Endotracheal tube ignition during laser surgery of the larynx

Development of an Improved LASER-Resistant Endotracheal Tube

OBJECTIVES

Surgical fires, particularly within Otolaryngology, remain a surprisingly frequent and devastating complication of laser-related surgery in the oropharynx and airway; Current estimates suggest anywhere from 200 to 600 surgical fires per year in the United States, with 20%-30% of these occurring as a complication of laser surgery and 90%-95% of these occurring in the head and neck region. Unfortunately, the complications of laser surgery in the airway may include respiratory failure, airway burns with stenosis, and may result in mortality. The most commonly utilized endotracheal tube for protection against inadvertent laser strikes, the Laser-Shield II tube (Medtronic), was removed from the commercial marketplace in 2016 after cases of airway fires were reported as a result of feature deficiencies in the product (FDA MAUDE Database review). Since the demise of the Laser-Shield II tube, alternatives such as the Mallinckrodt laser tube and handmade reinforced tubes have been utilized, although shortcomings in design and features have made these options less appealing to practicing Otolaryngologists. Creating a laser-safe endotracheal tube is critical for safe upper airway surgery. This paper evaluates new technologies, materials, and technical innovations in endotracheal tubes that may advance patient safety in laser-assisted Otolaryngology procedures.

STUDY TYPE

This paper evaluates new technologies, materials, and technical innovations in endotracheal tubes that may advance patient safety in laser-assisted Otolaryngology procedures.

METHODS

First, this article reviews the background of laser surgery in Otolaryngology and the consequent risk of surgical fire with resultant development of laser-resistant endotracheal tubes and commercial availability. Next, a review of claims and national database review of product failures related to previous laser-resistant endotracheal tubes is performed through the FDA MAUDE database. This includes an evaluation of cases: review of techniques in laser airway surgery including spontaneous ventilation, decreased O2 concentration, currently available endotracheal tubes including "handmade" fixes for perceived safety risks, and determination of failure points for previous laser-resistant endotracheal tubes. Third, the paper reviews the requested features of an "ideal" laser-resistant endotracheal tube. Finally, the paper reviews failure testing from an initial, unsuccessful attempt at material development and the consequent development of alternative technologies that address failure points from previous endotracheal tubes and addresses requested features with a detailed analysis of FDA-approval required testing. Extensive lab testing of the new tube predicts a significant reduction of risk in vivo with inability to perforate the shaft or cuff of the tubes under standard working conditions.

RESULTS

While no iteration of a laser-resistant endotracheal tube is entirely laser safe, advances in technology can improve the safety profile of these devices. The new tube contains a double cuff, a soft and flexible shaft to minimize laryngeal insertion trauma, a smooth external surface, a tight-to-shaft balloon, and methylene blue dye in the cuff to alert the user to inadvertent penetration. These characteristics were the most requested by laryngologists in the development of a new laser-resistant tube. The newest endotracheal tube brings the features most requested by Otolaryngologists in a laser-resistant tube, and improves the safety profile over previous tubes.

CONCLUSION

Development of a new endotracheal tube represents an advancement in safety for the Otolaryngologist in laser airway surgery. Understanding the previous history and the science behind surgical fire formation is essential in advancing safety for patients in the future.

LEVEL OF EVIDENCE

N/A Laryngoscope, 134:S1-S12, 2024.

Surgical Fires in Otolaryngology: A Systematic and Narrative Review

Objective

To bring attention to the epidemiology, prevention, management, and consequences of surgical fires in otolaryngology by reviewing the literature.

Data Sources

PubMed, EMBASE, Web of Science, and Scopus.

Review Methods

Comprehensive search terms were developed, and searches were performed from data source inception through August 2016. A total of 4506 articles were identified; 2351 duplicates were removed; and 2155 titles and abstracts were independently reviewed. Reference review was also performed. Eligible manuscripts described surgical fires involving patients undergoing otolaryngologic procedures.

