The relationship between experience and mental workload in anaesthetic practice: an observational study.

Mental workload is seen as a key factor in defining performance and expertise in some complex work environments, but there are no validated instruments for assessing mental workload in anaesthesia. We studied the mental workload of 20 anaesthetists of varying levels of experience, during five routine cases each, by measuring the delay in their responses to a frequently, but randomly, administered vibrotactile stimulus as a secondary task. We delivered, and recorded response times for, 6096 stimuli, with a median (range) of 55.5 (9-178) responses per case. Subjects learnt rapidly to respond to the device and there was no evidence of a 'learning curve' that might bias our results. There was limited evidence of a relationship between workload and experience; for instance, in trainees completing simple cases, mental workload had a negative linear relationship with training grade (rho = -0.360, p = 0.006). However, average differences between trainees and qualified practitioners in response times to the stimulus were overshadowed by differences between subjects at the same level of experience. Finally, although the number of 'hands full' responses was small, removing these from the analysis had a greater effect than expected, suggesting that the 'hands full' condition is not random, but varies with experience and may be independently associated with expertise. This method appears feasible for use in clinical practice and may, with refinement, aid the identification and tracking of the development of expertise in anaesthetic trainees.