IMPAIRED MODULATION OF ARTERIAL BAROREFLEX CONTROL OF BLOOD PRESSURE. HEART RATE AND PERIPHERAL RESISTANCE DURING LOWER BODY NEGATIVE PRESSURE IN CHRONIC HEART FAILURE

Open-loop baroreflex responses were evaluated in eight conscious dogs before and during congestive heart failure to determine the effects of failure on baroreflex control of blood pressure, heart rate, cardiac output, and total peripheral resistance. Heart failure was induced by rapid ventricular pacing. Baroreflex function was determined by calculation of the range and gain of the open-loop stimulus-response relationships for the effect of carotid sinus pressure on blood pressure, heart rate, cardiac output, and total peripheral resistance. The range and gain of blood pressure responses were substantially reduced as early as 3 days after induction of heart failure (161 +/- 6 to 99 +/- 8 mmHg and -2.7 +/- 0.3 to -1.5 +/- 0.1, respectively) and remained depressed for the 21 days of heart failure. This depression in baroreflex control of blood pressure was associated with similar depressions in reflex range and gain for heart rate (125 +/- 9 to 78 +/- 11 beats/min and -2.05 +/- 0.2 to -1.16 +/- 0.2 beats/min, respectively) and cardiac output (1.74 +/- 0.2 to 0.46 +/- 0.2 l/min and -0.81 +/- 0.02 to -0.027 +/- 0.008 l/min, respectively). The group-averaged range and gain for reflex control of vascular resistance were not altered by heart failure. In three dogs, discontinuation of rapid ventricular pacing led to resolution of heart failure within 7 days and partial restoration of the range and gain of reflex control of blood pressure. We conclude that heart failure reversibly depresses baroreflex control of blood pressure principally through a concurrent reduction in reflex control of cardiac output, whereas reflex control of vascular resistance is not consistently affected.

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

Journal of Neurophysiology ◽

10.1152/jn.2001.86.2.559 ◽

2001 ◽

Vol 86 (2) ◽

pp. 559-564 ◽

Cited By ~ 21

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.

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

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.2001.281.2.r468 ◽

2001 ◽

Vol 281 (2) ◽

pp. R468-R475 ◽

Cited By ~ 31

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.

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Hemodynamic Strategies in Blood Pressure Regulation During Orthostatic Challenge in Women

Canadian Journal of Applied Physiology ◽

10.1139/h97-023 ◽

1997 ◽

Vol 22 (4) ◽

pp. 351-367

Author(s):

Tania L. Culham ◽

Gabrielle K. Savard

Keyword(s):

Blood Pressure ◽

Arterial Pressure ◽

Stroke Volume ◽

Negative Pressure ◽

Lower Body Negative Pressure ◽

Peripheral Resistance ◽

Orthostatic Tolerance ◽

Lower Body ◽

Orthostatic Challenge ◽

Carotid Baroreflex

Several studies indicate that carotid baroreflex responsiveness is a good predictor of orthostatic tolerance. Two groups of healthy women with high (HI) and low (LO) carotid baroreflex responsiveness were studied (a) to determine any differences in the level of orthostatic tolerance of the two groups, and (b) to study the hemodynamic strategies used by HI and LO responders to regulate arterial pressure during the orthostatic challenge of lower body negative pressure (LBNP). Orthostatic tolerance was similar between the two groups, whereas the hemodynamic strategies recruited to maintain blood pressure at −40 mmHg LBNP differed: HI responders exhibited greater LBNP-induced decreases in stroke volume and cardiac output, as well as a greater increase in peripheral resistance compared to LO responders (p < .05). In addition, a significant increase in plasma renin activity during LBNP was found in the HI responders only. No significant between-group differences were found in arterial and cardiopulmonary control of vascular resistance or arterial haroreflex control of heart rate during LBNP. Key words: arterial pressure, carotid baroreceptor, lower body negative pressure, orthostatic tolerance, stroke volume

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Hemodynamic response during lower body negative pressure: role of volume status.

Journal of the American Society of Nephrology ◽

10.1681/asn.v91105 ◽

1998 ◽

Vol 9 (1) ◽

pp. 105-113 ◽

Cited By ~ 1

Author(s):

G Ligtenberg ◽

P J Blankestijn ◽

H A Koomans

Keyword(s):

