Modeling Fatigue in Manual and Robot-Assisted Work for Operator 5.0.

Fatigue, and many other human performance factors, impact worker wellbeing, and thus production quality and efficiency. Adopting the Industry 5.0 perspective, we propose that integrating human performance models into wider industrial system models can improve modeling accuracy and lead to superior outcomes. Integrating our Worker Fatigue Model as part of their industrial system architect model allowed Airbus, a leading aircraft manufacturer, to more accurately predict system performance as a function of the workforce makeup, which could be a combination of human workers and robots, or a combination of highly experienced and less experienced workers. Our approach demonstrates the importance and value of including human performance models in trade studies for introducing robots on the shop floor, and can be used to include various aspects of human performance in industrial system models to address specific task requirements or different levels of automation.

Validation of the VBLaST pattern cutting task: a learning curve study.

BACKGROUND: Mastery of laparoscopic skills is essential in surgical practice and requires considerable time and effort to achieve. The Virtual Basic Laparoscopic Skill Trainer (VBLaST-PC©) is a virtual simulator that was developed as a computerized version of the pattern cutting (PC) task in the Fundamentals of Laparoscopic Surgery (FLS) system. To establish convergent validity for the VBLaST-PC©, we assessed trainees' learning curves using the cumulative summation (CUSUM) method and compared them with those on the FLS. METHODS: Twenty-four medical students were randomly assigned to an FLS training group, a VBLaST training group, or a control group. Fifteen training sessions, 30 min in duration per session per day, were conducted over 3 weeks. All subjects completed pretest, posttest, and retention test (2 weeks after posttest) on both the FLS and VBLaST© simulators. Performance data, including time, error, FLS score, learning rate, learning plateau, and CUSUM score, were analyzed. RESULTS: The learning curve for all trained subjects demonstrated increasing performance and a performance plateau. CUSUM analyses showed that five of the seven subjects reached the intermediate proficiency level but none reached the expert proficiency level after 150 practice trials. Performance was significantly improved after simulation training, but only in the assigned simulator. No significant decay of skills after 2 weeks of disuse was observed. Control subjects did not show any learning on the FLS simulator, but improved continually in the VBLaST simulator. CONCLUSIONS: Although VBLaST©- and FLS-trained subjects demonstrated similar learning rates and plateaus, the majority of subjects required more than 150 trials to achieve proficiency. Trained subjects demonstrated improved performance in only the assigned simulator, indicating specificity of training. The virtual simulator may provide better opportunities for learning, especially with limited training exposure.

OR fire virtual training simulator: design and face validity.

BACKGROUND: The Virtual Electrosurgical Skill Trainer is a tool for training surgeons the safe operation of electrosurgery tools in both open and minimally invasive surgery. This training includes a dedicated team-training module that focuses on operating room (OR) fire prevention and response. The module was developed to allow trainees, practicing surgeons, anesthesiologist, and nurses to interact with a virtual OR environment, which includes anesthesia apparatus, electrosurgical equipment, a virtual patient, and a fire extinguisher. Wearing a head-mounted display, participants must correctly identify the "fire triangle" elements and then successfully contain an OR fire. Within these virtual reality scenarios, trainees learn to react appropriately to the simulated emergency. A study targeted at establishing the face validity of the virtual OR fire simulator was undertaken at the 2015 Society of American Gastrointestinal and Endoscopic Surgeons conference. METHODS: Forty-nine subjects with varying experience participated in this Institutional Review Board-approved study. The subjects were asked to complete the OR fire training/prevention sequence in the VEST simulator. Subjects were then asked to answer a subjective preference questionnaire consisting of sixteen questions, focused on the usefulness and fidelity of the simulator. RESULTS: On a 5-point scale, 12 of 13 questions were rated at a mean of 3 or greater (92%). Five questions were rated above 4 (38%), particularly those focusing on the simulator effectiveness and its usefulness in OR fire safety training. A total of 33 of the 49 participants (67%) chose the virtual OR fire trainer over the traditional training methods such as a textbook or an animal model. CONCLUSIONS: Training for OR fire emergencies in fully immersive VR environments, such as the VEST trainer, may be the ideal training modality. The face validity of the OR fire training module of the VEST simulator was successfully established on many aspects of the simulation.

