Is forced oscillation technique the next respiratory function test of choice in childhood asthma

Feasibility and efficacy of the forced oscillation technique in patients with lysosomal storage diseases

Lysosomal storage disorders (LSDs) are a diverse group of inborn errors of metabolism, which involves the storage of macromolecules within the lysosome due to the absence of or deficiency in lysosomal enzymes. In this condition, respiratory dysfunction is the common cause of morbidity and mortality. Thus, an objective measurement examination of pulmonary function, such as spirometry, is essential for the diagnosis and management of respiratory conditions. However, spirometry requires active patient involvement. Meanwhile, the forced oscillation technique (FOT) is performed during tidal breathing and is feasible in patients who cannot perform spirometry. Thus, the current study aimed to assess the feasibility and efficacy of FOT in assessing respiratory function among patients with LSD. This study was conducted at the outpatient department of Tawam Hospital, Al-Ain, the United Arab Emirates. Patients with confirmed LSD were included in the analysis. Information on respiratory history was obtained using a standardized respiratory questionnaire, and lung function was assessed using FOT. The main outcomes were respiratory resistance (Rrs5), reactance at 5 Hz (Xrs5), and area under the reactance curve (AX). In total, 35 patients with LSD were assessed. FOT was used to evaluate 16 (47%) patients. Of the patients who were successfully assessed using FOT, 10 presented with abnormal outcomes. Hence, there was an association between lung function assessed using FOT and spirometry results in these patients. FOT can help obtain lung function measurements in patients with LSD. In this study, the patients commonly presented with abnormal FOT outcomes.

Clinical applications of forced oscillation technique (FOT) for diagnosis and management of obstructive lung diseases in children

Obstructive lung diseases such as bronchial asthma, COPD, and cystic fibrosis are a burden on many patients across the globe. Spirometry is considered the gold standard for diagnosing airflow obstruction, but it can be difficult for pediatric patients to do and requires a lot of effort. As a result, healthcare providers need new, effortless methods to diagnose airway obstructions, particularly in young children and individuals unable to perform the spirometry maneuver. The forced oscillation technique is a modern method requiring only tidal breathing combined with the application of external, source of low-amplitude oscillations to evaluate the respiratory system's response. It might be essential for identifying early respiratory changes caused by smoking, childhood asthma, and may prove more sensitive than spirometry in identifying peripheral airway disturbances or evaluating the long-term success of therapy. This review describes the methodology and the indications for the forced oscillation technique and outlines its relevance in clinical practice.

Current technological advancement in asthma care

INTRODUCTION

Asthma is a common chronic respiratory disease affecting 262 million people globally, causing half a million deaths each year. Poor asthma outcomes are frequently due to non-adherence to medication, poor engagement with asthma services, and a lack of objective diagnostic tests. In recent years, technologies have been developed to improve diagnosis, monitoring, and care.

AREAS COVERED

Technology has impacted asthma care with the potential to improve patient outcomes, reduce healthcare costs, and provide personalized management. We focus on current evidence on home diagnostics and monitoring, remote asthma reviews, and digital smart inhalers. PubMed, Ovid/Embase, Cochrane Library, Scopus and Google Scholar were searched in November 2023 with no limit by year of publication.

EXPERT OPINION

Advanced diagnostic technologies have enabled early asthma detection and personalized treatment plans. Mobile applications and digital therapeutics empower patients to manage their condition and improve adherence to treatments. Telemedicine platforms and remote monitoring devices have the potential to streamline asthma care. AI algorithms can analyze patient data and predict exacerbations in proof-of-concept studies. Technology can potentially provide precision medicine to a wider patient group in the future, but further development is essential for implementation into routine care which in itself will be a major challenge.

Errors in Metered Dose Inhaler Use Amongst Pediatric Asthma Patients

Purpose

The aim of this paper is to use easily accessible smartphones as a straightforward means for physicians to objectively check Medical Device Inhaler (MDI) technique, without the need for additional devices. Additionally, we seek to assess the frequency of inhaler technique errors and their impact on asthma control.

