Jugular venous pooling during lowering of the head affects blood pressure of the anesthetized giraffe

2009 ◽  
Vol 297 (4) ◽  
pp. R1058-R1065 ◽  
Author(s):  
E. Brøndum ◽  
J. M. Hasenkam ◽  
N. H. Secher ◽  
M. F. Bertelsen ◽  
C. Grøndahl ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Arterial Pressure ◽  
Venous Pressure ◽  
Upright Position ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Jugular Veins ◽  
Cross Sectional ◽  
Spontaneously Breathing

How blood flow and pressure to the giraffe's brain are regulated when drinking remains debated. We measured simultaneous blood flow, pressure, and cross-sectional area in the carotid artery and jugular vein of five anesthetized and spontaneously breathing giraffes. The giraffes were suspended in the upright position so that we could lower the head. In the upright position, mean arterial pressure (MAP) was 193 ± 11 mmHg (mean ± SE), carotid flow was 0.7 ± 0.2 l/min, and carotid cross-sectional area was 0.85 ± 0.04 cm2. Central venous pressure (CVP) was 4 ± 2 mmHg, jugular flow was 0.7 ± 0.2 l/min, and jugular cross-sectional area was 0.14 ± 0.04 cm2 ( n = 4). Carotid arterial and jugular venous pressures at head level were 118 ± 9 and −7 ± 4 mmHg, respectively. When the head was lowered, MAP decreased to 131 ± 13 mmHg, while carotid cross-sectional area and flow remained unchanged. Cardiac output was reduced by 30%, CVP decreased to −1 ± 2 mmHg ( P < 0.01), and jugular flow ceased as the jugular cross-sectional area increased to 3.2 ± 0.6 cm2 ( P < 0.01), corresponding to accumulation of ∼1.2 l of blood in the veins. When the head was raised, the jugular veins collapsed and blood was returned to the central circulation, and CVP and cardiac output were restored. The results demonstrate that in the upright-positioned, anesthetized giraffe cerebral blood flow is governed by arterial pressure without support of a siphon mechanism and that when the head is lowered, blood accumulates in the vein, affecting MAP.

scholarly journals Sequential alterations in the diameters of capillaries in rabbit skeletal muscle following deep transverse friction - a morphometric study

2005 ◽  
Vol 61 (2) ◽  
Author(s):  
M. A. Gregory ◽  
M. N. Deane ◽  
M. Marsh
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Muscle Blood Flow ◽  
Biceps Femoris ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Biceps Femoris Muscle ◽  
Beneficial Effects ◽  
The Cross

Objective: The precise mechanisms by which massage promotes repair in injured soft tissue are unknown. Various authorshave attributed the beneficial effects of massage to vasodilation and increased skin and muscle blood flow. The aim of this study was to determine whether deep transverse friction massage (DTF) causes capillary vasodilation in untraumatised skeletal muscle. Setting: Academic institution.Interventions: Twelve New Zealand white rabbits were anaesthetised and the left biceps femoris muscle received 10 minutes of DTF. Following treatment, wedge biopsies were taken from the musclewithin 10 minutes of treatment (R1 - 4), 24 hours (R5 - 8) and 6 days(R9 - 12) after treatment. To serve as controls, similar biopsies weretaken from the right biceps femoris of animals. The samples were fixed, dehydrated and embedded in epoxy resin.Transverse sections (1µm) of muscle were cut, stained with 1% aqueous alkaline toluidine blue and examined with a light microscope using a 40X objective. Images containing capillaries were captured using an image analyser with SIS software and the cross sectional diameters of at least 60 capillaries were measured from each specimen. Main Outcome Measures: Changes in capillary diameter. Results: The mean capillary diameters in control muscle averaged 4.76 µm. DTF caused a significant immediate increase of 17.3% in cross sectional area (p<0.001), which was not significantly increased by 10.0% after 24 hours (p>0.05). Six days after treatment the cross-sectional area of the treated muscle was 7.6% smaller than the controls. Conclusions: This confirms the contention that DTF stimulates muscle blood flow immediately after treatment and this may account for its beneficial effects in certain conditions. 

