Effect of lymphatic outflow pressure on lymphatic albumin transport in humans

2001 ◽  
Vol 91 (3) ◽  
pp. 1223-1228 ◽  
Author(s):  
Jauchia Wu ◽  
Gary W. Mack
Keyword(s):  
Protein Transport ◽  
Lower Body Negative Pressure ◽  
Venous Pressure ◽  
Isotonic Saline ◽  
Saline Infusion ◽  
Positive Pressure ◽  
Lower Body ◽  
Lower Body Positive Pressure ◽  
The Difference ◽  
The Impact

The effects of posture on the lymphatic outflow pressure and lymphatic return of albumin were examined in 10 volunteers. Lymph flow was stimulated with a bolus infusion of isotonic saline (0.9%, 12.6 ml/kg body wt) under four separate conditions: upright rest (Up), upright rest with lower body positive pressure (LBPP), supine rest (Sup), and supine rest with lower body negative pressure (LBNP). The increase in plasma albumin content (ΔAlb) during the 2 h after bolus saline infusion was greater in Up than in LBPP: 82.9 ± 18.5 vs. −28.4 mg/kg body wt. ΔAlb was greater in LBNP than in Sup: 92.6 vs. −22.5 ± 18.9 mg/kg body wt ( P < 0.05). The greater ΔAlb in Up and Sup with LBNP were associated with a lower estimated lymphatic outflow pressure on the basis of the difference in central venous pressure (ΔCVP). During LBPP, CVP was increased compared with Up: 3.8 ± 1.4 vs. −1.2 ± 1.2 mmHg. During LBNP, CVP was reduced compared with Sup: −3.0 ± 2.2 vs. 1.7 ± 1.0 mmHg. The translocation of protein into the vascular space after bolus saline infusion reflects lymph return of protein and is higher in Up than in Sup. Modulation of CVP with LBPP or LBNP in Up and Sup, respectively, reversed the impact of posture on lymphatic outflow pressure. Thus posture-dependent changes in lymphatic protein transport are modulated by changes in CVP through its mechanical impact on lymphatic outflow pressure.

Hemodynamic responses to graded lower body positive pressure

1993 ◽  
Vol 265 (1) ◽  
pp. H69-H73 ◽  
Author(s):  
X. Shi ◽  
C. G. Crandall ◽  
P. B. Raven
Keyword(s):  
Forearm Blood Flow ◽  
Venous Pressure ◽  
Positive Pressure ◽  
Intramuscular Pressure ◽  
Lower Body ◽  
Central Venous ◽  
Lower Body Positive Pressure ◽  
Pressure Sensitive ◽  
Body Positive ◽  
Forearm Vascular Resistance

Fourteen healthy young men were exposed to progressive increases in lower body positive pressure (LBPP) from 0 to 40 Torr in the supine position. Central venous pressure (CVP) increased 1.09 mmHg (P < 0.05) at 5 Torr LBPP. Between 20 and 40 Torr LBPP CVP increased 0.85 mmHg, resulting in a total increase of 2.06 mmHg (P < 0.05). During 0–20 Torr LBPP mean arterial pressure (MAP) increased from 86 to 89 mmHg with a slope of 0.15 mmHg/Torr LBPP. Stroke volume and cardiac output were significantly increased at 20 Torr LBPP. Beyond 20 Torr LBPP, MAP increased to 95 mmHg at 40 Torr (P < 0.05) with a slope of 0.32 mmHg/Torr LBPP. Forearm blood flow increased above rest at 40 Torr LBPP (P< 0.05). However, neither peripheral nor forearm vascular resistance decreased significantly from rest. Despite the significant increases in MAP, heart rate was unchanged above 20 Torr LBPP. These data suggest that LBPP produces increases in CVP at 0–20 Torr by translocation of blood volume from the legs to the thorax. At LBPP > 20 Torr, further increases in CVP and MAP were produced by other mechanisms possibly related to an activation of intramuscular pressure-sensitive receptors.

Cardiovascular responses to apneic facial immersion during altered cardiac filling

2003 ◽  
Vol 94 (6) ◽  
pp. 2249-2254 ◽  
Author(s):  
W. Shane Journeay ◽  
Francis D. Reardon ◽  
Glen P. Kenny
Keyword(s):  
Lower Body Negative Pressure ◽  
Cardiovascular Responses ◽  
Positive Pressure ◽  
Control Mechanisms ◽  
Lower Body ◽  
Lower Body Positive Pressure ◽  
Body Positive ◽  
Postexercise Hypotension ◽  
Cardiac Filling ◽  
Facial Immersion