Patients and Methods

Thirty-two children between the ages of 5 and 18 receiving asthma therapy through MDIs were included. Three surveys were administered to all participants to gauge device history, asthma control, and patient characteristics. Patient technique was scored using inhaler audio signals recorded with a smartphone. For subjects that were able, forced oscillation technique (FOT) was performed during tidal breathing conditions before and after corticosteroid administration.

Results

81% (25/31) of participants used their MDIs incorrectly with the most common errors being rapid shallow breathing, inadequate breath-holding, and excessive actuations. Poor inhaler technique correlated with poorly controlled asthma symptoms.

Conclusion

The use of smartphone recordings can a convenient way to evaluate technique errors and could allow patients to demonstrate and refine their technique and usage without a doctor's visit, ensuring proper technique and enhancing treatment effectiveness.

Bronchiectasis Assessment in Primary Ciliary Dyskinesia: A Non-Invasive Approach Using Forced Oscillation Technique

Primary ciliary dyskinesia (PCD) is an autosomal recessive disorder that results from the dysfunction of motile cilia, which can cause chronic upper and lower respiratory infections leading to bronchiectasis. However, there is a need for additional tools to monitor the progression of bronchiectasis in PCD. The forced oscillation technique (FOT) is an effort-independent lung function test that can be used to evaluate respiratory mechanics. In this retrospective study, we aimed to describe the radiographic findings associated with respiratory impedance (resistance (Rrs) and reactance (Xrs)) measured by FOT in six adult PCD patients and one pediatric with the (RSPH4A (c.921+3_921+6delAAGT (intronic)) founder mutation. We compared the radiographic findings on a high-resolution chest computed tomography (CT) scan with the FOT results. Our findings suggest that respiratory impedance measured by FOT may be a valuable tool for detecting and monitoring the progression of bronchiectasis in PCD patients with the (RSPH4A (c.921+3_921+6delAAGT (intronic)) founder mutation. However, further research is necessary to validate these results and determine the sensitivity and specificity of bronchiectasis monitoring in PCD patients with other genetic mutations.

Influence of neonatal endotracheal tube dimensions on oscillometry-acquired reactance: a bench study

Objective.To examine the influence of the endotracheal tube (ETT) on respiratory reactance (X_rs) measured with the forced oscillation technique (FOT) and develop a correction method for it.Approach.In a bench study, the reactance of ETTs (X_tube) with different dimensions was measured on a breathing test lung in various respiratory settings.Main results.X_tubecan be accurately predicted by a fitted formula, with an R²of 0.97, with negligible effects due to changes in respiratory pattern and lung volume.Significance.The developed formula offers the ability to measure ETT-independent X_rsvalues of patients, improving the potential of FOT for lung function testing in mechanically ventilated newborns.

Differences in respiratory oscillometry measurements using mouthpiece, mouth, and nasal mask in healthy adults

Airway resistance measurements using oscillometry provide a potential alternative to spirometry in assessing airway obstruction and dynamics due to measurements taken during tidal breathing. Oscillometry typically requires participants to form a tight seal around a mouthpiece that can prove challenging for some people. To address this challenge, we conducted a prospective study to evaluate the effect of different interfaces like mouthpiece, mouth mask, and nasal mask on respiratory impedance results from oscillometry in a cohort of healthy adults. Ten healthy adults [7 females; mean age: 38.9 yr (SD ±15.5)] underwent oscillometry using each of the three interfaces. We measured resistance at 5 Hz (Rrs₅), frequency dependence of resistance at 5-20 Hz (Rrs_5-20), and reactance area (Ax). Rrs₅ was not different when using the mouthpiece compared with the mouth mask [mean 2.98 cmH₂O/L/s (SD ±0.68) vs. mean 3.2 cmH₂O/L/s (SD ±0.81); P = 0.92; 95% CI -0.82 to +0.38], respectively. Nasal mask Rrs₅ measurements were significantly higher than mouthpiece measurements (mean 7.31 cmH₂O/L/s; SD ±2.62; P < 0.01; 95%CI -6.91 to -1.75). With Ax₅, we found a mean of 4.01 cmH₂O/L (SD ±2.04) with the mouth mask compared with a mean of 4.02 cmH₂O/L (SD ±1.87; P = 1.0 95% CI -1.86 to +1.87) for the mouthpiece, however, we found a significant difference between the mouthpiece and nasal mask for Ax (mean = 10.71; SD ±7.0 H₂O/L; P = 0.04, 95% CI -12.96 to -0.43). Our findings show that oscillometry using a mouth mask may be just as effective as using a mouthpiece in assessing airway dynamics and resistance.NEW & NOTEWORTHY This is the first study to compare the use of different interfaces: mouthpiece, mouth mask, and nasal mask, for oscillometry in an adult population. We report that using a mouth mask in oscillometry may provide a valid alternative to a mouthpiece in cohorts who may struggle to form the required tight seal that is typically required in oscillometry or spirometry.

