Carotid baroreflex function during prolonged exercise

1999 ◽  
Vol 87 (1) ◽  
pp. 339-347 ◽  
Author(s):  
K. H. Norton ◽  
K. M. Gallagher ◽  
S. A. Smith ◽  
R. G. Querry ◽  
R. M. Welch-O’Connor ◽  
...  
Keyword(s):  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Perceived Exertion ◽  
Prolonged Exercise ◽  
Venous Pressure ◽  
Exercise Bout ◽  
Operating Point ◽  
Central Command ◽  
Carotid Baroreflex ◽  
Neck Pressure

The present investigation was designed to uncouple the hemodynamic physiological effects of thermoregulation from the effects of a progressively increasing central command activation during prolonged exercise. Subjects performed two 1-h bouts of leg cycling exercise with 1) no intervention and 2) continuous infusion of a dextran solution to maintain central venous pressure constant at the 10-min pressure. Volume infusion resulted in a significant reduction in the decrement in mean arterial pressure seen in the control exercise bout (6.7 ± 1.8 vs. 11.6± 1.3 mmHg, respectively). However, indexes of central command such as heart rate and ratings of perceived exertion rose to a similar extent during both exercise conditions. In addition, the carotid-cardiac baroreflex stimulus-response relationship, as measured by using the neck pressure-neck suction technique, was reset from rest to 10 min of exercise and was further reset from 10 to 50 min of exercise in both exercise conditions, with the operating point being shifted toward the reflex threshold. We conclude that the progressive resetting of the carotid baroreflex and the shift of the reflex operating point render the carotid-cardiac reflex ineffectual in counteracting the continued decrement in mean arterial pressure that occurs during the prolonged exercise.

scholarly journals Carotid baroreflex control of heart rate is enhanced, while control of mean arterial pressure is preserved during whole body heat stress in young healthy men

2016 ◽  
Vol 311 (4) ◽  
pp. R735-R741 ◽  
Author(s):  
Davor Krnjajic ◽  
Dustin R. Allen ◽  
Cory L. Butts ◽  
David M. Keller
Keyword(s):  
Heart Rate ◽  
Heat Stress ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Whole Body ◽  
Chamber Pressure ◽  
Carotid Baroreflex ◽  
Whole Body Heat Stress ◽  
Neck Pressure ◽  
Body Heat

Whole body heat stress (WBH) results in numerous cardiovascular alterations that ultimately reduce orthostatic tolerance. While impaired carotid baroreflex (CBR) function during WBH has been reported as a potential reason for this decrement, study design considerations may limit interpretation of previous findings. We sought to test the hypothesis that CBR function is unaltered during WBH. CBR function was assessed in 10 healthy male subjects (age: 26 ± 3; height: 185 ± 7 cm; weight: 82 ± 10 kg; BMI: 24 ± 3 kg/m2; means ± SD) using 5-s trials of neck pressure (+45, +30, and +15 Torr) and neck suction (−20, −40, −60, and −80 Torr) during normothermia (NT) and passive WBH (Δ core temp ∼1°C). Analyses of stimulus response curves (four-parameter logistic model) for CBR control of heart rate (CBR-HR) and mean arterial pressure (CBR-MAP), as well as separate two-way ANOVA of the hypotensive and hypertensive stimuli (factor 1: thermal condition, factor 2: chamber pressure), were performed. For CBR-HR, maximal gain was increased during WBH (−0.73 ± 0.11) compared with NT (−0.39 ± 0.04, mean ± SE, P = 0.03). In addition, the CBR-HR responding range was increased during WBH (33 ± 5) compared with NT (19 ± 2 bpm, P = 0.03). Separate analysis of hypertensive stimulation revealed enhanced HR responses during WBH at −40, −60, and −80 Torr (condition × chamber pressure interaction, P = 0.049) compared with NT. For CBR-MAP, both logistic analysis and separate two-way ANOVA revealed no differences during WBH. Therefore, in response to passive WBH, CBR control of heart rate (enhanced) and arterial pressure (no change) is well preserved.

