant differences were observed in all IOS parameters, though not in most spirometry parameters, between period 1 and baseline. Furthermore, significant differences were noted between baseline and period 2 in terms of FEV1, %MMEF, %PEF, and all IOS parameters. CONCLUSION: ICS/LABA/LAMA demonstrates superiority over ICS/LABA in improving symptoms and lung function, which is primarily attributed to the addition of LAMA. Additionally, IOS revealed the effectiveness of LAMA across all airway segments, particularly in the periphery. Hence, LAMA can be effective against various asthma phenotypes characterized by airway inflammation, even in real-world cases.

Airway Reactance Predicts Static Lung Hyperinflation in Severe Asthma.

BACKGROUND AND OBJECTIVES: Background: Static lung hyperinflation (SLH) measured using body plethysmography in patients with asthma is associated with poor outcomes. The severity of SLH may be associated with small airway dysfunction (SAD), which can be measured using impulse oscillometry (IOS). Objective: This study aims to determine the correlation between SLH and SAD in patients with severe asthma and assess the improvement in SLH and SAD with treatment. METHODS: We analyzed data from patients who were enrolled in the Taiwan Severe Asthma Registry, which comprises a prospective observational cohort. Plethysmography and IOS were performed regularly. The relationship between spirometry and IOS parameters was determined. Changes in the clinical outcomes in response to treatment were analyzed. RESULTS: Of 107 patients with severe asthma, 83 (77.6%) had SLH based on an increased residual volume to total lung capacity ratio (RV/ TLC). Most patients were older women with worse pulmonary function and SAD than those without SLH. SAD, defined as increased airway resistance/reactance, was significantly correlated with SLH. Airway reactance at 5 Hz (X5) ≤-0.21 kPa/(L/s) detected SLH with an area under the receiver operating characteristic curve of 0.84 (P<.0001; sensitivity, 85.2%; and specificity, 83.3%). After 12 months, patients who received add-on biologics (vs those who did not) had significantly reduced exacerbations, fractional exhaled nitric oxide level, and blood eosinophil counts, as well as improved forced expiratory volume in the first second, X5, and a trend toward reduced RV/TLC ratio. CONCLUSIONS: In severe asthma, airway reactance (X5) could be a novel parameter for assessing SLH.

Impulse oscillometry in the diagnosis of cough variant asthma in children.

BACKGROUND: Cough variant asthma (CVA) is one of the most common causes of chronic cough in children worldwide. The diagnosis of CVA in children remains challenging. This study aimed to assess the diagnostic utility of impulse oscillometry (IOS) pulmonary function in children with CVA. METHODS: This study included children aged 4 to 12 years diagnosed with CVA who underwent IOS pulmonary function and bronchodilation (BD) tests. A control group of healthy children was matched. Pre- and post-BD IOS parameters were recorded and presented as mean ± standard deviation or median. Receiver operating characteristic (ROC) curves were plotted, and the area under the curve (AUC) was calculated to evaluate the discriminatory potential of the IOS parameters for diagnosing CVA. RESULTS: A total of 180 patients with CVA and 65 control subjects were included. The baseline IOS parameters in the CVA group, except X5%pred, were significantly greater compared to the control group. After inhalation of salbutamol sulfate, all IOS parameters improved significantly in the CVA group. However, Z5%pred, R5%pred, and R20%pred remained greater in the CVA group compared to the control group. The improvement rates of IOS parameters in the CVA group significantly surpassed those in the control group. The ROC curve results for pre-BD IOS parameters and the improvement rate during the BD test showed that the combinations of pre-Z5%pred+△Z5% and pre-R5%pred+△R5% achieved the highest AUC value of 0.920 and 0.898, respectively. The AUC values of these combined parameters surpassed those of individual ones. CONCLUSIONS: This study highlights that children with CVA exhibit greater IOS parameters compared to healthy children. The changes in IOS parameters during the BD test provided valuable diagnostic information for CVA, and the combination of various parameters can help pediatricians accurately identify CVA in children.

Correlation between impulse oscillometry parameters and test for respiratory and asthma control in kids (TRACK) in asthma control of preschoolers with asthma.

