Simulation-based teaching for procedural skills is useful in facilitating the application of knowledge and practice of psychomotor skills in a safe environment.[1]  By allowing the acquisition of expertise through deliberate practice, procedural simulation also improves patient safety.[2]  

Bench top models are useful in helping novice learners acquire adequate psychomotor skills to perform a procedure correctly and safely. However, there is a need for simulation to provide more experienced trainees with appropriate challenges and enhance their expertise. By identifying a trainee’s level of expertise one is able to aim at the zone of proximal development and enhance their acquisition of new skills. Cognitive load theory [3] can be used as a framework to understand to what degree a particular simulation exercise challenges an individual trainee.

Hybrid simulation (HS) combines the use of benchtop models and simulated patients, and is useful in training for complex procedural skills.  In particular, it can help enhance the communication skills –with both patients and other health professionals- required for successful procedures. In order to understand individual trainees experiences to a HS exercise, we investigated the utility of measuring workload using the NASA-TLX instrument. 

We developed a hybrid simulation platform for ultrasound-guided (US) central venous catheter (CVC) insertion. The exercise required insertion of a CVC into a rubber part task trainer affixed to a standardized patient (SP), while interacting with the SP and a standardized nurse, and responding to the patient’s clinical status and ECG-monitoring. 

Two scenarios with increasing levels of difficulty were developed by three clinicians: In scenario 1, halfway through the CVC insertion (when the guide wire was threaded into the vein) the ECG monitor alarm would indicate frequent premature ventricular beats (PVCs). Trainees were expected to interact with the ‘standardized nurse’ and withdraw the guidewire slightly, thus eliminating the PVCs.  In scenario 2, halfway through the CVC insertion the monitor would indicate a decrease in blood pressure to 70/50 mmHg.  The trainee was then required to intervene with intravenous fluids or vasopressors to improve the blood pressure while completing the CVC insertion. Scenario 2 was felt to be of higher difficulty, as inserting the CVC is an important step in treating the patients low blood pressure, thus making successful placement of the catheter a more pressing need. 

After informed consent, ten senior internal medicine trainees (postgraduate year 4) were randomized to go through both scenarios in either sequence (Sc 1 followed by Sc2 or Sc2 followed by Sc1).  After completing each scenario, trainees were given feedback and then asked to complete a NASA-TLX instrument (Fig 1).[4]  

We found that NASA-TLX measures of total workload correlated with scenario difficulty as designed.  Significant variability was seen between residents.  The components of NASA-TLX showing greatest variability This suggests  NASA-TLX provides a useful quantitative anchor of scenario difficulty not captured by checklist performance.  Workload measures such as the NASA-TLX may allow improved learning through modulation of scenario difficulty and cognitive load.  Our future work will aim at appropriately increasing scenario difficulty based on initial workload measures.