Face and content validation of a Virtual Translumenal Endoscopic Surgery Trainer (VTEST™).

BACKGROUND: Natural orifice translumenal endoscopic surgery (NOTES) is an emerging surgical paradigm, where peritoneal access is achieved through one of the natural orifices of the body. It is being reported as a safe and feasible surgical technique with significantly reduced external scarring. Virtual Translumenal Endoscopic Surgical Trainer (VTEST™) is the first virtual reality simulator for the NOTES. The VTEST™ simulator was developed to train surgeons in the hybrid transvaginal NOTES cholecystectomy procedure. The initial version of the VTEST™ simulator underwent face validation at the 2013 Natural Orifice Surgery Consortium for Assessment and Research (NOSCAR) summit. Several areas of improvement were identified as a result, and the corresponding modifications were implemented in the simulator. This manuscript outlines the results of the subsequent evaluation study, performed in order to assess the face and content validity of the latest VTEST™ simulator. METHODS: Twelve subjects participated in an institutional review board-approved study that took place at the 2014 NOSCAR summit. Six of the 12 subjects, who are experts with NOTES experience, were used for face and content validation. The subjects performed the hybrid transvaginal NOTES cholecystectomy procedure on VTEST™ that included identifying the Calot's triangle, clipping and cutting the cystic duct/artery, and detaching the gallbladder. The subjects then answered five-point Likert scale feedback questionnaires for face and content validity. RESULTS: Overall, subjects rated 12/15 questions as 3.0 or greater (60 %), for face validity questions regarding the realism of the anatomical features, interface, and the tasks. Subjects also highly rated the usefulness of the simulator in learning the fundamental NOTES technical skills (3.50 ± 0.84). Content validity results indicate a high level of usefulness of the VTEST™ for training prior to operating room experience (4.17 ± 0.75).

Use of stochastic resonance methods for improving laparoscopic surgery performance.

BACKGROUND: Vibrotactile feedback (VIB) has been utilized in previous research as sensory augmentation to improve performance during minimally invasive surgical tasks. Stochastic resonance (SR), introduced into the human control system as white noise at a subthreshold level, has shown promise to improve the sensitivity of tactile receptors resulting in performance enhancement for sensorimotor tasks. The purpose of this study was to determine whether SR could improve performance (accuracy, speed) in a simulated laparoscopic palpation task. METHODS: Sixteen subjects performed a palpation task using a laparoscopic tool to detect the presence of tumors (compacted felt) embedded in simulated tissue samples (silicone gel) inside a laparoscopic trainer box. Subjects were randomly assigned to one of the four different conditions: (1) SR, (2) VIB, (3) VIB + SR, and (4) Control. The VIB and SR signals were administered via two separate haptic actuators attached to the subjects' dominant upper arms and forearms, respectively. All subjects were presented with 36 tissue samples with no sensory augmentation (Control) to establish baseline, followed by another 36 samples under one of the randomly assigned vibration conditions (SR, VIB, VIB + SR, or Control). RESULTS: Results show a significantly larger improvement in tumor detection accuracy in the SR group compared to the VIB and Control groups. There was no difference in the time to task completion, indicating that there was no speed-accuracy trade-off. CONCLUSIONS: The results have implications for the design of instruments and methods for increasing detection accuracy such as in palpation tasks. This technology could help surgeons better identify tumors located in healthy surrounding tissue.

A systematic review of the effect of distraction on surgeon performance: directions for operating room policy and surgical training.

