it is seen with the use of lasers that do not make use of optical fibers for laser beam delivery , such as carbon - dioxide ( co2 ) lasers which use articulated arm technology .
they have optical fibers for delivery of the laser at the site of surgery , facilitating more precision and control .
a 7-year - old boy was admitted for excision of a cystic swelling at the posterior aspect of the base of the tongue a few centimeters anterior to the valleculae .
the smallest laser endotracheal tube ( ett ) available was of 7-mm outer diameter ( od ) and an internal diameter of 5.5 mm .
after induction of anesthesia with propofol , followed by administration of suxamethonium intravenously ( iv ) , nasotracheal intubation was done with this tube .
anesthesia was maintained oxygen in air , atracurium , intermittent boluses of propofol , and fentanyl iv .
the saline - soaked throat pack was obstructing the field of vision of the surgeon and also restricting the outward pull of the tongue as cyst was large ( 3  3 cm ) and placed posteriorly .
the surgeon assured that adequate precautions would be taken to avoid bringing the diode laser delivery handle tip in contact with the ett . toward the end of the surgical laser excision , the tip of the handle accidently slipped and touched the ett .
we heard a very short  pop  like noise which lasted for about 12 s. the exhaled gas from the expiratory valve also smelt of smoke for about a minute or so .
there was however no change in hemodynamics , drop in spo2 or reduction in air entry / chest expansion .
as the surgery had been completed and we were able to ventilate the lungs , we reversed the neuromuscular blockade .
after tracheal extubation , a flexible laryngopharyngoscope was passed to visualize the trachea up to the carina and fortunately everything appeared to be normal .
the removed ett [ figure 1 ] had a very small circular hole and the inner aspect of the tube was black distal to the hole [ figure 2 ] .
the cuff was intact but the tubing from the pilot balloon to the cuff was damaged , which is typically seen in 
patient recovered well and was shifted to postoperative , ward , monitored and given humidified oxygen and discharged next day .
diode lasers are used with low power setting and do not usually cause perforation or damage to polyvinyl chloride ( pvc ) ett coming in direct contact . though studies have shown silicon and red rubber tubes to be more resistant to ignition compared to pvc , some studies have reported that pvc is less flammable than silicon or red rubber , having a flammability index of 0.26 vs. 0.19 for silicon and red rubber , respectively .
use of laser resistant material wrapped around pvc ett or double - cuffed silicon - coated ett is however more safe .
laser - resistant ett are bulkier and more rigid than conventional ett and thus need careful insertion to prevent mucosal abrasions . in the event of a blow - torch phenomenon ,
pvc tubes burn more vigorously and hydrochloric acid may be produced , which is a pulmonary toxin . in case of such an airway fire ,
oxygen should be temporary discontinued , damaged ett removed , trachea reintubated with a fresh ett , and the pharynx flushed with cold saline .
a rigid or fiberoptic bronchoscopy examination should be done to look for damage and pieces of burned ett .
humidified oxygen , steroids , and antibiotics must be administered and at times controlled ventilation and tracheostomy may become necessary .
postoperatively , patient should be intensively monitored and a chest x - ray should be taken .
surgeons must ensure that laser energy is not reflected from smooth metal surfaces or directed at sensitive structures . applying protective metal foil wraps to ett , such as aluminum or copper
has been advocated.[35 ] the ett cuff can be filled with colored saline and placed far distally in trachea and the visible cuff covered with moistened cotton pledgets , which should be remoistened as needed .
laser resistant tubes are available for use during laser surgery . to reduce the obstruction in the surgical field , by airway instruments ,
 we report a case of blow - torch phenomenon encountered during diode laser assisted excision of a thyroglossal cyst in a child . 
 this is first such case report from india and highlights an unusual complication which anesthesiologists need to be aware of due to the increasing use of operative laser . 