Global Research Trends in Forced Oscillation Technique (FOT) and Impulse Oscillometry System (IOS): A Bibliometric Analysis of Impact and Emerging Areas

Background/Objectives: Assessing respiratory mechanics is essential for detecting early airway abnormalities. The Forced Oscillation Technique (FOT) and Impulse Oscillometry (IOS) have gained increasing recognition as complementary, effort-independent tools used in both research and clinical practice. This study aimed to provide a novel, comprehensive bibliometric overview of global research trends, impact, and emerging themes in FOT/IOS research. Methods: A systematic search of English-language articles and review articles related to FOT/IOS was conducted in the Web of Science Core Collection to identify publications related to FOT and IOS. Data were analyzed using VOSviewer, Microsoft Excel, and Biblioshiny to examine publication trends, citation patterns, collaboration networks, keyword co-occurrence, and thematic evolution. In addition, manual data extraction was performed for the top 100 most-cited papers to describe their methodological, population, and technical characteristics. Results: A total of 1072 studies published between 1976 and 2025 were included after screening. Research activity increased markedly after 2005, peaking in 2022 and reflecting sustained growth over time. The United States and Australia were the leading contributing countries. Frequently occurring keywords, including “Asthma”, “Forced oscillation technique”, “Impulse oscillometry”, “Lung-function”, and “Spirometry”, emerged as major research themes. Thematic development over time revealed a transition from methodological and pediatric-focused themes to more clinically relevant and practical applications, highlighting the growing clinical significance of oscillometry. Conclusions: Global research on oscillometry has increased significantly over the past five decades, reflecting the growing recognition of FOT and IOS as complementary tools to conventional pulmonary function tests for small airway assessment. Future research directions include continued standardization, population-specific reference values, and the evaluation of oscillometry across diverse clinical settings.