BACKGROUND: Distractions during surgical procedures have been linked to medical error and team inefficiency. This systematic review identifies the most common and most significant forms of distraction in order to devise guidelines for mitigating the effects of distractions in the OR. METHODS: In January 2015, a PubMed and Google Scholar search yielded 963 articles, of which 17 (2 %) either directly observed the occurrence of distractions in operating rooms or conducted a laboratory experiment to determine the effect of distraction on surgical performance. RESULTS: Observational studies indicated that movement and case-irrelevant conversation were the most frequently occurring distractions, but equipment and procedural distractions were the most severe. Laboratory studies indicated that (1) auditory and mental distractions can significantly impact surgical performance, but visual distractions do not incur the same level of effects; (2) task difficulty has an interaction effect with distractions; and (3) inexperienced subjects reduce their speed when faced with distractions, while experienced subjects did not. CONCLUSION: This systematic review suggests that operating room protocols should ensure that distractions from intermittent auditory and mental distractions are significantly reduced. In addition, surgical residents would benefit from training for intermittent auditory and mental distractions in order to develop automaticity and high skill performance during distractions, particularly during more difficult surgical tasks. It is unclear as to whether training should be done in the presence of distractions or distractions should only be used for post-training testing of levels of automaticity.

The effect of stress on learning in surgical skill acquisition.

BACKGROUND: An excessive level of stress and anxiety in medical education can have a negative impact on learning. In particular, the interaction between attending surgeons and trainees in the operating room could induce stress on trainees that is counterproductive, especially if the teaching style or feedback is unduly harsh or critical. AIM: To characterize the effects of stress resulting from attending-trainee interaction during surgical skill acquisition. METHODS: Forty medical students learned to perform the FLS pattern-cutting task for the first time in one of four scenarios. In the control condition, no mentor was present. In the three experimental conditions, participants were observed, encouraged, or criticized by an expert surgeon. RESULTS: Task performance, as well as physiological and subjective indicators of stress, were measured. Taking both speed and accuracy into account, participants who were criticized performed the worst on the task, and those who were encouraged performed best. Physiological and subjective measures indicated that the criticized participants experienced the highest level of stress and anxiety. CONCLUSION: Even though providing constructive criticism to trainees is inevitable during the course of teaching, an exceedingly critical and negative mentoring style by attending physicians could be detrimental to trainees' acquisition of surgical skills.

Haptic Communication in Collaborative Virtual Environments.

OBJECTIVE: To understand the interaction between haptic and verbal communication, we quantified the relative effect of verbal, haptic, and haptic-plus-verbal feedback in a collaborative virtual pointing task. BACKGROUND: Collaborative virtual environments (CVEs) provide a medium for interaction among remote participants. Better understanding of the role of haptic feedback as a supplement to verbalization can improve the design of CVEs. METHODS: Thirty-six participants were randomly paired into 18 dyads to complete a 2-D pointing task in a CVE. In a mixed experimental design, participants completed the task in three communication conditions: haptic only (H), verbal only (V), and haptic plus verbal (HV). The order of the conditions presented to the participants was counterbalanced. RESULTS: The time to task completion, path length, overshoot, and root mean square error were analyzed. Overall, performance in the V and HV conditions was significantly better than in the H condition. H was the least efficient communication channel but elicited response with the shortest reaction time. When verbalization was not available, the use of the haptic device was more likely to be exaggerated to ensure information transmission. When verbalization was used, participants converged on the use of a Cartesian coordinate system for communicating spatial information. CONCLUSION: Haptic communication can be used to complete a collaborative virtual task but is less efficient than verbal communication. A training period may help to improve the efficiency of haptic communication. APPLICATION: These results can be used to design remote collaboration tasks incorporating haptic components and for improving the design of CVEs that support haptic communication.

Face and construct validation of a next generation virtual reality (Gen2-VR) surgical simulator.

