[Impulse oscillometry in the diagnosis of the severity of obstructive pulmonary disease]

[Recommendations on interpretive strategies for routine lung function tests]

During the annual conference of the German Respiratory Society (DGP = Deutsche Gesellschaft für Pneumologie und Beatmungsmedizin) in 2024, updated recommendations for lung function testing have been published. The original full-length version can be downloaded free of charge as pfd-paper from the journal entitled "Atemwegs- und Lungenkrankheiten, Jahrgang 50 (2024) März (111-184)". In the current recommendations new approaches have been embedded that focus on modern interpretations of lung function results, as has been proposed by the ERS (European Respiratory Society) in collaboration with the ATS (American Thoracic Society). This targets the spirometry, the whole bodyplethysmography, diffusion capacity testing, testing for bronchodilation, unspecific bronchoprovocation in addition to the reference values. Oscillometry and respiratory muscle function testing are also included in the recommendations. The current publication considers itself as a short version of the most important topics of the full-length lung function recommendations. However, reading also the full-length paper is strongly emphasised based on the understanding that lung function testing is highly important in daily clinical practice when dealing with patients suffering from respiratory diseases.

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.

Diagnostic sensitivity of impulse oscillometry in early detection of patients exposed to risk factors chronic obstructive pulmonary diseases

Background: Impulse oscillometry (IOS) is a method that does not depend on the cooperation of the patient and can detect small airway diseases with higher sensitivity than spirometry. However, the clinical application value of IOS in the screening of patients exposed to risk factors COPD and early diagnosis remains unclear. The aim of this study is to evaluate diagnostic sensitivity of IOS in the early detection of patients exposed to risk factors COPD.

Methods: A prospective cross-sectional study was conducted in Rasoul Akram Hospital, Tehran, Iran, from 2013 to 2015. 28 patients with COPD risk factors and normal spirometry participated in the study. The IOS was performed. We obtained the respiratory resistance and impedance of 5 Hz (R5) and 20 Hz (R20) and 5 Hz (Z5), respectively. The data were analyzed using SPSS version 17 using Chi-square and two independent sample t-test. Spearman correlation test was used to measure the correlation of oscillometry parameters in the diagnosis of COPD. P-value <0.05 was considered significantfor all statistical analyses.

Results: The mean patient age was 55.50±11.27 years. In this study, the sensitivity of Z5, R5, and R20 was respectively 28.5%, 25%, and 31.5%. All oscillometry parameters were significantly correlated with each other but none of the oscillometry parameters showed significant correlations with FEV1/FVC (rZ5=0.018, rR5=0.082, rR20=0.041 and PZ5=0.932, PR5=0.711, P R20=0.850). According to the results, only 9 patients (32.5%) with normal values of FEV1/FVC had abnormal values of oscillometry.

Conclusion: IOS has a low sensitivity and cannot be used in the screening of early-stage chronic obstructive pulmonary disease.

Finding the right spot: Where to measure airway parameters in patients with COPD

PURPOSE

The importance of spirometry for management of COPD was reduced in the 2017 revision of the GOLD report. CT derived airway measurements show strong correlations with lung function tests and symptoms. However, these correlations are specific to the airway localization, and currently there is no evidence for the ideal spot. Therefore, the aim of this prospective study was to systematically correlate CT derived airway measurements with extensive lung function testing.

METHODS AND MATERIALS

65 patients with diagnosed COPD underwent body plethysmography, impulse oscillometry and dose optimized qCT examination (Somatom Force, Healthineers, Germany) in inspiration and expiration. Eight airway parameters (e.g. outer diameter, maximal wall thickness) were acquired for both scans in every lobe for the third to fifth generation bronchus and correlated with the lung function tests.

RESULTS

The most significant correlations between airway parameters were found for the third generation bronchus of the upper left lobe during expiration (25 out of 48 correlation pairs, mean r = -0.39) and for the third generation bronchus of the upper right lobe during inspiration (9 out of 48 correlation pairs, mean r = -0.25). No significant correlations were for example found for the upper right lobe in expiration.

CONCLUSION

Correlations between airway parameters and lung function tests vary widely between lobes, bronchus generations and breathing states. Our work suggests that the third generation bronchus of the upper left lobe in expiration could be the preferred localization for airway quantification in future studies.

