Inert Gas Washout Measurement of Muscle Blood Flow Distribution — Roles of Hypoxia and Diffusion Limitation

The purpose of this study was to determine whether reduction in apparent muscle O2 diffusing capacity (Dmo2) calculated during reduced blood flow conditions in maximally working muscle is a reflection of alterations in blood flow distribution. Isolated dog gastrocnemius muscle (n = 6) was stimulated for 3 min to achieve peak O2 uptake (VO2) at two levels of blood flow (controlled by pump perfusion): control (C) conditions at normal perfusion pressure (blood flow = 111 +/- 10 ml.100 g-1.min-1) and reduced blood flow treatment [ischemia (I); 52 +/- 6 ml.100 g-1.min-1]. In addition, maximal vasodilation was achieved by adenosine (A) infusion (10(-2)M) at both levels of blood flow, so that each muscle was subjected randomly to a total of four conditions (C, CA, I, and IA; each separated by 45 min of rest). Muscle blood flow distribution was measured with 15-microns-diameter colored microspheres. A numerical integration technique was used to calculate Dmo2 for each treatment with use of a model that calculates O2 loss along a capillary on the basis of Fick's law of diffusion. Peak VO2 was reduced significantly (P < 0.01) with ischemia and was unchanged by adenosine infusion at either flow rate (10.6 +/- 0.9, 9.7 +/- 1.0, 6.7 +/- 0.2, and 5.9 +/- 0.8 ml.100 g-1.min-1 for C, CA, I, and IA, respectively). Dmo2 was significantly lower by 30-35% (P < 0.01) when flow was reduced (except for CA vs. I; 0.23 +/- 0.03, 0.20 +/- 0.02, 0.16 +/- 0.01, and 0.13 +/- 0.01 ml.100 g-1.min-1.Torr-1 for C, CA, I, and IA, respectively). As expressed by the coefficient of variation (0.45 +/- 0.04, 0.47 +/- 0.04, 0.55 +/- 0.03, and 0.53 +/- 0.04 for C, CA, I, and IA, respectively), blood flow heterogeneity per se was not significantly different among the four conditions when examined by analysis of variance. However, there was a strong negative correlation (r = 0.89, P < 0.05) between Dmo2 and blood flow heterogeneity among the four conditions, suggesting that blood flow redistribution (likely a result of a decrease in the number of perfused capillaries) becomes an increasingly important factor in the determination of Dmo2 as blood flow is diminished.

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Influence of simulated microgravity on cardiac output and blood flow distribution during exercise

Journal of Applied Physiology ◽

10.1152/jappl.1995.79.5.1762 ◽

1995 ◽

Vol 79 (5) ◽

pp. 1762-1768 ◽

Cited By ~ 38

Author(s):

C. R. Woodman ◽

L. A. Sebastian ◽

C. M. Tipton

Keyword(s):

Blood Flow ◽

Cardiac Output ◽

Aerobic Capacity ◽

Muscle Blood Flow ◽

Knee Extensor ◽

Flow Distribution ◽

Blood Flow Distribution ◽

Heavy Exercise ◽

Cage Control ◽

Impaired Ability

Rats exposed to simulated conditions of microgravity by head-down suspension (HDS) exhibit reductions in aerobic capacity. This may be due to an impaired ability to augment cardiac output and to redistribute blood flow during exercise. The purpose of this investigation was to measure cardiac output and blood flow distribution in rats that were exposed to 14 days of HDS or cage control conditions. Measurements were obtained at rest and during light-intensity (15 m/min) and heavy-intensity (25 m/min; 10% grade) treadmill exercise. Cardiac output was similar in HDS and cage control rats at rest and light exercise but was significantly lower in HDS rats (-33%) during heavy exercise. Soleus muscle blood flow (ml/min) was lower at rest and during exercise in HDS rats; however, when expressed relative to muscle mass (ml.min-1.100 g-1), soleus blood flow was lower only during light exercise. Plantaris muscle blood flow was lower in HDS rats during heavy exercise. Blood flow to the ankle flexor, knee extensor, and knee flexor muscles was not altered by HDS. Blood flow to the spleen and kidney was significantly higher in HDS rats. It was concluded that the reduction in aerobic capacity associated with HDS is due in part to an impaired ability to augment cardiac output during exercise.

