Monitoring body-cors temperature from the trachea: Comparison between pulmonary artery,tympanic, esophageal,and rectal temperatures

Introduction. We designed an endotracheal tube (ETT) for acquiring body-tore temperature from the trachea. This ETT had two temperature sensors, one attached to the inside surface of the cuff, the other mounted on the ETT shaft underneath the cuff. The ETT was evaluatedin vitro and in dogs to determine: 1) optimal position of temperature sensors and 2) the responsiveness, accuracy, and resistance to ventilatory artifacts.Methods.In vitro. An artificial trachea assessed the response-time and accuracy of ETT temperature sensors to abrupt temperature changes and ventilatory flow-rates.In vivo. Body temperature in 5 dogs was lowered to approximately 26°C then elevated toward 39°C using a heat exchanger during carotid jugular bypass. ETT temperature measurements were compared simultaneously with those from the artificial trachea (in vitro) or from the pulmonary artery, tympanic cavity, esophagus, and rectum of dogs using dry and humidified gas.Results. Cuff temperature sensor responded quickly and accurately to temperature changes and was less prone than the tube sensor to ventilatory and humidity artifacts. During carotid-jugular bypass,in vivo tube and cuff mean temperatures averaged 1.4°C and 0.36°C lower, respectively, than pulmonary artery temperatures. There were no statistical differentes (P > 0.05) between cuff temperatures and those measured from the pulmonary artery, tympanic cavity, esophagus, and rectum. Heating and humidifying the inspiratory gas of dogs with a water-bath humidifer or heat moisture exchanger (HME) had minimal effects on the cuff temperature sensor. An in-line HME increasedin vivo tube temperature from baseline values by 1.13 ± 0.80 °C, while cuff temperature increased by 0.21 ±0.24°C.Conclusion. The cuff of the ETT is a reliable site for measuring body-tore temperature in intubated patients.