UBC Theses and Dissertations
Cardio-respiratory responses to mental challenge : high, moderate, and low heart rate reactors Hait, Aaron Vincent
Three issues were examined in this study: (1) the extent to which psychological challenge or stress elicits changes in the breathing patterns of normal subjects; (2) whether breathing pattern changes covary with cardiovascular arousal; and (3) whether individuals identified as being potentially at-risk for developing hypertension respond to mental challenge tasks with breathing pattern and cardiovascular changes that are reliably different from those of lower risk individuals. Subjects were 100 healthy young men divided into reactor quintiles on the basis of their heart rate (HR) changes to a 1-minute cold pressor test. Those in the upper quintile were designated as being at-risk for developing hypertension. Their cardiovascular and respiratory changes to two counterbalanced versions of a 5-minute mental arithmetic test (Easy & Hard) were compared with those of the third and fifth quintile subjects. Marked individual differences were evident in the direction and extent of breathing changes. Overall, the rate, amplitude, variability, and predominant mode of breathing increased substantially over resting levels in response to the math tasks. Only breathing rate and variability reliably covaried with task difficulty. Little correspondence was found between breathing changes and cardiovascular arousal. The data did indicate a trend for breathing to shift towards greater ribcage dominance as task difficulty increased. This was especially true for the at-risk group and least true for the low reactor quintile. The expected group differences in cardiovascular reactivity were not found however, implying that the HR reactivity to cold stimulation is not a good predictor of reactivity to acute mental challenge or stress. Overall, the results suggest that breathing patterns change in response to psychological stress but are not clearly associated with cardiovascular arousal. The attempt to identify subgroups of aberrant breathers on the basis of HR reactivity also yielded equivocal results.
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