{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,11,3]],"date-time":"2026-11-03T17:09:04Z","timestamp":1793725744259,"version":"4.6.1"},"reference-count":46,"publisher":"BMJ","issue":"1","license":[{"start":{"date-parts":[[2022,10,6]],"date-time":"2022-10-06T00:00:00Z","timestamp":1665014400000},"content-version":"unspecified","delay-in-days":5,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100020290","name":"King Saud bin Abdulaziz University for Health Science","doi-asserted-by":"publisher","award":["Not applicable"],"award-info":[{"award-number":["Not applicable"]}],"id":[{"id":"10.13039\/501100020290","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Open Resp Res"],"accepted":{"date-parts":[[2022,9,17]]},"published-print":{"date-parts":[[2022,10]]},"abstract":"<jats:sec>\n                  <jats:title>Background<\/jats:title>\n                  <jats:p>Chronic obstructive pulmonary disease (COPD) is diagnosed and its severity graded by traditional spirometric parameters (forced expiratory volume in 1 s (FEV<jats:sub>1<\/jats:sub>)\/forced vital capacity (FVC) and FEV<jats:sub>1<\/jats:sub>, respectively) but these parameters are considered insensitive for identifying early pathology. Measures of small airway function, including forced expiratory flow between 25% and 75% of vital capacity (FEF<jats:sub>25-75<\/jats:sub>), may be more valuable in the earliest phases of COPD. This study aimed to determine the prevalence of low FEF<jats:sub>25-75<\/jats:sub> in ever-smokers with and without airflow limitation (AL) and to determine whether FEF<jats:sub>25-75<\/jats:sub> relates to AL severity.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Method<\/jats:title>\n                  <jats:p>A retrospective analysis of lung function data of 1458 ever-smokers suspected clinically of having COPD. Low FEF<jats:sub>25-75<\/jats:sub> was defined by z-score&lt;\u22120.8345\u2009and AL was defined by FEV<jats:sub>1<\/jats:sub>\/FVC z-scores&lt;\u22121.645. The severity of AL was evaluated using FEV<jats:sub>1<\/jats:sub> z-scores. Participants were placed into three groups: normal FEF<jats:sub>25-75<\/jats:sub>\/ no AL (normal FEF<jats:sub>25-75<\/jats:sub>\/AL\u2212); low FEF<jats:sub>25-75<\/jats:sub>\/ no AL (low FEF<jats:sub>25-75<\/jats:sub>\/AL\u2212) and low FEF<jats:sub>25-75<\/jats:sub>\/ AL (low FEF<jats:sub>25-75<\/jats:sub>\/AL+).<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Results<\/jats:title>\n                  <jats:p>Low FEF<jats:sub>25-75<\/jats:sub> was present in 99.9% of patients with AL, and 50% of those without AL. Patients in the low FEF<jats:sub>25-75<\/jats:sub>\/AL\u2212 group had lower spirometric measures (including FEV<jats:sub>1<\/jats:sub> FEF<jats:sub>25-75<\/jats:sub>\/FVC and FEV<jats:sub>3<\/jats:sub>\/FVC) than those in the normal FEF<jats:sub>25-75<\/jats:sub>\/AL\u2212 group. FEF<jats:sub>25-75<\/jats:sub> decreased with AL severity. A logistic regression model demonstrated that in the absence of AL, the presence of low FEF<jats:sub>25-75<\/jats:sub> was associated with lower FEV<jats:sub>1<\/jats:sub> and FEV<jats:sub>1<\/jats:sub>\/FVC even when smoking history was accounted for.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Conclusions<\/jats:title>\n                  <jats:p>Low FEF<jats:sub>25-75<\/jats:sub> is a physiological trait in patients with conventional spirometric AL and likely reflects early evidence of impairment in the small airways when spirometry is within the \u2018normal range\u2019. FEF<jats:sub>25-75<\/jats:sub> likely identifies a group of patients with early evidence of pathological lung damage who warrant careful monitoring and reinforced early intervention to abrogate further lung injury.<\/jats:p>\n               <\/jats:sec>","DOI":"10.1136\/bmjresp-2022-001385","type":"journal-article","created":{"date-parts":[[2022,10,6]],"date-time":"2022-10-06T07:45:37Z","timestamp":1665042337000},"page":"e001385","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":15,"title":["Small airway function measured using forced expiratory flow between 25% and 75% of vital capacity and its relationship to airflow limitation in symptomatic ever-smokers: a cross-sectional study"],"prefix":"10.1136","volume":"9","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0609-5771","authenticated-orcid":false,"given":"Nowaf Y","family":"Alobaidi","sequence":"first","affiliation":[{"name":"Birmingham Acute Care Research Group, Institute of Inflammation and Ageing, University of Birmingham, Birmingham, UK"},{"name":"Respiratory Therapy Department, College of Applied Medical Sciences, King Saud bin Abdulaziz University for Health Sciences, Alahsa, Saudi Arabia"},{"name":"King Abdullah International Medical Research Center, Alahsa, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8449-9491","authenticated-orcid":false,"given":"Mohammed","family":"Almeshari","sequence":"additional","affiliation":[{"name":"Birmingham Acute Care Research Group, Institute of Inflammation and Ageing, University of Birmingham, Birmingham, UK"},{"name":"Rehabilitation Health Sciences Department, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"James","family":"Stockley","sequence":"additional","affiliation":[{"name":"Lung Function & Sleep Department, Respiratory Medicine, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Robert Andrew","family":"Stockley","sequence":"additional","affiliation":[{"name":"Lung Function & Sleep Department, Respiratory Medicine, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3454-5482","authenticated-orcid":false,"given":"Elizabeth","family":"Sapey","sequence":"additional","affiliation":[{"name":"Birmingham Acute Care Research Group, Institute of Inflammation and Ageing, University of Birmingham College of Medical and Dental Sciences, Birmingham, UK"},{"name":"Acute Medicine, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"239","published-online":{"date-parts":[[2022,10,6]]},"reference":[{"key":"2025083110533764000_9.1.e001385.1","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa032158"},{"key":"2025083110533764000_9.1.e001385.2","doi-asserted-by":"publisher","DOI":"10.1056\/NEJM196806202782501"},{"key":"2025083110533764000_9.1.e001385.3","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa1106955"},{"key":"2025083110533764000_9.1.e001385.4","doi-asserted-by":"crossref","first-page":"591","DOI":"10.1016\/S2213-2600(18)30196-6","article-title":"Small airways disease in mild and moderate chronic obstructive pulmonary disease: a cross-sectional study","volume":"6","author":"Koo","year":"2018","journal-title":"Lancet Respir Med"},{"key":"2025083110533764000_9.1.e001385.5","unstructured":"Global Initiative for Chronic Obstructive Lung Disease . 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