Lumped Parameter Thermal Model for the Study of Vascular Reactivity in the Fingertip

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
O. Ley ◽  
C. Deshpande ◽  
B. Prapamcham ◽  
M. Naghavi
Keyword(s):  
Heat Flux ◽  
Blood Flow ◽  
Thermal Model ◽  
Vascular Reactivity ◽  
Arterial Occlusion ◽  
Blood Perfusion ◽  
Cost Effective ◽  
Venous Occlusion ◽  
Cardiovascular Complications ◽  
Tissue Temperature

Vascular reactivity (VR) denotes changes in volumetric blood flow in response to arterial occlusion. Current techniques to study VR rely on monitoring blood flow parameters and serve to predict the risk of future cardiovascular complications. Because tissue temperature is directly impacted by blood flow, a simplified thermal model was developed to study the alterations in fingertip temperature during arterial occlusion and subsequent reperfusion (hyperemia). This work shows that fingertip temperature variation during VR test can be used as a cost-effective alternative to blood perfusion monitoring. The model developed introduces a function to approximate the temporal alterations in blood volume during VR tests. Parametric studies are performed to analyze the effects of blood perfusion alterations, as well as any environmental contribution to fingertip temperature. Experiments were performed on eight healthy volunteers to study the thermal effect of 3min of arterial occlusion and subsequent reperfusion (hyperemia). Fingertip temperature and heat flux were measured at the occluded and control fingers, and the finger blood perfusion was determined using venous occlusion plethysmography (VOP). The model was able to phenomenologically reproduce the experimental measurements. Significant variability was observed in the starting fingertip temperature and heat flux measurements among subjects. Difficulty in achieving thermal equilibration was observed, which indicates the important effect of initial temperature and thermal trend (i.e., vasoconstriction, vasodilatation, and oscillations).

Peak calf blood flow estimates are higher with Dohn than with Whitney plethysmograph

1996 ◽  
Vol 81 (3) ◽  
pp. 1418-1422 ◽  
Author(s):  
D. N. Proctor ◽  
J. R. Halliwill ◽  
P. H. Shen ◽  
N. E. Vlahakis ◽  
M. J. Joyner
Keyword(s):  
Blood Flow ◽  
Reactive Hyperemia ◽  
Arterial Occlusion ◽  
Venous Occlusion ◽  
Calf Blood Flow ◽  
Absolute Flow ◽  
Wide Range ◽  
Before And After ◽  
The Mean ◽  
Highly Correlated

Estimates of calf blood flow with venous occlusion plethysmography vary widely between studies, perhaps due to the use of different plethysmographs. Consequently, we compared calf blood flow estimates at rest and during reactive hyperemia in eight healthy subjects (four men and four women) with two commonly used plethysmographs: the mercury-in-silastic (Whitney) strain gauge and Dohn air-filled cuff. To minimize technical variability, flow estimates were compared with a Whitney gauge and a Dohn cuff on opposite calves before and after 10 min of bilateral femoral arterial occlusion. To account for any differences between limbs, a second trial was conducted in which the plethysmographs were switched. Resting flows did not differ between the plethysmographs (P = 0.096), but a trend toward lower values with the Whitney was apparent. Peak flows averaged 37% lower with the Whitney (27.8 +/- 2.8 ml.dl-1.min-1) than with the Dohn plethysmograph (44.4 +/- 2.8 ml.dl-1.min-1; P < 0.05). Peak flow expressed as a multiple above baseline was also lower with the Whitney (10-fold) than with the Dohn plethysmograph (14.5-fold; P = 0.02). Across all flows at rest and during reactive hyperemia, estimates were highly correlated between the plethysmographs in all subjects (r2 = 0.96-0.99). However, the mean slope for the Whitney-Dohn relationship was only 60 +/- 2%, indicating that over a wide range of flows the Whitney gauge estimate was 40% lower than that for the Dohn cuff. These results demonstrate that the same qualitative results can be obtained with either plethysmograph but that absolute flow values will generally be lower with Whitney gauges.

