Thermodamage, thermosensitivity and thermotolerance of normal swine oesophagus

The normal swine oesophagus was heated using an intracavity microwave radiator for 30 min at 45, 46, 47, 48 and 49 degrees C. The animals were sacrificed 48 h or 30 days later. The degree of heat injury was evaluated on an histological score system with a maximum possible damage score of 100 per cent. The acute heat injury (48 h after heating) at these temperatures was 2, 17, 40, 50 and 67 per cent respectively. The main feature of acute heat damage was degenerative necrosis or thrombosis of blood vessels at the oesophageal wall. This occurred only in one out of nine cases at 45 and 46 degrees C heating, but in seven out of nine cases at 48 and 49 degrees C. The main feature of late heat damage was fibrosis. The score of chronic damage for the above groups was 12, 23, 30, 34 and 51 per cent, respectively. When animals were preheated at 44 degrees C for 30 min and then reheated at 45-49 degrees C 4 h later, we found that preheating could provide about 2 degrees C protection. From the above data, we suggest that 45 degrees C and 30 min heating is a safe dose for normal oesophageal tissue.