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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 effects related to work at high altitudes and acceleration force overload can generate physiological compensation mechanisms and eventual short-, medium- and long-term changes in lung function. Therefore, this study aimed to describe the chronic changes in lung function in combat pilots of the Brazilian Air Force. The sample consisted of 19 combat pilots and 20 controls. For pulmonary function measurements, we observed an increase in the mean values of Forced Vital Capacity (FVC) and Forced Expiratory Volume in the First Second (FEV1), a decrease in lung volume, an increase in resistance and work of breathing, in the exposed group compared to the control, with significant modifications to Residual Volume (RV) by Total Lung Capacity (TLC) in liters (L) and percentage (%). Similar behavior when evaluated according to flight hours, with an increase proportional to the increase in exposure time. Discrete changes, such as those observed in this research, may reflect adaptations of the respiratory system, bringing a complementary view to changes in chronic conditions.

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.

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.

IntroductionThe 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.MethodsOscillometric 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 discussionThe 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 p ConclusionsOscillometric principles combined with machine learning algorithms provide a new method for diagnosing respiratory changes in patients with systemic sclerosis. The present study's findings provide evidence that this combination may help in the early diagnosis of respiratory changes in these patients.

Background COVID-19 is characterized by a rapid change in the patient’s condition, with major changes occurring over a few days. We aimed to develop and evaluate an emergency system for monitoring patients with COVID-19, which may be useful in hospitals where more severe patients stay in their homes. Methodology/Principal findings The system consists of the home-based patient unit, which is set up around the patient and the hospital unit, which enables the medical staff to telemonitor the patient’s condition and help to send medical recommendations. The home unit allows the data transmission from the patient to the hospital, which is performed using a cell phone application. The hospital unit includes a virtual instrument developed in LabVIEW® environment that can provide a real-time monitoring of the oxygen saturation (SpO2), beats per minute (BPM), body temperature (BT), and peak expiratory flow (PEF). Abnormal events may be fast and automatically identified. After the design details are described, the system is validated by a 30-day home monitoring study in 12 controls and 12 patients with COVID-19 presenting asymptomatic to mild disease. Patients presented reduced SpO2 (p2 Conclusions An emergency system for home monitoring of patients with COVID-19 was developed in the current study. The proposed system allowed us to quickly respond to early abnormalities in these patients. This system may contribute to conserving hospital resources for those most in need while simultaneously enabling early recognition of patients under acute deterioration, requiring urgent assessment.

AimsThis study aimed to identify the symptoms associated with early stage SARS-CoV-2 (COVID-19) infections in healthcare professionals (HCP) using both clinical and laboratory data.MethodsA total of 1,297 patients, admitted between March 18 and April 8, 2020, were stratified according to their risk of developing COVID-19 using their responses to a questionnaire designed to evaluate symptoms and risk conditions.ResultsAnosmia/hyposmia (p ConclusionsThe significant clinical features for COVID-19 were identified as anosmia, fever, chills, and body pain. Elevated CRP, leukocytes under 5,400 x 109/L, and relative monocytosis (>9%) were common among patients with a confirmed COVID-19 diagnosis. These variables may help, in the absence of RT-PCR tests, to identify possible COVID-19 infections during pandemic outbreaks.SummaryFrom March 19 to April 8 2020, 1,297 patients attended the Polyclinic Piquet Carneiro for COVID-19 detection. Healthcare professional data was analyzed, significant clinical features were anosmia, fever, chills and body pain. Elevated CRP, leukopenia and monocytosis were common in COVID-19.

The burden associated with respiratory diseases is increasing and will likely grow exponentially in the next generations. Therefore a great research effort has been directed to the development of improved methods for diagnosis and management of respiratory diseases. Advances in clinical decision support systems based on machine learning (ML) algorithms have opened a new realm of methods in this area. These methods are closely related to personalized medicine, providing support to medical decisions, practices, interventions, and technologies that are tailored to individual patients on the basis of their predicted response or risk of disease. In particular, pattern analysis of pulmonary function has attracted attention as an approach to early detection of respiratory diseases. This article presents a review of the development of clinical decision support systems using in pulmonary function analysis from a machine learning perspective. Initially, a brief description of the main ML algorithms is presented, as well as the main methods used for pulmonary function exams. Then, we discuss the previous studies concerning the use of ML methods in pulmonary function analysis in a historical order, emphasizing the state of the art in this field. Methods using respiratory data beyond pulmonary function were also reviewed, as well as recent works integrating telemonitoring of pulmonary function and ML algorithms to optimize control of disease trajectory and prevent exacerbations. This review showed that ML has been successfully used in the automated interpretation of pulmonary function tests. In several studies, the introduction of ML methods increased diagnostic accuracy, including the early diagnosis. Very promising results were also observed concerning the prevention of exacerbations. Several of these studies, however, are small-scale studies, so large-scale studies are still needed to validate current findings and to boost its adoption by the medical community. Finally, we conclude and examine important future directions for this research field, including big data analytics, interactive machine learning, and deep learning.

Caroline Oliveira Ribeiro,1 Alvaro Camilo Dias Faria,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, Brazil 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 (P0.8). The use of FrOr modeling significantly improved this process (P0.9). 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. Keywords: COPD, oscillation mechanics, smoking, respiratory modeling, integer-order modeling, respiratory impedance

INTRODUCTION The forced oscillation technique (FOT) is a particularly useful test of the mechanical properties of the respiratory system that has an increasingly important role in lung function laboratories. There is general agreement in the literature that the determination of reference values is of utmost importance in the clinical use of the FOT. OBJECTIVE Our aim was to present reference values for whole-breath FOT measurements, establish which anthropometric variables were more predictive of impedance parameters, and provide all the details to adequately adopt these reference equations in individual laboratories. METHODS We prospectively evaluated a randomly selected non-smoking sample of the adult Brazilian population (288 subjects, 144 males and 144 females aged 20-86 years). The volunteers were separated by sex and divided into six groups based on decade of age. Sex-specific linear prediction equations were developed by multiple regression analysis using age, body mass and height as explanatory variables. RESULTS Age introduced a slight, but significant, reduction of resistance in men (P

Introduction The segmentation and skeletonisation of images via computed tomography (CT) airway lumen volumetry provide a new perspective regarding the incorporation of this technique in medical practice. Our aim was to quantify morphological changes in the large airways of patients with acromegaly through CT and, secondarily, to correlate these findings with hormone levels and pulmonary function testing (PFT) parameters. Methods This was a cross-sectional study in which 28 non-smoker patients with acromegaly and 15 control subjects underwent CT analysis of airway lumen volumetry with subsequent image segmentation and skeletonisation. Moreover, all participants were subjected to PFT. Results Compared with the controls, patients with acromegaly presented higher diameters in the trachea, right main bronchus and left main bronchus. The patients with acromegaly also showed a higher tracheal sinuosity index (the deviation of a line from the shortest path, calculated by dividing total length by shortest possible path) than the controls [1.06 (1.02–1.09) vs. 1.03 (1.02–1.04), P = 0.04], and tracheal stenosis was observed in 25% of these individuals. The tracheal area was correlated with the levels of growth hormone (rs = 0.45, P = 0.02) and insulin-like growth factor type I (rs = 0.38, P = 0.04). The ratio between the forced expiratory flow and forced inspiratory flow at 50% of the forced vital capacity was correlated with the tracheal area (rs = 0.36, P = 0.02) and Δ tracheal diameters (rs = 0.58, P

