PHYSIOLOGICAL INDEXES OF WORKLOAD IN A SIMULATED FLIGHT TASK

The sensitivity of physiological measures to evaluate workload was inv estigated in a simulated flight task. Heart rate, blood pressure (from beat to beat), respiration and eye blinks were recorded in 14 subject s while they performed a complex task in a flight simulator. Workload was manipulated by introducing an additional task and by varying the t ask difficulty of segments of the flight scenarios. Heart rate and blo od pressure were both affected by the different levels of task difficu lty. Heart-rate variability was found to be confounded by respiration. Slow respiratory activity contributed considerably to heart rate vari ability, especially after periods of high workload (for example, after landing). The gain between blood-pressure and heart-rate variability (modulus) was sensitive to mental effort and was not influences by res piration. Eye blinks, in particular the duration, were specifically af fected by the visual demands of the task and not by the workload in ge neral. When subjects had to process visual information, the number and duration of blinks decreased.