Cardiac Control

Rushmer, Robert F.; Smith, Orville A.

doi:10.1152/physrev.1959.39.1.41

Cited by 174 publications

(26 citation statements)

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“…Since rate was comparable under all circumstances, changes in stroke volume generally reflected changes in cardiac output. These findings are in contrast to Rushmer and Smith's observations suggesting that stroke volume usually does not change during exercise (20). It may be that some of the discrepancy is explicable by the fact that, in our studies, both resting and exercise values were obtained in the upright position.…”

Section: C02 Tensioncontrasting

confidence: 99%

Cardiopulmonary Physiological Responses to Heavy Exercise in Patients With Anemia *

Sproule¹,

Mitchell²,

Miller³

1960

J. Clin. Invest.

131

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Section: C02 Tensioncontrasting

confidence: 99%

Cardiopulmonary Physiological Responses to Heavy Exercise in Patients With Anemia *

Sproule¹,

Mitchell²,

Miller³

1960

J. Clin. Invest.

131

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“…It is apparent from the work of nearly everyone who has examined the control of cardiac output from the point of view of both the circuit and the pump (1-4) that, if circuit parameters (resistances and compliances along the entire course of individual blood vessels and total blood volume) remain fixed, the only way to increase cardiac output significantly through a change in heart parameters (heart rate, diastolic volume, and force of contraction) alone is to decrease right atrial pressure. Yet ample evidence indicates that a variety of cardiac outputs can occur at the same right atrial pressure (5).…”

mentioning

confidence: 99%

Effect of Epinephrine on Pressure, Flow, and Volume Relationships in the Systemic Circulation of Dogs

Caldini

Permutt

Waddell

et al. 1974

Circulation Research

186

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The effect of epinephrine on peripheral circulation was studied in ten anesthetized open-chest dogs. Blood flow and right atrial pressure were independently controlled by a right heart bypass; changes in blood volume could be precisely determined from the changes occurring in the bypass reservoir. At constant blood flow and right atrial pressure, a constant infusion of epinephrine (5.8 Mg/kg min" 1 ) decreased blood volume by an average of 208 ml. During epinephrine infusion, the ratio of changes in blood volume to changes in blood flow measured at constant right atrial pressure, (A V/A0)p ra , decreased from 0.226 minutes to 0.153 minutes and the ratio of changes in blood volume to changes in right atrial pressure at constant blood flow, the vascular compliance, decreased from 27.1 ml/cm H 2 O to 20.7 ml/cm H 2 O. Transient changes in blood volume following a step decrease in right atrial pressure at constant blood flow showed that blood was draining from two vascular compartments with different time constants: 0.059 minutes and 0.388 minutes before epinephrine infusion and 0.058 minutes and 0.486 minutes during epinephrine infusion. We analyzed the data using a mathematical model of the peripheral circulation consisting of two compartments with different time constants. The analysis showed that the primary effect of epinephrine on the systemic circulation was to redistribute blood flow away from the compartment with the longest time constant. The reduction in (&VI&Q) Pra and the decrease in blood volume at constant flow and right atrial pressure were essentially determined by the change in flow distribution brought about by a change in arteriolar tone and not by a change in venous tone. KEY WORDS peripheral circulation vascular compliance cardiac output circulatory model venous resistance mean circulatory pressure venous return• For well over a hundred years, it has been recognized that the level of cardiac output is determined not only by the state of the heart but also by the state of the blood vessels (1,2). Grodins (3) has succinctly stated the reason behind this phenomenon: "... mechanical coupling between heart and circuit dictates that cardiac output is a function of both heart and circuit parameters." Guyton (4) has explained this relationship in more detail. The pressure of blood within the right atrium plays a unique role in the coupling between heart and blood vessels. On the one hand, the level of right atrial pressure relative to intrapleural pressure determines the filling pressure of the right ventricle. Therefore, right

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“…Rushmer and Smith have examined the literature and concluded that an increase in stroke volume is not an essential feature of the ventricular response in normal human subjects (1,2). Contrary views, particularly in the older literature, were attributed to differences in the technics used to measure cardiac output and in the degree of training of the subjects (1).…”

mentioning

confidence: 99%

The Effect of Changes in Posture and of Graded Exercise on Stroke Volume in Man *

Wang¹,

Marshall²,

Shepherd³

1960

J. Clin. Invest.

193

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Interest has been revived recently in the relative importance of changes in heart rate and stroke volume during exercise in man. Rushmer and Smith have examined the literature and concluded that an increase in stroke volume is not an essential feature of the ventricular response in normal human subjects (1, 2). Contrary views, particularly in the older literature, were attributed to differences in the technics used to measure cardiac output and in the degree of training of the subjects (1). However, in the studies reviewed by Rushmer, the subjects had exercised in various postures. This could have accounted for much of the apparent discrepancy (3), a point which Rushmer has now emphasized (4).The present investigation demonstrates the importance of the posture of the subject in the interpretation of changes in stroke volume from rest to exercise. The stroke volume increases only slightly once exercise has begun, regardless of the severity of the exercise or the position assumed by the subject. METHODSSeven healthy "untrained" men, aged 25 to 35 years, were studied. Cardiac output was measured by the indicator-dilution method. A cardiac catheter was placed with its tip in the superior vena cava. The indicator, cardio-green dye,1 was given in a dose of 7.5 mg by sudden injection from a specially calibrated syringe. The syringe was attached to the catheter throughout the experiment and was filled before each injection from a supply syringe connected to it by a three-way tap. Blood was sampled continuously for each dilution curve from the radial artery through a Wood oximeter at * This investigation was supported in part by a grant from the Minnesota Heart Association. rates of 28 to 50 ml per minute. The dilution curve was recorded on a photokymograph. Not more than 40 ml was withdrawn for any curve. On completion of each curve the blood was reinfused.Samples of blood were withdrawn from the radial artery before and after each experiment. Known amounts of dye were added to 10 ml aliquots of blood and the resulting mixtures were drawn through the cuvet oximeter to permit calibration of tIle dilution curves. The calibrations for the two samples invariably were close (Figure 1, upper panel) and were reproducible from day to day. Calibrations for blood from different subjects were similar. Figure 1

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Cardiac Control

Cited by 174 publications

References 0 publications

Cardiopulmonary Physiological Responses to Heavy Exercise in Patients With Anemia *

Cardiopulmonary Physiological Responses to Heavy Exercise in Patients With Anemia *

Effect of Epinephrine on Pressure, Flow, and Volume Relationships in the Systemic Circulation of Dogs

The Effect of Changes in Posture and of Graded Exercise on Stroke Volume in Man *

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