Neural blockade during exercise augments central command's contribution to carotid baroreflex resetting

2001 ◽  
Vol 280 (4) ◽  
pp. H1635-H1644 ◽  
Author(s):  
R. G. Querry ◽  
S. A. Smith ◽  
M. Strømstad ◽  
K. Ide ◽  
P. B. Raven ◽  
...  
Keyword(s):  
Perceived Exertion ◽  
Voluntary Contraction ◽  
Control Force ◽  
Central Command ◽  
Response Curves ◽  
Neural Blockade ◽  
Stimulus Response ◽  
Carotid Baroreflex ◽  
Before And After ◽  
Neck Pressure

This investigation was designed to determine central command's role on carotid baroreflex (CBR) resetting during exercise. Nine volunteer subjects performed static and rhythmic handgrip exercise at 30 and 40% maximal voluntary contraction (MVC), respectively, before and after partial axillary neural blockade. Stimulus-response curves were developed using the neck pressure-neck suction technique and a rapid pulse train protocol (+40 to −80 Torr). Regional anesthesia resulted in a significant reduction in MVC. Heart rate (HR) and ratings of perceived exertion (RPE) were used as indexes of central command and were elevated during exercise at control force intensity after induced muscle weakness. The CBR function curves were reset vertically with a minimal lateral shift during control exercise and exhibited a further parallel resetting during exercise with neural blockade. The operating point was progressively reset to coincide with the centering point of the CBR curve. These data suggest that central command was a primary mechanism in the resetting of the CBR during exercise. However, it appeared that central command modulated the carotid-cardiac reflex proportionately more than the carotid-vasomotor reflex.

scholarly journals Baroreflex responses during dry resting and exercise apnoeas in air and pure oxygen

2020 ◽  
Author(s):  
Anna Taboni ◽  
Giovanni Vinetti ◽  
Timothée Fontolliet ◽  
Gabriele Simone Grasso ◽  
Enrico Tam ◽  
...  
Keyword(s):  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Baroreflex Sensitivity ◽  
Pure Oxygen ◽  
Operating Point ◽  
Second Phase ◽  
Central Command ◽  
Sequence Method ◽  
Rest And Exercise

Abstract Purpose We analysed the characteristics of arterial baroreflexes during the first phase of apnoea (φ1). Methods 12 divers performed rest and exercise (30 W) apnoeas (air and oxygen). We measured beat-by-beat R-to-R interval (RRi) and mean arterial pressure (MAP). Mean RRi and MAP values defined the operating point (OP) before (PRE-ss) and in the second phase (φ2) of apnoea. Baroreflex sensitivity (BRS, ms·mmHg−1) was calculated with the sequence method. Results In PRE-ss, BRS was (median [IQR]): at rest, 20.3 [10.0–28.6] in air and 18.8 [13.8–25.2] in O2; at exercise 9.2[8.4–13.2] in air and 10.1[8.4–13.6] in O2. In φ1, during MAP decrease, BRS was lower than in PRE-ss at rest (6.6 [5.3–11.4] in air and 7.7 [4.9–14.3] in O2, p < 0.05). At exercise, BRS in φ1 was 6.4 [3.9–13.1] in air and 6.7 [4.1–9.5] in O2. After attainment of minimum MAP (MAPmin), baroreflex resetting started. After attainment of minimum RRi, baroreflex sequences reappeared. In φ2, BRS at rest was 12.1 [9.6–16.2] in air, 12.9 [9.2–15.8] in O2. At exercise (no φ2 in air), it was 7.9 [5.4–10.7] in O2. In φ2, OP acts at higher MAP values. Conclusion In apnoea φ1, there is a sudden correction of MAP fall via baroreflex. The lower BRS in the earliest φ1 suggests a possible parasympathetic mechanism underpinning this reduction. After MAPmin, baroreflex resets, displacing its OP at higher MAP level; thus, resetting may not be due to central command. After resetting, restoration of BRS suggests re-establishment of vagal drive.

