|Year : 2012 | Volume
| Issue : 1 | Page : 1-2
Bending the rules-The flexible CO2 laser in head and neck surgery
ENT/Head and Neck Surgeon, University College London Hospital, London, United Kingdom
|Date of Web Publication||9-Apr-2012|
ENT/Head and Neck Surgeon, University College London Hospital, London
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
O'Flynn P. Bending the rules-The flexible CO2 laser in head and neck surgery. J Laryngol Voice 2012;2:1-2
The popularity of CO2 laser in the field of laryngology has made it a workhorse and indispensible tool in the modern armamentarium of the ENT surgeon. CO2 lasers emit energy with a wavelength of 10 600 nm, highly suitable for airway surgery. The key advantages of CO2 lasers in the airway are accuracy, ease of access, and the minimal collateral damage caused to surrounding tissues.
However, with conventional CO2 lasers, there is a major limitation of delivering the laser beam to the intended target in a "line of sight fashion." The CO2 laser light travels in a straight line and needs optics to guide it along tubes and prisms. There remain areas in the upper airway that are difficult to reach like the nasopharynx, tongue base, and subglottis. There are also patients in whom anatomy or previous treatment makes access difficult. Examples may include cases with prominent dentition or overbite, craniofacial abnormalities, and trismus. Occasionally, spinal problems including fixation, kyphosis, and rheumatoid arthritis also limit our usage of the traditional CO2 laser tools.
The challenge therefore is to develop a delivery system that can "bend the rules" and make the CO2 laser beam "flexible."
Classically, fibers transmit light using a basic principle of optics called total internal reflection. This property of the light to be internally guided depends on the material of the fiber. The CO2 light, however, has a wavelength which gets absorbed instead of getting reflected by materials used to make the fiber. In 1998, Fink et al.  published a description of how this problem could be overcome. They developed a reflector consisting of multiple alternating layers of glass and polymer to demonstrate omnidirectional reflection of wavelength range from 10 to 15 micrometers. A fiber based on these principles was developed to selectively enable transmission of CO2 laser light with minimal transmission losses.  Now, there are commercially available systems exploiting photonic band-gap principles to produce flexible CO2 fibers. The CO2 laser energy passes through a hollow fiber confined by a series of concentric mirrors whose thickness and the gap between them is related to the wavelength of the CO2 laser, i.e., 10 600 nm. The fibers are cooled by the passage of gas (air or helium) through the core. This allows the transmission of CO2 energy around corners and thus beyond the limitation of line of sight.
This new paradigm has the potential to "bend the rules" of the usage of medical laser in the upper airways. The potential advantages include greater accessibility and lesser invasive surgery.
The usage of these lasers is a comprehensive topic in itself, but briefly consists of five essential components namely-the conventional base laser unit, a connection system to the fiber, the fiber itself, a supply of gas, and headpieces.
The base unit is the conventional CO2 laser. Connection to the laser at the proximal end of the fiber remains an area of development. Accuracy of inputting the laser energy into the fine core of the fiber is essential. Then, there is the fiber itself which is specially adapted for use in CO2 lasers. This fiber needs to be cooled and therefore a supply of gas and a system to control the flow is coupled. Although the fibers are flexible and can be bent, they are fragile and can readily be damaged. Kinking of the fiber causes a blockage of the cooling gas flow and burn out of the fiber if laser energy is deployed down it.
The fiber is eventually guided into the area of surgery using various types of curved and angulated hand pieces.
The laser may be used in conjunction with a suspension laryngoscopy and microscope. More commonly, however, the flexible CO2 is used in conjunction with microlaryngoscopy set up with angled Hopkins rod telescope which enable visualization "around the corners." [Figure 1] shows the setup in both these situations.
The fiber itself can also be used through an instrument channel of a flexible endoscope.
As with other medical lasers, safety is an integral requisite for using these lasers. Apart from the general laser safety measures and eye protection, certain additional precautions are required. These include testing the beam on wooden spatula to confirm energy at distal end of fiber. This is especially so since the beam diverges from tip, so power falls as inverse square (unlike collimated beam). The distal tip of the fiber should be dipped in water to check flow of gas. As a precaution, the laser is not safe for use below the carina.
Flexible laser fibers are being used increasingly in surgery and in particular the Head and Neck region. Our initial clinical usage has been encouraging.  As these technologies continue to develop, they are bound to become more reliable. In combination with robots, these fibers will open up even more inaccessible areas to surgical intervention. At present, the place for their use is restricted, at least in part to the costs involved. However, the future is exciting and as we laryngologists wait for increasing our surgical armamentarium, the flexible CO2 laser has the potential to be a landmark development.
| References|| |
|1.||Fink Y, Winn JN, Fan S, Chen C, Michel J, Joannopoulos JD, et al. A Dielectric Omnidirectional Reflector. Science 1998;282:1679-82. |
|2.||Temelkuran B, Hart SD, Benoit G, Joannopoulos JD, Fink Y. Wavelength-scalable hollow optical fibres with large photonic bandgaps for CO2 laser transmission. Nature 2002;420:650-3. |
|3.||O'Flynn P, Awad Z, Kothari P, Vaz FM. The first UK report of the applications of flexible CO2 laser in head and neck surgery: How we do it. Clin Otolaryngol 2010;35:139-42. |
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