Abstract
Different cardiovascular response patterns to various laboratory stressors have been noted for some time. These patterns have typically been discriminated in terms of blood pressure (BP) and heart rate (HR) increases. Tasks that elicit greater increases in systolic blood pressure (SBP) and HR have been associated with active coping or $\beta$-adrenergic responses; whereas, tasks that evoke larger increases in diastolic blood pressure (DBP) and decreases in HR have been more likely to be associated with as passive coping or a-adrenergic responses. Classification, however, becomes a problem when SBP, DBP, and HR all increase to the behavioral challenge; therefore, this study examined these responses and other responses of cardiovascular performance (Cardiac Output (CO), Total Peripheral Resistance (TPR) and Systolic Time Intervals (STI)) as determined by impedance cardiography (ICG) to a speech stressor, a mirror star tracing task, and the foot cold pressor test in 10 male and 10 female normotensive, white subjects.The major findings of this study were that the tasks elicited significant increases in both SBP and DBP, but these increases were differentiated by other cardiovascular responses (CO, TPR, and STI) to the various tasks. During the preparation period of the speech task the elevation of BP appears to have resulted from an increase in CO which was apparently supported by increases in cardiac contractility at least as indexed by QT/QX$\sb{\rm on}$ and Heather Index (HI) ratios and a decrease in the PEP/LVET ratio. The augmentation of BP during the speech itself seems to have resulted from an increase in TPR and the maintenance of the CO level from the preparation period. The rise in BP during both the mirror star tracing and cold pressor tasks resulted from increase in TPR. The observations made concerning these response patterns were further supported by the correlations between the plasma catecholamines and the indices of cardiovascular performance.Therefore, based on the present results, when behavioral challenge elicits increases in SBP and DBP the addition of ICG derived measures can aid in the differentiation of responses to the tasks. The speech preparation period showed a response pattern suggestive of $\beta$-adrenergic stimulation, the speech itself a mixed $\beta$- and a-adrenergic pattern of stimulation and the mirror star tracing and cold pressor tasks patterns suggesting a-adrenergic stimulation.