Effects of anesthesia on carotid sinus reflex control of arterial hemodynamics in the dog

1980 ◽  
Vol 239 (5) ◽  
pp. H681-H691 ◽  
Author(s):  
R. H. Cox ◽  
R. J. Bagshaw
Keyword(s):  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Carotid Sinus ◽  
Peripheral Resistance ◽  
Operating Point ◽  
Set Point ◽  
Arterial Hemodynamics ◽  
Pulsatile Pressure ◽  
Reflex Gain ◽  
Reflex Control

The detailed characteristics of the carotid sinus reflex control of regional pressure-flow relations were compared in dogs anesthetized with chloralose, pentobarbital, or halothane. The carotid sinuses were isolated and perfused under conditions of controlled pulsatile pressure. Pressure and flow were measured in the ascending aorta and the celiac, mesenteric, renal, and iliac artery. Mean arterial pressure and peripheral resistance were highest under chloralose and lowest under halothane. For cardiac output this relation was reversed. Set point values of reflex gain and overall range of control were similar under chloralose and halothane and lowest under pentobarbital. These results were found both before and after bilateral cervical vagotomy. Operating point values of regional resistance were generally largest with chloralose and smallest with halothane. Operating point sensitivities of regional resistances were generally smallest under pentobarbital and similar under chloralose and halothane. Vagotomy was associated with increases in set point values of mean arterial pressure, set point gain, and overall range of control under all three anesthetics. With chloralose as a reference, halothane does not depress cardiovascular reflex mechanisms. Carotid sinus reflexes under halothane were as sensitive and well maintained as they were under chloralose. These reflexes were significantly depressed under pentobarbital compared with chloralose.

scholarly journals Identifying the role of group III/IV muscle afferents in the carotid baroreflex control of mean arterial pressure and heart rate during exercise

2018 ◽  
Vol 596 (8) ◽  
pp. 1373-1384 ◽  
Author(s):  
Thomas J. Hureau ◽  
Joshua C. Weavil ◽  
Taylor S. Thurston ◽  
Ryan M. Broxterman ◽  
Ashley D. Nelson ◽  
...  
Keyword(s):  
Heart Rate ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Muscle Afferents ◽  
Baroreflex Control ◽  
Group Iii ◽  
Carotid Baroreflex

Cardiovascular reflexes during abdominal ischemia in cats

1994 ◽  
Vol 267 (1) ◽  
pp. R97-R106 ◽  
Author(s):  
H. S. Huang ◽  
J. C. Longhurst
Keyword(s):  
Blood Pressure ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Femoral Vein ◽  
Venous Pressure ◽  
Vena Cava ◽  
Left Ventricular ◽  
Mesenteric Arteries ◽  
Cardiovascular Reflexes ◽  
Group 3

The cardiovascular effects of regional abdominal ischemia and reperfusion were studied in cats anesthetized with alpha-chloralose. In group 1 (n = 9), central venous pressure was kept constant by a servo-controller while the celiac and superior mesenteric arteries were occluded by loop snares for 10 min. In group 2 (n = 9), a constant-perfusion circuit to the celiac and superior mesenteric arteries that could divert flow to the femoral vein was used to induce abdominal ischemia. In group 3 (n = 7), venous return from the inferior vena cava was controlled, and a constant-perfusion circuit was used to induce abdominal ischemia. Abdominal ischemia significantly (P < 0.05) increased portal venous blood lactate from 4.3 +/- 0.6 to 6.0 +/- 0.6 mM in group 3. The early increases in blood pressure caused by passive volume shifts in groups 1 and 2 were abolished in group 3. The late, i.e., 10 min, response to abdominal ischemia consisted of significant (P < 0.05) increases in mean arterial pressure (29 +/- 7, 24 +/- 7, and 33 +/- 8 mmHg in groups 1, 2, and 3, respectively). Abdominal ischemia also significantly (P < 0.05) increased the first derivative of left ventricular pressure at 40 mmHg developed pressure from 4,355 +/- 377 to 4,839 +/- 407 mmHg/s in group 3. Celiac and superior mesenteric ganglionectomy abolished the late but not the early hemodynamic changes. Ganglionectomy also significantly (P < 0.05) enhanced the decrease in mean arterial pressure during reperfusion in all groups. We conclude that the pressor and contractile responses during 10 min of abdominal ischemia and the relative maintenance of blood pressure during reperfusion after ischemia are reflex in nature.