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Critical speed in the rat: implications for hindlimb muscle blood flow distribution and fibre recruitment

The Journal of Physiology ◽

10.1113/jphysiol.2010.198382 ◽

2010 ◽

Vol 588 (24) ◽

pp. 5077-5087 ◽

Cited By ~ 65

Author(s):

Steven W. Copp ◽

Daniel M. Hirai ◽

Timothy I. Musch ◽

David C. Poole

Keyword(s):

Blood Flow ◽

Critical Speed ◽

Muscle Blood Flow ◽

Flow Distribution ◽

Blood Flow Distribution ◽

Hindlimb Muscle

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Cardiac Output and Regional Blood Flow in Gills and Muscles after Exhaustive Exercise in Rainbow Trout (Salmo Gairdneri)

Journal of Experimental Biology ◽

10.1242/jeb.105.1.1 ◽

1983 ◽

Vol 105 (1) ◽

pp. 1-14

Author(s):

PETER NEUMANN ◽

GEORGE F. HOLETON ◽

NORBERT HEISLER

Keyword(s):

Blood Flow ◽

Cardiac Output ◽

Rainbow Trout ◽

Muscle Blood Flow ◽

Recovery Period ◽

Flow Distribution ◽

Strenuous Exercise ◽

Salmo Gairdneri ◽

Diffusion Resistance ◽

Blood Flow Distribution

Rainbow trout (Salmo gairdneri) were electrically stimulated to exhausting activity and the changes in cardiac output and blood flow distribution to gills and systemic tissues resulting from the developing severe lactacidosis were repeatedly measured by the microsphere method (15 μm). Determination of cardiac output by application of the Fick principle resulted in values not significantly different from cardiac output measured by the indicator dilution technique, suggesting that cutaneous respiration, oxygen consumption, and arterio-venous shunting were insignificant under these conditions. Following muscular activity, cardiac output was elevated by up to 60%. In the gills, the blood flow distribution in the gill arches showed a consistent pattern, even during lactacidosis, with a higher perfusion in gill arches II and III, and in the middle sections of individual gills. Blood flow to white and red muscle was increased much more than cardiac output (+230 and +490%, respectively) such that blood flow to other tissues was actually reduced. We conclude that the elimination of lactate from muscle cells during the recovery period from strenuous exercise is delayed, not as a result of an impaired post-exercise muscle blood flow, but probably as a result of a high diffusion resistance in the cell membrane. Note: Deceased.

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Vasoconstrictor role for vasopressin in conscious, sodium-depleted rats

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1987.253.4.h763 ◽

1987 ◽

Vol 253 (4) ◽

pp. H763-H769

Author(s):

B. Jover ◽

M. Dupont ◽

A. Mimran ◽

R. Woods ◽

B. McGrath

Keyword(s):

Blood Flow ◽

Regional Blood Flow ◽

Muscle Blood Flow ◽

Flow Distribution ◽

Renin Angiotensin System ◽

Adrenergic System ◽

Blood Flow Distribution ◽

Sprague Dawley ◽

Vascular Bed ◽

Renal Vascular

To define the role of vasopressin as a vasoconstrictor hormone in sodium depletion, systemic hemodynamics and regional blood flow distribution were examined in conscious Sprague-Dawley rats after 6 days of a low-sodium diet. Studies were performed after selective or combined blockade with the vasopressin antagonist [d(CH2)5Tyr(Me)]AVP (AVPA), enalaprilat (CEI), and phentolamine (PHENTOL). Plasma levels of vasopressin were increased significantly after CEI and increased further after PHENTOL and CEI plus PHENTOL. AVPA had no effect on blood pressure, whether given alone or in the presence of PHENTOL, CEI, or CEI plus PHENTOL. Significant falls in peripheral vascular resistance associated with reflex increases in cardiac output were observed when AVPA was given to animals pretreated with either CEI or PHENTOL but not both. AVPA alone produced no significant changes in regional blood flow distribution, but a vasoconstrictor action of vasopressin in the renal vascular bed was revealed after prior treatment with CEI or PHENTOL. Muscle blood flow was also increased in the PHENTOL plus AVPA group compared with the PHENTOL group. No significant additional effects of AVPA were revealed by pretreatment with CEI, PHENTOL, or CEI plus PHENTOL for mesenteric, hepatic, splenic, or cerebral vascular beds. It is suggested that vasopressin acts as a vasoconstrictor hormone in conscious sodium-depleted rats when either the renin-angiotensin system or alpha-adrenergic system is inhibited but not when both systems are blocked. The renal vascular bed is an important site for vasopressin-induced vasoconstriction under these circumstances.