BACKGROUND: Little research has been conducted to evaluate the correlation between impulse oscillometry (IOS), Childhood Asthma Control Test (C-ACT), and Test for Respiratory and Asthma Control in Kids (TRACK). METHODS: This study was conducted at China Medical University Hospital between September 1, 2019, and March 31, 2021. Children aged 2-6 years who had been diagnosed with asthma with acute exacerbation were enrolled and followed-up until the end of the study. Correlations between the parameters of IOS, C-ACT and TRACK were assessed. The validity and reliability of TRACK were verified. RESULTS: A total of 114 children with asthma and acute exacerbations were recruited. Their mean age was 4.1 ± 1.1 years, and 60.5% were males. After a year of treatment, the change of R5-R20 from baseline 0.64 ± 0.38 kPa/L/s to 12th month 0.48 ± 0.2 kPa/L/s (p = 0.022). TRACK and C-ACT scores were significantly correlated during the observation period. R5-R20 in IOS at baseline and at the 12th month of follow-up as well as the change in IOS parameters were significantly associated with C-ACT (p = 0.003, 0.015, and 0.001, respectively). R5% and R5-R20 changes in IOS were associated with TRACK (p = 0.04 and 0.025, respectively). Sensitivity and specificity of TRACK were 80.8% (67.5-90.4) and 100% (94.1-100), respectively, with cut-off points >95 and AUC 93.8%. CONCLUSION: TRACK score appears to have a stronger association with the IOS parameter than C-ACT score. Our findings indicate that TRACK is a valid tool for assessing asthma control in preschool children.

Maternal vitamin D status modifies the effects of early life tobacco exposure on child lung function.

BACKGROUND: Prior studies suggest that vitamin D may modify the effects of environmental exposures; however, none have investigated gestational vitamin D and cumulative tobacco smoke exposure (TSE) throughout pregnancy and early life. OBJECTIVES: This study investigated the effects of early life TSE on child lung function and the modulatory effects of gestational vitamin D on this association. METHODS: The VDAART (Vitamin D Antenatal Asthma Reduction Trial) recruited nonsmoking pregnant women and followed the mother-child pairs to age 6 years. TSE was assessed with questionnaires and plasma cotinine measurements in the mothers (10-18 and 32-38 gestational weeks) and children (1, 3, and 6 years). Cumulative TSE was calculated from the repeated cotinine measurements. 25-hydroxyvitamin D (25[OH]D) levels were measured at 10-18 and 32-38 gestational weeks. Lung function was assessed at 6 years with spirometry and impulse oscillometry. RESULTS: Of the 476 mother-child pairs, 205 (43%) had increased cotinine levels at ≥1 time point. Cumulative TSE was associated with decreased FEV1 (ß = -0.043 L, P = .018) and increased respiratory resistance at 5 Hz (R5; ß = 0.060 kPa/L/s, P = .002). This association persisted in subjects with insufficient (<30 ng/mL) 25(OH)D levels throughout pregnancy (ß = 0.077 kPa/L/s, P = .016 for R5) but not among those with sufficient levels throughout pregnancy. CONCLUSIONS: Cumulative TSE from pregnancy to childhood is associated with dose- and duration-dependent decreases in child lung function at 6 years even in the absence of reported maternal smoking. Gestational vitamin D may modulate this effect and have therapeutic potential for minimizing the adverse effect of TSE on lung throughout early life. RANDOMIZED TRIAL: Maternal Vitamin D Supplementation to Prevent Childhood Asthma (VDAART); clinicaltrials.gov identifier: NCT00920621.

Lower Arginine Bioavailability, Increased FeNO Levels, and Airway Resistance on Impulse Oscillometry Are Characteristics of Asthma in Children and Young Adults with Sickle Cell Disease.

