Forced Oscillation Technique Parameters Research Articles

Changes in fractional exhaled nitric oxide, forced expiratory volume in one second, and forced oscillation technique parameters over three years in adults with bronchial asthma managed under Yokohama Seibu Hospital’s coordinated care system

BackgroundIn western Yokohama, our hospital and primary care clinics manage adults with asthma via a coordinated care system. We investigated the changes in the fractional expired nitric oxide (FeNO), forced expiratory volume in 1 second (FEV1), and forced oscillation technique (FOT) parameters over 3 years in a cohort of patients in our collaborative system.MethodsFrom 288 adults with well controlled asthma managed under the Yokohama Seibu Hospital coordinated care system between January 2009 and May 2018, we selected 99 subjects to undergo spirometry, FeNO and FOT testing over 3 years and analyzed the changes in these parameters.ResultsOf the 99 patients enrolled, 17 (17.2%) experienced at least one exacerbation (insufficiently controlled (IC)), whereas, 82 (82.8%) remained in well controlled during the 3-year study period. Of well-controlled patients, 54 patients (54.5%) met the criteria for clinical remission under treatment (CR); the remaining 28 patients did not meet the CR criteria (WC). There were no differences in FeNO, FEV1, or FOT parameters at baseline among the IC, WC, and CR groups. The levels of FEV1 decreased gradually, whereas the levels of FeNO decreased significantly over 3 years. The levels of percent predicted FEV1 (%FEV1) significantly increased. We also observed significant improvement in FOT parameters; reactance at 5 Hz (R5), resonant frequency (Fres), and integral of reactance up to the resonant frequency (AX). The CR group demonstrated significant relationships between the change in FeNO and the change in FEV1 and between the change in FEV1 and the change in FOT parameters. No significant correlations emerged in the IC or WC group.ConclusionThe decrease in FeNO and increase in %FEV1, we observed in all study participants suggest that the coordinated care system model benefits patients with asthma. Although it is difficult to predict at baseline which patients will experience an exacerbation, monitoring changes in FeNO and FEV1 is useful in managing patients with asthma. Furthermore, monitoring changes in R5, Fres, and AX via forced oscillation technique testing is useful for detecting airflow limitation.

Bronchial obstruction in osteogenesis imperfecta can be detected by forced oscillation technique.

Respiratory insufficiency is a leading cause of death in individuals with osteogenesis imperfecta (OI). However, evaluating pulmonary function in OI presents challenges. Commonly used pulmonary function tests such as spirometry and body plethysmography are sometimes difficult to perform for OI patients, and reference intervals are not always applicable. The forced oscillation technique (FOT) is a patient-friendly method for detecting respiratory abnormalities that requires no effort from the patient. This study investigates the feasibility of FOT in the evaluation of respiratory function in the clinical management of OI patients. Twelve OI patients, comprising eight with Sillence OI I, two with OI IV, and two with OI III, underwent spirometry, body plethysmography, and FOT, both pre-and post-administration of salbutamol. FOT measurements exhibited consistent trends that aligned with spirometry and body plethysmography findings. The resistance at 8 Hz decreased after the administration of salbutamol, indicating that FOT is able to detect bronchial obstruction and its alleviation by medication (p < 0.05). The resonant frequency during expiration was higher than during inspiration in nearly all patients, suggesting obstructive disease. The technique gives insight into both inspiratory and expiratory impairment of pulmonary ventilation. The main FOT parameters showed a relatively high repeatability in duplicate measurements. Bronchial obstruction can be detected by FOT in patients with OI during quiet breathing, making it an easily executable alternative to other lung function measurements. The technique can detect the bronchodilator effect of sympathomimetic medication. It has the potential to provide information on expiratory flow limitation, pulmonary restriction, and reduced lung compliance.

Pulmonary functions, nasal symptoms, and quality of life in patients with primary ciliary dyskinesia (PCD).