A computed method for noninvasive MRI assessment of pulmonary arterial hypertension

2004 ◽  
Vol 96 (2) ◽  
pp. 463-468 ◽  
Author(s):  
Eric Laffon ◽  
Christophe Vallet ◽  
Virginie Bernard ◽  
Michel Montaudon ◽  
Dominique Ducassou ◽  
...  
Keyword(s):  
Arterial Pressure ◽  
Pulmonary Arterial Pressure ◽  
Cross Sectional Area ◽  
Physical Parameters ◽  
Sectional Area ◽  
Biophysical Parameters ◽  
Cross Sectional ◽  
Mean Pulmonary Arterial Pressure ◽  
Pulmonary Arterial ◽  
The Mean

The present method enables the noninvasive assessment of mean pulmonary arterial pressure from magnetic resonance phase mapping by computing both physical and biophysical parameters. The physical parameters include the mean blood flow velocity over the cross-sectional area of the main pulmonary artery (MPA) at the systolic peak and the maximal systolic MPA cross-sectional area value, whereas the biophysical parameters are related to each patient, such as height, weight, and heart rate. These parameters have been measured in a series of 31 patients undergoing right-side heart catheterization, and the computed mean pulmonary arterial pressure value (PpaComp) has been compared with the mean pressure value obtained from catheterization (PpaCat) in each patient. A significant correlation was found that did not differ from the identity line PpaComp = PpaCat ( r = 0.92). The mean and maximal absolute differences between PpaComp and PpaCat were 5.4 and 11.9 mmHg, respectively. The method was also applied to compute the MPA systolic and diastolic pressures in the same patient series. We conclude that this computed method, which combines physical (whoever the patient) and biophysical parameters (related to each patient), improves the accuracy of MRI to noninvasively estimate pulmonary arterial pressures.

scholarly journals Changes in lower extremity blood flow during advancing phases of pregnancy and the effects of special footwear

2017 ◽  
Vol 16 (3) ◽  
pp. 214-219 ◽  
Author(s):  
Marta Gimunová ◽  
Martin Zvonař ◽  
Kateřina Kolářová ◽  
Zdeněk Janík ◽  
Ondřej Mikeska ◽  
...  
Keyword(s):  
Blood Flow ◽  
Venous Blood ◽  
Cross Sectional Area ◽  
Popliteal Vein ◽  
Control Group ◽  
Venous Disease ◽  
Venous Blood Flow ◽  
Sectional Area ◽  
Cross Sectional ◽  
Experimental Group

Abstract Background During pregnancy, a number of changes affecting venous blood flow occur in the circulatory system, such as reduced vein wall tension or increased exposure to collagen fibers. These factors may cause blood stagnation, swelling of the legs, or endothelial damage and consequently lead to development of venous disease. Objectives The aim of this study is to evaluate the effect of special footwear designed to improve blood circulation in the feet on venous blood flow changes observed during advancing phases of pregnancy. Methods Thirty healthy pregnant women participated in this study at 25, 30, and 35 weeks of gestation. Participants were allocated at random to an experimental group (n = 15) which was provided with the special footwear, or a control group (n = 15). At each data collection session, Doppler measurements of peak systolic blood flow velocity and cross-sectional area of the right popliteal vein were performed using a MySonoU6 ultrasound machine with a linear transducer (Samsung Medison). The differences were compared using Cohen’s d test to calculate effect size. Results With advancing phases of pregnancy, peak systolic velocity in the popliteal vein decreased significantly in the control group, whereas it increased significantly in the experimental group. No significant change in cross-sectional area was observed in any of the groups. Conclusions Findings in the experimental group demonstrated that wearing the footwear tested may prevent venous blood velocity from reducing during advanced phases of pregnancy. Nevertheless, there is a need for further investigation of the beneficial effect on venous flow of the footwear tested and its application.

scholarly journals Venous compliance and clinical implications

2018 ◽  
Vol 7 (2) ◽  
Author(s):  
Paolo Zamboni ◽  
Valentina Tavoni ◽  
Francesco Sisini ◽  
Massimo Pedriali ◽  
Erika Rimondi ◽  
...  
Keyword(s):  
Venous Pressure ◽  
Vena Cava ◽  
Cross Sectional Area ◽  
Venous System ◽  
Clinical Implications ◽  
Sectional Area ◽  
Venous Compliance ◽  
Cross Sectional ◽  
The Cross ◽  
Deformable System

Compliance is a characteristic of every deformable system. Compliance is very clear concept in physics and mechanics but in clinics, perhaps, is not the same. However, in veins compliance fits perfectly with the function of drainage of the venous system. Volumetric increase (dV) of the content is correlated with pressure increase (dP) inside the vein according to the equation C’= dV/dP. In humans 75% of the blood is located in the venous system, primarily because the molecular components of a vein media layer is significantly more compliant to that of arteries. This property is fundamental to understanding the change in blood volume in response to a change in posture. Measurements of venous compliance in clinical practice can be done by the means of ultrasound, as well as with the plethysmography. Ultrasound methods assimilate the cross sectional area to the volume of the vein, because it reflects the blood content. Changes in cross sectional area can be reliably measured in response to a change in posture, while pressure can be derived from the hydrostatic pressure changes. Venous compliance is of paramount importance also in pulsatile veins such as the inferior or superior vena cava and the jugular veins, where high resolution ultrasound may accurately derive the cross sectional area. Clinical implications of the mechanical properties of the venous wall are extensively discussed, including the need of dedicated venous stenting, which takes into account venous compliance as the main parameter of the venous function. In addition, venous compliance is the interpretative key for a better understanding of plethysmography curves, as well as of varicose veins and of their return to normal cross sectional area following ambulatory venous pressure reduction.