Background and Objectives: Data on characteristics of asthma in children with sickle cell disease (SCD) is conflicting. Recently, the L-arginine pathway has gained attention in the pathogenesis of asthma and SCD. This study aimed to determine the distinctive clinical and laboratory features and the role of arginine metabolism in asthmatic children with SCD. Materials and Methods: A total of 52 children and adolescents with SCD, including 24 with asthma (SCD-A) and 28 without asthma (SCD-NA), and 40 healthy controls were included. A questionnaire, atopy tests, fractional exhaled nitric oxide (FeNO), and lung function tests were employed. Serum metabolites of the arginine pathway were measured. The results of the three groups were compared. Results: The demographic characteristics and atopy markers of the three groups were similar. FEV1%, FEV1/FVC, MMEF%, and total lung capacity (TLC%) values of SCD-A patients were not significantly different from the SCD-NA group, but they were significantly lower than the values measured in the controls. FeNO values greater than 35 ppb were present only in the SCD-A group. In impulse oscillometry, median resistance values at 5 Hz (R5)% were higher in both SCD subgroups than in healthy controls (p = 0.001). The (R5-20/R5)% values were higher in the SCD-A group (p = 0.028). Serum arginine levels and arginine bioavailability indices were significantly lower in the SCD-A group than in the SCD-NA group and healthy controls (p = 0.003 and p < 0.001). Conclusions: Asthma in children with SCD was not associated with atopy or low FEV1/FVC levels. However, lower arginine bioavailability and higher FeNO levels differentiated asthma in patients with SCD. High R5% and (R5-20/R5)% values indicated increased airway resistance in SCD, with a predominance of small airway disease in asthmatics.

Small airway resistance in obese and nonobese patients with obstructive sleep apnea syndrome using impulse oscillometry.

Background/aim: There is limited information on the pathologic changes in the small airways among obese and nonobese patients with obstructive sleep apnea syndrome (OSAS). Impulse oscillometry (IOS) measures airway resistance and reactance independently of patient effort. This study aimed to compare airway resistance in small airways using IOS between obese and nonobese patients with OSAS. Materials and methods: In this real-life cross-sectional study, demographic information was collected from obese and nonobese subjects diagnosed with moderate and severe OSAS without any other underlying diseases. Spirometry and IOS measurements were conducted, and the values of both groups were statistically analyzed. Results: The nonobese group had a mean age of 45.6 ± 11.7 years (median 45), while the obese group had a mean age of 48.4 ± 9.5 years (median 47.5). The mean body mass index (BMI) for the nonobese group was 26.2 ± 2.1 kg/m2 (median 27 kg/m2), and for the obese group, it was 35.6 ± 6.4 kg/m2 (median 33 kg/m2). Statistically significant differences were observed between the two groups in R5 - R20 percentage, reactance area (AX), and resonant frequency (Fres) values (p < 0.05). Conclusion: Among obese OSAS patients, there is an increase in resistance in small airways as indicated by IOS values. IOS shows promise as a potential screening tool for diagnosing OSAS.

Use of impulse oscillometry to assess lung function in prematurely born children and young people: Comparisons with spirometry.

Premature birth is a risk factor for bronchopulmonary dysplasia (BPD); both of which are associated with obstructive airway disease throughout childhood. Impulse oscillometry (IOS) is an effort-independent, passive measure of tidal breathing, which could have benefits in assessing lung function amongst younger patients unable to perform valid spirometry. A literature search was conducted to investigate the use of IOS in prematurely born children and young people. IOS results correlate with those of spirometry. Reversibility of airway obstruction in children with BPD is variable. IOS could have benefits in assessing individual patient response and suitability for bronchodilator therapy. More work, however, is required to establish multi-ethnic reference ranges and standardise commercially available devices prior to its routine incorporation into clinical practice.

Usefulness of simultaneous impulse oscillometry and spirometry with airway response to bronchodilator in the diagnosis of asthmatic cough.

Objective: Some of the most common causes of chronic cough include cough variant asthma (CVA), bronchial asthma (BA), and asthma-COPD overlap (ACO). Although there is some overlap in the etiology of these diseases, it is clinically important to attempt an early differential diagnosis due to treatment strategies and prognoses.Methods: Spirometry and impulse oscillometry (IOS) before and after bronchodilator inhalation were analyzed for clinically diagnosed CVA (cCVA, n = 203), BA (cBA, n = 222), and ACO (cACO, n = 61).Results: A significant difference in ΔFEV1 was observed between cBA and cCVA (ΔFEV1 improvement of 122.5 mL/5.4% and 65.7 mL/2.2%, respectively), but no difference was observed in ΔPEF, ΔV50, or ΔV25. Except for R20 (resistance at 20 Hz), significant differences between the three groups were observed in IOS. In IOS, cCVA and cBA showed comparable peripheral airway response to bronchodilator which was thought to be commensurate with changes in V50 and V25. cACO improved ΔFEV1 improvement of 81.0 mL/6.2% and was distinguished by a downward respiratory system reactance (Xrs) waveform with a limited bronchodilator response. FEV1/FVC, %FEV1, and %V25 had relatively strong correlations with the three IOS parameters, X5 (reactance at 5 Hz), resonant frequency (Fres), and low-frequency reactance area (ALX), in the correlation between IOS and spirometers.Conclusion: Changes in IOS parameters were more sensitive in this study than changes in FEV1 or the flow-volume curve. Considering the benefits and relevance of the two different tests, simultaneous IOS and spirometry testing were useful in the diagnosis of asthmatic cough.

