A biphasic model of limb venous compliance: a comparison with linear and exponential models

Risk, Marcelo; Lirofonis, Vasilios; Armentano, Ricardo; Freeman, Roy

doi:10.1152/japplphysiol.00932.2002

Cited by 17 publications

(10 citation statements)

References 21 publications

(22 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…2B and METHODS). In contrast to others, we did not increase the intravascular pressure by means of a thigh cuff (6,17,20,34,39,47), but applied negative pressure around the leg caused by LBNP.…”

Section: Discussioncontrasting

confidence: 84%

Sex-related effects on venous compliance and capillary filtration in the lower limb

Lindenberger

Länne²

2007

American Journal of Physiology-Regulatory, Integrative and Comp

View full text Add to dashboard Cite

Recent studies in humans have suggested sex differences in venous compliance of the lower limb, with lower compliance in women. Capillary fluid filtration could, however, be a confounder in the evaluation of venous compliance. The venous capacitance and capillary filtration response in the calves of 12 women (23.2 Ϯ 0.5 years) and 16 men (22.9 Ϯ 0.5 years) were studied during 8 min lower body negative pressure (LBNP) of 11, 22, and 44 mmHg. Calf venous compliance is dependent on pressure and was determined using the first derivative of a quadratic regression equation that described the capacitance-pressure relationship [compliance ϭ ␤ 1 ϩ (2 ⅐ ␤2 ⅐ transmural pressure)]. We found a lower venous compliance in women at low transmural pressures, and the venous capacitance in men was increased (P Ͻ 0.05). However, the difference in compliance between sexes was reduced and not seen at higher transmural pressures. Net capillary fluid filtration and capillary filtration coefficient (CFC) were greater in women than in men during LBNP (P Ͻ 0.05). Furthermore, calf volume increase (capacitance response ϩ total capillary filtration) during LBNP was equivalent in both sexes. When total capillary filtration was not subtracted from the calf capacitance response in the calculation of venous compliance, the sex differences disappeared, emphasizing that venous compliance measurement should be corrected for the contribution of CFC. lower body negative pressure; capillary filtration coefficient; venous capacitance THE VENOUS SECTION OF THE cardiovascular system can be looked upon as a voluminous blood reservoir (70% of total blood volume), designed to preserve a proper inflow of blood into the heart during various cardiovascular adjustments. Thus central venous pressure and filling of the heart may be maintained at a fairly stable level, despite variations in venous blood volume (49). During upright posture, however, the pooling of blood in the veins of the lower part of the body decreases central blood volume and venous return (4, 5, 16). The venous compartment in the legs, rather than the pelvic or abdominal region, seems to have a hemodynamic impact during lower body negative pressure (LBNP) (16), and in studies on men, a greater calf venous compliance has been linked to an increased venous capacitance response with a concomitant reduction in central blood volume (44,56). This, in turn, elicits an increased sympathetic response with higher peripheral resistance and increased heart rate (4, 5, 10, 16, 44, 58). Thus venous compliance of the lower limb may have an impact on cardiovascular responses to orthostatic stress and orthostatic tolerance, although there might be differences between sexes confounding such a link (4).Women are more susceptible to orthostatic stress than men (4,10,13,40,51,58), and in accordance with some findings in the arterial tree, it may be hypothesized that women have greater venous compliance in the lower limbs predisposing to orthostatic intolerance (52). This seems to be refuted however, by recent fi...

show abstract

Section: Discussioncontrasting

confidence: 84%

Sex-related effects on venous compliance and capillary filtration in the lower limb

Lindenberger

Länne²

2007

American Journal of Physiology-Regulatory, Integrative and Comp

View full text Add to dashboard Cite

show abstract

“…The pressure-volume rela tionship in the vein is dependent on tissue pressure and, therefore, on the used cuff pressure (10,14,17,32). Using the first (linear) part of the pressure-volume relationship can adequately represent VeC, especially when using intrave- nous pressure measurements, and makes comparisons be tween the different situations possible (32).…”

