Cardiac limitation to maximal oxygen transport and changes in components after jogging across the US

Observations were made before and 3–5 days after prolonged endurance jogging an average of 42 miles/day, 6 days/wk for 2.5 mo by a young male adult who voluntarily initiated a run across the United States. Both arterial PO2 and lactic acid increased. In each instance, the first limitation in circulatory delivery of oxygen was a plateau in stroke volume and cardiac output. Afterward, pulse deficit and systemic arterial pressure fell with exercise and heart rate accelerated. Although there was no change in oxygen transport (Q X CAO2), a reduction in stroke volume was exactly balanced by a rise in arterial oxygen content. Vital capacity, residual volume, and total lung capacity and diffusion capacity for carbon monoxide, hematocrit, and red cell mass increased, while plasma volume diminished and heart size and total blood volume were unchanged.

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Effect of Exercise-Induced Reductions in Blood Volume on Cardiac Output and Oxygen Transport Capacity

Frontiers in Physiology ◽

10.3389/fphys.2021.679232 ◽

2021 ◽

Vol 12 ◽

Author(s):

Janis Schierbauer ◽

Torben Hoffmeister ◽

Gunnar Treff ◽

Nadine B. Wachsmuth ◽

Walter F. J. Schmidt

Keyword(s):

Cardiac Output ◽

Stroke Volume ◽

Oxygen Saturation ◽

Blood Volume ◽

Oxygen Transport ◽

Arterial Oxygen ◽

Peripheral Oxygen Saturation ◽

Heart Volume ◽

Arterial Oxygen Content ◽

Oxygen Transport Capacity

We wanted to demonstrate the relationship between blood volume, cardiac size, cardiac output and maximum oxygen uptake (V.O2max) and to quantify blood volume shifts during exercise and their impact on oxygen transport. Twenty-four healthy, non-smoking, heterogeneously trained male participants (27 ± 4.6 years) performed incremental cycle ergometer tests to determine V.O2max and changes in blood volume and cardiac output. Cardiac output was determined by an inert gas rebreathing procedure. Heart dimensions were determined by 3D echocardiography. Blood volume and hemoglobin mass were determined by using the optimized CO-rebreathing method. The V.O2max ranged between 47.5 and 74.1 mL⋅kg–1⋅min–1. Heart volume ranged between 7.7 and 17.9 mL⋅kg–1 and maximum cardiac output ranged between 252 and 434 mL⋅kg–1⋅min–1. The mean blood volume decreased by 8% (567 ± 187 mL, p = 0.001) until maximum exercise, leading to an increase in [Hb] by 1.3 ± 0.4 g⋅dL–1 while peripheral oxygen saturation decreased by 6.1 ± 2.4%. There were close correlations between resting blood volume and heart volume (r = 0.73, p = 0.002), maximum blood volume and maximum cardiac output (r = 0.68, p = 0.001), and maximum cardiac output and V.O2max (r = 0.76, p < 0.001). An increase in maximum blood volume by 1,000 mL was associated with an increase in maximum stroke volume by 25 mL and in maximum cardiac output by 3.5 L⋅min–1. In conclusion, blood volume markedly decreased until maximal exhaustion, potentially affecting the stroke volume response during exercise. Simultaneously, hemoconcentrations maintained the arterial oxygen content and compensated for the potential loss in maximum cardiac output. Therefore, a large blood volume at rest is an important factor for achieving a high cardiac output during exercise and blood volume shifts compensate for the decrease in peripheral oxygen saturation, thereby maintaining a high arteriovenous oxygen difference.

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Effects of Hematocrit Variations on Cerebral Blood Flow and Oxygen Transport in Ischemic Cerebrovascular Disease

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/jcbfm.1981.45 ◽

1981 ◽

Vol 1 (4) ◽

pp. 413-417 ◽

Cited By ~ 66

Author(s):

Masahito Kusunoki ◽

Kazufumi Kimura ◽

Masaichi Nakamura ◽

Yoshinari Isaka ◽

Shotaro Yoneda ◽

...

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Cerebrovascular Disease ◽

Oxygen Transport ◽

Oxygen Delivery ◽

Inverse Correlation ◽

Arterial Oxygen ◽

Brain Oxygenation ◽

Arterial Oxygen Content ◽

Ischemic Cerebrovascular Disease

The contribution of hematocrit (Ht) changes on cerebral blood flow (CBF) and brain oxygenation in ischemic cerebrovascular disease is still controversial. In the present study, effects of Ht variations on CBF and oxygen delivery were investigated in patients with ischemic cerebrovascular disease. CBF was measured by the Xe-133 intracarotid injection method in 27 patients, whose diagnoses included completed stroke, reversible ischemic neurological deficit, and transient ischemic attack. Ht values in the patients ranged from 31 to 53%. There was a significant inverse correlation between CBF and Ht in these Ht ranges. Oxygen delivery, i.e., the product of arterial oxygen content and CBF, increased with Ht elevation and reached the maximum level in the Ht range of 40–45% and then declined. The CBF-Ht and oxygen transport-Ht relations observed in our study were similar to those in the glass-tube model studies by other workers rather than to those in intact animal experiments. From these results, it is conceivable that in ischemic cerebrovascular disease, the vasomotor adjustment was impaired in such a manner that the relations among Ht, CBF, and oxygen delivery were different from those in healthy subjects. Further, an “optimal hematocrit” for brain oxygenation was also discussed.

