Background: The Chicago classification primarily utilizes ten 5 mL liquid swallows in a supine position as the standard high-resolution esophageal manometry (HRM) protocol. HRM can be performed with varying volumes and consistencies and in an upright position. We aimed to determine the impact on HRM results by (1) position, (2) swallows of differing volume and consistency, and (3) perception of bolus passage.
Methods: HRM was performed in healthy volunteers (HV) with the following protocol of swallows: liquids 10 × 5 mL, 5 × 10 mL, and 3 × 10 mL multiple rapid swallows; applesauce 5 × 5 mL and 5 × 10 mL; and bread 5 × 2 × 2 cm and 5 × 4 × 4cm. HV rated difficulty of each swallow on a 5-point Likert scale. All HVs performed the protocol in supine position first and then in "semi-upright" (sitting 70 degrees in a bed) and "upright" (sitting in a chair) in a randomized order.
Key results: Thirty-seven HVs, median age 27 years, 64% female completed this study. Median distal contractile integral (DCI) and integrated relaxation pressure 4 s (IRP4) of 5 mL liquid swallows significantly differed (all p < 0.01) between position performed. Large volume swallows resulted in higher DCI and lower IRP4. IRP4 results were significantly increased for 2 × 2 cm pieces of bread compared to 5 mL water swallows. DCI results were higher for 2 × 2 cm pieces of bread compared to 5 mL water swallows. Distal latency was shorter in more upright positions. Among this cohort of HV, perceived difficulty of bolus passage was more likely to occur with solid boluses.
Conclusions and inferences: The volume and consistency of a swallow and the position it is performed in, significantly alter HRM metrics. Interpretation of HRM studies should incorporate different normative values which are specific to the position and bolus type.
Keywords: HRM; chicago classification; dysphagia; high resolution esophageal manometry; swallowing.
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