THE DIODE LASER IN NASAL SURGERY

Farneti G., Magnani G., Tesei F., Parmeggiani A., Balbi M., Pasquini E.Ear, Nose and Throat unit of Budrio, Bologna Area Health Authority,Ear, Nose and Throat Clinic, The photothermal effects producedcan be summarised as: hyperthermia, oedema and protein - denaturation, coagulation,vacuolation, vaporisation (boiling, necrosis), carbonisation, incandescence. Apart from thelast two harmful effects, the others are observed in the region of application, in anincreasing order, getting closer to the target of the action.In surgical practice, the result of an intervention with a laser depends on the type used, onthe way the laser light is absorbed by the tissues and on the duration of the exposure. Thehigher the degree of energy absorbed by the tissue, the greater the collateral damage tothe adjacent tissues. This effect may be useful if a coagulating action is required. On theother hand, if the tissue is rapidly vaporised without peripheral damage, an excellent‘cutting’ action is achieved with little haemostatic effect.

The laser can be used in different emission modes:
· Continuous (1, 2, 3, W/sec) that enables both rapid coagulant action and excellent removal of tissues in relation to the power delivered. The thermal damage is directly proportionate to the time of application;
· Pulsed (10‘W/msec), which permits less peripheral heating than continuous emission over the same time
· Super-pulsed (1000W/ sec), which preserves the surrounding tissue
· Ultrapulsed 100W/ nanosec), with shockwave without heat nor cell ablation There are three modes of applying the photonic beam
· Contact: the tip of the laser fibre is placed directly on the surface of the tissue.Depending on the energy power, both vaporisation (cut) and coagulation can be achieved;
· Non-contact: the tip of the laser fibre remains some millimetres from the tissue; this method is used above all for photocoagulation;
· Interstitial: the laser is positioned through a small hole in the mucous membrane and its energy is absorbed by the local tissues.Laser rhinosurgery is a relatively recent development. Lenz (24) in 1977 was the first to report the intranasal use of the Argon laser for surgical treatment of vasomotor rhinitis. Healy (16) in 1978 was the first to discuss the use of CO2 lasers in rhinology. The application of the laser in nasal endoscopic surgery it very promising but has been hindered by the absence of suitable instruments that would enable the laser to be conveyed to the intranasal level in combination with the optic-fibre rhinoscopic equipment and aspiration devices.
In 1996 Metson (26) defined the characteristics of the ideal laser for rhinosurgery:
· efficient ablation of both soft tissue and bone;
· precise removal of the tissue at a depth of less than 1 mm;
· removal of the tissue with haemostatic action;
· coagulation of vessels with a diameter of greater than 0.5 mm;
· possibility to deliver the laser beam with guide probes to the intranasal level withoptic fibres.

Instruments
The equipment used in our ENT unit is the OTO 808 diode laser, which consists of 4
components:
1. a central body that encloses the laser source, the lenses, the heat exchangers and all
the electronic controls
2. a palmtop computer for monitoring the laser parameters
3 a pedal for actuating the radiation
4 a handpiece or optic fibre to release the energy to the tissue.
Our appliance belongs to Class IV risk class and emits infrared laser radiation with
wavelengths between 630 and 670 nm for the guide laser and for laser radiation for the
envisaged use of the OTO 808 at 808 nm. Its maximum emission power is 30 Watts and
divergence of the laser beam is 470 mrad.
It can be used in continuous light beam emission mode or in pulsed mode (with single or
repeated modes). The usable optic fibres and the respective applicable maximum power
rates are 200 μm (max 7W), 365 μm (max 10W), 600 μm (max 25W), 1000 μm (max 30W).
One of the main obstacles to the application of the laser in nasal endoscopic surgery is
due to the lack of suitable instruments for conveying the lasers at the intranasal level in
combination with rhinoscopic equipment with optic fibres and aspiration devices.
The simplest system consists of fixing the fibre to malleable and flexible supports that
enable the fibres to be directed in given directions but do not allow simultaneous aspiration
of the vapours.