INTRODUCTION: Surgical performance is affected by distractors and interruptions to surgical workflow that exist in the operating room. However, traditional surgical simulators are used to train surgeons in a skills laboratory that does not recreate these conditions. To overcome this limitation, we have developed a novel, immersive virtual reality (Gen2-VR) system to train surgeons in these environments. This study was to establish face and construct validity of our system. METHODS AND PROCEDURES: The study was a within-subjects design, with subjects repeating a virtual peg transfer task under three different conditions: Case I: traditional VR; Case II: Gen2-VR with no distractions and Case III: Gen2-VR with distractions and interruptions. In Case III, to simulate the effects of distractions and interruptions, music was played intermittently, the camera lens was fogged for 10 s and tools malfunctioned for 15 s at random points in time during the simulation. At the completion of the study subjects filled in a 5-point Likert scale feedback questionnaire. A total of sixteen subjects participated in this study. RESULTS: Friedman test showed significant difference in scores between the three conditions (p < 0.0001). Post hoc analysis using Wilcoxon signed-rank tests with Bonferroni correction further showed that all the three conditions were significantly different from each other (Case I, Case II, p < 0.0001), (Case I, Case III, p < 0.0001) and (Case II, Case III, p = 0.009). Subjects rated that fog (mean 4.18) and tool malfunction (median 4.56) significantly hindered their performance. CONCLUSION: The results showed that Gen2-VR simulator has both face and construct validity and that it can accurately and realistically present distractions and interruptions in a simulated OR, in spite of limitations of the current HMD hardware technology.

Achieving Interface and Environment Fidelity in the Virtual Basic Laparoscopic Surgical Trainer.

Virtual reality trainers are educational tools with great potential for laparoscopic surgery. They can provide basic skills training in a controlled environment and free of risks for patients. They can also offer objective performance assessment without the need for proctors. However, designing effective user interfaces that allow the acquisition of the appropriate technical skills on these systems remains a challenge. This paper aims to examine a process for achieving interface and environment fidelity during the development of the Virtual Basic Laparoscopic Surgical Trainer (VBLaST). Two iterations of the design process were conducted and evaluated. For that purpose, a total of 42 subjects participated in two experimental studies in which two versions of the VBLaST were compared to the accepted standard in the surgical community for training and assessing basic laparoscopic skills in North America, the FLS box-trainer. Participants performed 10 trials of the peg transfer task on each trainer. The assessment of task performance was based on the validated FLS scoring method. Moreover, a subjective evaluation questionnaire was used to assess the fidelity aspects of the VBLaST relative to the FLS trainer. Finally, a focus group session with expert surgeons was conducted as a comparative situated evaluation after the first design iteration. This session aimed to assess the fidelity aspects of the early VBLaST prototype as compared to the FLS trainer. The results indicate that user performance on the earlier version of the VBLaST resulting from the first design iteration was significantly lower than the performance on the standard FLS box-trainer. The comparative situated evaluation with domain experts permitted us to identify some issues related to the visual, haptic and interface fidelity on this early prototype. Results of the second experiment indicate that the performance on the second generation VBLaST was significantly improved as compared to the first generation and not significantly different from that of the standard FLS box-trainer. Furthermore, the subjects rated the fidelity features of the modified VBLaST version higher than the early version. These findings demonstrate the value of the comparative situated evaluation sessions entailing hands on reflection by domain experts to achieve the environment and interface fidelity and training objectives when designing a virtual reality laparoscopic trainer. This suggests that this method could be used successfully in the future to enhance the value of VR systems as an alternative to physical trainers for laparoscopic surgery skills. Some recommendations on how to use this method to achieve the environment and interface fidelity of a VR laparoscopic surgical trainer are identified.

Identifying Opportunities for Virtual Reality Simulation in Surgical Education: A Review of the Proceedings from the Innovation, Design, and Emerging Alliances in Surgery (IDEAS) Conference: VR Surgery.

OBJECTIVES: To conduct a review of the state of virtual reality (VR) simulation technology, to identify areas of surgical education that have the greatest potential to benefit from it, and to identify challenges to implementation. BACKGROUND DATA: Simulation is an increasingly important part of surgical training. VR is a developing platform for using simulation to teach technical skills, behavioral skills, and entire procedures to trainees and practicing surgeons worldwide. Questions exist regarding the science behind the technology and most effective usage of VR simulation. A symposium was held to address these issues. METHODS: Engineers, educators, and surgeons held a conference in November 2013 both to review the background science behind simulation technology and to create guidelines for its use in teaching and credentialing trainees and surgeons in practice. RESULTS: Several technologic challenges were identified that must be overcome in order for VR simulation to be useful in surgery. Specific areas of student, resident, and practicing surgeon training and testing that would likely benefit from VR were identified: technical skills, team training and decision-making skills, and patient safety, such as in use of electrosurgical equipment. CONCLUSIONS: VR simulation has the potential to become an essential piece of surgical education curriculum but depends heavily on the establishment of an agreed upon set of goals. Researchers and clinicians must collaborate to allocate funding toward projects that help achieve these goals. The recommendations outlined here should guide further study and implementation of VR simulation.

