Clinical Utility of Modified Inflation–Deflation Test in Eustachian Tube Function Testing

Background/Objectives: The modified inflation–deflation test (MIDT) is a physiological test used to evaluate eustachian tube function in patients with tympanic membrane perforation. However, the clinical characteristics and diagnostic value of MIDT have not been fully established. This study aimed to investigate the characteristics of MIDT findings in normal function and patients with Eustachian tube dysfunction (ETD) classified by sonotubometry. Methods: We retrospectively assessed 192 ears of 181 patients with tympanic membrane perforation who underwent sonotubometry and MIDT. Based on sonotubometry findings, 117 ears were classified into the normal function group and 75 ears into the ETD group. The MIDT parameters of the groups, including the first opening pressure (OP1), first closing pressure (CP1), residual pressure after three openings (RP3), and pressure difference between OP1 and CP1 were compared. Correlation and receiver-operating characteristic (ROC) analyses were performed. Results: The ETD group had significantly higher OP1, CP1, and RP3 levels than the normal function group (all p < 0.001). The pressure difference between OP1 and CP1 was significantly greater for the normal function group. Failure of Eustachian tube opening was observed in 46.7% and 3.4% of ears in the ETD and normal function groups, respectively. Eustachian tube opening duration measured by sonotubometry was negatively correlated with OP1, CP1, and RP3 but positively correlated with the OP1–CP1 difference. ROC analysis identified an optimal cutoff value of 112.50 daPa for the OP1–CP1 difference, yielding a sensitivity of 92.3% and a specificity of 58.7%. Conclusions: MIDT was significantly associated with sonotubometry findings and effectively differentiated ETD from normal Eustachian tube function. These findings support the clinical utility of the MIDT as a physiological tool for assessing Eustachian tube function in patients with tympanic membrane perforation.