Motor-Unit Activity Differs With Load Type During a Fatiguing Contraction

2005 ◽  
Vol 93 (3) ◽  
pp. 1381-1392 ◽  
Author(s):  
Carol J. Mottram ◽  
Jennifer M. Jakobi ◽  
John G. Semmler ◽  
Roger M. Enoka
Keyword(s):  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Motor Unit ◽  
Perceived Exertion ◽  
Biceps Brachii ◽  
Discharge Rate ◽  
Motor Output ◽  
Rating Of Perceived Exertion ◽  
Position Task ◽  
Target Force

Despite a similar rate of change in average electromyographic (EMG) activity, previous studies have observed different rates of change in mean arterial pressure, heart rate, perceived exertion, and fluctuations in motor output during the performance of fatiguing contractions that involved different types of loads. To obtain a more direct measure of the motor output from the spinal cord, the purpose of this study was to compare the discharge characteristics of the same motor unit in biceps brachii during the performance of two types of fatiguing contractions. In separate tests with the upper arm vertical and the elbow flexed to 1.57 rad, the seated subjects maintained either a constant upward force at the wrist (force task) or a constant elbow angle (position task) for a prescribed duration. The force and position tasks were performed in random order at a target force equal to 3.5 ± 2.1% (mean ± SD) of the maximal voluntary contraction (MVC) force above the recruitment threshold of the isolated motor unit. Each subject maintained the two tasks for an identical duration (161 ± 96 s) at a mean target force of 22.2 ± 13.4% MVC (range: 3–49% MVC). The dependent variables included the discharge characteristics of the same motor unit in biceps brachii, fluctuations in motor output (force or acceleration), mean arterial pressure, heart rate, and rating of perceived exertion. Despite similar increases in the amplitude of the averaged EMG (% MVC) for the elbow flexor muscles during both tasks ( P = 0.60), the rates of increase in mean arterial pressure ( P < 0.001), rating of perceived exertion ( P = 0.023), and fluctuations in motor output ( P = 0.003) were greater during the position task compared with the force task. Consistent with these differences, mean discharge rate declined at a greater rate during the position task ( P = 0.03), and the coefficient of variation for discharge rate increased only during the position task ( P = 0.02). Furthermore, more motor units were recruited during the position task compared with the force task ( P = 0.01). These findings indicate that despite a comparable net muscle torque, the rate of increase in the motor output from the spinal cord was greater during the position task.

scholarly journals Effects of Different Doses of Magnesium Sulfate on Pneumoperitoneum-related Hemodynamic Changes in Patients Undergoing Gastrointestinal Laparoscopy: a randomized, double-blind, controlled trial

2019 ◽  
Author(s):  
Wei Tan ◽  
Dong-chen Qian ◽  
Meng-meng Zheng ◽  
Xuan Lu ◽  
Yuan Han ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Central Venous Pressure ◽  
Magnesium Sulfate ◽  
Systemic Vascular Resistance ◽  
Vascular Resistance ◽  
Venous Pressure ◽  
Control Group ◽  
Central Venous

