Light intensity and area of illumination provided by various laryngoscope blades.

Several brands of laryngoscopes and commonly used blades are evaluated for differences in direct light intensity and area of illumination. The purpose of this study was to determine which laryngoscope/blade combination provided the best lighting conditions for tracheal intubation. The direct light intensity was assessed by directing various laryngoscope/blade combinations towards a multifunction exposure meter (Flash Meter III, Minolta Corp.). Light intensity expressed in Lux was calculated using the formula: lux = 2.5 x 2 exposure index. The area of illumination provided by the laryngoscopes was assessed by taking photographs when the laryngoscope blade tips were touching a wall. The widest diameter of bright illumination in the photograph was measured in centimeters (cm). The direct light intensity ranged from 0.4-5.5 x 10(3)lux. The field of illumination ranged from 3.2 to 8.8 cm. When fitted on regular size handles, blades with incandescent bulbs provided more intense light than blades using fibreoptic light sources (P = 0.0078). For blades using incandescent light, the use of a short handle laryngoscope resulted in a decrease in light intensity (P = 0.0117). The results of this study suggest that blades using incandescent light provide greater light intensity than blades using fibreoptics.