Several factors may influence quality of life (QOL) for patients with primary ciliary dyskinesia (PCD). We aimed to evaluate the association between pulmonary functions, nasal symptoms and QOL in PCD patients. A prospective single center study. Patients performed spirometry, whole body plethysmography, forced oscillation technique (FOT), lung clearance index (LCI), 6-min walk test (6MWT), and filled two questionnaires: a specific PCD QOL questionnaire (PCD-QOL) and Sino-nasal outcome test (SNOT-22) questionnaire, assessing symptoms of chronic rhinosinusitis and health related QOL. Twenty-seven patients (56% females), age 19.4 ± 10.5 years were included; their, FEV1 was 74.6 ± 22.7%, and RV/TLC was (157.3 ± 39.3% predicted). Health perception and lower respiratory symptoms domains of PCD-QOL had the lowest score (median [IQR]: 50 [33.3-64.6] and 57.1 [38.9-72.2], respectively). FOT parameters correlated with several PCD-QOL domains. R5 z-score (indicating total airway resistance) and AX z-score (indicating airway reactance) correlated negatively with physical domain (r = -0.598, p = .001, and r = -0.42, p = .03, respectively); R5 z-score also correlated negatively with hearing domain (r = -0.57, p = .002). R5-20 z-score (indicating small airway resistance) correlated negatively with role domain (r = -0.49, p = .03). SNOT-22 score correlated negatively with several PCD-QOL domains (lower respiratory symptoms r = -0.77, p < .001; physical r = -0.72, p < .001; upper respiratory symptoms r = -0.66, p < .001). No correlations were found between spirometry values, LCI, 6MWT, and PCD-QOL. FOT suggested small airway dysfunction, and correlated negatively with several PCD-QOL domains. Nasal symptoms had strong negative correlations with PCD-QOL. Larger longitudinal studies will further elucidate factors affecting QOL in PCD.

Donor-Recipient Size Mismatch, Donor Age and Interstitial Lung Disease Are Associated with Abnormal Reactance, Resistance and Airway Closure After Bilateral Lung Transplantation

<h3>Purpose</h3> The effect of donor-recipient demographics and features on recipient lung mechanics after transplantation (LTx) is unknown. The Forced Oscillation Technique (FOT) measures the mechanical properties of the respiratory system. We have recently developed novel analyses of FOT parameters that assess airway closure. This study aims to assess the effect of donor and recipient clinical history on recipient respiratory system mechanics post LTx using FOT. <h3>Methods</h3> Bilateral LTx recipients were recruited into a multi-centre (Alfred Hospital, Melbourne and St Vincent's Hospital, Sydney) prospective study. Subjects underwent spirometry, plethysmography and FOT (Tremoflo 2000, Thorasys, Canada) on one occasion at 3-6 months after LTx. Donor lung size was estimated from predicted total lung capacity equations. General linear models were used to assess the effect of donor-recipient demographics and features on respiratory mechanics from FOT. <h3>Results</h3> A total of 63 patients (52% male, age 52 ±15yrs) were included. Oversized donor lungs (donor predicted TLC > recipient TLC pre-Tx) were associated with increased respiratory reactance (Xrs5, p=0.041) and increased peripheral airway resistance (R5-19, p=0.002). Undersized donor lungs (donor predicted TLC < recipient TLC pre-Tx) were associated with increased total and peripheral airway resistance (R5 and R5-19, p=0.043 and p=0.003) and markers of early airway closure from FOT (Xrs5 and DR1, p=0.047 and p=0.038). Recipients transplanted for interstitial lung disease (ILD) were more likely to have increased total and peripheral airway resistance (R5 and R5-19, p=0.035 and p=0.038). Increasing donor age was more associated with airflow limitation (FER, p=0.009) and peripheral airway resistance (R5-19, p=0.042). <h3>Conclusion</h3> LTx recipients who receive over or under-sized donor lungs, older donor lungs, or had ILD as their native lung disease were more likely to have abnormal respiratory system mechanics. Longitudinal assessment is required to understand the trajectory of novel oscillometry parameters, including FOT, in relation to lung allograft dysfunction.