Section: Discussionmentioning

confidence: 99%

Venous response to orthostatic stress

Krabbendam¹,

Jacobs²,

Lotgering³

et al. 2008

American Journal of Physiology-Heart and Circulatory Physiology

View full text Add to dashboard Cite

Additional material and information about A J P -H eart a n d Circulatory Physiology can be found at:http://www.the-aps.org/publications/ajpheart This infomation is current as of May 11, 2011.A JP -H eart and Circulatory Physiology publishes original investigations on the physiology of the heart, blood vessels, and lymphatics, including experimental and theoretical studies of cardiovascular function at all levels of organization ranging from the intact animal to the cellular, subcellular, and molecular levels. (HUT) induces a re duction in preload, which is thought to be restored through sym pa thetic venoconstriction, reducing unstressed volume (Vu) and venous compliance (VeC). In this study, we assessed venous inflow and outflow responses and their reproducibility and determined the rela tion with autonomic function during HUT. Eight healthy non-pregnant women were subjected to 20° head-down tilt to 60° HUT at 20° intervals. A t each rotational step, we random ly assessed forearm pressure-volume (P-V) curves (venous occlusion plethysmography) during inflow (VeCIN) and outflow [venous emptying rate (VERoUT)]. V eCIN was defined as the ratio o f the slope of the volume-time curve and pressure-time curve, with direct intravenous pressure m easure ment. V EROUT was determined using the derivate of a quadratic regression m odel using cuff pressure. W e defined Vu as the y-intercept of the P-V curve. W e calculated, for both methods, the coefficients of reproducibility (CR) and variation (CV). V ascular sympathetic activ ity was determined by spectral analysis. V eCIN decreased at each rotational step compared with the supine position (P < 0.05), whereas VEROUT increased. CR of VeCIN was higher in the supine position than V EROUT but low er during HUT. CV varied between 19% and 25% (VeCIN) and between 12% and 21% (VEROUT). HUT decreased Vu. The change in V eCIN and V EROUT correlated with the change in vascular sympathetic activity (r = -0.36, P < 0.01, and r = 0.48, P < 0.01). This is the first study in which a reproducible reduction in V eCIN and V u and a rise in V EROUT during HUT are documented. The alterations in venous characteristics relate to changes in vascular sym pathetic activity.head-up tilt; venous compliance; venous emptying rate; venous ca pacity; autonomic system

show abstract

“…Another important limitation of the occlusion plethysmographic method is that there is no direct measure of venous pressure and venous endothelial function after direct pharmacological stimuli. 41 A few studies have recently been published on the effects of OC on endothelial function. However, because a wide variety of different techniques were used to evaluate endothelial function in those studies, such as imaging techniques (magnetic resonance, Doppler), in-vitro cultures, serum markers of endothelial dysfunction, and brachial artery plethysmography, a comparison of the results is not possible.…”

Section: Discussionmentioning

confidence: 99%

Effect of a Low-Dose Oral Contraceptive on Venous Endothelial Function in Healthy Young Women: Preliminary Results

Giribela¹,

Rubira²,

Melo³

et al. 2007

Clinics

View full text Add to dashboard Cite

Giribela CRG, Rubira MC, Melo NR de, Plentz RDM, Angelis K de, Moreno H, Consolim-Colombo FM. Effect of a lowdose oral contraceptive on venous endothelial function in healthy young women: preliminary results. Clinics. 2007;62(2): 151-8.BACKGROUND: A possible increase in the incidence of venous thromboembolic events has been reported among users of third generation oral contraceptives. The objective of this study was to evaluate the effect of a low dose oral contraceptive (15 µg ethinyl estradiol/60 µg gestodene) on the venous endothelial function of healthy young women. METHODS: Prospective case control study using the dorsal hand vein technique. Venous endothelial function was evaluated at baseline and after 4 months in the oral contraceptive users group (11 women) and in a control group (9 women). After preconstriction of the vein with phenylephrine, dose-response curves for acetylcholine and sodium nitroprusside were constructed. RESULTS: In the contraceptive users group, a reduction occurred in the maximum venodilation response to acetylcholine and sodium nitroprusside after 4 months of oral contraceptive use, but this difference was not statistically significant (P > 0.05). No significant changes were detected in maximum venodilation responses to acetylcholine and sodium nitroprusside at the 4-month time point in the control group. CONCLUSION: This study found no significant impairment of endothelium-dependent or independent venodilation in healthy young women following oral contraceptive use. Further studies are necessary using the same methodology in a larger sample over a longer follow-up period.

show abstract

A biphasic model of limb venous compliance: a comparison with linear and exponential models

Cited by 17 publications

References 21 publications

Sex-related effects on venous compliance and capillary filtration in the lower limb

Sex-related effects on venous compliance and capillary filtration in the lower limb

Venous response to orthostatic stress

Effect of a Low-Dose Oral Contraceptive on Venous Endothelial Function in Healthy Young Women: Preliminary Results

Contact Info

Product

Resources

About