Application of Interrupter Resistance and Spirometry Techniques in Pediatric Pulmonary Medicine: Feasibility and Concordance in Healthy Children Under 8 Years

Background and Objectives: Pediatric pulmonary medicine relies heavily on accurate lung function assessment, yet conventional spirometry presents challenges in children due to cooperation requirements. In this context, the interrupter resistance technique (Rint), a method used in pediatric pulmonology, offers a potentially more feasible alternative for evaluating airway resistance in younger populations. This study aimed to assess the feasibility and clinical concordance between expiratory interrupter resistance (Rint(e)) and standard spirometry in healthy children under 8 years, thus contributing to the development of age-appropriate pulmonary function testing in pediatric medicine. Materials and Methods: A cross-sectional study was conducted on 200 healthy children (aged 2–8 years) in Tunisia. Pulmonary measurements were taken using a handheld device for both Rint(e) and spirometry. Feasibility rates were calculated, and correlations between the techniques were statistically analyzed. Results: Rint(e) showed significantly higher feasibility than spirometry (82.5% vs. 34.5%, p < 0.05). While older children had higher success rates with both techniques, feasibility was independent of sex, BMI, and passive smoking exposure. Moderate negative correlations were found between log Rint(e) and FEV1/FVC indices. Conclusions: In pediatric pulmonary assessment, Rint(e) demonstrated higher feasibility than spirometry among young children, making it a practical complementary method in clinical settings. However, due to only moderate correlation with spirometric indices, Rint(e) cannot yet replace spirometry in diagnostic use. Its integration into pediatric medicine may help address the gap in functional respiratory evaluation for children under the age of 8.