MONITORING BODY-CORE TEMPERATURE FROM THE TRACHEA - COMPARISON BETWEEN PULMONARY-ARTERY, TYMPANIC, ESOPHAGEAL, AND RECTAL TEMPERATURES

Introduction. We designed an endotracheal tube (ETT) for acquiring bod y-core temperature from the trachea. This ETT had two temperature sens ors, one attached to the inside surface of the cuff, the other mounted on the ETT shaft underneath the cuff. The ETT was evaluated in vitro and in dogs to determine: 1) optimal position of temperature sensors a nd 2) the responsiveness, accuracy and resistance to ventilatory artif acts. Methods. In vitro. An artificial trachea assessed the response-t ime and accuracy of ETT temperature sensors to abrupt: temperature cha nges and ventilatory flow-rates. In viva. Body temperature in 5 dogs w as lowered to approximately 26 degrees C then elevated toward 39 degre es C using a heat exchanger during carotid-jugular bypass. ETT tempera ture measurements were compared simultaneously with those from the art ificial trachea (in vitro) or from the pulmonary artery, tympanic cavi ty, esophagus, and rectum of dogs using dry and humidified gas. Result s. Cuff temperature sensor responded quickly and accurately to tempera ture changes and was less prone than the tube sensor to ventilatory an d humidity artifacts. During carotid-jugular bypass, in vivo tube and cuff mean temperatures averaged 1.4 degrees C and 0.36 degrees C lower , respectively, than pulmonary artery temperatures. There were no stat istical differences (P > 0.05) between cuff temperatures and those mea sured from the pulmonary artery, tympanic cavity, esophagus, and rectu m. Heating and humidifying the inspiratory gas of dogs with a water-ba th humidifer or heat moisture exchanger (HME) had minimal effects on t he cuff temperature sensor. An in-line HME increased in vivo tube temp erature from baseline values by 1.13 +/- 0.80 degrees C, while cuff te mperature increased by 0.21 +/- 0.24 degrees C. Conclusion. The cuff o f the ETT is a reliable site for measuring body-core temperature in in tubated patients.