Introduction: Interstitial lung diseases (ILD) diagnosis requires a multidisciplinary workup, but sometimes it is impossible to achieve a confident diagnosis. Aim: To find predictive factors of mortality in patients with unclassifiable ILD (UILD). Methods: Retrospective analysis (Jan-2015 to Jan-2018) of patients diagnosed in our outpatient ILD clinic with UILD. Radiologic assessment was made by 2 independent radiologists and interobserver agreement was analysed. A cox regression analysis was performed. Results: From 379 patients, 37 (9.8%) were diagnosed with UILD. The most common reason of UILD was high surgical risk (21 patients, 55.3%). 14 patients (36.8%) died. The independent predictors of mortality were older age (HR 7.04 95% CI 1.05-47.31; p=0.045), lower FVC (HR 21.13, 95% CI 2.51-178.11; p=0.005) and LTOT (HR 11.24, 95% CI 1.89-66.81; p=0.008). Conclusions: UILD is a heterogeneous disease. Older age, lower FVC and LTOT seem to be independent predictors of mortality and interobserver agreement between radiologists ranged from good to very good.

The main objective of this study was to evaluate the performance of the Forced Oscillation Technique (FOT) and the extended RIC (eRIC) model in the analysis of respiratory mechanical alterations in individuals with work-related asthma (WRA). Twenty-nine individuals were evaluated: 17 healthy and 12 with WRA. Considering the resistive properties of the respiratory system, we observed increases in resistance of the peripheral airways (RpeRIC, p < 0.009) and a reduction in WRA homogeneity (p < 0.02). The use of a bronchodilator resulted in improvement of the total (R0, p < 0.05) and mean (Rm, p < 0.01) resistance. Regarding reactance, in the WRA group, the mean values were more negative (Xm, p < 0.03), while the resonance frequency increased (Fr, p < 0.0001), with decreases in dynamic compliance (C, p < 0.05, CeRIC, p < 0.01) and inertance (IeRIC, p < 0.02). We can conclude that FOT associated with the eRIC model may represent an alternative for longitudinal evaluation in WRA patients and can contribute to early disease identification.

Several respiratory diseases introduce increases in upper airway obstruction. This work describes the design and application of a system based on Tracheal Sounds Analysis (TSA) able to evaluate this obstruction. A miniature microphone was used, providing analog signals to a virtual instrument developed in LabVIEWTM environment. The design of the instrument is described, as well as in vitro and in vivo results obtained with orifice plates and patients with acromegaly, respectively. It was observed that the mean power (Pm) using orifice plates increased in comparison to that observed for free airflow, which is in agreement with the presence of turbulent airflow, associated with increased resistance. The comparative analysis of the Pm in controls and patients during spontaneous ventilation showed increased values in Pm (p < 0.009) and reduced values of the slope of the regression lines in the spectra (p < 0.006) in patients. These results are in agreement of the physiopathology of the studied disease, and provide clear evidence that TSA is able to detect the increased upper airway obstruction associated with acromegaly. Considering that TSA is performed during spontaneous breathing, requiring minimal patient effort, we concluded that the developed system could be a useful tool for the evaluation of changes in the airway obstruction introduced by acromegaly.

We evaluated the effect of exposition to asbestos in the complexity of the respiratory system investigating the airflow pattern sampling entropy (SamEnV′), recurrence period density entropy (RPDEV′) and variability (SDV′). A non-invasive and simple protocol for assessing respiratory mechanics during spontaneous breathing was used in a group of 30 controls and 29 asbestos-exposed patients. Exposition resulted in a significant reduction in the RPDEV′ (p < 0.001) and an increase in SDV′ (p < 0.001). These results suggest that the airflow pattern becomes less complex in exposed patients, which may explain the reduction in respiratory systems’ adaptability to daily life activities. The influence of smoking was also investigated in exposed patients, which resulted in a significant reduction in SamEnV′ (p < 0.03). This suggests a further abnormal effect in smokers. Diagnostic accuracy evaluations indicate that RPDEV′ and SDV′may contribute to the diagnosis of respiratory abnormalities in asbestos-exposed patients with accuracies of 76.9 and 78.8%, respectively. As measuring airflow pattern complexity during tidal breathing is simple method, requiring only the passive cooperation, this technique may constitute a significant clinical contribution by providing novel respiratory biomarkers to facilitate the diagnosis of respiratory abnormalities these patients.

The aim of this study was to investigate the potential of the forced oscillation technique (FOT) in the differential diagnosis of patients with obstructive and restrictive respiratory diseases. A total of 76 individuals was analysed, including moderate obstructive (MO; n = 18), severe obstructive (SO; n = 20), moderate restrictive (MR; n = 18) and severe restrictive (SR; n = 20) patients. The observed changes were consistent with previously published results and the physiological foundations involved. Analyses using receiver operator characteristic curves showed that resistance values provided adequate differentiation between patient groups with more advanced diseases (SO-MR and SO-SR), with diagnostic accuracy ≥0.80. The highest accuracy was offered by the respiratory system resonance frequency, which discriminated between the obstructive and restrictive groups accurately (≥0.84). Given the ease of performing the test, we can assume that the proposed methodology will provide a significant contribution to the differential diagnosis of obstructive and restrictive respiratory diseases.

The aim of the present study was to evaluate the forced oscillation technique (FOT) associated with fractional-order models in the early diagnosis of the effects of smoking and in patients with early-stage chronic obstructive pulmonary disease (COPD). A total of 79 subjects was analysed: 31 controls, 26 who smoked and 22 with mild COPD. COPD caused significant increases in the inertance (L) and damping factor (p < 0.001) and the hysteresivity (p < 0.001). L presented high diagnostic accuracy in the identification of the effects of smoking (99.5%) and COPD (99.9%). This model contributed to improving our knowledge about the modifications that occur in the early stage of COPD. Additionally, parameters obtained from this model present great potential for early diagnosis in smokers and in patients with early-stage COPD.