Abstract Background: The infusion of magnesium sulfate is well known to reduce arterial pressure and attenuate hemodynamic response to pneumoperitoneum. This study aimed to investigate whether different doses of magnesium sulfate can effectively attenuate the pneumoperitoneum-related hemodynamic changes and the release of vasopressin in patients undergoing laparoscopic gastrointestinal surgery. Methods: Sixty-nine patients undergoing laparoscopic partial gastrectomy were randomized into three groups: group L received magnesium sulfate 30 mg/kg loading dose and 15 mg/kg/h continuous maintenance infusion for 1 h; group H received magnesium sulfate 50 mg/kg followed by 30 mg/kg/h for 1 h; and group S (control group) received same volume 0.9% saline infusion, immediately before the induction of pneumoperitoneum. Systemic vascular resistance (SVR), cardiac output (CO), mean arterial pressure (MAP), heart rate (HR), central venous pressure(CVP), serum vasopressin and magnesium concentrations were measured. The extubation time, visual analogue scale were also assessed. The primary outcome is the difference in SVR between different groups. The secondary outcome is the differences of other indicators between groups, such as CO, MAP, HR, CVP, vasopressin and postoperative pain score. Results: Pneumoperitoneum instantly resulted in a significant reduction of cardiac output and an increase in mean arterial pressure, systemic vascular resistance, central venous pressure and heart rate in the control group (P < 0.01). The mean arterial pressure (T2 – T4), systemic vascular resistance (T2 – T3), central venous pressure(T3-T5) and the level of serum vasopressin were significantly lower (P < 0.05) and the cardiac output (T2 – T3) was significantly higher (P < 0.05) in group H than those in the control group. The mean arterial pressure (T4), systemic vascular resistance (T2), and central venous pressure(T3-T4) were significantly lower in group H than those in group L (P < 0.05). Furthermore, the visual analog scales at 5 min and 20 min, the level of vasopressin, and the dose of remifentanil were significantly decreased in group H compared to the control group and group L (P < 0.01). Conclusion: Magnesium sulfate could safely and effectively attenuate the pneumoperitoneum-related hemodynamic instability during gastrointestinal laparoscopy and improve postoperative pain at serum magnesium concentrations above 2 mmol/L.

scholarly journals Effect of Levosimendan Compared to Conventional Inotropic Agents on Hemodynamics and Outcome in Patient with Poor LV Function Undergoing Cardiac Surgery

2019 ◽  
Vol 7 (19) ◽  
pp. 3205-3210
Author(s):  
Mahmoud Khaled ◽  
Ahmad Naem Almogy ◽  
Mohamed Shehata ◽  
Fahim Ragab ◽  
Khaled Zeineldein
Keyword(s):  
Heart Rate ◽  
Cardiac Surgery ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Venous Pressure ◽  
Left Ventricular ◽  
Base Deficit ◽  
Inotropic Agents ◽  
Poor Left Ventricular Function ◽  
Mixed Venous

BACKGROUND: Patients undergoing heart surgery involving cardiopulmonary bypass (CPB) experience global myocardial ischemia with subsequent reperfusion which, despite cardioplegic protection, may result in different degrees of transient ventricular dysfunction. Levosimendan is a “calcium sensitisers”, it improves myocardial contractility by sensitising troponin C to calcium without increasing myocardial oxygen consumption and without impairing relaxation and diastolic function. AIM: To evaluate the adding effect of a calcium sensitiser (levosimendan) compared to the conventional inotropic and vasoactive agent used in the patient with poor left ventricular function undergoing cardiac surgery on different measured hemodynamic variables and the effect on the outcome. METHODS: It is prospective observational studies were patients were divided into 2 groups of 30 patients each. The first Group received conventional inotropic and vasoactive treatment at different doses, while the other group received levosimendan additionally at a loading dose of 6-12mic/kg according to mean arterial pressure over 0.5 hr followed by 24 hrs infusion at 0.05 to 0.2 mic/kg/min. Hemodynamic data were collected at the end and 30 minutes after CPB, after that at 6, 12, 24, and 36 hours post CPB. Mean arterial pressure (MAP), central venous pressure (CVP), heart rate (HR), mixed venous saturation (Svo2), and base deficit (BD) were measured. RESULTS: Levosimendan had significantly improved postoperative hemodynamic values as in the mixed venous pressure at different times postoperative (p < 0.05), also the base deficit at different times postoperative (p < 0.05), while there was a significant reduction in systemic vascular resistance as decreased mean arterial pressure in levosimendan group compared to conventional group at 6hrs postoperative mean 77.50 ± 10.81 vs 83.73 ± 10.81 with (p = 0.029), and at 12 hrs postoperative mean 77.37 ± 10.10vs 84.23 ± 13.81 with (p = 0.032), and there was no significant difference in heart rate at different times postoperative between both groups (p > 0.05), while there was no significant effect on mortality between both groups (p = 0.781). CONCLUSION: Levosimendan had improved hemodynamic parameters significantly with no effect on mortality compared to conventional inotropic agents in a patient with poor left ventricular function undergoing cardiac surgery.

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