Pdl

585 nm

Hemoglobin

Ho:YAG = holmium:yttrium-aluminum-garnet; KTP 532 = potassium titanyl phosphate at 532 nm; Nd:YAG = neodymium:yttrium-aluminum-garnet; PDL = pulsed dye laser.

Ho:YAG = holmium:yttrium-aluminum-garnet; KTP 532 = potassium titanyl phosphate at 532 nm; Nd:YAG = neodymium:yttrium-aluminum-garnet; PDL = pulsed dye laser.

of the micromanipulator, an optic system coupling the laser source to the operating microscope, was key in providing microprecision and the ability to achieve small vessel (< 0.5 mm) hemostasis.

The CO2 laser was first clinically applied in the airway by Strong and Jako in 1972 for a variety of laryngeal lesions which included laryngeal papillomas, carcinoma in situ, and vocal cord nodules, among others.1 Over time, the number of applications and techniques using the CO2 laser has multiplied, and today, it is considered the mainstay of treatment for laryngeal hemangiomas, recurrent laryngeal papillomatosis, and for properly selected cases of laryngeal cancer and laryngeal stenosis.2-5

CO2 Laser-Soft Tissue Interaction. The 10.6 |im infrared wavelength of the carbon dioxide laser undergoes a 90% absorption by water contained in soft tissue. This laser light is then transformed into heat within tissue, raising the tissue temperature to 100°C and vaporizing the water content. The remaining 10% is carbon residue, which should be removed manually to avoid inflammatory tissue reaction. The steam of vaporization needs to be removed with an efficient suction device to avoid collateral damage from the hot vapors.

There are three important parameters that should be kept in mind when delivering laser energy. These are power (w), exposure time (sec), and power density (spot size). Of these basic parameters, time exposure is the most important. Limiting the time of laser exposure with short applications minimizes heat conduction within tissue, thus limiting collateral damage. Basic studies of soft tissue interaction in canine trachea showed excellent depth of penetration with minimal damage to the adjacent tissue.6 The energy curve of the focused CO2 laser (micromanipulator) is in the shape of an inverse gaussian curve; that is, the maximal power is at the center of the beam, fading at the margins.

A major disadvantage of the CO2 laser is that it can not be transmitted through flexible fibers, which limits its usefulness in the trachea and bronchi. The CO2 laser must be delivered from the source, using a somewhat awkward articulated mirror system. Other delivery systems such as a semiflexible hollow waveguide can also be used, however, this does not provide a focused, "clean" beam and suffers from imprecise soft tissue interaction. The CO2 laser is usually and best used in a focused fashion through a microspot micromanipulator (250 micron spot size) for applications in the larynx and subglottis down to the first tracheal ring, using a laryngoscope placed on a suspension system, thus freeing up the surgeon's hands. We prefer a standard diagnostic laryngoscope such as the Dedo design (Pilling Co., Philadelphia, PA), inserting the laryngoscope between the vocal cords and exposing the subglottic larynx up to the first tracheal ring.

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