Alterations of mature arterioles associated with chronically reduced blood flow

1993 ◽  
Vol 264 (1) ◽  
pp. H40-H44 ◽  
Author(s):  
D. H. Wang ◽  
R. L. Prewitt
Keyword(s):  
Blood Flow ◽  
Vascular Wall ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Adaptive Responses ◽  
Total Blood ◽  
Cross Sectional ◽  
Old Rats ◽  
Total Blood Flow ◽  
Autoregulatory Mechanism

Adaptive responses of mature arterioles were examined after a 38% reduction in total blood flow to the cremaster muscle produced by unilateral orchidectomy in 12-wk-old rats. Four weeks later, the muscle was smaller than the contralateral cremaster, which did not increase in size during this period. Measured by closed-circuit television microscopy, the internal diameters of first- through fourth-order arterioles (1A-4A) were smaller, but wall cross-sectional area was reduced only in 3As. The smaller diameter of the 1A in the orchidectomy muscle resulted in unchanged wall shear rate. As determined from the perfusion-fixed, microfilled cremaster muscles, the total length of the arcading arterioles and the number of 3As were not statistically different, but the total number of 4As was significantly reduced on the orchidectomy side. Therefore, chronic load reduction in a mature muscle resulted in reduced blood flow, decreased number of 4As, and smaller arteriolar internal diameters in the absence of net changes in vascular wall cross-sectional area. A local autoregulatory mechanism related to flow-induced shear stress is suggested as the mechanism mediating the changes.

Atrial natriuretic peptide increases resistance to venous return in rats

1987 ◽  
Vol 252 (5) ◽  
pp. H894-H899 ◽  
Author(s):  
Y. W. Chien ◽  
E. D. Frohlich ◽  
N. C. Trippodo
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Arterial Pressure ◽  
Atrial Natriuretic Peptide ◽  
Natriuretic Peptide ◽  
Total Peripheral Resistance ◽  
Venous Return ◽  
Venous Pressure ◽  
Peripheral Resistance ◽  
Atrial Natriuretic

To examine mechanisms by which administration of atrial natriuretic peptide (ANP) decreases venous return, we compared the hemodynamic effects of ANP (0.5 microgram X min-1 X kg-1), furosemide (FU, 10 micrograms X min-1 X kg-1), and hexamethonium (HEX, 0.5 mg X min-1 X kg-1) with those of vehicle (VE) in anesthetized rats. Compared with VE, ANP reduced mean arterial pressure (106 +/- 4 vs. 92 +/- 3 mmHg; P less than 0.05), central venous pressure (0.3 +/- 0.3 vs. -0.7 +/- 0.2 mmHg; P less than 0.01), and cardiac index (215 +/- 12 vs. 174 +/- 10 ml X min-1 X kg-1; P less than 0.05) and increased calculated resistance to venous return (32 +/- 3 vs. 42 +/- 2 mmHg X ml-1 X min X g; P less than 0.01). Mean circulatory filling pressure, distribution of blood flow between splanchnic organs and skeletal muscles, and total peripheral resistance remained unchanged. FU increased urine output similar to that of ANP, yet produced no hemodynamic changes, dissociating diuresis, and decreased cardiac output. HEX lowered arterial pressure through a reduction in total peripheral resistance without altering cardiac output or resistance to venous return. The results confirm previous findings that ANP decreases cardiac output through a reduction in venous return and suggest that this results partly from increased resistance to venous return and not from venodilation or redistribution of blood flow.

Effect of position and lung volume on upper airway geometry

1987 ◽  
Vol 63 (1) ◽  
pp. 375-380 ◽  
Author(s):  
J. M. Fouke ◽  
K. P. Strohl
Keyword(s):  
Lung Volume ◽  
Supine Position ◽  
Upper Airway ◽  
Upright Position ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Position Change ◽  
Cross Sectional ◽  
Acoustic Reflection ◽  
Residual Capacity

The occurrence of upper airway obstruction during sleep and with anesthesia suggests the possibility that upper airway size might be compromised by the gravitational effects of the supine position. We used an acoustic reflection technique to image airway geometry and made 180 estimates of effective cross-sectional area as a function of distance along the airway in 10 healthy volunteers while they were supine and also while they were seated upright. We calculated z-scores along the airway and found that pharyngeal cross-sectional area was smaller in the supine than in the upright position in 9 of the 10 subjects. For all subjects, pharyngeal cross-sectional area was 23 +/- 8% smaller in the supine than in the upright position (P less than or equal to 0.05), whereas glottic and tracheal areas were not significantly altered. Because changing from the upright to the supine position causes a decrease in functional residual capacity (FRC), six of these subjects were placed in an Emerson cuirass, which was evacuated producing a positive transrespiratory pressure so as to restore end-expiratory lung volume to that seen before the position change. In the supine posture an increase in end-expiratory lung volume did not change the cross-sectional area at any point along the airway. We conclude that pharyngeal cross-sectional area decreases as a result of a change from the upright to the supine position and that the mechanism of this change is independent of the change in FRC.

