Early detection of changes in lung mechanics with oscillometry following bariatric surgery in severe obesity

Effects of Weight Change and Weight Cycling on Lung Function in Overweight and Obese Adults

Rationale: Epidemiological studies have reported on the detrimental effects on lung function after natural, and thus limited, weight gain in unselected populations. Studies on bariatric surgery, on the contrary, have indicated large improvements in lung function after substantial weight loss. Objectives: To study the associations between profound weight loss or gain and pulmonary function within the same population. A second objective was to investigate the effect of weight cycling on pulmonary function. Methods: From our lung function database, we selected the records of subjects in follow-up for continuous positive airway pressure therapy for sleep apnea with a weight change of ⩾20 kg within 5 years. Lung function (N = 255) at baseline was normal except for a tendency toward mild restriction in morbid obesity. Within this sample, 73 subjects were identified with significant "weight cycling", defined as a ⩾10-kg opposite change in body weight before or after the ⩾20-kg weight change. Results: Weight change affected pulmonary function more in men than in women (P < 0.001). In men, forced vital capacity (FVC) increased an average of 1.4% predicted per unit of body mass index after weight loss and the reverse after weight gain, whereas women exhibited a smaller change of 0.9% predicted per unit of body mass index. Weight loss slightly increased the ratio of forced expiratory volume in 1 second to FVC and decreased the specific airway resistance, whereas the opposite occurred with weight gain. Greater effects of weight change on lung function were observed in leaner subjects (P = 0.02) and in older subjects (P < 0.002). Changes in total lung capacity followed the changes in FVC, with no change in residual volume, and the greatest change was observed in functional residual capacity. In subjects with weight cycling, the improvement in lung function due to weight loss was reversed by subsequent weight gain and vice versa. Conclusions: This study provides evidence that the detrimental effect of obesity on lung function is a passive and reversible process.

Respiratory issues in patients with multiple sclerosis as a risk factor during SARS-CoV-2 infection: a potential role for exercise

Coronavirus disease-2019 (COVID-19) is associated with cytokine storm and is characterized by acute respiratory distress syndrome (ARDS) and pneumonia problems. The respiratory system is a place of inappropriate activation of the immune system in people with multiple sclerosis (MS), and this may cause damage to the lung and worsen both MS and infections.The concerns for patients with multiple sclerosis are because of an enhance risk of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The MS patients pose challenges in this pandemic situation, because of the regulatory defect of autoreactivity of the immune system and neurological and respiratory tract symptoms. In this review, we first indicate respiratory issues associated with both diseases. Then, the main mechanisms inducing lung damages and also impairing the respiratory muscles in individuals with both diseases is discussed. At the end, the leading role of physical exercise on mitigating respiratory issues inducing mechanisms is meticulously evaluated.

Lung de-recruitment in the allergic asthma of obesity: evidence from an anatomically based inverse model

The increase in asthma associated with the obesity epidemic cannot simply be due to airway hyperresponsiveness from chronic lung compression because chronic lung compression is a feature of obesity in general. We therefore sought to investigate what other factors might be at play in the impaired lung function seen in obese individuals with asthma. We measured respiratory system impedance in four groups-Lean Control, Lean Allergic Asthma, Obese Control, and Obese Allergic Asthma-before and after administration of albuterol. Impedance measurements were fit with an anatomically based computational model of lung mechanics that represents the airway tree as a branching structure with a uniform degree of asymmetry and a fixed radius scaling ratio, γ, between branches of sequential order. The two model parameters that define the airway tree, γ and tracheal radius, varied only modestly between the four study groups, indicating relatively minor differences in airway caliber. In contrast, respiratory system elastance was 57, 34, 143, and 271 cmH2O/L, respectively, for the four groups, suggesting that obesity induced significant lung de-recruitment that was exacerbated by allergic asthma. In addition, when the radii of the individual branches of the airway tree were varied randomly, we found that roughly half the terminal airways had to be closed to have the model fit the data well. We conclude that de-recruitment of small airways is a particular feature of Obese Allergic Asthma, and this can be inferred from respiratory system impedance fit with an anatomically based computational model.NEW & NOTEWORTHY Using a novel anatomically based computational model to interpret oscillometry measurements of impedance, we show that respiratory system elastance is increased in obesity and is increased dramatically in individuals with obese allergic asthma. A significant component of this increased elastance in obese allergic asthma appears to be due to closure of small airways rather than alveolar atelectasis, and this closure is partially mitigated by albuterol. These findings potentially point to nonpharmacological therapies in obese allergic asthma aimed at recruiting closed airways.