Endothelin-1 and pancreatic islet vasculature: studies in vivo and on isolated, vascularly perfused pancreatic islets

2007 ◽  
Vol 292 (6) ◽  
pp. E1616-E1623 ◽  
Author(s):  
En Yin Lai ◽  
A. Erik G. Persson ◽  
Birgitta Bodin ◽  
Örjan Källskog ◽  
Arne Andersson ◽  
...  
Keyword(s):  
Blood Flow ◽  
Pancreatic Islet ◽  
Vascular Reactivity ◽  
Blood Perfusion ◽  
Receptor Subtype ◽  
Endothelin 1 ◽  
Islet Blood Flow ◽  
Endothelin B

Endothelin-1 (ET-1) is a potent endothelium-derived vasoconstrictor, which also stimulates insulin release. The aim of the present study was to evaluate whether exogenously administered ET-1 affected pancreatic islet blood flow in vivo in rats and the islet arteriolar reactivity in vitro in mice. Furthermore, we aimed to determine the ET-receptor subtype that was involved in such responses. When applying a microsphere technique for measurements of islet blood perfusion in vivo, we found that ET-1 (5 nmol/kg) consistently and markedly decreased total pancreatic and especially islet blood flow, despite having only minor effects on blood pressure. Neither endothelin A (ETA) receptor (BQ-123) nor endothelin-B (ETB) receptor (BQ-788) antagonists, alone or in combination, could prevent this reduction in blood flow. To avoid confounding interactions in vivo, we also examined the arteriolar vascular reactivity in isolated, perfused mouse islets. In the latter preparation, we demonstrated a dose-dependent constriction in response to ET-1. Administration of BQ-123 prevented this, whereas BQ-788 induced a right shift in the response. In conclusion, the pancreatic islet vasculature is highly sensitive to exogenous ET-1, which mediates its effect mainly through ETA receptors.

Effect of active muscle mass during ischemic exercise on peak lower leg vascular conductance

2005 ◽  
Vol 98 (3) ◽  
pp. 765-771 ◽  
Author(s):  
Aaron J. Polichnowski ◽  
Ellen K. Heyer ◽  
Alexander V. Ng
Keyword(s):  
Blood Flow ◽  
Muscle Mass ◽  
Plantar Flexion ◽  
Arterial Occlusion ◽  
Venous Occlusion ◽  
Lower Leg ◽  
Isokinetic Dynamometer ◽  
Active Muscle ◽  
Vascular Conductance ◽  
The Right

Uncertainty exists as to whether a period of passive arterial occlusion (PAO) or ischemic exercise (IE) results in peak lower leg vascular conductance (LVC). This uncertainty is due to the different body positions, active muscle mass, and occlusion times used for PAO or IE. The purpose of this study was to examine whether 10 min of PAO elicits a similar LVC compared with ischemic dorsiflexion (IDF), ischemic plantar flexion (IPF), and ischemic plantar-dorsiflexion (IPDF). Ten subjects (5 women, 27 ± 9 yr, 68 ± 3 kg) were studied on 3 days over 1 wk in a semireclined position with the right foot attached to an isokinetic dynamometer. Mean arterial pressure (Finapres) and lower leg blood flow (LBF, venous occlusion plethysmography) were measured at rest and after PAO and IE. PAO was administered randomly on 1 of the 3 days and before IE. IE protocols consisted of maximal isokinetic dorsiflexion and/or plantar flexion at 120 and 60°/s, respectively. In a second experiment, an additional eight subjects (4 women, 29 ± 12 yr, 77 ± 12 kg) were studied to examine the effect of isokinetic speed during IDF on peak LBF and LVC. Peak LVC (ml·min−1·100 ml−1·mmHg−1) was similar among IPF (0.590 ± 0.16), IPDF (0.532 ± 0.17), and PAO (0.511 ± 0.18), and significantly lower after IDF (0.334 ± 0.15). No differences in peak LBF and LVC were observed after IDF using different isokinetic speeds. We conclude that 10 min of PAO, IPF, and IPDF performed in a similar posture are adequate stimuli to elicit peak LVC.

scholarly journals Cardiovascular and Autonomic Responses after a Single Bout of Resistance Exercise in Men with Untreated Stage 2 Hypertension

