The Multichannel Intraoesophageal Impedance Transit Concept.

Introduction/aims The multichannel intraoesophageal impedance transit (MIIT) is a new clinical concept that is being introduced to measure the oesophageal transit during a 24-hour multichannel impedance-pH (MII-pH) study. Methods MIIT was tested in a case-control study between January 2020 and December 2023. A laboratory test was first conducted to determine the saline baseline impedance (SBI) using MII-pH catheters. SBI was later used to reference the oesophageal transit of saline during the MIIT test. In the MIIT test, patients rapidly drank 200 ml of saline within 20 seconds. The saline transit was identified by the temporal impedance changes from the oesophageal mucosal baseline impedance (MBI) to the approximate SBI level. The duration of SBI was recorded from multiple impedance sensors in the proximal, mid and distal oesophagus which form the MIIT. The regional MIIT were correlated to the Hospital Odynophagia Dysphagia Questionnaire (HODQ) scores for clinical dysphagia and severity. Regional MIIT were also compared between achalasia patients (case group) and non-achalasia patients (control group) based on high-resolution manometry (HRM) and barium swallow (BS) diagnosis. Descriptive statistics, -test and chi-squared test compared the MIIT with respect to HODQ scores, HRM and BS outcomes. Receiver operating characteristic curves with Youden's J indices determined the optimal MIIT cut-off threshold for achalasia. This research was approved by the North West Haydock NHS Health Research Authority (REC 18/NW/0120) and the Integrated Research Application System (Project ID: 333800). Results Nine hundred and eleven patients undertook the MIIT test prospectively to HRM study (females 554, mean age 50.9 years). Three hundred and thirty-three patients (36.6%) additionally underwent the BS study (the BS-HRM diagnostic concordance outcome was 83.8%). Oesophageal luminal transit of saline was identifiable during MIIT and found to be significantly lower than the MBI (-value=3.59-9.07, p<0.001). Regional MIIT increased with higher dysphagia severity (r≈0.33, p<0.001) and positive HODQ scores for clinical dysphagia (-value=6.18-6.30, p<0.001). Similarly, prolonged regional MIIT was observed in achalasia patients based on BS study diagnosis (-values: 9.86-11.2, p<0.001) and HRM study diagnosis (-values: 23-27.4, p<0.001). Patients with concordant BS-HRM study for achalasia also showed prolonged regional MIIT (-value: 13.9-16.4, p<0.001). The optimal MIIT of the distal oesophagus for achalasia diagnosis is between 4.05 minutes and 5.45 minutes (sensitivity: 73.8-100%, positive predictive values: 90.5-94.4%). MIIT thresholds for achalasia show higher concordance to the HRM study than the BS study at 4.05 minutes (χ=4.69, p<0.030). Conclusions The MIIT concept was demonstrated to be a simple and effective transit assessment that showed exceptional reliability to BS and HRM studies. The MIIT technique can be easily incorporated into the MII-pH investigation without causing additional risk or burden to patients.