Airwaves Oscillometry

 Additional Research

The Relevance of Small Airway Dysfunction in Asthma with Nocturnal Symptoms. Abdo M, etal; the ALLIANCE study group. J Asthma Allergy  2021 Jul 13;14:897-905.

Rationale: Small airway dysfunction (SAD) is a frequent feature of asthma that has been linked to disease severity and poor symptom control. However, little is known about the role of SAD in nocturnal asthma.

Objective: To study the association between the severity of SAD and frequency of nocturnal symptoms compared to conventional lung function testing.

Methods: We assessed the frequency of self-reported nocturnal symptoms through the asthma control test. We studied the impact of nocturnal asthma using the Asthma Quality of Life Questionnaire (AQLQ) and the Multidimensional Fatigue Inventory (MFI-20). We assessed the lung function using spirometry, body plethysmography, impulse oscillometry, single and multiple inert gas washout and measured markers of T2-inflammation (blood and sputum eosinophils; fractional exhaled nitric oxide (FeNo)). We stratified the patients according to the presence and frequency of nocturnal asthma.

Results: A total of 166 asthma patients were enrolled in the analysis. 87 patients (52%) reported to have nocturnal symptoms at least once in the last 4 weeks. The odds ratio of nocturnal asthma correlated with the severity of all non-spirometric measures of SAD, yet neither with airflow obstruction (FEV1 and FEV/FVC) nor with large airway resistance (R20). Patients with frequent nocturnal asthma (n = 29) had a numerical increase of T2 markers and more severe SAD, as indicated by all non-spirometric measures of SAD (all p-values <0.05), worse overall asthma control, increased fatigue and reduced quality of life (all p-values <0.01) compared to patients with infrequent nocturnal asthma (n=58) or patients without nocturnal asthma (n=79). We identified 63 patients without airflow obstruction, nearly 43% of them (n=27) had nocturnal asthma. In this subgroup, only markers of air trapping and ventilation heterogeneity were significantly elevated and correlated with the frequency of nocturnal symptoms: LCI (Spearman's coefficient =-0.42, p<0.001), RV% (-0.32, p= 0.02).

Conclusion: SAD is closely associated to asthma with nocturnal symptoms. Spirometry might underestimate the broad spectrum of distal lung function impairments in this population of patients.

 

Current place of impulse oscillometry in the assessment of pulmonary diseases. Bednarek M, etal. Respir Med. 2020 Aug-Sep;170: 105952.   

        In 1956, a diagnostic tool using the forced oscillation  technique (FOT) was developed to examine respiratory functions. A modification of this method is  impulse oscillometry (IOS). In the latter, a loudspeaker delivers to the respiratory system a regular,  square pressure wave at a constant frequency from which all other individual frequencies are derived  using spectral analysis. The usefulness of IOS has been examined in relation to COPD, asthma, interstitial lung diseases, obstructive sleep apnea, and other conditions. The greatest advantage, most  notable in children, is the ability to monitor the course of a disease and to assess the response to  therapy in a simple way, i.e., minimal requirements for the cooperation of the patient, rapid and  reproducible measurements. The IOS shows similar or even higher sensitivity than spirometry in  detecting small airways dysfunction (SAD). The most well-known result observed in peripheral airways  disease (PAD) is the frequency dependence of resistance. Importantly, the abnormal resistance at a  specific frequency may occur with normal spirometry in those with early PAD. Moreover, IOS is  particularly useful if the patient cannot perform effort dependent exhalation. Despite its advantages,  the technique is still poorly found in official worldwide recommendations. Nonetheless, considering the  promising results of many studies, an increase in interest in IOS is expected, and it could soon be on  par with standard pulmonary function tests. The aim of this work is to present the basics, current  views, and various aspects of IOS. To carry out our analysis, we searched for relevant publications on  PubMed, Web of Science. Original and review articles were selected and discussed. 

