Contraction-dependent modulations in regional diaphragmatic blood flow

1990 ◽  
Vol 68 (5) ◽  
pp. 2019-2028 ◽  
Author(s):  
F. Hu ◽  
A. Comtois ◽  
A. E. Grassino
Keyword(s):  
Blood Flow ◽  
Duty Cycle ◽  
Time Course ◽  
Azygos Vein ◽  
Transdiaphragmatic Pressure ◽  
Parabolic Function ◽  
Internal Mammary ◽  
Anesthetized Dogs ◽  
Phrenic Artery ◽  
Artery Flow

Blood flow (Q) of the diaphragm was measured simultaneously with Doppler probes placed on diaphragmatic veins and an artery and by direct volumetric measurements obtained from cannulation of diaphragmatic blood vessels. The Doppler converting coefficients obtained were 6.27, 7.25, 4.21, and 41.07 ml.min-1.kHz-1 for left phrenic artery flow (Qpha), phrenic vein flow (Qphv), internal mammary vein flow (Qimv), and azygos vein flow (Qazv), respectively. The time course of Qpha, Qphv, Qimv, and Qazv after imposed patterns of diaphragmatic contraction was measured in nine anesthetized dogs. Each pattern consisted of various combinations of transdiaphragmatic pressure (Pdi), frequency of pacing (f), and duty cycle obtained by bilateral phrenic nerve stimulation. The dogs were prepared with chests open and loosely casted abdomens. Qpha, Qphv, Qimv, and Qazv were measured at rest (control, passive diaphragm, mechanical ventilation) and at two submaximal levels of stimulation (30 and 60% of Pdimax). The f was 10 or 30 cycles/min and the duty cycle was 0.25, 0.50, and 0.75. The results show 1) Qpha, Qphv, Qimv, and Qazv reached stable values (equilibration) after 30-36 s of pacing; 2) the steady Qpha, Qphv, and Qimv were linearly related to Pdi, and they were related by a parabolic function to duty cycle, whereas Qazv was not significantly affected by Pdi and increased linearly as a function of the duty cycle; 3) the diaphragmatic blood drainage was approximately 60% through the intercostal veins leading into the azygos trunk, 25% through the phrenic vein, and 15% through the internal mammary vein during pacing of the diaphragm at a duty cycle of 0.50 and 60% Pdimax; and 4) for a given pacing pattern, Qpha and Qphv increased with f, but Qimv and Qazv did not.

Diaphragmatic blood flow in the dog

1986 ◽  
Vol 60 (2) ◽  
pp. 554-561 ◽  
Author(s):  
H. Bark ◽  
S. M. Scharf
Keyword(s):  
Blood Flow ◽  
Duty Cycle ◽  
Stimulus Frequency ◽  
Phase Flow ◽  
Transdiaphragmatic Pressure ◽  
Relaxation Phase ◽  
Duty Cycles ◽  
Tension Time ◽  
Phrenic Artery ◽  
Electromagnetic Flow Probe

In anesthetized mongrel dogs we measured the blood flow in the left phrenic artery (Qdi), using an electromagnetic flow probe, before and during supramaximal phrenic nerve stimulation (pacing). This was done at constant respiratory rate (24/min) but at three different stimulation frequencies at a duty cycle of 0.4 (20, 50, and 100 Hz) and at three different duty cycles at a stimulation frequency of 50 Hz (duty cycle = 0.2, 0.4, and 0.8). Qdi was unchanged during diaphragm contraction until transdiaphragmatic pressure (Pdi) was greater than approximately 11 cmH2O, whereafter it began to decrease, reaching zero at Pdi approximately 20 cmH2O. Thus, when Pdi was greater than 21 cmH2O, all flow occurred during relaxation. Qdi averaged over the entire respiratory cycle (Qt) was less at duty cycle = 0.8 than under the other conditions. This was because of decreasing length of relaxation phase rather than a difference of relaxation phase flow (Qr), which was maximal during all conditions of phrenic stimulation. During pacing-induced fatigue, Qt actually rose slightly as Pdi fell. This was due to an increase in contraction phase flow while Qr remained constant. The relationship between Qt and tension-time index was not unique but varied according to the different combinations of duty cycle and stimulus frequency.

