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PEDIATRIC ANESTHESIA

An Evaluation of a Virtual Reality Airway Simulator

Richard Rowe, MD, MPH^*, and Ronald A. Cohen, MD

Departments of *Anesthesiology and Diagnostic Imaging, Children’s Hospital Oakland, Oakland; and Departments of Anesthesiology and Radiology, University of California, San Francisco School of Medicine, San Francisco, California

Address correspondence and reprint requests to Dr. Richard Rowe, Department of Anesthesiology, Children’s Hospital Oakland, Oakland, CA 94609. Address e-mail to cho.dr.rwr{at}cho.org

	Abstract

Top Abstract Introduction Materials and Methods Results Discussion References

 
In this research, we sought to test the hypothesis that the AccuTouch^® Flexible Bronchoscopy Simulator (Simulator) is an effective way to teach clinicians the psychomotor skills necessary to use the fiberoptic bronchoscope as an instrument for intubating the trachea of a pediatric patient. Pediatric residents with no prior experience in fiberoptic bronchoscopy were studied. Residents performed fiberoptic intubation on children undergoing general anesthesia. Tapes of these intubations were analyzed for: time to visualization of the carina, and number and time that the bronchoscope tip hit the mucosa. Residents were then trained on the Simulator. Performance of fiberoptic intubation on a subsequent child was compared. Training on the Simulator was the only instruction that the residents received between the two cases. A control group of residents performed two consecutive intubations without training on the Simulator between cases. Residents studied an average of 17 cases, and spent 39 min on the Simulator. Performance was markedly improved after the Simulator. Time to completion of successful intubation with a bronchoscope was reduced from 5.15 to 0.88 min (P < 0.001). The number of times that the tip of the bronchoscope hit the mucosa was reduced from 21.4 to 3.0 (P < 0.001). The amount of time that the resident spent viewing the mucosa decreased from 2.24 to 0.19 min (P < 0.001). The percent of time viewing the channel of the airway increased from 58.5% to 80.4% (P = 0.004). This bronchoscopy simulator was very effective in teaching residents the psychomotor skills necessary for fiberoptic intubation. Significant improvement was seen in time to completion of endotracheal intubation, as well as other performance indicators.

IMPLICATIONS: This research showed that the AccuTouch^® Bronchoscopy Simulator is an effective way to teach the psychomotor skills necessary to intubate the trachea of patients using a fiberoptic bronchoscope. The residents that practiced on the Simulator dramatically improved their skills compared with a control group of residents.

	Introduction

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Fiberoptic laryngoscopy is a very effective, safe, and reliable method for intubating the tracheas of patients with known "difficult airways" (1–4). Although it is easy to teach the didactic part of this technique, the psychomotor skills needed to use this instrument effectively are more difficult to teach. Workshops using plastic mannequins have improved performance in only 35% of participants (5). Our hypothesis is that the AccuTouch^® Flexible Bronchoscopy Simulator (Simulator) by Immersion Medical Systems (Gaithersburg, MD) is an effective tool in teaching clinicians the psychomotor skills necessary to become competent users of the fiberoptic bronchoscope.

Virtual reality (VR) has become an established tool for teaching medical personnel (6–8). Research in laparoscopic surgery simulators has shown a marked improvement in surgical performance, including shorter time to completion of a laparoscopic procedure, less pass-pointing, and more efficient path length (6). A prototype has been reported for a VR program to teach fiberoptic intubation (9). However, there has not been an evaluation of this technology to prove whether it actually improves bronchoscopic performance.

	Materials and Methods

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The Children’s Hospital Oakland (CHO) Research Committee approved the study, and informed consent was obtained from the study participants. Twenty pediatric residents, who were on a 2-wk rotation in the Department of Anesthesiology at CHO, were enrolled. None had prior experience in bronchoscopy. There were 12 residents in the "Simulator" group, and 8 residents in the "Control" group, randomly assigned. All residents performed two fiberoptic intubations on patients during the study. These cases were videotaped and graded. The Simulator group received training on the Simulator between their cases, whereas the Control group did not. There were eight residents randomly assigned to the Control group. These residents followed the same protocol as the group that used the Simulator, except that after their first case they did another intubation without the aid of instruction from the anesthesia faculty or practice on the Simulator. The Control group was designed to discern whether residents could improve their ability in fiberoptic intubation by experience alone. The controls were not paired with the Simulator group. Randomization was done with a coin toss and resulted in more residents in the Simulator group than in the Control group.

The study was designed to be in compliance with our normal standard of anesthetic care. Patients were undergoing a dental procedure in which the dentist had requested placement of a nasal endotracheal tube (ETT) to give access to the entire oral cavity for treatment. All children in the study received midazolam 0.5 mg/kg per os before the induction. The patients received a general anesthetic with halothane, isoflurane, or sevoflurane. After the induction of general anesthesia, the patients had an IV catheter inserted in their arm and a muscle relaxant was administered. Oral intubation (with conventional direct laryngoscopy) was performed to determine the size of the ETT that was the best fit for the patient’s trachea. The patient’s nares were prepped with a vasoconstrictor and local anesthetic, and then suctioned to remove any debris.