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Systemic oxygen transport in induced normovolemic anemia and polycythemia

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1962.203.4.720 ◽

1962 ◽

Vol 203 (4) ◽

pp. 720-724 ◽

Cited By ~ 44

Author(s):

John F. Murray ◽

Philip Gold ◽

B. Lamar Johnson

Keyword(s):

Cardiac Output ◽

Oxygen Transport ◽

Arterial Oxygen Saturation ◽

Peripheral Resistance ◽

Arterial Oxygen ◽

Peripheral Vascular ◽

Arterial Oxygen Content ◽

Normovolemic Anemia ◽

Systemic Oxygen ◽

Negative Linear Relationship

The hemodynamic effects of normovolemic anemia and polycythemia were studied in 14 dogs. Anemia (5 dogs) and polycythemia (5 dogs) were induced by bleeding and simultaneously infusing dextran or packed erythrocytes. Measurements included cardiac output, arterial oxygen saturation, peripheral vascular resistance, and systemic oxygen transport (cardiac output X arterial oxygen content). Cardiac output had a significant negative linear relationship to hematocrit ( r = –0.74, P < 0.01) over the range studied (13–74%). Peripheral resistance fell 46% in anemic animals and increased 152% in four of five polycythemic animals. Arterial saturation was significantly correlated to changes in hematocrit ( r = 0.62, P < 0.01) and cardiac output ( r = –0.55, P < 0.01); these values were due primarily to the linearity encountered in the anemia experiments and a reversal in these relationships tended to occur at high hematocrits. Systemic oxygen transport was maximum at normal hematocrits and decreased in anemia and polycythemia. The data indicate that hemodynamic adjustments in normovolemic anemia and polycythemia are insufficient to maintain normal oxygen delivery.

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Effects of khellin on coronary blood flow and related metabolic functions

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1959.196.2.391 ◽

1959 ◽

Vol 196 (2) ◽

pp. 391-393 ◽

Cited By ~ 6

Author(s):

Richard L. Farrand ◽

Steven M. Horvath

Keyword(s):

Blood Flow ◽

Cardiac Output ◽

Coronary Blood Flow ◽

Control Period ◽

Systemic Arterial Pressure ◽

Arterial Oxygen ◽

Arterial Oxygen Content ◽

Fick Principle ◽

Metabolic Functions ◽

Pulmonary Arterial

Khellin, a drug employed as a coronary dilator, was tested to determine its effects on the cardiovascular system of the dog. Ten mongrel dogs were anesthetized with Nembutal and, after control observations were made, given an intravenous administration of 1 mg/kg body weight of khellin. Coronary blood flow and cardiac output samples were drawn during the control period and at 10, 40 and 80 minutes after administration of the drug Cardiac output was calculated by the direct Fick principle and coronary blood flow by the nitrous oxide method. There was a significant (5%) increase in the arterial oxygen content during the 10- and 40-minute intervals, but no change was observed at 80 minutes. An increase in arterial-mixed venous oxygen difference occurred at 40 and 80 minutes. No change in systemic arterial pressure or cardiac output was noted at any time. Coronary blood flow had decreased slightly at 80 minutes. A significant decrease in carbon dioxide content of the arterial, pulmonary arterial and coronary sinus blood was observed, possibly as a consequence of hyperventilation. Khellin appeared to alter the metabolism of the myocardial and splanchnic tissues.

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Model of oxygen transport and metabolism predicts effect of hyperoxia on canine muscle oxygen uptake dynamics

Journal of Applied Physiology ◽

10.1152/japplphysiol.00489.2007 ◽

2007 ◽

Vol 103 (4) ◽

pp. 1366-1378 ◽

Cited By ~ 14

Author(s):

Nicola Lai ◽

Gerald M. Saidel ◽

Bruno Grassi ◽

L. Bruce Gladden ◽

Marco E. Cabrera

Keyword(s):