Objective: To describe and quantify the main changes seen on computed tomography of the chest in mildly symptomatic adult patients with sickle cell disease, as well as to evaluate the radiologist accuracy in determining the type of hemoglobinopathy. Materials and Methods: A prospective study involving 44 adult patients with sickle cell disease who underwent inspiration and expiration computed tomography of the chest. The frequency of tomography findings and the extent of involvement are reported. We also calculated radiologist accuracy in determining the type of hemoglobinopathy by analyzing the pulmonary alterations and morphology of the spleen. Results: The changes found on computed tomography scans, in descending order of frequency, were as follows: fibrotic opacities (81.8%); mosaic attenuation (56.8%); architectural distortion (31.8%); cardiomegaly (25.0%); lobar volume reduction (18.2%); and increased caliber of peripheral pulmonary arteries (9.1%). For most of the findings, the involvement was considered mild, five or fewer lung segments being affected. The accuracy in determining the type of hemoglobinopathy (HbSS group versus not HbSS group) was 72.7%. Conclusion: In adult patients with sickle cell disease, the main tomography findings reflect fibrotic changes. In addition, computed tomography can be helpful in differentiating among hemoglobinopathies. Resumo Objetivo: Descrever e quantificar as principais alterações na tomografia computadorizada do tórax em pacientes adultos oligossintomáticos com doença falciforme e, secundariamente, avaliar o índice de acerto do radiologista quanto ao tipo de hemoglobinopatia. Materiais e Métodos: Estudo prospectivo em que 44 pacientes adultos com doença falciforme foram submetidos a tomografia computadorizada do tórax tanto em inspiração como em expiração. Foram descritos a frequência dos achados tomográficos e os graus de acometimento. Por meio da análise das alterações pulmonares e do padrão morfológico do baço, foi calculado o índice de acerto do radiologista quanto ao tipo de hemoglobinopatia. Resultados: As alterações encontradas nos exames de tomografia computadorizada, em ordem decrescente de frequência, foram: opacidades reticulares (81,8%), padrão de atenuação em mosaico (56,8%), distorção arquitetural (31,8%), cardiomegalia (25%), redução volumétrica lobar (18,2%) e aumento do calibre de ramos periféricos das artérias pulmonares (9,1%). Na maioria dos achados o grau de acometimento foi considerado leve, com até cinco segmentos pulmonares acometidos. O índice de acerto quanto ao tipo de hemoglobinopatia (grupo HbSS versus grupo não HbSS) foi 72,7%. Conclusão: Em pacientes adultos com doença falciforme os principais achados tomográficos refletem alterações fibróticas. Além do mais, a tomografia computadorizada pode ser útil na diferenciação do tipo de hemoglobinopatia.

Our aim was to evaluate the use of fractional-order (FrOr) modeling in asthma.We compared FrOr models with traditional parameters and an integer-order model FrOr parameters best fit the data, showing good associations with spirometry.They also showed a high accuracy in the detection of the mild obstruction in asthma FrOr models provide meaningful information in asthmatic patients. The purpose of this study was to evaluate the use of fractional-order (FrOr) modeling in asthma. To this end, three FrOr models were compared with traditional parameters and an integer-order model (InOr). We investigated which model would best fit the data, the correlation with traditional lung function tests and the contribution to the diagnostic of airway obstruction. The data consisted of forced oscillation (FO) measurements obtained from healthy (n=22) and asthmatic volunteers with mild (n=22), moderate (n=19) and severe (n=19) obstructions. The first part of this study showed that a FrOr was the model that best fit the data (relative distance: FrOr=4.3?2.4; InOr=5.1?2.6%). The correlation analysis resulted in reasonable (R=0.36) to very good (R=0.77) associations between FrOr parameters and spirometry. The closest associations were observed between parameters related to peripheral airway obstruction, showing a clear relationship between the FrOr models and lung mechanics. Receiver-operator analysis showed that FrOr parameters presented a high potential to contribute to the detection of the mild obstruction in a clinical setting. The accuracy area under the Receiver Operating Characteristic curve (AUC) observed in these parameters (AUC=0.954) was higher than that observed in traditional FO parameters (AUC=0.732) and that obtained from the InOr model (AUC=0.861). Patients with moderate and severe obstruction were identified with high accuracy (AUC=0.972 and 0.977, respectively). In conclusion, the results obtained are in close agreement with asthma pathology, and provide evidence that FO measurement associated with FrOr models is a non-invasive, simple and radiation-free method for the detection of biomechanical abnormalities in asthma.

Breathing is a complex rhythmic motor act, which is created by integrating different inputs to the respiratory centres. Analysing nonlinear fluctuations in breathing may provide clinically relevant information in patients with complex illnesses, such as asbestosis. We evaluated the effect of exposition to asbestos on the complexity of the respiratory system by investigating the respiratory impedance sample entropy (SampEnZrs) and recurrence period density entropy (RPDEnZrs). Similar analyses were performed by evaluating the airflow pattern sample entropy (SampEnV&rsquo, ) and recurrence period density entropy (RPDEnV&rsquo, ). Groups of 34 controls and 34 asbestos-exposed patients were evaluated in the respiratory impedance entropy analysis, while groups of 34 controls and 30 asbestos-exposed patients were investigated in the analysis of airflow entropy. Asbestos exposition introduced a significant reduction of RPDEnV&rsquo, in non-smoker patients (p &lt, 0.0004), which suggests that the airflow pattern becomes less complex in these patients. Smoker patients also presented a reduction in RPDEnV&rsquo, (p &lt, 0.05). These finding are consistent with the reduction in respiratory system adaptability to daily life activities observed in these patients. It was observed a significant reduction in SampEnV&rsquo, in smoker patients in comparison with non-smokers (p &lt, 0.02). Diagnostic accuracy evaluations in the whole group of patients (including non-smokers and smokers) indicated that RPDEnV&rsquo, might be useful in the diagnosis of respiratory abnormalities in asbestos-exposed patients, showing an accuracy of 72.0%. In specific groups of non-smokers, RPDEnV&rsquo, also presented adequate accuracy (79.0%), while in smoker patients, SampEnV&rsquo, and RPDEnV&rsquo, presented adequate accuracy (70.7% and 70.2%, respectively). Taken together, these results suggest that entropy analysis may provide an early and sensitive functional indicator of interstitial asbestosis.