Heart Rate ◽

Cardiac Index ◽

Blood Volume ◽

Pulse Pressure ◽

Negative Pressure ◽

Lower Body Negative Pressure ◽

Peripheral Resistance ◽

Hemodynamic Response ◽

Volume Status ◽

Lower Body

Sudden dialysis-related hypotension is characterized by paradoxical vasodilation, suggestive of sympathoinhibition. A similar hypotensive reaction can be evoked by lower body negative pressure (LBNP), which thus allows the study of the numerous factors involved in dialysis hypotension separately. This article examines the influence of changes in volume status on the hemodynamic response to LBNP (45 mmHg up to the iliac crest, maximum 60 min) in 12 healthy subjects. LBNP caused a decrease in cardiac index and pulse pressure, and an increase in heart rate and total peripheral resistance, most of which developed within the first 3 min of LBNP. Six subjects developed sudden hypotension characterized by vasodilation after 9 +/- 4 min of LBNP. After saline expansion (25 ml/kg), which increased blood volume by approximately 8%, five subjects endured LBNP for the full 60 min. However, after 60 min of LBNP, the circulatory parameters suggested a similar critical situation as that observed before presyncope in their first experiment. The other six subjects endured the full 60 min of LBNP. After furosemide-induced volume reduction associated with 1.6 +/- 0.2 kg weight loss and approximately 7% blood volume reduction, five of them developed vasodilatory presyncope after 17 +/- 5 min of LBNP. Comparison of presyncopal and nonpresyncopal experiments within subjects, as well as between subjects, showed that the early (3 min) response to LBNP was different: Despite similar decreases in cardiac index, the values for systolic pressure, pulse pressure, peripheral resistance, and stroke volume were lower, and the heart rate was higher in the experiments ending in presyncope. It is concluded that the volume status is a determinant of the tolerance to LBNP, probably by affecting the vasoconstrictive response. By inference, this study suggests that the vasoconstrictive response to the hemodynamic stress of hemodialysis is also influenced by the volume status.

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

Clinical Science ◽

10.1042/cs0830535 ◽

1992 ◽

Vol 83 (5) ◽

pp. 535-540 ◽

Cited By ~ 45

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.

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Simulation of cardiovascular response to lower body negative pressure from 0 to -40 mmHg

Journal of Applied Physiology ◽

10.1152/jappl.1994.77.2.630 ◽

1994 ◽

Vol 77 (2) ◽

pp. 630-640 ◽

Cited By ~ 25

Author(s):

F. M. Melchior ◽

R. S. Srinivasan ◽

P. H. Thullier ◽

J. M. Clere

Keyword(s):

Heart Rate ◽

Negative Pressure ◽

Baroreflex Sensitivity ◽

Lower Body Negative Pressure ◽

Cardiovascular Response ◽

Left Ventricular ◽

Diastolic Filling ◽

Lower Body ◽

Arterial Baroreflex ◽

Arterial Baroreflex Sensitivity

This paper presents a mathematical model for simulation of the human cardiovascular response to lower body negative pressure (LBNP) up to -40 mmHg both under normal conditions and when arterial baroreflex sensitivity or leg blood capacity (LBC) is altered. Development of the model assumes that the LBNP response could be explained solely on the bases of 1) blood volume redistribution, 2) left ventricular end-diastolic filling, 3) interaction between left ventricle and peripheral circulation, and 4) modulations of peripheral resistances and heart rate by arterial and cardiopulmonary baroreflexes. The model reproduced well experimental data obtained both under normal conditions and during complete autonomic blockade; thus it is validated for simulation of the cardiovascular response from 0 to -40 mmHg LBNP. We tested the ability of the model to simulate the changes in LBNP response due to a reduction in LBC. To assess these changes experimentally, six healthy men were subjected to LBNP of -15, -30, and -38 mmHg with and without wearing elastic compression stockings. Stockings significantly reduced LBC (from 3.9 +/- 0.3 to 1.8 +/- 0.4 ml/100 ml tissue at -38 mmHg LBNP; P < 0.01) and attenuated the change in heart rate (from 23 +/- 4 to 8 +/- 3% at -38 mmHg LBNP; P < 0.05). The model accurately reproduced this result. The model is useful for assessing the influence of LBC or other parameters such as arterial baroreflex sensitivity in diminishing the orthostatic tolerance of humans after spaceflight, bed rest, or endurance training.

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Aortic baroreflex control of heart rate during hypertensive stimuli: effect of fitness

Journal of Applied Physiology ◽

10.1152/jappl.1993.74.4.1555 ◽

1993 ◽

Vol 74 (4) ◽

pp. 1555-1562 ◽

Cited By ~ 34

Author(s):

X. Shi ◽

J. M. Andresen ◽

J. T. Potts ◽

B. H. Foresman ◽

S. A. Stern ◽

...

Keyword(s):

Heart Rate ◽

Steady State ◽

Negative Pressure ◽

Lower Body Negative Pressure ◽

Venous Pressure ◽

Lower Body ◽

Baroreflex Control ◽

Fitness Level ◽

Neck Pressure ◽

Sinus Pressure

We examined the aortic baroreflex control of heart rate (HR) in seven healthy young men of average fitness (AF) and seven of high fitness (HF). The fitness level was determined by maximal oxygen uptake (AF = 42.9 +/- 1.1, HF = 62.3 +/- 1.8 ml.kg-1.min-1). Aortic baroreflex control of HR was determined during a steady-state increase of mean arterial pressure (MAP; AF, +15.0 +/- 2.1 and HF, +18.3 +/- 0.8 mmHg) with phenylephrine (PE) infusion combined with positive neck pressure (NP; AF, 18 +/- 2.0 and HF, 20 +/- 0.8 mmHg) to counteract the increased carotid sinus pressure and with low levels of lower body negative pressure to counteract the increased central venous pressure. There was no group difference in the increased MAP or NP, nor was there stage difference in MAP within either group during PE infusion. However, the isolated cardiac-aortic baroreflex gains (i.e., delta HR/delta MAP) were significantly less in the HF (0.16 +/- 0.02 and 0.14 +/- 0.03 beats.min-1.mmHg-1) than in the AF (0.52 +/- 0.08 and 0.59 +/- 0.07 beats.min-1.mmHg-1) subjects at PE + NP and PE + NP + lower body negative pressure. We concluded that during steady-state increases in MAP, the sensitivity of aortic baroreflex control of HR was significantly less in the HF than in the AF subjects.

