Clinical application value of impulse oscillometry in geriatric patients with COPD

Diagnosis and evaluation of small airway disease and COPD using impulse oscillometry

Impulse oscillometry (IOS) is a sensitive tool for assessing small airway function in patients with chronic obstructive pulmonary disease (COPD). This study aimed to differentiate between COPD, small airway disease (SAD), and normal groups using IOS, and to evaluate the clinical applicability of IOS. This retrospective cohort study was conducted from January 2020 to February 2022. The eligible population comprised adult patients who simultaneously underwent IOS and pulmonary function tests. The diagnostic value of IOS in differentiating SAD and/or COPD from control was analyzed, and the correlations among IOS parameters, lung function, and radiological assessment results were determined. Among the enrolled 306 patients, 38 (12.4%) had SAD and 134 (43.8%) had COPD. The remainder comprised the control group without COPD and/or SAD. Abnormal airway resistance according to IOS parameters was detected in 17.2% of the patients in the control group, 47.2% of those in the SAD group, and 55.2% of those in the COPD group. Airway resistance estimated by IOS were significantly higher in the SAD and COPD groups than in the control group and correlated with lung function and radiological airway wall thickness. We developed a composite index called the IOS severity index (IOSsi) using IOS parameters that can predict SAD and COPD, and IOSsi showed significantly differentiation of SAD and/or COPD from control. Especially, IOSsi value ≥ 4 was associated with an increased risk of SAD and/or COPD and also with risk for moderate-to-severe exacerbation in patients with COPD. IOS may be a useful tool to differentiate disease status and evaluate disease severity and prognosis in patients with SAD and/or COPD, and a prognostic factor of COPD.

Impulse oscillometry system and pulmonary function test assessment of the impact of tumor location, staging, and pathological type on lung function in primary lung cancer

PURPOSE

To study the effects of tumor site, stage, pathologic type and imaging findings on lung function in primary lung cancer, as well as the correlation between impulse oscillometry system (IOS) and pulmonary function test (PFT) parameters.

METHODS

The impact of tumor location, staging, and pathological type on lung function were evaluated in 219 patients with primary lung cancer through IOS and PFT. Spearman correlation coefficient was used to analyze the relationship between IOS parameters and PFT parameters.

RESULTS

The PFT parameters in adenocarcinoma were significantly higher than those in SCLC, while the other parameters in IOS were obviously lower than those in SCLC except X5Hz (P < 0.05). The PFT parameters of FVC%, FEV1% and MVV% in SCC were evidently higher than those in SCLC, while the parameters of IOS were significantly lower than those in SCLC (P < 0.05). The PFT parameters of adenocarcinoma were higher than those of SCC (P < 0.05). In the PFT parameters of stage I patients, FEV1/FVC%, MEF50%, MMEF75/25%, and DLCO% were markedly higher than those of stage II patients, and FVC%, FEV1%, FEV1/FVC%, MEF50%, MEF25%, PEF%, MMEF75/25%, TLC%, and DLCO% were obviously higher than those of stage III and IV patients; and the MVV%, Z5Hz%, R5Hz% in IOS parameters were obviously lower than those in stage III, while Fres (1/s) and X5Hz were significantly lower than those in stage IV (P < 0.05). Compared with Phase IV, the X5Hz of stage II patients was clearly higher (P = 0.023). Besides, PFT parameters of peripheral lung cancer were obviously higher than those of central lung cancer (P < 0.05), while Z5Hz%, Fres (1/s) and R5Hz% of IOS parameters were clearly lower than those of central lung cancer (P < 0.05). Moreover, for patients without and with other pulmonary imaging manifestations, the PFT parameters of the former were significantly higher than those of the latter (P < 0.05), while only Fres (1/s) of IOS parameters was significantly lower than the latter (P < 0.05). Furthermore, there is a low to moderate correlation between IOS parameters and PFT parameters.

CONCLUSION

Patients with central SCLC and SCC and advanced lung cancer had the worst lung function. The IOS parameters show a good correlation with the traditional PFT parameters, and IOS can be used as an alternative measurement method for PFT when necessary.