Background and objective Integer and fractional-order models have emerged as powerful methods for obtaining information regarding the anatomical or pathophysiological changes that occur during respiratory diseases. However, the precise interpretation of the model parameters in light of the lung structural changes is not known. This study analyzed the associations of the integer and fractional-order models with structural changes obtained using multidetector computed tomography densitometry (MDCT) and pulmonary function analysis. Methods Integer and fractional-order models were adjusted to data obtained using the forced oscillation technique (FOT). The results obtained in controls (n = 20) were compared with those obtained in patients with silicosis (n = 32), who were submitted to spirometry, body plethysmograph, FOT, diffusing capacity of the lungs for carbon monoxide (DLCO), and MDCT. The diagnostic accuracy was also investigated using ROC analysis. Results The observed changes in the integer and fractional-order models were consistent with the pathophysiology of silicosis. The integer-order model showed association only between inertance and the non-aerated compartment (R = −0.69). This parameter also presented the highest associations with spirometry (R = 0.81), plethysmography (−0.61) and pulmonary diffusion (R = 0.53). Considering the fractional-order model, the increase in the poorly aerated and non-aerated regions presented direct correlations with the fractional inertance (R = 0.48), respiratory damping (R = 0.37) and hysteresivity (R = 0.54) and inverse associations with its fractional exponent (R = −0.62) and elastance (−0.35). Significant associations were also observed with spirometry (R = 0.63), plethysmography (0.37) and pulmonary diffusion (R = 0.51). Receiver operator characteristic analysis showed a higher accuracy in the FrOr model (0.908) than the eRIC model (0.789). Conclusions Our study has shown clear associations of the integer and fractional-order parameters with anatomical changes obtained via MDCT and pulmonary function measurements. These findings help to elucidate the physiological interpretation of the integer and fractional-order parameters and provide evidence that these parameters are reflective of the abnormal changes in silicosis. We also observed that the fractional-order model showed smaller curve-fitting errors, which resulted in a higher diagnostic accuracy than that of the eRIC model. Taken together, these results provide strong motivation for further studies exploring the clinical and scientific use of these models in respiratory medicine.

BACKGROUND: With increased survival rates and the consequent emergence of an adult population with cystic fibrosis (CF), developing novel tools for periodic evaluations of these patients has become a new challenge. Thus, we sought to determine the contribution of lung-volume quantification using multidetector computed tomography (CT) in adults with CF and to investigate the association between structural changes and functional abnormalities. METHODS: This was a cross-sectional study in which 21 adults with CF and 22 control subjects underwent lung-volume quantification using multidetector CT. Voxel densities were divided into 4 bands: −1,000 to −900 Hounsfield units (HU) (hyperaerated region), −900 to −500 HU (normally aerated region), −500 to −100 HU (poorly aerated region), and −100 to 100 HU (non-aerated region). In addition, all participants performed pulmonary function tests including spirometry, body plethysmography, diffusion capacity for carbon monoxide, and the forced oscillation technique. RESULTS: Adults with CF had more non-aerated regions and poorly aerated regions with lung-volume quantification using multidetector CT than controls. Despite these abnormalities, total lung volume measured by lung-volume quantification using multidetector CT did not differ between subjects and controls. Total lung capacity (TLC) measured by body plethysmography correlated with both total lung volume (rs = 0.71, P CONCLUSIONS: In adults with CF, lung-volume quantification using multidetector CT can destimate the lung volumes of compartments with different densities and determine the aerated and non-aerated contents of the lungs; furthermore, lung-volume quantification using multidetector CT is clearly related to pulmonary function parameters.

Background The improvement in sickle cell anemia (SCA) care resulted in the emergence of a large population of adults living with this disease. The mechanisms of lung injury in this new population are largely unknown. The forced oscillation technique (FOT) represents the current state-of-the-art in the assessment of lung function. The present work uses the FOT to improve our knowledge about the respiratory abnormalities in SCA, evaluates the associations of FOT with the functional exercise capacity and investigates the early detection of respiratory abnormalities. Methodology/Principal findings Spirometric classification of restrictive abnormalities resulted in three categories: controls (n = 23), patients with a normal exam (n = 21) and presenting pulmonary restriction (n = 24). FOT analysis showed that, besides restrictive changes (reduced compliance; p

We investigated the influence of airway obstruction in the complexity of the airflow pattern in COPD and its use as a marker of disease activity. The sample entropy (SampEnV') and the variability (SDV') of the airflow pattern were measured in a group of 88 subjects with various levels of airway obstruction. Airway obstruction resulted in a reduction in the SampEnV' (p0.0001) that was significantly correlated with spirometric indices of airway obstruction (R=0.50, p0.001). The early adverse effects in mild airway obstruction were detected by the SampEnV' with an accuracy of 84%. SDV' increased with airway obstruction (p0.002). We conclude that (1) the airflow patterns in COPD exhibit reduced complexity compared with healthy subjects; (2) this reduction in complexity is proportional to airway obstruction; and (3) the evaluation of SampEnV' may provide novel respiratory biomarkers suitable to facilitate the diagnosis of respiratory abnormalities in COPD.

Background: Recent studies suggested that the bronchodilator response depends on airway obstruction. The forced oscillation technique (FOT) may help improve our understanding of the changes in respiratory mechanics that occur after the application of a bronchodilator. Objectives: We aimed to (1) assess the response to salbutamol and to compare the impedance changes in healthy individuals and COPD patients, (2) investigate the effects of airway obstruction on this response and (3) evaluate the utility of the FOT as a complementary measurement to assess the response to the bronchodilator. Methods: Twenty-five healthy individuals and 82 patients with COPD were assessed with the FOT followed by spirometry before and after the use of salbutamol. Results: The changes exhibited by the COPD subgroups were greater than in the healthy individuals (p < 0.05). Increased obstruction resulted in decreased reductions in mean resistance and increased improvements in mean reactance (p < 0.001). In addition, the bronchodilation reduced the ventilation heterogeneity and the impedance modulus in all COPD stages (p < 0.05). The correlation coefficients for the spirometric and FOT changes were low (0.21-0.38). Conclusions: In the initial phases of COPD (stage I), the effects of bronchodilation are greater than in healthy volunteers. The bronchodilator use improved the oscillatory mechanics in all of the studied groups of COPD patients. These improvements are reduced in more advanced phases of airway obstruction (II, III and IV). The FOT provides information that complements the data supplied by spirometry, contributing to an improvement in the evaluation of the bronchodilator response in COPD.

The purpose of this study was to develop an automatic classifier to increase the accuracy of the forced oscillation technique (FOT) for diagnosing early respiratory abnormalities in smoking patients. The data consisted of FOT parameters obtained from 56 volunteers, 28 healthy and 28 smokers with low tobacco consumption. Many supervised learning techniques were investigated, including logistic linear classifiers, k nearest neighbor (KNN), neural networks and support vector machines (SVM). To evaluate performance, the ROC curve of the most accurate parameter was established as baseline. To determine the best input features and classifier parameters, we used genetic algorithms and a 10-fold cross-validation using the average area under the ROC curve (AUC). In the first experiment, the original FOT parameters were used as input. We observed a significant improvement in accuracy (KNN=0.89 and SVM=0.87) compared with the baseline (0.77). The second experiment performed a feature selection on the original FOT parameters. This selection did not cause any significant improvement in accuracy, but it was useful in identifying more adequate FOT parameters. In the third experiment, we performed a feature selection on the cross products of the FOT parameters. This selection resulted in a further increase in AUC (KNN=SVM=0.91), which allows for high diagnostic accuracy. In conclusion, machine learning classifiers can help identify early smoking-induced respiratory alterations. The use of FOT cross products and the search for the best features and classifier parameters can markedly improve the performance of machine learning classifiers.

