Background. Situation awareness (SA) is considered to be an important non-technical skill for delivering safe anaesthesia. The spatial distribution of visual attention (VA) is an underlying process for attaining adequate SA. In the present study, a novel technology was used to assess the distribution of VA in anaesthetists delivering anaesthesia. The impact of a critical incident on VA in relation to individual experience is analysed in a descriptive and exploratory manner.Methods. Fifteen anaesthetists induced general anaesthesia in a full-scale simulator while wearing a head-mounted eye-tracking camera system. After an uneventful session, workload was increased in a randomized order by simulation of a critical incident in the second or third session. Eye tracking was used for the assessment of individual's distribution of VA to monitors, patient, and environment. A post hoc video analysis revealed information about the spatial distribution of VA. Descriptive statistics and exploratory analysis were used.Results. Twenty per cent of VA was directed to the patient monitor (30% during critical incident scenarios, P=0.003). The more experienced anaesthetists (more than 2 yr of work experience) increased the amount of time dedicated to manual tasks from 21% to 25% during critical incidents, whereas the less experienced decreased from 20% to 14% (P=0.061).Conclusions. Distribution of attention is different during anaesthesia induction with critical incidents compared with uneventful anaesthesia induction. Less experienced anaesthesia providers spend more time on monitoring tasks. Further investigation in confirmatory designs is needed.

BackgroundWorkload assessment is an important tool for improving patient safety in anaesthesia. We tested the hypothesis that heart rate, pupil size, and duration of fixation increase, whereas saccade amplitude decreases with increased workload during simulated critical incidents.MethodsFifteen trainee anaesthetists participated in this randomized cross-over trial. Each participant used a head-mounted eye-tracking device (EyeSeeCam) during induction of general anaesthesia in a full-scale simulation during three different sessions. No critical incident was simulated in the first session. In a randomized order, workload was increased by simulation of a critical incident in the second or third session. Pupil size, duration of fixations, saccadic amplitude, and heart rate of each participant and the simulator conditions were recorded continuously and synchronized. The data were analysed by paired sample t-tests and mixed-effects regression analysis.ResultsThe findings of the second and third sessions of 11 participants were analysed. Pupil diameter and heart rate increased simultaneously as the severity of the simulated critical incident increased. Allowing for individual effects, the simulator conditions explained 92.6% of the variance in pupil diameter and 93.6% of the variance in heart rate (both P<0.001). The duration of fixation decreased with increased workload. The saccadic amplitude remained unaffected by workload changes.ConclusionsPupil size and heart rate reflect workload increase within simulator sessions, but they do not permit overall workload comparisons between individuals or sessions. Contrary to our assumption, the duration of fixation decreased with increased workload. Saccade amplitude did not reflect workload fluctuations.

Remote eye tracking systems are widely used evaluation tools in many disciplines. Such systems have to deal with free head motions that cause a defocussing of the camera image. Hence, remote eye tracking systems usually have a limited operating range. This contribution presents a novel auto-focus setup for a small and mobile remote gaze tracking system that enables a clear eye image acquisition in a large operating range. Therefore, our setup uses a miniature liquid lens to achieve smallest possible focusing latencies and installation space. Using this technology, we extended the eye tracking system's operating range to distances from 0.6 m up to 1.3 m, with a mean accuracy of 0.45° in 4 exemplary working distances.