Mucus Plugs and Small Airway Dysfunction in Asthma, COPD, and Asthma-COPD Overlap.

PurposeThere are reports concerning mucus plugs detected on high-resolution computed tomography images and airflow obstruction in asthma and chronic obstructive pulmonary disease (COPD). However, little is known about the associations between mucus plugs and small airway dysfunction (SAD). We evaluated the relationship between mucus plugs and pulmonary function in patients with asthma, COPD, and asthma-COPD overlap (ACO), and investigated the relevance to SAD and type 2 inflammation in a retrospective study.MethodsSubjects included 49 asthmatic, 40 ACO, and 41 COPD patients. ACO was diagnosed based on the Japanese Respiratory Society ACO guidelines. Clinical and laboratory parameters, including blood eosinophil count, serum total IgE levels, fractional exhaled nitric oxide (FeNO), spirometry, and forced oscillation technique (FOT), were compared between patients with and without mucus plugs.ResultsMucus plugs were found in 29 (59%) asthmatic, 25 (65%) ACO, 17 (41%) COPD patients. Patients with mucus plugs had reduced spirometry and larger FOT parameters, especially in COPD patients. Mucus scores correlated positively with IgE in ACO and FeNO in asthmatic patients, but not in COPD patients. Multivariate logistic regression analysis revealed that SAD parameters, including forced vital capacity and resonant frequency, a respiratory reactance parameter, were significantly associated with the presence of mucus plugs in the whole studied population.ConclusionsSAD, rather than large airway dysfunction, was associated with mucus plugs in asthma, ACO, and COPD patients.

Self-reported exercise-induced dyspnea and airways obstruction assessed by oscillometry and spirometry in adolescents.

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

Forced oscillatory parameters as predictors of COPD assessment test improvement in untreated COPD patients

BackgroundFew studies have examined whether baseline spirometry and the forced oscillation technique (FOT) would predict The COPD Assessment Test (CAT) score improvement after treatment of untreated COPD patients. MethodsThe study subjects included 65 untreated COPD patients. They underwent the CAT, spirometry, and FOT (MostGraph) before and after treatment for more than 2 months. In addition, recursive partitioning analysis was performed using spirometry and the FOT parameters to identify the predictors of CAT improvement (CAT score ≥2). ResultsCAT scores and lung function significantly improved after treatment. Recursive partitioning analysis identified 3 improved classes, defined by Rrs at 20 Hz (R20), Xrs at 5 Hz (X5), and ΔX5, but not by spirometry. The accuracy of predicting CAT improvement was as follows: odds ratio, 25.3; 95 % confidence interval, 6.1 to 104.1; sensitivity, 91.2 %; specificity, 71.0 %; positive likelihood ratio, 3.14; and negative likelihood ratio, 0.12. ConclusionsFOT helps predict improved health status in untreated COPD patients.

Artificial intelligence for quality control of oscillometry measures

BackgroundThe forced oscillation technique (FOT) allows non-invasive lung function testing during quiet breathing even without expert guidance. However, it still relies on an operator for excluding breaths with artefacts such as swallowing, glottis closure and coughing. This manual selection is operator-dependent and time-consuming. We evaluated supervised machine learning methods to exclude breaths with artefacts from data analysis automatically. MethodsWe collected 932 FOT measurements (Resmon Pro Full, Restech) from 155 patients (6–87 years) following the European Respiratory Society (ERS) technical standards. Patients were randomly assigned to either a training (70%) or test set. For each breath, we computed 71 features (including anthropometric, pressure stimulus, breathing pattern, and oscillometry data). Univariate filter, multivariate filter and wrapper methods for feature selection combined with several classification models were considered. ResultsTrained operators identified 4333 breaths with- and 10244 without artefacts. Features selection performed by a wrapper method combined with an AdaBoost tree model provided the best performance metrics on the test set: Balanced Accuracy = 85%; Sensitivity = 79%; Specificity = 91%; AUC-ROC = 0.93. Differences in FOT parameters computed after manual or automatic breath selection was less than ∼0.25 cmH2O*s/L for 95% of cases. ConclusionSupervised machine-learning techniques allow reliable artefact detection in FOT diagnostic tests. Automating this process is fundamental for enabling FOT for home monitoring, telemedicine, and point-of-care diagnostic applications and opens new scenarios for respiratory and community medicine.