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Recent Diagnosis Techniques in Pediatric Asthma: Impulse Oscillometry in Preschool  Asthma and Use of Exhaled Nitric Oxide. Review. McDowell KM. Immunol Allergy Clin North Am. 2019 May; 39(2): 205-219.

          Objective measures of lung function are important in the diagnosis and management of asthma. Spirometry, the pulmonary function test most widely used in asthma, requires respiratory maneuvers that may be difficult for preschoolers. Impulse oscillometry (IOS) is a noninvasive method of measuring lung function during tidal breathing; hence, IOS is an ideal test for use in preschool asthma. Fractional exhaled nitric oxide (FeNO) levels correspond to eosinophilic inflammation and predict responsiveness to corticosteroids. Basic concepts of IOS, methodology, and interpretation, including available normative values, and recent findings regarding FeNO are reviewed in this article.

 

Dismantling airway disease with the use of new pulmonary function indices. Zimmermann SC, etal. Eur Respir Rev. 2019 Mar 27;28(151):180122.

          We are currently limited in our abilities to diagnose, monitor disease status and manage chronic airway disease like asthma and chronic obstructive pulmonary disease (COPD). Conventional lung function measures often poorly reflect patient symptoms or are insensitive to changes, particularly in the small airways where disease may originate or manifest. Novel pulmonary function tests are becoming available which help us better characterise and understand chronic airway disease, and their translation and adoption from the research arena would potentially enable individualised patient care.In this article, we aim to describe two emerging lung function tests yielding novel pulmonary function indices, the forced oscillation technique (FOT) and multiple breath nitrogen washout (MBNW). With a particular focus on asthma and COPD, this article demonstrates how chronic airway disease mechanisms have been dismantled with the use of the FOT and MBNW. We describe their ability to assess detailed pulmonary mechanics for diagnostic and management purposes including response to bronchodilation and other treatments, relationship with symptoms, evaluation of acute exacerbations and recovery, and telemonitoring. The current limitations of both tests, as well as open questions/directions for further research, are also discussed. 

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Asthma Diagnosis: The Changing Face of Guidelines. Drake SM, etal. Pulm Ther. 2019 Dec; 5(2):103-115.

          Asthma, the most common chronic respiratory disease, is frequently misdiagnosed, and accounts for a significant proportion of healthcare expenditure. This has driven the National Institute for Health and Care Excellence (NICE) in the United Kingdom (UK) to produce recent guidance; in places, this contrasts to that of the British Thoracic Society/Scottish Intercollegiate Guideline Network (BTS/SIGN), which have been producing their own guidance since 2003. Here we review the history of asthma diagnostic guidelines, and compare and review the evidence behind them, in adults and in children. We discuss the definitions of asthma and how these drive the concepts behind diagnostic strategies. We anticipate future directions in asthma diagnosis which will take into account the concepts of personalised medicine and disease endotypes. We also consider the utility of tests in use now and in the future, in particular novel tests relating to small airway inflammation and obstruction.

 

Application of the forced oscillation technique in diagnosing and monitoring asthma in preschool children. Starczewska-Dymek L, etal. Adv Respir Med. 2019; 87(1):26-35.

          The measurement of lung function in preschool children for the diagnosis of asthma is not routinely used. The need to perform forced expiratory manoeuvres requires active cooperation and thus limits the use of spirometry in this age group. The forced oscillation technique (FOT) is a simple and noninvasive method of assessing the mechanical properties of the respiratory system during tidal breathing. It is used in young patients and requires minimal cooperation. It provides an objective assessment of the respiratory system in a group of patients in whom we have not yet had appropriate diagnostic tools. In recent years, due to the availability of new technical solutions, FOT has been increasingly used and has a chance to become a method used routinely in diagnosing and monitoring treatment in preschool children. This article presents the possibility of the clinical application of FOT in diagnosing and monitoring of early childhood asthma.

 

Lung function in a cohort of 5-year-old children born very preterm. Lombardi E, etal. Pediatr Pulmonol. 2018 Dec; 53(12):1633-1639.

