An assessment of the luminance and light field characteristics of used direct laryngoscopes

Purpose: To determine luminance and light field characteristics and the eff ect of residual battery potential and luminance on light colour temperature in our used Macintosh #3 and #4 fibre-light (FLB) and bulb-light (BLB) lar yngoscopes. Methods: We used a power supply to provide laryngoscopes with potentials eq uivalent to those most commonly measured in the handles in use in our OR. M easurements were made under controlled, constant, conditions using a Pentax digital spotmeter (luminance) or a Minolta Color III colour temperature me ter (light colour), Colour measurements were made while increasing the powe r source potential from 2-3 volts (v) in increments of 0.1 v. Light field m easurements were made with a mm increment ruler mounted on the base of the test fixture. Results: At 2.5 and 2.8 v respectively, the #3 FLB produced luminance value s of 23.9 +/- 11.4 and 41.7 +/- 17.2 cd.m(-2) (mean +/- SD), and the #4 FLB produced 58.6 +/- 21.4 and 90.9 +/- 32.2 cd.m(-2). Increasing potential in creased luminance values (P < 0.001) and the #4FLB produced higher luminanc e values (P < 0.001). BLB produced higher luminance values than did FLB acr oss all comparisons (P < 0.001). As potentials and luminance values decreas ed, light temperature was reduced (P < 0.001). There were no differences in light field dimensions noted in any comparison. Conclusion: Fifteen percent of the BLB did not meet the minimum luminance f or laryngoscopy of 100 cd.m(-2) 92% of the FLB did not meet that same stand ard.