Toward scar-free surgery: an analysis of the increasing complexity from laparoscopic surgery to NOTES.

BACKGROUND: NOTES is an emerging technique for performing surgical procedures, such as cholecystectomy. Debate about its real benefit over the traditional laparoscopic technique is on-going. There have been several clinical studies comparing NOTES to conventional laparoscopic surgery. However, no work has been done to compare these techniques from a Human Factors perspective. This study presents a systematic analysis describing and comparing different existing NOTES methods to laparoscopic cholecystectomy. METHODS: Videos of endoscopic/laparoscopic views from fifteen live cholecystectomies were analyzed to conduct a detailed task analysis of the NOTES technique. A hierarchical task analysis of laparoscopic cholecystectomy and several hybrid transvaginal NOTES cholecystectomies was performed and validated by expert surgeons. To identify similarities and differences between these techniques, their hierarchical decomposition trees were compared. Finally, a timeline analysis was conducted to compare the steps and substeps. RESULTS: At least three variations of the NOTES technique were used for cholecystectomy. Differences between the observed techniques at the substep level of hierarchy and on the instruments being used were found. The timeline analysis showed an increase in time to perform some surgical steps and substeps in NOTES compared to laparoscopic cholecystectomy. CONCLUSION: As pure NOTES is extremely difficult given the current state of development in instrumentation design, most surgeons utilize different hybrid methods-combination of endoscopic and laparoscopic instruments/optics. Results of our hierarchical task analysis yielded an identification of three different hybrid methods to perform cholecystectomy with significant variability among them. The varying degrees to which laparoscopic instruments are utilized to assist in NOTES methods appear to introduce different technical issues and additional tasks leading to an increase in the surgical time. The NOTES continuum of invasiveness is proposed here as a classification scheme for these methods, which was used to construct a clear roadmap for training and technology development.

Effects of sleep hours and fatigue on performance in laparoscopic surgery simulators.

BACKGROUND: Studies on a virtual reality simulator have demonstrated that sleep-deprived residents make more errors. Work-hour restrictions were implemented, among other reasons, to ensure enough sleep time for residents. The objective of this study was to assess the effects of sleep time, perceived fatigue, and experience on surgical performance. We hypothesized that performance would decrease with less sleep and fatigue, and that experienced surgeons would perform better than less experienced surgeons despite sleep deprivation and fatigue. METHODS: Twenty-two surgical residents and attendings performed a peg transfer task on two simulators: the Fundamentals of Laparoscopic Skills (FLS) trainer and the Virtual Basic Laparoscopic Surgical Trainer (VBLaST©), a virtual version of the FLS. Participants also completed questionnaires to assess their fatigue level and recent sleep hours. Each subject performed ten trials on each simulator in a counterbalanced order. Performance was measured using the FLS normalized scores and analyzed using a multiple regression model. RESULTS: The multiple regression analysis showed that sleep hours and perceived fatigue were not covariates. No correlation was found between experience level and sleep hours or fatigue. Sleep hours and fatigue did not appear to affect performance. Expertise level was the only significant determinant of performance in both FLS and VBLaST©. CONCLUSIONS: Restricting resident work hours was expected to result in less fatigue and better clinical performance. In our study, peg transfer task performance was not affected by sleep hours. Experience level was a significant indicator of performance. Further examination of the complex relationship between sleep hour, fatigue, and clinical performance is needed to support the practice of work-hour restriction for surgical residents.