Peripharyngeal tissue deformation and stress distributions in response to caudal tracheal displacement: pivotal influence of the hyoid bone?

2014 ◽  
Vol 116 (7) ◽  
pp. 746-756 ◽  
Author(s):  
Jason Amatoury ◽  
Kristina Kairaitis ◽  
John R. Wheatley ◽  
Lynne E. Bilston ◽  
Terence C. Amis
Keyword(s):  
Hyoid Bone ◽  
Upper Airway ◽  
Cross Sectional Area ◽  
Tissue Deformation ◽  
Stress Distributions ◽  
Sectional Area ◽  
Tissue Pressure ◽  
Cross Sectional ◽  
Spontaneously Breathing ◽  
Model Slope

Caudal tracheal displacement (TD) leads to improvements in upper airway (UA) function and decreased collapsibility. To better understand the mechanisms underlying these changes, we examined effects of TD on peripharyngeal tissue stress distributions [i.e., extraluminal tissue pressure (ETP)], deformation of its topographical surface (UA lumen geometry), and hyoid bone position. We studied 13 supine, anesthetized, tracheostomized, spontaneously breathing, adult male New Zealand white rabbits. Graded TD was applied to the cranial tracheal segment from 0 to ∼10 mm. ETP was measured at six locations distributed around/along the length of the UA, covering three regions: tongue, hyoid, and epiglottis. Axial images of the UA (nasal choanae to glottis) were acquired with computed tomography and used to measure lumen geometry (UA length; regional cross-sectional area) and hyoid bone displacement. TD resulted in nonuniform decreases in ETP (generally greatest at tongue region), ranging from −0.07 (−0.11 to −0.03) [linear mixed-effects model slope (95% confidence interval)] to −0.27 (−0.31 to −0.23) cmH2O/mm TD, across all sites. UA length increased by 1.6 (1.5–1.8)%/mm, accompanied by nonuniform increases in cross-sectional area (greatest at hyoid region) ranging from 2.8 (1.7–3.9) to 4.9 (3.8–6.0)%/mm. The hyoid bone was displaced caudally by 0.22 (0.18–0.25) mm/mm TD. In summary, TD imposes a load on the UA that results in heterogeneous changes in peripharyngeal tissue stress distributions and resultant lumen geometry. The hyoid bone may play a pivotal role in redistributing applied caudal tracheal loads, thus modifying tissue deformation distributions and determining resultant UA geometry outcomes.

Valsalva's maneuver revisited: a quantitative method yielding insights into human autonomic control

1996 ◽  
Vol 271 (3) ◽  
pp. H1240-H1249 ◽  
Author(s):  
M. L. Smith ◽  
L. A. Beightol ◽  
J. M. Fritsch-Yelle ◽  
K. A. Ellenbogen ◽  
T. R. Porter ◽  
...  
Keyword(s):  
Arterial Pressure ◽  
Cross Sectional Area ◽  
Neuronal Firing ◽  
Right Atrial ◽  
Sectional Area ◽  
Nerve Activity ◽  
Cross Sectional ◽  
Muscle Nerve ◽  
Peripheral Arterial ◽  
Valsalva’S Maneuver

Seventeen healthy supine subjects performed graded Valsalva maneuvers. In four subjects, transesophageal echographic aortic cross-sectional areas decreased during and increased after straining. During the first seconds of straining, when aortic cross-sectional area was declining and peripheral arterial pressure was rising, peroneal sympathetic muscle neurons were nearly silent. Then, as aortic cross-sectional area and peripheral pressure both declined, sympathetic muscle nerve activity increased, in proportion to the intensity of straining. Poststraining arterial pressure elevations were proportional to preceding increases of sympathetic activity. Sympathetic inhibition after straining persisted much longer than arterial and right atrial pressure elevations. Similarly, R-R intervals changed in parallel with peripheral arterial pressure, until approximately 45 s after the onset of straining, when R-R intervals were greater and arterial pressures were smaller than prestraining levels. Our conclusions are as follows: opposing changes of carotid and aortic baroreceptor inputs reduce sympathetic muscle and increase vagal cardiac motor neuronal firing; parallel changes of barorsensory inputs provoke reciprocal changes of sympathetic and direct changes of vagal firing; and pressure transients lasting only seconds reset arterial pressure-sympathetic and -vagal response relations.

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