Effects of tension, duty cycle, and arterial pressure on diaphragmatic blood flow in dogs

1989 ◽  
Vol 66 (2) ◽  
pp. 968-976 ◽  
Author(s):  
S. N. Hussain ◽  
C. Roussos ◽  
S. Magder
Keyword(s):  
Blood Flow ◽  
Arterial Pressure ◽  
Duty Cycle ◽  
Phrenic Nerve Stimulation ◽  
Gradual Decline ◽  
Transdiaphragmatic Pressure ◽  
Duty Cycles ◽  
Severe Hypotension ◽  
Internal Mammary ◽  
Pressure Part

We investigated the selective effects of changes in transdiaphragmatic pressure (Pdi) and duty cycle on diaphragmatic blood flow in supine dogs at normal arterial pressure (N), moderate hypotension (MH), and severe hypotension (SH) [mean arterial pressure (Part) of 116, 75, and 50 mmHg, respectively]. The diaphragm was paced at a rate of 12/min by bilateral phrenic nerve stimulation. Left phrenic (Qphr-T) and left internal mammary (Qim-T) arterial flows were measured by electromagnetic flow probes. Changes in Pdi and duty cycle were achieved by changing the stimulation frequencies and the duration of contraction, whereas Part changes were produced by bleeding. With N and at a duty cycle of 0.5, incremental increases in Pdi produced peaks in Qphr-T and Qim-T at 30% maximum diaphragmatic pressure (Pdimax) with a gradual decline at higher Pdi. With MH and SH, blood flow peaked at 10% Pdimax. At any given Pdi, blood flow was lower with MH and SH in comparison to N. The effect of duty cycle was tested at two levels of Pdi. With N and at low Pdi (25% Pdimax), blood flow rose progressively with increases in duty cycle, whereas at moderate Pdi level (50% Pdimax) blood flow peaked at a duty cycle of 0.3, with no increase thereafter. With MH, blood flow at low Pdi rose linearly with increasing duty cycle but to a lesser extent than with N, and at a moderate Pdi flow peaked at a duty cycle of 0.3. With SH, blood flow at low and moderate Pdi was limited at duty cycles greater than 0.3 and 0.1, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Optimal diaphragmatic blood perfusion

1992 ◽  
Vol 72 (1) ◽  
pp. 149-157 ◽  
Author(s):  
F. Hu ◽  
A. Comtois ◽  
A. E. Grassino
Keyword(s):  
Time Course ◽  
Blood Perfusion ◽  
Fatigue Threshold ◽  
Transdiaphragmatic Pressure ◽  
Relaxation Phase ◽  
Time Index ◽  
Duty Cycles ◽  
Parabolic Function ◽  
Tension Time ◽  
Phrenic Artery

The intrabreath time course of phrenic artery blood perfusion (Qpha) was studied in five anesthetized dogs. The diaphragm was paced with submaximal levels of stimulation at various duty cycles (DC) to achieve tension-time index below and above the fatigue threshold (0.03–0.60). Left Qpha was measured via Doppler technique during control (inactive diaphragm) and during two submaximal levels of bilateral phrenic nerve stimulation sustained for 1 min. Measurements were done when Qpha reached steady state in each run. The frequency of pacing of each run was 10/min, and the DC ranged from 0.1 to 0.9 in 0.1 increments. Shortening of costal and crural segments was measured by sonomicrometry. It was found that Qpha during the diaphragmatic contraction phase (QphaC) was a sigmoidal function of DC and was not affected by the levels of transdiaphragmatic pressure (Pdi) explored (34–64% of maximal Pdi). Qpha during the diaphragmatic relaxation phase (QphaR) was a parabolic function of the DC, reaching an optimal value at DC of approximately 0.3 at any given Pdi. QphaR increased significantly with the preceding level of Pdi. QphaT (the sum of QphaC and QphaR) was a parabolic function of DC, reaching peak values at DC of 0.4–0.6 and then decreasing. This function was similar at two levels of Pdi. Post-pacing hyperemia was directly related to tension-time index greater than 0.20.

