A Mechanics-Based Perspective on the Function of Human Sphincters During Functional Luminal Imaging Probe Manometry

Area of Science:

• Gastroenterology
• Biomedical Engineering
• Physiology

Background:

• The Functional Luminal Imaging Probe (FLIP) measures sphincter cross-sectional area (CSA) and pressure.
• Pressure-CSA hysteresis loops from FLIP testing offer diagnostic insights into sphincter function.
• The underlying mechanics of these pressure-CSA loops are not well understood.

Purpose of the Study:

• To consolidate and explain the mechanics of pressure-CSA loops in different human sphincters.
• To differentiate between negative slope loops (NSL) and positive slope loops (PSL).
• To link loop patterns to underlying sphincter mechanical modes.

Main Methods:

• Analysis of clinical data from FLIP testing across various sphincters.
• Developing a mechanical model to explain pressure-CSA loop formation.
• Correlating loop patterns with identified sphincter mechanical modes.

Main Results:

• Two distinct pressure-CSA loop patterns were identified: negative slope loop (NSL) and positive slope loop (PSL).
• Sphincter loop type depends on the interplay of neurogenic relaxation/external pulling and proximal muscle contraction-induced distention.
• Sphincters relying solely on neurogenic relaxation exhibit NSL, while those using both mechanisms show PSL.

Conclusions:

• This work provides a fundamental mechanical understanding of human sphincter function.
• The identified pressure-CSA loop patterns can help differentiate normal and abnormal sphincter phenotypes.
• This understanding can facilitate the development of physiomarkers based on work calculation for sphincter assessment.