Prevention of surgical skill decay.

The U.S. military medical community spends a great deal of time and resources training its personnel to provide them with the knowledge and skills necessary to perform life-saving tasks, both on the battlefield and at home. However, personnel may fail to retain specialized knowledge and skills if they are not applied during the typical periods of nonuse within the military deployment cycle, and retention of critical knowledge and skills is crucial to the successful care of warfighters. For example, we researched the skill and knowledge loss associated with specialized surgical skills such as those required to perform laparoscopic surgery (LS) procedures. These skills are subject to decay when military surgeons perform combat casualty care during their deployment instead of LS. This article describes our preliminary research identifying critical LS skills, as well as their acquisition and decay rates. It introduces models that identify critical skills related to laparoscopy, and proposes objective metrics for measuring these critical skills. This research will provide insight into best practices for (1) training skills that are durable and resistant to skill decay, (2) assessing these skills over time, and (3) introducing effective refresher training at appropriate intervals to maintain skill proficiency.

Characterizing the learning curve of the VBLaST-PT(©) (Virtual Basic Laparoscopic Skill Trainer).

BACKGROUND: Mastering laparoscopic surgical skills requires considerable time and effort. The Virtual Basic Laparoscopic Skill Trainer (VBLaST-PT(©)) is being developed as a computerized version of the peg transfer task of the Fundamentals of Laparoscopic Surgery (FLS) system using virtual reality technology. We assessed the learning curve of trainees on the VBLaST-PT(©) using the cumulative summation (CUSUM) method and compared them with those on the FLS to establish convergent validity for the VBLaST-PT(©). METHODS: Eighteen medical students from were assigned randomly to one of three groups: control, VBLaST-training, and FLS-training. The VBLaST and the FLS groups performed a total of 150 trials of the peg-transfer task over a 3-week period, 5 days a week. Their CUSUM scores were computed based on predefined performance criteria (junior, intermediate, and senior levels). RESULTS: Of the six subjects in the VBLaST-training group, five achieved at least the "junior" level, three achieved the "intermediate" level, and one achieved the "senior" level of performance criterion by the end of the 150 trials. In comparison, for the FLS group, three students achieved the "senior" criterion and all six students achieved the "intermediate" and "junior" criteria by the 150th trials. Both the VBLaST-PT(©) and the FLS systems showed significant skill improvement and retention, albeit with system specificity as measured by transfer of learning in the retention test: The VBLaST-trained group performed better on the VBLaST-PT(©) than on FLS (p = 0.003), whereas the FLS-trained group performed better on the FLS than on VBLaST-PT(©) (p = 0.002). CONCLUSIONS: We characterized the learning curve for a virtual peg transfer task on the VBLaST-PT(©) and compared it with the FLS using CUSUM analysis. Subjects in both training groups showed significant improvement in skill performance, but the transfer of training between systems was not significant.

Development and validation of VBLaST-PT© : a virtual peg transfer simulator.

Peg transfer is one of the five tasks in the Fundamentals of Laparoscopic Surgery (FLS), which is now established as a standard for training minimally invasive surgery. In this paper we report development and preliminary validation of Virtual Basic Laparoscopic Skill Trainer-peg transfer (VBLaST-PT© simulator. Face validation of the VBLaST-PT© with 34 subjects revealed high scores for all aspects of simulation. A two-tailed Mann-Whitney performed on the total scores on VBLaST-PT© showed significant (p=0.001) difference between the skill groups.

Effect of automatic image realignment on visuomotor coordination in simulated laparoscopic surgery.