Reference value of Forced Oscillation Technique for healthy preschool children.

The reference values of Forced Oscillation Technique (FOT) parameters of the inspiratory and expiratory phase for preschool children have not yet been established. To evaluate FOT measures in Thai healthy preschool children. Preschool children, aged 3-6 years, were screened. Children who were positive for the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire for asthma, positive family history of allergic diseases, recent lower respiratory tract infections, and environmental tobacco smoke were excluded. FOT parameters, including resistance (Rrs), reactance (Xrs), frequency of resonance (Fres) and area of reactance (ALX), were measured. A total of 390 healthy children with the mean age of 5.1 ± 0.9 years were enrolled. FOT was successfully performed in 378 children (96.9%). The mean (SD) for the whole breath (WB) resistance at 5Hz (R5), 20 Hz (R20) and R5-20 were 11.49 (2.69) cmH2O/L/s, 9.46 (2.19) cmH2O/L/s and 2.02 (0.82) cmH2O/L/s, respectively. The median (IQR) for WB reactance at 5Hx (X5), Fres and ALX were -1.51 (-2.37 to -0.96) cmH2O/L/s, 11.17 (8.50-15.65) Hz, and 7.53 (3.72-14.32) cmH2O/L/s, respectively. Significantly difference in WB R5, R20, X5, Fres and ALX between male and female children were demonstrated. The expiratory phase R5, R20, R5-20 were significantly higher than those of the inspiratory phase (p < 0.001). There are significant correlations between the height and FOT parameters. Reference curve for the FOT parameters was generated based on height using the lambda-mu-sigma (LMS) method. Reference curve of FOT parameters measured in healthy preschool children were demonstrated. Majority of preschool children could perform FOT method.

Examination of predictable factors of perioperative respiratory complications by preoperative forced oscillation technique parameters.

In this study, we investigated whether pulmonary function tests such as forced oscillation technique parameters could predict perioperative respiratory complications. In the results of our study, perioperative respiratory complications cannot be predicted using the results of preoperative pulmonary function tests and forced oscillation technique parameters. Patients who are judged by comprehensive preoperative judgment to be suitable for general anesthesia may not need to consider the risk of perioperative complications using pulmonary function test.

Clinical Application of Forced Oscillation Technique (FOT) in Early Detection of Airway Changes in Smokers.

The forced oscillation technique (FOT) is a non-invasive method to assess airway function by emitting oscillatory signals into the respiratory tract during tidal ventilation. This opinion piece discusses the current use, trialled modification and future directions in utilizing FOT as a novel diagnostic tool for early detection of small airway changes in smokers. The published evidence to date has shown that FOT parameters could be a sensitive diagnostic tool to detect early respiratory changes in smokers. Multiple frequencies and the frequency dependence of resistance and reactance can provide the most valuable and early information regarding smoking induced changes in airways. Considering its non-invasiveness, lower level of discomfort to patients than spirometry, feasibility, and cost effectiveness, it could be the first-choice diagnostic technique for detection of early respiratory changes in smokers. The finding of FOT could further be supported and correlated with inflammatory markers.

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.

Day-to-day variability of forced oscillatory mechanics for early detection of acute exacerbations in COPD.

