For almost 60 yr, direct laryngoscopy was the sole method used by anaesthesiologists to insert a tracheal tube into the trachea. The search for a bigger and better angle of view during difficult intubations led to the development of devices using video assistance. The first generation of videolaryngoscopes was developed based on the technology used in rigid fibreoptic laryngoscopes.¹ The need of long training periods and the high incidence of complications did not make the first generation of videolaryngoscopes popular.² In 2001, a new type of videolaryngoscopes arrived in the shape of the glidescope^® (Verathon Company, USA). The glidescope^® used a high-resolution digital camera placed at the tip of an improved Macintosh laryngoscope blade, attached to a high-definition screen. The device also featured the advantage of an anti-fogging system.³ The glidescope^® is able to help anaesthesiologists to obtain improved Cormack and Lehane views in comparison with standard direct laryngoscopy.⁴ Other types of videolaryngoscopes were then developed; all have been shown to improve the view of the vocal cords.⁵

We have developed an automatic anaesthesia system for closed-loop administration of anaesthesia drugs. The control variables used were bispectral index (BIS) and Analgoscore for hypnosis and antinociception, respectively. One hundred and eighty-six patients were randomly enrolled in two groups. Propofol, remifentanil, and rocuronium were administered using closed-loop feedback control (closed-loop, n = 93) or manually (control group, n = 93). The clinical performance of hypnosis control was determined by calculating the offset from a BIS of 45: ‘excellent’, ‘good’, ‘poor’, and ‘inadequate’ control was defined as BIS values within 10%, from 11% to 20%, from 21% to 30%, or >30% offset from the target. The clinical performance of analgesia was defined as the offset from Analgoscore values. Data presented as mean (standard deviation) (95% confidence interval). Excellent or good control of hypnosis was achieved significantly longer in the closed-loop group [47.0 (9.8%) (45.0/49.0), 34.4 (4.7%) (33.5/35.4)] than in the control group [37.3 (14.3%) (34.4/40.2) and 32.3 (7.6%) (30.7/33.7)], respectively (P<0.0001 and 0.0085). Poor and inadequate control of hypnosis was significantly shorter in the closed-loop group [10.8 (5.0%) (9.8/11.8) and 7.7 (6.2%) (6.4/9.0)] than in the control group [14.7 (6.8%) (13.3/16.0) and 15.8 (14.7%) (12.8/18.8)], respectively (P<0.0001). Excellent control of analgesia was achieved significantly longer in the closed-loop group [78.7 (16.2%) (75.4/82.0)] than in the control group [73.7 (17.8%) (70.1/77.3)] (P=0.0456). The closed-loop system was better at maintaining BIS and Analgoscore than manual administration.