Our aim 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 asthma.We used different techniques, including k-nearest neighbour (KNN), random forest (RF), AdaBoost with decision trees (ADAB) and feature-based dissimilarity space classifier (FDSC).Our findings revealed that all classifiers improved the diagnostic accuracy; ADAB and KNN were very close to achieving high accuracy.The best performance was observed using the cross products of the FOT parameters associated with KNN, which was able to reach a high diagnostic accuracy.Our study and findings will contribute to assist clinicians in airway obstruction identification and guiding therapy in asthma. Background and ObjectivesThe 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. MethodsThe 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). ResultsThe first part of this study showed that the best FOT parameter was the resonance frequency (AUC=0.81), which indicates moderate accuracy (0.700.90). 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). ConclusionsMachine learning classifiers can help in the diagnosis of airway obstruction in asthma patients, and they can assist clinicians in airway obstruction identification.

The purpose of this study is to develop a clinical decision support system based on machine learning (ML) algorithms to help the diagnostic of chronic obstructive pulmonary disease (COPD) using forced oscillation (FO) measurements. To this end, the performances of classification algorithms based on Linear Bayes Normal Classifier, K nearest neighbor (KNN), decision trees, artificial neural networks (ANN) and support vector machines (SVM) were compared in order to the search for the best classifier. Four feature selection methods were also used in order to identify a reduced set of the most relevant parameters. The available dataset consists of 7 possible input features (FO parameters) of 150 measurements made in 50 volunteers (COPD, n=25; healthy, n=25). The performance of the classifiers and reduced data sets were evaluated by the determination of sensitivity (Se), specificity (Sp) and area under the ROC curve (AUC). Among the studied classifiers, KNN, SVM and ANN classifiers were the most adequate, reaching values that allow a very accurate clinical diagnosis (Se>87%, Sp>94%, and AUC>0.95). The use of the analysis of correlation as a ranking index of the FOT parameters, allowed us to simplify the analysis of the FOT parameters, while still maintaining a high degree of accuracy. In conclusion, the results of this study indicate that the proposed classifiers may contribute to easy the diagnostic of COPD by using forced oscillation measurements.

OBJECTIVES: Pulmonary involvement in rheumatoid arthritis is directly responsible for 10% to 20% of all mortality. The best way to improve the prognosis is early detection and treatment. The forced oscillation technique is easy to perform and offers a detailed exam, which may be helpful in the early detection of respiratory changes. This study was undertaken to (1) evaluate the clinical potential of the forced oscillation technique in the detection of early respiratory alterations in rheumatoid arthritis patients with respiratory complaints and (2) to compare the sensitivity of forced oscillation technique and spirometric parameters. METHODS: A total of 40 individuals were analyzed: 20 healthy and 20 with rheumatoid arthritis (90% with respiratory complaints). The clinical usefulness of the parameters was evaluated by investigating the sensibility, the specificity and the area under the receiver operating characteristic curve. ClinicalTrials.gov: NCT01641705. RESULTS: The early adverse respiratory effects of rheumatoid arthritis were adequately detected by the forced oscillation technique parameters, and a high accuracy for clinical use was obtained (AUC.0.9, Se = 80%, Sp = 95%). The use of spirometric parameters did not obtain an appropriate accuracy for clinical use. The diagnostic performance of the forced oscillation technique parameters was significantly higher than that of spirometry. CONCLUSIONS: The results of the present study provide substantial evidence that the forced oscillation technique can contribute to the easy identification of initial respiratory abnormalities in rheumatoid arthritis patients that are not detectable by spirometric exams. Therefore, we believe that the forced oscillation technique can be used as a complementary exam that may help to improve the treatment of breathing disorders in rheumatoid arthritis patients.

OBJECTIVE: To set out a severity classification for idiopathic pulmonary fibrosis (IPF) based on the interaction of pulmonary function parameters with high resolution computed tomography (CT) findings. INTRODUCTION: Despite the contribution of functional and radiological methods in the study of IPF, there are few classification proposals for the disease based on these examinations. METHODS: A cross-sectional study was carried out, in which 41 non-smoking patients with IPF were evaluated. The following high resolution CT findings were quantified using a semi-quantitative scoring system: reticular abnormality, honeycombing and ground-glass opacity. The functional variables were measured by spirometry, forced oscillation technique, helium dilution method, as well as the single-breath method of diffusing capacity of carbon monoxide. With the interaction between functional indexes and high resolution CT scores through fuzzy logic, a classification for IPF has been built. RESULTS: Out of 41 patients studied, 26 were male and 15 female, with a mean age of 70.8 years. Volume measurements were the variables which showed the best interaction with the disease extension on high resolution CT, while the forced vital capacity showed the lowest estimative errors in comparison to total lung capacity. A classification for IPF was suggested based on the 95% confidence interval of the forced vital capacity %: mild group (>92.7); moderately mild (76.9-92.6); moderate (64.3-76.8%); moderately severe (47.1-64.2); severe (24.3-47.0); and very severe (

One of the most common occurrences in patients with rheumatoid arthritis (RA) is the presence of problems in the knee joint. The methods used in the diagnosis of this damage, however, are expensive and/or invasive. This work describes the design and application of a system able to non-invasively evaluate changes in knee joint using accelerometry. Three accelerometers mounted perpendicularly were used, providing signals to a portable instrument. In vivo tests investigating the knee joint vibration power between 2 and 10 Hz showed increased values in RA patients (p

Several respiratory diseases, as well as surgical procedures, may introduce changes in the thoracoabdominal movement. Non-intrusive techniques have the potential to simplify the exam of these patients. This work describes the design of a noncontact system able to evaluate changes in the thoracic and abdominal movement. Two ultrasonic transducers were used, providing analogue signals to a virtual instrument. In vitro evaluations using a flat surface in motion showed small errors in the evaluation of the asynchrony (Δ=6.8O), and the relative contributions of the abdominal (CRAb) and thoracic (CRTx) compartments (CRAb=1.3%; CRTx=-1.3%). In vivo tests in normal subjects simulating abnormal conditions resulted in higher values of asynchrony (p

INTRODUCTION: Detection of smoking effects is of utmost importance in the prevention of cigarette‐induced chronic airway obstruction. The forced oscillation technique offers a simple and detailed approach to investigate the mechanical properties of the respiratory system. However, there have been no data concerning the use of the forced oscillation technique to evaluate respiratory mechanics in groups with different degrees of tobacco consumption. OBJECTIVES: (1) to evaluate the ability of the forced oscillation technique to detect smoking‐induced respiratory alterations, with special emphasis on early alterations; and (2) to compare the diagnostic accuracy of the forced oscillation technique and spirometric parameters. METHODS: One hundred and seventy subjects were divided into five groups according to the number of pack–years smoked: four groups of smokers classified as 60 pack–years and a control group. The four groups of smokers were compared with the control group using receiver operating characteristic (ROC) curves. RESULTS: The early adverse effects of smoking in the group with 60 pack–years, the diagnostic performance of the forced oscillation technique was similar to that observed with spirometry. CONCLUSIONS: This study revealed that forced oscillation technique parameters were able to detect early smoking‐induced respiratory involvement when pathologic changes are still potentially reversible. These findings support the use of the forced oscillation technique as a versatile clinical diagnostic tool in helping with chronic obstructive lung disease prevention, diagnosis, and treatment.