Short-term effect of particulate matter on lung function and impulse oscillometry system (IOS) parameters of chronic obstructive pulmonary disease (COPD) in Beijing, China.

OBJECTIVE: This study aimed to evaluate the associations between particulate matter (PM), lung function and Impulse Oscillometry System (IOS) parameters in chronic obstructive pulmonary disease (COPD) patients and identity effects between different regions in Beijing, China. METHODS: In this retrospective study, we recruited 1348 outpatients who visited hospitals between January 2016 and December 2019. Ambient air pollutant data were obtained from the central monitoring stations nearest the participants' residential addresses. We analyzed the effect of particulate matter with aerodynamic diameter ≤ 2.5 µm (PM2.5) exposure on lung function and IOS parameters using a multiple linear regression model, adjusting for sex, smoking history, education level, age, body mass index (BMI), mean temperature, and relative humidity . RESULTS: The results showed a relationship between PM2.5, lung function and IOS parameters. An increase of 10 µg/m3 in PM2.5 was associated with a decline of 2.083% (95% CI: -3.047 to - 1.103) in forced expiratory volume in one second /predict (FEV1%pred), a decline of 193 ml/s (95% CI: -258 to - 43) in peak expiratory flow (PEF), a decline of 0.932% (95% CI: -1.518 to - 0.342) in maximal mid-expiratory flow (MMEF); an increase of 0.732 Hz (95% CI: 0.313 to 1.148) in resonant frequency (Fres), an increase of 36 kpa/(ml/s) (95% CI: 14 to 57) in impedance at 5 Hz (Z5) and an increase of 31 kpa/(ml/s) (95% CI: 2 to 54) in respiratory impedance at 5 Hz (R5). Compared to patients in the central district, those in the southern district had lower FEV1/FVC, FEV1%pred, PEF, FEF75%, MMEF, X5, and higher Fres, Z5 and R5 (p < 0.05). CONCLUSION: Short-term exposure to PM2.5 was associated with reductions in lung function indices and an increase in IOS results in patients with COPD. The heavier the PM2.5, the more severe of COPD.

Application of impulse oscillometry to detect interstitial lung disease and airway disease in adults with rheumatoid arthritis.

BACKGROUND: We conducted a retrospective observational study to explore the potential application of impulse oscillometry (IOS) as an alternative to high-resolution computed tomography (HRCT) for detecting pulmonary involvement in patients with rheumatoid arthritis (RA) because clinically evident interstitial lung disease (ILD) and airway involvement are common in this population. METHODS: We enrolled 72 patients with RA who underwent pulmonary function tests (PFTs) and IOS between September 2021 and September 2022. We aimed to identify the PFT and IOS variables associated with lung diseases shown on HRCT images. RESULTS: In our cohort of 72 patients, 48 underwent HRCT; of these, 35 had airway disease or ILD and 13 showed no obvious abnormalities on HRCT. Abnormal IOS and PFT parameters were observed in 34 and 23 patients, respectively, with abnormal HRCT images. The predicted percentages for forced vital capacity, the ratio of forced expiratory volume in the first one second to forced vital capacity, and forced mid-expiratory flow value were significantly lower in patients with abnormal HRCT. Lung resistance at 5 Hz, difference in resistance between 5 and 20 Hz, resonant frequency (Fres), and reactance area were higher in these patients and reactance at 5 Hz was lower. Compared to other parameters, Fres > 14.14 was significantly associated with alterations in HRCT and may be used as an indicator for monitoring disease. CONCLUSION: Fres > 14.14 is significantly associated with lung involvement in RA patients. Performance of spirometry with IOS is more beneficial than spirometry alone for evaluating lung involvement in RA patients.