Results

Seventy-two articles describing 87 otolaryngologic surgical fire cases were identified. These occurred during oral cavity or oropharyngeal procedures (11%), endoscopic laryngotracheal procedures (25%), tracheostomies (36%), “other” general anesthesia procedures (3%), and monitored anesthesia care or local procedures (24%). Oxidizing agents consisted of oxygen alone (n = 63 of 81, 78%), oxygen and nitric oxide (n = 17 of 81, 21%), and room air (n = 1 of 81, 1%). The fractional inspired oxygen delivered was >30% in 97% of surgical fires in non–nitrous oxide general anesthesia cases (n = 35 of 36). Laser-safe tubes were used in only 12% of endoscopic laryngotracheal cases with endotracheal tube descriptions (n = 2 of 17). Eighty-six percent of patients experienced acute complications (n = 76 of 87), including 1 intraoperative death, and 22% of patients (n = 17 of 77) experienced long-term complications.

Conclusion

Surgical fires in otolaryngology persist despite aggressive multi-institutional efforts to curb their incidence. Guideline recommendations to minimize the concentration of delivered oxygen and use laser-safe tubes when indicated were not observed in many cases. Improved institutional fire safety practices are needed nationally and internationally.

A randomized controlled trial of factors influencing fire occurrence during laser surgery of cadaveric rodents under simulated mask anesthesia

OBJECTIVE

To determine whether face mask fit during anesthesia affects the occurrence of fire episodes during laser surgery in nonintubated cadaveric rodents under volatile anesthesia.

DESIGN

Adaptive single-center randomized controlled trial with an interim analysis.

SAMPLE

100 dead rats intended for animal consumption.

PROCEDURES

Rat carcasses were randomly allocated to undergo simulated anesthetic procedures with 2 face masks: open mask versus tight-fitting mask. Under volatile anesthesia, 4 cutaneous surgeries were performed (skin biopsies at 3 different sites and resection of a pinna) by means of a diode laser on each carcass. A single interim analysis of 50 rats was planned a priori to drop an arm of the study in the case of a highly significant difference in the incidence of fire events. Surgeries would have continued with the other face mask until completion of the study. Univariate and multivariate analyses were performed.

RESULTS

Overall, 25 surgeries were performed with open face masks and 75 with tight-fitting masks. During 400 surgical procedures on 100 rat carcasses, 11 (11%; 95% confidence interval, 5.62% to 18.83%) fire events occurred. Ten fire events occurred with the open masks, and 1 fire event occurred with the tight-fitting masks (relative risk, 30.0; 95% confidence interval, 4.0 to 222.8). All of the fire events occurred on different carcasses when cheek skin biopsy was performed. Procedure time, body weight, and surgeon did not significantly concur in the prediction of fire events.

CONCLUSIONS AND CLINICAL RELEVANCE

Modification of open masks by the addition of a latex diaphragm significantly reduced the occurrence of fire ignition during laser surgery. Results suggested that open masks should not be used for laser surgery of nonintubated rodents during volatile anesthesia. Additionally, results indicated that surgical lasers should be avoided for facial surgery of nonintubated anesthetized rodents, even if tight-fitting masks are used.

Hazard of CO₂ laser-induced airway fire in laryngeal surgery: experimental data of contributing factors

In carbon dioxide (CO2) laser surgery of the larynx, the potentially dangerous combination of laser-induced heat in an oxygen-enriched atmosphere typically occurs when jet ventilation is used or due to an insufficiently blocked endotracheal tube. Until now, no limitations for safe oxygen concentrations or laser intervals have been established. The aim of this study was to investigate and quantify the factors that may contribute to an airway fire in laryngeal laser surgery. Fat, muscle and cartilage were irradiated with a CO2 laser at 2, 4, 6 and 8 W in five different oxygen concentrations with and without smoke exhaustion. The time to ignition was recorded for each different experimental setup. Fat burnt fastest, followed by cartilage and muscle. The elevation of laser energy or oxygen concentration reduced the time to inflammation of any tissue. The elevation of oxygen by 10 % increases the risk of inflammation more than the elevation of laser power by 2 W. Under smoke exhaustion, inflammation and burning occurred delayed or were even inhibited at lower oxygen concentrations. Lasing in more than 50 % oxygen is comparatively dangerous and can cause airway fire in less than 5 s, especially when laser energies of more than 5 W are applied. In equal or lower than 50 % oxygen, an irradiation interval of 5 s can be considered a comparatively safe time limit to prevent inflammation in laryngeal laser surgery. Smoke exhaustion should always be applied.