Autoregulation of diaphragmatic blood flow in dogs

1988 ◽  
Vol 64 (1) ◽  
pp. 329-336 ◽  
Author(s):  
S. N. Hussain ◽  
C. Roussos ◽  
S. Magder
Keyword(s):  
Blood Flow ◽  
Venous Blood ◽  
Muscular Activity ◽  
Work Load ◽  
Quiet Breathing ◽  
Transdiaphragmatic Pressure ◽  
Arterial Blood ◽  
Normal Ranges ◽  
Phrenic Artery ◽  
Spontaneously Breathing

In eight anesthetized spontaneously breathing dogs, we determined whether diaphragmatic blood flow is dependent on arterial blood pressure (Pa) or whether it is autoregulated. We also determined whether diaphragmatic muscular activity affects the degree of autoregulation. We measured blood flow through the left phrenic artery (Qphr) with an electromagnetic flow probe and decreased Pa in steps by controlled hemorrhage. Phrenic venous blood was sampled to allow the calculation of diaphragmatic O2 consumption (VO2phr). Diaphragmatic energy demands were varied by using three inspiratory resistances (R1, R2, and R3), which increased peak transdiaphragmatic pressure two-, three-, and fourfold, respectively. During quiet breathing, Qphr was independent of Pa between Pa of 90 and 120 mmHg (i.e., plateau of pressure-flow relation), but at lower Pa, Qphr was directly related to Pa. During inspiratory loading, the Qphr plateau ended at a higher Pa than with quiet breathing, but within the normal ranges of Pa there still was a plateau. VO2phr at a given work load was constant between Pa of 70 and 120 mmHg, but at Pa of 50-55 mmHg, VO2phr declined with all work loads. We conclude that in spontaneously breathing dogs 1) Qphr is autoregulated over the normal range of blood pressures and 2) VO2phr is maintained over wider ranges of Pa than Qphr.

Restriction of regional blood flow and diaphragmatic contractility

1991 ◽  
Vol 70 (6) ◽  
pp. 2439-2447 ◽  
Author(s):  
A. Comtois ◽  
F. Hu ◽  
A. Grassino
Keyword(s):  
Blood Flow ◽  
Regional Blood Flow ◽  
Abdominal Pressure ◽  
Doppler Flowmetry ◽  
Descending Aorta ◽  
Diaphragmatic Function ◽  
Internal Mammary ◽  
Residual Capacity ◽  
Phrenic Artery ◽  
Crural Diaphragm

We have tested the hypothesis that the diaphragmatic head-to-head arterial anastomosis system should maintain adequate diaphragmatic function even during occlusion of some of its arteries. In six anesthetized open-chest dogs, left phrenic vein blood flow (Qphv) was measured by pulsed Doppler flowmetry. Contractility was measured by sonomicrometry in the left costal and crural diaphragm. The diaphragm was paced for 15 min by continuous bilateral supramaximal phrenic nerve stimulation. In five separate runs the following arteries were occluded at minute 5: 1) left phrenic artery, 2) internal mammary artery (IMA), 3) left phrenic artery and IMA, 4) descending aorta, and 5) descending aorta and IMA. Occlusion was then released at minute 10 of the run. In runs 1-3 there were no changes in contractility in costal or crural diaphragm and no changes in Qphv. However, in runs 4 and 5, Qphv decreased to 55.2 +/- 7.4 and 24.0 +/- 6.5% of control values, respectively. In run 4, percent maximum shortening from functional residual capacity (%LFRC) of the crural diaphragm decreased by 39.1%, while %LFRC of the costal diaphragm increased by 41.4% and abdominal pressure decreased by 47.0%. In run 5, abdominal pressure decreased by 53.5% and %LFRC of the crural and costal diaphragm decreased by 45.5 and 5.8%, respectively. Also relative postocclusion hyperemia was greater in run 5 (64.8%) than in run 4 (40.2%).(ABSTRACT TRUNCATED AT 250 WORDS)

Time course of jejunal blood flow, O2 uptake, and O2 extraction during nutrient absorption

1984 ◽  
Vol 247 (3) ◽  
pp. H395-H402 ◽  
Author(s):  
S. P. Sit ◽  
C. C. Chou
Keyword(s):  
Blood Flow ◽  
Bile Flow ◽  
Time Course ◽  
Glucose Absorption ◽  
Significant Rise ◽  
Nutrient Absorption ◽  
O2 Uptake ◽  
O2 Extraction ◽  
Steady Level ◽  
Anesthetized Dogs

