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When operating lasers, what three variables are set by the physician?
- power (measured in watts)
- spot size (measured in millimeters)
- exposure time (measured in seconds)
How does scatter impact the effect of the laser?
Scattering tends to spread the laser energy over a larger surface area of tissue, but it limits the penetration depth. Light of shorter wavelength has greater scatter.
What is a strategy for minimizing thermal collateral damage?
To minimize lateral thermal damage from thermal diffusion, the tissue should be ablated with a short laser pulse.
Describe the properties of a Neodymium:Yttrium-Aluminum-Garnet (Nd:YAG) Laser.
- wavelength of 1.064 µm in the near infrared range
- can be transmitted through clear liquids, facilitating its use in the eye
- Absorption is slightly color dependent, with increased absorption in darkly pigmented tissues and char
- strong scattering and deep penetration makes precise control impossible.
- Good for coagulationp
Describe the properties of Carbon Dioxide (CO2) Laser.
- wavelength of 10.6 µm in the infrared (invisible) range
- strongly absorbed by pure, homogeneous water and by all biologic tissues high in water content.
- The extinction length of this wavelength is about 0.03 mm in water and in soft tissue.
- Reflection and scattering are negligible.
- absorption of the radiant energy produced by the CO2 laser is independent of tissue color
- the thermal effects produced by this wavelength on adjacent nontarget tissues are minimal
Describe the properties of the Potassium-Titanyl-Phosphate (KTP) Laser
- 532 nm comparable to Argon
- scattering and absorption by skin pigments when using the KTP laser are nearly the same as for the Ar laser
- the KTP laser light is more strongly absorbed by hemoglobin
Describe the properties of 585-nm Pulsed Dye Laser
- 585-nm pulsed dye laser (PDL)
- used mainly as a photoangiolytic laser for laryngeal applications.
- The targets oxyhemoglobin, which has an absorption peak of 571 nm.
- absorbed by intraluminal blood of vascular lesions such as papilloma, vascular polyps, vocal fold ectasias and varices.
- PDL causes involution of the lesion through disruption of the vascular supply rather than immediate removal of the lesion.
Which protective glasses are worn with which laser?
- CO2: clear lenses
- Nd:YAG: blue/green
- KTP, Ar: tinted
What do you do In the event of tube ignition during a laser airway procedure?
- ventilation must be stopped immediately and the tube withdrawn simultaneously as saline is flushed down the endotracheal tube.
- reestablish airway immediately
- bronchoscopy performed to assess the degree of injury.
- Intravenous steroids may be delivered and the patient should remain intubated; repeat bronchoscopy should be performed daily until it is established that the airway is stable.