Practice advisory for the prevention and management of operating room fires: an updated report by the American Society of Anesthesiologists Task Force on Operating Room Fires

Supplemental Digital Content is available in the text.

Acute and chronic changes in the subglottis induced by graded carbon dioxide laser injury in the rabbit airway

OBJECTIVE

To investigate the repair process following carbon dioxide laser injury to the upper airway mucosa (UAM) during the development of chronic subglottic stenosis (SGS).

DESIGN

Animals were assigned to either sham control (cricothyroidotomy only) or injured (cricothyroidotomy and posterior subglottic laser) groups using various carbon dioxide laser exposures (8, 12, and 16 W) for 4 seconds.

SUBJECTS

Twenty-four New Zealand white rabbits.

INTERVENTIONS

The subglottis was approached via cricothyroidotomy. Sham control airways were immediately closed, whereas injured airways were subjected to graded carbon dioxide laser exposures prior to closure. Airways were endoscopically monitored preoperatively, postoperatively, and on postoperative days 7, 14, 28, 42, 56, 70, and 84. Animals were killed at 14 and 84 days. Subglottic tissue was harvested for histologic evaluation (reepithelialization, extracellular matrix, vascularity, and inflammation).

MAIN OUTCOME MEASURES

Endoscopic visualization and histologic analysis.

RESULTS

(1) Increases in UAM thickness (up to 5 times the thickness of normal mucosa) were observed but were limited primarily to the lamina propria. The mucosal epithelium regenerated without chronic changes. Focal areas of cartilage repair were encountered acutely after injury and to a greater extent in the chronic phases of repair. (2) Acutely, the thickened lamina propria comprised poorly organized extracellular matrix components and demonstrated increases in blood vessel size and number. (3) Histologic changes present in the acute phase only partially resolved in progression to chronic SGS. Chronic SGS was characterized by thick collagen fiber bundles extending into the remodeled subglottic cartilage.

CONCLUSIONS

The carbon dioxide laser induces acute changes to lamina propria architecture and vascularity that persist chronically. Elucidating responsible signaling pathways may facilitate the development of therapeutic agents to prevent or reduce the formation of SGS.

Entflammungs- und Brandverhalten von biologischem Gewebe bei In-vitro-Bestrahlung mit dem CO2-Laser

BACKGROUND

Laser surgery in endoscopy has greatly enhanced the surgical armamentarium for treating various laryngeal and hypopharyngeal disorders, but harbours a risk of tissue ignition and inflammation of surgical and anaesthetic instrumentation. However, even if non-inflammable material is used, there is still a residual fire hazard from endogenous tissue that may develop an ignitable aerosol (so-called laser smog) as an effect of laser irradiation. The aim of this study was to investigate how tissue carbonisation and vaporisation contributes to the risk of airway fire.

METHODS

For the simulation of gas accumulation in the hypopharynx and larynx following the European standard ISO-11990, a cylindrical steel chamber with an open and a closed end has been used to simulate the operative setting. Pork meat chunks with a tissue composition similar to the larynx and hypopharynx such as fat, muscle, cartilage and bone were introduced into this chamber. Ventilation was achieved through jet ventilation with disposable, non-inflammable laser jet catheters. The tissue was then repeatedly exposed to a laser beam in super-pulse mode (pulse rate 250 Hz) with various intensities and exposure lengths at an impact angle of 75 degrees. The laser intensity was varied from 2 to 15 W. The type, duration, intensity and incidence of tissue ignition were recorded and analysed.

RESULTS

The degree of tissue ignition correlated with laser intensity. Low laser intensity caused spark formation whereas high intensity resulted in sustained tissue fire. The type of tissue had an impact on ignition intensity thereby showing lower ignition thresholds and higher ignition susceptibility in fat-containing tissue compared to muscle. The most important factor for occurrence of tissue ignition was the chamber oxygen concentration which displayed an inverse correlation with the time until tissue ignition. Oxygen concentrations of 35% led to tissue ignition in 42 s, 40% oxygen in 20 s. Oxygen concentrations higher than 60% resulted in immediate tissue ignition.