Diagnostic value of impulse oscillometry in chronic obstructive pulmonary disease: a multicentre, retrospective, observational study

OBJECTIVES

Diagnosis and assessment of chronic obstructive pulmonary disease (COPD) rely extensively on spirometry, which necessitates patient cooperation. The clinical value of impulse oscillometry (IOS) as a non-volitional method in patients with COPD remains uncertain.

DESIGN

This retrospective observational study was conducted using patient data from between January 2014 and December 2015.

SETTING

Five public hospitals in China: West China Hospital, Nuclear Industry 416 Hospital, Suining Central Hospital, Affiliated Hospital, Medical College of Chengdu University and 363 Hospital.

PARTICIPANTS

The study included 6307 participants aged>40 years, comprising 2109 COPD patients and 4198 general non-COPD individuals, according to the Global Initiative for Obstructive Lung Disease (GOLD) spirometry standard. Participants with lung cancer, pulmonary tuberculosis, pneumonia or those who underwent lung resection were excluded from the study.

OUTCOME MEASURES AND ANALYSIS

Demographic data, spirometry results and IOS results were collected. Spearman's correlation analysis was used to examine the correlation between the IOS and spirometry parameters. Receiver operating characteristic curve analysis was used to evaluate the IOS performance in COPD diagnosis and severity staging.

RESULTS

Patients with COPD exhibited significant increases in Z5, R5, R20, R5-R20, Fres and Rp, but a decrease in X5 compared with non-COPD subjects (p<0.0001). IOS parameters, including Z5, R5-R20, Fres, Rp and X5, varied with the GOLD stages, with mild-to-moderate correlations with MMEF25%-75%, forced expiratory volume in one second (FEV1)/forced vital capacity and FEV1%, respectively. However, the combination of these five IOS parameters did not exhibit ideal performance in diagnosing COPD (area under the curve (AUC) 0.78; sensitivity 63.68%; specificity 80.09%), differentiating GOLD stage 1 patients from the general non-COPD population (AUC 0.71; sensitivity 54.71%; specificity 77.49%) or identifying GOLD stages 3 and 4 patients among those with COPD (AUC 0.75; sensitivity 69.51%; specificity 70.32%).

CONCLUSION

IOS parameters, while showing good correlation with spirometry in patients with COPD, did not perfectly substitute for spirometry in diagnosing COPD, especially in the early and advanced stages of the disease.

Clinical Value of Impulse Oscillometry in Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-Analysis

INTRODUCTION

Impulse oscillometry (IOS) is an effortless test compared to spirometry. Numerous studies explored the role of IOS in spirometry-based chronic obstructive pulmonary disease (COPD), but most of them had limited sample sizes with poor statistical power. This systematic review and meta-analysis aimed to pool the individual data and quantitatively analyze the clinical value of IOS in COPD.

METHODS

PubMed, Web of Science, Ovid, Cochrane Library, China National Knowledge Internet, and Wanfang were searched for studies with comparisons of IOS indicators between COPD patients and healthy controls, including respiratory resistance at 5 Hz (R5) and 20 Hz (R20), difference between R5 and R20 (R5-R20), respiratory reactance at 5 Hz (X5), resonant frequency (Fres), and area of reactance (Ax). Meta-analyses were conducted to calculate the weighted mean differences (WMDs) and 95% confidence intervals (CIs).

RESULTS

39 eligible studies were enrolled, involving 6,144 COPD patients and 4,611 healthy controls. Relative to healthy controls, COPD patients had significantly higher R5 (WMD: 0.17, 95% CI: 0.14, 0.20), R5-R20 (WMD: 0.13, 95% CI: 0.11, 0.15), Fres (WMD: 9.04, 95% CI: 7.66, 10.42), Ax (WMD: 1.24, 95% CI: 0.86, 1.61), and lower X5 (WMD: -0.15, 95% CI: -0.18, -0.11), and such differences became even greater as the Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage escalated. Pooled correlation coefficients presented that R5, R5-R20, Fres, and X5 were significantly related to post-bronchodilator forced expiratory volume in the first second (FEV1)/forced vital capacity ratio (meta r = -0.37, -0.45, -0.53, and 0.42, respectively) and FEV1 as a percentage of predicted value (meta r = -0.43, -0.54, -0.59, and 0.56, respectively).

