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Anesthesia & Analgesia:
doi: 10.1213/ANE.0000000000000133
Technology, Computing, and Simulation: Technical Communication

Mitigating Operating Room Fires: Development of a Carbon Dioxide Fire Prevention Device

Culp, William C. Jr MD; Kimbrough, Bradly A.; Luna, Sarah AA; Maguddayao, Aris J. AA

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Author Information

From the Department of Anesthesiology, Texas A&M University Health Science Center College of Medicine, Scott & White Hospital, Temple, Texas.

Accepted for publication January 6, 2014.

Funding: This article is supported, in part, by the National Science Foundation (Arlington, Virginia) under grant no. 0855343; the Texas A&M University College of Medicine Undergraduate Research Award (College Station, Texas); the Scott & White Resident Mentorship Award, and by institutional, departmental, and investigator sources.

Conflict of Interest: See Disclosures at the end of the article.

Reprints will not be available from the authors.

Address correspondence to William C. Culp, Jr., MD, Department of Anesthesiology, Texas A&M University Health Science Center College of Medicine, Scott & White Memorial Hospital, 2401 South 31st St., Temple, TX 76508. Address e-mail to wculp@sw.org.

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Abstract

Operating room fires are sentinel events that present a real danger to surgical patients and occur at least as frequently as wrong-sided surgery. For fire to occur, the 3 points of the fire triad must be present: an oxidizer, an ignition source, and fuel source. The electrosurgical unit (ESU) pencil triggers most operating room fires. Carbon dioxide (CO2) is a gas that prevents ignition and suppresses fire by displacing oxygen. We hypothesize that a device can be created to reduce operating room fires by generating a cone of CO2 around the ESU pencil tip. One such device was created by fabricating a divergent nozzle and connecting it to a CO2 source. This device was then placed over the ESU pencil, allowing the tip to be encased in a cone of CO2 gas. The device was then tested in 21%, 50%, and 100% oxygen environments. The ESU was activated at 50 W cut mode while placing the ESU pencil tip on a laparotomy sponge resting on an aluminum test plate for up to 30 seconds or until the sponge ignited. High-speed videography was used to identify time of ignition. Each test was performed in each oxygen environment 5 times with the device activated (CO2 flow 8 L/min) and with the device deactivated (no CO2 flow-control). In addition, 3-dimensional spatial mapping of CO2 concentrations was performed with a CO2 sampling device. The median ± SD [range] ignition time of the control group in 21% oxygen was 2.9 s ± 0.44 [2.3–3.0], in 50% oxygen 0.58 s ± 0.12 [0.47–0.73], and in 100% oxygen 0.48 s ± 0.50 [0.03–1.27]. Fires were ignited with each control trial (15/15); no fires ignited when the device was used (0/15, P < 0.0001). The CO2 concentration at the end of the ESU pencil tip was 95%, while the average CO2 concentration 1 to 1.4 cm away from the pencil tip on the bottom plane was 64%. In conclusion, an operating room fire prevention device can be created by using a divergent nozzle design through which CO2 passes, creating a cone of fire suppressant. This device as demonstrated in a flammability model effectively reduced the risk of fire. CO2 3-dimensional spatial mapping suggests effective fire reduction at least 1 cm away from the tip of the ESU pencil at 8 L/min CO2 flow. Future testing should determine optimum CO2 flow rates and ideal nozzle shapes. Use of this device may substantially reduce the risk of patient injury due to operating room fires.

Operating room fires have been recently identified as a key safety problem by many patient advocacy organizations, including The Joint Commissiona, the Emergency Care Research Institute,1 the American Society of Anesthesiologists,2 and the Anesthesia Patient Safety Foundation.b It is estimated that >600 operating room fires occur annually, but due to the threat of liability, litigation, and media attention, the true number of operating room fires is likely greater.3 In addition, operating room fires are listed as one of the top 10 health technology hazards of 2013.4

For a fire to occur, the 3 elements of the fire triad must be present: a fuel source, an oxidizer, and an ignition source. In 90% of claims from operating room fires, the ignition source is the electrosurgery unit (ESU).5 Due to the widespread use of electrosurgery, it is difficult to remove the primary ignition source of operating room fires. Carbon dioxide (CO2) is a commonly available gas used routinely in the operating room environment for insufflation and is also widely used as a commercial fire extinguisher agent. We hypothesized that a device could be created that would modify an ESU pencil such that a protective cone of CO2 gas would encase the active portion of the ESU pencil tip, thereby displacing oxygen and creating a microatmosphere of CO2. This reduction in oxygen concentration around the sparks emanating from the ESU pencil would then reduce the risk of operating room fire.

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METHODS

After obtaining exemption from the local IRB, a divergent nozzle with a maximal inner diameter of 1.16 cm was fashioned from medical grade plastic. This portion of the device was then connected to a CO2 source via silicon tubing and then secured to an ESU pencil (Pencil: Goldline Push Button, ESU: Sabre 2400, Conmed, Utica, NY) such that the active portion of the ESU pencil tip extended past the device by approximately 1 mm, (Fig. 1).

