The location of the human volume indifferent point predicts orthostatic tolerance

Jarvis, Sara S.; Pawelczyk, James A.

doi:10.1007/s00421-009-1336-7

Cited by 5 publications

(8 citation statements)

References 18 publications

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“…With HIP located just below the diaphragm and thus close to the liver, liver venous pressure would not be expected to change during tilt. We identified the indifference point for intravascular volume and confirm that VIP, as indicated by electrical impedance for extracellular, intracellular, and total body fluid is located within the lower abdomen (16,17,28,29). The strength of this study is that HIP and VIP were determined simultaneously and that the location of VIP below the liver was enforced by determination of both body fluid distribution and filling of the ICV (Figs.…”

Section: Discussionsupporting

confidence: 58%

“…Kirsch et al (22) considered HIP to indicate the indifference point not only for intravascular pressure but also for volume (VIP) and from changes in volume of superficial tissue estimated the indifference point to be within the upper abdomen. However, by measuring body fluid with segmental electrical impedance, Perko et al found VIP to be located in the pelvic region (28,29), while Jarvis and Pawelczyk refined the technique and placed VIP in the lower abdomen (16,17). A limitation to these observations is that, while electrical impedance can distinguish between intra-and extracellular compartments, electrical impedance cannot distinguish between intraand extravascular fluid, and it is sensitive to organ migration (13,18).…”

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confidence: 99%

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The hydrostatic pressure indifference point underestimates orthostatic redistribution of blood in humans

Petersen

Carlsen

Nielsen

et al. 2014

Journal of Applied Physiology

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The hydrostatic indifference point (HIP; where venous pressure is unaffected by posture) is located at the level of the diaphragm and is believed to indicate the orthostatic redistribution of blood, but it remains unknown whether HIP coincides with the indifference point for blood volume (VIP). During graded (± 20°) head-up (HUT) and head-down tilt (HDT) in 12 male volunteers, we determined HIP from central venous pressure and VIP from redistribution of both blood, using ultrasound imaging of the inferior caval vein (VIPui), and fluid volume, by regional electrical admittance (VIPadm). Furthermore, we evaluated whether inflation of medical antishock trousers (to 70 mmHg) affected HIP and VIP. Leaving cardiovascular variables unaffected by tilt, HIP was located 7 ± 4 cm (mean ± SD) below the 4th intercostal space (IC-4) during HUT and was similar (7 ± 3 cm) during HDT and higher (P < 0.0001) than both VIPui (HUT: 22 ± 16 cm; HDT: 13 ± 7 cm) and VIPadm (HUT: 29 ± 9 cm; HDT: 20 ± 9 cm below IC-4). During HUT antishock trousers elevated both HIP and VIPui [to 3 ± 5 cm (P = 0.028) and 17 ± 7 cm below IC-4 (P = 0.051), respectively], while VIPadm remained unaffected. By simultaneous recording of pressure and filling of the inferior caval vein as well as fluid distribution, we found HIP located corresponding to the diaphragm while VIP was placed low in the abdomen, and that medical antishock trousers elevated both HIP and VIP. The low indifference point for volume shows that the gravitational influence on distribution of blood is more profound than indicated by the indifference point for venous pressure.

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Section: Discussionsupporting

confidence: 58%

mentioning

confidence: 99%

The hydrostatic pressure indifference point underestimates orthostatic redistribution of blood in humans

Petersen

Carlsen

Nielsen

et al. 2014

Journal of Applied Physiology

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“…Criteria for test termination during LBNP or upright tilt often includes a consistent SBP of Ͻ70 -90 mmHg (6,8,18,20,31,35,36), as well as a 15-to 20-mmHg decrease in SBP (8,15). Therefore, the validity of both absolute BPs and the changes in BP are important to appropriately identify presyncope and thus test termination during LBNP or similar orthostatic testing.…”

Section: Discussionmentioning

confidence: 99%

Validity of auscultatory and Penaz blood pressure measurements during profound heat stress alone and with an orthostatic challenge

