Predicted Value and Interpretation of Impulse Oscillometry Lung Function Test Among Different Types of Population Model

Background: Impulse oscillometry (IOS) is an increasingly adopted method for evaluating pulmonary function due to its minimal effort requirements and sensitivity to small airway changes. While IOS offers advantages over conventional spirometry, there is substantial variability in reference values across populations, raising concerns about its diagnostic consistency. Objective: This systematic review aims to evaluate and synthesize existing literature on IOS reference values in healthy populations, with a focus on identifying demographic, methodological, and regional factors influencing these standards. Methods: A comprehensive search was conducted in PubMed, Scopus, and Web of Science for studies published between January 2018 and January 2025. The review adhered to PRISMA guidelines. Inclusion criteria consisted of peer-reviewed studies reporting IOS reference values in healthy, non-smoking individuals. Data on study design, sample characteristics, measurement devices, and reported IOS parameters (e.g., R5, R20, X5, AX) were extracted and analyzed. Study quality was assessed using an adapted version of the Newcastle-Ottawa Scale. Results: A total of 12 studies met the inclusion criteria, encompassing over 6,000 participants from diverse geographic regions, including Europe, Asia, Africa, and the Americas. The review found consistent associations between IOS parameters and anthropometric factors, particularly height and age. However, substantial differences were noted across populations, partly due to variations in ethnicity, testing equipment, and prediction equations. Many reference values were derived from predominantly Caucasian cohorts, limiting their generalizability. Some studies proposed locally developed equations, highlighting the need for context-specific standards. Conclusion: This review demonstrates that IOS reference values are not universally applicable and are influenced by a range of demographic and methodological variables. The lack of standardized global reference equations limits the clinical utility of IOS, especially in non-Western populations. Future research should focus on developing harmonized, population-specific norms and standardizing testing protocols to enhance the clinical relevance of IOS worldwide.