Carotid arterial haemodynamics after mild degrees of lower-body negative pressure in man

1992 ◽  
Vol 83 (5) ◽  
pp. 535-540 ◽  
Author(s):  
P. J. Lacolley ◽  
B. M. Pannier ◽  
M. A. Slama ◽  
J. L. Cuche ◽  
A. P. G. Hoeks ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Weight Bearing ◽  
Normal Subjects ◽  
Lower Body ◽  
Head Up Tilt ◽  
Cardiopulmonary Receptors ◽  
Carotid Arterial

1. Pulsatile changes in the diameter of the common carotid artery were studied transcutaneously using an echo-tracking technique in 15 normal subjects: eight subjects before and during application of graded lower-body negative pressure from −5 to −15 mmHg, and seven subjects before and during weight-bearing head-up tilt at 30 and 60 degrees. 2. In concomitant studies of changes in forearm vascular resistance, it was seen that mild lower-body negative pressure produced deactivation of cardiopulmonary receptors without changes in systemic blood pressure or heart rate. 3. After lower-body negative pressure, a significant decrease in carotid arterial diastolic diameter [from 0.662 ± 0.028 to 0.624 ± 0.033 cm (lower-body negative pressure −10 mmHg) and 0.640 ± 0.030 cm lower-body negative pressure −15 mmHg), P<0.001 and <0.05] was observed. 4. After head-up tilt, carotid arterial diameter was also significantly decreased at 30 and 60 degrees, whereas a significant increase in heart rate occurred only at 60 degrees and mean blood pressure did not change. 5. The study provides evidence that the geometry of the arterial wall is substantially modified by noninvasive manoeuvres such as head-up tilting and lower-body negative pressure. The latter is assumed to selectively deactivate human cardiopulmonary receptors, but the present data suggest that local changes may also influence carotid baroreceptors.

Noise-Enhanced Heart Rate and Sympathetic Nerve Responses to Oscillatory Lower Body Negative Pressure in Humans

2001 ◽  
Vol 86 (2) ◽  
pp. 559-564 ◽  
Author(s):  
Ichiro Hidaka ◽  
Shin-Ichi Ando ◽  
Hideaki Shigematsu ◽  
Koji Sakai ◽  
Soko Setoguchi ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Stochastic Resonance ◽  
Negative Pressure ◽  
Sympathetic Nerve ◽  
Carotid Sinus ◽  
Lower Body Negative Pressure ◽  
Arterial System ◽  
Lower Body ◽  
Cardiopulmonary Baroreceptors

By injecting noise into the carotid sinus baroreceptors, we previously showed that heart rate (HR) responses to weak oscillatory tilt were enhanced via a mechanism known as “stochastic resonance.” It remains unclear, however, whether the same responses would be observed when using oscillatory lower body negative pressure (LBNP), which would unload the cardiopulmonary baroreceptors with physically negligible effects on the arterial system. Also, the vasomotor sympathetic activity directly controlling peripheral resistance against hypotensive stimuli was not observed. We therefore investigated the effects of weak (0 to approximately −10 mmHg) oscillatory (0.03 Hz) LBNP on HR and muscle sympathetic nerve activity (MSNA) while adding incremental noise to the carotid sinus baroreceptors via a pneumatic neck chamber. The signal-to-noise ratio of HR, cardiac interbeat interval, and total MSNA were all significantly improved by increasing noise intensity, while there was no significant change in the arterial blood pressure in synchronized with the oscillatory LBNP. We conclude that the stochastic resonance, affecting both HR and MSNA, results from the interaction of noise with the signal in the brain stem, where the neuronal inputs from the arterial and cardiopulmonary baroreceptors first come together in the nucleus tractus solitarius. Also, these results indicate that the noise could induce functional improvement in human blood pressure regulatory system in overcoming given hypotensive stimuli.

Differential sympathetic nerve and heart rate spectral effects of nonhypotensive lower body negative pressure

2001 ◽  
Vol 281 (2) ◽  
pp. R468-R475 ◽  
Author(s):  
John S. Floras ◽  
Gary C. Butler ◽  
Shin-Ichi Ando ◽  
Steven C. Brooks ◽  
Michael J. Pollard ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Stroke Volume ◽  
Negative Pressure ◽  
Sympathetic Nerve ◽  
Lower Body Negative Pressure ◽  
Muscle Sympathetic Nerve Activity ◽  
Venous Pressure ◽  
Harmonic Component ◽  
Lower Body