From Beneath the Skin to the Airway Wall: Understanding the Pathological Role of Adipose Tissue in Comorbid Asthma-Obesity

This article provides a contemporary report on the role of adipose tissue in respiratory dysfunction. Adipose tissue is distributed throughout the body, accumulating beneath the skin (subcutaneous), around organs (visceral), and importantly in the context of respiratory disease, has recently been shown to accumulate within the airway wall: "airway-associated adipose tissue." Excessive adipose tissue deposition compromises respiratory function and increases the severity of diseases such as asthma. The mechanisms of respiratory impairment are inflammatory, structural, and mechanical in nature, vary depending on the anatomical site of deposition and adipose tissue subtype, and likely contribute to different phenotypes of comorbid asthma-obesity. An understanding of adipose tissue-driven pathophysiology provides an opportunity for diagnostic advancement and patient-specific treatment. As an exemplar, the potential impact of airway-associated adipose tissue is highlighted, and how this may change the management of a patient with asthma who is also obese. © 2023 American Physiological Society. Compr Physiol 13:4321-4353, 2023.

[Indications in Obesity Therapy - Surgeons First?]

Obesity is a growing problem worldwide. For the first time since 2010, more people have been overweight than underweight. In particular, obesity-associated diseases, above all type 2 diabetes mellitus, pose enormous challenges to the healthcare system. On July 3, 2020, the German Bundestag recognised obesity as a disease and initiated the development of a diseases management program (DMP), which is currently being drawn up. So far, the indication for treatment of obesity in Germany has been based on the S3 guideline "Surgery of obesity and metabolic diseases" of the DGAV from 2018 and the S3 guideline "Prevention and therapy of obesity" of the German Obesity Society e. V. from 2014. This article gives an overview of the currently available conservative, medical, endoscopic and surgical treatment methods for overweight and obesity in Germany and explains the indications. Against the background of the reorientation of obesity treatment as a part of the DMP and the forthcoming revisions of the guidelines, the previous indication should be discussed critically. The scientific findings of the last few years show that surgical treatment of obesity not only achieves the greatest weight loss in the long term, but also that obesity-associated diseases are then treated more effectively and overall mortality is reduced significantly more effectively than with conservative treatment.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Increased airway resistance can be related to the decrease in the functional capacity in obese women

Background and objective

Obesity can increase the airways resistance, mainly in the periphery, leading to dyspnea perception that can impair the functional capacity. This study aimed to analyze if airways resistance could be related to the walking capacity of women with morbid obesity.

Methods

Thirty-seven women with grade III obesity in preoperative bariatric surgery were evaluated using the spirometry test, impulse oscillometry system (IOS), and six-minute walk test (6MWT). Additionally, data about their daily dyspnea perception and physical activity level were collected.

Results

Variables of the spirometry test did not detect ventilator disorders. Compared to the predicted values, the IOS identified significant increase in airways resistance (kPa/L/s) (R5: 0.36 (0.34; 0.36) and 0.53 (0.47; 0.61); R20: 0.30 (0.28; 0.30) and 0.41 (0.35; 0.45); R5-20: 0.06 (0.06; 0.06) and 0.14 (0.10; 0.15); X5: -0.03 (-0.04; -0.01) and -0.20 (-0.27; -0.18), respectively). The distance walked in the 6MWT, 491.4±60.4m was significantly correlated to R5 (rho = -0.41, p = 0.01), R5-20 (rho = -0.52, p = 0.001), and X5 (rho = 0.54, p = 0.0006).

