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Background: Within-breath analysis of oscillometry parameters is a growing research area since it increases sensitivity and specificity to respiratory pathologies and conditions. However, reference equations for these parameters in White adults are lacking and devices using multiple sinusoids or pseudorandom forcing stimuli have been underrepresented in previous studies deriving reference equations. The current study aimed to establish reference ranges for oscillometry parameters, including also the within-breath ones in White adults using multi-sinusoidal oscillations. Methods: White adults with normal spirometry, BMI ≤30 kg/m2, without a smoking history, respiratory symptoms, pulmonary or cardiac disease, neurological or neuromuscular disorders, and respiratory tract infections in the previous 4 weeks were eligible for the study. Study subjects underwent oscillometry (multifrequency waveform at 5–11–19 Hz, Resmon PRO FULL, RESTECH Srl, Italy) in 5 centers in Europe and the USA according to international standards. The within-breath and total resistance (R) and reactance (X), the resonance frequency, the area under the X curve, the frequency dependence of R (R5–19), and within-breath changes of X (ΔX) were submitted to lambda-mu-sigma models for deriving reference equations. For each output parameter, an AIC-based stepwise input variable selection procedure was applied. Results: A total of 144 subjects (age 20.8–86.3 years; height 146–193 cm; BMI 17.42–29.98 kg/m2; 56% females) were included. We derived reference equations for 29 oscillatory parameters. Predicted values for inspiratory and expiratory parameters were similar, while differences were observed for their limits of normality. Conclusions: We derived reference equations with narrow confidence intervals for within-breath and whole-breath oscillatory parameters for White adults. [ABSTRACT FROM AUTHOR]

This study investigated the relationship between three respiratory support approaches on lung volume recruitment during the first 2 h of postnatal life in preterm lambs. We estimated changes in lung aeration, measuring respiratory resistance and reactance by oscillometry at 5 Hz. We also measured intratracheal pressure in subsets of lambs. The first main finding is that sustained inflation (SI) applied noninvasively (Mask SI; n = 7) or invasively [endotracheal tube (ETT) SI; n = 6] led to similar rapid lung volume recruitment (∼6 min). In contrast, Mask continuous positive airway pressure (CPAP) without SI (n = 6) resuscitation took longer (∼30–45 min) to reach similar lung volume recruitment. The second main finding is that, in the first 15 min of postnatal life, the Mask CPAP without SI group closed their larynx during custom ventilator-driven expiration, leading to intratracheal positive end-expiratory pressure of ∼17 cmH2O (instead of 8 cmH2O provided by the ventilator). In contrast, the Mask SI group used the larynx to limit inspiratory pressure to ∼26 cmH2O (instead of 30 cmH2O provided by the ventilator). These different responses affected tidal volume, being larger in the Mask CPAP without SI group [8.4 mL/kg; 6.7–9.3 interquartile range (IQR)] compared to the Mask SI (5.0 mL/kg; 4.4–5.2 IQR) and ETT SI groups (3.3 mL/kg; 2.6–3.7 IQR). Distinct physiological responses suggest that spontaneous respiratory activity of the larynx of preterm lambs at birth can uncouple pressure applied by the ventilator to that applied to the lung, leading to unpredictable lung pressure and tidal volume delivery independently from the ventilator settings. NEW & NOTEWORTHY: We compared invasive and noninvasive resuscitation on lambs at birth, including or not sustained inflation (SI). Lung volume recruitment was faster in those receiving SI. During noninvasive resuscitation, larynx modulation reduced tracheal pressure from that applied to the mask in lambs receiving SI, while it led to increased auto-positive end-expiratory pressure and very large tidal volumes in lambs not receiving SI. Our results highlight the need for individualizing pressures and monitoring tidal volumes during resuscitation at birth. [ABSTRACT FROM AUTHOR]

Developing countries face a huge challenge in managing obstructive lung disorders due to frequency, severity, management, and economic impact. Spirometry has been the popular choice to assess the severity and reversibility of airflow obstruction, but the success of evaluation depends on the practitioner’s skills and the patient’s cooperation. Impulse oscillometry (IOS), a variant of forced oscillation technique is preferred over spirometry since it can be performed without forced respiratory maneuvers. The objective of this review is to evaluate IOS techniques and weigh its benefits against spirometry. Publications from international electronic databases such as PubMed, Scopus, and Web of Science were searched using relevant keywords for 5 years (2018–2023). A total of 416 articles were filtered, and of these, 70 were selected which specifically discussed the principles, procedures, parameters, and interpretations of spirometry and oscillometry. From the full-text articles included, we have reflected on the history, defined, explained, compared, and contrasted spirometry and oscillometry methods to establish the versatility of oscillometry technique to identify small airway functions and its application in special clinical conditions. This review presents an easily comprehensible synthesis of oscillometry and spirometry bringing out the principles, advantages, and limitations that are suitable for a larger spectrum of healthcare and research community.

The fact that some SARS-CoV-2 pneumonia patients benefit from changing body position, and some from continuous positive airways pressure (CPAP), indicates the functional character of hypoxia. We hypothesize that such effects could be explained by the closure of small airways. To prove the hypothesis, we evaluated the patency of small airways in 30 oxygen-dependent, spontaneously breathing patients with SARS-CoV-2 pneumonia during their hospital stay using the FOT method and then compared the results with data obtained three months later. During the acute period, total resistance (R5) and peripheral resistance (R5-20) rose above the upper limit of normal (ULN) in 28% and 50% of all patients, respectively. Reactance indices X5, AX and Fres exceeded ULN in 55%, 68% and 66% of cases. Significant correlations were observed between PaO2/FiO2, the time spent in the hospital and R5, X5, AX and Fres. After 3 months, 18 patients were re-examined. During the hospital stay, 11 of them had risen above the upper limit of normal (ULN), for both resistance (R5-20) and reactance (X5, AX) values. Three months later, ULN for R5-20 was exceeded in only four individuals, but ULN for X5 and AX was exceeded in five individuals. Lung function examination revealed a combined restrictive/obstructive ventilatory failure and reduced CO transfer factor. We interpret these changes as lung tissue remodeling due to the process of fibrosis. We conclude that during acute period of SARS-CoV-2 pneumonia, dilated pulmonary blood vessels and parenchymal oedema induce functional closure of small airways, which in turn induce atelectasis with pulmonary right-to-left shunting, followed by the resulting hypoxemia. [ABSTRACT FROM AUTHOR]

