Integrated Relaxation Pressure and Its Diagnostic Ability May Vary According to the Conditions Used for HREM Recording

Abstract

Integrated Residual Pressure (IRP) measured under conditions alternative to supine single swallows may provide clinically useful information regarding EGJ relaxation. This study aimed to compare IRP values obtained under different situations and explore their potential clinical utility. We analyzed and compared the values of IRP obtained from healthy volunteers and patients with suspected achalasia during supine single swallows (Ssup-IRP), sitting single swallows (Ssit-IRP), supine multiple rapid swallows (Msup-IRP), and sitting multiple rapid swallows (Msit-IRP). We analyzed the HREM recordings of 40 healthy volunteers and 53 patients with suspected achalasia. The four metrics were significantly different from each other in healthy volunteers (Ssup-IRP > Msup-IRP > Ssit-IRP > Msit-IRP) and their corresponding 95th percentiles were substantially distinct (Ssup-IRP: 25.3 mmHg, Ssit-IRP: 20.9 mmHg, Msup-IRP: 15.9 mmHg, and Msit-IRP: 11.9 mm Hg, respectively). Complete agreement among the four metrics in predicting abnormal IRP was found in 39 of the 47 patients with suspected achalasia who completed the protocol. Optimal cutoffs derived from ROC curve analysis demonstrated ≥ 0.95 specificities for detection of impaired EGJ relaxation among patients with suspected achalasia. Among the eight patients with suspected achalasia with normal Ssup-IRP, five demonstrated abnormal Msit-IRP and four abnormal Ssit-IRP. Significant differences of IRP exist depending on the measurement situation, indicating that correct interpretation of IRP values requires specific cutoffs for each situation.The sensitivities of Ssit-IRP and Msit-IRP in detecting defective EGJ relaxation appear to be slightly higher than that of Ssup-IRP.

Keywords: Achalasia; Integrated relaxation pressure; Multiple rapid swallows; Sitting; Supine.