We determined the feasibility, accuracy and optimal location of oesophageal core temperature measurements using the ProSeal laryngeal mask airway drain tube. Thirty normothermic anaesthetized ventilated adults (ASA 1 to 2, aged 18 to 80 years) were studied. Temperatures were recorded using a thermistor at six different locations (middle of drain tube and at 0 to 20 cm distal to the drain tube in 5 cm increments) and compared to nasopharyngeal (thermistor) and aural (infrared tympanic thermometer) reference core temperatures. The temperature probe was successfully inserted into the oesophagus in all patients at the first attempt. Oesophageal temperature increased with depth from 0 to 5 cm (35.2 v 35.9, P<0.0001) and 5 to 10 cm (35.9 v 36.3, P<0.01), but was unchanged from 10 to 15 cm (36.3 v 36.6) and 15 to 20 cm (36.6 v 36.7). Aural temperature was higher than nasopharyngeal temperature (36.8 v 36.0, P<0.0001). Aural temperature was 0.89 to 1.59°C higher than the oesophagus at 0 to 5 cm and 0.21 to 0.30°C higher than the oesophagus at 15 to 20 cm. Nasopharyngeal temperature was 0.06 to 0.76°C higher than the oesophagus at 0 to 5 cm and 0.62 to 0.84°C lower than the oesophagus at 15 to 20 cm. The lowest temperature was in the mid-point of the drain tube (34.7). We conclude that oesophageal core temperature measurement is feasible and accurate using the ProSeal laryngeal mask airway. The optimal location for the temperature probe is at 15 to 20 cm.
Oesophageal temperature probe