OBJETIVO: Investigar os efeitos da obstrução de vias aéreas nas variações das propriedades resistivas e elásticas do sistema respiratório de asmáticos adultos mediadas pelo uso de salbutamol. MÉTODOS: Foram analisados 24 indivíduos controles e 69 asmáticos, todos não tabagistas, divididos em três grupos segundo o nível de obstrução de vias aéreas (leve, moderada e acentuada). Cada grupo foi dividido em dois subgrupos de acordo com a resposta broncodilatadora: resposta broncodilatadora positiva (RB+) ou negativa (RB-). A espirometria foi utilizada para a avaliação da obstrução, e a técnica de oscilações forçadas, para a análise das propriedades resistivas e elásticas, sendo realizadas antes e após a utilização de 300 µg de salbutamol. RESULTADOS: A resistência no intercepto (R0) apresentou maior redução nos grupos com maior obstrução. Essa redução foi mais evidente nos subgrupos RB+ do que nos RB- (p < 0,02 e p < 0,03, respectivamente). Houve diferença significativa entre o grupo controle e a o subgrupo com obstrução acentuada RB+ (p < 0,002). As reduções na elastância dinâmica (Edyn) se acentuaram significativamente com a obstrução, tanto para os subgrupos RB- (p < 0,03), quanto para os RB+ (p < 0,003). As reduções da Edyn foram significativamente maiores nos subgrupos com obstrução moderada RB- (p < 0,008) e com obstrução acentuada RB+ (p < 0,0005) do que no grupo controle. CONCLUSÕES: Em asmáticos, o aumento da obstrução de vias aéreas resulta na elevação das variações em R0 e Edyn com o uso de salbutamol. Pacientes com RB+ apresentam variações mais elevadas que indivíduos com RB-. OBJECTIVE: To investigate the effects of airway obstruction on albuterol-mediated variations in the resistive and elastic properties of the respiratory system of adult patients with asthma. METHODS: This study comprised 24 healthy controls and 69 patients with asthma, all of whom were nonsmokers. The patients were divided into three groups according to the severity of airway obstruction (mild, moderate or severe). Each of the three groups was divided into two subgroups according to the bronchodilator response (BR): positive (BR+) or negative (BR-). Airway obstruction was determined by means of spirometry, and the resistive and elastic properties were determined by means of the forced oscillation technique. These measurements were conducted before and after albuterol use (300 µg). RESULTS: The resistance at the intercept (R0) presented greater reductions in the groups with higher obstruction. This reduction was more evident in the BR+ subgroups than in the BR- subgroups (p < 0.02 and p < 0.03, respectively). There was a significant difference between the control group and the BR+ subgroup with severe obstruction (p < 0.002). The reductions in dynamic elastance (Edyn) were significantly greater in proportion to the degree of obstruction, in the BR- subgroups (p < 0.03), and in the BR+ subgroups (p < 0.003). The reductions in Edyn were significantly greater in the BR- subgroup with moderate obstruction (p < 0.008) and in the BR+ subgroup with severe obstruction (p < 0.0005) than in the control group. CONCLUSIONS: In patients with asthma, increased airway obstruction results in greater reductions in R0 and Edyn after albuterol use. These reductions are greater among BR+ patients than among BR- patients.

Background: The forced oscillation technique (FOT) is a promising method for providing a detailed analysis of respiratory mechanics during spontaneous breathing. There is limited data about the use of FOT in patients with sarcoidosis. Objectives: The aims of this study were to test the ability of FOT to describe the changes in respiratory mechanics in sarcoidosis and to evaluate the clinical potential of FOT. Methods: Twenty healthy subjects and 31 patients were studied. All subjects performed spirometric exams, and pulmonary volumes were measured in patients. Resistive data were interpreted using the zero-intercept resistance (R0), the slope of the resistive component of the impedance (S), and the mean resistance (Rm). The analysis of reactance was used to measure the mean reactance (Xm) and the respiratory system dynamic compliance (Cdyn). The total mechanical load was evaluated using the absolute value of the respiratory impedance (Z4Hz). Results: In close agreement with pathophysiological fundamentals, significant (p < 0.001) increases in R0, Rm, and Z4Hz, and reductions in Cdyn (p < 0.003) were observed. S and Xm presented smaller modifications (p < 0.02). All FOT parameters were significantly correlated with spirometric indices. Z4Hz was the most adequate parameter for clinical use (Se = 75%, Sp = 75%), followed by R0 and Rm. Conclusions:FOT parameters were consistent with the pathophysiology of sarcoidosis and were also able to detect the effects of this disease. Because the FOT is easy to perform, such a technique may represent an alternative and/or a complement to other conventional exams to help the clinical evaluations of sarcoidotic patients.

Physiological studies of swallowing and the diagnosis and treatment of dysphagia are crucially dependent of detailed information of respiratory and feeding events. However, this information has been obtained by indirect and/or expensive methods, as well as by methods demanding exposure to radiation. In this context, the purpose of this study was twofold: (1) describe a new low-cost system for the analysis of the respiratory events during swallowing using the Forced Oscillation Technique and (2) evaluate the performance of this device in the description of physiological events during water swallowing. The device consists of a personal computer adapted to measurement modules able to characterize the soft palate movement, the elevation of the larynx, the duration of deglutition apnoea, and the direction of airflow at the end of the swallow apnoea. These parameters were studied in eight healthy subjects under conditions of saliva swallowing and three doses of water (5,10 and 20 mL). The system allowed a real time description of the respiratory and feeding events, which were in close agreement with physiological principles. Mean results showed an increase of the apnoea time that was not statistically significant. In contrast, a highly significant increase of respiratory impedance during swallowing was observed (p < 0.0001). The described instrument does not use radiation. It shows itself particularly well suited for studies of deglutition physiology, including mechanisms involved in airway protection during swallowing. It can also be potentially useful contributing to easy clinical bedside evaluations and biofeedback procedures for the rehabilitation of paediatric and elderly patients.