Elayne Moura Teixeira,1 Caroline Oliveira Ribeiro,1 Agnaldo José Lopes,2,3 Pedro Lopes de Melo1,4 1Biomedical Instrumentation Laboratory, Institute of Biology and Faculty of Engineering, State University of Rio de Janeiro, Rio de Janeiro, Brazil; 2Pulmonary Function Laboratory, Pedro Ernesto University Hospital, Faculty of Medical Sciences, State University of Rio de Janeiro, Rio de Janeiro, Brazil; 3Pulmonary Rehabilitation Laboratory, Augusto Motta University Center, Rio de Janeiro, Brazil; 4Laboratory of Clinical and Experimental Research in Vascular Biology - Biomedical Center, State University of Rio de Janeiro, Rio de Janeiro, BrazilCorrespondence: Pedro Lopes de Melo, Rua São Francisco Xavier 524, Pavilhão Haroldo Lisboa da Cunha, Sala 104, Maracanã, Rio de Janeiro, RJ, 20550-013, Brazil, Tel +55-21-2334-0705, Email plopes@uerj.brPurpose: Chronic obstructive pulmonary disease (COPD) phenotypes may introduce different characteristics that need to be known to improve treatment. Respiratory oscillometry provides a detailed analysis and may offer insight into the pathophysiology of COPD. In this paper, we used this method to evaluate the differences in respiratory mechanics of COPD phenotypes.Patients and Methods: This study investigated a sample of 83 volunteers, being divided into control group (CG = 20), emphysema (n = 23), CB (n = 20) and asthma-COPD overlap syndrome (ACOS, n = 20). These analyses were performed before and after bronchodilator (BD) use. Functional capacity was evaluated using the Glittre‑ADL test, handgrip strength and respiratory pressures.Results: Initially it was observed that oscillometry provided a detailed description of the COPD phenotypes, which was consistent with the involved pathophysiology. A correlation between oscillometry and functional capacity was observed (r=− 0.541; p = 0.0001), particularly in the emphysema phenotype (r = − 0.496, p = 0.031). BD response was different among the studied phenotypes. This resulted in an accurate discrimination of ACOS from CB [area under the receiver operating curve (AUC) = 0.84] and emphysema (AUC = 0.82).Conclusion: These results offer evidence that oscillatory indices may enhance the comprehension and identification of COPD phenotypes, thereby potentially improving the support provided to these patients.Keywords: asthma-COPD overlap, emphysema, chronic bronchitis, respiratory impedance, handgrip analysis, Glittre-ADL test, forced oscillation technique, bronchodilator response

Abstract Background Intra-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. Methods History 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. Results Among 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. Conclusions Our 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.

Abstract Rationale Lung recruitment and continuous distending pressure (CDP) titration are critical for assuring the efficacy of high-frequency ventilation (HFOV) in preterm infants. The limitation of oxygenation (peripheral oxygen saturation, SpO2) in optimizing CDP calls for evaluating other non-invasive bedside measurements. Respiratory reactance (Xrs) at 10 Hz measured by oscillometry reflects lung volume recruitment and tissue strain. In particular, lung volume recruitment and decreased tissue strain result in increased Xrs values. Objectives In extremely preterm infants treated with HFOV as first intention, we aimed to measure the relationship between CDP and Xrs during SpO2-driven CDP optimization. Methods In this prospective observational study, extremely preterm infants born before 28 weeks of gestation undergoing SpO2-guided lung recruitment maneuvers were included in the study. SpO2 and Xrs were recorded at each CDP step. The optimal CDP identified by oxygenation (CDPOpt_SpO2) was compared to the CDP providing maximal Xrs on the deflation limb of the recruitment maneuver (CDPXrs). Results We studied 40 infants (gestational age at birth = 22+ 6-27+ 5 wk; postnatal age = 1–23 days). Measurements were well tolerated and provided reliable results in 96% of cases. On average, Xrs decreased during the inflation limb and increased during the deflation limb. Xrs changes were heterogeneous among the infants for the amount of decrease with increasing CDP, the decrease at the lowest CDP of the deflation limb, and the hysteresis of the Xrs vs. CDP curve. In all but five infants, the hysteresis of the Xrs vs. CDP curve suggested effective lung recruitment. CDPOpt_SpO2 and CDPXrs were highly correlated (ρ = 0.71, p

Rationale: Respiratory resistance (Rrs) and reactance (Xrs) as measured by oscillometry and their intrabreath changes have emerged as sensitive parameters for detecting early pathological impairments during tidal breathing. Objectives: This study evaluates the prevalence and association of abnormal oscillometry parameters with respiratory symptoms and respiratory diseases in a general adult population. Methods: A total of 7,560 subjects in the Austrian LEAD (Lung, hEart, sociAl, boDy) Study with oscillometry measurements (computed with the Resmon Pro FULL; Restech Srl) were included in this study. The presence of respiratory symptoms and doctor-diagnosed respiratory diseases was assessed using an interview-based questionnaire. Rrs and Xrs at 5 Hz, their inspiratory and expiratory components, the area above the Xrs curve, and the presence of tidal expiratory flow limitation were analyzed. Normality ranges for oscillometry parameters were defined. Measurements and Main Results: The overall prevalence of abnormal oscillometry parameters was 20%. The incidence of abnormal oscillometry increased in the presence of symptoms or diagnoses: 17% (16–18%) versus 27% (25–29%), P < 0.0001. All abnormal oscillometry parameters except Rrs at 5 Hz were significantly associated with respiratory symptoms/diseases. Significant associations were found, even in subjects with normal spirometry, with abnormal oscillometry incidence rates increasing by 6% (4–8%; P < 0.0001) in subjects with symptoms or diagnoses. Conclusions: Abnormal oscillometry parameters are present in one-fifth of this adult population and are significantly associated with respiratory symptoms and disease. Our findings underscore the potential of oscillometry as a tool for detecting and evaluating respiratory impairments, even in individuals with normal spirometry. [ABSTRACT FROM AUTHOR]

Abstract Background Lung function analysis in Parkinson's disease (PD) is often difficult due to the demand for adequate forced expiratory maneuvers. Respiratory oscillometry exams require onlyquiet tidal breathing and provide a detailed analysis of respiratory mechanics. We hypothesized that oscillometry would simplify the diagnosis of respiratory abnormalitiesin PD and improve our knowledge about the pathophysiological changes in these patients. Materials and methods This observational study includes 20 controls and 47 individuals with PD divided into three groups (Hoehn and Yahr Scale 1–1.5; H&Y scale 2–3 and PD smokers).The diagnostic accuracy was evaluated by investigating the area under the receiver operating characteristic curve (AUC). Results Initial stages are related to increased peripheral resistance (Rp; p = 0.001). In more advanced stages, a restrictive pattern is added, reflected by reductions in dynamic compliance (p

To date both the clinical management and our understanding of respiratory disease have benefitted from widely available tests like spirometry, plethysmography and gas transfer. In recent years, however, there has been a growing interest in the use of more sensitive diagnostic tools in evaluating respiratory disorders. In this context, oscillometry applied to the study of small airways is emerging, and an interesting cohort of subjects of study is represented by the high-risk population undergoing CT lung cancer screening in the RISP program. The aim of the study is to characterize, in this cohort, patients with evidence of emphysema on low- dose chest CT and investigate their clinical and functional characteristics with spirometry and oscillometry. [ABSTRACT FROM AUTHOR]

Ensuring the vibration reliability of rotary machines is based on the reliable mathematical model of rotor movement. Considering the critical factors leading to a stability loss is an important problem in up-to-date machinery. However, the presence of fractional-order hydrodynamic features of gap seals and the effect of anomalous energy dissipation lead to a need to clarify existing rotordynamic models by considering the fractional-order terms. Therefore, this article deals with the comprehensive modeling approach to study forced oscillations of a single-mass rotor and check its dynamic stability considering the fractional-order origin of the damping force. Moreover, the impact of fractional order on the damping factor and dynamic stability of whirl movement considering the circulation force in gap seals, is still not fully explored. This problem adds particular importance to the presented research. As a result, a single-mass flexible rotor model was extended by considering the fractional-order damping force. Moreover, based on the discovered asymptotic property of the Mittag-Leffler function, the impact of fractional order on the amplitude-frequency response was also determined. Finally, boundaries for dynamic stability loss were identified considering the fractional-order damping force. Overall, the study allowed the development and substantiation of a more generalized scientific and methodological approach to ensuring the vibration reliability of rotary machines.