Accuracy of forced oscillation technique to assess lung function in geriatric COPD population

Introduction

Performing lung function test in geriatric patients has never been an easy task. With well-established evidence indicating impaired small airway function and air trapping in patients with geriatric COPD, utilizing forced oscillation technique (FOT) as a supplementary tool may aid in the assessment of lung function in this population.

Aims

To study the use of FOT in the assessment of airflow limitation and air trapping in geriatric COPD patients.

Study design

A cross-sectional study in a public hospital in Hong Kong. ClinicalTrials.gov ID: NCT01553812.

Methods

Geriatric patients who had spirometry-diagnosed COPD were recruited, with both FOT and plethysmography performed. “Resistance” and “reactance” FOT parameters were compared to plethysmography for the assessment of air trapping and airflow limitation.

Results

In total, 158 COPD subjects with a mean age of 71.9±0.7 years and percentage of forced expiratory volume in 1 second of 53.4±1.7 L were recruited. FOT values had a good correlation (r=0.4–0.7) to spirometric data. In general, X values (reactance) were better than R values (resistance), showing a higher correlation with spirometric data in airflow limitation (r=0.07–0.49 vs 0.61–0.67), small airway (r=0.05–0.48 vs 0.56–0.65), and lung volume (r=0.12–0.29 vs 0.43–0.49). In addition, resonance frequency (Fres) and frequency dependence (FDep) could well identify the severe type (percentage of forced expiratory volume in 1 second <50%) of COPD with high sensitivity (0.76, 0.71) and specificity (0.72, 0.64) (area under the curve: 0.8 and 0.77, respectively). Moreover, X values could stratify different severities of air trapping, while R values could not.

Conclusion

FOT may act as a simple and accurate tool in the assessment of severity of airflow limitation, small and central airway function, and air trapping in patients with geriatric COPD who have difficulties performing conventional lung function test. Moreover, reactance parameters were better than resistance parameters in correlation with air trapping.

Airway resistance and allergic sensitization in children with obstructive sleep apnea hypopnea syndrome

OBJECTIVE

The purpose of this study was to determine the airway resistance in Chinese children with obstructive sleep apnea hypopnea syndrome (OSAHS) by impulse oscilloetry (IOS) and investigate the association of the severity of OSAHS with the airway resistance and allergic sensitization.

METHOD

A total of 120 children (92 boys) treated for snoring in Beijing Children's Hospital between October 2010 and March 2011 were included in this study. Ninety-three children were diagnosed with OSAHS and 27 did not show OSAHS. Total airway resistance (R5), proximal airway resistance (R20), and peripheral airway resistance (X5) were determined by IOS. Serum levels of total IgE and allergen-specific IgE (sIgE) were also determined.

RESULTS

R5 in the OSAHS group was significantly higher than that in the non-OSAHS group (P = 0.0025), whereas R20 and X5 were similar in the two groups. R5 was positively correlated with apnea hypopnea index and obstructive apnea index and negatively correlated with the lowest arterial oxygen saturation significantly (all P < 0.05). The percentage of children with abnormal serum levels of total IgE or abnormal allergen-specific IgEs was comparable in OSAHS and non-OSAHS groups. The proportions of abnormal R5 and of abnormal serum levels of total IgE were significantly higher in children with severe OSAHS compared with children with mild or moderate OSAHS (all P < 0.05).

CONCLUSIONS

Total airway resistance was significantly increased in Children with OSAHS. Allergic sensitization might contribute to the exacerbation of existing OSAHS in children. Large scale studies are required to further validate these findings.

Neuro-fuzzy classification of asthma and chronic obstructive pulmonary disease

Background

This paper presents a system for classification of asthma and chronic obstructive pulmonary disease (COPD) based on fuzzy rules and the trained neural network.

Methods

Fuzzy rules and neural network parameters are defined according to Global Initiative for Asthma (GINA) and Global Initiative for chronic Obstructive Lung Disease (GOLD) guidelines. For neural network training more than one thousand medical reports obtained from database of the company CareFusion were used. Afterwards the system was validated on 455 patients by physicians from the Clinical Centre University of Sarajevo.

Results

Out of 170 patients with asthma, 99.41% of patients were correctly classified. In addition, 99.19% of the 248 COPD patients were correctly classified. The system was 100% successful on 37 patients with normal lung function. Sensitivity of 99.28% and specificity of 100% in asthma and COPD classification were obtained.