Conclusion

The IOS is able to identify changes in airway resistance even before the onset of symptoms. When evaluated by IOS women with severe obesity and normal spirometry exhibited central and peripheral airways obstruction. The correlations between the IOS and six-minute walk distance suggest that increased peripheral airways resistance could be related to worsening functional capacity.

Clinical Characteristics and Management Strategies for Adult Obese Asthma Patients

The rates of asthma and obesity are increasing concurrently in the United States. Epidemiologic studies demonstrate that the incidence of asthma increases with obesity. Furthermore, obese individuals have asthma that is more severe, harder to control, and resistant to standard medications. In fact, specific asthma-obesity phenotypes have been identified. Various pathophysiologic mechanisms, including mechanical, inflammatory, metabolic and microbiome-associated, are at play in promulgating the obese-asthma phenotypes. While standard asthma medications, such as inhaled corticosteroids and biologics, are currently used to treat obese asthmatics, they may have limited effectiveness. Targeting the underlying aberrant processes, such as addressing steroid resistance, microbiome, metabolic and weight loss approaches, may be helpful.

Clinical significance and applications of oscillometry

Recently, “Technical standards for respiratory oscillometry” was published, which reviewed the physiological basis of oscillometric measures and detailed the technical factors related to equipment and test performance, quality assurance and reporting of results. Here we present a review of the clinical significance and applications of oscillometry. We briefly review the physiological principles of oscillometry and the basics of oscillometry interpretation, and then describe what is currently known about oscillometry in its role as a sensitive measure of airway resistance, bronchodilator responsiveness and bronchial challenge testing, and response to medical therapy, particularly in asthma and COPD. The technique may have unique advantages in situations where spirometry and other lung function tests are not suitable, such as in infants, neuromuscular disease, sleep apnoea and critical care. Other potential applications include detection of bronchiolitis obliterans, vocal cord dysfunction and the effects of environmental exposures. However, despite great promise as a useful clinical tool, we identify a number of areas in which more evidence of clinical utility is needed before oscillometry becomes routinely used for diagnosing or monitoring respiratory disease.

This paper provides a current review of the interpretation, clinical significance and application of oscillometry in respiratory medicine, with special emphasis on limitations of evidence and suggestions for future research.https://bit.ly/3GQPViA

Evaluating Possible Mechanisms Linking Obesity to COVID-19: a Narrative Review

Currently, pneumonia caused by the coronavirus disease 2019 (COVID-19) is a pandemic. To date, there is no specific antiviral treatment for the disease, and universal access to the vaccine is a serious challenge. Some observational studies have shown that COVID-19 is more common in countries with a high prevalence of obesity and that people with COVID-19 have a higher body mass index. In these studies, obesity increased the risk of disease, as well as its severity and mortality. This study aimed to review the mechanisms that link obesity to COVID-19.

Respiratory impedance measured using impulse oscillometry in a healthy urban population

This study derives normative prediction equations for respiratory impedance in a healthy asymptomatic urban population using an impulse oscillation system (IOS). In addition, this study uses body mass index (BMI) in the equations to describe the effect of obesity on respiratory impedance.

Data from an urban population comprising 472 healthy asymptomatic subjects that resided or worked in lower Manhattan, New York City were retrospectively analysed. This population was the control group from a previously completed case–control study of the health effects of exposure to World Trade Center dust. Since all subjects underwent spirometry and oscillometry, these previously collected data allowed a unique opportunity to derive normative prediction equations for oscillometry in an urban, lifetime non-smoking, asymptomatic population without underlying respiratory disease.

Normative prediction equations for men and women were successfully developed for a broad range of respiratory oscillometry variables with narrow confidence bands. Models that used BMI as an independent predictor of oscillometry variables (in addition to age and height) demonstrated equivalent or better fit when compared with models that used weight. With increasing BMI, resistance and reactance increased compatible with lung and airway compression from mass loading.