The fact that some SARS-CoV-2 pneumonia patients benefit from changing body position, and some from continuous positive airways pressure (CPAP), indicates the functional character of hypoxia. We hypothesize that such effects could be explained by the closure of small airways. To prove the hypothesis, we evaluated the patency of small airways in 30 oxygen-dependent, spontaneously breathing patients with SARS-CoV-2 pneumonia during their hospital stay using the FOT method and then compared the results with data obtained three months later. During the acute period, total resistance (R5) and peripheral resistance (R5-20) rose above the upper limit of normal (ULN) in 28% and 50% of all patients, respectively. Reactance indices X5, AX and Fres exceeded ULN in 55%, 68% and 66% of cases. Significant correlations were observed between PaO2/FiO2, the time spent in the hospital and R5, X5, AX and Fres. After 3 months, 18 patients were re-examined. During the hospital stay, 11 of them had risen above the upper limit of normal (ULN), for both resistance (R5-20) and reactance (X5, AX) values. Three months later, ULN for R5-20 was exceeded in only four individuals, but ULN for X5 and AX was exceeded in five individuals. Lung function examination revealed a combined restrictive/obstructive ventilatory failure and reduced CO transfer factor. We interpret these changes as lung tissue remodeling due to the process of fibrosis. We conclude that during acute period of SARS-CoV-2 pneumonia, dilated pulmonary blood vessels and parenchymal oedema induce functional closure of small airways, which in turn induce atelectasis with pulmonary right-to-left shunting, followed by the resulting hypoxemia.

Scoliosis is a condition that affects the spine and causes chest rotation and trunk distortion. Individuals with severe deformities may experience dyspnea on exertion and develop respiratory failure. Respiratory oscillometry is a simple and non-invasive method that provides detailed information on lung mechanics. This work aims to investigate the potential of oscillometry in the evaluation of respiratory mechanics in patients with scoliosis and its association with physical performance. We analyzed 32 volunteers in the control group and 32 in the scoliosis group. The volunteers underwent traditional pulmonary function tests, oscillometry, and the 6-minute walk test (6MWT). Oscillometric analysis showed increased values of resistance at 4 Hz (R4, P

Ensuring the vibration reliability of rotary machines is based on the reliable mathematical model of rotor movement. Considering the critical factors leading to a stability loss is an important problem in up-to-date machinery. However, the presence of fractional-order hydrodynamic features of gap seals and the effect of anomalous energy dissipation lead to a need to clarify existing rotordynamic models by considering the fractional-order terms. Therefore, this article deals with the comprehensive modeling approach to study forced oscillations of a single-mass rotor and check its dynamic stability considering the fractional-order origin of the damping force. Moreover, the impact of fractional order on the damping factor and dynamic stability of whirl movement considering the circulation force in gap seals, is still not fully explored. This problem adds particular importance to the presented research. As a result, a single-mass flexible rotor model was extended by considering the fractional-order damping force. Moreover, based on the discovered asymptotic property of the Mittag-Leffler function, the impact of fractional order on the amplitude-frequency response was also determined. Finally, boundaries for dynamic stability loss were identified considering the fractional-order damping force. Overall, the study allowed the development and substantiation of a more generalized scientific and methodological approach to ensuring the vibration reliability of rotary machines. [ABSTRACT FROM AUTHOR]

Primary ciliary dyskinesia (PCD) is an autosomal recessive disorder that results from the dysfunction of motile cilia, which can cause chronic upper and lower respiratory infections leading to bronchiectasis. However, there is a need for additional tools to monitor the progression of bronchiectasis in PCD. The forced oscillation technique (FOT) is an effort-independent lung function test that can be used to evaluate respiratory mechanics. In this retrospective study, we aimed to describe the radiographic findings associated with respiratory impedance (resistance (Rrs) and reactance (Xrs)) measured by FOT in six adult PCD patients and one pediatric with the (RSPH4A (c.921+3_921+6delAAGT (intronic)) founder mutation. We compared the radiographic findings on a high-resolution chest computed tomography (CT) scan with the FOT results. Our findings suggest that respiratory impedance measured by FOT may be a valuable tool for detecting and monitoring the progression of bronchiectasis in PCD patients with the (RSPH4A (c.921+3_921+6delAAGT (intronic)) founder mutation. However, further research is necessary to validate these results and determine the sensitivity and specificity of bronchiectasis monitoring in PCD patients with other genetic mutations. [ABSTRACT FROM AUTHOR]

Abstract Background In this work, we developed many machine learning classifiers to assist in diagnosing respiratory changes associated with sarcoidosis, based on results from the Forced Oscillation Technique (FOT), a non-invasive method used to assess pulmonary mechanics. In addition to accurate results, there is a particular interest in their interpretability and explainability, so we used Genetic Programming since the classification is made with intelligible expressions and we also evaluate the feature importance in different experiments to find the more discriminative features. Methodology/principal findings We used genetic programming in its traditional tree form and a grammar-based form. To check if interpretable results are competitive, we compared their performance to K-Nearest Neighbors, Support Vector Machine, AdaBoost, Random Forest, LightGBM, XGBoost, Decision Trees and Logistic Regressor. We also performed experiments with fuzzy features and tested a feature selection technique to bring even more interpretability. The data used to feed the classifiers come from the FOT exams in 72 individuals, of which 25 were healthy, and 47 were diagnosed with sarcoidosis. Among the latter, 24 showed normal conditions by spirometry, and 23 showed respiratory changes. The results achieved high accuracy (AUC > 0.90) in two analyses performed (controls vs. individuals with sarcoidosis and normal spirometry and controls vs. individuals with sarcoidosis and altered spirometry). Genetic Programming and Grammatical Evolution were particularly beneficial because they provide intelligible expressions to make the classification. The observation of which features were selected most frequently also brought explainability to the study of sarcoidosis. Conclusions The proposed system may provide decision support for clinicians when they are struggling to give a confirmed clinical diagnosis. Clinicians may reference the prediction results and make better decisions, improving the productivity of pulmonary function services by AI-assisted workflow.

Introduction: We evaluate the accuracy of postnatal biochemical and lung function tests performed within 3 h from birth for predicting surfactant need in preterm infants ≤34 weeks' gestation receiving noninvasive respiratory support for respiratory distress syndrome (RDS). Methods: We systematically searched MEDLINE, Embase, The Cochrane Library, PROSPERO, and clinicaltrials.gov databases for studies published from 2000 to November 10, 2021, cross-referencing relevant literature and contacting experts. We included diagnostic accuracy studies and systematic reviews of biochemical or lung function tests identifying the need for surfactant in preterm neonates ≤34 weeks' with RDS not intubated at birth. The authors individually assessed the risk of bias following a tailored QUADAS-2 tool. Results: Eight studies, including 810 infants, met the inclusion criteria. Four tests were included: the click test, the stable microbubble test, the lamellar body count on gastric aspirates, and the forced oscillation technique. The reference standards were transparent criteria for distinguishing the infants according to oxygen requirement, which reflected the current criteria for surfactant therapy. The risk of bias was judged high because of the population selection and exclusion of participants from the analysis. There were no serious concerns regarding blinding and applicability. The individual study sensitivity and specificity range from 0.60 to 1 and from 0.51 to 0.91, respectively. It was not appropriate to combine the accuracy estimates in a meta-analysis because of the heterogeneity of the study characteristics. Conclusions: Current evidence is insufficient to recommend biochemical and lung function tests for tailoring surfactant therapy. [ABSTRACT FROM AUTHOR]

