title: An assessment of the luminance and light field characteristics of used direct laryngoscopes.
abstract: 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.
authors.affiliation: Department of Anesthesiology and Biomedical Engineering, University of Ottawa and the Ottawa Hospital-General Site, Ontario, Canada. ecrosby@fox.nstn.ca
authors.forename: E
authors.initials: E
authors.lastname: Crosby
authors.forename: M
authors.initials: M
authors.lastname: Cleland
mesh_terms: D019544:Equipment Failure Analysis / Q000379:methods*; D005336:Fiber Optic Technology; D020704:Laryngoscopes; D007828:Laryngoscopy / Q000592:standards; D008029:Lighting