Experimental Data ◽

Oxygen Uptake ◽

Oxygen Content ◽

Oxygen Transport ◽

Mechanistic Model ◽

Arterial Oxygen ◽

Cellular Respiration ◽

Arterial Oxygen Content ◽

Muscle Oxygen ◽

Muscle Oxygen Uptake

Previous studies have shown that increased oxygen delivery, via increased convection or arterial oxygen content, does not speed the dynamics of oxygen uptake, V̇o2m, in dog muscle electrically stimulated at a submaximal metabolic rate. However, the dynamics of transport and metabolic processes that occur within working muscle in situ is typically unavailable in this experimental setting. To investigate factors affecting V̇o2m dynamics at contraction onset, we combined dynamic experimental data across working muscle with a mechanistic model of oxygen transport and metabolism in muscle. The model is based on dynamic mass balances for O2, ATP, and PCr. Model equations account for changes in cellular ATPase, oxidative phosphorylation, and creatine kinase fluxes in skeletal muscle during exercise, and cellular respiration depends on [ADP] and [O2]. Model simulations were conducted at different levels of arterial oxygen content and blood flow to quantify the effects of convection and diffusion of oxygen on the regulation of cellular respiration during step transitions from rest to isometric contraction in dog gastrocnemius muscle. Simulations of arteriovenous O2 differences and V̇o2m dynamics were successfully compared with experimental data (Grassi B, Gladden LB, Samaja M, Stary CM, Hogan MC. J Appl Physiol 85: 1394–1403, 1998; and Grassi B, Gladden LB, Stary CM, Wagner PD, Hogan MC. J Appl Physiol 85: 1404–1412, 1998), thus demonstrating the validity of the model, as well as its predictive capability. The main findings of this study are: 1) the estimated dynamic response of oxygen utilization at contraction onset in muscle is faster than that of oxygen uptake; and 2) hyperoxia does not accelerate the dynamics of diffusion and consequently muscle oxygen uptake at contraction onset due to the hyperoxia-induced increase in oxygen stores. These in silico derived results cannot be obtained from experimental observations alone.

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Transcriptomic Markers of Recombinant Human Erythropoietin Micro-Dosing in Thoroughbred Horses

Genes ◽

10.3390/genes12121874 ◽

2021 ◽

Vol 12 (12) ◽

pp. 1874

Author(s):

Anna R. Dahlgren ◽

Heather K. Knych ◽

Rick M. Arthur ◽

Blythe P. Durbin-Johnson ◽

Carrie J. Finno

Keyword(s):

Recombinant Human Erythropoietin ◽

Mononuclear Cells ◽

Cell Mass ◽

Arterial Oxygen ◽

Horse Racing ◽

Peripheral Blood Mononuclear ◽

Arterial Oxygen Content ◽

Human Erythropoietin ◽

Thoroughbred Horses ◽

Important Concern

Recombinant human erythropoietin (rHuEPO) is a well-known performance enhancing drug in human athletes, and there is anecdotal evidence of it being used in horse racing for the same purpose. rHuEPO, like endogenous EPO, increases arterial oxygen content and thus aerobic power. Micro-doping, or injecting smaller doses over a longer period of time, has become an important concern in both human and equine athletics since it is more difficult to detect. Horses offer an additional challenge of a contractile spleen, thus large changes in the red blood cell mass occur naturally. To address the challenge of detecting rHuEPO doping in horse racing, we determined the transcriptomic effects of rHuEPO micro-dosing over seven weeks in exercised Thoroughbreds. RNA-sequencing of peripheral blood mononuclear cells isolated at several time points throughout the study identified three transcripts (C13H16orf54, PUM2 and CHTOP) that were significantly (PFDR < 0.05) different between the treatment groups across two or three time point comparisons. PUM2 and CHTOP play a role in erythropoiesis while not much is known about C13H16orf54, but it is primarily expressed in whole blood. However, gene expression differences were not large enough to detect via RT-qPCR, thereby precluding their utility as biomarkers of micro-doping.

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Comparison of transfusion with DCLHb or pRBCs for treatment of intraoperative anemia in sheep

Journal of Applied Physiology ◽

10.1152/jappl.2002.92.1.343 ◽

2002 ◽

Vol 92 (1) ◽

pp. 343-353 ◽

Cited By ~ 16

Author(s):

Luiz A. Vane ◽

J. Sean Funston ◽

Robert Kirschner ◽

Don Harper ◽

Donald J. Deyo ◽

...