Yuji Yamamoto,1 Haruhiko Hirata,1 Takayuki Shiroyama,1 Tomoki Kuge,1 Kinnosuke Matsumoto,1 Midori Yoneda,1 Makoto Yamamoto,1 Yujiro Naito,1 Yasuhiko Suga,1 Kiyoharu Fukushima,1 Kotaro Miyake,1 Shohei Koyama,1 Kota Iwahori,1 Izumi Nagatomo,1 Yoshito Takeda,1 Atsushi Kumanogoh1– 4 1Department of Respiratory Medicine and Clinical Immunology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan; 2Department of Immunopathology, WPI, Immunology Frontier Research Center (iFReC), Osaka University, Suita, Osaka, Japan; 3Integrated Frontier Research for Medical Science Division, Institute for Open and Transdisciplinary Research Initiatives (OTRI), Osaka University, Suita, Osaka, Japan; 4Center for Infectious Diseases for Education and Research (CiDER), Osaka University, Suita, Osaka, JapanCorrespondence: Yuji Yamamoto, Department of Respiratory Medicine and Clinical Immunology, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka, 565-0871, Japan, Tel +81 6-36879-3833, Fax +81 6-6879-3839, Email cyyamamoto1110@gmail.comPurpose: Pulmonary fibrosis and emphysema result in relatively maintained ventilation and reduced diffusing capacity. This pulmonary functional impairment complicates the evaluation of pulmonary function in patients with combined pulmonary fibrosis and emphysema (CPFE). Therefore, a single and easy-to-use pulmonary function index to evaluate patients with CPFE warrants further studies. Respiratory impedance can easily be provided by oscillometry and might be a candidate index to evaluate pulmonary function in patients with CPFE. As a preliminary study to assess the utility of respiratory impedance, we investigated the associations of physiological indices, including respiratory impedance, in patients with idiopathic pulmonary fibrosis (IPF) with and without emphysema.Patients and Methods: This retrospective study evaluated patients with IPF who did and did not satisfy the diagnostic criteria of CPFE. All patients underwent oscillometry, spirometry, and diffusing capacity for carbon monoxide (DLCO). Correlations of the obtained physiological indices were analyzed.Results: In total, 47 patients were included (18 and 29 patients with CPFE and IPF, respectively). Respiratory reactance (Xrs) at 5 Hz (X5) in the inspiratory phase was associated with forced vital capacity (FVC) % predicted in patients with CPFE (rS=0.576, P=0.012) and IPF (rS=0.539, P=0.003). Inspiratory X5 positively correlated with DLCO % predicted only in patients CPFE (rS=0.637, P=0.004).Conclusion: Emphysema might associate Xrs with ventilation and diffusing capacity in patients with IPF and emphysema. Given the multiple correlations of Xrs with FVC and DLCO, this study warrants further studies to verify the utility of oscillometry in a large-scale study for patients with CPFE.Keywords: chronic obstructive pulmonary disease, forced oscillation technique, gas exchange, idiopathic pulmonary fibrosis, ventilation

Objective: To develop regression equations to predict forced oscillation technique (FOT) parameters in Indian children and adolescents. Methods: Lung function was assessed in a multigeographic cohort of residential school children using a portable FOT-based device (PulmoScan) and spirometry. FOT measurements were performed in 1497 study participants, aged 9–19 y, from 8 Indian districts. Bland–Altman analysis was performed for additional 32 adult subjects to compare the results of PulmoScan to a standard IOS device in an outpatient setting. Reference equations were developed for Rrs and Xrs from the data of healthy subjects with normal spirometry using multivariate regression model for Indo-European, Dravidian, and mixed ethnic groups. Results: X5 (bias = 0.02) showed a better agreement than resistance parameters (R5 bias = 0.75, R20 bias = −0.22) in IOS/PulmoScan comparison. Anthropometric variables (age, height, and weight) were positively correlated with reactance (X5) and negatively with resistance parameters (R5, R10, R15, and R20), with most associations being stronger in boys. Final regression model considered ethnicity as a key determinant along with anthropometry. Conclusion: Multiethnic reference equations were developed for Indian children aged 9–19 y based on a novel handheld FOT device. [ABSTRACT FROM AUTHOR]

Abstract Background Dupilumab, an anti-IL-4α receptor antibody, is a new treatment for severe or refractory asthma. However, real-world evidence on the efficacy of dupilumab in patients with mild to moderate bronchial asthma is lacking. Methods We retrospectively evaluated the effects of dupilumab in 62 patients who received dupilumab for eosinophilic sinusitis comorbid with asthma at a single centre in Japan. Type 2 inflammatory markers, ACT, respiratory function tests, and forced oscillation technique (FOT) were analysed before, three months after, and one year after dupilumab administration, mainly in patients with mild to moderate asthma. Results FEV1, %FEV1, %FVC, treatment steps for asthma and ACT improved significantly after three months of dupilumab treatment. FeNO was markedly decreased, whereas IgE and eosinophil counts showed no significant changes. Pre- and post-treatment respiratory resistance (Rrs) and respiratory reactance (Xrs) correlated significantly with FEV1. Improvement in %FEV1 was associated with higher FeNO and higher serum IgE before dupilumab treatment. Conclusion Dupilumab treatment for sinusitis may improve respiratory functions, asthma symptoms, and asthma treatment reduction, even if the associated bronchial asthma is not severe.

Caroline Oliveira Ribeiro,1 Agnaldo José Lopes,2,3 Pedro Lopes de Melo1 1Biomedical Instrumentation Laboratory, Institute of Biology and Faculty of Engineering, State University of Rio de Janeiro, Rio de Janeiro, Brazil; 2Pulmonary Function Laboratory, State University of Rio de Janeiro, Rio de Janeiro, Brazil; 3Pulmonary Rehabilitation Laboratory, Augusto Motta University Center, Rio de Janeiro, BrazilCorrespondence: Pedro Lopes de Melo, Rua São Francisco Xavier 524, Pavilhão Haroldo Lisboa da Cunha, Sala 104, Maracanã, Rio de Janeiro, 20550-013, Brazil, Tel +55-21-2334-0705, Email plopes@uerj.brPurpose: Respiratory oscillometry has emerged as a powerful method for detecting respiratory abnormalities in COPD. However, this method has not been widely introduced into clinical practice. This limitation arises, at least in part, because the clinical meaning of the oscillometric parameters is not clear. In this paper, we evaluated the association of oscillometry with functional capacity and its ability to predict abnormal functional capacity in COPD.Patients and Methods: This cross-sectional study investigated a control group formed by 30 healthy subjects and 30 outpatients with COPD. The subjects were classified by the Glittre‑ADL test and handgrip strength according to the functional capacity.Results: This study has shown initially that subjects with abnormal functional capacity had a higher value for resistance (p < 0.05), reactance area (Ax, p < 0.01), impedance modulus (Z4, p < 0.05), and reduced dynamic compliance (Cdyn, p < 0.05) when compared with subjects with normal functional capacity. This resulted in significant and consistent correlations among resistive oscillometric parameters (R=− 0.43), Cdyn (R=− 0.40), Ax (R = 0.42), and Z4 (R = 0.41) with exercise performance. Additionally, the effects of exercise limitation in COPD were adequately predicted, as evaluated by the area under the curve (AUC) obtained by receiver operating characteristic analysis. The best parameters for this task were R4-R20 (AUC = 0.779) and Ax (AUC = 0.752).Conclusion: Respiratory oscillometry provides information related to functional capacity in COPD. This method is also able to predict low exercise tolerance in these patients. These findings elucidate the physiological and clinical meaning of the oscillometric parameters, improving the interpretation of these parameters in COPD patients.Keywords: chronic obstructive pulmonary disease, COPD physiopathology, forced oscillation technique, respiratory impedance, Glittre-ADL test, handgrip strength, exercise limitation

The article discusses the results of a study on the effectiveness of spirometry and forced oscillation technique in reducing thoracic compliance. Topics mentioned include the measurement of impedance to air flow due to airway resistance and respiratory system compliance, some limitations associated with spirometry, and the influence of chest restriction on total lung capacity.

