American Journal of Physiology. Gastrointestinal and Liver Physiology vol:302 issue:9 pages:G909-G913
INTRODUCTION: The measurement of the physical extent of opening of the upper esophageal sphincter (UES) during bolus swallowing has to date relied on videofluoroscopy. Theoretically luminal impedance measured during bolus flow should be influenced by luminal diameter. In this study we measured the UES nadir impedance (lowest value of impedance) during bolus swallowing and assessed it as a potential correlate of UES diameter that can be determined non-radiologically. METHODS: In 40 dysphagia patients, bolus swallowing of liquids, semisolids and solids was recorded with manometry, impedance and videofluoroscopy. During swallows, the UES opening diameter (in the lateral fluoroscopic view) was measured and compared to automated impedance manometry (AIM) derived swallow function variables and UES nadir impedance as well as high resolution manometry (HRM) derived UES relaxation pressure variables. RESULTS: Of all measured variables, UES nadir impedance was the most strongly correlated with UES opening diameter. Narrower diameter correlated with higher impedance (r = -0.478, p<0.001). Patients with <10mm, 10-14mm (normal) and ≥15mm UES diameter had average UES nadir impedances of 498±39 ohms, 369±31 ohms and 293±17 ohms respectively (ANOVA p=0.005). A higher swallow risk index (SRI), indicative of poor pharyngeal swallow function, was associated with narrower UES diameter and higher UES nadir impedance during swallowing. In contrast, UES relaxation pressure variables were not significantly altered in relation to UES diameter. CONCLUSIONS: The UES nadir impedance correlates with opening diameter of the UES during bolus flow. This variable, when combined with other pharyngeal AIM analysis variables, may allow characterisation pathophysiology of swallowing dysfunction.