Determination of the latency effects on surgical performance and the acceptable latency levels in telesurgery using the dV-Trainer® simulator

Abstract

The primary limitation of telesurgery is the communication latency. Accurate and detailed data are lacking to reveal the latency effects on surgical performance; furthermore, the maximum acceptable latency in telesurgery remains unclear. Sixteen medical students performed an energy dissection exercise and a needle-driving exercise on the robotic simulator dV-Trainer(®), and latencies varying between 0 and 1,000ms with a 100-ms interval were randomly and blindly presented. Task completion time, instrument motion, and errors were automatically recorded. The difficulty, security, precision, and fluidity of manipulation were self-scored by subjects between 0 and 4 (0 the best, 2 moderate, and 4 the worst). Task completion time, motion, and errors increased gradually as latency increased. An exponential regression was fit to the mean times and motions (R (2)>0.98). Subjective scorings of the four items were similar. The mean scores were less than 1 at delays ≤200ms, then increased from 1 to 2 at 300-700ms, and finally approached 3 at delays above. In both exercises, latencies ≤300ms were judged to be safe by all and 400-500ms were accepted by 66-75% of subjects. Less than 20% of subjects accepted delays ≥800ms. The surgical performance deteriorates in an exponential way as the latency increases. The delay impact on instrument manipulation is mild at 0-200ms, then increases from small to large at 300-700ms, and finally becomes very large at 800-1,000ms. Latencies ≤200ms are ideal for telesurgery; 300ms is also suitable; 400-500ms may be acceptable but are already tiring; and 600-700ms are difficult to deal with and only acceptable for low risk and simple procedures. Surgery is quite difficult at 800-1,000ms, telementoring would be a better choice in this case.