Insulating and cooling effects of nasal endoscope sheaths and irrigation

Heat generated at the tips of nasal endoscopes have been shown to reach temperatures high enough to cause thermal tissue injury. Endoscope sheaths have the potential to minimize the risk of thermal tissue injury. The purpose of this study was to assess the abilities of plastic and metal endoscope sheaths and sheath irrigation to insulate against dangerous scope tip temperatures.

A 4-mm 0-degree rigid nasal endoscope was used with light-emitting diode (LED) and xenon light sources (400-W LED, 300-W, and 175-W xenon) to assess scope tip temperature before and after endoscope sheath placement. Temperatures were assessed again after placement of each sheath, both before and after active saline irrigation. Scope tip temperature was measured using a noncontact infrared thermometer.

The unsheathed rigid scope tip reached a maximal temperature after 10 minutes at 100% light source intensity. The 400-W LED and 300-W xenon sources generated potentially dangerous scope tip temperatures exceeding 42°C, whereas the 175-W xenon source never generated a maximal temperature over 32.6°C. After placement of plastic and metal sheaths, mean scope tip temperatures were decreased by 2°C (4.8%) and 2.2°C (5.5%), respectively. After active saline irrigation, mean scope tip temperatures were decreased by 5.1°C (12.6%) and 5.2°C (12.8%), respectively.

With modern light sources, nasal endoscopes have the potential to reach temperatures that may cause thermal tissue injury. Endoscope sheaths lead to decreases in scope temperatures, and the effect is greater with active irrigation. In addition to improving visualization, endoscope sheaths may decrease the risk of thermal tissue injury.