Workload Assessment of Surgeons: Correlation Between Nasa Tlx and Blinks

Bin Zheng, MD PhD, Xianta Jiang, Msc, Geoffery Tien, Msc, Adam Meneghetti, MD, Neely Panton, MD, Stella Atkins, PhD. University of British Columbia


Objective: Blinks are known as an indicator of visual attention and stresses. When an operator is overloaded, he will tend to blink less, and quickly. In this study, surgeons’ mental workloads were assessed by eye blinks and the NASA Task Load Index (NASA TLX), a paper assessment. We hypothesized that surgeons who display physical signs of stresses during a laparoscopic procedure will report a high level of mental workload assessed at the end of the procedure with the NASA TLX.
Methods: While performing a partial cholecystectomy on a virtual reality trainer (SurgicalSim, METI Inc.), a surgeon’s physical signs of stresses were captured continuously using our lightweight head-mounted eye-tracker (Locarna Systems Inc.). Blink frequency and duration were computed automatically using computer video-processing program. At the end of each procedure, the operating surgeon was required to complete the NASA TLX to further assess the workload experienced during the procedure. Surgical performance was measured by task time, trajectory of tool tips, and errors. Surgeons’ blink frequency and duration were correlated to the outcomes of the NASA TLX reports. Workload outcome assessed by the NASA TLX were compared between two groups of surgeons who performed either low frequency (less than 6 blinks/minute) or high frequency of blinks (more than 6 blinks/minute during the procedure).
Results: A total of 42 surgical trials were recorded from 23 surgeons. The correlation coefficients (Pearson test) between NASA TLX and the blink frequency and duration were – 0.17 (P = 0.282) and 0.446 (P = 0.776), respectively. Surgeons who blinked less frequently reported a higher level of frustration (46 vs. 34, P = 0.047) and overall level of workload (57 vs. 47, P = 0.045) compared with those who blinked more frequently. Interestingly, task performance was not associated with the blink frequency performed by surgeons. Although the low-blink surgeons were more satisfied with their performance (60 vs. 43, P = 0.005), task time (P = 0.439), length of tool tip trajectory (P = 0.925), and number of surgical errors made in the procedure (P = 0.671) were not significantly different between the two blink groups.
Our research hypothesis was supported; the mental workload of surgeons assessed through a self-reported instrument matched well to the stresses recorded by physical signs. This study also demonstrated the value of using eye-tracking technology for assessment of surgeon mental workload in the operating room. Surgeons with a high mental workload showed blinking with less frequency. As we can record the eye motion of surgeons with surgical video, we expect to develop a way to annotate difficult steps in the procedure and visualize the surgeon’s mental state during the surgical procedure.

Session Number: SS02 – Instrumentation / Ergonomics
Program Number: S008

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