IMPEDANCE PLANIMETRIC CHARACTERIZATION OF THE DISTAL ESOPHAGUS IN THEGOETTINGEN MINIPIG

Regional differences in biomechanical properties of the oesophagus wer e studied in 15 healthy Goettingen minipigs by means of impedance plan imetry. The investigation was performed during anaesthesia by stepwise pressure-induced balloon distensions with concomitant measurement of pressure and luminal cross-sectional area (CSA) in the oesophagus 5 an d 10 cm above the gastro-oesophageal junction. The circumferential wal l tension, circumferential strain and incremental elastic modulus were computed from the measurements of pressure and CSA at steady-state co nditions. Probably due to the anaesthesia, only scant peristalsis was recorded and the CSA always reached steady state during the balloon di stensions. The CSAs were highest in the distal oesophagus (P<0.001). A t the highest induced pressure, the CSAs were 605 +/- 32 and 453 +/- 2 9 mm(2) (mean +/- SEM) for the locations 5 and 10 cm from the gastro-o esophageal junction. The tension-strain distributions were non-linear and the curve obtained 5 cm above the gastro-oesophageal junction was shifted to the right when compared with the curve obtained from 10 cm above this junction. Fitting of the function tension = exp(a + b strai n) to the data gave determination coefficients higher than 0.97 and P values lower than 0.001 for both measuring points. The constant a diff ered between the two locations in the oesophagus (P<0.05). In conclusi on, the pressure-CSA and the tension-strain distributions differed bet ween the two measuring points suggesting that the elastic properties a re different.