Laryngoscopes were introduced to the medical community about a century ago. It was clear from the outset that these instruments would play a very important role in anesthesiology and critical care. Many contributed to the evolution of the laryngoscope and eventually what began as a bulky device with thick power cords, large bulbs and unreliable connections transformed into the instrument available today.

Since 1980, Propper has pioneered significant improvements towards the reliability, safety, efficacy and sterilization of laryngoscope blades. Areas involving surface condition, illumination, and anatomical design were researched to create what is currently Propper's modern and elegant family of laryngoscope blades. (See photos to the right)

Fiber-Optic Laryngoscopes
Initially, laryngoscopes were equipped with the bulb on the distal part of blades. Although this design approach provided ample illumination to the larynx and the vocal cords, it created several problems:

• bulb can be abused during intubation procedure: in the patient’s mouth it can touch tissue and fluids that can reduce the lifetime of the bulb
• bulb is abused during disassembling for blade cleaning and repair
• more bulbs are necessary: each blade is equipped with bulb;
• bulb is unprotected: it is easy to break
• fine electrical contacts constantly oxidize and must be cleaned and tested by trained personnel on a regular basis
• electrical repairs to the blade are periodically required
• insulation problems due to fluids leakage and corrosion can reduce light output or cause a short circuit

In the early 1980’s fiber-optic technology was incorporated to laryngoscope blade design with the aim of relocating the bulb and associated wiring from the blade to the handle. This approach brought about a far more reliable combination of blade and handle.

Integrated Design from Propper
The rising problem of iatrogenic infections forced hospitals to focus on cleaning, decontamination and the use of steam autoclaves for laryngoscope sterilization. The traditional fiber-optic design was not ideally suited to satisfy new infection control requirements. Since the laryngoscopes have a fiber-optic bundle housed in its own sleeve and the sleeve is attached mechanically to the blade, this creates several difficult-to-clean areas between the sleeve and the blade body. These areas could capture a patient’s saliva, blood and other biological material. This was particularly pronounced for Macintosh blades given its curved geometry. There was clearly a need to separate the bundle in such a way as to allow for its easy removal. If this is not done, great care would be necessary in cleaning these areas to ensure proper sterilization. Furthermore, the need to disassemble components meant keeping track of a variety of blades and their matching optical bundle assemblies. For anyone who has worked in the CS Department this was no small task.

In 1981 a patent was secured which elegantly resolved the difficulties faced by prior designs. All Propper blades are fully integrated by permanently encasing the fiber-optic bundle to the blade, which eliminate any traps for biological fluids. This approach provides several advantages over the separable fiber-optic blade:

• Easier to clean. Propper Integrated blades do not have any hollows and grooves where biological material can be trapped.
• No possibility of lost components of the blade in cleaning, sterilization, and assembly procedure.
• No reassembly required.
• Fiber optic bundle is protected. The Propper fiber optic bundle is permanently encased in stainless steel; the bundle is not subjected to the stress of handling the bundle assembly separately.
• Cost effectiveness. Propper’s integrated fiber optic blades require significantly less time and materials for cleaning and decontamination.

All Propper blades meet the requirements of ISO 7376-3 standard and are interchangeable with handles and blades from other manufacturers identified by the “green mark”.

Maximizing the brightness
To generate the highest brightness, several factors needed to be optimized. Propper laryngoscopes are made with the highest quality optical grade quartz fibers, densely packed into bundles as large as 5 mm in diameter. The uniformity of these fibers is selected to ensure their resistance to high temperatures and mechanical stress. The ends are optically polished and sealed with an optical grade high temperature epoxy. The source of light closely coupled to the handle end is a special xenon bulb housed in a miniature parabolic reflector. This generates substantially higher light output than traditional halogen bulbs. Combining all these factors ensured maximum brightness.

When comparing new blades from different manufacturers, it is not always easy to recognize the difference between low- and high-end quality optics. Initially, the light transmission may not be substantially different between low-end and Propper laryngoscopes. However, after several months of use and sterilization, the low-end blades will exhibit a gradual loss of illumination. This deterioration is the result of broken fibers and/or the darkening of the epoxy seals. Both effects are associated with their inability to withstand the thermal shocks of steam sterilization.