Keyword(s):

Intensive Care Unit ◽

Blood Cells ◽

Volume Expansion ◽

Filling Pressure ◽

Arterial Oxygen ◽

Control Group ◽

Hemodynamic Effects ◽

Total Blood ◽

Arterial Oxygen Content ◽

Packed Red Blood Cells

Isoflurane-anesthetized sheep were transfused with packed red blood cells (pRBCs) or diaspirin cross-linked hemoglobin (DCLHb) for treatment of intraoperative hemorrhage. A rapid 15-min hemorrhage with lactated Ringer (LR) infusion maintained filling pressure at baseline and reduced blood hemoglobin (Hb) to ∼5 g/dl. Sheep received 2 g/kg Hb, DCLHb ( n = 6), or pRBCs ( n = 7); control group received LR alone ( n = 6). After 2 h, anesthesia was discontinued; sheep were monitored in the animal intensive care unit for 48 h. DCLHb expanded blood volume more, but increased total blood Hb less, than pRBCs. Lower Hb and increased methemoglobin resulted in lower arterial oxygen content compared with the pRBCs. DCLHb caused pulmonary hypertension (from 13 to 30 mmHg) and elevated filling pressure (from 6 to 15 mmHg). Cardiac outputs (CO) were similar for all groups during anesthesia; however, during recovery CO increased only in the LR and packed pRBCs groups. DCLHb may limit the reflex ability to increase CO after volume expansion. Hemodynamic effects of DCLHb may be exaggerated when infused after large-volume LR.

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The role of catecholamines in erythrocyte pH regulation and oxygen transport in rainbow trout (Salmo gairdneri) during exercise

Journal of Experimental Biology ◽

10.1242/jeb.122.1.139 ◽

1986 ◽

Vol 122 (1) ◽

pp. 139-148 ◽

Cited By ~ 7

Author(s):

D. R. Primmett ◽

D. J. Randall ◽

M. Mazeaud ◽

R. G. Boutilier

Keyword(s):

Rainbow Trout ◽

Oxygen Transport ◽

Ph Regulation ◽

Arterial Oxygen ◽

Salmo Gairdneri ◽

Swimming Velocity ◽

Oxygen Binding ◽

Arterial Oxygen Content ◽

Burst Swimming ◽

Critical Swimming Velocity

Rainbow trout were subjected to burst swimming to exhaustion followed by 4 h aerobic swimming at 80% critical swimming velocity. Severe physiological disturbances, including a marked plasma acidosis caused by the burst swim, were corrected during the 4 h of subsequent aerobic exercise. Erythrocytic pH and arterial oxygen content increased, even though plasma pH was reduced. We suggest that the increase in erythrocytic pH was caused by the action of elevated adrenaline and noradrenaline levels in the blood acting on beta-adrenergic receptors on the trout red blood cell, causing the cell to swell and raising intracellular pH, offsetting any effect of a reduction of plasma pH on erythrocyte pH and haemoglobin-oxygen binding. Propranolol blocked the action of catecholamines on trout erythrocytes. We conclude that catecholamines play an important role in maintaining oxygen transport to aerobic muscles, following burst swimming and the associated acidotic conditions.

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Level of ventilation influences the cardiovascular response to hypoxemia in lambs

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y04-130 ◽

2004 ◽

Vol 82 (12) ◽

pp. 1113-1117 ◽

Cited By ~ 1

Author(s):

James E Fewell ◽

Bonnie J Taylor

Keyword(s):

Blood Pressure ◽

Heart Rate ◽

Cardiac Output ◽

Oxygen Transport ◽

Cardiovascular Response ◽

Recovery Period ◽

Arterial Oxygen ◽

Arterial Oxygen Content ◽

Systemic Oxygen ◽

Cardiovascular Variables

Newborn animals of a number of species display a brisk increase in ventilation followed by a gradual drop toward or below baseline within minutes of exposure to acute hypoxemia. Heart rate and cardiac output (a determinant of systemic oxygen transport along with the arterial oxygen content) appear to follow a similar pattern, but whether or not the cardiovascular response is influenced by the respiratory response is unknown. We therefore carried out experiments in which the level of ventilation was controlled during normoxemia and hypoxemia to test the hypothesis that the level of ventilation influences the cardiovascular response to acute hypoxemia. Six lambs ranging in age from 17 to 22 days were anesthetized, tracheostomized, and instrumented for measurement of cardiovascular variables. A recovery period of at least 3 days was allowed before the study when each lamb was artificially ventilated with a mixture of 70% nitrous oxide and 30% oxygen in nitrogen. A control respiratory frequency (f) of 30 breaths per min was set and a control tidal volume (VT) was chosen to achieve normocapnia. Cardiovascular measurements were made during normoxemia and hypoxemia (FIO2 0.10) 5 min after f or VT was changed to simulate a decrease, no change, or an increase in ventilation. During normoxemia, the level of ventilation had little effect on the measured cardiovascular variables. At control levels of ventilation, hypoxemia caused an increase in cardiac output that was due solely to an increase in stroke volume as heart rate decreased; blood pressure was unchanged. Increasing ventilation during hypo xemia did not augment cardiac output or alter blood pressure as compared with that observed at control levels of ventilation. Decreasing ventilation during hypoxemia, however, decreased cardiac output due to a profound bradycardia; blood pressure increased significantly. Our data provide evidence that the level of ventilation significantly influences the cardiovascular response to hypoxemia in young lambs.Key words: newborn, hypoxemia, cardiovascular, respiration, systemic oxygen transport.

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