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Sterilization Reduces Light Intensity of Laryngoscope Light Sources

Sterilization Reduces Light Intensity of Laryngoscope Light Sources

Airway Intubation Set

The invasive nature of a laryngoscope means practitioners need assurance of two things. First, the instrument must be properly sterilized; infectious diseases are transmittable via a poorly sanitized laryngoscope blade. Second, the procedure requires proper illumination for visual acuity. The old-school method of sterilization using steam will effectively decontaminate blades, but at a cost. Studies show that using steam to sterilize reusable fiberoptic laryngoscope blades reduces light intensity, making them less effective. An example of one of these studies is detailed below.

Study Method

In order to test the theory that steam sterilization reduces the illumination of reusable fiberoptic blades, Tomoki Nishiyama, MD, PhD, took six Macintosh size 3 blades and steam sterilized them 80 times at 135 degrees Celsius. After the sterilization, done 10 times per week, each blade was tested using the recommended illumination bulb provided by the manufacturer.

Dr. Nishiyama positioned the tip of the blade against the edge of the light meter sensor to determine the maximum illumination intensity. Measurements were done both before and after each sterilization procedure. The test protocol included placing new batteries into the device and verifying the charge each time. As a baseline, Dr. Nishiyama also tested three new laryngoscope blades to obtain a variance analysis. Photographs were taken at the beginning of the study and after every 10 sterilizations.

Study Results

The study results show that relying on reusable laryngoscope blades sterilized through a steam process does effectively lower the illumination of the scope. Dr. Nishiyama found the light intensity of the reusable blades was higher prior to sterilization. In fact, his study proved illumination of the reusable fiberoptic blades was actually considerably higher than that of disposable products.

Subjecting these blades to the sterilization process, however, changed the quality of the illumination. After 20 sterilizations, it was lower that what is available with disposable blades. After 80 sterilizations, the lighting was significantly reduced. The cause of the reduction in light intensity is the result of irregular lighting on the tip surface. With steam sterilization, the lighting became unstable, reducing the overall effect.

This is not the first study to look at the effect cleaning has on these reusable blades. Another researcher proved that the reusable blades were able to withstand cleaning at lower temperatures using machine washing and disinfection. The light begins to break down as the temperature rises, however. At 134 degrees Celsius, scope illumination decreased by 75 percent after 75 turns in the machine. This corresponds with Nishiyama’s study results, which showed a decrease of 50 to 60 percent after 80 steam sterilizations.

Study Conclusion

Steam sterilization is the only disinfecting method able to reliably decontaminate reusable laryngoscope blades. The same method that makes these blades safe to reuse, also makes them a less effective tool. The reusable blades deteriorate significantly after repeated exposure to high temperature steam, making them a less practical choice than single-use blades.

The reason for choosing the reusable blades, to save money on replacement supplies, does not hold up in lieu of this evidence. The blades degrade after multiple uses, losing as much as 60 percent of the illumination. Disposable laryngoscope blades offer a more stable light source that will remain effective every single time. Facilities that utilize reusable fiberoptic blades and sterilized them repeatedly would benefit from switching to single-use devices based on Dr. Nishiyama’s study.


Nishiyama, MD, PhD, Tomoki, Changes in the Light Intensity of the Fiberoptic Laryngoscope Blade by Steam Sterilization. International Anesthesia Research Society, Vol. 104, No. 4, April 2007.



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