Ganio

Lucas

Hastings³

et al. 2011

American Journal of Physiology-Regulatory, Integrative and Comp

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Ganio MS, Brothers RM, Lucas RAI, Hastings JL, Crandall CG. Validity of auscultatory and Penaz blood pressure measurements during profound heat stress alone and with an orthostatic challenge. Am J Physiol Regul Integr Comp Physiol 301: R1510 -R1516, 2011. First published August 10, 2011 doi:10.1152/ajpregu.00247.2011.-Despite frequent reporting of blood pressure (BP) during profound passive heat stress, both with and without a hypotensive challenge, the method by which BP is measured often varies between laboratories. It is unknown whether auscultatory and finger BP measures accurately reflect intra-arterial BP during dynamic changes in cardiac output and peripheral resistance associated with the aforementioned conditions. The purpose of this investigation was to test the hypothesis that auscultatory BP measured at the brachial artery, and finger BP measured by the Penaz method, are valid measures of intra-arterial BP during a passive heat stress and a heat-stressed orthostatic challenge, via lower body negative pressure (LBNP). Absolute (specific aim 1) and the change in (specific aim 2) systolic (SBP), diastolic (DBP), and mean BPs (MBP) were compared at normothermia, after a core temperature increase of 1.47 Ϯ 0.09°C, and during subsequent LBNP. Heat stress did not change auscultatory SBP (6 Ϯ 11 mmHg; P ϭ 0.16), but Penaz SBP (Ϫ22 Ϯ 16 mmHg; P Ͻ 0.001) and intra-arterial SBP (Ϫ11 Ϯ 13 mmHg P ϭ 0.017) decreased. In contrast, DBP and MBP did not differ between methods throughout heat stress. Compared with BP before LBNP, the magnitude of the reduction in BP with all three methods was similar throughout LBNP (P Ͼ 0.05). In conclusion, auscultatory SBP and Penaz SBP failed to track the decrease in intra-arterial SBP that occurred during the profound heat stress, while decreases in arterial BP during an orthostatic challenge are comparable between methodologies. lower body negative pressure; passive heat stress; arterial blood pressure VARIOUS METHODS ARE USED TO measure arterial blood pressure (BP) in the passively heat-stressed human (6,8,18,20,31,35,36). The most valid approach is an intra-arterial catheter connected to a calibrated transducer (BP INTRA ). Although BP INTRA is the gold standard, physician assistance and supervision are often required, and there is significant cost and subject risk, resulting in BP INTRA measurements being prohibitive in most settings.An alternative to BP INTRA is automated auscultatory BP (BP AUSC ). This method is often used because of the relatively low cost, ease of use, and its capacity to be used in a variety of settings (26). However, this method is limited because each measurement requires ϳ30 s, thus prohibiting the use of BP AUSC during conditions when arterial BP is rapidly changing (e.g., when a subject is approaching presyncope during an orthostatic tolerance test).In the 1970's, noninvasive beat-by-beat BP measurements were made possible using a finger cuff coupled with Penaz technology (25). Penaz-derived BP (BP PENAZ ) recordings have been validated for resting...

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“…When humans stand up, gravity pools blood to dependent regions of the body (Matzen, Perko, Groth, Friedman, & Secher, 1991). Thus, the 'indifference point' (where pressure does not change during headup or head-down tilt) for venous pressure is at the level of the diaphragm (Gauer & Thron, 1965), whereas for volume (Jarvis & Pawelczyk, 2010;Perko et al, 1997) and diameter of the inferior caval vein the indifference point is below the liver (Petersen, Carlsen, Nielsen, Damgaard, & Secher, 2014). Consequently, in an upright posture, central venous pressure (CVP) becomes negative, in parallel with reduction in the central blood volume and, therefore, preload to the heart and cardiac output (CO) decrease (Harms, van Lieshout, Jenstrup, Pott, & Secher, 2003;Matzen et al, 1991).…”

Section: Introductionmentioning

confidence: 99%

“…The central blood volume is often taken as the blood within the thoracic cavity as c 2019 The Authors. Experimental Physiology c 2019 The Physiological Society monitored by electrical impedance by Perko et al (1997) and Jarvis and Pawelczyk (2010). Nonetheless, it is the diastolic filling of the heart that is important for the ability to increase CO, but diastolic filling of the heart cannot be determined during whole-body exercise, such as rowing.…”

Section: Introductionmentioning

confidence: 99%

Cardiac output during exercise is related to plasma atrial natriuretic peptide but not to central venous pressure in humans

Yoshiga

Dawson

Volianitis

et al. 2019

Experimental Physiology

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New Findings What is the central question of this study?Is cardiac output during exercise dependent on central venous pressure? What is the main finding and its importance?The increase in cardiac output during both rowing and running is related to preload to the heart, as indicated by plasma atrial natriuretic peptide, but unrelated to central venous pressure. The results indicate that in upright humans, central venous pressure reflects the gravitational influence on central venous blood rather than preload to the heart. Abstract We evaluated the increase in cardiac output (CO) during exercise in relationship to central venous pressure (CVP) and plasma arterial natriuretic peptide (ANP) as expressions of preload to the heart. Seven healthy subjects (four men; mean ± SD: age 26 ± 3 years, height 181± 8 cm and weight 76 ± 11 kg;) rested in sitting and standing positions (in randomized order) and then rowed and ran at submaximal workloads. The CVP was recorded, CO (Modelflow) calculated and arterial plasma ANP determined by radioimmunoassay. While sitting, (mean ± SD) CO was 6.2 ± 1.6 l min−1, plasma ANP 70 ± 10 pg ml−1 and CVP 1.8 ± 1.1 mmHg, and when standing decreased to 5.9 ± 1.0 l min−1, 63 ± 10 pg ml−1 and −3.8 ± 1.2 mmHg, respectively (P < 0.05). Ergometer rowing elicited an increase in CO to 22.5 ± 5.5 l min−1 as plasma ANP increased to 156 ± 11 pg ml−1 and CVP to 3.8 ± 0.9 mmHg (P < 0.05). Likewise, CO increased to 23.5 ± 6.0 l min−1 during running, albeit with a smaller (P < 0.05) increase in plasma ANP, but with little change in CVP (−0.9 ± 0.4 mmHg). The increase in CO in response to exercise is related to preload to the heart, as indicated by plasma ANP, but unrelated to CVP. The results indicate that in upright humans, CVP reflects the gravitational influence on central venous blood rather than preload to the heart.

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The location of the human volume indifferent point predicts orthostatic tolerance

Cited by 5 publications

References 18 publications

The hydrostatic pressure indifference point underestimates orthostatic redistribution of blood in humans

The hydrostatic pressure indifference point underestimates orthostatic redistribution of blood in humans

Validity of auscultatory and Penaz blood pressure measurements during profound heat stress alone and with an orthostatic challenge

Cardiac output during exercise is related to plasma atrial natriuretic peptide but not to central venous pressure in humans

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