Development and evaluation of the second version of scrub nurse robot (SNR) for endoscopic and laparoscopic surgery

Abstract

The shortage of nurses in large hospitals of developed countries has become a major problem. Especially, the shortage of scrub nurses, who assist operating surgeons exchange surgical instruments, has been chronically severe. To compensate for this shortage, we have been proposing the scrub nurse robot (SNR) system that is capable of functioning as a skilled human scrub nurse in endoscopic and laparoscopic surgery. We developed the 2nd version of SNR, and achieved smooth and wide movement of its arms each with 4 DOF. The 2nd SNR is able to speak several sentences and recognize some words as well as the names of surgical instruments, and is also capable of recognizing a surgeon's intraoperative actions by its real-time visual recognition system (RTVRS). The RTVRS is basically composed of both a commercially-available 3D position tracking system and the algorithm that we developed to recognize surgeons' actions during exchange of instruments from the above-mentioned positional data. In this paper, we evaluated how quickly and timely the RTVRS-driven SNR helped surgeon's stand-ins exchange instruments in a laboratory, in comparison with human scrub nurses in real surgical operations. We found two problems about the current RTVRS-driven SNR: one is its response time and the other is chiefly related to the design and mechanism of the part storing the surgical instruments. 1) Concerning the first problem, the RTVRS-driven SNR took 2.11 sec until it finished holding out its hand with an instrument after it had detected a surgeon's stand-in's motions observed during extraction of a surgical instrument. However, a skilled real surgeon took 1.90 sec until he got the requested instrument in the clinical cases although he had to wait for as long as 1.24 sec until receiving it. Therefore, we must speed up the SNR's performance at least by 0.2 sec to assist the real surgeon as human scrub nurses did. Especially, since 0.68 sec out of the 2.11 sec was spent in data processing within the current RTVRS, we conclude that the performance of the RTVRS must be improved rather than speed-up of its arm movement. 2) The other problem was highlighted by measurement of the time during which the stand-ins and the real surgeon had to take their eyes from the monitor displaying the operative field within the abdomen. We termed this period of time 'eyes-off time. The existence of 'eyes-off' time observed during his actions of returning an instrument after use and of waiting for the next instrument was regarded as unfavorable. The 'eyes-off' time was 2.34 sec in the laboratory whereas it was 0.19 sec in the clinical cases. The much longer 'eyes-off' time in the laboratory was partly due to inexperienced stand-ins' performances, but mainly because of the design and mechanism of the part storing the instruments (a tool changer). To overcome these two problems, we are now developing the next version of SNR.