CONCLUSION

IOS may be a supplement to spirometry in diagnosing and assessing COPD, especially when spirometry is inappropriate. More well-designed, large sample-sized, prospective studies are warranted to establish an IOS-based criterion for COPD management.

Using Machine Learning with Impulse Oscillometry Data to Develop a Predictive Model for Chronic Obstructive Pulmonary Disease and Asthma

We aimed to develop and validate a machine learning model using impulse oscillometry system (IOS) profiles for accurately classifying patients into three assessment-based categories: no airflow obstruction, asthma, and chronic obstructive pulmonary disease (COPD). Our research questions were as follows: (1) Can machine learning methods accurately classify obstructive disease states based solely on multidimensional IOS data? (2) Which IOS parameters and modeling algorithms provide the best discrimination? We used data for 480 patients (240 with COPD and 240 with asthma) and 84 healthy individuals for training. Physiological and IOS parameters were combined into six feature combinations. The classification algorithms tested were logistic regression, random forest, neural network, k-nearest neighbor, and support vector machine. The optimal feature combination for identifying individuals without pulmonary obstruction, with asthma, or with COPD included 15 IOS and physiological features. The neural network classifier achieved the highest accuracy (0.786). For discriminating between healthy and unhealthy individuals, two combinations of twenty-three features performed best in the neural network algorithm (accuracy of 0.929). When distinguishing COPD from asthma, the best combination included 15 features and the neural network algorithm achieved an accuracy of 0.854. This study provides compelling technical evidence and clinical justifications for advancing IOS data-driven models to aid in COPD and asthma management.

Impulse oscillometry indices in relation to respiratory symptoms and spirometry in the Swedish Cardiopulmonary Bioimage Study

Background

Impulse oscillometry (IOS) is sensitive in detecting lung function impairment. In small studies, impaired IOS relates better to respiratory symptoms than spirometry. We studied how IOS related to spirometry and respiratory symptoms in a large population of individuals (n=10 360) in a cross-sectional analysis.

Methods

Normal values for IOS and spirometry were defined in healthy, never-smoking individuals, aged 50-64 years, from the Swedish CArdioPulmonary bioImage Study (n=3664 for IOS and 3608 for spirometry). For IOS, abnormal values for resistance at 5 Hz (R5) and at 20 Hz and area of reactance were defined using the 95th percentile. Abnormal reactance at 5 Hz for IOS and abnormal conventional spirometry indices (forced expiratory volume in 1 s (FEV1), forced and slow vital capacity and their ratios) were defined using the 5th percentile.

Results

Abnormal IOS parameters were found in 16% of individuals and were associated with increased odds ratios for nearly all respiratory symptoms when adjusted for age, gender and smoking. In individuals with normal spirometry, abnormal IOS resistance was related to cough and dyspnoea, while abnormal reactance was related to wheeze. In these individuals, the combination of abnormal R5 with abnormal reactance resulted in approximately two-fold higher likelihood for having cough, chronic bronchitis and dyspnoea, even when further adjusting for FEV1, expressed as % predicted.

Conclusions

Abnormal IOS is related to increased respiratory burden in middle-aged individuals with normal spirometry, especially when resistance and reactance parameters are combined. The different relationships between respiratory symptoms and reactance and resistance warrant further research.

Interpreting lung oscillometry results: Z-scores or fixed cut-off values?

