Effects of exercise and heat stress on regional blood flow in pregnant sheep

1986 ◽  
Vol 60 (5) ◽  
pp. 1759-1764 ◽  
Author(s):  
A. W. Bell ◽  
J. R. Hales ◽  
A. A. Fawcett ◽  
R. B. King
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Heat Stress ◽  
Regional Blood Flow ◽  
Heat Exposure ◽  
Respiratory Muscles ◽  
Fold Increase ◽  
Pregnant Uterus ◽  
Pregnant Sheep ◽  
Exercise Induced

Radioactive microspheres were used to measure cardiac output and blood flow to most major tissues, including those in the pregnant uterus, in late-pregnant ewes at rest and during treadmill exercise (approximately 3-fold increase in metabolic rate for 30 min) in thermoneutral (TN) (dry bulb temperature (Tdb) = 13 degrees C, wet bulb temperature (Twb) = 10 degrees C) and mildly hot (MH) (Tdb = 40 degrees C, Twb = 27 degrees C) environments. Exercise caused major increases in blood flow to respiratory muscles, nonrespiratory limb muscles, and adipose tissue, and flow was decreased to some gastrointestinal tissues, spleen, pancreas, and to placental and nonplacental tissues in the pregnant uterus. Heat exposure had relatively little effect on these exercise-induced changes, except that flow was further increased in the respiratory muscles. Results are compared with those of a similar study on nonpregnant sheep in which changes in muscle, skin, and visceral flows during exercise were attenuated by heat exposure. It is suggested that redistribution of blood flow from the pregnant uterus, which in resting ewes took 22% of cardiac output, is a significant buffer against the potentially deleterious effects of combined exercise and heat stress on blood flow to exercising muscles and thermoregulatory tissues.

Influence of heat stress on exercise-induced changes in regional blood flow in sheep

1983 ◽  
Vol 55 (6) ◽  
pp. 1916-1923 ◽  
Author(s):  
A. W. Bell ◽  
J. R. Hales ◽  
R. B. King ◽  
A. A. Fawcett
Keyword(s):  
Blood Flow ◽  
Skin Blood Flow ◽  
Regional Blood Flow ◽  
Respiratory Muscles ◽  
Fold Increase ◽  
Respiratory Alkalosis ◽  
Upper Respiratory Tract ◽  
Hindlimb Muscles ◽  
Exercise Induced ◽  
Induced Changes

Radioactive microspheres were used to measure cardiac output and blood flow to most major tissues in sheep at rest and during treadmill exercise (3- to 6-fold increase in metabolic rate for 30 min) in thermoneutral (TN) [dry bulb temperature (Tdb) = 16 degrees C, wet bulb temperature (Twb) = 12 degrees C] and mildly hot (MH) (Tdb = 40 degrees C, Twb = 23 degrees C) environments. During exercise, rectal temperature increased more under MH than under TN conditions; exercise-induced changes in the major central cardiovascular parameters were unaffected by MH. Exercise in TN caused mild hypocapnia, and in MH, severe respiratory alkalosis. Skin blood flow in the torso decreased during exercise in TN and MH. Extremity skin blood flow was increased by heat but not exercise. Exercise-induced increases in flows to respiratory muscles and upper respiratory tract tissues were greatly enhanced in MH. Exercise caused large increases in blood flow to fore- and hindlimb muscles, which were less in MH than in TN. Effects of MH on exercise-induced changes in flow to these and other tissues (e.g., abdominal viscera and adipose tissue) are discussed in terms of the conflicting requirements of energy expenditure and body temperature regulation during exercise in sheep and other species, particularly humans.

Fever and regional blood flows in wethers and parturient ewes

1988 ◽  
Vol 65 (1) ◽  
pp. 165-172 ◽  
Author(s):  
C. M. Blatteis ◽  
J. R. Hales ◽  
A. A. Fawcett ◽  
T. A. Mashburn
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Regional Blood Flow ◽  
Flow Distribution ◽  
Full Term ◽  
Blood Flows ◽  
Pregnant Sheep ◽  
Regional Blood Flows ◽  
Placental Blood ◽  
Placental Blood Flow

To determine whether the reported absence of fever in full-term-pregnant ewes might be associated with shifts of regional blood flows from thermogenic tissues to placenta during this critical period, fevers were induced twice by injections of Escherichia coli lipopolysaccharide (LPS, 0.25 microgram/kg iv) into each of six Merino ewes from 8 to 1 days prepartum, and their regional blood flow distribution was measured with radioactive, 15-microns-diam microspheres before and during the rise in fever (when their rectal temperature had risen approximately 0.4 degree C). Unexpectedly, fever always developed, rising to heights not significantly different at any time before parturition [4-8 days prepartum = 0.81 +/- 0.23 degree C (SE); 1-3 days prepartum = 0.75 +/- 0.17 degree C) and similar to those in three wethers treated similarly (0.90 +/- 0.10 degree C). Generally, during rising fever, blood flow in the ewes shifted away from heat loss tissues (e.g., skin, nose) to heat production tissues (e.g., shivering muscle, fat) and cardiac output increased; blood flow through redistribution organs (e.g., splanchnic bed) decreased. The reverse occurred during defervescence. Utero-placental blood flow remained high in the febrile ewes. These regional blood flow distributions during febrigenesis and lysis are essentially the same as those during exposures to ambient cold and heat, respectively. Some differences in the responses of cardiac output and its redistribution, however, were apparent between wethers and pregnant ewes. We conclude that 1) the previously reported "absence of fever in the full-term-pregnant sheep" should not be regarded as a general phenomenon and 2) full-term-pregnant sheep support fever production without sacrificing placental blood flow.

