Impedance Planimetry: An Integrated Approach for Assessing Sensory, Active, and Passive Biomechanical Properties of the Human Esophagus

Objectives: Our objective was to study the biomechanical properties and their relationships to the sensory and motor function of the esophagus, which has seldom been examined in humans. Methods: We used impedance planimetry, to study these properties. This system measures cross‐sectional area (CSA) and intraluminal pressure simultaneously and facilitates calculation of some of the biomechanical properties of the esophageal wall. We performed 15 studies in 12 healthy volunteers. In three subjects, the studies were repeated to test reproducibility. Results: Stepwisc increments in balloon pressure from 5 to 40 cm H₂O induced an increase in CSA (mean ± SD), 91 ± 27 to 469 ± 63 mm², the wall tension 27 ± 4 to 484 ± 32 mm ± cm H₂O, and the strain 0.2 ± 0.1 to 1.3 ± 0.3. The tension/strain relationship increased exponentially. The compliance did not change. The threshold for first sensation was 30 ± 11 cm H₂O (mean ± SD). In three subjects, when the balloon was distended > 40 cm H₂O, chest pain was induced at a threshold of 62 ± 3 cm H₂O. and the compliance decreased. Balloon distension induced tertiary contractions and secondary peristalsis at thresholds of 15 ± 4 cm H₂O, and 19 ± 5 cm H₂O. Repeat studies showed good correlation (r= 0.9). Conclusion: Graded balloon distension increases esophageal CSA, wall tension, and strain. When a threshold is reached, tertiary contractions and secondary peristalsis develop at pressures less than 50% of sensory threshold. At higher pressures, chest pain is induced. Impedance planimetry promises to be a simple, objective, reproducible, and comprehensive technique for evaluating the sensory, motor, and viscoelastic properties of the esophagus.