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Mechanical effects of respiration and stepping on systolic arterial pressure variability during treadmill exercise
S Piazza1, R Furlan, S Dell'Orto
1Centre for Cardiovascular Research (CNR), Second Department of Internal Medicine, L. Sacco Hospital, University of Milan, Italy.
Aim:
To evaluate the changes produced by maximal dynamic exercise in the rhythmic components of systolic arterial pressure variability.
Patients And Methods:
We studied seven normotensive subjects during different levels of a modified treadmill test (Bruce protocol, up to stage 4). Arterial pressure was measured directly by a high-fidelity microtip pressure transducer. Spectral analysis provided two main oscillatory components of systolic arterial pressure variability, a low-frequency component related to the sympathetic-mediated neural control of vasomotion and a high-frequency component reflecting the mechanical effects of respiration on blood pressure.
Results:
The low-frequency component increased at the beginning of exercise and remained stable thereafter, while the high-frequency component increased progressively. A third rhythmic component (very high frequency) with a frequency higher than respiration and synchronous with the rate of the subjects' footsteps, which was undetectable on a visual inspection of analog tracings, became progressively more apparent, reaching its maximum at exercise stage 4.
Conclusions:
These findings emphasize the importance of high-fidelity techniques and computer analysis for the evaluation of arterial pressure variability in dynamic conditions.