Sickle cell anemia (SCA) is characterized by a broad spectrum of abnormalities that affect most body organs and systems. To date, there is few data on the influence of these patients' clinical characteristics on the functional exercise capacity.To investigate the effect of the clinical complications on the functional exercise capacity of adult SCA patients.Cross-sectional study, where 45 SCA patients underwent clinical evaluations, echocardiography, pulmonary function testing, and determination of six-minute walking distance (6MWD).A significant correlation (P 0.001) was found between 6MWD and hemoglobin (Hb) level, tricuspid regurgitation velocity, forced vital capacity, acute chest syndrome, and diffusing capacity for carbon monoxide. The prediction model for 6MWD explained 67% of the 6MWD variability (P 0.001).Hemodynamics, cardiovascular function, pulmonary function, and episodes of acute lung injury seem to impact the 6MWD in adults with SCA.

Introduction Although impaired pulmonary function and respiratory sleep disorders are described as responsible for increased mortality in acromegalic patients, little is known about the tracheal abnormalities in this group of patients. Thus, the objectives of this study were to describe the tracheal structural abnormalities and correlate these changes with the respiratory function and clinical data of acromegalic patients. Material and methods This is a cross-sectional study that was carried out at two university hospitals. Twenty acromegalic patients underwent spirometry, forced oscillation technique, and computed tomography (CT) assessments. Dyspnea and daytime sleepiness were assessed using the Modified Medical Research Council (MMRC) scale and the Epworth Sleepiness Scale (ESS), respectively. Forty matched subjects served as controls. Results The acromegalic patients exhibited larger median ratios between forced expiratory flow and forced inspiratory flow at 50% of the forced vital capacity (FEF50%/FIF50%) (2.05 vs. 1.06, p = 0.0001) compared with healthy volunteers. In the CT analysis, acromegalic patients exhibited larger median differences between their cervical and thoracic tracheal diameters (Δ tracheal diameters) (3 vs. 1 mm; p = 0.003). An association was found between FEF50%/FIF50% and the following variables: mean resistance (Rm), cervical tracheal diameter, and Δ tracheal diameters. Rm also exhibited a negative correlation with cervical tracheal diameter. Neither the MMRC scale nor the ESS exhibited any significant correlation with large airway obstruction (LAO) indices or with the measured tracheal diameters. Conclusions Acromegalic patients have tracheal structural abnormalities which are associated with functional indicators of LAO but not with clinical data.

Background The Forced Oscillation Technique (FOT) has the potential to increase our knowledge about the biomechanical changes that occur in Cystic Fibrosis (CF). Thus, the aims of this study were to investigate changes in the resistive and reactive properties of the respiratory systems of adults with CF. Methods The study was conducted in a group of 27 adults with CF over 18 years old and a control group of 23 healthy individuals, both of which were assessed by the FOT, plethysmography and spirometry. An equivalent electrical circuit model was also used to quantify biomechanical changes and to gain physiological insight. Results and discussion The CF adults presented an increased total respiratory resistance (p

OBJETIVO: Analisar, através da técnica de oscilações forçadas, pacientes asmáticos com resposta broncodilatadora positiva pelo laudo espirométrico e comparar esses resultados com os obtidos em indivíduos sadios. MÉTODOS: Foram analisados 53 indivíduos não tabagistas, sendo 24 sadios sem história de doença pulmonar e 29 asmáticos com resposta broncodilatadora positiva segundo o laudo espirométrico. Todos foram submetidos à técnica de oscilações forçadas e a espirometria antes e após vinte minutos da administração de salbutamol spray (300 g). Os parâmetros derivados da técnica de oscilações forçadas foram: resistência total, reatância total, resistência extrapolada para o eixo y, coeficiente angular da reta de resistência e complacência dinâmica. Na espirometria, os parâmetros utilizados foram o volume expiratório forçado no primeiro segundo e a capacidade vital forçada. RESULTADOS: No grupo controle, a utilização do broncodilatador produziu alteração significativa na resistência extrapolada para o eixo y (p < 0,001), embora o coeficiente angular da reta de resistência e a complacência dinâmica não tenham apresentado diferenças estatisticamente significativas. A análise dos asmáticos mostrou que a diferença entre as medidas pré e pós-broncodilatador foi significativa, tanto para os parâmetros espirométricos quanto para os de técnica de oscilações forçadas. Valores de p < 0,001 foram obtidos em todas as comparações relacionadas aos asmáticos. CONCLUSÃO: As alterações nos parâmetros obtidos a partir da técnica de oscilações forçadas mostraram-se em estreita concordância com a fisiopatologia da resposta broncodilatadora em asmáticos, indicando que a técnica de oscilações forçadas pode ser útil como análise complementar à espirometria nesses pacientes. OBJECTIVE: To use the forced oscillation technique to evaluate asthma patients presenting positive bronchodilator responses (confirmed through spirometry) and compare the results with those obtained in healthy individuals. METHODS: The study sample consisted of 53 non-smoking volunteers: 24 healthy subjects with no history of pulmonary disease and 29 asthmatics presenting positive bronchodilator response, as determined through analysis of spirometry findings. All of the subjects were submitted to forced oscillation technique and spirometry immediately before and 20 minutes after the administration of salbutamol spray (300 g). The parameters derived from the forced oscillation technique were total respiratory resistance, total respiratory reactance, resistance extrapolated to the y axis, the slope of resistance, and dynamic compliance. The parameters measured in the spirometry evaluation tests were forced expiratory volume in one second and forced vital capacity. RESULTS: In the control group, bronchodilator use produced a significant alteration in the resistance extrapolated to the y axis (p < 0.001), although no significant differences were observed in the slope of resistance or in dynamic compliance. Analysis of the asthma patients revealed significant differences between the prebronchodilator and postbronchodilator values for all spirometry and forced oscillation technique parameters. Values of p < 0.001 were obtained for all comparisons between the two groups. CONCLUSION: The modifications provoked by use of the forced oscillation technique were in direct concordance with the pathophysiology of the bronchodilator response in asthma patients, indicating that the forced oscillation technique could be useful as a complement to spirometry in these patients.

The Forced Oscillation Technique (FOT) is a method for non-invasively assessing respiratory mechanics during spontaneous breathing, demanding little cooperation. The aim of this study was to test the ability of FOT to describe the changes in respiratory mechanics in progressive COPD. The study was performed in a control group formed by 21 healthy subjects and 79 outpatients with COPD, which were classified by spirometry, according to the degree of airway obstruction, in mild, moderate and severe groups. Resistive impedance data were submitted to linear regression analysis over the 4-16 Hz frequency range, which yielded the total respiratory system resistance extrapolated at 0 Hz (R0), the respiratory system conductance (Grs), mean respiratory resistance (Rm), and the resistance/frequency slope (S). Reactance data were interpreted using the mean values (Xm) over the 4-32 Hz frequency range, the dynamic compliance (Crs,dyn), the dynamic elastance (E(rs,dyn)), and the resonant frequency (fr) data. Considering the control and mild groups, the increase of airway obstruction resulted in a significant increase of R0 (P

Thermally sensitive devices—thermistors—have usually been used to monitor sleep-breathing disorders. However, because of their long time constant, these devices are not able to provide a good characterization of fast events, like hypopneas. Nasal pressure recording technique (NPR) has recently been suggested to quantify airflow during sleep. It is claimed that the short time constants of the devices used to implement this technique would allow an accurate analysis of fast abnormal respiratory events. However, these devices present errors associated with nonlinearities and acoustic resonance that could reduce the diagnostic value of the NPR. Moreover, in spite of the high scientific and clinical potential, there is no detailed description of a complete instrumentation system to implement this promising technique in sleep studies. In this context, the purpose of this work was twofold: (1) describe the development of a flexible NPR device and (2) evaluate the performance of this device when compared to pneum...