Hyperinflation with intrinsic PEEP and respiratory muscle blood flow

1994 ◽  
Vol 77 (5) ◽  
pp. 2440-2448 ◽  
Author(s):  
Y. Kawagoe ◽  
S. Permutt ◽  
H. E. Fessler
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Respiratory Muscle ◽  
Respiratory Muscles ◽  
Fold Increase ◽  
Transversus Abdominis ◽  
Resistive Load ◽  
Transdiaphragmatic Pressure ◽  
Circulatory Effects ◽  
Inspiratory Work

Increased end-expiratory lung volume and intrinsic positive end-expiratory pressure (PEEP) are common in obstructive lung disease, especially during exacerbations or exercise. This loads the respiratory muscles and may also stress the circulatory system, causing a reduction or redistribution of cardiac output. We measured the blood flow to respiratory muscles and systemic organs using colored microspheres in 10 spontaneously breathing anesthetized tracheotomized dogs. Flows during baseline breathing (BL) were compared with those during hyperinflation (HI) induced by a mechanical analogue of airway closure and with those during an inspiratory resistive load (IR) that produced an equivalent increase in inspiratory work and time-integrated transdiaphragmatic pressure. Cardiac output was unchanged during IR (3.19 +/- 0.27 l/min at BL, 3.09 +/- 0.34 l/min during IR) but was reduced during HI (2.14 +/- 0.29 l/min; P < 0.01). Among the organs studied, flow was unaltered by IR but decreased to the liver and pancreas and increased to the brain during HI. For the respiratory muscles, flow to the diaphragm increased during IR. However, despite a 1.9-fold increase in inspiratory work per minute and a 2.5-fold increase in integrated transdiaphragmatic pressure during HI, blood flow to the diaphragm was unchanged and flow to the scalenes and sternomastoid fell. The only respiratory muscle to which flow increased during HI was the transversus abdominis, an expiratory muscle. We conclude that the circulatory effects of hyperinflation in this model impair inspiratory muscle perfusion and speculate that this may contribute to respiratory muscle dysfunction in hyperinflated states.

Regional blood flow and vascular resistance in response to oxytocin in the pregnant sheep and dog

1961 ◽  
Vol 16 (6) ◽  
pp. 1087-1092 ◽  
Author(s):  
N. S. Assali ◽  
L. Holm ◽  
H. Parker
Keyword(s):  
Blood Flow ◽  
Vascular Resistance ◽  
Regional Blood Flow ◽  
Uterine Blood Flow ◽  
Pregnant Uterus ◽  
Blood Flows ◽  
Uterine Contractions ◽  
Intravenous Drip ◽  
Pregnant Sheep ◽  
Regional Vascular Resistance

The effects of oxytocin on regional blood flow and regional vascular resistance were investigated in a group of pregnant ewes and bitches not in labor and in another group in early labor. Single injections or intravenous drip infusion did not change significantly arterial pressure, cardiac output, electrocardiogram, and renal, iliac, femoral, and carotid blood flows in any of the animals studied. The effects on the pregnant uterus were negligible before the onset of spontaneous labor. Only when the animal was in labor did oxytocin produce an increase in uterine contractions accompanied by a significant decrease in uterine blood flow. The data indicate that in the pregnant sheep and dog the circulatory action of oxytocin is limited to the pregnant uterus in labor and that the decrease in blood flow is probably due to an increase in intramural vascular resistance caused by the contracting myometrium around the uterine arterioles. Submitted on May 5, 1961

THE EFFECT OF EXERCISE ON THE CARDIAC OUTPUT AND BLOOD FLOW DISTRIBUTION OF THE LARGESCALE SUCKER CATOSTOMUS MACROCHEILUS

1993 ◽  
Vol 183 (1) ◽  
pp. 301-321 ◽  
Author(s):  
A. S. Kolok ◽  
M. R. Spooner ◽  
A. P. Farrell
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Swimming Performance ◽  
Flow Distribution ◽  
Fold Increase ◽  
Blood Flow Distribution ◽  
Dramatic Decline ◽  
Red Muscle ◽  
Catostomus Macrocheilus ◽  
A Current

Cardiac output (Q.) and blood flow distribution were measured in adult largescale suckers at rest and while swimming. Cardiac output was directly measured using an ultrasonic flowprobe in fish during the summer (16°C), fall (10°C) and winter (5°C). Largescale suckers were adept at holding station against a current without swimming and, when engaged in this behavior, they did not significantly increase Q. relative to that found in fish in still water. When fish began to swim, Q. increased significantly. From 16 to 10°C, the critical swimming speed (Ucrit), maximum Q. and scope for Q. of the suckers did not change. However, from 10 to 5°C all three traits were significantly reduced. Thus, these fish respond to variation in water temperature in two different ways. From 16 to 10°C, the fish compensate perfectly for the change in temperature with respect to cardiac and swimming performance. From 10 to 5°C, however, largescale suckers experience a dramatic decline in cardiac and swimming performance that may be associated with a quiescent overwintering strategy. Blood flow distribution in the fish at rest and while swimming was measured at 16°C using injection of colored microspheres. In the resting fish, over 10 % of the microspheres were recovered from the kidney and over 43 % were recovered from white muscle. When the fish were swimming, there was a 60-fold increase in blood flow to the red muscle while blood flow to all other tissues remained consistent with that at rest.

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