The resident was given basic instruction on use of the fiberoptic bronchoscope. All fiberoptic intubations were performed with an Olympus LF-2 or LF-P (Olympus, Lake Placid, NY) or Storz 3.7 mm scope (Storz, Culver City, CA). An appropriate-sized ETT was placed on the bronchoscope. The views through the bronchoscopes were recorded on videotape by using either a Stryker Model 782 Medical Video Camera (Stryker, Kalamazoo, MI) or a Storz Telecam (Storz). Videotapes were later reviewed for time to completion (from the time that the bronchoscope entered the nares until a view of the carina was obtained), number of collisions of the tip of the bronchoscope with the mucosa, amount of time viewing the mucosa, and amount of time viewing the airway. The typical "red out" view that is seen when the tip of the bronchoscope is pressed against the mucosa was calculated as the time viewing the mucosa; if the tip of the bronchoscope was away from the mucosa, it was rated as a view of the airway. After the resident had obtained a view of the patient’s carina with the bronchoscope, the ETT was advanced over the bronchoscope and into the patient’s trachea, and the bronchoscope was removed. Videotapes were scored by anesthesia attendings who were blinded to subject identity and group.

Consistent with our philosophy of care, the residents were allowed a maximum of 4 min to complete the intubation. The patient’s lungs were ventilated via the oral ETT. Once the resident obtained a view of the glottis, the ETT was removed from the glottis. Oxygen saturation of all patients remained >95% during the study. Any resident who exceeded that time limit was given extra verbal or physical assistance to complete the intubation. The attending anesthesiologist also helped residents who asked for assistance during the case. Residents were assigned to appropriate cases with permission of the attending anesthesiologist. Attendings were not randomized, but were blinded concerning resident group status.

Residents in the Simulator group were shown how to use the Simulator but were given no training by an attending anesthesiologist. The residents received their training by interacting with the Simulator. The Simulator consists of a proxy flexible bronchoscope, a robotic interface device, computer with monitor, and simulation software. The bronchoscope is designed to mimic the feel of an actual bronchoscope. The interface device tracks the motions of the bronchoscope and reproduces the forces felt during an actual bronchoscopic procedure. The proximal end of the interface is shaped like a human face with a port to insert the bronchoscope through one of the nasal passages. The bronchoscope tracks the manipulations of the tip control lever, the suction button, and video buttons. In addition, instruments are tracked as they are manipulated in the working channel. This allows for biopsies and other diagnostic and therapeutic procedures to be performed on the Simulator.

The monitor displays computer-generated images of the airway as the user navigates through the virtual anatomy. The images that are used in the Simulator were obtained from helical computed tomography images of patients at CHO. Medical illustrators at Immersion Medical rendered these black and white files so that they resemble the respiratory mucosa that is seen clinically when viewing a patient’s airway with a video bronchoscope. In addition to being rendered anatomically correct, the virtual patient also behaves in a physiologically realistic manner. The patient breathes, coughs, bleeds, and exhibits changes in vital signs. The Simulator provides 4 cases: normal adult, 5-yr-old child, normal neonate, and neonate with Pierre Robin Syndrome.

When the tip of the bronchoscope is passed into the nares of the Simulator’s faceplate, images of the mucosa of the nares are viewed. As the bronchoscope is advanced, it must be directed in the same way as in a clinical setting. The simulation software records the user actions and stores this information in a database. Examples of information that is collected and displayed include: time the case was open, time in "red-out" (bronchoscope against mucosa), number of collisions of the tip of the bronchoscope with the mucosa, and number of attempts to pass through the glottis.

Analysis of variance was performed, and any values of P > 0.05 were reported as not statistically significant. Values were reported as mean with standard deviation.

	Results

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Residents in the Simulator group practiced on an average of 17 cases, and spent 39 min on the Simulator (Table 1). All indicators of intubation performance on patients improved in the Simulator group between the first and second intubations (Table 2). The patients for the study ranged from age 1 to 17 yr. The median age was 5.2 yr in the Simulator group and 4.6 yr in the Control group (P > 0.05). The age frequency of cases is presented in Figure 1.

View larger version (26K): [in this window] [in a new window]   Figure 1. Frequency distribution of age of patients. Sim = Simulator.

The results of the initial Simulator group and the initial Control group showed no significant difference in performance. There was also no significant difference in performance when the results of the initial Control group were compared with the final Control group.

Thirty-nine patients had normal airways by examination. One patient had a history of Apert’s syndrome; however, the attending anesthesiologist evaluated the patient’s airway as normal (and the intubation was completed in <1 min by a resident in the "final" Simulator group). All fiberoptic intubations were successfully completed by the residents within their 2-wk rotation on our service. There was no significant difference in the interval between cases between the two groups. None of the cases had any complications.