Propper handles
Two significant features of the Propper handles are a removable battery compartment and a patented switch mechanism. The importance of the removable battery compartment is evident to users who recognize the difficulties involved in sterilizing traditional handles. Prior to processing traditional handles, the parts that should not be sterilized are disassembled. These parts include bulbs, batteries and switch mechanisms. Reassembly of all these parts is then required after the sterilization. The Propper handles are constructed so that the components not requiring sterilization are fully contained in an enclosed sleeve. The sleeve is removed by unscrewing the bottom cap. This outer shell can then be sterilized using any approved steam, EO, as well as Steris® or Sterrad® procedures*. The patented switch mechanism provides a positive contact by eliminating the fragile spring contacts current in other designs. Together, these features yield much longer lifetimes and greater reliability for the Propper handle assembly.

Sterilization of Laryngoscopes
Growing interest in sterilization of laryngoscopes3 has set new and stringent sterilization requirements for the blades. It is a well-known fact that autoclaving can be very harmful to low quality blades. After repeated cycles, the plating may peel, plastic parts may melt, and fiber optics may deteriorate, reducing light transmission. As a leading company in the sterilization field, Propper has employed all of its experience to offer blades that withstand repeated sterilization procedures. The materials used to manufacture the blades and handles are carefully chosen and tested for compatibility with different cleaning and sterilization procedures. Each new type of blade is subjected to at least 500 standard steam gravity-displacement and prevaccum cycles. As a result of this rigorous testing, we have developed sterilization recommendations that most adequately fit hospital practices and current AAMI standards.

Recommendations for sterilization of Propper fiber-optic laryngoscopes:

Manual cleaning and disinfection
Wash with a soft brush. Only use an FDA approved disinfectant that is warranted by the manufacturer for use with fiber optic and stainless steel instruments. Adhere strictly to manufacturer’s instructions regarding concentration and duration. The solutions should be replaced regularly since the risk of corrosion increases with standing time and contamination of solution. A maximum immersion time of 60 minutes must not be exceeded. After disinfection, rinse with deionized water and wipe dry with a cotton cloth.

Machine cleaning and disinfection
The manufacturer’s instructions regarding duration, temperature and concentration of chemicals must be followed. Temperature should not exceed 93«C.

Ultrasonic cleaning
An ultrasonic bath (at 35 kHz) is suitable for thorough and gentle cleaning of heavily soiled and sensitive parts. Manual ultrasonic cleaning should only last long enough for the dirt to be removed, no longer than 5 minutes under normal circumstances. If detergents are added to ultrasonic baths (use non chlorine-containing agents), extra rinsing will be necessary.

Sterilization
Both the blade and outer shell of the Propper handle may be sterilized using the STERRAD® or STERIS® sterilization systems. EO gas sterilization may be used as well.

Steam sterilization: After cleaning, blades should be wrapped then sterilized in gravity displacement autoclaves at 121«C (250«F) for 20 minutes, or in pre-vacuum sterilizers at 134«C (273«F) for 4 minutes. Make certain, that laryngoscopes cool down slowly. Instruments used on patients with suspected CJD may be effectively sterilized using extended 18-minute cycle at 134«C (273«F) as recommended by the WHO4. However, it may eventually reduce light transmission. WARNING: Do not use Halogen bearing solutions (i.e. Iodophor liquids), Dry Heat or Flash sterilization.

Meeting the goal
Propper’s aim during its 69-year history has always been to provide the medical professional with safe, reliable and effective instruments. No words can convey our commitments more strongly than holding and using our laryngoscope products. The superior quality and flawless craftsmanship will be immediately evident. The large number of medical facilities throughout the world currently using Propper laryngoscope products confirms that our aim has been met time and time again.

Feel free to contact Andrew Sharavara with any questions or comments at as@proppermfg.com

References:
1. US Patent 4,556,052: Medical Instrument with Internal Light Source for Illuminating Body Cavities. 1985.
2. US Patent 5,542,905: Switch Mechanism for Use in a Laryngoscope Handle. 1996.
3. Recommended Practices for Cleaning and Processing Anesthesia Equipment. AORN Journal. November 1999.
4. World Health Organization. Infection Control Guidelines for Transmissible Spongiform Encephalopathies. Report of a WHO Consultation. Geneva, Switzerland. 23-26 March 1999.

* Sterrad is a registered trademark of Johnson&Johnson, Steris is a registered trademark of Steris Corporation.