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Marcus Vinicius Machado ◽  
Thais de Paola Chequer Barbosa ◽  
Thais Camasmine Chrispino ◽  
Fabricia Junqueira das Neves ◽  
Gabriel Dias Rodrigues ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Resistance Exercise ◽  
Vascular Reactivity ◽  
Forearm Blood Flow ◽  
Area Under The Curve ◽  
Venous Occlusion ◽  
Antihypertensive Medications ◽  
Single Bout

The aim of this paper is to assess the integrated responses of ambulatory blood pressure (BP), cardiac autonomic modulation, spontaneous baroreflex sensitivity (BRS), and vascular reactivity after a single bout of resistance exercise (RE) in men with stage 2 hypertension who have never been treated before. Ten hypertensive men were subjected to a RE session of three sets of 20 repetitions and an intensity of 40% of the 1-repetition maximum (RM) test in seven different exercises. For the control (CTR) session, the volunteers were positioned on the exercise machines but did not perform any exercise. Forearm blood flow was measured by venous occlusion plethysmography. We also analyzed the heart rate variability (HRV), ambulatory BP, blood pressure variability (BPV), and BRS. All measurements were performed at different timepoints: baseline, 20 min, 80 min, and 24 h after both RE and CTR sessions. There were no differences in ambulatory BP over the 24 h between the RE and CTR sessions. However, the area under the curve of diastolic BP decreased after the RE session. Heart rate (HR) and cardiac output increased for up to 80 and 20 min after RE, respectively. Similarly, forearm blood flow, conductance, and vascular reactivity increased 20 min after RE ( p < 0.05 ). In contrast, HRV and BRS decreased immediately after exercise and remained lower for 20 min after RE. We conclude that a single bout of RE induced an increase in vascular reactivity and reduced the pressure load by attenuating AUC of DBP in hypertensive individuals who had never been treated with antihypertensive medications.

Intrinsic control of colonic blood flow and oxygenation

1980 ◽  
Vol 238 (6) ◽  
pp. G478-G484
Author(s):  
P. R. Kvietys ◽  
T. Miller ◽  
D. N. Granger
Keyword(s):  
Blood Flow ◽  
Vascular Resistance ◽  
Perfusion Pressure ◽  
Reactive Hyperemia ◽  
Venous Pressure ◽  
Arterial Occlusion ◽  
Venous Occlusion ◽  
Colonic Blood Flow ◽  
O2 Extraction ◽  
O2 Delivery

In a denervated autoperfused dog colon preparation, arterial perfusion pressure, venous outflow pressure, blood flow, and arteriovenous O2 difference were measured during graded arterial pressure alterations, arterial occlusion, venous pressure elevation, venous occlusion, and local intra-arterial infusion of adenosine. As perfusion pressure was reduced from 100 to 30 mmHg, colonic blood flow decreased and arteriovenous O2 difference increased. Although blood flow was not autoregulated O2 delivery was maintained within 10% of control between 70 to 100 mmHg and then decreased with further reduction in perfusion pressure. Arterial occlusion (15, 30, and 60 s) resulted in a postocclusion reactive hyperemia; the magnitude of the hyperemia was directly related to the duration of occlusion. Venous occlusion resulted in a postocclusion reactive hypoemia. Elevation of venous pressure from 0 to 20 mmHg increased vascular resistance, O2 extraction, and the capillary filtration coefficient, but decreased O2 delivery. Infusion of adenosine decreased vascular resistance and O2 extraction, but increased O2 delivery. These data suggest that both metabolic and myogenic mechanisms are involved in the control of colonic blood flow and oxygenation.

scholarly journals Hyperglycemia Increases Muscle Blood Flow and Alters Endothelial Function in Adolescents with Type 1 Diabetes

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Amanda S. Dye ◽  
Hong Huang ◽  
John A. Bauer ◽  
Robert P. Hoffman
Keyword(s):  
Blood Flow ◽  
Type 1 Diabetes ◽  
Endothelial Function ◽  
Vascular Function ◽  
Microvascular Complications ◽  
Muscle Blood Flow ◽  
Arterial Occlusion ◽  
Venous Occlusion ◽  
Before And After