CONCLUSIONS

Despite the use of non-inflammable materials in endoscopic laser surgery of the upper airway and hypopharynx, the risk of tissue ignition remains due to the inflammable laser smog which is easily ignited in an oxygen-rich environment. Hence to minimise this risk, we recommend using oxygen concentrations lower than 40%, low laser intensities (<6 W) and limiting continuous laser activation to periods shorter than 10 s.

Tracheostomy Tube Ignition During Microlaryngeal Surgery Using Diode Laser: A Case Report

Ignition of the tracheal tube during laser microlaryngeal surgery under general anesthesia is an uncommon complication with potentially serious consequences. We present here a case of a patient with glottic stenosis following endotracheal intubation, who experienced this potentially catastrophic combustion during endoscopic arytenoidectomy, using a diode laser under general anesthesia via 60% FiO2, with an airway fire occurring at the tracheostomy tube and causing tubal damage and obstruction. The anesthetic connecting tube was immediately disconnected and the tracheostomy tube replaced. No adverse consequences to this patient's upper airway were noted during follow-up visits. Higher oxygen concentrations, the presence of combustibles, and the narrowness of the surgical field during endolaryngeal diode laser surgery are risk factors for airway fires.

Value of endotracheal tube safety in laryngeal laser surgery

BACKGROUND AND OBJECTIVES

Due to the increased popularity of laryngeal laser therapy, surgeons and anesthesiologists are inevitably confronted with questions concerning the choice of the most efficient endotracheal tube (ETT) for laryngeal laser surgery, especially with regard to possible endolaryngeal tube fires, or combustions. The purpose of this study was to determine the current practice in endolaryngeal laser surgery in Germany.

STUDY DESIGN/MATERIALS AND METHODS

A questionnaire was sent to 152 ENT Departments in Germany, care was taken that the responders could send back the questionnaire anonymously. Among other questions the participants were asked for the number of lasersurgical treatments of the larynx performed in the past, the usual type of ETTs in use, whether other safety precautions were taken during CO2 laser surgery of the larynx and for intraoperative complications like tube ignition, fires or combustions.

RESULTS

Eighty six of the 152 addressed ENT departments replied. In laryngeal laser surgery, 59/86 departments regularly use special laser tubes in daily routine (74.5%). In about 20,000 lasersurgical procedures, 15 incidents of ETT fire have been reported. In six of the reported 15 cases a tube fire occurred despite the fact that special laser tubes had been utilized.

CONCLUSIONS

The present study could demonstrate that the use of special laser tubes does not necessarily protect against ETT fire. Thus, even when using special laser tubes other safety measures should be taken. In view of the maximum safety for the patient it has to be stated, that the safety during surgery correlates definitely with the experience of the surgeon. The weakest point of ETTs is usually situated in the cuff region.

Airflow through the auxiliary line of the laser fiber prevents ignition of intra-airway fire during endoscopic laser surgery

BACKGROUND AND OBJECTIVES

Ignition accidents during bronchoscopic laser irradiation have occasionally been reported, but the mechanisms responsible for the ignition accidents are not fully understood. We examined causative factors including ignition site, oxygen concentration, and role of airflow through the laser fiber.

STUDY DESIGN/MATERIALS AND METHODS

Porcine muscle tissue was placed in a bottle and irradiated by laser under various conditions. Also, a piece of porcine muscle was wedged in a main bronchus of the isolated porcine lungs and irradiated by laser in the same way.

RESULTS

Flashing occurred on the tissue exposed to the laser, and this flashing reached the ignition when the oxygen concentration was above 30%. Increasing airflow through the laser fiber prevented the ignition even at an oxygen concentration at 100%.

CONCLUSIONS

In laser irradiation, the tissue exposed to the laser can be the ignition site of fire. Increasing airflow through the laser fiber was an effective technique to prevent airway fire.