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Short-term variability of blood pressure: effects of lower-body negative pressure and long-duration bed rest

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00050.2012 ◽

2012 ◽

Vol 303 (1) ◽

pp. R77-R85 ◽

Cited By ~ 10

Author(s):

Federico Aletti ◽

Manuela Ferrario ◽

Da Xu ◽

Danielle K. Greaves ◽

J. Kevin Shoemaker ◽

...

Keyword(s):

Blood Pressure ◽

Negative Pressure ◽

Lower Body Negative Pressure ◽

Venous Pressure ◽

Bed Rest ◽

Pressure Effects ◽

Lower Body ◽

Arterial Baroreflex ◽

Long Duration ◽

Cardiopulmonary Baroreflex

Mild lower-body negative pressure (LBNP) has been utilized to selectively unload cardiopulmonary baroreceptors, but there is evidence that arterial baroreceptors can be transiently unloaded after the onset of mild LBNP. In this paper, a black box mathematical model for the prediction of diastolic blood pressure (DBP) variability from multiple inputs (systolic blood pressure, R-R interval duration, and central venous pressure) was applied to interpret the dynamics of blood pressure maintenance under the challenge of LBNP and in long-duration, head-down bed rest (HDBR). Hemodynamic recordings from seven participants in the WISE (Women's International Space Simulation for Exploration) Study collected during an experiment of incremental LBNP (−10 mmHg, −20 mmHg, −30 mmHg) were analyzed before and on day 50 of a 60-day-long HDBR campaign. Autoregressive spectral analysis focused on low-frequency (LF, ∼0.1 Hz) oscillations of DBP, which are related to fluctuations in vascular resistance due to sympathetic and baroreflex regulation of vasomotor tone. The arterial baroreflex-related component explained 49 ± 13% of LF variability of DBP in spontaneous conditions, and 89 ± 9% ( P < 0.05) on day 50 of HDBR, while the cardiopulmonary baroreflex component explained 17 ± 9% and 12 ± 4%, respectively. The arterial baroreflex-related variability was significantly increased in bed rest also for LBNP equal to −20 and −30 mmHg. The proposed technique provided a model interpretation of the proportional effect of arterial baroreflex vs. cardiopulmonary baroreflex-mediated components of blood pressure control and showed that arterial baroreflex was the main player in the mediation of DBP variability. Data during bed rest suggested that cardiopulmonary baroreflex-related effects are blunted and that blood pressure maintenance in the presence of an orthostatic stimulus relies mostly on arterial control.

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Factors mediating the pressor response to isometric muscle contraction: An experimental study in healthy volunteers during lower body negative pressure

PLoS ONE ◽

10.1371/journal.pone.0243627 ◽

2020 ◽

Vol 15 (12) ◽

pp. e0243627

Author(s):

Niels A. Stens ◽

Jonny Hisdal ◽

Espen F. Bakke ◽

Narinder Kaur ◽

Archana Sharma ◽

...

Keyword(s):

Blood Pressure ◽

Negative Pressure ◽

Lower Body Negative Pressure ◽

Blood Pressure Response ◽

Pressor Response ◽

Isometric Exercise ◽

Peripheral Resistance ◽

Relative Importance ◽

Lower Body ◽

Arterial Blood

Whilst both cardiac output (CO) and total peripheral resistance (TPR) determine mean arterial blood pressure (MAP), their relative importance in the pressor response to isometric exercise remains unclear. This study aimed to elucidate the relative importance of these two different factors by examining pressor responses during cardiopulmonary unloading leading to step-wise reductions in CO. Hemodynamics were investigated in 11 healthy individuals before, during and after two-minute isometric exercise during lower body negative pressure (LBNP; -20mmHg and -40mmHg). The blood pressure response to isometric exercise was similar during normal and reduced preload, despite a step-wise reduction in CO during LBNP (-20mmHg and -40mmHg). During -20mmHg LBNP, the decreased stroke volume, and consequently CO, was counteracted by an increased TPR, while heart rate (HR) was unaffected. HR was increased during -40 mmHg LBNP, although insufficient to maintain CO; the drop in CO was perfectly compensated by an increased TPR to maintain MAP. Likewise, transient application of LBNP (-20mmHg and -40mmHg) resulted in a short transient drop in MAP, caused by a decrease in CO, which was compensated by an increase in TPR. This study suggests that, in case of reductions of CO, changes in TPR are primarily responsible for maintaining the pressor response during isometric exercise. This highlights the relative importance of TPR compared to CO in mediating the pressor response during isometric exercise.

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