Association of Dyslipidemia and Respiratory Resistance Assessed by the Forced Oscillation Technique in Asthmatic Children

PURPOSE

This study aimed to evaluate the associations between dyslipidemia and pulmonary function parameters assessed by spirometry and the forced oscillation technique in asthmatic children.

METHODS

Asthmatic children (5-18 years old) had fasting serum lipid profiles including low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), triglyceride (TG), and high-density lipoprotein cholesterol (HDL-C) concentrations, and C-reactive protein (CRP) measured. Pulmonary function tests were assessed by spirometry and the forced oscillation technique (FOT).

RESULTS

One hundred forty-one asthmatic children were enrolled with a mean (SD) age of 11.82 (3.38) years. Eighty-eight (62.4%) children were boys, 64 (45.4%) had dyslipidemia, and 20 (14.2%) were obese. Among the children with dyslipidemia, a high LDL-C concentration (65.6%) was the most common form of dyslipidemia, followed by high TC (57.8%), high TG (35.9%), and low HDL-C concentrations (15.6%). Multivariable analysis showed significant associations between HDL-C concentrations and respiratory resistance at 5 Hz (R₅) and respiratory resistance at 20 Hz (R₂₀), and TC concentrations were modestly associated with reactance at 5 Hz (X₅), the frequency of resonance (Fres), and the area of reactance (ALX). Asthmatic children who had high LDL-C concentrations had a significantly higher expiratory phase R₅, whole breath R₂₀, and expiratory phase R₂₀ than those in children with normal LDL-C concentrations.

CONCLUSION

This study suggests an association of blood cholesterol, especially HDL-C and LDL-C, and respiratory resistance measured by the FOT, irrespective of the obesity status. An intervention for improving LDL-C and HDL-C concentrations may be beneficial on lung function parameters in asthmatic children.

CLINICAL TRIAL REGISTRATION

TCTR20200305005; date of registration: 03-04-2020 (retrospectively registered).

Oscillometry of the respiratory system: a translational opportunity not to be missed

Airway oscillometry has become the de facto standard for quality assessment of lung physiology in laboratory animals and has demonstrated its usefulness in understanding diseases of small airways. Nowadays, it is seeing extensive use in daily clinical practice and research; however, a question that remains unanswered is how well physiological findings in animals and humans correlate? Methodological and device differences are obvious between animal and human studies. However, all devices deliver an oscillated airflow test signal and output respiratory impedance. In addition, despite analysis differences, there are ways to interpret animal and human oscillometry data to allow suitable comparisons. The potential with oscillometry is its ability to reveal universal features of the respiratory system across species, making translational extrapolation likely to be predictive. This means that oscillometry can thus help determine if an animal model displays the same physiological characteristics as the human disease. Perhaps more importantly, it can also be useful to determine whether an intervention is effective as well as to understand if it affects the desired region of the respiratory system, e.g., the periphery of the lung. Finally, findings in humans can also inform preclinical scientists and give indications as to what type of physiological changes should be observed in animal models to make them relevant as models of human disease. The present article will attempt to demonstrate the potential of oscillometry in respiratory research, an area where the development of novel therapies is plagued with a failure rate higher than in other disease areas.

Non-interventional monitoring of expiratory flow limitation during experimental mechanical ventilation

Background

Expiratory flow limitation (EFL) is common among patients in the intensive care unit under mechanical ventilation (MV) and may have significant clinical consequences. In the present study, we examine the possibility of non-interventional detection of EFL during experimental MV.

