Effects of battery type and age on performance of rechargeable laryngoscopes

Optimal visualization of the glottis can be crucial to successful laryngoscopy. Limited information has been published on the light intensity delivered from laryngoscopes powered by rechargeable batteries. In this study the laryngoscope light intensity delivered from 10 nickel metal hydride (NiMH), 7 nickel cadmium (NiCAD), and 2 lithium (LI) batteries with 3-5 or more years of clinical usage were tested in comparison to 5 new NiMH batteries. Each battery was charged in a new laryngoscope handle and recharging unit for 24 h before testing. Light intensity (lux) from the bulb in the laryngoscope handle was recorded at 3-min intervals under continuous loading until battery depletion. The mean times ±1 standard deviation (SD) to minimum acceptable light output (2,000 lux from the handle) were new NiMH 70 ± 1 min, 3-year-old NiMH 96 ± 2 min, 5+ year-old NiCAD 45 ± 22 min, and 5+ year-old LI 117 ± 4 min. There were significant differences in the time to minimum light intensity among all groups (p = 0.00-0.04). All new and used batteries exceeded the minimum ISO standard of light intensity for more than 10 min. These data demonstrate that rechargeable laryngoscope batteries can safely be used for several years before requiring replacement.