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Oxygen consumption and distribution of blood flow in rats climbing a laddermill

Journal of Applied Physiology ◽

10.1152/jappl.1990.68.1.241 ◽

1990 ◽

Vol 68 (1) ◽

pp. 241-247 ◽

Cited By ~ 6

Author(s):

K. I. Norton ◽

M. T. Jones ◽

R. B. Armstrong

Keyword(s):

Blood Flow ◽

Fiber Type ◽

Muscle Blood Flow ◽

Flow Distribution ◽

Treadmill Running ◽

Blood Flow Distribution ◽

Sprague Dawley ◽

Circulatory Response ◽

Blood Flows ◽

Sprague Dawley Rats

The purpose of this study was threefold: 1) to determine whether untrained rats that refused to run on treadmill would climb on a laddermill (75 degrees incline); 2) to determine O2 consumption (VO2) in untrained rats as a function of laddermill climbing speed; and 3) to determine whether the circulatory response of untrained rats to laddermill climbing is similar to that previously reported for treadmill running at an equivalent VO2. Eighteen female Sprague-Dawley rats that would not perform on a treadmill as part of another study were used to measure VO2 as a function of laddermill speed (5-17 m/min). Data were obtained from all 18 rats; VO2 increased linearly as a function of laddermill speed (r = 0.83, y = 3.0 x + 63.2). Twenty-four female Sprague-Dawley rats that also refused to run on a treadmill were used to measure mean arterial pressure, heart rate, and blood flow distribution (with microspheres) during climbing at 5 and 10 m/min. These exercise intensities were metabolically equivalent to level treadmill running at 45 and 60 m/min (VO2 approximately 78 and 93 ml.min-1.kg-1, respectively). Of the 24 animals, 23 were willing to climb. Mean arterial pressures were higher (approximately 10%) during laddermill climbing than during equivalent treadmill running, but heart rates were the same. General blood flow distribution among muscles as a function of fiber type (with red muscles receiving higher flows) and between muscles and visceral tissues (muscle blood flow increased as a function of exercise intensity while visceral blood flows decreased) were similar to data for rats running on the level.(ABSTRACT TRUNCATED AT 250 WORDS)

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Comparison of exogenous adenosine and voluntary exercise on human skeletal muscle perfusion and perfusion heterogeneity

Journal of Applied Physiology ◽

10.1152/japplphysiol.00745.2009 ◽

2010 ◽

Vol 108 (2) ◽

pp. 378-386 ◽

Cited By ~ 47

Author(s):

Ilkka Heinonen ◽

Jukka Kemppainen ◽

Kimmo Kaskinoro ◽

Juha E. Peltonen ◽

Ronald Borra ◽

...

Keyword(s):