Lower body negative pressure (LBNP; −5 and −15 mmHg) was applied to 14 men (mean age 44 yr) to test the hypothesis that reductions in preload without effect on stroke volume or blood pressure increase selectively muscle sympathetic nerve activity (MSNA), but not the ratio of low- to high-frequency harmonic component of spectral power (PL/PH), a coarse-graining power spectral estimate of sympathetic heart rate (HR) modulation. LBNP at −5 mmHg lowered central venous pressure and had no effect on stroke volume (Doppler) or systolic blood pressure but reduced vagal HR modulation. This latter finding, a manifestation of arterial baroreceptor unloading, refutes the concept that low levels of LBNP interrogate, selectively, cardiopulmonary reflexes. MSNA increased, whereas PL/PH and HR were unchanged. This discordance is consistent with selectivity of efferent sympathetic responses to nonhypotensive LBNP and with unloading of tonically active sympathoexcitatory atrial reflexes in some subjects. Hypotensive LBNP (−15 mmHg) increased MSNA and PL/PH, but there was no correlation between these changes within subjects. Therefore, HR variability has limited utility as an estimate of the magnitude of orthostatic changes in sympathetic discharge to muscle.

scholarly journals Non-linear Heart Rate and Blood Pressure Interaction in Response to Lower-Body Negative Pressure

2017 ◽  
Vol 8 ◽  
Author(s):  
Ajay K. Verma ◽  
Da Xu ◽  
Amanmeet Garg ◽  
Anita T. Cote ◽  
Nandu Goswami ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Lower Body ◽  
Non Linear

Fractal nature of short-term systolic BP and HR variability during lower body negative pressure

1994 ◽  
Vol 267 (1) ◽  
pp. R26-R33 ◽  
Author(s):  
G. C. Butler ◽  
Y. Yamamoto ◽  
R. L. Hughson
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Heart Rate Variability ◽  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Cardiovascular Responses ◽  
Orthostatic Stress ◽  
Lower Body ◽  
Short Term ◽  
Test Protocol

We have shown previously that the heart rate variability (HRV) signal is fractal in nature with a high degree of complexity, as given by the calculated fractal dimension (DF). We have also reported that loss of complexity, as indicated by a reduction in DF of HRV, is associated with orthostatic hypotension and impending syncope. To extend this investigation of cardiovascular responses, we have investigated the signal characteristics of short-term systolic blood pressure variability (BPV) coincident with measurements of HRV during orthostatic stress. Eight healthy men completed a test protocol of 20 min supine rest followed sequentially by 10 min at each of -5, -15, -25, -40, and -50 mmHg lower body negative pressure (LBNP) and 10 min supine recovery. We found that resting BPV and HRV were fractal with approximately 70% of both variables in the fractal component of the variability signal. The slope of the 1/f beta relationship was 1.16 +/- 0.12 for HRV and 2.31 +/- 0.17 for BPV. With increasing levels of orthostatic stress, the 1/f beta slope of HRV increased significantly to 1.68 +/- 0.08 at -50 mmHg LBNP, whereas the 1/f beta slope was unchanged for BPV. Indicators of parasympathetic and sympathetic nervous system activity derived from heart rate variability suggested reduced and increased values, respectively, as the LBNP increased. These data indicate important differences in heart rate and blood pressure control under orthostatic stress.

Increase in the Strength of Synchronization between the Baroreflex Waves of Blood Pressure and Heart Rate Due to the Lower Body Negative Pressure Effect

2021 ◽  
Vol 47 (4) ◽  
pp. 398-403
Author(s):  
V. O. Negulyaev ◽  
E. A. Orlova ◽  
A. P. Sharova ◽  
O. S. Tarasova ◽  
O. L. Vinogradova ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Negative Pressure ◽  
Pressure Effect ◽  
Lower Body Negative Pressure ◽  
Lower Body

Increase in vagal activity during hypotensive lower-body negative pressure in humans

1988 ◽  
Vol 255 (1) ◽  
pp. R149-R156 ◽  
Author(s):  
K. Sander-Jensen ◽  
J. Mehlsen ◽  
C. Stadeager ◽  
N. J. Christensen ◽  
J. Fahrenkrug ◽  
...  
Keyword(s):  
Heart Rate ◽  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Venous Pressure ◽  
Initial Increase ◽  
Vagal Activity ◽  
Lower Body ◽  
Central Venous ◽  
Subsequent Decrease ◽  
Before And After

Progressive central hypovolemia is characterized by a normotensive, tachycardic stage followed by a reversible, hypotensive stage with slowing of the heart rate (HR). We investigated circulatory changes and arterial hormone concentrations in response to lower-body negative pressure (LBNP) in six volunteers before and after atropine administration. LBNP of 55 mmHg initially resulted in an increase in HR from 55 +/- 4 to 90 +/- 5 beats/min and decreases in mean arterial pressure (MAP) from 94 +/- 4 to 81 +/- 5 mmHg, in central venous pressure from 7 +/- 1 to -3 +/- 1 mmHg, and in cardiac output from 6.1 +/- 0.5 to 3.7 +/- 0.11/min. Concomitantly, epinephrine and norepinephrine levels increased. After 8.2 +/- 2.3 min of LBNP, the MAP had decreased to 41 +/- 7 mmHg and HR had decreased to 57 +/- 3 beats/min. Vasopressin increased from 1.2 +/- 0.3 to 137 +/- 45 pg/ml and renin activity increased from 1.45 +/- 4.0 to 3.80 +/- 1.0 ng.ml-1.h-1 with no further changes in epinephrine, norepinephrine, and vasoactive intestinal polypeptide. A tardy rise in pancreatic polypeptide indicated increased vagal activity. After atropine. LBNP also caused an initial increase in HR, which, however, remained elevated during the subsequent decrease in MAP to 45 +/- 6 mmHg occurring after 8.1 +/- 2.4 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiovascular responses to lower body negative pressure in trained and untrained older men