Simple Summary: Forced oscillation technique allows assessment of the respiratory system impedance, free from patient-dependent factors. Our study is the first to evaluate whether the implementation of physical activity has an influence on oscillometric results in patients after thoracic surgery due to lung cancer. The results indicate that despite the 6-min walking test and hand strength improvements, pulmonary rehabilitation has no impact on oscillometric values in this group of patients. Background: Thoracic surgery is a recommended treatment option for non-small cell lung cancer patients. An important part of a patient's therapy, which helps to prevent postoperative complications and improve quality of life, is pulmonary rehabilitation (PR). The aim of this study was to assess whether the implementation of physical activity has an influence on forced oscillation technique (FOT) values in patients after thoracic surgery due to lung cancer. Methods: In this observational study, we enrolled 54 patients after thoracic surgery due to lung cancer, 49 patients with idiopathic interstitial fibrosis (IPF), and 54 patients with chronic obstructive pulmonary disease/asthma–COPD overlap (COPD/ACO). All patients were subjected to three weeks of in-hospital PR and assessed at the baseline as well as after completing PR by FOT, spirometry, grip strength measurement, and the 6-min walk test (6MWT). Results: We observed differences between FOT values under the influence of physical activity in studied groups, mostly between patients after thoracic surgery and COPD/ACO patients; however, no significant improvement after completing PR among FOT parameters was noticed in any group of patients. Improvements in the 6MWT distance, left hand strength, and right hand strength after PR were noticed (p < 0.001, 0.002, and 0.012, respectively). Conclusions: Three weeks of pulmonary rehabilitation had no impact on FOT values in patients after thoracic surgery due to lung cancer. Instead, we observed improvements in the 6MWT distance and the strength of both hands. Similarly, no FOT changes were observed in IPF and COPD/ACO patients after completing PR. [ABSTRACT FROM AUTHOR]

Background: In this work, we developed many machine learning classifiers to assist in diagnosing respiratory changes associated with sarcoidosis, based on results from the Forced Oscillation Technique (FOT), a non-invasive method used to assess pulmonary mechanics. In addition to accurate results, there is a particular interest in their interpretability and explainability, so we used Genetic Programming since the classification is made with intelligible expressions and we also evaluate the feature importance in different experiments to find the more discriminative features.Methodology/principal Findings: We used genetic programming in its traditional tree form and a grammar-based form. To check if interpretable results are competitive, we compared their performance to K-Nearest Neighbors, Support Vector Machine, AdaBoost, Random Forest, LightGBM, XGBoost, Decision Trees and Logistic Regressor. We also performed experiments with fuzzy features and tested a feature selection technique to bring even more interpretability. The data used to feed the classifiers come from the FOT exams in 72 individuals, of which 25 were healthy, and 47 were diagnosed with sarcoidosis. Among the latter, 24 showed normal conditions by spirometry, and 23 showed respiratory changes. The results achieved high accuracy (AUC > 0.90) in two analyses performed (controls vs. individuals with sarcoidosis and normal spirometry and controls vs. individuals with sarcoidosis and altered spirometry). Genetic Programming and Grammatical Evolution were particularly beneficial because they provide intelligible expressions to make the classification. The observation of which features were selected most frequently also brought explainability to the study of sarcoidosis.Conclusions: The proposed system may provide decision support for clinicians when they are struggling to give a confirmed clinical diagnosis. Clinicians may reference the prediction results and make better decisions, improving the productivity of pulmonary function services by AI-assisted workflow. [ABSTRACT FROM AUTHOR]

Measurement of respiratory impedance ( Z rs ) in intubated patients requires accurate compensation for pressure losses across the endotracheal tube (ETT). In this study, we compared time-domain (TD), frequency-domain (FD) and combined time-/frequency-domain (FT) methods for ETT compensation. We measured total impedance ( Z tot ) of a test lung in series with three different ETT sizes, as well as in three intubated porcine subjects. Pressure measurement at the distal end of the ETT was used to determine the true Z rs . For TD compensation, pressure distal to the ETT was obtained based on its resistive and inertial properties, and the corresponding Z rs was estimated. For FD compensation, impedance of the isolated ETT was obtained from oscillatory flow and pressure waveforms, and then subtracted from Z tot . For TF compensation, the nonlinear resistive properties of the ETT were subtracted from the proximal pressure measurement, from which the linear resistive and inertial ETT properties were removed in the frequency-domain to obtain Z rs . The relative root mean square error between the actual and estimated Z rs ( r R M S E , Z ^ rs ) showed that TD compensation yielded the least accurate estimates of Z rs for the in vitro experiments, with small deviations observed at higher frequencies. The FD and TF compensations yielded estimates of Z rs with similar accuracies. For the porcine subjects, no significant differences were observed in r R M S E , Z ^ rs across compensation methods. FD and TF compensation of the ETT may allow for accurate oscillometric estimates of Z rs in intubated subjects, while avoiding the difficulties associated with direct tracheal pressure measurement. [ABSTRACT FROM AUTHOR]

Abstract Background Tidal expiratory flow limitation (EFLT) is common among COPD patients. Whether EFLT changes during sleep and can be abolished during home ventilation is not known. Methods COPD patients considered for noninvasive ventilation used a ventilator which measured within-breath reactance change at 5 Hz (∆Xrs) and adjusted EPAP settings to abolish EFLT. Participants flow limited (∆Xrs > 2.8) when supine underwent polysomnography (PSG) and were offered home ventilation for 2 weeks. The EPAP pressure that abolished EFLT was measured and compared to that during supine wakefulness. Ventilator adherence and subjective patient perceptions were obtained after home use. Results Of 26 patients with supine EFLT, 15 completed overnight PSG and 10 the home study. In single night and 2-week home studies, EFLT within and between participants was highly variable. This was unrelated to sleep stage or body position with only 14.6% of sleep time spent within 1 cmH2O of the awake screening pressure. Over 2 weeks, mean EPAP was almost half the mean maximum EPAP (11.7 vs 6.4 cmH2O respectively). Group mean ∆Xrs was ≤ 2.8 for 77.3% of their home use with a mean time to abolish new EFLT of 5.91 min. Adherence to the ventilator varied between 71 and 100% in prior NIV users and 36–100% for naïve users with most users rating therapy as comfortable. Conclusions Tidal expiratory flow limitation varies significant during sleep in COPD patients. This can be controlled by auto-titrating the amount of EPAP delivered. This approach appears to be practical and well tolerated by patients. Trial registration: The trial was retrospectively registered at CT.gov NCT04725500.

Primary ciliary dyskinesia (PCD) is an autosomal recessive disorder that results from the dysfunction of motile cilia, which can cause chronic upper and lower respiratory infections leading to bronchiectasis. However, there is a need for additional tools to monitor the progression of bronchiectasis in PCD. The forced oscillation technique (FOT) is an effort-independent lung function test that can be used to evaluate respiratory mechanics. In this retrospective study, we aimed to describe the radiographic findings associated with respiratory impedance (resistance (Rrs) and reactance (Xrs)) measured by FOT in six adult PCD patients and one pediatric with the (RSPH4A (c.921+3_921+6delAAGT (intronic)) founder mutation. We compared the radiographic findings on a high-resolution chest computed tomography (CT) scan with the FOT results. Our findings suggest that respiratory impedance measured by FOT may be a valuable tool for detecting and monitoring the progression of bronchiectasis in PCD patients with the (RSPH4A (c.921+3_921+6delAAGT (intronic)) founder mutation. However, further research is necessary to validate these results and determine the sensitivity and specificity of bronchiectasis monitoring in PCD patients with other genetic mutations.