Anesthesia for microlaryngeal surgery: the case for subglottic jet ventilation

Although the techniques for surgery on the endolarynx using suspension and the operating microscope have been fully developed, the safest, and least obtrusive anesthetic technique has yet to be manifested, as evidenced by more than 200 references to anesthesia for microlaryngoscopy in the world literature. This study reviews the physiology, physics, and problems of each anesthetic technique. In light of this review, animal and human studies are reported demonstrating the utility and safety of subglottic ventilation when provided with proper monitoring using an automatic ventilator. A modified Ben-Jet tube is reported, which has a 1-mm ID channel to monitor PCO2 and tracheal pressure. This self-centering 3.0-mm tube, which extends 6 to 8 cm below the glottis, is unobtrusive for the surgeon. The subglottic tube, which is much less likely to be malaligned, is much more acceptable to the anesthesiologist. Anesthesia, by intravenous sedation, utilizes neuromuscular blockade while ventilating through the jet tube powered by an automatic ventilator with an automatic shutdown feature attached to the monitor tube to prevent inadvertent barotrauma. The third phase of this study compared fluoroplastic, used in a prototype jet ventilation tube, with 6-mm Silastic, Red Rubber, and polyvinyl chloride (PVC) tubes when struck by maximum power of CO2, Nd-YAG, and K-532 lasers. The test was performed in a closed chamber in which concentrations of oxygen and nitrogen were controlled. Although damaged by the CO2 laser beam, the fluoroplastic tubes did not continue burning when the laser was turned off in 100% oxygen, even when coated by blood. The other three tubes continued to burn in 23% oxygen. Neither the KTP nor Nd-YAG laser damaged the Teflon tube, while they ignited a sustained flame in 30% oxygen. This study supports the use of fluoroplastic for a laser safe jet ventilation tube. It also demonstrates the danger of tube fires, even in low oxygen concentrations, when using Silastic, rubber, and PVC tubes in laser laryngeal surgery. There was no difference in the flammability of Silastic, rubber or PVC when struck by these lasers in this study. For these reasons, subglottic ventilation using a fluoroplastic, monitored, self-centering, subglottic, jet ventilation tube driven by an automatic ventilator with a shutdown feature, in the event of excessive pressure buildup, is proposed for anesthetizing healthy patients undergoing suspension microlaryngoscopy, and who have no airway obstructing lesion. A large tube with inflatable cuff is indicated when a supraglottic lesion may obstruct the airway.

The resistance to carbon dioxide laser ignition of a new endotracheal tube: Xomed Laser-Shield II

STUDY OBJECTIVE

To assess the resistance of a new endotracheal tube to penetration and ignition by a carbon dioxide (CO2) laser at a clinically relevant power setting.

DESIGN

An unblinded, in vitro trial simulating clinical conditions.

SETTING

The operating room at a university medical center.

PATIENTS

None.

INTERVENTIONS

A CO2 laser at 20W with a beam diameter of 1 mm was directed onto the Xomed Laser-Shield II at several points: both perpendicular and tangential to the portion of the tube covered by the protective wrap, to the unwrapped silicone tubing just proximal to the cuff, to the cuff filled with saline and methylene blue, and to the unwrapped silicone tubing distal to the cuff. Trials were performed with or without supplemental oxygen (O2) blown onto the study site and with a 6 L/min flow through the tube containing one of four concentrations of O2 in O2-air admixtures: 21%, 30%, 40%, and 100%.

MEASUREMENTS AND MAIN RESULTS

Under all conditions, the laser did not penetrate the protective wrap, but the overlying polytetrafluoroethylene (Teflon) sheet was vaporized to an area equal to the size of beam application. The cuff was penetrated by the laser within 5 seconds. The unprotected silicone protein of the tube was penetrated by the laser in approximately 5 seconds, and time to formation of a blowtorch phenomenon shortened with increasing the percentage of O2 flowing through the tube.

CONCLUSIONS

The protective coating of the Xomed Laser-Shield II is laser-resistant, but the unprotected silicone proximal and distal to the cuff is laser-vulnerable and can, under certain conditions, promote a blowtorch phenomenon. This tube would be acceptable for use in oral and pharyngeal laser surgery, but we recommend its use only in well-ventilated areas, out of concern for exposure to the products of the pyrolysis of Teflon, specifically the development of polymer-fume fever.

Ventilatory complications of carbon dioxide laser laryngeal surgery

STUDY OBJECTIVE

To evaluate complications associated with ventilatory techniques accompanying endolaryngeal carbon dioxide laser surgery.

DESIGN

Retrospective survey of the Society of Academic Anesthesia Chairmen.

SETTING

Operating room at an urban medical center.

PATIENTS

Data from 15,701 patients were analyzed.

