Fig 1. Design of Oesophageal Heat Exchanger.
The OHE consisted of silicone designated for medical use. The tube (500mm length) consisted of three integrated tubes: (a) the outlet tube supplied water from the temperature regulating device (HICO Variotherm 555, Hirtz & Co.KG, Cologne, Germany), and was connected to the inlet tube (b), which withdrew the water back to the chiller. A third tube (c) provided gastric suctioning. Purified water served as temperature regulating agent. Water temperature was assessed at the inlet (Tin) and the outlet (Tout) of the OHE. Water could be cooled down to a minimum of 3°C or warmed to a maximum of 41°C. With a feedback loop, which registered the pulmonary artery temperature (Gold standard), the water temperature was continuously adjusted to the requirements of the study protocol. Water flow rate (L/min) was measured in the forward line. Both OHE11 and OHE14.7 were inserted in uninflated (A) conditions to protect the oesophageal epithelium from desquamation and avoid unnecessary contact pressure. Immediately after initiation of cooling, OHE deflated (B) to their particular diameters. Under clinical circumstances, a blind advance of the OHE similar to a gastric tube may conceivable.