An assessment of the luminance and light field characteristics of used direct laryngoscopes.
OBJECTIVE
To determine luminance and light field characteristics and the effect of residual battery potential and luminance on light colour temperature in our used Macintosh #3 and #4 fibre-light (FLB) and bulb-light (BLB) laryngoscopes.


METHODS
We used a power supply to provide laryngoscopes with potentials equivalent to those most commonly measured in the handles in use in our OR. Measurements were made under controlled, constant, conditions using a Pentax digital spotmeter (luminance) or a Minolta Color III colour temperature meter (light colour). Colour measurements were made while increasing the power source potential from 2-3 volts (v) in increments of 0.1 v. Light field measurements 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 values of 23.9 +/- 11.4 and 41.7 +/- 17.2 cd x m(-2) (mean +/- SD), and the #4 FLB produced 58.6 +/- 21.4 and 90.9 +/- 32.2 cd x m(-2). Increasing potential increased luminance values (P < 0.001) and the #4FLB produced higher luminance values (P < 0.001). BLB produced higher luminance values than did FLB across all comparisons (P < 0.001). As potentials and luminance values decreased, light temperature was reduced (P < 0.001). There were no differences in light field dimensions noted in any comparison.


CONCLUSIONS
Fifteen percent of the BLB did not meet the minimum luminance for laryngoscopy of 100 cd x m(-2), 92% of the FLB did not meet that same standard.
Crosby
E
E
Department of Anesthesiology and Biomedical Engineering, University of Ottawa and the Ottawa Hospital-General Site, Ontario, Canada. ecrosby@fox.nstn.ca
Cleland
M
M
D019544:Equipment Failure Analysis / Q000379:methods*; D005336:Fiber Optic Technology; D020704:Laryngoscopes; D007828:Laryngoscopy / Q000592:standards; D008029:Lighting