Mechanical effects of respiration and stepping on systolic arterial pressure variability during treadmill exercise.
OBJECTIVE
To evaluate the changes produced by maximal dynamic exercise in the rhythmic components of systolic arterial pressure variability.


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.
Centre for Cardiovascular Research (CNR), Second Department of Internal Medicine, L. Sacco Hospital, University of Milan, Italy.
S
S
Piazza
R
R
Furlan
S
S
Dell'Orto
A
A
Porta
F
F
Lombardi
M
M
Pagani
A
A
Malliani
D000328:Adult; D001794:Blood Pressure / Q000502:physiology*; D018660:Blood Pressure Monitoring, Ambulatory; D005080:Exercise Test; D006801:Humans; D012119:Respiration / Q000502:physiology*