Telemonitoring trials for early detection of acute exacerbations of chronic obstructive pulmonary disease (AECOPD) have provided mixed results. Day-to-day variations in lung function measured by the forced oscillation technique (FOT) may yield greater insight. We evaluated the clinical utility of home telemonitoring of variability in FOT measures in terms of 1) the relationship with symptoms and quality of life (QoL); and 2) the timing of variability of FOT measures and symptom changes prior to AECOPD. Daily FOT parameters at 5 Hz (resistance (R) and reactance (X); Resmon Pro Diary, Restech Srl, Milan, Italy), daily symptoms (COPD Assessment Test (CAT)) and 4-weekly QoL data (St George's Respiratory Questionnaire (SGRQ)) were recorded over 8-9 months from chronic obstructive pulmonary disease (COPD) patients. Variability of R and X was calculated as the standard deviation (sd) over 7-day running windows and we also examined the effect of varying window size. The relationship of FOT versus CAT and SGRQ was assessed using linear mixed modelling, daily changes in FOT variability and CAT prior to AECOPD using one-way repeated measures ANOVA. Fifteen participants with a mean±sd age of 69±10 years and a % predicted forced expiratory volume in 1 s (FEV1) of 39±10% had a median (interquartile range (IQR)) adherence of 95.4% (79.0-98.8%). Variability of the inspiratory component of X (indicated by the standard deviation of inspiratory reactance (SDXinsp)) related to CAT and weakly to SGRQ (fixed effect estimates 1.57, 95% CI 0.65-2.49 (p=0.001) and 4.41, 95% CI -0.06 to 8.89 (p=0.05), respectively). SDXinsp changed significantly on the same day as CAT (1 day before AECOPD, both p=0.02) and earlier when using shorter running windows (3 days before AECOPD, p=0.01; accuracy=0.72 for 5-day windows). SDXinsp from FOT telemonitoring reflects COPD symptoms and may be a sensitive biomarker for early detection of AECOPD.

Relationships among bronchodilator reversibility, the fraction of exhaled nitric oxide, and the parameters of the forced oscillation technique in adult asthma treated with inhaled corticosteroids and long-acting β2 agonists combination

In bronchial asthma, both airway inflammation and reversible airway narrowing require assessment and treatment. These two pathologies are treated primarily with inhaled corticosteroids (ICS) and long-acting β2 agonists (LABA), respectively. Therefore, ICS-LABA combinations are widely used to treat asthma. Airway inflammation and reversible airway narrowing are assessed primarily with fraction of exhaled nitric oxide (FENO) and bronchodilator reversibility (BDR). The forced oscillation technique (FOT) has recently attracted attention as a method for assessing obstructive respiratory disturbance. However, little is known about the relationships among these assessments. Therefore, we investigated the relationships among BDR, FENO, and FOT during ICS-LABA combination therapy. The subjects comprised 87 patients (25 men and 62 women) with asthma undergoing ICS/LABA combination therapy from July to September 2017. We applied the FENO test, FOT, and BDR testing without the patients stopping their therapy. The rates of change in FEV1 (ΔFEV1%) was correlated with FENO (r = 0.278). Among the FOT parameters, X5 (r = −0.263), Fres (r = 0.292), and AX (r = 0.245) were significantly correlated with ΔFEV1%. FENO, Fres and %FEV1 at baseline in these stable asthmatics were significantly assosiated with ΔFEV1% independently of the effects of age, atopy and body mass index (BMI). These results suggest that FENO and the results of respiratory function testing and FOT reflect different aspects of asthma and should be combined and comprehensively evaluated.

Bronchodilator Response Assessed by the Forced Oscillation Technique Identifies Poor Asthma Control With Greater Sensitivity Than Spirometry