Instead of using % predicted values or Z-scores to define and quantify respiratory abnormality in oscillometry, fixed cut-off values will likely give more accurate discriminationhttps://bit.ly/3vVmIyE

We read with great interest the article by Lianget al. [1] wherein the authors analysed the characteristics and diagnostic performance of oscillometry in adult patients with asthma (n=781), COPD (n=688), interstitial lung disease (n=274), bronchiectasis (n=109) and upper airway obstruction (n=40), and compared these with spirometry using data collected from a registry from across 13 hospital clinics in China. The authors concluded that compared to spirometry, respiratory oscillometry was more appropriate for evaluating, rather than diagnosing, respiratory diseases. The conclusion was based on the comparison of Z-scores for area under the curve (AUC), sensitivity and specificity between forced expiratory volume in 1 s (FEV₁) (spirometry) and resistance measured at 5 Hz (R₅) (oscillometry) (AUC 0.900, sensitivity 74% and specificity 95.4% versus 0.807, 62.4% and 90.3%, respectively, for all respiratory diseases, and 0.820, 76.2% and 75.2% versus 0.788, 66.7% and 81.5%, respectively, for obstructive airways diseases). This is clearly one of the largest studies to date that has examined the diagnostic performance of oscillometry in real-life clinical practice; however, we argue that the Z-score methodology used to compare diagnostic performance of oscillometry with spirometry is not appropriate and therefore misleads the interpretation.

Reply to: Interpreting lung oscillometry results: Z-scores instead of fixed cut-off values?

Z-score is preferable to fixed cut-offs in the interpretation of respiratory oscillometry resultshttps://bit.ly/3GrKs2p

We thank S. Salvi and co-workers for their interest in our original article [1], which analysed the characteristics and diagnostic performance of respiratory oscillometry in respiratory diseases. S. Salvi and co-workers proposed that fixed cut-off values, instead of Z-scores, should be used to differentiate between healthy and disease states.

Impulse Oscillometry as a Diagnostic Test for Pulmonary Emphysema in a Clinical Setting

Body plethysmography (BP) is the standard pulmonary function test (PFT) in pulmonary emphysema diagnosis, but not all patients can cooperate to this procedure. An alternative PFT, impulse oscillometry (IOS), has not been investigated in emphysema diagnosis. We investigated the diagnostic accuracy of IOS in the diagnosis of emphysema. Eighty-eight patients from the pulmonary outpatient clinic at Lillebaelt Hospital, Vejle, Denmark, were included in this cross-sectional study. A BP and an IOS were performed in all patients. Computed tomography scan verified presence of emphysema in 20 patients. The diagnostic accuracy of BP and IOS for emphysema was evaluated with two multivariable logistic regression models: Model 1 (BP variables) and Model 2 (IOS variables). Model 1 had a cross-validated area under the ROC curve (CV-AUC) = 0.892 (95% CI: 0.654-0.943), a positive predictive value (PPV) = 59.3%, and a negative predictive value (NPV) = 95.0%. Model 2 had a CV-AUC = 0.839 (95% CI: 0.688-0.931), a PPV = 55.2%, and an NPV = 93.7%. We found no statistically significant difference between the AUC of the two models. IOS is quick and easy to perform, and it can be used as a reliable rule-out method for emphysema.

Quantitative CT Metrics for the Prediction of Therapeutic Effect in Asthma

Background: Few studies have explored the correlation between asthma medication and features on HRCT images. We aim to analyse the differences and temporal changes of lung function and airway resistance in asthma with diverse HRCT phenotypes in a short period after inhalation of budesonide/formoterol. Method: This observational study recruited 55 adult patients with varying severities of asthma. We performed detailed airway metrics measurements of chest CT scans, such as airway wall thickness (WT), wall area percentage (WA%), wall thickness percentage (T/OR), and airways with an inner perimeter of 10 mm (Pi10). The effect of lung structural features on asthma medication response was explored according to the WA% and T/OR twelve hours post-drug administration. Using multivariable regression models, we then assessed the influence of WA% on lung function. Results: WA% (p < 0.001) and T/OR (p < 0.001) significantly increased in asthma than in healthy control subjects. Compared to mild asthma, airway walls were further thickened (WA%, p = 0.023; T/OR: p = 0.029) and associated with lumen narrowing (Pi10, p = 0.055) in moderate to severe asthma. WA% and T/OR correlated well with lung function (FEV1, FVC, MMEF, and PEF) and airway resistance (R5, R20, Rp, and Fres). Regression analysis showed that MEF25 decreased with increasing age and WA% (R2 = 0.58, p < 0.001). Patients with thickened airway walls experienced a maximal increase in FVC, FEV1, and PEF at 2 h (p < 0.001) and a maximal decrease of R5, Z5, and Rp at 2 h (p < 0.001) in those with a thickened airway pattern. Conclusions: Asthma patients with different bronchial wall thicknesses exhibited variable lung function changes. Specifically, patients with thick airway wall patterns were more sensitive to inhaled budesonide in the short term.