During laparoscopic surgery, the surgeon's hand-eye coordination is often disrupted by the incongruent mapping between the orientation of the endoscopic view and the actual operative field. Two experiments were conducted to examine the effect of automatic image realignment on the performance of laparoscopic surgery. The first experiment investigated how visual-motor misalignment impacted laparoscopic surgery performance. Novice subjects were randomly assigned to one of the two paired viewing conditions in a simulated laparoscopic surgery environment: 1) the endoscope was either at the center of the modeled workspace with an optical axis of 90°, or at -45° from the midline of the subjects with an optical axis 45°; 2) the endoscope was either at 0°, or at 180° from the midline of the subjects, both with an optical axis of 45°. Each group of twelve subjects performed a dynamic point-and-touch task under the assigned pair of viewing conditions, each with eight image orientations, in a repeated-measures mixed design. The second experiment examined whether the automatic realigning mechanism that was activated mid-task (such that a congruent mapping between display and control was re-established if the mapping at the beginning of the task had been misaligned) was helpful to improve performance. Twelve novice subjects performed the same task as in the first experiment in a repeated-measures design. Performance was examined under three misaligned visuomotor mappings, each followed by the realigned mapping activated by the automatic realigning mechanism. Results showed that performance was best when the endoscopic image was perfectly aligned with the actual task space (0° image orientation), but degraded progressively as a function of deviation from perfect alignment. Subjects' performance maintained a consistent pattern across 8 image orientations regardless of optical axis orientation and endoscope location. Performance was improved with the automatic realigning mechanism. It is recommended that any solution to restore the visuomotor congruency in laparoscopic surgery should first align the image with the task space. This work has implications for the design of visualization systems in laparoscopic surgery.

Ergonomic considerations in natural orifice translumenal endoscopic surgery (NOTES): a case study.

Surgical technique evolved from traditional open surgery to laparoscopic surgery, offering patients reduced pain and quick recovery. Recently, a new approach called natural orifice translumenal endoscopic surgery (NOTES) has emerged. In NOTES, procedures may be transvaginal, transgastric, or transrectal or transesophageal. NOTES procedures present new ergonomic challenges to surgeons due to visualization and tissue manipulation challenges. An ergonomic analysis of NOTES cholecystectomy was conducted. As there is currently no standardization for performing NOTES, this analysis presents the results as a case study. Results showed NOTES procedures impose unique limitations on the surgeon's ability to perform surgical tasks autonomously, requiring collaboration and coordination amongst the surgical team members.

Evaluation of techniques to model bend loss in multimode fibers for endoscopic application.

Bend loss from optical fibers can have positive applications, which need to be characterized and related to fiber curvature in a systematic approach to be useful. One potential application for optical fibers is a shape sensor for tracking flexible bodies in remote access environments, such as in endoscopy or boroscopy. We conducted a review of bend-loss characterization and evaluated several methods for characterizing bend loss in multimode optical fibers for an endoscopic shape-tracking application. Specifically, closed-form equation-based methods and numerical simulations were examined. Beam propagation method (BPM) simulations were determined to be the most applicable characterization tool. Results from simulations using BPM software were compared to experimentally obtained data. BPM simulation was sufficiently accurate for modeling 50 mum fibers but impractical for larger, multimode fibers.

Differences in day and night shift clinical performance in anesthesiology.

OBJECTIVE: This study examined whether anesthesia residents (physicians in training) performed clinical duties in the operating room differently during the day versus at night. BACKGROUND: Fatigue from sleep deprivation and working through the night is common for physicians, particularly during residency training. METHODS: Using a repeated-measures design, we studied 13 pairs of day-night matched anesthesia cases. Dependent measures included task times, workload ratings, response to an alarm light latency task, and mood. RESULTS: Residents spent significantly less time on manual tasks and more time on monitoring tasks during the maintenance phase at night than during the day. Residents reported more negative mood at night than during the day, both pre- and postoperation. However, time of day had no effect on the mood change between pre- and postoperation. Workload ratings and the response time to an alarm light latency task were not significantly different between night and day cases. CONCLUSIONS: Because night shift residents had been awake and working for more than 16 hr, the observed differences in task performance and mood may be attributed to fatigue. The changes in task distribution during night shift work may represent compensatory strategies to maintain patient care quality while keeping perceived workload at a manageable level. APPLICATIONS: Fatigue effects during night shifts should be considered when designing work-rest schedules for clinicians. This matched-case control scheme can also be applied to study other phenomena associated with patient safety in the actual clinical environment.