(702) Heart Rate Variability Differentiates Expertise Level in Point-of-Care Lung US Interpretation

Introduction: Currently, defining expertise in point of care ultrasound (POCUS) is based on coursework and supervised case completion, but there is no objective means of determining the level of competence in interpretation, leading to potential negative patient outcomes through misdiagnosis. We sought to determine whether an individual’s cardiovascular response during interpretation in the form of heart rate variability (HRV) metrics could show differences between experts and novices in point of care lung ultrasound interpretation as HRV has previously been shown to serve as an analog of cognitive-executive performance.

Methods: We conducted a prospective, observational, pilot study in which we compared expert pediatric critical care and emergency medicine ultrasound faculty with advanced training in POCUS against novice resident physicians with no advanced training. Participants were asked to interpret a set of 10 lung ultrasound clips, each played for 10 seconds, while we collected HRV metrics that capture the balance between sympathetic and parasympathetic systems including the root mean square of successive differences (RMSSD), the standard deviation of NN intervals (SDNN), the number of NN intervals above 50 milliseconds (ms) (NN50), the proportion of NN intervals above 50 ms/total (pNN50), and low frequency/high frequency (LF/HF) ratio to evaluate for differences between groups. Comparisons were additionally made in diagnostic accuracy and perceived cognitive load using the NASA Task Load Index (NASA-TLX).

Results: 15 participants completed the study (6 experts, 9 novices). Experts had significantly higher rates of correct interpretation as well as lower perceived cognitive workload (all p< 0.05) while at the same time showing HRV metrics consistent with higher rates of sympathetic output than novices in time domain metrics (decreased RMSSD, SDNN, NN50, and pNN50, all p< 0.01), as well as increases in the frequency domain metric of LH/HF ratio (p=0.03).

Conclusions: In our cohort, HRV could be used to objectively discriminate between levels of expertise, as experts physiologically express markers of stress, but maintain high levels of diagnostic accuracy. Future work should focus on its ability to discriminate intermediate levels of expertise to focus on skill acquisition during ultrasound training.