Blood Flow ◽

High Intensity ◽

Muscle Blood Flow ◽

Flow Distribution ◽

Voluntary Exercise ◽

Adenosine Infusion ◽

Blood Flow Distribution ◽

Flow Heterogeneity ◽

Exercise Hyperemia ◽

Exercise Induced

Adenosine is a widely used pharmacological agent to induce a “high-flow” control condition to study the mechanisms of exercise hyperemia, but it is not known how well an adenosine infusion depicts exercise-induced hyperemia, especially in terms of blood flow distribution at the capillary level in human muscle. Additionally, it remains to be determined what proportion of the adenosine-induced flow elevation is specifically directed to muscle only. In the present study, we measured thigh muscle capillary nutritive blood flow in nine healthy young men using PET at rest and during the femoral artery infusion of adenosine (1 mgmin−1l thigh volume−1), which has previously been shown to induce a maximal whole thigh blood flow of ∼8 l/min. This response was compared with the blood flow induced by moderate- to high-intensity one-leg dynamic knee extension exercise. Adenosine increased muscle blood flow on average to 40 ± 7 ml·min−1·100 g muscle−1 with an aggregate value of 2.3 ± 0.6 l/min for the whole thigh musculature. Adenosine also induced a substantial change in blood flow distribution within individuals. Muscle blood flow during the adenosine infusion was comparable with blood flow in moderate- to high-intensity exercise (36 ± 9 ml·min−1·100 g muscle−1), but flow heterogeneity was significantly higher during the adenosine infusion than during voluntary exercise. In conclusion, a substantial part of the flow increase in the whole limb blood flow induced by a high-dose adenosine infusion is conducted through the physiological non-nutritive shunt in muscle and/or also through tissues of the limb other than muscle. Additionally, an intra-arterial adenosine infusion does not mimic exercise hyperemia, especially in terms of muscle capillary flow heterogeneity, while the often-observed exercise-induced changes in capillary blood flow heterogeneity likely reflect true changes in nutritive flow linked to muscle fiber and vascular unit recruitment.

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Competition for blood flow distribution between respiratory and locomotor muscles: implications for muscle fatigue

Journal of Applied Physiology ◽

10.1152/japplphysiol.00189.2018 ◽

2018 ◽

Vol 125 (3) ◽

pp. 820-831 ◽

Cited By ~ 27

Author(s):

A. William Sheel ◽

Robert Boushel ◽

Jerome A. Dempsey

Keyword(s):

Blood Flow ◽

Muscle Fatigue ◽

Respiratory Muscle ◽

Muscle Blood Flow ◽

Respiratory Muscles ◽

Flow Distribution ◽

Muscle Afferents ◽

Afferent Feedback ◽

Blood Flow Distribution ◽

Arterial Blood

Sympathetically induced vasoconstrictor modulation of local vasodilation occurs in contracting skeletal muscle during exercise to ensure appropriate perfusion of a large active muscle mass and to maintain also arterial blood pressure. In this synthesis, we discuss the contribution of group III-IV muscle afferents to the sympathetic modulation of blood flow distribution to locomotor and respiratory muscles during exercise. This is followed by an examination of the conditions under which diaphragm and locomotor muscle fatigue occur. Emphasis is given to those studies in humans and animal models that experimentally changed respiratory muscle work to evaluate blood flow redistribution and its effects on locomotor muscle fatigue, and conversely, those that evaluated the influence of coincident limb muscle contraction on respiratory muscle blood flow and fatigue. We propose the concept of a “two-way street of sympathetic vasoconstrictor activity” emanating from both limb and respiratory muscle metaboreceptors during exercise, which constrains blood flow and O2 transport thereby promoting fatigue of both sets of muscles. We end with considerations of a hierarchy of blood flow distribution during exercise between respiratory versus locomotor musculatures and the clinical implications of muscle afferent feedback influences on muscle perfusion, fatigue, and exercise tolerance.

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Absorption of various inert gases from subcutaneous gas pockets in rats

Journal of Applied Physiology ◽

10.1152/jappl.1962.17.2.268 ◽

1962 ◽

Vol 17 (2) ◽

pp. 268-274 ◽

Cited By ~ 45

Author(s):

J. Piiper ◽

R. E. Canfield ◽

H. Rahn

Keyword(s):

Experimental Data ◽

Blood Flow ◽

Nitrous Oxide ◽

Absorption Rate ◽

Sulfur Hexafluoride ◽

Inert Gases ◽

Inert Gas ◽

Diffusion Limitation ◽

Tissue Layer ◽

And Diffusion

A study was made of absorption of the inert gases, helium, argon, hydrogen, nitrogen, sulfur hexafluoride, nitrous oxide, and cyclopropane, from subcutaneous gas pockets in rats breathing oxygen. For interpretation of the data a method of analysis was devised which permitted distinction between perfusion and diffusion as factors limiting the absorption rate. Application of this method to the experimental data leads to the conclusion that both perfusion and diffusion limitation were effective in determining the absorption rates of the inert gases, diffusion limitation being the more important factor. The blood flow responsible for the uptake of inert gas from the gas pocket, and the thickness of the tissue layer between blood and pocket gas could be crudely estimated. Submitted on October 9, 1961

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