Clinical characteristics of airway impairment assessed by impulse oscillometry in patients with chronic obstructive pulmonary disease: findings from the ECOPD study in China.

BACKGROUND: The role of airway impairment assessed by impulse oscillometry (IOS) in patients with chronic obstructive pulmonary disease (COPD) remains unclear. Therefore, this study aimed to analyze the proportion and clinical characteristics of airway impairment assessed by IOS across COPD severities, and explore whether airway impairment is a subtype of COPD. METHODS: This study was based on cross-sectional data from the ECOPD cohort in Guangdong, China. Subjects were consecutively recruited from July 2019 to August 2021. They filled out questionnaires and underwent lung function tests, IOS and computed tomography (CT). COPD was defined as post-bronchodilator forced expiratory volume in one second/forced vital capacity < lower limit of normal (LLN). Meanwhile, airway impairment was defined as IOS parameters > upper limit of normal or < LLN. On the one hand, Poisson regression was employed to analyze the associations between acute exacerbations of COPD (AECOPD) in the previous year and airway impairment. On the other hand, logistic regression was used to assess differences in CT imaging between patients with IOS parameters' abnormalities and patients with normal IOS parameters. RESULTS: 768 COPD subjects were finally enrolled in the study. The proportion of airway impairment assessed by R5, R20, R5-R20, X5, AX, and Fres was 59.8%, 29.7%, 62.5%, 52.9%, 60.9% and 67.3%, respectively. Airway impairment assessed by IOS parameters (R5, R5-R20, X5, AX, and Fres) in patients with COPD was present across all severities of COPD, particularly in GOLD 3-4 patients. Compared with patients with normal IOS parameters, patients with IOS parameters' abnormalities had more respiratory symptoms, more severe airway obstruction and imaging structural abnormalities. Patients with IOS parameters' abnormalities assessed by R5 [risk ratio (RR): 1.58, 95% confidential interval (CI): 1.13-2.19, P = 0.007], R5-R20 [RR: 1.73, 95%CI: 1.22-2.45, P = 0.002], X5 [RR: 2.11, 95%CI: 1.51-2.95, P < 0.001], AX [RR: 2.20, 95%CI: 1.53-3.16, P < 0.001], and Fres [RR: 2.13, 95%CI: 1.44-3.15, P < 0.001] had a higher risk of AECOPD in the previous year than patients with normal IOS parameters. CONCLUSIONS: Airway impairment assessed by IOS may be a subtype of COPD. Future studies are warranted to identify the underlying mechanisms and longitudinal progression of airway impairment.

The impact of adenoid hypertrophy on pulmonary functions measured using impulse oscillometry in preschool-age children.

PURPOSE: To assess pulmonary impedance [resistance (zR5, zR20, R5-20, Fres, and AX) and reactance (zX5 and zX20)] using impulse oscillometry (IOS) in children with adenoid hypertrophy (AH) and its association with the degree of AH, and to evaluate subsequent changes in pulmonary function 3 months after adenoidectomy. METHODS: This prospective cross-sectional study was conducted with 170 preschool-age children [110 with AH and 60 sex- and age-matched healthy controls (HCs)]. Pulmonary function was analyzed using IOS at baseline (1st visit) in all participants and 3 months after adenoidectomy (2nd visit) in patients who underwent the operation. RESULTS: The IOS parameters of zR5, zR20, R5-20, Fres, and AX were higher, but zX20 was lower, in children with AH compared to the HCs (p < 0.05 for all). The parameters of zR5, Fres, and AX were higher in children with grade IV AH than in those with grade I (p < 0.001). zR5, zR20, R5-20, Fres, and AX decreased, but zX20 increased, after adenoidectomy (2nd visit) compared to baseline (1st visit) (p < 0.05). Post-adenoidectomy (2nd visit) zR5, AX, Fres values were higher in children with AH compared to baseline values in the HCs (1st visit) (p < 0.05). The area under the ROC curve (AUC) value for estimating adenoidectomy was 0.741 for zX20 (CI 0.648-0.834, p < 0.001) with a cut-off value of  ≤ -3.21, sensitivity of 68.8%, and specificity of 70%. CONCLUSION: This study shows that IOS is a useful method for demonstrating subclinical bronchial obstruction in preschool-age children with AH with greater pulmonary impedance (resistance and reactance). Pulmonary impedance decreased 3 months after adenoidectomy, but remained higher than in the HCs. The IOS parameter of X20 may be predictive of adenoidectomy. This study evaluated the pulmonary functions of children with adenoid hypertrophy (AH) using impulse oscillometry (IOS) and the association with the scale of AH. Pulmonary functions were analyzed using IOS. The main IOS parameters include resistances (zR5 and zR20), reactance (zX5 and zX20), R5-20 (resistance at 5 Hz minus resistance at 20 Hz), resonant frequency (Fres), and AX. Fres is the point at which reactance is zero and is measured in Hz (1/s). The Reactance Area (AX - "Goldman Triangle") represents the integrated low-frequency respiratory reactance magnitude between 5 Hz and Fres. Faster frequencies of R (~ 20 Hz) reflect larger airways, regarded as resistance around the central airways. Lower frequencies of R (~ 5 Hz) providing information around the entire (small and large) airways. Peripheral (small) airway resistance is defined by R5-20. IOS parameters of zR5, zX20, Fres, and AX differed among AH grades I-IV and compared to the HCs (p < 0.001 for all).

