Cardiorespiratory assessment of mental load in Pilot selection

Kurzfassung

The ability to cope with mentally demanding situations and maintain cognitive functioning is a core requirement for airline pilots. Stress resistance is therefore an important selection criterion which is, however, difficult to assess. The main objective of this project was to enhance the assessment of stress resistance in pilot selection and to investigate the relationship between mental load and respiration as well as cardiac parameters. At the German Aerospace Center, the evaluation of stress resistance is currently based on observer ratings of visible strain symptoms and self-reports as well as performance measures. Since mental load has been shown to have clear effects on physiological systems, we investigated whether cardiorespiratory measures that can be obtained cheap and unobtrusively provide additional valuable information. While cardiac parameters have been studied extensively in response to mental load, little research has been devoted to the usefulness of respiratory measures – even though respiration is closely related to psychological processes under stress. Existing studies revealed that, on the one hand, respiratory reactivity might reflect mental load and, on the other hand, inappropriate changes might even cause performance decrements. However, further empirical evidence is needed to establish both findings. In a review study we integrated empirical findings on respiratory changes from baseline to mentally demanding task periods and possible effects of task difficulty and task duration. Based on the available studies, we found that mentally demanding episodes were characterized by faster breathing and higher minute ventilation, but that the respiratory amplitude was generally invariant to mental load. While total variability in respiratory rate was not systematically affected by mental load, we found that correlated variability was reduced. In addition, our analyses revealed that mental load may lead to overbreathing (decreased end-tidal carbon dioxide levels) and to higher oxygen consumption and carbon dioxide production. Habituation effects were only reported for respiratory rate. Overall, this review showed that several respiratory measures are sensitive to mental load. Since most of the available studies were restricted to traditional time and volume parameters, we conducted an experimental study which also included variability and gas exchanges measures. The present experimental study was conducted on a sample of pilot candidates and aimed at investigating whether cardiorespiratory measures are sensitive to mental load as induced by a highly demanding multiple task that resembles the mental requirements of pilot selection and routine flight in a simplified way. We assessed heart rate, heart rate variability, respiratory rate, respiratory variability, and partial pressure of end-tidal carbon dioxide during baseline, task, and recovery periods. All measures changed clearly from baseline to task. Effects of recovery were observed for all measures besides end-tidal carbon dioxide. When analyzing associations with cognitive performance, small effects were found for respiratory measures, indicating that a more flexible system is related to higher cognitive performance. In addition, we investigated individual differences in personality and their associations with cardiorespiratory activation. While a lower cardiac reactivity was found in participants characterized by cognitive avoidant coping, respiratory rate was reduced in participants with higher levels of self-focused attention. Negative affectivity was not associated with cardiorespiratory activation but moderated the relationship of cardiac and self-reported arousal measures. Given that physiological and self-report measures of mental load are often combined when evaluating operator load, our results imply that an integration of individual differences may reduce unexplained variance. Taken together, the present experimental findings suggest that respiratory parameters would be a useful supplement to the current measures being used to assess stress resistance in pilot selection and that a consideration of trait characteristics may increase the validity of workload assessments.