The Effect of High-Frequency, Structured Expert Feedback on the Learning Curves of Basic Interventional Ultrasound Skills Applied to Regional Anesthesia

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Proficiency in needle-to-ultrasound beam alignment and accurate approach to structures are pivotal for ultrasound-guided regional anesthesia. This study evaluated the effects of high-frequency, structured expert feedback on simulation training of such abilities.


Forty-two subjects randomly allocated as controls or intervention participated in two 25-trial experiments. Experiment 1 consisted of inserting a needle into a bovine muscular phantom parallel to the ultrasound beam while maintaining full imaging of the needle. In experiment 2, the needle aimed to contact a target inside the phantom. Intervention subjects received structured feedback between trials. Controls received a global critique after completing the trials. The slopes of the learning curves derived from the sequences of successes and failures were compared. Change-point analyses identified the start and the end of learning in trial sequences. The number of trials associated with learning, the number of technical errors, and the duration of training sessions were compared between intervention and controls.


In experiment 1, learning curves departed from 73% (controls) and 76% (intervention) success rates; slopes (standard error) were 0.79% (0.02%) and 0.71% (0.04), respectively, with mean absolute difference of 0.18% (95% confidence interval [CI], 0.17%–0.19%; P = 0). Intervention subjects’ learning curves were shorter and steeper than those of controls. In experiment 2, the learning curves departed from 43% (controls) and 80% (intervention) success rates; slopes (standard error) were 1.06% (0.02%) and 0.42% (0.03%), respectively, with a mean difference of 0.65% (95% CI, 0.64%–0.66%; P = 0). Feedback was associated with a greater number of trials associated with learning in both experiment 1 (mean difference, 1.55 trials; 95% CI, 0.15–3 trials; P = 0) and experiment 2 (mean difference, 4.25 trials; 95% CI, 1.47–7.03 trials; P = 0) and a lower number of technical errors per trial in experiments 1 (mean difference, 0.19; 95% CI, 0.07–0.30; P = .02) and 2 (mean difference, 0.58; 95% CI, 0.45–0.70; P = 0), but longer training sessions in both experiments 1 (mean difference, 9.2 minutes; 95% CI, 4.15–14.24 minutes; P = .01) and 2 (mean difference, 7.4 minutes; 95% CI, 1.17–13.59 minutes; P = .02).


High-frequency, structured expert feedback compared favorably to self-directed learning, being associated with shorter learning curves, smaller number of technical errors, and longer duration of in-training improvement, but increased duration of the training sessions.

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