Alterations of blood flow and endothelial function precede development of complications in type 1 diabetes. The effects of hyperglycemia on vascular function in early type 1 diabetes are poorly understood. To investigate the effect of hyperglycemia on forearm vascular resistance (FVR) and endothelial function in adolescents with type 1 diabetes, FVR was measured before and after 5 minutes of upper arm arterial occlusion using venous occlusion plethysmography in (1) fasted state, (2) euglycemic state (~90 mg/dL; using 40 mU/m2/min insulin infusion), and (3) hyperglycemic state (~200 mg/dL) in 11 adolescents with type 1 diabetes. Endothelial function was assessed by the change in FVR following occlusion. Seven subjects returned for a repeat study with hyperglycemia replaced by euglycemia. Preocclusion FVR decreased from euglycemia to hyperglycemia (P=0.003). Postocclusion fall in FVR during hyperglycemia was less than during euglycemia (P=0.002). These findings were not reproduced when hyperglycemia was replaced with a second euglycemia. These results demonstrate that acute hyperglycemia causes vasodilation and alters endothelial function in adolescents with type 1 diabetes. In addition they have implications for future studies of endothelial function in type 1 diabetes and provide insight into the etiology of macrovascular and microvascular complications of type 1 diabetes.

Enhanced maximal metabolic vasodilatation in the dominant forearms of tennis players

1986 ◽  
Vol 61 (2) ◽  
pp. 673-678 ◽  
Author(s):  
L. I. Sinoway ◽  
T. I. Musch ◽  
J. R. Minotti ◽  
R. Zelis
Keyword(s):  
Blood Flow ◽  
Forearm Blood Flow ◽  
Arterial Occlusion ◽  
Study Groups ◽  
Venous Occlusion ◽  
Control Group ◽  
Tennis Players ◽  
Blood Flows ◽  
Metabolic Vasodilation ◽  
Adaptation To Exercise

In an effort to evaluate potential peripheral adaptations to training, maximal metabolic vasodilation was studied in the dominant and nondominant forearms of six tennis players and six control subjects. Maximal metabolic vasodilation was defined as the peak forearm blood flow measured after release of arterial occlusion, the reactive hyperemic blood flow (RHBF). Two ischemic stimuli were employed in each subject: 5 min of arterial occlusion (RHBF5) and 5 min of arterial occlusion coupled with 1 min of ischemic exercise (RHBF5ex). RHBF and resting forearm blood flows were measured using venous occlusion strain-gauge plethysmography (ml X min-1 X 100 ml-1). Resting forearm blood flows were similar in both arms of both groups. RHBF5ex was similar in both arms of our control group (dominant, 40.8 +/- 1.2 vs. nondominant, 40.9 +/- 2.1). However, RHBF5ex was 42% higher in the dominant than in the nondominant forearms of our tennis player population (dominant, 48.7 +/- 4.0 vs. nondominant, 34.4 +/- 3.4; P less than 0.05). This intraindividual difference in peak forearm blood flows was not secondary to improved systemic conditioning since the maximal O2 consumptions in the two study groups were similar (controls, 45.4 +/- 3.9 vs. tennis players, 46.1 +/- 1.7). These findings suggest a primary peripheral cardiovascular adaptation to exercise training in the dominant forearms of the tennis players resulting in a greater maximal vasodilatation.

Cardiovascular and flux relationships in canine ileum

1984 ◽  
Vol 247 (4) ◽  
pp. G357-G365
Author(s):  
D. Mailman
Keyword(s):  
Blood Flow ◽  
Sodium Nitroprusside ◽  
Capillary Pressure ◽  
Infusion Rate ◽  
Mesenteric Artery ◽  
Arterial Occlusion ◽  
Venous Occlusion ◽  
Anesthetized Dogs ◽  
Nitroprusside Infusion

