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Key rationale is that oscillometry may detect bronchodilator response more sensitively than spirometry in more severe patients. Screening data from two prospective clinical trials were reviewed in patients with abnormal R5-R20/R5 ratios, with bronchodilator effects assessed after medication withdrawal and after salbutamol administration. Statistical analysis used paired tests and correlation analyses.",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":35,"@type":76,"position":81},"https://docshare.wps.com/document/healthcare/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/bronchodilator-reversibility-of-spirometry-and-oscillometry-ratios-in-severe-refractory-asthma-research-letter-review/445342/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/bronchodilator-reversibility-of-spirometry-and-oscillometry-ratios-in-severe-refractory-asthma-research-letter-review/445342.png","ImageObject",300,407,{"name":92,"@type":93},"moss~","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-10-31","2026-09-29",true,{"@type":102,"interactionType":103,"userInteractionCount":39},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"What bronchodilator response metrics were compared in this study?","Question",{"text":112,"@type":113},"The study reviewed bronchodilator effects using both spirometry measures (such as FEV1/FVC and FEF25-75/FVC) and oscillometry-derived ratios (including R5-R20/R5 and X5/AX).","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"How was reversibility assessed after medication management?",{"text":117,"@type":113},"Medications were withheld before pulmonary function tests, followed by administration of 400 μg salbutamol, then repeated oscillometry and spirometry after 20 minutes.",{"name":119,"@type":110,"acceptedAnswer":120},"What was the main relationship between oscillometry ratios and lung function measures?",{"text":121,"@type":113},"Oscillometry-derived ratios were significantly correlated with spirometry ratios, with a stronger correlation to FEF25-75/FVC than to FEV1/FVC.","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},445342,1790815928,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":133,"doc_module":4,"category_id":34,"category_name":35,"doc_title":65,"doc_description":67,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":39,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":81,"language":139,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":140,"faqs":141,"seo_title":142,"seo_description":67,"update_tm":143,"read_time":39,"preview_page_count":4},962090895452,"https://ap-avatar.wpscdn.com/davatar_a8503ba1806abce46bf441b54a3ca4cd","Clinical & Experimental Allergy  \nRESEARCH LETTER  OPEN ACCESS   \nBronchodilator Reversibility ofSpirometry and Oscillometry Ratios in Severe Refractory Asthma  \nRobert Greig  | Philipp Suter | Rory Chan | Brian Lipworth   \nScottish Centre for Respiratory Research, Ninewells Hospital and Medical School, Dundee, Scotland, UK Correspondence: Brian Lipworth ([b.j.lipworth@dundee.ac.uk](b.j.lipworth@dundee.ac.uk))  \nReceived: 6 June 2025 | Revised: 30 July 2025 | Accepted: 4 August 2025  \nFunding: Unrestricted research grants from Sanofi (EudraCT 2021-005593-25) and AstraZeneca (EudraCT No. 2019-003763-22) to the University of Dundee were provided for the original research studies. All funders had no role in this post hoc analysis, including (1) the study design; (2) the analysis and interpretation of data; (3) the writing of the report; and (4) the decision to submit the manuscript for publication.  \nKeywords: asthma | bronchodilator | oscillometry ratio | reversibility | spirometry ratio  \nTo the Editor,  \nBronchodilator response (BDR) is a key tenet in the diagnosis of asthma and is defined as an improvement in the forced expiratory volume in 1 s (FEV1) of 12% and 200 mL in response to a short acting beta agonist (SABA) such as salbutamol [1] . Oscillometry demonstrates a greater sensitivity to detect BDR when compared to spirometry in more severe asthma patients [2] . Airwave oscillometry (AOS) is an effort independent technique where a vibrating mesh creates soundwaves that are superimposed on normal tidal breathing. This allows measurement of respiratory impedance comprising components of resistance (R) and reactance (X) calculated from the relationship of pressure/flow (kPa/L/s) to frequency (Hz) . AOS also facilitates the assessment of the small airways through the heterogeneity in lung resistance between total airways at 5 Hz (R5) and the large airways at 20 Hz (R20) as R5-R20 or as peripheral lung compliance through the area under the reactance curve (AX) between 5 Hz and the resonant frequency (Fres) where the impedance equals zero. Spirometry, in comparison, measures the forced expiratory dynamic lung volumes and flow using effort dependent measurements. Oscillometry derived ratios akin to the FEV1/FVC ratio have been proposed as a method to aid the interpretation of the raw values which clinicians may not be familiar with. An R5-R20/R5 ratio ≥19% or an X5/AX ratio \u003C 15% is associated with poorer symptom control and increased exacerbations [3], and such ratios have been shown to  \nidentify significant improvements in asthma patients who were commenced on tezepelumab [4] . Here we review bronchodilator effects on both spirometry and oscillometry derived ratios.  \nThe screening data from two previous prospective clinical trials (EudraCT No. 2019-003763-22 and EudraCT 2021-005593-25) was reviewed in patients with an abnormal R5-R20/R5 ratio ≥19% who were initially identified. Prior to their pulmonary function tests, medications were withheld as follows: inhaled corticosteroid for 12 h, long-acting beta-agonists and muscarinic antagonists for 12 h/24 h depending on dosing frequency, SABA for 6 h, and montelukast for 48 h. None of the patients were taking biologics at the time of BDR assessment. Following the European Respiratory Society guidelines and manufacturer's instructions, fractional exhaled nitric oxide (FeNO) was obtained using NIOX Vero (NIOX, Oxford, UK) [5] . Spirometry (Micromedical, Chatham, UK) and AOS (Thorasys Tremoflo, Montreal, Canada) were performed in triplicate [6] . Using a pressurised metered dose inhaler with an Aerochamberspacer device (Trudell Medical, London, Canada) 400 μg of salbutamol was administered to all patients, with oscillometry and spirometry repeated after 20 min. SPSS version 29 was used for statistical analysis. Paired Student's t-tests were applied with a two-tailed alpha error of 5%. Nominal p values are quoted as either p \u003C 0.05, \u003C 0.01, or \u003C 0.001 (two tailed) . Correlations we","cbCaimNDWCTuInXG","https://ap.wps.com/l/cbCaimNDWCTuInXG","pdf",157078,"English","# Summary\n## Study design and eligibility\n## Bronchodilator assessment and testing methods\n## Baseline characteristics\n## Outcomes and statistical results\n## Correlation findings","[{\"question\":\"What bronchodilator response metrics were compared in this study?\",\"answer\":\"The study reviewed bronchodilator effects using both spirometry measures (such as FEV1/FVC and FEF25-75/FVC) and oscillometry-derived ratios (including R5-R20/R5 and X5/AX).\"},{\"question\":\"How was reversibility assessed after medication management?\",\"answer\":\"Medications were withheld before pulmonary function tests, followed by administration of 400 μg salbutamol, then repeated oscillometry and spirometry after 20 minutes.\"},{\"question\":\"What was the main relationship between oscillometry ratios and lung function measures?\",\"answer\":\"Oscillometry-derived ratios were significantly correlated with spirometry ratios, with a stronger correlation to FEF25-75/FVC than to FEV1/FVC.\"}]","Bronchodilator Reversibility of Spirometry and Oscillometry Ratios in Severe Refractory Asthma - Research Letter - review | PDF",1790711608]