An audit of laryngoscopes and application of a new ISO standard

P>Objective: The International Organization for Standardization (ISO) recently published an International Standard (ISO 7376:2009) which specifies illuminance levels and tests for illumination from hook-on type laryngoscopes used for intubation. A clinical study examining luminance for laryngoscopy found that 100 cd center dot m-2 was the minimum level acceptable for laryngoscopy. The purpose of this study was to measure the quality of light from laryngoscopes available for use by anesthetists in an anesthetic department and compare them to the ISO illuminance standard and published minimum acceptable luminance limits. Methods: A measuring device was constructed to support each laryngoscope in a standardized manner. For 190 reusable laryngoscopes, illuminance was measured with a lux meter at the base of this device. Eighteen clinically available laryngoscopes were then examined in detail, as a snapshot study, with multiple light recordings according to the ISO Standard. We also measured the luminance provided by each laryngoscope. Results: Only two of the 18 laryngoscopes met the minimum illuminance level of 500 lux after 10 min. Nine laryngoscopes provided a luminance < 100 cd center dot m-2, which is the reported minimum required luminance for laryngoscopy. None of the 18 laryngoscopes tested complied with the ISO standard for laryngoscope light distribution. Conclusions: Laryngoscope light should be regularly audited. Results from these audits can be used to retire or repair substandard laryngoscopes to maintain acceptable standards of laryngoscope light. Audit results produce tangible evidence that is useful when applying for capital expenditure. Light measurements are not easy to make. There needs to be a convenient device to reliably measure laryngoscope illumination.