MEASUREMENTS AND MAIN RESULTS

Twenty-six percent of patients were ventilated with Venturi jet ventilation and the rest through an endotracheal tube. Reported complications were classified as ventilation related and ventilation unrelated, as well as by severity. A total of 49 complications occurred in the Venturi jet group (1.2%). Of these complications, 24 were ventilation related (0.58%) and 18 were serious or life threatening (0.43%). There were no deaths in this group. Ventilation through an endotracheal tube was associated with a lower frequency of overall complications (0.36%), ventilation-related complications (0.15%), serious or life-threatening complications (0.15%), and serious or life-threatening ventilation-related complications (0.11%) (p less than 0.001). However, there were eight airway fires in this latter group, one resulting in a fatality.

CONCLUSIONS

No clear choice of ventilatory technique is supported by this survey, but teamwork and experience give the best results.

Tubeless anaesthesia for microlaryngeal surgery

An anaesthetic technique for laryngeal microsurgery is described and evaluated using intravenous propofol infusion and topical lignocaine with the patient breathing spontaneously without an endotracheal tube. Eighty adult patients divided into two groups according to their ASA status (Group A; 58 ASA I and II; Group B; 22 ASA III and IV) were analysed. Operating conditions were good in all but one case. Good anaesthesia was achieved in about 70% of patients. The requirement for propofol was less in Group B. Blood pressures decreased significantly following induction (P less than 0.001) but returned towards the preoperative values after ten minutes in Group A patients whereas the recovery was slower in Group B. Apnoea occurred on induction in about 40% of patients overall. PaCO2 showed a similar small increase in both groups. Oxygenation was adequate. The results show that propofol as an infusion in this simple tubeless technique is satisfactory. As the technique was considered potentially hazardous in those patients with upper airway obstruction, such patients were not included in this study.

Anesthetic technique for safe laser use in surgery

The use of lasers has simplified, shortened, and made less traumatic many surgical procedures. It has also increased the range of conditions amenable to treatment in all of the surgical specialties. There are, however, potentially serious hazards associated with the surgical use of lasers. The most serious hazards are explosions and fire, particularly during surgery on the airway, where flammable material, i.e., the endotracheal tube, high oxygen concentrations, and the laser, which is a high energy ignition source, are in close proximity. This report deals with techniques of anesthesia delivery that minimize the risks to the patient and operating room environment consequent on laser use in the airway. Laser use elsewhere in or on the body is associated with no greater danger than the use of electrocautery and requires no special anesthetic adaptation.

High incidence of CO2 laser beam contact with the tracheal tube during operations on the upper airway

Polyvinyl chloride tracheal tubes from 50 consecutive CO2 laser operations of the larynx and trachea were collected after tracheal extubation. In all cases, the helium protocol for laser operations was used, which includes the following: helium in the anesthetic gas mixture at 60% or more during laser resection (FIO2 less than or equal to 0.4); tracheal intubation with plain, unmarked polyvinyl chloride tubes; laser power density less than or equal to 1,992 W/cm2; and laser bursts of less than or equal to 10-second duration. No tracheal tube fires or airway burns occurred. The polyvinyl chloride tubes were examined for marks caused by the laser, and cuffed tubes were tested for cuff viability. Of the 50 tubes examined, 18 were noncuffed and 32 were cuffed. Although most contacts did not penetrate the tubes, 58% of the tubes showed evidence of contact with the laser as a brown mark on the tube or as a cuff leak. Cuffed tubes were more likely to incur laser contact (69%) than noncuffed tubes (39%), a significant difference (p = 0.04). Most of the cuffed tubes that came in contact with the laser sustained damage at the cuff (77%). It was concluded that the risk of tracheal tube contact with a laser beam is at least 1 in 2, that cuffed tubes are more likely to be hit with a laser beam than noncuffed tubes, and that cuffed tubes that are hit usually sustain damage to the cuff. Because no fires occurred in this series despite frequent laser contact with the tube, these data indicate that the helium protocol helps to prevent polyvinyl chloride tube fires.

Anaesthesia for carbon dioxide laser laryngeal surgery in infants. A new tracheal tube

Problems associated with the presence of a tracheal tube during anaesthesia for infant laryngeal surgery using the carbon dioxide laser are described. This paper discusses alternatives and describes an effective anaesthetic technique and a new tracheal tube.