The complexity of the human respiratory system causes that one of the main methods of analyzing the dynamic pulmonary phenomena and interpreting experimental results are simulations of its computational models. Among the most compound elements of these models, apart from the bronchial tree structure, is the phenomenon of flow limitation in flexible bronchi, which causes them to collapse with increasing flow, thus their properties, such as resistance, compliance and inertance, are highly nonlinear and time‐varying. Commonly, this phenomenon is ignored, or a distributed model for the airway pressure drop is applied, simulated with a modified numerical solver of this differential equation (ODE). The disadvantages of this solution are the problems with taking into account the inherent singularity of the model and the long computation time due to iterative nature of the ODE procedure. The aim of the work was to derive an algebraic approximation of this distributed model, suitable for implementation in continuous dynamic models, to validate it by comparing the results of simulations with the respiratory system model including approximate and original (ODE solver) numerical procedures, as well as to evaluate possible acceleration of calculations. All simulations, including spontaneous breathing, mechanical ventilation with the optimal ventilatory waveform and forced expiration, proved that algebraic approximation yielded results negligibly differing from the ODE solution, and shortened the computation time by an order. The proposed approach is an attractive alternative in the case of computer implementations of pulmonary models, where simulations of flows and pressures in the complex respiratory system are of primary importance. [ABSTRACT FROM AUTHOR]

The forced oscillation technique (FOT) is a non-volitional assessment that is used during tidal breathing. A variant of FOT uses a pseudorandom noise (PRN) signal which we postulated might have utility in assessing lung function in prematurely born children. We, therefore, undertook a systematic review to evaluate the evidence regarding PRN FOT. A comprehensive search of the literature was conducted by using the following databases: Medline, Embase, Web of Science and CINAHL. Observational studies, case series/reports and randomized-controlled trials were eligible for inclusion. Article abstracts and full texts were screened independently by two reviewers, with disagreements resolved by discussion or a third reviewer if necessary. Five studies were included (n = 587 preterm children). Three compared PRN FOT with spirometry, and two compare it to the interrupter technique. Most studies failed to report comprehensive methodology of the frequency spectra used to generate the PRN signal. There was evidence that poorer lung function, as assessed by PRN FOT, was associated with a greater burden of respiratory symptoms, but there was insufficient evidence to determine whether PRN FOT performed better than other lung-function tests. Detailed methodological documentation, in accordance with ERS guidance, is needed to assess the benefits of PRN FOT prior to routine clinical incorporation to assess prematurely born children. [ABSTRACT FROM AUTHOR]

(1) Background: Pulmonary rehabilitation (PR) plays a significant therapeutic role for patients with idiopathic interstitial pneumonia (IIP). The study assessed the impact of physical activity on lung function measured by forced oscillation technique (FOT). (2) Methods: The study involved 48 patients with IIP subjected to a 3-week inpatient PR. The control group included IIP patients (n = 44) on a 3-week interval without PR. All patients were assessed at baseline and after 3 weeks of PR by FOT, spirometry, plethysmography, grip strength measurement and the 6-minute walk test. (3) Results: There were no significant changes in FOT measurements in the PR group, except for reduced reactance at 11 Hz, observed in both groups (p < 0.05). Patients who completed PR significantly improved their 6-min walk distance (6MWD) and forced vital capacity (FVC). The change in 6MWD was better in patients with higher baseline reactance (p = 0.045). (4) Conclusions: Patients with IIP benefit from PR by an increased FVC and 6MWD; however, no improvement in FOT values was noticed. Slow disease progression was observed in the study and control groups, as measured by reduced reactance at 11 Hz. Patients with lower baseline reactance limitations achieve better 6MWD improvement. [ABSTRACT FROM AUTHOR]

Background: Dupilumab, an anti-IL-4α receptor antibody, is a new treatment for severe or refractory asthma. However, real-world evidence on the efficacy of dupilumab in patients with mild to moderate bronchial asthma is lacking.Methods: We retrospectively evaluated the effects of dupilumab in 62 patients who received dupilumab for eosinophilic sinusitis comorbid with asthma at a single centre in Japan. Type 2 inflammatory markers, ACT, respiratory function tests, and forced oscillation technique (FOT) were analysed before, three months after, and one year after dupilumab administration, mainly in patients with mild to moderate asthma.Results: FEV1, %FEV1, %FVC, treatment steps for asthma and ACT improved significantly after three months of dupilumab treatment. FeNO was markedly decreased, whereas IgE and eosinophil counts showed no significant changes. Pre- and post-treatment respiratory resistance (Rrs) and respiratory reactance (Xrs) correlated significantly with FEV1. Improvement in %FEV1 was associated with higher FeNO and higher serum IgE before dupilumab treatment.Conclusion: Dupilumab treatment for sinusitis may improve respiratory functions, asthma symptoms, and asthma treatment reduction, even if the associated bronchial asthma is not severe. [ABSTRACT FROM AUTHOR]

Vocal cord dysfunction (VCD) often coexists with asthma and exacerbates respiratory symptoms. A noninvasive method could be considered beneficial for the detection and follow-up of VCD complicated by asthma. Here, we report a case of VCD complicated by asthma, highlighting the effectiveness of colored three-dimensional (3-D) imaging of respiratory impedance using a broadband frequency forced oscillation technique (MostGraph). A 74-year-old woman with difficult-to-treat asthma, in whom mepolizumab treatment was ineffective, was referred to our hospital. Stridulous sounds were loudest over the anterior neck. Pulmonary function tests' results were normal; however, a flattening of the inspiratory flow-volume curve was detected. Remarkably, prominent spikes were observed in the inspiratory phase in the colored 3-D imaging of respiratory resistance, which was superimposed on increased respiratory resistance in the expiratory phase. Flexible laryngoscopy revealed the adduction of vocal cords on inspiration. The patient was diagnosed with asthma complicated by VCD. After successful treatment of VCD by speech therapy, inspiratory spikes of respiratory resistance disappeared, and normal vocal cord movement was observed on laryngoscopy. The present case report indicates the effectiveness of forced oscillometry in evaluating dynamic changes in respiratory resistance for detecting and monitoring VCD complicated by asthma. [ABSTRACT FROM AUTHOR]

Inhaling carbon dioxide (CO2) in humans is known to cause inconsistent effects on airway function. These could be due to direct effects of CO2 on airway smooth muscle or to changes in minute ventilation (VE). To address this issue, we examined the responses of the respiratory system to inhaled methacholine in healthy subjects and subjects with mild asthma while breathing air or gas mixtures containing 2% or 4% CO2. Respiratory mechanics were measured by a forced oscillation technique at 5 Hz during tidal breathing. At baseline, respiratory resistance (R5) was significantly higher in subjects with asthma (2.53 ± 0.38 cmH2O·L-1·s) than healthy subjects (2.11 ± 0.42 cmH2O·L-1·s) (P = 0.008) with room air. Similar values were observed with CO2 2% or 4% in the two groups. V_ E, tidal volume (VT), and breathing frequency (BF) significantly increased with CO2-containing mixtures (P < 0.001) with insignificant differences between groups. After methacholine, the increase in R5 and the decrease in respiratory reactance (X5) were significantly attenuated up to about 50% with CO2-containing mixtures instead of room air in both asthmatic (P < 0.001) and controls (P < 0.001). Mediation analysis showed that the attenuation of methacholine-induced changes in respiratory mechanics by CO2 was due to the increase in VE (P = 0.006 for R5 and P = 0.014 for X5) independently of the increase in VT or BF, rather than a direct effect of CO2. These findings suggest that the increased stretching of airway smooth muscle by the CO2-induced increase in VE is a mechanism through which hypercapnia can attenuate bronchoconstrictor responses in healthy subjects and subjects with mild asthma. [ABSTRACT FROM AUTHOR]

