Effects of laryngoscope handle light source on the light intensity from disposable laryngoscope blades

Abstract

A bench-top study was performed to assess the effects of different laryngoscope handles on the light intensity delivered from disposable metal or plastic laryngoscope blades. The light intensity from both the handle light sources themselves and the combined handle and laryngoscope blade sets was measured using a custom-designed testing system and light meter. Five samples of each disposable blade type were tested and compared with a standard re-usable stainless steel blade using three different handle/light sources (Vital Signs LED, Heine 2.5 V Xenon and 3.5 V Xenon). The light intensity delivered by the disposable blades ranged from 790 to 3846 lux for the different handle types. Overall, the 3.5 V Heine handle delivered the highest light output (p < 0.007) in comparison with the other handles. For the disposable blades, the overall light output was significantly higher from the plastic than the metal blades (p < 0.001).

Mechanical testing of the deflection and ultimate strength of metal and plastic disposable laryngoscope blades

“…Nine different brands of disposable Macintosh (size 3) laryngoscope blades were tested, including five metal brands and four plastic brands (Table ). These blades had been previously used in our testing of illumination, 3 but none had undergone any stress loading. Five samples from each brand were tested except for one metal blade, of which four samples were used (Table ).…”

Laryngoscope brightness determined by visual inspection and during mannequin laryngoscopy

“…After institutional research ethics board approval (CDHA-RS2014-074, July 2013), a convenience sample of 35 anesthesia staff and residents (n = 25 and 10, respectively) provided written informed consent to participate. A laryngoscope brightness testing chamber 3 was employed to identify ten used laryngoscope blades with light intensities ranging from approximately 140-2,200 lux (Table). This range encompasses previously proposed minimum light intensity requirements for laryngoscopy.…”

“…This range encompasses previously proposed minimum light intensity requirements for laryngoscopy. [3][4][5] Ten baseline illumination measurements were obtained for each blade using a single new 3.5 volt rechargeable handle fitted with a xenon bulb (Heine, Herrsching, Germany) prior to assessment by study participants. Participants were blinded to the measured brightness intensity of each blade.…”

“…This is considerably greater than the 500 lux recommended by the ISO, 5 but comparable to 700 lux proposed by Baker. 4 We recommend regular quality audits of reusable laryngoscopes blades using a light meter 3 to ensure that they are sufficiently bright.…”

An analysis of patents for anesthetic laryngoscopes

“…The bulbs and batteries need to be checked on a regular basis to maintain the quality of the light produced by traditional laryngoscopes. Anesthetic laryngoscopes often use natural white light sources, such as cool white light-emitting diodes (LEDs), halogen light bulbs, or Xenon light bulbs (Milne et al, 2014). However, a combined ultraviolet and white light source has been found to act as a black light source that emits electromagnetic radiation at a wavelength of 300-450 nm.…”