This study represents the largest cohort of healthy urban subjects assessed with an IOS device. Normative prediction equations were derived that should facilitate application of IOS in the clinical setting. In addition, the data suggest that modelling of lung function may be best performed using height and BMI as independent variables rather than the traditional approach of using height and weight.

Prediction equations for respiratory impedance were derived in an urban cohort incorporating the effects of mass loading from obesity. Urban exposures had minimal effect on impedance allowing application of the equations to a broad range of populations.https://bit.ly/3a3zZvd

Oscillation Mechanics, Integer and Fractional Respiratory Modeling in COPD: Effect of Obstruction Severity

Purpose

This research examines the emerging role of respiratory oscillometry associated with integer (InOr) and fractional order (FrOr) respiratory models in the context of groups of patients with increasing severity. The contributions to our understanding of the respiratory abnormalities along the course of increasing COPD severity and the diagnostic use of this method were also evaluated.

Patients and Methods

Forty-five individuals with no history of smoking or pulmonary diseases (control group) and 141 individuals with diagnoses of COPD were studied, being classified into 45 mild, 42 moderate, 36 severe and 18 very severe cases.

Results

This study has shown initially that the course of increasing COPD severity was adequately described by the model parameters. This resulted in significant and consistent correlations among these parameters and spirometric indexes. Additionally, this evaluation enhanced our understanding of the respiratory abnormalities in different COPD stages. The diagnostic accuracy analyses provided evidence that hysteresivity, obtained from FrOr modeling, allowed a highly accurate identification in patients with mild changes [area under the receiver operator characteristic curve (AUC)= 0.902]. Similar analyses in groups of moderate and severe patients showed that peripheral resistance, derived from InOr modeling, provided the most accurate parameter (AUC=0.898 and 0.998, respectively), while in very severe patients, traditional, InOr and FrOr parameters were able to reach high diagnostic accuracy (AUC>0.9).

Conclusion

InOr and FrOr modeling improved our knowledge of the respiratory abnormalities along the course of increasing COPD severity. In addition, the present study provides evidence that these models may contribute in the diagnosis of COPD. Respiratory oscillometry exams require only tidal breathing and are easy to perform. Taken together, these practical considerations and the results of the present study suggest that respiratory oscillometry associated with InOr and FrOr models may help to improve lung function tests in COPD.

Obesity and the Lung: What We Know Today

Obesity is becoming more and more prevalent especially in Western industrial nations. The understanding of adipose tissue as an endocrine organ as well as the detection of adipocytokines - hormones that are secreted from the adipose tissue - gave reason to examine the interactions between adipose tissue and target organs. These efforts have been intensified especially in the context of bariatric surgery as promising weight loss therapy. Interactions between the lung and adipose tissue have rarely been investigated and are not well understood. There are obvious mechanical effects of obesity on lung function explaining the associations between obesity and lung diseases, in particular obesity hypoventilation syndrome, obstructive sleep apnea syndrome, asthma, and chronic obstructive pulmonary disease. The rise in the prevalence of obesity affects the epidemiology of pulmonary diseases as well. The aim of this review is to summarize the current knowledge on interactions, associations, and consequences of obesity and weight loss on lung function and lung diseases. Based on these data, areas for future research are identified.

Differential diagnosis of asthma and restrictive respiratory diseases by combining forced oscillation measurements, machine learning and neuro-fuzzy classifiers

To design machine learning classifiers to facilitate the clinical use and increase the accuracy of the forced oscillation technique (FOT) in the differential diagnosis of patients with asthma and restrictive respiratory diseases. FOT and spirometric exams were performed in 97 individuals, including controls (n = 20), asthmatic patients (n = 38), and restrictive (n = 39) patients. The first experiment of this study showed that the best FOT parameter was the resonance frequency, providing moderate accuracy (AUC = 0.87). In the second experiment, a neuro-fuzzy classifier and different supervised machine learning techniques were investigated, including k-nearest neighbors, random forests, AdaBoost with decision trees, and support vector machines with a radial basis kernel. All classifiers achieved high accuracy (AUC ≥ 0.9) in the differentiation between patient groups. In the third and fourth experiments, the use of different feature selection techniques allowed us to achieve high accuracy with only three FOT parameters. In addition, the neuro-fuzzy classifier also provided rules to explain the classification. Neuro-fuzzy and machine learning classifiers can aid in the differential diagnosis of patients with asthma and restrictive respiratory diseases. They can assist clinicians as a support system providing accurate diagnostic options.