Association between annual change in FEV1 and comorbidities or impulse oscillometry in chronic obstructive pulmonary disease

Background

Chronic obstructive pulmonary disease (COPD) is characterized by persistent respiratory symptoms and airflow limitation. The decline in forced expiratory volume in one second (FEV₁) is considered to be one of the most important outcome measures for evaluating disease progression. However, the only intervention proven to improve COPD prognosis is smoking cessation. This study therefore investigated the factors associated with annual FEV₁ decline in COPD.

Methods

This retrospective study followed up 65 patients treated for COPD for 5 years: 13 current smokers and 52 former smokers, 25 with pneumonia, 24 with asthma, 18 with cancer, and 17 with cardiovascular disease. The patients were divided into groups based on clinical cutoff parameters of the impulse oscillometry system (IOS): 11 high and 54 low R5, 8 high and 57 low R20, 21 high and 44 low R5–R20, 26 high and 39 low X5, 38 high and 27 low Fres, and 36 high and 29 low AX. We investigated whether the decline in FEV₁ was associated with comorbidities and IOS parameters.

Results

The annual change in FEV₁ over 5 years was significantly affected by smoking status (current − 66.2 mL/year vs. former − 5.7 mL/year, p < 0.01), pneumonia (with − 31.5 mL/year vs. without − 8.9 mL/year, p < 0.05), asthma (with − 30.2 mL/year vs. − 10.8 mL/year, p < 0.01), but not by cancer and cardiovascular disease. In the groups defined by IOS results, only the high AX group had significantly more annual decline in FEV₁ and %FEV₁ than the low AX group (− 22.1 vs. − 12.8, p < 0.05 and − 0.20 vs. 0.40, p < 0.05, respectively).

Conclusions

Continuing smoking as well as complications in pneumonia and asthma would be risk factors for the progression of COPD. AX might be a suitable parameter to predict the prognosis of patients with COPD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-022-01980-6.

Reference values of respiratory impedance with impulse oscillometry in healthy Chinese adults

Background

Impulse oscillometry (IO) is a non-invasive pulmonary function test for measuring respiratory impedance. Available reference equations of IO indices for adults are limited. The aim of this study was to develop reference equations of IO indices for Chinese adults.

Methods

In a multicentral, cross-sessional study of IO in Chinese adults, IO data from healthy subjects were collected from 19 general hospitals across China between 2016 and 2018. Oscillometry measurements were conducted in accordance with recommendations of the European Respiratory Society (ERS). Multiple linear regression was performed to develop sex-specific reference equations of IO indices.

Results

IO measurements were performed in 1,318 subjects, of which 567 subjects were defined as healthy individuals with acceptable IO data and were included in the final analysis. Reference equations and limits of normal [lower limit of normal (LLN)/upper limit of normal (ULN)] of IO indices were developed separately for males and females. Height but not age was shown to be the most influential contributor to IO indices. The reference equations currently used in lung function laboratories predicted higher R5 and X5. Normal ranges of R5 and X5 recommended by the equipment manufacturer were clearly different from the ULN/LLN derived from the reference equations.

Conclusions

Reference equations of IO indices for Chinese adults from a wide region were provided in this study. It is necessary to update new IO reference equations and adopt ULN/LLN as normal ranges of IO indices.