Safe anesthesia for endoscopic laryngeal laser surgery

Anesthesia safety for endoscopic laryngeal laser surgery has been a major limiting factor for laser applications in the larynx and the hypopharynx. Several anesthesia techniques have been proposed and each technique appears to have its own limitations. This paper will deal with the distinct advantages offered by the malleable copper tube which is used for delivery of the open Venturi system anesthesia for endoscopic laser surgery. A retrospective study of 100 patients who have undergone this modality of anesthesia at our institution will be presented. Our conclusion from this study shows clearly the superiority of the copper tube over the conventional aluminium-foil-wrapped endotracheal tube in safety and the exposure of the larynx during surgery.

Incendiary characteristics of a new laser-resistant endotracheal tube

Endotracheal tube fires are the most frequent complication of laser surgery of the larynx. We investigated the incendiary characteristics of a new laser-resistant endotracheal tube, compared to polyvinyl chloride (PVC) and red rubber (RR) tubes, with different gas mixtures. A CO2 laser was focused on each tube and the probability of fire was assessed with oxygen fractions (FiO2) of 30%, 40%, 50%, 70%, and 100%, the balance being N2 or N2O. The laser-resistant tube could not be penetrated by a single laser pulse, regardless of laser energy or gas composition. PVC and RR tubes were readily ignited, the probability of ignition being related to oxygen concentration and laser energy. Nitrous oxide readily supported combustion. We suggest that laser surgery of the larynx can be most safely performed with a laser-resistant endotracheal tube and with gas mixtures containing the minimal safe O2 concentration (without nitrous oxide).

Metal tube anaesthesia for ear, nose and throat carbon dioxide laser surgery

Tracheal tube anaesthesia in ear, nose and throat surgery using the carbon dioxide laser is reviewed. The development of metal tubes and techniques is described.

High frequency ventilation through a small catheter for laser surgery of laryngotracheal and bronchial disorders

One-lung and two-lung high frequency ventilation (HFV) through a 2-mm internal diameter catheter was evaluated in 22 patients during endoscopic laser excision of stenotic lesions of larynx, trachea, and bronchi. High frequency ventilation at 80 to 250 breaths per minute using air during two-lung HFV and using air-oxygen at an inspired oxygen concentration of 25% during one-lung HFV maintained adequate alveolar ventilation and oxygenation in all patients. The use of HFV through a catheter allowed continuous control of ventilation and provided maximal surgical exposure for endoscopic laser surgery. The continuous outflow of HFV gases through the endoscope also prevented lung contamination with blood and debris. The potential of HFV polyvinylchloride catheter ignition by laser was also evaluated in the laboratory during continuous flow of air-oxygen and oxygen-nitrous oxide. The laser ignited polyvinylchloride tubes in all the mixtures of oxygen and nitrous oxide within 3 to 7 seconds. Oxygen at 30% mixed with nitrogen 70% was safe and all such tubes were not ignited by the laser. The ability of HFV to provide adequate oxygenation during endoscopic laser surgery using air-oxygen at an FiO2 below 30% also avoids the hazard of catheter and airway fire.

Injuries to the bronchi and lungs caused by laser-ignited endotracheal tube fires

A CO2 laser attached to an operating room microscope was used to produce extraluminal and intraluminal ignition of various endotracheal tubes in dogs. Extraluminal ignition was produced in Silastic and red rubber endotracheal tubes. The red rubber tube ignited before the tube lumen was penetrated. The Silastic tube failed to ignite while the cuff was inflated. When the cuff was deflated, ignition occurred before the lumen was penetrated. No lung or bronchial injuries were detected in the red rubber or Silastic endotracheal tube extraluminal fires. Intraluminal fires were produced in Silastic, red rubber, and polyvinylchloride (PVC) endotracheal tubes. Microscopic examination of the bronchi and lungs revealed severe injuries in dogs intubated with the PVC and red rubber endotracheal tubes. No injuries to the bronchi and lungs were detected in the Silastic tube group, although the potentially toxic effects of silica ash require further investigation.

