Background and objectives: Having identified key determinants of teaching and learning spinal anesthesia, it was necessary to characterize and render the haptic sensations (feeling of touch) associated with needle insertion in the lower back. The approach used is to match recreated sensations (eg, "pop" through skin or dura mater) with experts' perceptions of the equivalent clinical events.
Methods: The study was performed using a haptic device (Phantom Desktop) that simulated the tactile elements of predefined clinical events. Twenty-four experts (anesthetists) were invited to assess rendered versions of 3 basic sensations, which typically occur during the performance of spinal anesthesia with a 25-gauge pencil point needle: (1) touching different surfaces (skin, bone), (2) the "pop" sensations (skin, dura mater), and (3) the sensations associated with advancement of the spinal needle through particular tissues (subcutaneous tissue, ligaments, intrathecal space). The perceptions of each participant were recorded. The relationships between each rendered sensation and the corresponding participant's perception was modeled using standard random effects techniques.
Results: Experts seem to possess a specific haptic perception regarding most sensations. The coefficient of variation was less than 0.50 for all sensations with the exception of intrathecal space. However, there is considerable within-rater variation when experts are presented with the same haptic rendering on more than one occasion for bone surface, skin pop, dura pop, and subcutaneous tissue.
Conclusions: The importance of this finding is that it demonstrates the feasibility of an "expert perception"-based approach to the design of medical simulators.