Utility of a low-cost wireless force platform as a potential clinical test of balance recovery after neuraxial anaesthesia.

INTRODUCTION: Recovery of balance after neuraxial anaesthesia can remain delayed after simple clinical tests have demonstrated motor recovery. Dynamic posturography tracks the small movements or sway of a person standing as still as possible on a force platform and has been investigated as an objective measure of the ability to walk following anaesthesia. These are expensive laboratory devices, limiting their clinical utility. One measured variable is path length, the cumulative distance travelled in the horizontal plane by the centre of pressure of a person standing on the platform over 1min. Path length might potentially be measured using the Nintendo® Wii-Fit Balance Board™. METHODS: The feasibility of intercepting raw wireless data from a Wii-Fit Balance Board™ using custom software to calculate path length was explored. Subsequently, path lengths were measured using both this and a laboratory platform simultaneously. In a random order 20 volunteers (a) stood for 1min, feet together, eyes open (conventional baseline test); and (b) stood for 1min, feet together, eyes closed (simulating residual anaesthesia with increased sway). For each device, the ratio b:a was calculated as an index of performance reduction when eyes were closed. RESULTS: Path lengths ranged from 58.5 to 243cm, mean bias 9cm (Wii-Fitlaboratory platform) and 95% confidence limits of 0.04 to -0.13. CONCLUSIONS: The path lengths were in close agreement and the Wii-Fit Balance Board™ may be worthy of further investigation as a tool to objectively assess readiness to ambulate following neuraxial anaesthesia.

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.