Small Airway Disease Syndromes. Piercing the Quiet Zone

The role for direct assessment of small airway function in subjects with respiratory symptoms but normal airflow by spirometry is discussed. Small airway disease syndrome is described in numerous disease states using a multidisciplinary approach. Data demonstrate that small airway disease is related to presence of respiratory symptoms, exposure to inhaled toxins, presence of local and systemic inflammation, and presence of histologic abnormalities within the distal lung. Investigation of immunological derangements associated with distal airway dysfunction in the setting of normal spirometry may provide insight into pathophysiological mechanisms that are present at disease onset. For the purposes of this symposium, data were reviewed in selected clinical conditions (obesity, environmental inhalational injury, and cigarette smoking) that have been recently studied in the André Cournand Pulmonary Physiology Laboratory at Bellevue Hospital using the forced oscillation technique.

The Role of Airway Shunt Elastance on the Compartmentalization of Respiratory System Impedance

An inverse model consisting of two elastic compartments connected in series and served by two airway conduits has recently been fit to measurements of respiratory impedance in obese subjects. Increases in the resistance of the distal conduit of the model with increasing body mass index have been linked to peripheral airway compression by mass loading of the chest wall. Nevertheless, how the two compartments and conduits of this simple model map onto the vastly more complicated structure of an actual lung remain unclear. To investigate this issue, we developed a multiscale branching airway tree model of the respiratory system that predicts realistic input impedance spectra between 5 and 20 Hz with only four free parameters. We use this model to study how the finite elastances of the conducting airway tree and the proximal upper airways affect impedance between 5 and 20 Hz. We show that progressive constriction of the peripheral airways causes impedance to appear to arise from two compartments connected in series, with the proximal compartment being a reflection of the elastance of upper airway structures proximal to the tracheal entrance and the lower compartment reflecting the pulmonary airways and tissues. We thus conclude that while this simple inverse model allows evaluation of overall respiratory system impedance between 5 and 20 Hz in the presence of upper airway shunting, it does not allow the separate contributions of central versus peripheral pulmonary airways to be resolved.

Forced oscillation technique for early detection of the effects of smoking and COPD: contribution of fractional-order modeling

Purpose

The aim of the present study was to evaluate the performance of the forced oscillation technique (FOT) for the early diagnosis of the effects of smoking and COPD. The contributions of the integer-order (InOr) and fractional-order (FrOr) models were also evaluated.

Patients and methods

In total, 120 subjects were analyzed: 40 controls, 40 smokers (20.3±9.3 pack-years) and 40 patients with mild COPD.

Results

Initially, it was observed that traditional FOT parameters and the InOr and FrOr models provided a consistent description of the COPD pathophysiology. Mild COPD introduced significant increases in the FrOr inertance, damping factor and hysteresivity (P<0.0001). These parameters were significantly correlated with the spirometric parameters of central and small airway obstruction (P<0.0001). The diagnostic accuracy analyses indicated that FOT parameters and InOr modeling may adequately identify these changes (area under the receiver operating characteristic curve – AUC >0.8). The use of FrOr modeling significantly improved this process (P<0.05), allowing the early diagnosis of smokers and patients with mild COPD with high accuracy (AUC >0.9).

Conclusion

FrOr modeling improves our knowledge of modifications that occur in the early stages of COPD. Additionally, the findings of the present study provide evidence that these models may play an important role in the early diagnosis of COPD, which is crucial for improving the clinical management of the disease.

