Performance and ergonomic characteristics of expert surgeons using a face-mounted display during virtual reality-simulated laparoscopic surgery: an electromyographically based study.

BACKGROUND: Display positions for laparoscopy in current operating rooms may not be optimal for surgeon comfort or task performance, and face-mounted displays (FMDs) have been forwarded as a potential ergonomic solution. Little is known concerning expert use characteristics of these devices that might help define their role in future surgical care. The authors report the performance and ergonomic characterization of an FMD using virtual reality simulation technology to recreate the surgical environment. METHODS: An FMD was studied in short- and long-duration trials of validated virtual reality-simulated surgical tasks. For the short-duration phase 7, expert surgeons were familiarized with a task on a conventional monitor, then returned on two separate occasions to repeat the task with the FMD while digital photos were taken during task performance and at the end in a standardized fashion. For the long-duration phase 5, expert surgeons performed two separate trials with repetitive groups of validated tasks for a minimum of 30 min while electromyelogram and performance data were measured. Photos of their gaze angle during and at the end of the trial were taken. RESULTS: All the participants consistently assumed a gaze angle slightly below horizontal during task performance. Performance scores on the FMD did not differ from those obtained with a conventional display, and remained stable with repetitive task performance. No participant had electromyelogram signals that exceeded the established thresholds for fatigue, but some had values within the threshold range. CONCLUSION: The natural gaze angle during simulated surgery was consistently a bit below horizontal during rigorous virtual reality-simulated tasks. Performance was not compromised during expert surgeons' use of an FMD, nor did muscle fatigue characteristics arise under these conditions. The findings suggest that these devices may represent a viable alternative to conventional displays for minimally invasive surgery, but definition of specific roles requires further investigation.

Sclerosing mesenteritis. Response to cyclophosphamide.

We present two patients with an aggressive form of sclerosing mesenteritis characterized by a progressive, life-threatening course, prominent retroperitoneal disease, and tubuloreticular structures in one case, an ultrastructural feature associated with autoimmune and cyclophosphamide-responsive diseases. In both patients, aggressive immunosuppressive medical therapy with cyclophosphamide resulted in prompt, dramatic improvement, without recurrence. When the diagnosis of sclerosing mesenteritis is established, we recommend early aggressive medical therapy with cyclophosphamide, particularly when tubuloreticular structures are present.

Electroviscous flow and electrophoretic motion during erythrocyte entry in a glass capillary in the presence of applied electric potential gradients.

One means of measuring an effect of erythrocyte deformability on red cell flow is to determine how long it takes erythrocytes to enter or flow through an aperture whose diameter is smaller than 8 micrometers. It is convenient to impose an electric potential difference across the aperture so that the passage of an erythrocyte can be monitored by electronic means. We report here that such electric potential gradients may have a large influence on red cell entry times, primarily through the mechanism of erythrocyte electrophoretic mobility.