The history and future of carbon dioxide lasers

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The history and future of carbon dioxide lasers
Oct 1, 2007
Joely Kaufman, Rita Patel
Dermatology Times

Since its invention by Dr. Kumar Patel in the early 1960s, the carbon dioxide laser has evolved into one of the most extensively manipulated lasers in medicine. The first documented use of the CO2 laser dates back to the early 1970s, when otolaryngologists used it on cadaver larynxes. It was next adapted to the laparascope and colposcope, which allowed for the treatment of various gynecologic diseases. The successful precision of the laser-tissue interaction of the CO2 laser in gynecologic studies led to the laser's introduction to dermatology, where it was originally applied to aesthetically improve the appearance of congenital vascular lesions such as port wine stains and hemangiomas. Today, the CO2 is used to therapeutically treat a gamut of dermatologic conditions, ranging from aesthetic to congenital deformities to benign, premalignant and malignant tumors, and even to infectious lesions.

The CO2 laser, using gas (CO2) as its medium, emits coherent light at a wavelength of 10,600 nm. At this infrared wavelength, water is the tissue chromophore. The water in skin is located both intracellularly and extracellularly, and with sufficient heating, vaporization occurs, leading to tissue coagulation and ablation. This ablation leads to immediate, visible tissue contraction. Months later, histologic evidence of new collagen and elastin formation is seen. CO2 laser resurfacing has been used for photoaging, including lentigos, fine and moderate rhytides, rhinophyma, dyschromias and acne scarring.

Carbon dioxide laser resurfacing has been considered the gold standard in laser resurfacing, producing clinical results that have not been reproducible by any other system to date. Unfortunately, these dramatic results also come with their share of complications.

The first CO2 laser to be introduced emitted light at 10,600 nm in a continuous fashion. Continuous wave (CW) lasers apply heat during the entire time the laser is in operation mode. The amount of heat generated will depend on how quickly the handpiece is moved and how many passes are performed. Results were variable, with a high rate of complications, especially in new users, which led to changes in the CO2 laser delivery system.

THE PRESENT

Simply changing the delivery of the same wavelength of light has resulted in a system that has been used successfully in dermatology for years. In the 1990s, two new CO2 systems were developed to shorten the exposure time of the skin to this infrared light (the pulsed CO2 and the scanning spot CW CO2).

The goal with any laser system is to avoid collateral damage when treating the target. This is done by keeping the exposure time to less than the thermal relaxation time of the target, preventing excessive spread of heat to surrounding tissues. Exposure times less than or equal to one millisecond have proven to be much safer with the CO2. The pulsed CO2 laser does just that. It delivers pulses of light of duration less than one millisecond. The high-energy short-pulsed system uses a flash of energy that is short enough in duration to prevent heat from dissipating into surrounding tissue. The scanned carbon dioxide laser system uses a computer-controlled mirror to rapidly scan an area in less time than is needed to expel heat into the bordering tissue. The scanning CO2 laser uses the continuous wave laser, but delivers spots with each exposure time less than one millisecond. Depth of tissue injury is more controlled between 20 and 120 microns per pass. This reduces the potential for scarring.

Still, even with the pulsed and scanning spot deliveries, CO2 lasers do have their downside. Each physician using this laser must be well-trained in its capabilities and nuances. Even the pulsed and scanning CO2 lasers are extremely operator-dependent. The procedure is painful and requires some form of anesthesia. Patient selection is an important part of success with CO2 resurfacing. In addition to selection for skin type, patients need to be properly counseled on the procedure and recovery. Healing after CO2 can take two weeks or more, with some patients developing residual erythema for months. Proper woundcare during the recovery phase is essential. Despite these precautions, some ideal patients treated at ideal settings still end up with complications including hypertrophic scarring, depigmentation, hyperpigmentation, or shiny, unnatural-appearing skin. Because of their flexibility and lower side-effect profile, the high energy, pulsed and scanned CO2 lasers are now the models used for facial photorejuvenation.

THE FUTURE

For years researchers have been looking for laser treatments for photoaging that could compete with those of the CO2 lasers, but with a better safety profile. Safety became the focus of many lasers after the complications with the CW CO2 laser, and led to the introduction of the non-ablative laser systems. Focus now has been on the fractional systems for photorejuvenation. The original fractional devices are within the non-ablative wavelength ranges with excellent clinical results and a superior safety profile. Still, the tissue contraction seen with the CO2 is difficult to duplicate, and hence the recent drive to re-invent the CO2.

Fractional ablative lasers are now reaching the market, with several more to be released in the next year. Lumenis has introduced the ActiveFX. This system employs a pulsed CO2 laser with a computerized pattern generator that ablates only a fraction of the skin with any treatment. The spots are placed non-sequentially, allowing for maximal skin cooling of treated areas. The spot size is in the millimeter range, with each treatment spot separated by an area of untreated viable tissue. This viable tissue serves as a source for cells for rapid wound healing. Healing times after ActiveFX treatment is in the order of three to four days, as opposed to the two weeks for traditional CO2. There is more downtime than with non-ablative fractional resurfacing, but much less than with traditional CO2 resurfacing. Treatments are rapidly administered and tolerable with topical anesthesia alone. In addition, this system can be used in a traditional, more aggressive CO2 mode.

Another FDA-approved CO2 system Û to be available at the end of the year Û is the Fraxel:Re-Pair (Reliant). It will also use CO2 as its medium, and emit laser light with a wavelength of 10,600 nm. The Re-Pair laser system is a fractional, deep dermal ablative system (FDDA) approved for ablation, coagulation and skin resurfacing procedures. This system will treat to depths measuring more than 1.6 mm, and will differ from the other CO2 lasers in its smaller micron spot size. This micron spot size would potentially reduce the healing times and complication rates even further. One completed study using this device demonstrated efficacy in more than 75 percent of the 30 patients treated (Rahman et al). More importantly, they reported no adverse effects.

The MiXto CO2 laser was just recently introduced to the United States by Lasering USA. This device will offer microspot technology with a scanning delivery system. Clinical data on this device is still unpublished.

Carbon dioxide laser resurfacing will continue to be one of many tools in the aesthetic market. Though the ideal settings, spot size, number of passes and number of treatments is still to be debated, restructuring the CO2 laser to improve its safety profile and patient tolerability, while preserving its efficacy, will surely be well-received

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