TEMPERATURE DIFFERENCES IN THE OESOPHAGUS: The Effects of Intubation and Ventilation

Abstract

Oesophageal temperature variations during anaesthesia were measured in a number of groups of adult patients. It was found that in the upper half of the oesophagus intubation and controlled ventilation produced a greater degree of cooling than spontaneous breathing through a face-mask. Partial withdrawal of the endotracheal tube resulted in an upward shift of the cooled segment. Reducing the controlled tidal volume increased the mean temperature at the tip of the endotracheal tube and in the related part of the oesophagus. Temperatures in the lower fourth remained stable and it is concluded that the sensing probe should be inserted at least 24 cm below the corniculate cartilages when measuring the oesophageal temperature during anaesthesia.

Oesophageal Temperature Differences in Children

“…Using this formula to determine the depth of the probe insertion, temperatures were measured along the length of the oesophagus in 160 children anaesthetized and intubated for neurosurgical procedures. An Ellab fifteen-lead thermocouple (Whitby and Dunkin, 1968) was used in all except six neonates, in whom a single lead was inserted and then withdrawn 1 cm at a time. In these six cases, difficulty had been encountered in trying to insert the multi-lead probe the required distance, either because of its slightly greater bulk or because of the blind end that projects 2\ cm below the lowest recording ring.…”

“…In five children, none of them neonates, the formula used placed the lowest recording ring up to 2 cm inside the area of ventilatory cooling, which depends partly on the distance of insertion of the endotracheal tube (Whitby and Dunkin, 1969) and can extend below the carina. The readings obtained were 0.4-0.8 °C below the true lower oesophageal readings.…”

“…There is an area below the distal end of the endotracheal tube that is affected by ventilation and the temperature of the inspired gases. This area does not extend into the lowest quarter of the oesophagus (Stupfel and Severinghaus, 1956;Whitby andDunkin, 1963, 1969).…”

Considerations for the measurement of core, skin and mean body temperatures

“…Higher up in the oesophagus, the influence of ventilatory heat exchanges is most pronounced, so a sensor positioned here will not just have a lower absolute temperature, it will track ventilatory cycling (Nielsen and Nielsen, 1962;Whitby and Dunkin, 1969;Jaeger et al, 1980). At the level of the carina, local tissue temperatures can be 41°C cooler than within the lower third of the oesophagus (Severinghaus, 1959), particularly when breathing cold air (Jaeger et al, 1980).…”

Body Temperature and Anaesthesia

“…Readings from elsewhere in the oesophagus are influenced by the temperature of the inspired gases. A distance of 24 cm beyond the corniculate cartilages has been recommended as the minimum in adults, and a formula has been derived for use in children [84][85][86]. Alternatively, positioning at the site of loudest heart sounds, as heard through an oesophageal stethoscope, has been used.…”