Trial Registration

This study was registered at www.clinicaltrials.gov as part of a larger study NCT03467880.

Application Value of Broadband 3-Dimensional Impulse Oscillometry in COPD

Objective

To explore the correlation of respiratory resistance in stable COPD patients measured by broadband 3-dimensional impulse oscillometry (3D-IOS) and traditional pulmonary function test (PFT). To access the diagnostic value of 3D-IOS in COPD.

Methods

A total of 107 COPD patients and 61 healthy subjects as controls were chosen to collect and statistically analyze the data of R5, R5–R20, R20, X5 and Fres measured by broadband 3D-IOS and FEV1%pred, FVC%pred and FEV1/FVC by PFTs. The diagnostic value of broadband 3D-IOS parameters in COPD was evaluated by receiver operating characteristic curve (ROC). 3D-colored images used to show dynamic changes of respiratory resistance in COPD.

Results

The COPD group showed significant increases in R5, R20, R5–R20 and Fres, and a decrease in X5 (P<0.05). With the increase of GOLD grade, R5, R5–R20 and Fres increased whereas X5 decreased (P<0.05). Compared with FEV1%pred, FVC%pred and FEV1/FVC in the COPD group, R5, R5–R20 and Fres were negatively collated (P<0.05), whereas X5 was positively collated (P<0.01). R20 was uncorrelated with the traditional lung function parameters (P>0.05). Fres and FEV1/FVC (r=−0.467), and X5 and FEV1%pred (r=0.412) showed the strongest correlation. The AUC of R5, R5–R20, X5 and Fres was 0.7808, 0.7659, 0.8947 and 0.9095, respectively. Typical 3D-colored images of COPD displayed a green pattern in the inhalation phase and yellow–red–blue graduation in the expiration phase.

Conclusion

R5, R5-R20, X5 and Fres measured by broadband 3D-IOS can reflect the change of respiratory resistance in COPD. And they have good correlation with the traditional lung function parameters (FEV1%pred, FVC%pred, FEV1/FVC). Fres has the highest diagnostic accuracy. Comprehensive analysis of R5, R5–R20, Fres and X5 helps to determine the degree of respiratory obstruction in COPD. X5 and Fres can reflect changes in lung tissue compliance. 3D-colored images can visually show the change of respiratory resistance and reactance in COPD.

Diagnostic Ability of Impulse Oscillometry in Diagnosis of Chronic Obstructive Pulmonary Disease

The diagnosis of chronic obstructive pulmonary disease (COPD) mainly relies on spirometry. Due to the complexity of spirometry, easier-to-do impulse oscillometry (IOS) has been introduced as a complementary approach to conventional pulmonary function testing. Therefore, this study aimed to assess the efficacy of the diagnostic ability of IOS for diagnosing chronic obstructive pulmonary disease (COPD). This cross-sectional study was conducted at the Lung Health Center, Chiang Mai University, Thailand, between June 2019 and January 2020. IOS and spirometry were performed with all subjects suspected of having COPD. A Receiver Operating Characteristic (ROC) curve was plotted, the area under the ROC (AuROC) and 95%CI were compared among COPD and chronic smokers. One hundred and seventeen subjects suspected of having COPD with a mean age of 68.6 ± 8.6 years old were enrolled. Of these 103 (88.0%) were male. Thirty healthy subjects were also enrolled. IOS parameters including resistance at 5 Hz (R5), resonant frequency (Fres), area under reactance (AX), heterogeneity of resistance (R5-R20), and reactance at 5 Hz (X5) demonstrated excellent overall accuracy relative to the diagnosis of COPD with an AuROC ranging from 0.80 - 0.84. The AX ≥ 8.66 cmH₂O/L represented an AuROC = 0.79, with a sensitivity of 79.1% and a specificity of 78.0% for the diagnosis of COPD. IOS is a valuable tool for use in the diagnosis of COPD. It may be used in subjects who cannot carry out the spirometric procedure.