Abstract Introduction The use of machine learning (ML) methods would improve the diagnosis of respiratory changes in systemic sclerosis (SSc). This paper evaluates the performance of several ML algorithms associated with the respiratory oscillometry analysis to aid in the diagnostic of respiratory changes in SSc. We also find out the best configuration for this task. Methods Oscillometric and spirometric exams were performed in 82 individuals, including controls (n = 30) and patients with systemic sclerosis with normal (n = 22) and abnormal (n = 30) spirometry. Multiple instance classifiers and different supervised machine learning techniques were investigated, including k-Nearest Neighbors (KNN), Random Forests (RF), AdaBoost with decision trees (ADAB), and Extreme Gradient Boosting (XGB). Results and discussion The first experiment of this study showed that the best oscillometric parameter (BOP) was dynamic compliance, which provided moderate accuracy (AUC = 0.77) in the scenario control group versus patients with sclerosis and normal spirometry (CGvsPSNS). In the scenario control group versus patients with sclerosis and altered spirometry (CGvsPSAS), the BOP obtained high accuracy (AUC = 0.94). In the second experiment, the ML techniques were used. In CGvsPSNS, KNN achieved the best result (AUC = 0.90), significantly improving the accuracy in comparison with the BOP (p

Background: Lung function testing is recommended for the management of asthma. Due to certain limitations of conventional spirometry in vulnerable patients, forced oscillation technique (FOT) has been studied with promising results. As there is a paucity of data from developing world, we planned to conduct this study in children using FOT. To assess airway reversibility after inhaled salbutamol in asymptomatic children with suspected asthma. Settings: This study was conducted at pediatric asthma clinic of a tertiary care referral hospital in North India. Design: This was a prospective interventional study over 1-year period. Subjects and Methods: Asymptomatic children between 2 and 18 years of age, with history suggestive of asthma, were eligible for participation. Baseline and postbronchodilator pulmonary functions were assessed using FOT. Airway resistance and reactance were monitored at various frequencies. SPSS version 17 was used for statistical analysis. Results: Among the 345 enrolled children, baseline mean ± standard deviation total airway resistance (R5), central airway resistance (R19), peripheral airway resistance (R5–R19), reactance (X5), and resonant frequency (Fres) were 6.85 ± 2.60, 5.23 ± 1.93, 1.6 ± 1.16, and − 2.54 ± 1.36 cmH2O/L/s and 17.28 ± 3.06 Hz. The median (interquartile range) percentage change after inhaled salbutamol was 19.9 (11.40, 29.12), 22.86 (6.88, 38.76), 14.08 (3.40, 22.62), 39.20 (8.20, 62.39), and 15.79 (8.33, 27.27) in respective parameters. All changes were statistically significant. The studied respiratory variables were in maximum negative correlation with height, followed by body mass index. Conclusions: FOT is a simple technique for monitoring lung functions in children during asthma management.

OBJECTIVE: The present study was aimed to evaluate the diagnostic accuracy of impedance parameters to detect airflow obstruction and the severity of airflow obstruction in adults. METHODS: The spirometry parameters (forced expiratory volume in 1 s [FEV1], forced vital capacity [FVC], FEV1/FVC, FVC3/FVC, and FEF25-75) and respiratory impedance parameters (R5, R19, R5-19, and X5) measured by forced oscillation technique of consecutive 299 adults (male: 186) were included in the present analysis. The Spearman correlation coefficient (ρ) was used to assess the correlations of impedance parameters with spirometry indices. The area under the curve (AUC) was used to assess respiratory impedance parameters' diagnostic accuracy. RESULTS: The mean age of the study population was 54.1 ± 12.3 years, and 99 individuals (33%) had airflow obstruction (FEV1/FVC < 0.70) in spirometry. All spirometry indices (% of predicted) showed a weak negative correlation with R5, R19, R5-19, and weak positive correlation with X5. The R5 >142% predicted and X5 >136% predicted had the maximum AUC (0.75) with a sensitivity of up to 56% and specificity up to 86% to identify airflow obstruction. The impedance parameters showed low concordance with the severity of airflow obstruction. CONCLUSION: Respiratory impedance parameters had insufficient sensitivity to diagnose airflow obstruction and the severity of obstruction in adults. Thus, impedance parameters cannot a substitute for spirometry in diagnosing obstructive lung function.

Signal disruptions in small animals during the realization of the Forced Oscillation Technique are a well-known cause of data loss as it leads to non-reliable estimations of the respiratory impedance. In this work, we assessed the effects of removing the disrupted epoch when a 3-seconds input signal composed of one and a half 2-seconds full cycle is used. We tested our hypothesis in 25 SAMR1 mice under different levels of bronchoconstriction due to methacholine administration by iv bolus injections in different doses (15 animals) and by iv continuous infusion in different infusion rates (10 animals). Signal disruptions were computationally simulated as sharp drops in the pressure signal within a short timescale, and signal processing was performed using own developed algorithms. We found that the model goodness of fit worsens when averaging techniques to estimate the input respiratory impedance are not used. However, no statistically significant differences were observed in the comparison between Constant Phase Model parameters of the full 3-s signal and the 2-s non disrupted epoch in all doses or infusion rates for both methacholine delivery strategies. The proposed technique presents reliable outcomes that can reduce animal use in Forced Oscillation Technique realization. [ABSTRACT FROM AUTHOR]

Background: Self‐reported exercise‐induced dyspnea (EID) is common among adolescents. Possible underlying pathologies are exercise‐induced bronchoconstriction (EIB) and laryngeal obstruction (EILO). The forced oscillation technique (FOT) may evaluate exercise‐induced changes in airway caliber. Aim: To investigate in adolescents the relationship between EID, EIB (post‐exercise fall in forced expiratory volume in 1s (FEV1)≥10%), EILO, and post‐exercise challenge changes in FOT parameters. Methods: One hundred and forty‐three subjects (97 with EID) of 13–15 years old underwent a standardized exercise challenge with FOT measurement and spirometry repeatedly performed between 2 and 30 min post‐exercise. EILO was studied in a subset of 123 adolescents. Subjects showing greater changes than the healthy subgroup in the modulus of the inspiratory impedance were considered FOT responders. Results: EID‐nonEIB subjects presented similar post‐exercise changes in all FOT parameters to nonEID‐nonEIB adolescents. Changes in all FOT parameters correlated with FEV1 fall. 45 of 97 EID subjects responded neither by FEV1 nor FOT to exercise. 19 and 18 subjects responded only by FEV1 (onlyFEV1responders) or FOT (onlyFOTresponders), respectively. Only a lower baseline forced vital capacity (FVC)%predicted and a higher FEV1/FVC distinguished the onlyFEV1responders from onlyFOTresponders. FOT parameters did not present specific post‐exercise patterns in EILO subjects. Conclusion: FOT can be used to identify post‐exercise changes in lower airway function. However, EID has a modest relation with both FEV1 and FOT responses, highlighting the need for objective testing. More research is needed to understand whether onlyFEV1responders and onlyFOTresponders represent different endotypes. [ABSTRACT FROM AUTHOR]

