Abstract
A new approach for assessment of baroreflex function in humanss was developed in this study. Arterial pressure and R‐R interval were recorded in 10 healthy young (30 ± 5 yrs) and 8 elderly subjects (66 ± 6 yrs). Periodic squat‐stand maneuvers were performed at the frequencies of 0.05 and 0.1Hz respectively to produce large oscillations in arterial pressure to stimulate the baroreflex. Transfer function between changes in arterial pressure and R‐R interval was estimated to assess the cardiac baroreflex sensitivity (gain) and the temporal relations (phase) between these variables. During squat‐stand maneuvers, spectral power of oscillations in systolic blood pressure at the frequency of 0.05 Hz was 374 ± 191 mmHg2 in young and 561± 321 mmHg2 in the elderly, and at the 0.1Hz was 253 ± 119 mmHg2 in young and 203 ± 87 mmHg2 in the elderly. In response to these changes in arterial pressure, large oscillations in R‐R interval also were created at the frequencies of 0.05 and 0.1Hz respectively. When compared with the young, transfer function gain was reduced, while the phase became more negative in the elderly. In conclusion, periodic squat‐stand maneuvers produced large and coherent oscillations in arterial pressure and R‐R interval. Transfer function analysis between these variables provides a new and widely available method for assessment of dynamic baroreflex function in humans. Application of this method showed that not only was cardiac baroreflex sensitivity was reduced, but also the heart rate response to changes in arterial pressure was delayed in the elderly.
Published Version
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