Methods

Eight artificially ventilated New Zealand rabbits were included in the experiments. EFL was induced during MV by application of negative expiratory pressure (−5, −8 and −10 hPa) and detected by the negative expiratory pressure technique. Airway pressure (P_aw) and gas flow (V′) were digitally recorded and processed off-line for the evaluation of respiratory mechanics. The method is based on the computation and monitoring of instantaneous respiratory resistance R_rs(t). The resistive pressure (P_aw,res(t)) is calculated by subtracting from P_aw its elastic component and the end-expiratory pressure, as assessed by linear regression. Then, R_rs(t) is computed as the instant ratio P_aw,res(t)/V′(t).

Results

Two completely different patterns of expiratory R_rs(t) separate the cases with EFL from those without EFL. Small and random fluctuations are noticed when EFL is absent, whereas the onset of EFL is accompanied by an abrupt and continuous rise in R_rs(t), towards the end of expiration. Thus, EFL is not only detected but may also be quantified from the volume still to be expired at the time EFL occurs.

Conclusion

The proposed technique is a simple, accurate and non-interventional tool for EFL monitoring during MV.

Respiratory system resistance in expiratory flow limitation during mechanical ventilationhttps://bit.ly/34hU6Bv

Prenatal exposure to VOCs and NOx and lung function in preschoolers

BACKGROUND

Several studies have shown that exposure to air pollutants affects lung growth and development and can result in poor respiratory health in early life.

METHODS

We included a subsample of 772 Mexican preschoolers whose mothers participated in a Prenatal Omega-3 fatty acid Supplements, GRowth, And Development birth cohort study with the aim to evaluate the impact of prenatal exposure to volatile organic compounds and nitrogen oxides on lung function measured by oscillation tests. The preschoolers were followed until 5 years of age. Anthropometric measurements and forced oscillation tests were performed at 36, 48, and 60 months of age. Information on sociodemographic and health characteristics was obtained during follow up. Prenatal exposure to volatile organic compounds and nitrogen oxides was evaluated using a land use regression models and the association between them was tested using a lineal regression and longitudinal linear mixed effect models adjusting for potential confounders.

RESULTS

Overall, the mean (standard deviation) of the measurements of respiratory system resistance and respiratory system reactance at 6, 8, and 10 Hz during the follow-up period was 11.3 (2.4), 11.1 (2.4), 10.3 (2.2) and -5.2 (1.6), -4.8 (1.7), and -4.6 hPa s L^-1 (1.6), respectively. We found a significantly positive association between respiratory resistance (β_Rrs6  = 0.011; 95%CI: 0.001, 0.023) (P < .05) and prenatal exposure to nitrogen dioxide and a marginally negatively association between respiratory reactance (β_Xrs6  = -11.40 95%CI: -25.26, 1.17 and β_Xrs8  = -11.91 95%CI: -26.51, 1.43) (P = .07) and prenatal exposure to xylene.

CONCLUSION

Prenatal exposure to air pollutants was significantly associated with the alteration of lung function measured by oscillation tests in these preschool children.

[Technological Innovations in Pulmonology - Examples from Diagnostics and Therapy]

A significant proportion of the current technological developments in pneumology originate from the various areas of information technology. The spectrum ranges from smartphone apps to be used in daily life or in patient care to the use of artificial intelligence in screening and early detection of diseases. The diagnostic accuracy of apps for symptom analysis is currently very limited. Research projects are performed on the integration of symptoms and functional parameters into early detection, but also on mobility measurements as a prognostic marker in COPD. Lung cancer screening using computed tomography represents a major challenge. Here, artificial intelligence can help radiologists to cope with huge amounts of data. However, the quality of the software depends on the sufficient training of the system. Technological developments shape all fields of pneumology. For diagnostic and interventional endoscopy, they offer improved biopsy techniques and microstructural imaging. Advances in lung function measurements allow the differentiated analysis of respiratory mechanical disorders, and they could be transferred to ventilation technology. The translation of basic findings about the lung microbiome into patient care may perspectively help to better understand and treat COPD exacerbations.