The clinical application of the current methods of measuring nasal obstruction has been limited by complicated, invasive and stressful procedures that require the full co-operation of the patient. A pilot study is described where a simple way of evaluating nasal obstruction, based on oscillation methods, was investigated. The technique did not disturb spontaneous breathing and required little co-operation and comprehension. Significant differences were obtained when clinically classified normal (5.2 +/- 1.8 cmH2O l(-1) s) and patient (10.6 +/- 5.9 cmH2O l(-1) s) groups were evaluated (p0.01). A significant reduction (p0.02) was also observed in impedance results before (8.5 +/- 1.1 cmH2O l(-1) s) and after (5.2 +/- 1.7 cmH2O l(-1) s) clinically successful nasal surgery, closely reflecting the clinical conditions of the subjects. This simple forced oscillation technique showed good potential for future clinical applications in the pre-screening of nasal patients and the evaluation of therapeutic surgery.

Sleep breathing disorders are estimated to be present in 2%–4% of middle-aged adults. Serious adverse consequences, such as systemic arterial hypertension, myocardial infraction, and cerebrovascular disease, can be related to these conditions. Intellectual deficits associated with attention, memory, and problem-solving have also been associated with a poor quality of sleep. The main causes of these disorders are obstructions resulting from repetitive narrowing and closure of the pharyngeal airway, which have been monitored by indirect measurements of temperature, displacement, and other highly invasive procedures. The measurement of mechanical impedance of the respiratory system by the forced oscillation technique (FOT) has recently been suggested to quantify the respiratory obstruction during sleep. It is claimed that the noninvasive and dynamic characteristics of this technique would allow a noninvasive and accurate analysis of these events. In spite of this high scientific and clinical potential, there is no detailed description of a complete instrumentation system to implement this promising technique in sleep studies. In this context, the purpose of this study was twofold: (1) describe the development of a new computer-based system for identification of the mechanical impedance of the respiratory system during sleep by the FOT and (2) evaluate the performance of this device in the description of respiratory events in conditions including no, mild, serious disease, and therapeutic procedures. These evaluations confirmed the desirable features achieved in laboratory tests and the high scientific and clinical potential of this system.

The simple techniques generally used to investigate the biomechanical properties associated with the respiratory process are able to identify only basic characteristics, just supplying an initial representation of the complex behavior of the respiratory system. A much more detailed description can be obtained by the forced oscillation technique (FOT). Requiring very little cooperation of the subject, this technique allows a noninvasive evaluation of the mechanical impedance of the respiratory system. Although the FOT has a great scientific and clinical potential, this is attended by technical difficulties and has yet to be put to widespread use. In this context, this work describes a new flexible, open architecture, virtual-instrument-based impedance spectrometer for the FOT. After the design details are described, the system accuracy is evaluated investigating mechanical models simulating normal and individuals with restrictive disease. This analysis revealed errors smaller than 4% in modulus and 7° in phase. Experimental results obtained in a normal and an asthmatic subject, presented as examples, revealed mean resistance in asthmatic (5.72 cm H2O/l/s) higher than in normal (2.47 cm H2O/l/s). The mean-reactance curve revealed higher resonance frequency in the asthmatic subject (∼29 Hz) than in the normal one (∼9 Hz). A higher influence of the upper airways impedance of the asthmatic individual was also observed. These results are in close agreement with physiological fundamentals, supplying substantial evidence that this instrument can contribute to the production of more detailed biophysical respiratory descriptions and composes an improved basis for the fast and easy implementation of complex medical research projects.

Background: Despite the gradual improvement in treatment procedures and cure rates of acromegaly, a steady increase in the mortality rate due to respiratory disease has been documented in recent decades. In this study, our objectives were to describe the abnormalities in lung structure and function that occur in acromegalic patients and to correlate these changes with hormonal levels. Methods: This cross-sectional study included 20 acromegalic patients and 20 age-and height-matched control subjects, all non-smokers. All subjects underwent spirometry, whole body plethysmography, carbon monoxide diffusing capacity, and respiratory muscle strength. Acromegalic patients also performed high-resolution computed tomography (HRCT). Results: Most patients were female (65%), with a mean age of 52.5 ± 13 years. Acromegalic patients showed lower values of maximum expiratory pressure (55.9 ± 17.1 vs. 103.7 ± 19.2%; p < 0.001) and maximum inspiratory pressure (71.4 ± 27.8 vs. 85.3 ± 24.1%; p = 0.005) compared to control subjects. The values of forced vital capacity (107.1 ± 15.9 vs. 98.9 ± 21.4%; p = 0.028), total lung capacity – TLC (107.3 ± 12.9 vs. 93.7 ± 7.60%; p = 0.002), residual volume (114.1 ± 22.7 vs. 90.0 ± 14.6%; p < 0.001), and airways’ resistance (3.82 vs. 2.31 cmH2O/L/s; p = 0.039) were greater in acromegalic patients than in control subjects. The difference between the TLC measured by plethysmography and the VA (alveolar volume) measured during the DLCO maneuver was higher in acromegalic patients than in control subjects (0.69 ± 0.46 vs. 0.19 ± 0.61 L; p = 0.021). The main findings in HRCT in acromegalic patients were air trapping, airway calcification and bronchiectasis, which were observed in 60%, 40% and 35% of cases, respectively. There was no significant correlation between the levels of growth hormone and insulin-like growth factor I, the lung function and the air trapping. Conclusions: Acromegalic patients show changes consistent with the involvement of the small airways and ventilation inhomogeneity, both in terms of lung function and structure. However, air trapping cannot be explained either by hormone levels or changes in lung function.

The aim of the present study was to analyze the changes in the respiratory system impedance (Zrs) in the different phases of the respiratory cycle of patients with Chronic Obstructive Pulmonary Disease (COPD). This research was conducted using a monofrequency version of the forced oscillation technique (mFOT) and consisted of a controlled observational study where 31 individuals were analyzed, 8 controls and 23 individuals with COPD. The patients presented different degrees of airway obstruction. It was observed an increase in the Zrs measured in the beginning of inspiration, during the inspiratory phase, at the beginning of expiration, and during the expiratory phase (p