Continuous HRV analysis of HEMS emergency physicians to specify the work load over the different working days

Up to date, there has been little research about the acute stress load of emergency physicians of the Helicopter Emergency Medical Service (HEMS). Therefore, this study investigates the physiological stress level between an air-rescue day, a clinic day, and a day off (control day). Furthermore, phases of activity and resting were compared to assess the activity of the autonomic nervous system (ANS).

In this field study (within-subjects design), heart rate variability (HRV) and self-perceived stress levels were monitored on an air-rescue day, a clinic day, and a control day of 20 HEMS EPs [three females, 17 males; age: mean (M) = 44.95, standard deviation (SD) = 4.80].

When comparing the activity phases, significant differences were found for HR and HRV. The highest HR was found on the air-rescue day during the phase of landing at the operation site with M = 107.30 bpm (SD = 22.66 bpm), which was significantly higher than during activity phases of the clinic day (M = 88.28 bpm, SD = 11.81 bpm) and the control day (M = 83.28 bpm, SD = 14.83 bpm). The SDNN is significantly higher on the air-rescue day for the phase before the alarm (M = 72.23 ms, SD = 38.60 ms), the phase of the alarm (M = 77.52 ms, SD = 40.52 ms), and the average of all phases (M = 60.04 ms, SD = 34.07 ms) than on the clinic day (M = 38.42 ms, SD = 15.16 ms) and the control day, where the lowest value was reached (M = 39.11 ms, SD = 17.65 ms). The highest LF/HF was found during activity phases of the clinic day with M = 1281.84% (SD = 587.33%), which was significantly higher than the first five phases of the emergency operations and the average of all phases of the emergency operations of the air-rescue day, where a maximum of M = 896.57 ms (SD = 681.79 ms) during the phase before the alarm and a minimum of M = 764.69 ms (SD = 372.28 ms) during the phase of landing at the operation site. The lowest LF/HF for all testing days was found during the activity phases of the control day with M = 693.74% (SD = 404.73%). Overall, 60 observations were analyzed. In the psychological assessment, on average, the EPs shows lower values than the norm sample.

In the comparison of the activity phases, significant effects were found on the clinic day and during the phases of the emergency operations of the air-rescue day for the HR and HRV. Hereby, a significant activation of the EPs ANS and an outweigh of the sympathetic nervous system could be shown, whereby the subjective stress load was reported mainly as low. For the resting phases, no significant differences were found between all testing days. We interpret this as a good sign for the ability of regeneration between the phases of high stress load.