Measuring airway clearance outcomes in bronchiectasis: a review

While airway clearance techniques (ACTs) are recommended for individuals with bronchiectasis, many trials have demonstrated inconsistent benefits or failed to reach their primary outcome. This review determined the most common clinical and patient-reported outcome measures used to evaluate the efficacy of ACTs in bronchiectasis. A literature search of five databases using relevant keywords and filtering for studies published in English, up until the end of August 2019, was completed. Studies included randomised controlled trials, using crossover or any other trial design, and abstracts. Studies were included where the control was placebo, no intervention, standard care, usual care or an active comparator. Adults with bronchiectasis not related to cystic fibrosis were included. Extracted data comprised study authors, design, duration, intervention, outcome measures and results. The search identified 27 published studies and one abstract. The most common clinical outcome measures were sputum volume (n=23), lung function (n=17) and pulse oximetry (n=9). The most common patient-reported outcomes were health-related quality of life (measured with St George's Respiratory Questionnaire, n=4), cough-related quality of life (measured with Leicester Cough Questionnaire, n=4) and dyspnoea (measured with Borg/modified Borg scale, n=8). Sputum volume, lung function, dyspnoea and health- and cough-related quality of life appear to be the most common clinical and patient-reported measures of airway clearance treatment efficacy.

Regression Equations of Respiratory Impedance Measured by Forced Oscillation Technique for Indian Children

OBJECTIVE

To develop regression equations of within and whole-breath respiratory impedance for Indian children aged 5 to 17 y.

METHODS

A prospective cross-sectional study was carried out in 5 to 17 y old school children of Bhopal, India. Healthy children were identified by physical examination and by administering questionnaire. The respiratory system resistance (Rrs) and reactance (Xrs) were measured at frequency of 5, 11, and 19 Hz by forced oscillation technique (FOT). The regression equations of within and whole-breath Rrs and Xrs were developed separately for boys and girls by multiple linear regression models.

RESULTS

Total 336 children were recruited and data of 320 healthy children (boys - 159), standing height of 146.1 ± 16.6 cm and body mass index of 17.2 ± 2.9 kg/m² were included in the analysis. The mean respiratory system resistance at 5 Hz (R5) and respiratory system reactance at 5 Hz (X5) of the children, irrespective of gender were 5.46 ± 2.10 cmH₂O/L/s and - 1.43 ± 0.85 cmH₂O/L/s respectively. Boys of age 16 y and older had significantly smaller Rrs as compared to girls of corresponding age (p < 0.05). The standing height of children had the highest predictive power, followed by age in the regression model. With an increase in standing height, the magnitude of both Rrs and Xrs values of children decrease. The bodyweight of children had a negligible contribution to the regression models.

CONCLUSIONS

The regression equations of within- and whole-breath Rrs and Xrs of Indian children aged 5 to 17 y are presented for the first time. The R5 values of Indian children were comparable to children of other ethnicities.

Feasibility of forced oscillatory assessment of respiratory mechanics across a laryngeal mask airway in rabbits

OBJECTIVES

The forced oscillation technique (FOT) is the method of choice for assessment of respiratory tissue mechanics. A laryngeal mask airway (LMA) is increasingly used to secure the airways in subjects under sedation or general anesthesia. While FOT is routinely performed using an endotracheal tube (ETT), the accuracy of information about airway and tissue mechanics obtained with FOT using a LMA has not been characterized. Therefore, we compared the mechanical parameters obtained with FOT using LMA and ETT in rabbits.

APPROACH

FOT was performed through a LMA at normal and reduced oscillatory amplitudes in anesthetized and mechanically ventilated rabbits (n  =  9) at positive end-expiratory pressures (PEEP) of 3 and 6 cmH₂O. These measurements were repeated at normal amplitude for the same animal using an ETT. Airway resistance, inertance, respiratory tissue damping (G) and elastance (H) were measured under each condition by FOT. The potential bias of the distensible upper airways when FOT was applied using LMA was assessed with a simulation study.

MAIN RESULTS

Values of parameters reflecting airway mechanics were significantly higher when measured using LMA at both PEEPs and oscillatory amplitudes than with ETT. Conversely, regardless of the condition, there was a correlation (r  =  0.89 both at normal and reduced amplitudes; p   <  0.0001) with good agreement (mean bias of 8.8 cmH₂O/l and 11.3 cmH₂O/l) in H, whereas G was systematically lower when obtained with LMA than with ETT at PEEP 3 (21.1%  ±  7.2% and 9.6%  ±  6.9% at normal and reduced oscillatory amplitudes, respectively) and 6 cmH₂O (15.1%  ±  8.2%, 1.6%  ±  9.4%, p   <  0.05 for all).

