Carbon dioxide (CO2) laser use is widely accepted in veterinary surgery because of its advantages: reduced hemorrhage, swelling and pain, increased precision and minimal tissue trauma, and because of the development of many laser-improved and laser-specific procedures. The popularity of veterinary CO2 laser surgery has attracted many vendors. Each vendor contends that its laser is the best and its marketing creates confusion for veterinarians considering laser devices for their practices. The most important decision when selecting a laser is which delivery system to purchase. What is available? Which best meets patients’ needs? Which will be used most often? Which will give the greatest return on investment? CO2 Laser Delivery Systems Articulated Arm (AA) laser technology was developed in the 1970s. AA lasers deliver the laser beam to the tissue through a sophisticated four elbow, seven mirror articulated arm. The laser beam is focused 2-3 cm from the hand piece by a lens in the hand piece’s base. Since the operator must hold the hand piece away from the tissue for the beam to focus, these devices require a visible aiming beam. Hollow wave guide (HWG) lasers were developed in the 1990s and deliver the laser beam through a thin, flexible, hollow waveguide commonly called a "fiber.” The beam exits through either a pencil-size hand piece, focused by interchangeable, reusable and autoclavable focusing tips, or through a slender, adjustable tipless hand piece. Focusing tips and the adjustable tipless hand piece have focal lengths of 0.75 – 3 mm, so both are held very close to the tissue. No aiming beam is required. Factors in Selecting a Delivery System Ergonomics. The thin, flexible HWG and its pencil-like hand pieces are easy and comfortable to use. Its flexibility allows for convenient positioning and suspension of the hand piece over a mayo stand for ready access. The thick and restricted-movement AA delivery system limits laser position, and doesn’t always allow suspension of the hand piece at an appropriate height above a mayo stand. The weight, size and bulk of the AA system can result in arm and hand fatigue. Availability of Multiple Spot Sizes. HWG lasers offer multiple size focusing tips that can be quickly and easily changed during surgery: 0.2, 0.25, 0.3, 0.4, 0.8, 1.4 mm, or 0.4 mm x 3 mm. This variety of tip sizes allows the surgeon to select the size that will produce the best effect. AA lasers offer one fixed focal spot size, usually .2 - .25 mm. Precision. The HWG hand piece is held very close to the tissue, allowing enhanced precision and use in a great diversity of procedures. It is aimed from a distance of 0.75 to 3 mm, allowing the surgeon to gain maximum stability by resting the hand holding the hand piece on the patient. AA delivery hand pieces are held 2 to 3 cm from the tissue, resulting in less precision and requiring a visible aiming beam which is 10 or more times the diameter of the laser beam. AA lasers are effective for simple skin incisions and gross dissection, but not for procedures requiring precision. Ability to Defocus. Maximum power density is desired for cutting or removing tissue, but reduced power density can be used for hemostasis and contracting tissue. HWG focusing tips, having a focal length of 0.75 to 3 mm, produce a laser beam with wide angles of convergence and divergence and allow adjustment of power density with slight hand movement, by backing away from the tissue. AA laser hand pieces utilize a focusing lens with a fixed, 50 to 100 mm focal length. Its laser beam has very narrow angles of convergence and divergence and can only be defocused by backing the hand piece a great distance away from the tissue. Laser Power. Small-animal surgeons need no more than 30 watts of power. AA lasers for veterinary use range from 10 to 30 watts. HWG lasers for small animal use go up to 30 watts. For large-animal use, HWG lasers go up to 40 watts and represent the highest power commercially available for veterinary applications. Difference in cost of the two delivery systems is negligible when comparing devices of equal power. Beam Pulse Configuration. The best tissue effect is achieved by modifying laser beam pulse configuration according to tissue characteristics. The newer technology metal laser tubes of HWG lasers allow complex pulsing and offer pulse mode options for best tissue effect. The older technology glass laser tubes in AA lasers do not allow complex pulsing. Safety. Because of the wide angle of divergence of HWG focusing tips and the rapid defocusing of the beam, the danger zone for eye injury is relatively short. With the narrow angle of divergence of the AA focusing lens system, the laser beam maintains high power density for a great distance. The potential danger zone is much greater with AA devices. Calibration. HWG lasers have an external calibration feature so that the energy exiting the delivery system is precise. AA lasers rely on an internal power meter that monitors the energy entering the delivery system. Energy attenuation within the AA delivery system may affect the energy exiting the system. Disposables. AA lasers have no disposables. Modern hollow wave guides are durable and have long life. (The author has used a single HWG for as long as five years in thousands of surgeries.) Focusing tips for HWG lasers are reusable and have a virtually infinite life span. HWG’s latest advancement—a tipless hand piece—not only eliminates tips, but offers multiple spot size options in one autoclavable device for faster and better handling. Maintenance. Long-term cost for any piece of capital equipment depends on the credibility of the manufacturer and the reliability of its service organization. Firms with positive testimonials and references are much preferred. Veterinarians should avoid vendors that do not have well established service capabilities with long-term service contracts, loaner policies and quick turn-around of repairs. Training, education and clinical reference materials. The overwhelming popularity of HGW lasers means virtually all laser surgery courses, workshops and wet labs focus on and use the HGW lasers. Since HWG lasers have been the most used in practice, the body of clinical knowledge generated over the last 15 years is about HWG technique and its application in procedures and surgeries. HWG lasers now feature an on-board atlas of laser surgery with procedures, settings, pictures and videos. With no comparable body of knowledge, AA laser owners must extrapolate recommendations for HWG lasers to their own devices and apply that information to the limited number of HWG procedures in which AA lasers can appropriately be used. Return on investment. To justify purchase, capital equipment must be used often enough to generate revenue to pay for itself and make it profitable. Lasers can be very profitable if used frequently. Because of their versatility, HWG lasers can appropriately be used in virtually every surgery done in practice. Their ROI is very short. AA lasers have limited applications and require longer time for ROI. Conclusions A surgical laser will enhance surgical capabilities in a general practice. Selection of the delivery system is the most important consideration. Prospective surgeons should carefully consider the differences in the delivery systems prior to purchase. (Note: The author owns two surgical lasers – a 30-watt articulated arm laser and a 30-watt hollow wave guide laser. With full understanding of the issues discussed in this article, the author uses his HWG laser every day. His AA laser sits idle.) l Dr. Godbold established Stonehaven Park Veterinary Hospital in Jackson, Tenn., in 1980. Since 1999, he has pursued a special interest in surgical lasers and laser-associated technologies. This Education Series article was underwritten by LuxarCare of Woodinville, Wash.