The effect of obesity on lung function

INTRODUCTION

There is a major epidemic of obesity, and many obese patients suffer with respiratory symptoms and disease. The overall impact of obesity on lung function is multifactorial, related to mechanical and inflammatory aspects of obesity. Areas covered: Obesity causes substantial changes to the mechanics of the lungs and chest wall, and these mechanical changes cause asthma and asthma-like symptoms such as dyspnea, wheeze, and airway hyperresponsiveness. Excess adiposity is also associated with increased production of inflammatory cytokines and immune cells that may also lead to disease. This article reviews the literature addressing the relationship between obesity and lung function, and studies addressing how the mechanical and inflammatory effects of obesity might lead to changes in lung mechanics and pulmonary function in obese adults and children. Expert commentary: Obesity has significant effects on respiratory function, which contribute significantly to the burden of respiratory disease. These mechanical effects are not readily quantified with conventional pulmonary function testing and measurement of body mass index. Changes in mediators produced by adipose tissue likely also contribute to altered lung function, though as of yet this is poorly understood.

Improvement in upright and supine lung mechanics with bariatric surgery affects bronchodilator responsiveness and sleep quality

Obesity and weight-loss have complex effects on respiratory physiology, but these have been insufficiently studied, particularly at early time points following weight-loss surgery and in the supine position. We evaluated 15 severely obese female participants before, and 5 weeks and 6 months after bariatric surgery using the Pittsburgh Sleep Quality Index (PSQI), spirometry, plethysmography, and oscillometry to measure respiratory system mechanics. Oscillometry and spirometry were conducted in the upright and supine position, and pre- and post-bronchodilation with 200µg of salbutamol. At 5 weeks post-surgery, weight-loss was 11.9±2.7kg with no effect on spirometric outcomes and a slight effect on oscillometric outcomes. However, at 6 months, weight-loss was 21.4±7.1kg with a 14.1±6.1% and 17.8±5.4% reduction in upright and supine Rrs,6, respectively. Ers also decreased by 25.7±9.4% and 20.2±7.2% in the upright and supine positions. No changes were observed in spirometry, but sleep quality improved from PSQI of 8.4±3.5 to 4.1±2.9. Bronchodilator responsiveness was low at baseline but increased significantly post-surgery, and this response was comparable to the improvement in Rrs produced by weight-loss. Modeling the impedance spectra with a two-compartment model demonstrated that improvements in lung mechanics with weight-loss begin in the upper or central compartment of the lungs and progress to include the peripheral compartment. Respiratory mechanics are impaired in the severely obese and is associated with poor sleep quality, but these improved substantially with weight-loss. Our data provide new evidence that severely obese individuals may have poor sleep quality due to abnormal respiratory mechanics that weight-loss improves.

Peak expiratory flow in obese subjects in different positions

Objective: To analyze the peak expiratory flow (PEF) in obese subjects in standing (ST), seated (SE), supine (SU), prone (PR), and right and left lateral decubitus (RL and LL) positions. Methods: 36 obese volunteers, aged between 18 and 54 years, and nonsmokers, were evaluated by anthropometric data; spirometry; international physical activity questionnaire (IPAQ); and PEF in ST, SE, SU, PR, RL, and LL positions, randomly. Results: The mean age was 27.3 ± 7.4 years and BMI of 38.7 ± 3.2 kg/m²; IPAQ results: active (50%), irregularly active (25%), very active (16.7%), and sedentary (08.3%); spirometry results: FVC = 100.33%, FEV₁ = 92.83%, FEV₁/FVC ratio = 0.95, FEF_25-75% = 85.55%. The PEF (L/min) were within the normal range and there was no difference between the ST and SE (428.6 ± 100.9 and 430.0 ± 100.1). Comparing ST and SE to the other positions, in absolute and percent of predicted values (L/min and %), there was a decrease in the SU (85.4 ± 14.9), PR (401.1 ± 92.4 and 84.1 ± 14.4), RL (398.6 ± 94.7 and 83.3 ± 14.9) (p < 0.05), and there was no difference to SU (409.4 ± 102.8) and LL (410.3 ± 93.9 and 85.8 ± 14.5). Conclusion: The PEF of healthy obese are similar in the standing and seated positions. The PEF decreases in the lying positions, except for the LL, that could be used as an alternative for measurements.

