Bleeding is reduced with the use of the CO 2 laser because of its coagulating properties it seals small vessels as it cuts. Depending on the power density, the CO 2 laser can be used effectively for vaporizing tissue, for excision, or for incision. The instantaneous boiling of intracellular water causes cells to explode, forming steam. The CO 2 beam is readily absorbed by tissue because of its high water content. Of the various lasers available, the CO 2 laser remains the most versatile and is relatively safe because of limited depth penetration. Conversely, by decreasing the diameter of the spot size, the power density is increased by 4 ( Table 1). Doubling the beam diameter reduces the power density to one fourth. Power density is, therefore, inversely proportional to the area of the spot size and to the beam diameter. This concept is expressed in watts/cm 2 (unit/area) and referred to as intensity or power density. The higher the power density, the greater the laser's ability to vaporize and cut. The combination of watts (power) and spot size determines the rate of tissue interaction. As one gets closer to the target area, the spot size is made smaller, producing a more intense effect. The third parameter that can be controlled is the spot size of the beam. To limit tissue damage, especially in critical areas, one can simply move the beam back and forth, or select an intermittent, timed pulse mode, usually in fractions of a second. The longer the laser remains focused on one spot, the more energy is applied to that area. For most gynecologic procedures using the CO 2 laser, one rarely exceeds 20–30 W, which is used primarily for excision purposes. There are three basic parameters that determine the amount of energy being delivered to the tissue. Also, with the use of wave guides, one eliminates the problem of intermittent focusing of the beam that is associated with the joystick device (Fig. Fine focusing can be done through a joystick or automatically with a coupler. With laparoscopy, the focal length is longer, taking into account the length of the laparoscope. With the hand-held attachment, the focal point is usually 10 cm away from the focusing lens.
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A lens system is used to focus the laser to a focal point. The laser beam comes out of the port as an unfocused beam. The CO 2 laser, in contrast, produces a wavelength of 10,800 nm, which is in the nonvisible part of the electromagnetic spectrum thus, a helium–neon laser is also used, which produces a red light to identify the location of the CO 2 beam. The KTP produces a wavelength of 532 nm, making its light a green color. The argon laser produces a wavelength of 510 nm, making a blue-green light. Actual view of a CO 2 laser tube ( below) and coincident helium–neon laser ( above ), which provides visible aiming target.ĭifferent colors are produced by different lasers.