Persistent bronchodilator response (BDR) following diagnosis of asthma is an underrecognized treatable trait, associated with worse lung function and asthma control. The forced oscillation technique (FOT) measures respiratory system impedance, and BDR cutoffs have been proposed for healthy adults; however, the relevance in asthma is unknown. We compared BDR cutoffs, using FOT and spirometry, in asthma and the relationship with asthma control. Data from patients with asthma who withheld bronchodilator medication for at least 8h before a tertiary airway clinic visit were reviewed. All subjects performed FOT and spirometry before and after salbutamol administration, and completed the Asthma Control Test. FOT parameters examined included respiratory system resistance (R5) and reactance (X5) at 5Hz, and area under the reactance curve (AX). BDR was defined by standard recommendations for spirometry and based on the 95th percentile of BDR in healthy adults for FOT. Fifty-two subjects (18 men; mean age, 53 ± 18 years) were included. BDR was identified more frequently by FOT than spirometry (54%vs27%of subjects). BDR assessed by X5 and AX, but not R5, was associated with spirometric BDR (χ2, P< .01) and correlated with asthma control (X5: rs= -0.36, P< .01; AX: rs= 0.34, P= .01). BDR measured by reactance parameters identified more subjects with poor asthma control than did spirometry (AX, 69%vsspirometry, 41%). BDR assessed by FOT can identify poor asthma control. Reactance parameters were more sensitive in identifying poor asthma control than spirometry, supporting the use of FOT to complement spirometry in the clinical management of asthma.

Effect of vitamin D on lung function assessed by forced oscillation technique in asthmatic children with vitamin D deficiency: A randomized double-blind placebo-controlled trial.

The role of vitamin D and asthma in pulmonary function changes showed conflicting result. To evaluate if vitamin D treatment would improve lung function assessed by forced oscillation technique (FOT) in vitamin D deficient asthmatic children. A randomized double-blind placebo-controlled trial was performed in children, aged 3-18 years with well controlled asthma. Serum total 25(OH)D and FOT parameters including respiratory resistance at 5 Hz (R5), at 20 Hz (R20), respiratory reactance at 5 Hz (X5) and area of reactance (ALX), resonance frequency (Fres) were evaluated at baseline, 1 month and 3 months. Vitamin D deficient patients (serum total 25(OH)D < 20 ng/ml) were randomized to receive treatment with vitamin D2 (tVDD) or placebo (pVDD). Non-vitamin D deficient patients (nVDD) received placebo as a control group. A total of 84 children were recruited, 43 patients in nVDD group, 20 in tVDD group and 21 in pVDD group. There were no significant differences in age, sex, height and weight among groups. There were no significant differences of FOT parameters among groups at all visits. There was a trend toward decrease in R5/R20 from baseline to 1 month and 3 months visit in all groups, but the statistically significant improvement was observed only in nVDD group. Serum 25(OH)D showed no correlation with % predicted of FOT measures. Vitamin D treatment in asthmatic children who had vitamin D deficiency may have no short term beneficial effect on pulmonary function assessed by FOT. Vitamin D supplementation in all asthmatic patient needs further study.

Forced oscillation technique as a predictor for loss of control in asthmatic children.

BackgroundA reliable objective tool using as a predictor of asthma control status could assist asthma management.ObjectiveTo find the parameters of forced oscillation technique (FOT) as predictors for the future loss of asthma symptom control.MethodsChildren with well-controlled asthma symptom, aged 6–12 years, were recruited for a 12-week prospective study. FOT and spirometer measures and their bronchodilator response were evaluated at baseline. The level of asthma symptom control was evaluated according to Global Initiative for Asthma.ResultsAmong 68 recruited children, 41 children (60.3%) maintain their asthma control between 2 visits (group C-C), and 27 children (39.7%) lost their asthma control on the follow-up visit (group C-LC). Baseline FOT parameters, including the values of respiratory resistance at 5 Hz (R5), respiratory resistance at 20 Hz (R20), respiratory reactance at 5 Hz, area of reactance, %predicted of R5 and percentage of bronchodilator response (%∆) of R5 and R20 were significantly different between C-C and C-LC groups. In contrast, only %∆ of forced vital capacity, forced expiratory volume in 1 second (FEV1), and FEF25%–75% (forced expiratory flow 25%–75%) were significantly different between groups. Multiple logistic regression analysis revealed that %predicted of R5, %∆R5, %predicted of FEV1 and %∆FEV1 were the predictive factors for predicting the future loss of asthma control. The following cutoff values demonstrated the best sensitivity and specificity for predicting loss of asthma control: %predicted of R5=91.28, %∆R5=21.2, %predicted of FEV1=89.5, and %∆FEV1=7.8. The combination of these parameters predicted the risk of loss of asthma control with area under the curve of 0.924, accuracy of 83.8%.ConclusionResistance FOT measures have an additive role to spirometric parameter in predicting future loss of asthma control.