Blood flow and pressure in denerved ileum of anesthetized dogs were altered by occlusion of the mesenteric artery or vein or by infusion of intra-arterial sodium nitroprusside (0.015-1.5 mg/min). Unidirectional Na and H2O fluxes were measured and absorptive site blood flow was estimated from the clearance of tritiated H2O. Net Na and H2O absorptions were reduced by mesenteric venous or arterial occlusion. Net secretion occurred with mesenteric venous occlusion. Nitroprusside reduced net absorption only at an infusion rate of 0.15 mg/min. The absorptive Na and H2O fluxes were reduced by both mesenteric venous or arterial occlusion, with venous occlusion being more effective. Nitroprusside reduced the absorptive Na flux at an infusion rate of 0.15 mg/min but not the absorptive H2O flux. The secretory flux of Na was increased by mesenteric venous occlusion but reduced by arterial occlusion and not changed by nitroprusside infusion. The secretory H2O flux was decreased by moderate degrees of mesenteric venous occlusion but was unchanged at greater levels. Arterial occlusion decreased secretory H2O fluxes. Nitroprossude infusion increased secretory H2O fluxes at an infusion rate of 0.015 mg/min. The absorptive and secretory Na and H2O fluxes were significantly correlated with absorptive site blood flow plus estimated capillary pressure. Absorptive site blood flow was primarily responsible for changes in absorptive fluxes and estimated capillary pressure for changes in secretory fluxes. Absorptive site blood flow affected the secretory and absorptive fluxes of H2O more equally than the Na fluxes.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement by Venous Occlusion Plethysmography of Blood Flow through Surgically Created Arteriovenous Fistulae in the Human Forearm

1976 ◽  
Vol 50 (1) ◽  
pp. 43-49
Author(s):  
W. F. M. Wallace ◽  
J. P. Jamison
Keyword(s):  
Blood Flow ◽  
Arterial Occlusion ◽  
Venous Occlusion ◽  
Limited Range ◽  
Similar Amount ◽  
Absolute Value ◽  
Human Forearm ◽  
Flow Through ◽  
The Difference ◽  
Two Sides

1. Plethysmographs containing the hand plus forearm were used to measure blood flow in patients with a surgically created arteriovenous fistula in one forearm. 2. Apparent flow rate was stable over a limited range of collecting pressures; the absolute value of these pressures varied from patient to patient. 3. After arterial occlusion, blood flow increased by a similar amount on the normal side and on the side with the fistula. 4. Occlusion of fistular flow produced no significant change in heart rate. 5. Fistular flow, estimated as the difference between flow on the two sides, averaged 525 ml/min in seventeen patients.

The Influence Of Cyclooxygenase Inhibitors On Peripheral Blood Flow In Man

1981 ◽  
Author(s):  
J E Tooke ◽  
H Tindall
Keyword(s):  
Blood Flow ◽  
Vascular Reactivity ◽  
Peak Flow ◽  
Arterial Occlusion ◽  
Cyclooxygenase Inhibitors ◽  
Diabetic Patients ◽  
Peripheral Blood Flow ◽  
Reactive Hyperaemia ◽  
Double Blind ◽  
Significant Prolongation

Previous work has shown that inhibition of cyclooxygenase with indomethacin and flurbiprofen blunts post-occlusive reactive hyperaemia in man. Patients with diabetes mellitus exhibit a similar control-related impairment in vascular response due to their underlying disease. We were therefore concerned that the use of cyclooxygenase inhibitors in these patients might further impair vascular reactivity. We studied nine insulin-dependent diabetics with retinopathy who were given either aspirin 330mg + dipyridamole 75mg tds or placebo according to a randomised double-blind cross-over protocol. Calf and digital perfusion were measured using an ECG-triggered mercury strain gauge pleth-ysmograph (Janssen, Peri flew) which provided a semi-continuous computerized calculation of blood flow. Rest flow (RF) was measured following full acclimatization in a constant temperature room. Peak flow (PF) was assessed from the reactive hyperaemia following a four minute period of arterial occlusion. The aspirin- dipyridamole combination caused a significant reduction in mean PF : RF ratio (9.2: 7.2, p<0.0l) measured in the calf, and a significant prolongation of the mean time for 50% decay of peak flow (l9.7 to 26.0 seconds, p<0.02). A significant reduction also occurred in digital PF : RF ratio following aspirin-dipyridamole (5-0: 3-7, p<0.05). These results suggest that moderate doses of cyclooxygenase inhibitors prescribed for their platelet-inhibiting action may have profound effects on vascular reactivity. In diabetic patients the effects may add to a pre-existent abnormality.

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