High-accuracy detection of airway obstruction in asthma using machine learning algorithms and forced oscillation measurements

BACKGROUND AND OBJECTIVES

The main pathologic feature of asthma is episodic airway obstruction. This is usually detected by spirometry and body plethysmography. These tests, however, require a high degree of collaboration and maximal effort on the part of the patient. There is agreement in the literature that there is a demand of research into new technologies to improve non-invasive testing of lung function. The purpose of this study was to develop automatic classifiers to simplify the clinical use and to increase the accuracy of the forced oscillation technique (FOT) in the diagnosis of airway obstruction in patients with asthma.

METHODS

The data consisted of FOT parameters obtained from 75 volunteers (39 with obstruction and 36 without). Different supervised machine learning (ML) techniques were investigated, including k-nearest neighbors (KNN), random forest (RF), AdaBoost with decision trees (ADAB) and feature-based dissimilarity space classifier (FDSC).

RESULTS

The first part of this study showed that the best FOT parameter was the resonance frequency (AUC = 0.81), which indicates moderate accuracy (0.70-0.90). In the second part of this study, the use of the cited ML techniques was investigated. All the classifiers improved the diagnostic accuracy. Notably, ADAB and KNN were very close to achieving high accuracy (AUC = 0.88 and 0.89, respectively). Experiments including the cross products of the FOT parameters showed that all the classifiers improved the diagnosis accuracy and KNN was able to reach a higher accuracy range (AUC = 0.91).

CONCLUSIONS

Machine learning classifiers can help in the diagnosis of airway obstruction in asthma patients, and they can assist clinicians in airway obstruction identification.

Early Diagnosis of Respiratory Abnormalities in Asbestos-Exposed Workers by the Forced Oscillation Technique

BACKGROUND

The current reference test for the detection of respiratory abnormalities in asbestos-exposed workers is spirometry. However, spirometry has several shortcomings that greatly affect the efficacy of current asbestos control programs. The forced oscillation technique (FOT) represents the current state-of-the-art technique in the assessment of lung function. This method provides a detailed analysis of respiratory resistance and reactance at different oscillatory frequencies during tidal breathing. Here, we evaluate the FOT as an alternative method to standard spirometry for the early detection and quantification of respiratory abnormalities in asbestos-exposed workers.

METHODOLOGY/PRINCIPAL FINDINGS

Seventy-two subjects were analyzed. The control group was composed of 33 subjects with a normal spirometric exam who had no history of smoking or pulmonary disease. Thirty-nine subjects exposed to asbestos were also studied, including 32 volunteers in radiological category 0/0 and 7 volunteers with radiological categories of 0/1 or 1/1. FOT data were interpreted using classical parameters as well as integer (InOr) and fractional-order (FrOr) modeling. The diagnostic accuracy was evaluated by investigating the area under the receiver operating characteristic curve (AUC). Exposed workers presented increased obstruction (resistance p<0.001) and a reduced compliance (p<0.001), with a predominance of obstructive changes. The FOT parameter changes were correlated with the standard pulmonary function analysis methods (R = -0.52, p<0.001). Early respiratory abnormalities were identified with a high diagnostic accuracy (AUC = 0.987) using parameters obtained from the FrOr modeling. This accuracy was significantly better than those obtained with classical (p<0.001) and InOr (p<0.001) model parameters.

CONCLUSIONS

The FOT improved our knowledge about the biomechanical abnormalities in workers exposed to asbestos. Additionally, a high diagnostic accuracy in the diagnosis of early respiratory abnormalities in asbestos-exposed workers was obtained. This makes the FOT particularly useful as a screening tool in the context of asbestos control and elimination. Moreover, it can facilitate epidemiological research and the longitudinal follow-up of asbestos exposure and asbestos-related diseases.