1992 ◽  
Vol 73 (6) ◽  
pp. 2693-2700 ◽  
Author(s):  
S. Fortney ◽  
C. Tankersley ◽  
J. T. Lightfoot ◽  
D. Drinkwater ◽  
J. Clulow ◽  
...  
Keyword(s):  
Heart Rate ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Older Men ◽  
Volume Index ◽  
Lower Body ◽  
Vo2 Max ◽  
Cardiac Volumes

To determine whether aerobic conditioning alters the orthostatic responses of older subjects, cardiovascular performance was monitored during graded lower body negative pressure in nine highly trained male senior athletes (A) aged 59–73 yr [maximum O2 uptake (VO2 max) = 52.4 +/- 1.7 ml.kg-1 x min-1] and nine age-matched control subjects (C) (VO2 max = 31.0 +/- 2.9 ml.kg-1 x min-1). Cardiac volumes were determined from gated blood pool scintigrams by use of 99mTc-labeled erythrocytes. During lower body negative pressure (0 to -50 mmHg), left ventricular end-diastolic and end-systolic volume indexes and stroke volume index decreased in both groups while heart rate increased. The decreases in cardiac volumes and mean arterial pressure and the increase in heart rate between 0 and -50 mmHg were significantly less in A than in C. For example, end-diastolic volume index decreased by 32 +/- 4 ml in C vs. 14 +/- 2 ml in A (P < 0.01), mean arterial pressure declined 7 +/- 5 mmHg in C and increased by 5 +/- 3 mmHg in A (P < 0.05), and heart rate increased 13 +/- 3 beats/min in C and 7 +/- 1 beats/min in A (P < 0.05). These data suggest that increased VO2 max among older men is associated with improved orthostatic responses.

scholarly journals Differential Effects of Low- and High-Intensity Lower Body Negative Pressure on Noradrenaline and Adrenaline Kinetics in Humans

1996 ◽  
Vol 90 (5) ◽  
pp. 337-343 ◽  
Author(s):  
Marie-Cecile Jacobs ◽  
David S. Goldstein ◽  
Jacques J. Willemsen ◽  
Paul Smits ◽  
Theo Thien ◽  
...  
Keyword(s):  
Heart Rate ◽  
Vascular Resistance ◽  
Pulse Pressure ◽  
Negative Pressure ◽  
High Intensity ◽  
Lower Body Negative Pressure ◽  
Lower Body ◽  
Total Body ◽  
Noradrenaline And Adrenaline ◽  
Forearm Vascular Resistance

1. Lower body negative pressure provides a means to examine neurocirculatory reflexive responses to decreases in venous return to the heart. We assessed whether the pattern of catecholaminergic responses to lower body negative pressure depends on the intensity of the stimulus (−15 versus −40 mmHg). 2. In 14 healthy subjects, responses of forearm blood flow and noradrenaline spillover and of total body noradrenaline and adrenaline spillover were assessed during infusion of [3H]noradrenaline and [3H]adrenaline during −15 and −40 mmHg of lower body negxative pressure. 3. During lower body negative pressure at −15 mmHg, heart rate and pulse pressure did not change, but forearm vascular resistance increased by 25–50%. Forearm noradrenaline spillover increased by about 50%, from 0.63 ± 0.16 to 0.94 ± 0.23 pmol min−1 100 ml−1 (P<0.05). Total body noradrenaline spillover did not change, and total body adrenaline spillover increased significantly by about 30%. Clearances of noradrenaline and adrenaline were unchanged. 4. During lower body negative pressure at −40 mmHg, heart rate increased and pulse pressure decreased. Forearm vascular resistance increased by about 100%, and forearm noradrenaline spillover increased by 80%, from 0.73 ± 0.19 to 1.32 ± 0.36 pmol min−1 100 ml−1 (P<0.05). Total body noradrenaline spillover increased by 30%, and total body adrenaline spillover increased by about 50%. Clearances of both noradrenaline and adrenaline decreased. 5. The results are consistent with the view that selective deactivation of cardiopulmonary baroreceptors during low-intensity lower body negative pressure increases sympathoneural traffic to forearm skeletal muscle and increases adrenomedullary secretion without a concomitant generalized increase in sympathoneural outflows. Concurrent deactivation of cardiopulmonary and arterial baroreceptors during high-intensity lower body negative pressure evokes a more generalized increase in sympathoneural activity, accompanied by further increased adrenomedullary secretion and decreased plasma clearances of noradrenaline and adrenaline. The findings support differential increases in skeletal sympathoneural and adrenomedullary outflows during orthostasis, with more generalized sympathoneural responses to systemic hypotension.

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