Experiments were performed on anesthetized dogs to determine whether responses of jejunal blood flow, arteriovenous O2 difference, O2 uptake (VO2), and glucose absorption to luminal placement of predigested food or glucose would change with time during 30- and 60-min placement periods and to determine whether bile alters the responses. During the initial 15 min, food, glucose, food plus bile, and glucose plus bile produced a 13, 10, 51, and 30% increase in flow, respectively. During the next 15 min, flow returned to control levels, while arteriovenous O2 difference significantly increased with food or glucose; with glucose plus bile, flow decreased to 28% above control. In the case of food plus bile, flow decreased to 26% above control at 30 min and returned to control 50 min after placement. Despite the fluctuation in flow, the increase in VO2, and glucose absorption stayed at a steady level throughout the entire placement period. Bile significantly enhanced the increases in both flow and VO2 produced by food or glucose, prolonged the hypermia, delayed the significant rise in arteriovenous O2 difference, and had no effect on glucose absorption. In conclusion, the relative contributions of blood flow and O2 extraction to the enhanced VO2 produced by luminal food and glucose change with time, and bile significantly alters the magnitude or time course of changes in the above three variables.

Metabolite changes in the loaded hypoperfused and failing diaphragm

1988 ◽  
Vol 65 (4) ◽  
pp. 1563-1571 ◽  
Author(s):  
D. Lockhat ◽  
C. Roussos ◽  
C. D. Ianuzzo
Keyword(s):  
Skeletal Muscle ◽  
Mechanical Ventilation ◽  
Blood Flow ◽  
Mechanically Ventilated ◽  
Elastic Load ◽  
Mammary Arteries ◽  
Blood Flow Reduction ◽  
Internal Mammary ◽  
Anesthetized Dogs ◽  
Normal Blood Flow

Metabolite changes in the costal diaphragm were determined in anesthetized dogs subjected to a moderate inspiratory elastic load and to reduced blood flow. Diaphragmatic blood flow was reduced by occlusion of the descending aorta and internal mammary arteries. The goal of this study was to demonstrate that the failing diaphragm under these conditions shows biochemical changes similar to that of skeletal muscle fatigue. Selected metabolite concentrations were determined 1) during mechanical ventilation and normal blood flow, 2) during blood flow reduction and inspiratory loading when the ratio of airway pressure to diaphragmatic electromyogram (Paw/Edi) had decreased by 50% (fatigue), and 3) at 1 h after restoration of blood flow and mechanical ventilation (recovery). During fatigue, glycogen, ATP, and phosphocreatine were 30, 50, and 50% of control levels, respectively. Glucose 6-phosphate and lactate were two- and fivefold higher, respectively, than control concentrations. During recovery, all metabolites, except ATP and lactate, returned to control concentrations. These changes were not seen in resting ischemic skeletal muscles or in the diaphragmatic samples of the mechanically ventilated animals with diaphragmatic blood flow limitation. We conclude that when the loaded and hypoperfused diaphragm fails, as indicated by lower than control Paw/Edi, metabolite changes similar to that observed in fatigued skeletal muscle occur.

Patterns of Cerebral Blood Flow and Systemic Hemodynamics During Arithmetic Processing

2008 ◽  
Vol 22 (2) ◽  
pp. 81-90 ◽  
Author(s):  
Natalie Werner ◽  
Neval Kapan ◽  
Gustavo A. Reyes del Paso
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Time Course ◽  
Doppler Sonography ◽  
Transcranial Doppler Sonography ◽  
Systemic Hemodynamics ◽  
Heart Period ◽  
Blood Flow Velocities ◽  
Flow Velocities

The present study explored modulations in cerebral blood flow and systemic hemodynamics during the execution of a mental calculation task in 41 healthy subjects. Time course and lateralization of blood flow velocities in the medial cerebral arteries of both hemispheres were assessed using functional transcranial Doppler sonography. Indices of systemic hemodynamics were obtained using continuous blood pressure recordings. Doppler sonography revealed a biphasic left dominant rise in cerebral blood flow velocities during task execution. Systemic blood pressure increased, whereas heart period, heart period variability, and baroreflex sensitivity declined. Blood pressure and heart period proved predictive of the magnitude of the cerebral blood flow response, particularly of its initial component. Various physiological mechanisms may be assumed to be involved in cardiovascular adjustment to cognitive demands. While specific contributions of the sympathetic and parasympathetic systems may account for the observed pattern of systemic hemodynamics, flow metabolism coupling, fast neurogenic vasodilation, and cerebral autoregulation may be involved in mediating cerebral blood flow modulations. Furthermore, during conditions of high cardiovascular reactivity, systemic hemodynamic changes exert a marked influence on cerebral blood perfusion.

scholarly journals Confocal Blood Flow Videomicroscopy of Thrombus Formation over Human Arteries and Local Targeting of P2X7

