Mo1136 The Effect of Swallowing on Esophageal Basal Impedance Measurement Using 24 hr Esophageal pH Impedance Monitoring in Patients With Typical Refluxes Symptoms and No Esophagitis

Abstract

Basal esophageal impedance measurement has been reported as a good diagnostic tool for GERD. To investigate the effect of swallows, meal ingestion and sleep periods on basal esophageal impedance, patients with typical GERD symptoms and no esophagitis who underwent 24 hr esophageal impedance pH monitoring during off treatment using the VersaFlex® Z pH-impedance catheter and the Omega®, MMS system were included. The basal impedance level was the average values of 30 second-periods at the distal impedance channel, excluding periods of meal ingestion, swallows, belching and gastroesophageal refluxes. Basal impedance levels and swallow frequency were measured every 30 min during the entire recoding periods. Complete and incomplete saliva swallowing were defined as bolus entry followed by bolus clearance at all impedance recording sites and by failure bolus clearance in the two distal recording sites, respectively. Result: 23 consecutive patients with positive pH test(12F, 50 ±14 yr, BMI 26.9±5.0 kg/m2) and 23 patients with negative pH test(14F, 52±13yr, BMI 23.5±3.3 kg/m2, randomly selected from the patients who had typical reflux symptoms and negative pH test during the same study period) were included. The rate of total swallows during the 24 hr study period was similar between patients with positive and negative pH test, respectively (7.5±5.9vs.7.0±5.1 time/hr, p>0.05). The mean basal impedance during the entire study period was significant lower in patients with positive vs. negative pH test (1836±218 vs. 2866±350V , p<0.05). The basal impedance levels had a significantly positive correlation with total (r=0.26, p<0.05) and complete swallowing rate (r=0.3, p<0.05) in the whole 46 patients and both positive (total swallows r=0.38, p<0.05, complete swallows r=0.46, p<0.05) ) and negative pH groups (r = 0.38 and 0.37 respectively, p<0.05). Immediately after meal ingestion the basal impedance level and swallowing rate were significantly higher(3478±947V and 16.9±5.9 time /hr during 0-30 min after meal) compared to before meal (2022±670V and 3.4±2.1 time/hr) (p<0.05) and both basal impedance and swallowing rate gradually decreased over time (during 30-60 min were 2832±705V and 11.8±4.4 time/hr and 60-90 min after meal were 2280±712V and 6.9±3.2 time/hr). The basal impedance and swallowing rate of sleep-time period were significant lower than non sleeptime period (1625±603V vs.2286±660V, p<0.05 and 1.9±1.5 vs.7.5±6.4 time/hr, p<0.05). Conclusion: Swallow, meal ingestion, sleep and acid reflux status are significantly influence basal esophageal impedance level. The lower basal impedance during sleep and higher basal impedance after meal ingestion seems to be the effect of decrease and increase swallowing rate, respectively. This study suggest that control swallowing rate could optimize the measurement of esophageal basal impedance in shorter duration.