Background

The nature of medical emergencies places emergency physicians at risk for high levels of acute psychological stress (APS). Stress-modifying techniques like visualization, breath control, and mental practice may help mitigate APS, but objective markers of stress are difficult to measure in the clinical setting. We explored the relationship between heart rate variability (HRV), a real-time measure of autonomic arousal, and self-reported APS among emergency medicine (EM) residents learning to intubate on actual patients.

Methods

This was a prospective study of postgraduate year 1 (PGY-1) EM residents at a single academic medical center during their 1-month anesthesia rotation. We obtained repeated measures of HRV immediately before and during the first intubation attempt each day. Participants completed the modified Spielberger State-Trait Anxiety Inventory (STAI-6) before intubation attempts and scored intubation difficulty using the Intubation Difficulty Scale. We analyzed HRV using root mean square of successive differences and analyzed data using clustered data methods and Pearson correlation coefficients.

Results

We enrolled eight PGY-1 residents and recorded 64 intubations. Mean HRV in the 2 minutes before intubation (17.88 ± 9.22) and during intubation (21.17 ± 13.46) was significantly lower than resting baseline (32.09 ± 15.23; adjusted mean difference [95% CI] = -13.90 [-20.35 to -7.45], p < 0.001; and -10.77 [-17.65 to -3.88], p = 0.02). Preintubation anxiety was negatively correlated with HRV (r = -0.39 [-0.58 to -0.16], p = 0.001). Intubation difficulty was not significantly correlated with HRV (r = -0.12 [-0.36 to 0.13], p = 0.35).

Conclusions

HRV shows promise as a real-time index of autonomic arousal and may serve as an outcome measure in the evaluation of stress-modifying interventions.