Optical Stylets

Optical stylets use either fiberoptic rods coupled with a focusing lens, or miniature cameras at the distal stylet connected to video imaging screens. Stylet malleability and length are features that vary among commercially available optical stylets. Clarus Medical’s Shikani Stylet and Levitan FPS Stylet are made of malleable steel surrounding fiberoptic bundles (10,000 pixels). The distal end of these devices can be shaped for different applications, including use with and without a laryngoscope, and rolling through a supraglottic airway. The Storz Bonfils Scope has a fixed shape with a long narrow axis and upward bent distal tip. It provides extraordinary visual clarity (35,000 pixels) and now is also offered in a high-resolution video version. The Video RIFL (AI Medical Devices) is a novel combination of rigid scope with an articulating tip, and uses CMOS imaging with an integrated video screen. Clarus Medical has also just recently introduced a video scope using a CMOS chip.

Levitan FPS showing bend angle for use with a laryngoscope (~35 degrees, top) vs ~65-75 degrees when used independently (or through a Berman intubating airway).
The length of an optical stylet affects its ease of handling and intended use.  Tracheal tubes from different manufacturers have certain agreed upon industrial standards regarding fittings (such as the 15 mm connectors, etc.), shaping, and markings, but not overall length.Different tube sizes, and even tubes of the same ID by different manufacturers, have different lengths.This creates the need for some sort of tube stop, or adjustment device, so that different tube lengths can be appropriately positioned over an optical stylet.  If the tracheal tube is not positioned correctly the tip of the tube will project too far over the optical end of the stylet.  The resultant view is analogous to looking through a straw–a very small optical area at the center with most of the visual field occupied by the overlying tube.  If the length of the optical stylet exceeds the tube length and is not protected by an overlying tube, then the distal tip of the stylet is exposed to secretions, blood, or other material and the image can be easily compromised.  The ideal position for a tracheal tube is just overlying (~1 cm) the distal tip of the optical stylet, so the optical element is not exposed, but also not set too far back which would compromise the field of view. Different manufacturers have created a variety of mechanical adjustable tube stop devices that connect with the standard 15mm plastic hub on a tracheal tube.  The Levitan FPS has a tube stop that is not adjustable; the tube length is adjusted by trimming the tube to fit the shortened length of this optical stylet.   Most optical stylets have lengths of approximately 35 cm or longer.  This is to accommodate the overlying tracheal tubes and an adjustable tube stop. This distance requires the operator to be somewhat afar in order to bring their eye to the eyepiece. The impact of this length on ease of use is also a function of how the device is intended to be used.  The Bonfils has a fixed, low bend angle (~40 degrees) and was designed for independent use. The operator uses their left hand to distract	Storz Bonfils optical stylet: a non-malleable fiberoptic rod with high resolution image. Distal bend angle is 40 degrees. A newer version incorporates a video camera at the distal tip.
	The AI Video RIFL; an optical  stylet with an articulating tip and integrated monitor.

the jaw, while their right manipulates the scope down the right side of the mouth to the larynx. Depending upon the operator’s arm length and their comfort manipulating a relatively long instrument, this may be result in a relatively far distance from the operator (and eyepiece) to the patient.  There is an articulating eyepiece, however, which can be tilted downward and lessen the distance to the eyepiece depending on the specific method of use. The Shikani Stylet, also designed as an independent device, has a malleable distal section with an intended bend 70 and 90 degrees from the main section.  As this is navigated around the curve of the tongue and oropharynx the proximal end of the scope (and eyepiece) will be positioned in a near vertical position, approximately 30 cm or more directly above the patient’s mouth opening.  Depending on the height of the stretcher and the operator’s height this may be ergonomically difficulty.  The head of the bed can be lowered (not always an option depending on the patient stretcher), the operator can position themselves on a stool to gain additional height, or alternatively, the operator can face the patient’s head and roll the device partially into the mouth before moving to a position more directly above the supine patient.  In the spontaneously breathing patient, positioning the patient in a semi-sitting or upright position with the operator facing the patient will also address this problem.   The Video RIFL, with its attached video screen does not have these ergonomic issues since the operator does not need to use an eyepiece, and the articulating tip can be dynamically changed during the procedure (so there is more freedom of insertion from different positions). The Levitan FPS is deliberately shorter than other optical stylets (29 cm) because it was designed to be used in conjunction with a laryngoscope.   It can also be used without a laryngoscope using a near right angle bend (~65-75 degree bend) like the Shikani Stylet, but its overall shorter length eliminates height problem for most operators.