Abstract Background Tidal expiratory flow limitation (EFLT) promotes intrinsic PEEP (PEEPi) in patients with chronic obstructive pulmonary disease (COPD). Applying non-invasive ventilation (NIV) with an expiratory positive airway pressure (EPAP) matching PEEPi improves gas exchange, reduces work of breathing and ineffective efforts. We aimed to evaluate the effects of a novel NIV mode that continuously adjusts EPAP to the minimum level that abolishes EFLT. Methods This prospective, cross-over, open-label study randomized patients to one night of fixed-EPAP and one night of EFLT-abolishing-EPAP. The primary outcome was transcutaneous carbon dioxide pressure (PtcCO2). Secondary outcomes were: peripheral oxygen saturation (SpO2), frequency of ineffective efforts, breathing patterns and oscillatory mechanics. Results We screened 36 patients and included 12 in the analysis (age 72 ± 8 years, FEV1 38 ± 14%Pred). The median EPAP did not differ between the EFLT-abolishing-EPAP and the fixed-EPAP night (median (IQR) = 7.0 (6.0, 8.8) cmH2O during night vs 7.5 (6.5, 10.5) cmH2O, p = 0.365). We found no differences in mean PtcCO2 (44.9 (41.6, 57.2) mmHg vs 54.5 (51.1, 59.0), p = 0.365), the percentage of night time with PtcCO2 > 45 mm Hg was lower (62(8,100)% vs 98(94,100)%, p = 0.031) and ineffective efforts were fewer (126(93,205) vs 261(205,351) events/hour, p = 0.003) during the EFLT-abolishing-EPAP than during the fixed-EPAP night. We found no differences in oxygen saturation and lung mechanics between nights. Conclusion An adaptive ventilation mode targeted to abolish EFLT has the potential to reduce hypercapnia and ineffective efforts in stable COPD patients receiving nocturnal NIV. Trial registration: ClicalTrials.gov, NCT04497090. Registered 29 July 2020—Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04497090 .

Abstract Background Alveolar recruitment maneuvers enable easily reopening nonaerated lung regions via a transient elevation in transpulmonary pressure. To evaluate the effect of these maneuvers on respiratory resistance, we used an oscillatory technique during mechanical ventilation. This study was conducted to assess the effect of the alveolar recruitment maneuvers on respiratory resistance under routine anesthesia. We hypothesized that respiratory resistance at 5 Hz (R5) after the maneuver would be decreased after the lung aeration. Methods After receiving the ethics committee’s approval, we enrolled 33 patients who were classified with an American Society of Anesthesiologists physical status of 1, 2 or 3 and were undergoing general anesthesia for transurethral resection of a bladder tumor within a 12-month period from 2017 to 2018. The recruitment maneuver was performed 30 min after endotracheal intubation. The maneuver consisted of sustained manual inflation of the anesthesia reservoir bag to a peak inspiratory pressure of 40 cmH2O for 15 s, including 5 s of gradually increasing the peak inspiratory pressure. Respiratory resistance was measured using the forced oscillation technique before and after the maneuver, and the mean R5 was calculated during the expiratory phase. The respiratory resistance and ventilator parameter results were analyzed using paired Student’s t-tests, and p

Seigo Miyoshi,1 Hitoshi Katayama,1 Minoru Matsubara,2 Takahide Kato,1 Naohiko Hamaguchi,1 Osamu Yamaguchi1 1Department of Cardiology, Pulmonology, Hypertension and Nephrology, Ehime University Graduate School of Medicine, Toon, Ehime 791-0295, Japan; 2Department of Internal Medicine, Sumitomo Besshi Hospital, Niihama, Ehime 792-8543, JapanCorrespondence: Seigo MiyoshiDepartment of Cardiology, Pulmonology, Hypertension and Nephrology, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime 791-0295, JapanTel +81-89-960-5303Fax +81-89-960-5306Email seigom@m.ehime-u.ac.jpBackground and Objective: Spirometry is sometimes difficult to perform in elderly patients and patients with cognitive impairment. Forced oscillometry (FOT) is a simple, noninvasive technique used for measuring respiratory impedance. The aim of this study was to develop regression equations to estimate vital capacity (VC), forced vital capacity (FVC), and forced expiratory volume in 1 s (FEV1.0) on the basis of FOT indices and to evaluate the accuracy of these equations in patients with asthma, chronic obstructive pulmonary disease (COPD), and interstitial lung disease (ILD).Materials and Methods: We retrospectively included data on 683 consecutive patients with asthma (388), COPD (128), or ILD (167) in this study. We generated regression equations for VC, FVC, and FEV1.0 by multivariate linear regression analysis and used them to estimate the corresponding values. We determined whether the estimated data reflected spirometric indices.Results: Actual and estimated VC, FVC, and FEV1.0 values showed significant correlations (all r > 0.8 and P < 0.001) in all groups. Biases between the actual data and estimated data for VC, FVC, and FEV1.0 in the asthma group were − 0.073 L, − 0.069 L, and 0.017 L, respectively. The corresponding values were − 0.064 L, 0.027 L, and 0.069 L, respectively, in the COPD group and − 0.040 L, − 0.071 L, and − 0.002 L, respectively, in the ILD group. The estimated data in the present study did not completely correspond to the actual data. In addition, sensitivity for an FEV1.0/FVC ratio of < 0.7 and the diagnostic accuracy for the classification of COPD grade using estimated data were low.Conclusion: These results suggest that our method is not highly accurate. Further studies are needed to generate more accurate regression equations for estimating spirometric indices based on FOT measurements.Keywords: forced expiratory volume in 1 second, forced oscillation technique, forced vital capacity, spirometry, vital capacity

Masanori Yasuo,* Yoshiaki Kitaguchi,* Yayoi Tokoro, Makoto Kosaka, Yosuke Wada, Takumi Kinjo, Atsuhito Ushiki, Hiroshi Yamamoto, Masayuki Hanaoka The First Department of Internal Medicine, Shinshu University School of Medicine, Matsumoto, Japan*These authors contributed equally to this workCorrespondence: Masanori YasuoThe First Department of Internal Medicine, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, JapanTel +81 263 37 2631Fax +81 263 36 3722Email yasumasa@shinshu-u.ac.jpBackground: Obstructive ventilatory disturbances occur in both chronic obstructive pulmonary disease (COPD), a typical disease representative of peripheral airway obstruction, and central airway obstruction (CAO). Pulmonary function tests (PFTs), which depend on patient effort, are traditionally used to evaluate lung function. The forced oscillation technique (FOT) is an effort-independent method for examining lung function during tidal breathing. The FOT is used universally to assess respiratory function in patients with COPD. Several studies have measured FOT to assess ventilatory disturbances in CAO. The results showed that FOT measurements in patients with CAO were similar to those reported in patients with COPD. However, no studies have compared FOT measurements directly between CAO and COPD. The aim of this study was to identify differences in ventilatory disturbances between peripheral and central airway obstructions in COPD and CAO, before patients received pharmacological therapy or bronchoscopic interventions, respectively.Patients and Methods: We retrospectively included 16 patients with CAO (10 cases of tracheal obstruction and 6 cases of bronchial obstruction) and 75 treatment-naïve patients with COPD (60 cases in Global Initiative for Chronic Obstructive Lung Disease [GOLD] stage II and 15 cases in GOLD stage III) that were admitted from December 2013 to May 2017. Prior to treatment, patients were examined with the FOT and PFTs.Results: All parameters measured with the FOT in the inspiratory phase were significantly worse in patients with CAO than in patients with COPD. The PFTs showed that the CAO group had a significantly lower peak expiratory flow rate. In the airway wall thickening phenotype of COPD, a difference between the inspiratory and expiratory phases of the resonance frequency (ΔFres) was the best indicator for distinguishing between peripheral and central airway obstructions.Conclusion: This study compared differences between CAO and COPD (mainly GOLD stage II). We found that the FOT measurement, ΔFres, was the optimal indicator of the difference between the airway wall thickening COPD phenotype and CAO. Thus, the difference might be due to mechanical changes that occur in COPD with airway wall thickening.Keywords: forced oscillation technique, pulmonary function test, quality of life, central airway obstruction, COPD