Complications of CO2 laser surgery of the aerodigestive tract: experience of 4416 cases

The CO2 laser was first introduced for surgery of the aerodigestive tract in 1971. Since that time, great advances in application have been made in both the adult and pediatric population. Recent reports of isolated complications have appeared in the literature. However, a realistic complication rate in a large series of patients has yet to be reported. This report relates the combined experience of the authors in a total of 4416 cases during the 11-year period from 1971 to 1982. There were nine instances of complications, representing a complication rate of 0.2%. These complications provided a unique learning experience for the authors, and led to the establishment of certain basic principles that should be followed in all laser operations. This survey indicates that the CO2 laser is a safe, extremely useful surgical modality in the aerodigestive tract.

CO2 laser in otolaryngology-head and neck surgery: a retrospective analysis of complications

A retrospective review was conducted of all patients undergoing CO2 laser surgery by members of the Department of Otolaryngology-Head and Neck Surgery at Northwestern University Medical School from January 1, 1980 through December 31, 1981; 204 cases were identified and all are included in this report. Early in our department's experience with laser surgery, an endotracheal tube fire occurred. This incident precipitated a departmental review of complications associated with the use of the CO2 laser and resulted in the formulation of a laser safety protocol. All patients in this group were treated under the directives of this protocol; the operative complication rate was low. This retrospective analysis of complications associated with the use of the CO2 laser under a strictly applied protocol demonstrates the relative safety associated with judicious use of this instrument.

Comparison of tracheal damage from laser-ignited endotracheal tube fires

Studies were undertaken by the Departments of Otolaryngology-Head and Neck Surgery and Anesthesiology at Northwestern University Medical School and the Medical College of Wisconsin (Milwaukee) to compare the potential for tissue injury to the trachea and lungs of canines. Polyvinylchloride (PVC), Rusch red rubber, and silicone tubes were tested. The effects of an intraluminal tube fire on the larynx and trachea were documented with laryngeal and bronchoscopic photographs taken immediately postburn and at the time of sacrifice six hours later. The most severe burns were associated with the PVC tube. Silica ash was seen in the airway after the silicone tube fires and raises the possibility of future problems with silicosis. Histological examination of the trachea showed acute injury in all of the animals; specimens from the dogs with the PVC tube fires demonstrated the most severe cellular damage.

A complication of the use of the laser in ENT surgery

A case is reported of severe epistaxis resulting from the use of an aluminium foil-wrapped nasotracheal tube during laser surgery to the uvula.

Heat sink protection against lasering endotracheal cuffs

The ignition of an endotracheal cuff by CO2 laser impaction has proved troublesome in several ignition sequences. Metal foil tape wrapped around the shaft of the tube will provide adequate protection for it, but the tape does not extend to the thin-walled cuff. When normal saline solution is used instead of air to fill the cuff, heat is rapidly conducted away from the wall and the cuff is prevented from reaching its kindling temperature. If penetration should occur, a fine jet of saline solution instantaneously sprays the field, extinguishing any early combustion. The reaction time of the surgeon or an assistant is not a factor in prevention of thermal injury, no new equipment is required and preparation time is minimal.

Incendiary characteristics of endotracheal tubes with the carbon dioxide laser. An experimental study

The ignition characteristics of the American Hospital, Portex, polyvinyl chloride, and red rubber tracheal tubes commonly available have been evaluated using a standard carbon dioxide laser. The added hazard of the increased combustibility of the impregnated line on endotracheal tubes and the hazard of commonly utilized anesthetic or lubricating materials are discussed. The safety limits which experimentally, indicate levels of energy and laser burst time which seem to preclude the hazard of ignition are outlined. The potential danger of postburn bronchiolitis is noted, along with appropriate treatment.

Complications of CO2 laser surgery of the larynx

Since the introduction of CO2 laser surgery, surgeons have stressed the importance of protecting nontarget structures from errant irradiation. Although striking areas outside the intended field may inflict little or no damage, irradiating an exposed endotracheal tube may result in an endotracheal fire. Recent experience with a case of endotracheal tube ignition led to reevaluation of those factors associated with this serious complication. In an attempt to determine the best endotracheal tube to use during laser surgery of the larynx, the flammability of polyvinyl chloride and red rubber endotracheal tubes was compared. Several factors were noted to contribute to the potential hazard of endotracheal tube ignition. Since red rubber tubes are less flammable, they should be used during laryngeal CO2 laser surgery.