Exercise-Induced Bronchoconstriction Identified Using the Forced Oscillation Technique.

Objective: Lung mechanics using the forced oscillation technique (FOT) is suggested to be equivalent and more sensitive in determining exercise-induced bronchoconstriction (EIB) than spirometry. Dynamic alterations in minute ventilation (VE) may affect this measurement. We investigated changes in FOT parameters post exercise challenge (EC) in people with asthma as compared to spirometry. The rate of recovery and any effect of raised VE following exercise on FOT parameters were also assessed.Method: Airway resistance (R5) and reactance (X5) at 5 Hz and VE were measured prior to forced expiratory volume in 1 s (FEV1) before and up to 20 min after a standard EC in people with asthma and healthy controls. Airway hyperresponsiveness to the hyperosmolar mannitol test was measured in the asthmatic subjects within 1 week of the EC. Baseline and sequential measures were assessed using repeated measures ANOVA and Pearson’s correlation. Group demographics and recovery data were compared using an unpaired t test.Results: Subjects with current asthma (n = 19, mean ± SD age 28 ± 6 years) and controls (n = 10, 31 ± 5 years) were studied. Baseline FEV1, R5, X5, and VE were similar between groups (p > 0.09). Airway hyperresponsiveness was present in 12/19 asthmatic subjects. The EC max % change of R5 and X5 correlated with FEV1 (r > 0.90) and were only different to controls in those with asthma that responded by FEV1 criteria (p < 0.01). EC recovery of R5 was similar to FEV1; however, X5 was greater (p = 0.03). Elevated VE post EC did not affect the % change in FOT parameters across all subjects (p > 0.3). R5 and X5 were highly sensitive in determining a positive EC response (80–86%), but X5 was more specific (93 vs. 80%).Conclusion: FOT parameters tracked with forced maneuvers and were not influenced by increased ventilation following an exercise challenge designed to elicit EIB. FOT identified EIB similarly to spirometry in patients with asthma.

Within-breath changes in respiratory system impedance in children with cystic fibrosis.

The aim of this study was to assess within-breath respiratory system impedance by the forced oscillation technique (FOT) in children with cystic fibrosis (CF) and relate it to the underlying lung disease. Thirty-three children with CF (median [range] age 12.0 [6-17] years) underwent FOT at 8 Hz during tidal breathing, multiple breath nitrogen washout (LCI), spirometry (FEV1), body plethysmography (RV/TLC), and magnetic resonance imaging (MRI). FOT outcomes included: mean inspiratory, expiratory, and whole breath resistance (R8INSP , R8EXP , R8TOT ) and reactance (X8INSP , X8EXP , X8TOT ), and the differences between X8INSP and X8EXP (ΔX8). Morphological changes were evaluated by MRI using CF-specific morphological scores. Spearman correlation was performed to examine the correlation between FOT indices and other parameters. FEV1 was negatively correlated with R8EXP (r = -0.52, P = 0.002) and ΔX8 (r = -0.55, P = 0.001), and positively correlated with and X8EXP (r = 0.56, P < 0.001). RV/TLC was positively correlated with R8EXP (r = 0.43, P = 0.013), and ΔX8 (r = 0.54, P = 0.001) and negatively correlated with X8EXP (r = -0.54, P = 0.001). We found poor correlation between FOT parameters and LCI and no correlation between FOT parameters and MRI scores. In children with CF, changes in within-breath FOT parameters are consistent with peripheral obstruction and dynamic airway compression, while they are not associated with ventilation heterogeneities and morphological alterations.

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

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