	Discussion

Top Abstract Introduction Materials and Methods Results Discussion References

 
This study showed that the Simulator was successful at training residents the psychomotor skills necessary to intubate pediatric patients with a fiberoptic bronchoscope. Residents who had never performed fiberoptic intubation improved dramatically compared with the Control group who showed no significant change between two cases. To assess the user performance, the time from insertion of the bronchoscope into the patient’s nares until a good view of the carina was recorded. This is an objective result that can be obtained from the procedure videotapes. Because most residents took longer than four minutes to complete the intubation, we thought that it was in our standard practice of teaching to give them clues that would help them complete the intubation. We also answered any questions that they might have during the intubation. Because the Control group received similar treatment, the improvement in performance in the Simulator group can therefore be ascribed to the Simulator.

VR is used to teach skills to pilots in flight simulators as well as to clinicians in many areas of medicine (10–16). VR allows the participant to view computer-generated images that are convincingly real. An important aspect of VR is that the clinician must have as close to a real clinical experience as possible. The Simulator creates a realistic and immersive training environment for learning and practicing flexible bronchoscopy. The Simulator was designed to achieve four important features: First, the Simulator uses a bronchoscope that is used in the exact same technique as it is used clinically. Second, the clinician views images of the airways that are the exact architecture of a patient. Third, any movements that the clinician make with the bronchoscope result in the same views of the airway as would be seen in the clinical setting. And last, the bronchoscope gives haptic (or "force") feedback when the tip of the bronchoscope hits the mucosa, or enters the distal bronchi that are smaller than the diameter of the bronchoscope.

The residents were extremely happy with their improvement in such a short period of training on the Simulator. All of the residents rated their experience on the Simulator as very positive: instructive, fun, intuitive, and efficient at teaching. Although there are no standards to compare times of achieving bronchoscopic view of the carina, a time of less than a minute has been considered sufficient to demonstrate satisfactory fiberoptic intubation skills (17).

Anesthesiologists are responsible for the patient’s airway. Maintaining an airway is of paramount importance to the patient’s safety because loss of airway patency can cause irreparable harm within minutes. In the list of reasons for anesthesia-related injuries in the United States, adverse respiratory events cause the most harm (18). A review of the data from the American Society of Anesthesiologists Closed Claims Project showed that there has been a decrease in adverse respiratory events caused by inadvertent esophageal intubations, presumably because of increased monitoring with capnography and pulse oximetry. However, the number of poor outcomes of patients with difficult airways remains the same (19). The American Society of Anesthesiologists Task Force on the Management of the Difficult Airway recommends that clinicians become familiar with various techniques to handle patients with difficult airways (20). The fiberoptic bronchoscope is the method preferred by many anesthesiologists of intubating a patient with a difficult airway because it is the most flexible, least traumatic, least stimulating, and gives the clinician a direct visualization of the airway (1–4). Because patients can rapidly desaturate in conditions of inadequate ventilation, it is essential that the bronchoscopist be able to complete the intubation quickly (21). This study has shown that the Simulator can significantly decrease the time that it takes a resident to complete an intubation.

The number of anesthesia residency programs offering courses in the management of patients with difficult airways is increasing; however, many anesthesiologists still do not have the skills necessary to successfully complete a fiberoptic intubation (22).¹ Two of the most frequently cited reasons that clinicians do not maintain their skills are lack of case frequency and difficulty in learning fiberoptic intubation. The use of the Simulator responds to both of these objections. It is relatively easy to practice on the Simulator and "cases" are always available. Because the Simulator accurately replicates the clinical setting, residents can practice on 20 or 30 virtual cases a day, rather than waiting to experience these cases in the operating room. In this study, we showed that inexperienced residents acquired the needed psychomotor skills in <20 cases. This is consistent with studies that showed that physicians required between 15 and 20 cases to achieve satisfactory skills (17,23,24). The time required to achieve these results was an average of 39 minutes (Table 1).

This was not a research project designed to learn whether this simulator is better than traditional methods of teaching fiberoptic intubation. Because the Simulator poses no risk to any patients, it would be an ideal instructional tool for residents before their first attempt to perform fiberoptic intubation on a patient. However, further studies are needed to evaluate the teaching efficacy of different methods of training. There may have been a "motivation effect" in the Simulator group that improved their results compared with the Control group.

One of the first elements in evaluation of simulation technology is to find whether these instruments can accomplish the goals of teaching. The results of this research have shown that residents can be successfully taught the psychomotor skills of fiberoptic intubation in pediatric patients by using the Simulator.

	Acknowledgments

 
Funding for the development of the Simulator technology was provided by a Technology Transfer Grant, Children’s Hospital Oakland Research Institute, Oakland, CA to Immersion Medical, Inc., Gaithersburg, MD. There were no research funds for this project.

	Footnotes

 
¹ Cooper SD, Benumof JL. Teaching the management of difficult airways: the UCSD airway rotation [abstract]. Anesthesiology 1994;81:A1241.

	References

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Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999