Figure 1
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Flammability testing was then performed by placing a 10 × 3 cm swatch of laparotomy sponge on an aluminum testing rack. The laparotomy sponge was the most flammable of several potential fuels in operating room fires based on prior testing.6 The testing rack was set at a 45° angle and had an open area underneath the test sample to encourage oxygen exposure, thereby maximizing the chance of ignition, as previously described. ESU return pads were replaced by direct connection to the test rack with copper alligator clips. This apparatus was placed in a 46 × 46× 46 cm testing chamber with transparent walls so that the ambient gas composition could be controlled. The fire prevention device was then mated with the ESU pencil and placed in the testing chamber. The ESU pencil was activated at 50 W cut mode while placing the pencil tip on the laparotomy sponge resting on the aluminum test plate. (Typical ESU power settings are 20–40 W cut mode but occasionally will be increased to 50–60 W depending on application.) The ESU was activated for up to 30 seconds or until the sponge ignited. The time of ESU activation until ignition was measured by recording each test with high-speed videography. Time to ignition was defined as the time between initial contact of the tip of the ESU pencil and the time at which a sustainable flame was produced on the laparotomy sponge swatch. Each video was reviewed 3 times to confirm time values, and random samples were measured by the other investigators for confirmation. Tests were conducted in different oxygen concentrations: 19% to 23%, 50% to 60%, and 90% to 100%, as measured by a multi-gas analyzer (Apollo Anesthesia Workstation, Dräger Medical, Lübeck, Germany) connected to the testing chamber.

Five trials were performed with the fire prevention device CO2 flow at 8 L/min, and 5 trials with the CO2 flow off (control). Each set of trials was performed in the 3 oxygen concentrations for a total of 30 tests. Confidence intervals (CIs) were determined by using the Clopper-Pearson exact value, analyzing both individual trials and also pooling the control group data and the device group data. Proportions were compared with a 2 × 2 contingency table design, followed by a 2-tailed Fisher exact test. P < 0.05 was deemed statistically significant.

CO2 concentration mapping was also performed in a separate experiment. The fire prevention device was attached to an ESU pencil and then secured to a ring stand on a table in an upright position. A matrix of 1-cm cubes was fashioned from wire to create an x-, y- z-axis location marker in 3-dimensional space. The pencil was positioned such that the ESU pencil tip just touched the table surface through the middle of the matrix. A high concentration, calibrated CO2 monitor (CM-0006 CO2 Sample Draw Meter, CO2Meter, Inc., Ormond Beach, FL) was then connected to a 20-gauge IV catheter, which was used to sample CO2 concentrations along each discrete point of the 3-dimensional matrix, 1 cm at a time. With 8 L/min of CO2 flowing through the device, CO2 concentrations were sampled. This entire labarotory setup was conducted within a work booth designed to minimize air current contamination.

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RESULTS

Fires were ignited in every control group trial (15/15 trials). The median ± SD [range] ignition time of the control group in 21% oxygen was 2.9 s ± 0.44 [2.3–3.0], in 50% oxygen 0.58 s ± 0.12 [0.47–0.73], and in 100% oxygen 0.48 s ± 0.50 [0.03–1.27]. No fire was observed when CO2 was applied through the device in all concentrations of oxygen (0/15 trials, P < 0.0001; note that data homogeneity permitted data pooling for subsequent analysis) (Figs. 2 and 3). The 95% CIs for the control group in each of 3 oxygen concentrations was 55% to 100%, and for each of the device groups, 0% to 45%. Pooling all control group trials, this CI was 82% to 100%, and pooling all device trials, this CI was 0% to 18%. The exact 95% CI for the absolute reduction in percent risk of ignition is from 76% to 100%. The CO2 concentration at the end of the ESU pencil tip was 95%, while the average CO2 concentration 1 to 1.4 cm away from the ESU pencil tip on the bottom plane was 64% (Fig. 4).

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Figure 3
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Figure 4
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DISCUSSION

Preventing operating room fires is a high priority goal of many patient advocacy organizations. The Anesthesia Patient Safety Foundation and the American Society of Anesthesiologists Task Force on Fire Prevention have published high-quality educational materialsb and recommendations2 to reduce the risk of these fires. Despite these efforts, operating room fires remain a highly visible clinical problem, and a recent study reported an increase in ESU-triggered operating room fire claims over the last 10 years.7 Though recommendations, education, and regulation have raised awareness of operating room fires, the potential for fire still remains. Unfortunately, this heightened awareness has not yet translated into eliminating operating room fires, prompting a need to also address the problem in another way.

Most of these fires occur on the head and neck, largely due to the close proximity to open oxygen sources. Supplemental oxygen is necessary for many patients undergoing sedation, yet this is a key factor in increasing fire risk. Our prototype device attempts to use a routinely available and medically safe gas, CO2, to displace this oxygen away from the active tip of the ESU electrode, removing 1 leg of the fire triad. CO2 is inexpensive and readily available in most operating rooms from either a piped wall source or in tanks commonly used for insufflation. Previous studies have suggested that operating room fires are unlikely to occur if the oxygen concentration around the ignition source is <50%,8 so our initial target goal was to design a device that could generate at least a 50% CO2 concentration within 1 cm of the ESU tip.

Flammability testing of this device used a laparotomy sponge (the most flammable common operating room material tested in a previous study)6 in a super-oxygenated test chamber by using a high power ESU setting. Even under these very flammable conditions, the fire prevention device prevented or suppressed all fires for the 30-second duration of ESU use, while ignition occurred in <0.5 seconds without the device.

Limitations of this prototype device include the size of the divergent nozzle. This may reduce the surgeon’s ability to place the pencil tip within a small cavity, for instance, or through a trocar for laparoscopic application. In addition, the device may reduce some visibility around the ESU pencil tip. This interference may be minimized by using a colorless, translucent, optically neutral material in the device design. Visibility may actually be enhanced as the exiting CO2 pushes away smoke, debris, and blood from the cutting area. The bulk of the connecting CO2 tubing that runs on the outside our prototype device could be internalized within the body of the ESU pencil. Aside from the divergent nozzle tip, the resulting pencil would be very similar in weight and feel to a standard ESU pencil.

An operating room fire prevention device by using CO2 to displace oxygen can effectively prevent ignition by an ESU pencil in a highly flammable in vitro model of fire. This demonstration coupled with CO2 concentration spatial mapping establishes proof of concept for the device. Further testing and development to optimize device shape and characteristics along with optimal CO2 flow rates are justified. Future implementation of such a CO2 fire prevention device may effectively reduce the risk of operating room fires.

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DISCLOSURES

Name: William C. Culp, Jr., MD.

Contribution: The author invented the device, participated in study design, conducted the study, participated in data collection, performed data analysis, and prepared the manuscript.

Attestation: The author approved the final manuscript, reviewed the original study data and data analysis, and attests to the integrity of same. W.C. Culp, Jr., is the archival author.

Conflicts of Interest: The author is considering pursuing commercialization of the concept described by this device but has no other potential conflicts of interest to disclose.

Name: Bradly A. Kimbrough.

Contribution: The author participated in design and conduct of the study, participated in data collection, performed data analysis, and prepared the manuscript.

Attestation: The author approved the final manuscript, reviewed the original study data and data analysis, and attests to the integrity of same.

Conflicts of Interest: The author has no conflicts of interest to declare.

Name: Sarah Luna, AA.

Contribution: The author participated in design and conduct of the study, participated in data collection, performed data analysis, and prepared the manuscript.

Attestation: The author approved the final manuscript, reviewed the original study data and data analysis, and attests to the integrity of same.

Conflicts of Interest: The author has no conflicts of interest to declare.

Name: Aris J. Maguddayao, AA.

Contribution: The author participated in design and conduct of the study, participated in data collection, performed data analysis, and prepared the manuscript.

Attestation: The author approved the final manuscript, reviewed the original study data and data analysis, and attests to the integrity of same.

Conflicts of Interest: The author has no conflicts of interest to declare.

This manuscript was handled by: Maxime Cannesson, MD, PhD.

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FOOTNOTES

a Preventing surgical fires. Sentinel Event Alert 29 (June 24,2003). Available at: http:///www.jointcommission.org/sentinel_event_alert_issue_29_preventing_surgical_fires/. Accessed February 25,2013 Cited Here...

b Prevention and Management of Operating Room Fires. Available at: http://www.apsf.org/resources_video.php. Accessed February 25, 2013 Cited Here...

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REFERENCES

1. . ECRI Institute. New clinical guide to surgical fire prevention. Patients can catch fire-Here’s how to keep them safer. Health Devices. 2009;38:314–32

2. Apfelbaum JL, Caplan RA, Barker SJ, Connis RT, Cowles C, Ehrenwerth J, Nickinovich DG, Pritchard D, Roberson DW, Caplan RA, Barker SJ, Connis RT, Cowles C, de Richemond AL, Ehrenwerth J, Nickinovich DG, Pritchard D, Roberson DW, Wolf GLAmerican Society of Anesthesiologists Task Force on Operating Room Fires. . 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. Anesthesiology. 2013;118:271–90

3. Rinder CS. Fire safety in the operating room. Curr Opin Anaesthesiol. 2008;21:790–5

4. . ERCI Institute 2013 Top Ten Health Technology Hazards. Health Devices. 2012;41:111–24

5. Mehta SP, Bhananker SM, Posner KL, Domino KB. Operating room fires: a closed claims analysis. Anesthesiology. 2013;118:1133–9

6. Culp WC Jr, Kimbrough BA, Luna S. Flammability of surgical drapes and materials in varying concentrations of oxygen. Anesthesiology. 2013;119:770–6

7. Mehta SP, Bhananker SM, Posner KL, Domino KB. Operating room fires: a closed claims analysis. Anesthesiology. 2013;118:1133–9

8. Roy S, Smith LP. What does it take to start an oropharyngeal fire? Oxygen requirements to start fires in the operating room. Int J Pediatr Otorhinolaryngol. 2011;75:227–30

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