Minimum and optimum light output of Macintosh size 3 laryngoscopy blades: a manikin study *

Illumination provided by laryngoscope blades varies widely. It is not known what the optimum level of illumination should be during laryngoscopy. So far, no published standards exist for light intensity provided by laryngoscopes. Fifty anaesthetists were recruited to perform laryngoscopy on a manikin with three different laryngoscopes attached to a variable voltage supply. Anaesthetists were asked to find the minimum and optimum level of light they would wish to have for intubation. This study demonstrated that anaesthetists can see the larynx at very low light levels. The optimum level was significantly greater than the minimum level. The vacuum bulb laryngoscopes provides a significant lower light output than halogen and xenon laryngoscopes. There is a large variation in illumination requirements amongst anaesthetists which may make setting standards difficult. A brighter laryngoscope, as suggested by some manufacturers, may not necessarily be a better one.