The risks of laser surgery are the following:

A new technique without thermal injury is the endoscopic microdebrider. A survey of ENT surgeons expressed consensus that this technique replaces “shaving with the CO₂ laser” [5]. The cold microdebrider removal is more often used in adult patients.

Fire needs three things: flammable material, ignition, and oxidizing agent [3]. Flammable material could be tubes, sutures, topical sprays, dry tamponades, tonsil tissue, dry connective tissue, muscle, and fat.

Flammable anesthetics such as ether and cyclopropane are no longer in use. Source of ignition could be electric cautery or laser. Oxidizing agents include oxygen (O₂) and nitrous oxide (N₂O).

>> Dr. Andrew considered which tube would be best to use. Assuming there would be no laser, he decided on the Magill tube. “What is this tube made of?” asked Imo, bubbling over with curiosity.

Endotracheal tubes are either made of polyvinyl chloride (PVC), silicon, rubber, or metal. These days, most tubes are PVC, which are free of latex.

>> Dr. Andrew felt trapped by his own ignorance and sneaked a peak at the package, “It’s made of PVC.” Ever–energetic Imo took another from the drawer: “This one is silicon. Which is better suited for laser surgery?” she asked. While Dr. Andrew was silently cursing the question, anesthesia tech Steve came to the rescue and interrupted the two. “Can we get to work? The coffee I just made will be gone without me if I don’t make it to the break room soon!”

All endotracheal tubes, regardless of their composition, can catch fire if burned by a laser. The flammability of a material is described by its limiting oxygen index (LOI), critical oxygen index (COI), or oxygen index of flammability (OI). To determine the OI, various mixtures of oxygen and nitrogen are placed in the tube and then lit with a hydrogen flame. The oxygen concentration is increased, until the burning continues after removal of the flame. The OI describes the minimal concentration of O₂ in an O₂/N₂ mixture, which is still capable of supporting the flame. High OI values indicate high flammability protection/low flammability. The formula is
and is given in percent. Since nitrous oxide is also an oxidizing agent, there is a N₂O index on every tube.

Air contains 20.95 % oxygen. Every material which has an OI value <20.95 % is ignitable in room air. A material with an OI value of >20.95 % would burn poorly in room air. The value can approach zero, after the igniting flame is removed [4, 6].

Table 23.2 shows the OI value of various endotracheal tubes, which are discussed in Fig. 23.1 (according to [6]).

>> Dr. Andrew gave Lisa 75 μg fentanyl IV. She participated wonderfully in preoxygenation with the “astronaut mask,” and after 100 mg of propofol, she was fast asleep. “The mask ventilation is going well” said Dr. Andrew to anesthesia tech Steve. “Give her 4.5 mg mivacurium.” During the laryngoscopy, Dr. Andrew had a full view of the vocal cords. The papilloma was on the right.

The size 5 unblocked tube slid safely through the glottis. Afterwards, remifentanil at 0.3 μg/kg/min and propofol at 150 mcg/kg/min were started. Together with the ENT surgeons, Dr. Andrew positioned Lisa. Vital signs were unremarkable; however, after hyperextending the neck, a small leak appeared.

Repeated tracheal intubation and extubation increases the chance of bringing infectious material into the trachea and increases the danger of causing mucosal irritation. The ENT procedure in and of itself has the potential to cause mucosal edema, so additional intubation injuries should be avoided. An inflatable cuff can compensate for a tube that is too small and help to avoid changing the tube. Also, cuffed tubes help to prevent fresh gas leaks (e.g., leaks which arise by positioning the head) and an unmeasurable amount of O₂ and nitrous oxide leaked into the surgical area. Cuffed tubes can also prevent pieces of removed tissue from being carried into the trachea.

>> “Should we reinsert a larger tube?” asked anesthesia tech Steve. Before Dr. Andrew could answer, the ENT surgeon said “I’ll put some sponges around the entry to the larynx. That should seal the leak.” And then the surgery began. Dr. Andrew filled out his anesthesia record, and the ENT surgeon operated in silence. After a while, he glanced up from his surgery. “I think I’m going to have to use the laser. The papilloma is just too extensive to handle without it.”

In pediatric otolaryngology, there has been an interesting trend during the past 15 years in operative and anesthesia techniques. In the 1990s, a CO₂ laser was used in 90 % of the surgeries and a laser-resistant endotracheal tube in 50 %. Today, the microdebrider has taken the place of the CO₂ laser; the anesthesia techniques changed with the surgical variations. Two-thirds of papilloma surgeries are done with spontaneous breathing or periodic ventilation. Controlled ventilation occurs in ¼ of the cases via jet ventilation, and a laser-resistant endotracheal tube is used in 10 % of procedures [5]. The choice of method to use depends on: