Leg crossing with muscle tensing, a physical counter-manoeuvre to prevent syncope, enhances leg blood flow

2007 ◽  
Vol 112 (3) ◽  
pp. 193-201 ◽  
Author(s):  
Jan T. Groothuis ◽  
Nynke van Dijk ◽  
Walter ter Woerds ◽  
Wouter Wieling ◽  
Maria T. E. Hopman
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Orthostatic Intolerance ◽  
Peripheral Resistance ◽  
Haemodynamic Effects ◽  
Vascular Conductance ◽  
Leg Blood Flow ◽  
Head Up Tilt

In patients with orthostatic intolerance, the mechanisms to maintain BP (blood pressure) fail. A physical counter-manoeuvre to postpone or even prevent orthostatic intolerance in these patients is leg crossing combined with muscle tensing. Although the central haemodynamic effects of physical counter-manoeuvres are well documented, not much is known about the peripheral haemodynamic events. Therefore the purpose of the present study was to examine the peripheral haemodynamic effects of leg crossing combined with muscle tensing during 70° head-up tilt. Healthy subjects (n=13) were monitored for 10 min in the supine position followed by 10 min in 70° head-up tilt and, finally, for 2 min of leg crossing with muscle tensing in 70° head-up tilt. MAP (mean arterial BP), heart rate, stroke volume, cardiac output and total peripheral resistance were measured continuously by Portapres. Leg blood flow was measured using Doppler ultrasound. Leg vascular conductance was calculated as leg blood flow/MAP. A significant increase in MAP (13 mmHg), stroke volume (27%) and cardiac output (18%), a significant decrease in heart rate (−5 beats/min) and no change in total peripheral resistance during the physical counter-manoeuvre were observed when compared with baseline 70° head-up tilt. A significant increase in leg blood flow (325 ml/min) and leg vascular conductance (2.9 arbitrary units) were seen during the physical counter-manoeuvre when compared with baseline 70° head-up tilt. In conclusion, the present study indicates that the physical counter-manoeuvre of leg crossing combined with muscle tensing clearly enhances leg blood flow and, at the same time, elevates MAP.

Pet CO2 inversely affects MSNA response to orthostatic stress

2001 ◽  
Vol 281 (3) ◽  
pp. H1040-H1046 ◽  
Author(s):  
J. Kevin Shoemaker ◽  
Debbie D. O'Leary ◽  
Richard L. Hughson
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Cardiac Output ◽  
Orthostatic Intolerance ◽  
Muscle Sympathetic Nerve Activity ◽  
Peripheral Resistance ◽  
Burst Frequency ◽  
Head Up Tilt ◽  
End Tidal ◽  
Combined Data

Arterial hypocapnia has been associated with orthostatic intolerance. Therefore, we tested the hypothesis that hypocapnia may be detrimental to increases in muscle sympathetic nerve activity (MSNA) and total peripheral resistance (TPR) during head-up tilt (HUT). Ventilation was increased ∼1.5 times above baseline for each of three conditions, whereas end-tidal Pco 2 (Pet CO2 ) was clamped at normocapnic (Normo), hypercapnic (Hyper; +5 mmHg relative to Normo), and hypocapnic (Hypo; −5 mmHg relative to Normo) conditions. MSNA (microneurography), heart rate, blood pressure (BP, Finapres), and cardiac output (Q, Doppler) were measured continuously during supine rest and 45° HUT. The increase in heart rate when changing from supine to HUT ( P < 0.001) was not different across Pet CO2 conditions. MSNA burst frequency increased similarly with HUT in all conditions ( P < 0.05). However, total MSNA and the increase in total amplitude relative to baseline (%ΔMSNA) increased more when changing to HUT during Hypo compared with Hyper ( P < 0.05). Both BP and Q were higher during Hyper than both Normo and Hypo (main effect; P < 0.05). Therefore, the MSNA response to HUT varied inversely with levels of Pet CO2 . The combined data suggest that augmented cardiac output with hypercapnia sustained blood pressure during HUT leading to a diminished sympathetic response.

Orthostatic intolerance after spaceflight

1996 ◽  
Vol 81 (1) ◽  
pp. 7-18 ◽  
Author(s):  
J. C. Buckey ◽  
L. D. Lane ◽  
B. D. Levine ◽  
D. E. Watenpaugh ◽  
S. J. Wright ◽  
...  
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Space Shuttle ◽  
Orthostatic Intolerance ◽  
Peripheral Resistance ◽  
Systemic Hemodynamic ◽  
Vasoconstrictor Response ◽  
Before And After ◽  
Underlying Mechanisms

Orthostatic intolerance occurs commonly after spaceflight, and important aspects of the underlying mechanisms remain unclear. We studied 14 individuals supine and standing before and after three space shuttle missions of 9-14 days. After spaceflight, 9 of the 14 (64%) crew members could not complete a 10-min stand test that all completed preflight. Pre- and postflight supine hemodynamics were similar in both groups except for slightly higher systolic and mean arterial pressures preflight in the finishers [15 +/- 3.7 and 8 +/- 1.2 (SE) mmHg, respectively; P < 0.05]. Postflight, finishers and nonfinishers had equally large postural reductions in stroke volume (-47 +/- 3.7 and -48 +/- 3.3 ml, respectively) and increases in heart rate (35 +/- 6.6 and 51 +/- 5.2 beats/min, respectively). Cardiac output during standing was also similar (3.6 +/- 0.4 and 4.1 +/- 0.3 l/min, respectively). However, the finishers had a greater postflight vasoconstrictor response with higher total peripheral resistance during standing (22.3 +/- 1.2 units preflight and 29.4 +/- 2.3 units postflight) than did the nonfinishers (20.1 +/- 1.1 units preflight and 19.9 +/- 1.4 units postflight). We conclude that 1) the primary systemic hemodynamic event, i.e., the postural decrease in stroke volume, was similar in finishers and nonfinishers and 2) the heart rate response and cardiac output during standing were not significantly different, but 3) the postural vasoconstrictor response was significantly greater among the finishers (P < 0.01).

scholarly journals Central and peripheral contributors to skeletal muscle hyperemia: response to passive limb movement

2010 ◽  
Vol 108 (1) ◽  
pp. 76-84 ◽  
Author(s):  
John McDaniel ◽  
Anette S. Fjeldstad ◽  
Steve Ives ◽  
Melissa Hayman ◽  
Phil Kithas ◽  
...  
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Cardiac Output ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Stroke Volume ◽  
Limb Movement ◽  
Leg Blood Flow ◽  
Passive Exercise

The central and peripheral contributions to exercise-induced hyperemia are not well understood. Thus, utilizing a reductionist approach, we determined the sequential peripheral and central responses to passive exercise in nine healthy men (33 ± 9 yr). Cardiac output, heart rate, stroke volume, mean arterial pressure, and femoral blood flow of the passively moved leg and stationary (control) leg were evaluated second by second during 3 min of passive knee extension with and without a thigh cuff that occluded leg blood flow. Without the thigh cuff, significant transient increases in cardiac output (1.0 ± 0.6 l/min, Δ15%), heart rate (7 ± 4 beats/min, Δ12%), stroke volume (7 ± 5 ml, Δ7%), passive leg blood flow (411 ± 146 ml/min, Δ151%), and control leg blood flow (125 ± 68 ml/min, Δ43%) and a transient decrease in mean arterial pressure (3 ± 3 mmHg, 4%) occurred shortly after the onset of limb movement. Although the rise and fall rates of these variables differed, they all returned to baseline values within 45 s; therefore, continued limb movement beyond 45 s does not maintain an increase in cardiac output or net blood flow. Similar changes in the central variables occurred when blood flow to the passively moving leg was occluded. These data confirm the role of peripheral factors and reveal an essential supportive role of cardiac output in the hyperemia at the onset of passive limb movement. This cardiac output response provides an important potential link between the physiology of active and passive exercise.

Cardiovascular changes associated with thermal polypnea in the chicken

1964 ◽  
Vol 207 (6) ◽  
pp. 1349-1353 ◽  
Author(s):  
G. C. Whittow ◽  
P. D. Sturkie ◽  
G. Stein
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Respiratory Rate ◽  
Peripheral Resistance ◽  
Flow Through ◽  
Skin Temperatures ◽  
Increased Blood Flow

The effect of hyperthermia on the respiratory rate, cardiac output, blood pressure, arterial hematocrit, and the skin temperatures of the extremities of unanesthetized hens has been investigated. During hyperthermia, the respiratory rate increased to a maximal value and then declined. There was also an increase in cardiac output, followed by a decrease, but the peak cardiac output occurred at a rectal temperature which was significantly higher than that at which the peak respiratory rate was recorded. The increase in cardiac output was the result of an increase in both stroke volume and heart rate. The diminution of cardiac output seemed to be related to a decrease in the stroke volume at high levels of heart rate. The decrease in blood pressure and total peripheral resistance was attributed partly to an increased blood flow through the extremities.

Leg vasoconstriction during dynamic exercise with reduced cardiac output

1992 ◽  
Vol 73 (5) ◽  
pp. 1838-1846 ◽  
Author(s):  
J. A. Pawelczyk ◽  
B. Hanel ◽  
R. A. Pawelczyk ◽  
J. Warberg ◽  
N. H. Secher
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Cardiac Output ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Dynamic Exercise ◽  
Adrenergic Blockade ◽  
Vascular Conductance ◽  
Leg Blood Flow ◽  
Norepinephrine Spillover

We evaluated whether a reduction in cardiac output during dynamic exercise results in vasoconstriction of active skeletal muscle vasculature. Nine subjects performed four 8-min bouts of cycling exercise at 71 +/- 12 to 145 +/- 13 W (40-84% maximal oxygen uptake). Exercise was repeated after cardioselective (beta 1) adrenergic blockade (0.2 mg/kg metoprolol iv). Leg blood flow and cardiac output were determined with bolus injections of indocyanine green. Femoral arterial and venous pressures were monitored for measurement of heart rate, mean arterial pressure, and calculation of systemic and leg vascular conductance. Leg norepinephrine spillover was used as an index of regional sympathetic activity. During control, the highest heart rate and cardiac output were 171 +/- 3 beats/min and 18.9 +/- 0.9 l/min, respectively. beta 1-Blockade reduced these values to 147 +/- 6 beats/min and 15.3 +/- 0.9 l/min, respectively (P < 0.001). Mean arterial pressure was lower than control during light exercise with beta 1-blockade but did not differ from control with greater exercise intensities. At the highest work rate in the control condition, leg blood flow and vascular conductance were 5.4 +/- 0.3 l/min and 5.2 +/- 0.3 cl.min-1.mmHg-1, respectively, and were reduced during beta 1-blockade to 4.8 +/- 0.4 l/min (P < 0.01) and 4.6 +/- 0.4 cl.min-1.mmHg-1 (P < 0.05). During the same exercise condition leg norepinephrine spillover increased from a control value of 2.64 +/- 1.16 to 5.62 +/- 2.13 nM/min with beta 1-blockade (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Arterial hemodynamics during head-up tilt in conscious dogs

1988 ◽  
Vol 65 (4) ◽  
pp. 1556-1562 ◽  
Author(s):  
T. G. Bedford ◽  
K. J. Dormer
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Cardiac Output ◽  
Peripheral Resistance ◽  
Arterial Hemodynamics ◽  
Arterial Blood ◽  
Upright Standing ◽  
Head Up Tilt ◽  
Tilt Response ◽  
Sustained Increase

The purpose of this study was to measure the major arterial hemodynamic responses to head-up tilt in the conscious dog. After recovery from surgery for instrumentation, and after habituation to tilt, the dogs were tilted from horizontal to 75 degrees for 5 min. The arterial hemodynamic response after the initial cardiovascular adjustments to the tilt consisted of no change in heart rate and significantly increased arterial blood pressure, with significantly reduced stroke volume and cardiac output. Both renal blood flow and terminal aorta blood flow declined significantly, even more than cardiac output. Muscular exertion was not part of the tilt response because upright standing on the hindlimbs elicited a sustained increase in heart rate and a significantly smaller increase in estimated total peripheral resistance. When compared with the orthostatic response in humans, the increase in arterial pressure was exaggerated in the dogs.

Diastolic pressure and peripheral resistance during stellate ganglion stimulation

1963 ◽  
Vol 204 (1) ◽  
pp. 71-72 ◽  
Author(s):  
Edward D. Freis ◽  
Jay N. Cohn ◽  
Thomas E. Liptak ◽  
Aristide G. B. Kovach
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Cardiac Output ◽  
Total Peripheral Resistance ◽  
Diastolic Pressure ◽  
Stellate Ganglion ◽  
Peripheral Resistance ◽  
Resistance Vessels ◽  
Left Stellate Ganglion ◽  
Increased Blood Flow

The mechanism of the diastolic pressure elevation occurring during left stellate ganglion stimulation was investigated. The cardiac output rose considerably, the heart rate remained essentially unchanged, and the total peripheral resistance fell moderately. The diastolic rise appeared to be due to increased blood flow rather than to any active changes in resistance vessels.

scholarly journals Development of a Simple ImageJ-Based Method for Dynamic Blood Flow Tracking in Zebrafish Embryos and Its Application in Drug Toxicity Evaluation

Inventions ◽  
2019 ◽  
Vol 4 (4) ◽  
pp. 65 ◽  
Author(s):  
Fiorency Santoso ◽  
Bonifasius Putera Sampurna ◽  
Yu-Heng Lai ◽  
Sung-Tzu Liang ◽  
Erwei Hao ◽  
...  
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Cardiac Output ◽  
Blood Cell ◽  
Stroke Volume ◽  
Flow Velocity ◽  
Blood Flow Velocity ◽  
Video Recording ◽  
Cardiovascular Function ◽  
Zebrafish Embryos

This study aimed to develop a simple and cost-effective method to measure blood flow in zebrafish by using an image-based approach. Three days post fertilization (dpf) zebrafish embryos were mounted with methylcellulose and subjected to video recording for tracking blood flow under an inverted microscope equipped with a high-speed CCD camera. In addition, Hoffman lens was used to enhance the blood cell contrast. The red blood cell movement was tracked by using the TrackMate plug-in in the ImageJ image processing program. Moreover, Stack Difference and Time Series Analyzer plug-in were used to detect dynamic pixel changes over time to calculate the blood flow rate. In addition to blood flow velocity and heart rate, the effect of drug treatments on other cardiovascular function parameters, such as stroke volume and cardiac output remains to be explored. Therefore, by using this method, the potential side effects on the cardiovascular performance of ethyl 3-aminobenzoate methanesulfonate (MS222) and 3-isobutyl-1-methylxanthine (IBMX) were evaluated. MS222 is a common anesthetic, while IBMX is a naturally occurring methylxanthine. Compared to normal embryos, MS222- and IBMX-treated embryos had a reduced blood flow velocity by approximately 72% and 58%, respectively. This study showed that MS222 significantly decreased the heart rate, whereas IBMX increased the heart rate. Moreover, it also demonstrated that MS222 treatment reduced 50% of the stroke volume and cardiac output. While IBMX decreased the stroke volume only. The results are in line with previous studies that used expensive instruments and complicated software analysis to assess cardiovascular function. In conclusion, a simple and low-cost method can be used to study blood flow in zebrafish embryos for compound screening. Furthermore, it could provide a precise measurement of clinically relevant cardiac functions, specifically heart rate, stroke volume, and cardiac output.

Effect of sympathetic blockade on diurnal variation of hemodynamic patterns

1989 ◽  
Vol 256 (3) ◽  
pp. R778-R785 ◽  
Author(s):  
M. I. Talan ◽  
B. T. Engel
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Total Peripheral Resistance ◽  
Peripheral Resistance ◽  
Base Line ◽  
Sympathetic Blockade ◽  
Selective Blockade ◽  
Arterial Blood

Heart rate, stroke volume, and intra-arterial blood pressure were monitored continuously in each of four monkeys, 18 consecutive h/day for several weeks. The mean heart rate, stroke volume, cardiac output, systolic and diastolic blood pressure, and total peripheral resistance were calculated for each minute and reduced to hourly means. After base-line data were collected for approximately 20 days, observation was continued for equal periods of time under conditions of alpha-sympathetic blockade, beta-sympathetic blockade, and double sympathetic blockade. This was achieved by intra-arterial infusion of prazosin, atenolol, or a combination of both in concentration sufficient for at least 75% reduction of response to injection of agonists. The results confirmed previous findings of a diurnal pattern characterized by a fall in cardiac output and a rise in total peripheral resistance throughout the night. This pattern was not eliminated by selective blockade, of alpha- or beta-sympathetic receptors or by double sympathetic blockade; in fact, it was exacerbated by sympathetic blockade, indicating that the sympathetic nervous system attenuates these events. Because these findings indicate that blood volume redistribution is probably not the mechanism mediating the observed effects, we have hypothesized that a diurnal loss in plasma volume may mediate the fall in cardiac output and that the rise in total peripheral resistance reflects a homeostatic regulation of arterial pressure.

scholarly journals Changes in regional blood volume and blood flow during static handgrip

2007 ◽  
Vol 292 (1) ◽  
pp. H215-H223 ◽  
Author(s):  
Julian M. Stewart ◽  
Leslie D. Montgomery ◽  
June L. Glover ◽  
Marvin S. Medow
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Cardiac Output ◽  
Blood Volume ◽  
Cardiac Contractility ◽  
Peripheral Resistance ◽  
Low Frequencies ◽  
Exercise Pressor Reflex ◽  
Heart Rate Regulation ◽  
Pressor Reflex

Increased blood pressure (BP) and heart rate during exercise characterizes the exercise pressor reflex. When evoked by static handgrip, mechanoreceptors and metaboreceptors produce regional changes in blood volume and blood flow, which are incompletely characterized in humans. We studied 16 healthy subjects aged 20–27 yr using segmental impedance plethysmography validated against dye dilution and venous occlusion plethysmography to noninvasively measure changes in regional blood volumes and blood flows. Static handgrip while in supine position was performed for 2 min without postexercise ischemia. Measurements of heart rate and BP variability and coherence analyses were used to examine baroreflex-mediated autonomic effects. During handgrip exercise, systolic BP increased from 120 ± 10 to 148 ± 14 mmHg, whereas heart rate increased from 60 ± 8 to 82 ± 12 beats/min. Heart rate variability decreased, whereas BP variability increased, and transfer function amplitude was reduced from 18 ± 2 to 8 ± 2 ms/mmHg at low frequencies of ∼0.1 Hz. This was associated with marked reduction of coherence between BP and heart rate (from 0.76 ± 0.10 to 0.26 ± 0.05) indicative of uncoupling of heart rate regulation by the baroreflex. Cardiac output increased by ∼18% with a 4.5% increase in central blood volume and an 8.5% increase in total peripheral resistance, suggesting increased cardiac preload and contractility. Splanchnic blood volume decreased reciprocally with smaller decreases in pelvic and leg volumes, increased splanchnic, pelvic and calf peripheral resistance, and evidence for splanchnic venoconstriction. We conclude that the exercise pressor reflex is associated with reduced baroreflex cardiovagal regulation and driven by increased cardiac output related to enhanced preload, cardiac contractility, and splanchnic blood mobilization.

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