Objective: We assessed lung function and respiratory health in an area-based prospective cohort of preschool children born very preterm.

Design: Lung function was measured by interrupter respiratory resistance (Rint) and forced oscillation technique (FOT) (respiratory resistance (Rrs8), reactance (Xrs8), and area under the reactance curve (AX)) at a median age of 5.2 years in a cohort of 194 children born at 22-31 weeks of gestational age (GA) in Tuscany, Italy. Respiratory symptoms and hospitalizations were also assessed.

Results: Mean (SD) lung function Z-scores were impaired in preterm children for Rint (0.72 (1.13)), Xrs8 (-0.28 (1.34)), and AX (0.29 (1.41)). However, only a relatively small proportion of children (14.5-17.4%) had values beyond the 95th centile or below the 5th. Children with bronchopulmonary dysplasia (BPD) (n = 24) had slightly but not significantly impaired lung function indices in comparison with those without BPD (n = 170). In a multivariable analysis, lower GA was associated with worse lung function indices. Fifty-five percent of children had a history of wheezing ever and 21% had been hospitalized in their lifetime because of lower respiratory infections; 31% had wheezing in the last 12 months and this was associated with increased Rrs8 (P = 0.04) and AX (P = 0.08), and with decreased Xrs8 (P = 0.04) Z-scores.

Conclusions: Irrespectively of BPD preschool children born very preterm had impaired lung function indices, as measured by Rint and FOT, and a slightly higher burden of respiratory problems than the general population. GA seems to be crucial for lung development.

 

Input oscillometry and the forced oscillation technique for assessing lung function in preschool children with asthma. Allen JL. Pediatr Investig. 2018 May 11;2(1):37-43.

Preschool children with asthma present a challenge in lung function testing, as they cannot readily cooperate with spirometry. The forced oscillation technique (FOT) measures passive pressures and flows delivered by a loudspeaker to a facemask, at frequencies much higher than those occurring physiologically. This in turn allows for rapid collection of data from a spontaneously breathing child in a timespan of seconds. However, at very rapid oscillatory flow rates, the mechanical properties opposing flows into and out of the respiratory system (collectively termed the respiratory system impedance, and comprised of elastic, resistive and inertial components) are very different from at normal breathing frequencies, with elastic properties being less important and inertial properties being more important. An understanding of how the respiratory system behaves at high frequencies is essential to understanding the physiological basis of this technique. This article presents a way to understand these oscillatory mechanics of the respiratory system. It then describes studies of the FOT in normal preschool children and in children with asthma. The technique can also measure the separate contributions of the central and peripheral airways, as well as assess for changes after bronchodilator administration. The FOT holds promise for the objective measurement of lung function in children who are too young to reliably perform spirometry.

 

Is forced oscillation technique the next respiratory function test of choice in childhood asthma. Alblooshi A, etal. World J Methodol. 2017 Dec 26;7(4):129-138.

Respiratory diseases, especially asthma, are common in children. While spirometry contributes to asthma diagnosis and management in older children, it has a limited role in younger children whom are often unable to perform forced expiratory manoeuvre. The development of novel diagnostic methods which require minimal effort, such as forced oscillation technique (FOT) is, therefore, a welcome and promising addition. FOT involves applying external, small amplitude oscillations to the respiratory system during tidal breathing. Therefore, it requires minimal effort and cooperation. The FOT has the potential to facilitate asthma diagnosis and management in pre-school children by faciliting the objective measurement of baseline lung function and airway reactivity in children unable to successfully perform spirometry. Traditionally the use of FOT was limited to specialised centres. However, the availability of commercial equipment resulted in its use both in research and in clinical practice. In this article, we review the available literature on the use of FOT in childhood asthma. The technical aspects of FOT are described followed by a discussion of its practical aspects in the clinical field including the measurement of baseline lung function and associated reference ranges, bronchodilator responsiveness and bronchial hyper-responsiveness. We also highlight the difficulties and limitations that might be encountered and future research directions.