Medical devices in allergy practice

Medical devices provide people with some health benefits in terms of diagnosis, prevention, treatment, and monitoring of disease processes. Different medical specialties use varieties of medical devices more or less specific for them. Allergology is an interdisciplinary field of medical science and teaches that allergic reactions are of systemic nature but can express themselves at the level of different organs across the life cycle of an individual. Subsequently, medical devices used in allergology could be regarded as: 1) general, servicing the integral diagnostic and management principles and features of allergology, and 2) organ specific, which are shared by organ specific disciplines like pulmonology, otorhinolaryngology, dermatology, and others. The present position paper of the World Allergy Organization (WAO) is meant to be the first integral document providing structured information on medical devices in allergology used in daily routine but also needed for sophisticated diagnostic purposes and modern disease management. It is supposed to contribute to the transformation of the health care system into integrated care pathways for interrelated comorbidities.

Small Airway Dysfunction by Impulse Oscillometry in Symptomatic Patients with Preserved Pulmonary Function

BACKGROUND

Asthma and chronic obstructive pulmonary disease are characterized by persistent airway inflammation and airflow limitation. Early detection of these diseases in patients with respiratory symptoms and preserved pulmonary function (PPF) defined by spirometry is difficult. Impulse oscillometry (IOS) may have better sensitivity than effort-dependent forced expiratory flow between 25% and 75% (FEF_25%-75%) to detect small airway dysfunction (SAD).

OBJECTIVE

To identify SAD in patients with respiratory symptoms and PPF using IOS.

METHODS

Medical records of symptomatic patients without acute or known structural lung diseases were evaluated. Patients had bronchodilator testing and IOS in the outpatient clinic between March 1 and July 31, 2017. Correlations between respiratory symptoms, spirometry, and IOS parameters were determined.

RESULTS

Among 349 patients enrolled to the study, 255 (73.1%) patients met the criteria of PPF. The IOS parameters-difference in resistance at 5 Hz and resistance at 20 Hz , reactance at 5 Hz, resonant frequency (F_res), and area under reactance curve between 5 Hz and resonant frequency-were significantly correlated with FEF_25%-75%. The cutoffs for SAD were difference in resistance at 5 Hz and resistance at 20 Hz greater than 0.07 kPa/(L/s), reactance at 5 Hz less than -0.12 kPa/(L/s), F_res greater than 14.14 Hz, and area under reactance curve between 5 Hz and resonant frequency greater than 0.44 kPa/L. Of the IOS parameters, F_res and reactance at 5 Hz had the highest sensitivity and specificity. When compared with FEF_25%-75%, F_res had greater sensitivity to detect SAD in patients with PPF. Patients with IOS-defined SAD had a significantly higher incidence of wheeze or sputum production than did those defined by FEF_25%-75%.

CONCLUSIONS

Patients with respiratory symptoms and PPF may have SAD, which can be identified with the aid of IOS in addition to spirometry.

Impedance Oscillometry: Emerging Role in the Management of Chronic Respiratory Disease

PURPOSE OF REVIEW

Chronic respiratory diseases affecting adults and children are widely prevalent, so lung function testing is imperative for diagnosis and management. Spirometry is the traditional standard measure of lung function; however, certain groups of patients are unable to provide accurate and reproducible exhalation maneuvers. Consequently, the impedance oscillometry system (IOS) has been developed as an effort, independent technique to assess airway function in children and the elderly. To better understand this emerging modality, the following review will compare IOS with spirometry, examine the function of the device, provide interpretation strategies, and discuss the evidence supporting its use in adults and children with chronic lung disease.

RECENT FINDINGS

In a population of symptomatic adults with suspected COPD, impedance oscillometry resistance measurements correlate with FEV₁ and lung resistance increases with the severity of airflow limitation. In patients with asthma, IOS is a sensitive measure of airway hyperresponsiveness and bronchodilator response. Impedance oscillometry is evolving as an alternative measure to assess lung function pediatric and adult populations.