Conclusion

Our neuro-fuzzy system for classification of asthma and COPD uses a combination of spirometry and Impulse Oscillometry System (IOS) test results, which in the very beginning enables more accurate classification.

Additionally, using bronchodilatation and bronhoprovocation tests we get a complete patient's dynamic assessment, as opposed to the solution that provides a static assessment of the patient.

Impulse oscillometry in the diagnosis of airway resistance in chronic obstructive pulmonary disease

Spirometry is a standard lung function test for diagnosis and staging of chronic obstructive pulmonary disease (COPD). Impulse oscillometry (IOS) can be complementary to spirometry, especially in patients at advanced age and with physical or mental disorders who cannot be diagnosed through spirometry. The aim of this study was to compare IOS and spirometry in the assessment of airway obstruction in COPD. The study was conducted in 112 stable COPD patients, including 29 females and 83 males of the mean age of 69±11 years. The oscillometric evaluation included total (R5), peripheral (R5-R20), and negative reactance (X5), which were compared with the predicted forced expiratory volume in 1 s (FEV1%pred). The findings show a significantly negative correlation between FEV1%pred and the R5, R5-R20, and X5. COPD patients had increased R5, R5-R20, and X5. The severity of bronchial obstruction found by impulse oscillometry correlated well the spirometric assessment. IOS is a simple to perform test that may be helpful for functional examination of COPD patients.

Assessing and accessing the small airways; implications for asthma management

Despite the wealth of experience in the management of asthma, the disease remains inadequately controlled in some patients, who face long-term respiratory impairment and disability. The disease has been characterised as an inflammatory condition affecting first the larger airways and eventually the smaller airways, but there is evidence that peripheral airway involvement defines a particular and more severe phenotype of asthma. For this reason, assessing functional and biological parameters reflective of small airways involvement is important prognostically. No assessment method is universally and directly representative of peripheral airway function, but the traditional spirometric tests, including vital capacity, residual volume and forced vital capacity, are somewhat correlated with this function; useful methods for further assessment include the single-breath nitrogen wash-out test, impulse oscillometry, nitrous oxide and exhaled breath concentrate measurements, as well as computed tomography to reflect air trapping and response to treatment. Formulation advancements have made for easier treatment access to the smaller airways, with the new extrafine formulations resulting in better asthma control compared with non-extrafine formulations.

Spirometry and impulse oscillometry (IOS) for detection of respiratory abnormalities in metropolitan firefighters

BACKGROUND AND OBJECTIVE

As firefighters are at increased risk of adverse health effects, periodic examination of their respiratory health is important. The objective of this study was to establish whether the use of impulse oscillometry (IOS) reveals respiratory abnormalities in metropolitan firefighters that go undetected during routine respiratory health screening by spirometry and assessment of respiratory symptoms.

METHODS

This was a cross-sectional analysis of spirometry, IOS and questionnaire data from 488 male firefighters. Abnormal spirometry was defined as FEV(1), FEV(1)/FVC and/or FEF(50) below the lower limit of normal. Abnormal IOS was defined as resistance at 5 Hz (R5), frequency dependence of resistance (DeltaR5-R20) and/or reactance area (AX) above the upper limit of normal. Respiratory symptoms, smoking history, exposures and medical history were assessed. Data were analysed using logistic and linear regression models.

RESULTS

The mean age of the firefighters was 43.8 (SD 8.4) years. There were 123 (25%) former smokers and 50 (10%) current smokers. Abnormal spirometry was detected in 12%, abnormal IOS in 9% and respiratory symptoms in 20% of firefighters. Current smoking was associated with all IOS parameters (OR for R5 = 3.1, OR for DeltaR5-R20 = 7.7, OR for AX = 4.3), and with FEF(50) (OR = 9.1), chronic productive cough (OR = 4.0) and breathlessness (OR = 5.4) (P < 0.05 for all). Exposure during firefighting duties was associated with chronic productive cough (OR = 2.6), but not with spirometry or IOS parameters. Interaction terms in the linear regression models indicated associations between smoking and DeltaR5-R20, and also between smoking and AX, in the lowest and second lowest quartiles of spirometry parameters.

CONCLUSIONS

Application of IOS for the assessment of respiratory health in firefighters identified airways dysfunction in some individuals, even when spirometry values were within the normal range and there were no respiratory symptoms.