2021 ◽  
Vol 22 (8) ◽  
pp. 4066
Author(s):  
Patrizia Marchese ◽  
Maria Lombardi ◽  
Maria Elena Mantione ◽  
Domenico Baccellieri ◽  
David Ferrara ◽  
...  
Keyword(s):  
Blood Flow ◽  
Vascular Function ◽  
Collagen Type ◽  
Thrombus Formation ◽  
Collagen Type I ◽  
Type I ◽  
Prevention Therapy ◽  
Healthy Donors ◽  
Internal Mammary ◽  
Human Arteries

Atherothrombosis exposes vascular components to blood. Currently, new antithrombotic therapies are emerging. Herein we investigated thrombogenesis of human arteries with/without atherosclerosis, and the interaction of coagulation and vascular components, we and explored the anti-thrombogenic efficacy of blockade of the P2X purinoceptor 7 (P2X7). A confocal blood flow videomicroscopy system was performed on cryosections of internal mammary artery (IMA) or carotid plaque (CPL) determining/localizing platelets and fibrin. Blood from healthy donors elicited thrombi over arterial layers. Confocal microscopy associated thrombus with tissue presence of collagen type I, laminin, fibrin(ogen) and tissue factor (TF). The addition of antibodies blocking TF (aTF) or factor XI (aFXI) to blood significantly reduced fibrin deposition, variable platelet aggregation and aTF + aFXI almost abolished thrombus formation, showing synergy between coagulation pathways. A scarce effect of aTF over sub-endothelial regions, more abundant in tissue TF and bundles of laminin and collagen type I than deep intima, may suggest tissue thrombogenicity as molecular structure-related. Consistently with TF-related vascular function and expression of P2X7, the sections from CPL but not IMA tissue cultures pre-treated with the P2X7 antagonist A740003 demonstrated poor thrombogenesis in flow experiments. These data hint to local targeting studies on P2X7 modulation for atherothrombosis prevention/therapy.

scholarly journals Use of quantitative cardiovascular magnetic resonance myocardial perfusion mapping for characterization of ischemia in patients with left internal mammary coronary artery bypass grafts

2021 ◽  
Vol 23 (1) ◽  
Author(s):  
Andreas Seraphim ◽  
Kristopher D. Knott ◽  
Anne-Marie Beirne ◽  
Joao B. Augusto ◽  
Katia Menacho ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cardiovascular Magnetic Resonance ◽  
Coronary Artery ◽  
Magnetic Resonance ◽  
Myocardial Perfusion ◽  
Myocardial Blood Flow ◽  
Coronary Artery Bypass ◽  
Artery Bypass ◽  
Internal Mammary ◽  
Perfusion Defects

Abstract Background Quantitative myocardial perfusion mapping using cardiovascular magnetic resonance (CMR) is validated for myocardial blood flow (MBF) estimation in native vessel coronary artery disease (CAD). Following coronary artery bypass graft (CABG) surgery, perfusion defects are often detected in territories supplied by the left internal mammary artery (LIMA) graft, but their interpretation and subsequent clinical management is variable. Methods We assessed myocardial perfusion using quantitative CMR perfusion mapping in 38 patients with prior CABG surgery, all with angiographically-proven patent LIMA grafts to the left anterior descending coronary artery (LAD) and no prior infarction in the LAD territory. Factors potentially determining MBF in the LIMA–LAD myocardial territory, including the impact of delayed contrast arrival through the LIMA graft were evaluated. Results Perfusion defects were reported on blinded visual analysis in the LIMA–LAD territory in 27 (71%) cases, despite LIMA graft patency and no LAD infarction. Native LAD chronic total occlusion (CTO) was a strong independent predictor of stress MBF (B = − 0.41, p = 0.014) and myocardial perfusion reserve (MPR) (B = − 0.56, p = 0.005), and was associated with reduced stress MBF in the basal (1.47 vs 2.07 ml/g/min; p = 0.002) but not the apical myocardial segments (1.52 vs 1.87 ml/g/min; p = 0.057). Extending the maximum arterial time delay incorporated in the quantitative perfusion algorithm, resulted only in a small increase (3.4%) of estimated stress MBF. Conclusions Perfusion defects are frequently detected in LIMA–LAD subtended territories post CABG despite LIMA patency. Although delayed contrast arrival through LIMA grafts causes a small underestimation of MBF, perfusion defects are likely to reflect true reductions in myocardial blood flow, largely due to proximal native LAD disease.

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