Heart rate variability, cardiac mechanics, and subjectively evaluated stress during simulator flight

The effects of a simulator flight task on the heart rate variation (HRV) and hemodynamic variables were studied in nine pilots with instrument flight ratings. An electrocardiogram (ECG), phonocardiogram (PCG), and impedance cardiogram (ICG) were recorded continuously during three successive flights. Indices of HRV, power spectra, and autocorrelograms were computed from the R-R interval signal. Stroke volume (SV), cardiac output (CO), and systolic time intervals (STI) were determined by means of the ECG, PCG, and ICG. A scaling method for a subjective evaluation of tiredness, effort, and success during the flight was used. The repeats of the flight task decreased the heart rate (HR), CO, and cardiac index (CI). The different phases of the flight altered the HR (mean 97 min-1, S.E.M. 4 min-1), total HRV (RMSM) (mean 33 ms, S.E.M. 5 ms), and the periodic HRV. Subjectively, the pilots felt only moderate stress. The subjectively evaluated tiredness was significantly associated with the STI. Moderate informative stress in the flight simulator affected the chronotropic parameters of the heart. The inotropic state of the heart was not affected by the different phases of the flight but possibly by the diminishing sympathetic drive with accommodation during the repeats.