Evaluation of a Respiration Rate Sensor for Recording Tidal Volume in Calves under Field Conditions.

In the assessment of pulmonary function in health and disease, both respiration rate (RR) and tidal volume (Vt) are fundamental parameters of spontaneous breathing. The aim of this study was to evaluate whether an RR sensor, which was previously developed for cattle, is suitable for additional measurements of Vt in calves. This new method would offer the opportunity to measure Vt continuously in freely moving animals. To measure Vt noninvasively, the application of a Lilly-type pneumotachograph implanted in the impulse oscillometry system (IOS) was used as the gold standard method. For this purpose, we applied both measuring devices in different orders successively, for 2 days on 10 healthy calves. However, the Vt equivalent (RR sensor) could not be converted into a true volume in mL or L. For a reliable recording of the Vt equivalent, a technical revision of the RR sensor excluding artifacts is required. In conclusion, converting the pressure signal of the RR sensor into a flow equivalent, and subsequently into a volume equivalent, by a comprehensive analysis, provides the basis for further improvement of the measuring system.

[The possibilities of impulse oscillometry in the diagnosis of the lung function disorders after COVID-19].

BACKGROUND: Impulse oscillometry (IOS) is an effort independent method of studying lung mechanics. AIM: To study the diagnostic significance of IOS in assessing lung mechanics after COVID-19. MATERIALS AND METHODS: Spirometry, body plethysmography, diffusion test (DLco), IOS parameters were analyzed in 315 patients (the median age 48 years), the median period from the beginning of COVID-19 to the study was 50 days. Statistical analysis included descriptive statistics, correlation analysis and one-dimensional logistic regression analysis with an assessment of odds ratios. RESULTS: In general group, spirometry and body plethysmography parameters were in normal values, while DLCO was reduced in 61% of patients. Parameters of IOS were analyzed in the general group and between the groups, depending on the value of DLco and total lung capacity (TLC): normal or reduced. In general group, reactance area (AX), hererogeneity of resistance Rrs5-Rrs20, resistance at 5 Hz (Rrs5), reactance at 5 Hz (ΔXrs5) were increased in 29.8%, 17.8%, 6%, 4.8% of patients, respectively, and were statistically significantly higher in the group with reduced TLC, whereas in the group with reduced DLco AX, Rrs5-Rrs20 were statistically significantly higher. Logistic regression analysis showed that patients with Rrs5-Rrs20>0.07 kPa×sec/l or AX>0.32 kPa/l had a 1.99-fold and 2.24-fold increased risk for decrease DLco, respectively, while the risk of decrease in TLC was 2.25-fold (p=0.012) and 3.16-fold (p<0.001) higher, respectively. CONCLUSION: IOS allow to detect both dysfunction of small airways (if AX or Rrs5-Rrs20 are increased) and the risk of restrictive pattern and lung diffusion impairment after COVID-19.

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.