Thermophysical Properties of Thermosoftening Nasotracheal Tubes
Thermosoftening treatment of polyvinyl chloride (PVC) nasotracheal tubes (NTTs) can reduce the incidence and amount of epistaxis during nasotracheal intubation. The optimal thermal setting for thermosoftening treatment of NTTs without burn injury was investigated. Two composite types of PVC NTTs were used. Following withdrawal of the PVC NTTs from a bottle of water at 45 or 60°C, the changes in the surface temperature of the NTTs were measured by infrared thermography. Hardness of the NTTs at 25, 30, 35, and 40°C was measured. The incidence of epistaxis during nasotracheal intubation using thermosoftened NTTs was evaluated retrospectively. The surface temperature of both PVC NTTs dipped in 45 and 60°C water decreased to below body temperature 30 seconds after withdrawing them from the bottles. Although thermosoftening treatment proportionally decreased the hardness of both types of NTTs, the degrees differed according to their composition. When avoiding impingement of the NTT on the posterior wall of the nasopharynx, the incidence of mild and moderate epistaxis was 2.3%. Flexibility of PVC NTTs could be obtained by thermosoftening treatment at 60°C without burn injury. Thermosoftening treatment of PVC NTTs may be useful to avoid epistaxis during nasotracheal intubation.
Using infrared thermography, the changes in the surface temperatures of the tracheal tube between the tip and 15 cm from the proximal end are measured following dipping into 60°C water for 3 minutes. Infrared thermographs show the changes in the surface temperature after 5 minutes of the Mallinckrodt Nasal RAE Tube (a) and the Portex North Polar Preformed Tube (b) after withdrawing the tube from 60°C water. Color bars represent the temperature scale ranging from 20 to 60°C.
Dots indicate the mean surface temperature between the tip and 15 cm from the distal end measured by infrared thermography (n = 5). Each polygonal line shows the sequential values of the surface temperatures of the tubes at 30-second intervals for 5 minutes after withdrawing the tube from 45 or 60°C water. (a) Mallinckrodt Nasal RAE Endotracheal Tube; (b) Ivory PVC Portex North Polar Preformed Endotracheal Tube.
The pressure force for a 1-mm reduction of the minor axis of the tracheal tube was used as the index of hardness of the tube. Blue circles and orange circles indicate Mallinckrodt Nasal RAE Endotracheal Tube and Ivory PVC Portex North Polar Preformed Endotracheal Tube, respectively. Dots and error bars indicate the means and SDs. n = 5; ** p < 0.01 versus hardness at 25°C (Bonferroni's Multiple Comparison Test).
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