S484 Characterizing Lower Esophageal Sphincter Dysfunction, Integrated Relaxation Pressure vs Distensibility Index: Who Gives a Flip?

Abstract

Introduction: Characterizing lower esophageal sphincter dysfunction is of paramount importance when classifying disorders of esophageal motility. Integrated relaxation pressure (IRP) during high resolution impedance manometry (HRIM) has traditionally been used but has been found to be imperfect. Functional lumen impedance planimetry (FLIP) has been developed to be complementary with HRIM for discerning esophageal motility disorders. The aim of this study is to evaluate the relationship between distensibility index (DI) and IRP pertaining to LES relaxation made with FLIP compared with HRIM. Methods: A retrospective review of 227 patients was performed. Patients were classified as having normal IRP (less than 15 mmHg) or abnormal IRP (greater than or equal to 15 mmHg) as measured by HRIM. The average distensibility index as measured by FLIP for patients in both groups was compared. The patient groups were then subdivided into four groups on the basis of normal or abnormal DI using each of the common standards for abnormality (less than or equal to 2.8 mm2/mmHg and less than or equal to 2.0 mm2/mmHg). Fisher’s exact analysis was completed to determine whether abnormal IRP and abnormal DI are related. Results: In patients with a normal IRP (< 15) as measured by HRIM, the mean DI was 4.02 with a standard deviation of 2.89. In patients with abnormal IRP ( ≥ 15), the mean DI was 3.03 with a standard deviation of 2.58. The difference in the mean DIs was statistically significant (p-value = 0.0234, t-test) . Table illustrates the number of patients in each IRP and DI subgroup using both cutoff standards. There was no statistically significant difference in the observed patient frequencies of any classification than would be expected by chance. Conclusion: We found that a normal IRP (< 15mmHg) is associated with higher DIs and that an abnormal IRP (≥15 mmHg) was associated with a DI ≤ 3.1. However, abnormal DI by the standards of either cutoff was not related to having abnormal IRP. Our data supports that both a high IRP and reduced DI suggest impaired LES relaxation, but a DI of less than 2.0 and 2.8 does not predict an IRP of less than 15 mmHg, suggesting some variability between the two metrics. While the chi-squared analysis approached but did not achieve statistical significance in this study, repetition with larger sample sizes in the future may yield a clearer relationship between abnormal IRP and abnormal DI. Table 1. - Fisher's Exact Test of Number of Patients Classified By Distensbility Index (DI) and Integrated Relaxation Pressure Normality and Abnormality DI < 2.8 mm2/mmHg DI ≥ 2.8 mm2/mmHg DI < 2.0 mm2/mmHg DI ≥ 2.0 mm2/mmHg IRP< 15 mmHg 16 32 11 37 IRP ≥15 mmHg 81 83 63 101 p = 0.07 p = 0.06