Biomechanical wall properties in the isolated perfused porcine duodenum: an experimental study using impedance planimetry

The aims were to investigate duodenal biomechanical wall properties and properties of the ascending peristaltic reflex using impedance planimetry in the isolated perfused porcine duodenum. Stepwise inflation from 0.5 to 3.0 kPa of an intraluminal duodenal balloon, in which the pressure and balloon cross‐sectional area (Bcsa) were measured simultaneously, provided the distension stimulus. The biomechanical wall parameters were calculated from these measurements. In‐vitro test of the measurement system demonstrated that it was sufficient for biomechanical studies. Balloon inflation induced a phase of rapid distension followed approximately after 2–6 s by a phase of slow Bcsa increase. In non‐relaxed segments, contractile activity was recorded both proximal to and at the site of distension. This activity started immediately after inflation and it usually disappeared within 20 s. Bcsa always reached equilibrium within the 2‐min inflation period. The circumferential wall tension and the pressure elastic modulus increased from 4.4 (3.9–4.7) kPa mm and 3.0 (2.4–3.6) kPa at low balloon pressures to 36.5 (33.3–39.3) kPa mm and 26.1 (20.7–32.8) kPa at a balloon pressure of 3 kPa. During muscle relaxation, the duodenum showed a viscoelastic behaviour with an immediate quick phase of Bcsa increase followed by a slow viscous phase. The latter fitted best with the mono‐exponential function f(x) =αx (1–eβt). The model provides the opportunity for studying duodenal biomechanical wall properties in an intact organ model. The behaviour of the present duodenal model is compatible with a Maxwell model.