SIGNIFICANCE

Mechanical properties of the airways and the respiratory tissues, particularly for respiratory tissue stiffness, can be reliably assessed using LMA. However, the involvement of a longer laryngo-tracheo-bronchial pathway when using LMA should be considered for airway resistance and inertance, whereas upper airway shunting may affect the assessment of respiratory tissue damping.

Identifying pediatric lung disease: A comparison of forced oscillation technique outcomes

RATIONALE

Increasing evidence suggests the forced oscillation technique (FOT) has the capacity to provide non-invasive monitoring and diagnosis of respiratory disease in young children. However, which FOT outcomes provide the most pertinent clinical information is currently unknown. The aim of this study was to determine which FOT outcomes were most sensitive for differentiating between health and specific childhood respiratory disease.

METHODS

Respiratory impedance was measured using a commercial device (i2M, Chess Medical, Belgium) in children aged between 3 and 7 years, who had been diagnosed with either cystic fibrosis (N = 84), asthma (N = 99) or were born very preterm (N = 114). Z-scores were calculated for respiratory system resistance (Rrs) and reactance (Xrs) at 6, 8, and 10 Hz, the resonance frequency (Fres), frequency dependence (Fdep_4-24 ), and area under the reactance curve (AX). Pairwise comparisons of the area under the receiver operating characteristic (ROC) curve were used to determine the most relevant FOT variables.

RESULTS AND CONCLUSIONS

The FOT outcomes best able to discern between health and disease were Fres (P < 0.0001) in cystic fibrosis, Fres (P < 0.0001) in asthma and Xrs₈ (P < 0.0001) in children born preterm. These findings suggest the utility of specific FOT outcomes is dependent on the respiratory disease being assessed. It is hoped that a disease-specific approach to interpreting FOT data can help further refine the FOT technique to aid in the diagnosis of children with pediatric respiratory disease.

Question 3: Can we diagnose asthma in children under the age of 5 years?

The diagnosis of asthma in children under five years has been controversial due to changing concepts of what true asthma is in this age group. Previous diagnostic algorithms that used clinical indices to predict the persistence of asthma symptoms or phenotypes based on asthma triggers do not predict which children will benefit from asthma medication. A pragmatic approach to asthma diagnosis in this age group is based on identifying signs and symptoms of reversible airflow obstruction and documenting their response to asthma medication. Hopefully, this approach will provide clearer guidance to clinicians and improve asthma morbidity in these young children.

Bronchodilator responsiveness assessed by forced oscillometry and multiple breath washout techniques in preschool children

IMPORTANCE

The forced oscillation (FOT) and multiple breath washout (MBW) techniques are passive tests of lung function, and are reliable for preschool-age children. There has not been comparison testing to determine which test could more accurately differentiate between healthy controls and poorly controlled asthmatics, or differentiate a response to bronchodilator administration.

OBJECTIVE

To determine whether the MBW and/or FOT could differentiate between healthy controls and poorly controlled asthmatics, and whether the two tests could detect a response to bronchodilator administration.

METHODS

Twenty-eight healthy controls and 23 poorly controlled asthmatics 3-6 years of age participated. All subjects were administered the MBW followed by the FOT. A bronchodilator was then administered and testing was repeated. Wilcoxon Rank Sum tests were used to compare the difference between healthy controls and poorly controlled asthmatics. Wilcoxon Signed Rank tests were used to compare the pre- and post-bronchodilator values.

RESULTS

Neither MBW nor FOT differentiated healthy controls from poorly controlled asthmatics (pre-bronchodilator data); both groups had similar baseline gas mixing and airway mechanics. There was no improvement in any MBW outcomes post-bronchodilator administration. FOT detected a significant and similar degree of improvement in the airway mechanics in both groups.

INTERPRETATION

Neither MBW nor FOT differentiated between poorly controlled asthmatics (when well) and healthy controls. MBW did not detect a significant bronchodilator response in either subject group, whereas FOT detected a similar degree of bronchodilator responsiveness in both groups. This discrepancy may reflect differential changes in airway mechanics and gas mixing properties in response to bronchodilators.