The hypothesis that reduced cardiac filling, as a result of lower body negative pressure (LBNP) and postexercise hypotension (PEH), would attenuate the reflex changes to heart rate (HR), skin blood flow (SkBF), and mean arterial pressure (MAP) normally induced by facial immersion was tested. The purpose of this study was to investigate the cardiovascular control mechanisms associated with apneic facial immersion during different cardiovascular challenges. Six subjects randomly performed 30-s apneic facial immersions in 6.0 ± 1.2°C water under the following conditions: 1) −20 mmHg LBNP, 2) +40 mmHg lower body positive pressure (LBPP), 3) during a period of PEH, and 4) normal resting (control). Measurements included SkBF at one acral (distal phalanx of the thumb) and one nonacral region of skin (ventral forearm), HR, and MAP. Facial immersion reduced HR and SkBF at both sites and increased MAP under all conditions ( P < 0.05). Reduced cardiac filling during LBNP and PEH significantly attenuated the absolute HR nadir observed during the control immersion ( P < 0.05). The LBPP condition did not result in a lower HR nadir than control but did result in a nadir significantly lower than that of the LBNP and PEH conditions ( P < 0.05). No differences were observed in either SkBF or MAP between conditions; however, the magnitude of SkBF reduction was greater at the acral site than at the nonacral site for all conditions ( P < 0.05). These results suggest that the cardiac parasympathetic response during facial immersion can be attenuated when cardiac filling is compromised.

Baroreceptor-mediated suppression of osmotically stimulated vasopressin in normal humans

1988 ◽  
Vol 65 (3) ◽  
pp. 1226-1230 ◽  
Author(s):  
S. R. Goldsmith
Keyword(s):  
Heart Rate ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Central Venous Pressure ◽  
Venous Pressure ◽  
Positive Pressure ◽  
Lower Body ◽  
Central Venous ◽  
Lower Body Positive Pressure ◽  
Body Positive

Increases in central venous pressure and arterial pressure have been reported to have variable effects on normal arginine vasopressin (AVP) levels in healthy humans. To test the hypothesis that baroreceptor suppression of AVP secretion might be more likely if AVP were subjected to a prior osmotic stimulus, we investigated the response of plasma AVP to increased central venous pressure and mean arterial pressure after hypertonic saline in six normal volunteers. Plasma AVP, serum osmolality, heart rate, central venous pressure, mean arterial pressure, and pulse pressure were assessed before and after a 0.06 ml.kg-1.min-1-infusion of 5% saline give over 90 min and then after 10 min of 30 degrees head-down tilt and 10 min of head-down tilt plus lower-body positive pressure. Hypertonic saline increased plasma AVP. After head-down tilt, which did not change heart rate, pulse pressure, or mean arterial pressure but did increase central venous pressure, plasma AVP fell. Heart rate, pulse pressure, and central venous pressure were unchanged from head-down tilt values during lower-body positive pressure, whereas mean arterial pressure increased. Plasma AVP during lower-body positive pressure was not different from that during tilt. Osmolality increased during the saline infusion but was stable throughout the remainder of the study. These data therefore suggest that an osmotically stimulated plasma AVP level can be suppressed by baroreflex activation. Either the low-pressure cardiopulmonary receptors (subjected to a rise in central venous pressure during head-down tilt) or the sinoaortic baroreceptors (subjected to hydrostatic effects during head-down tilt) could have been responsible for the suppression of AVP.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Comparison of cardiovascular and biomechanical parameters of supine lower body negative pressure and upright lower body positive pressure to simulate activity in 1/6 G and 3/8 G

2013 ◽  
Vol 115 (2) ◽  
pp. 275-284 ◽  
Author(s):  
Thomas Schlabs ◽  
Armando Rosales-Velderrain ◽  
Heidi Ruckstuhl ◽  
Alexander C. Stahn ◽  
Alan R. Hargens
Keyword(s):  
Negative Pressure ◽  
Ground Reaction Force ◽  
Lower Body Negative Pressure ◽  
Reaction Force ◽  
Positive Pressure ◽  
Lower Body ◽  
Lower Body Positive Pressure ◽  
Body Positive ◽  
Biomechanical Parameters ◽  
Predicted Values

For future space exploration missions, it is important to determine the best method of simulating on Earth cardiovascular and biomechanical conditions for lunar and Martian gravities. For this purpose, we compared exercise performed within a lower body negative pressure (LBNP) and a lower body positive pressure (LBPP) chamber. Twelve subjects underwent a protocol of resting and walking (0.25 Froude) within supine LBNP and upright LBPP simulation. Each protocol was performed in simulated 1/6 G and 3/8 G. We assessed heart rate (HR), mean arterial blood pressure, oxygen consumption (V̇o2), normalized stride length, normalized vertical peak ground reaction force, duty factor, cadence, perceived exertion (Borg), and comfort of the subject. A mixed linear model was employed to determine effects of the simulation on the respective parameters. Furthermore, parameters were compared with predicted values for lunar and Martian gravities to determine the method that showed the best agreement. During walking, all cardiovascular and biomechanical parameters were unaffected by the simulation used for lunar and Martian gravities. During rest, HR and V̇o2 were lower in supine LBNP compared with upright LBPP. HR, V̇o2, and normalized vertical peak ground reaction force obtained with supine LBNP and upright LBPP showed good agreement with predicted values. Since supine LBNP and upright LBPP are lacking significant differences, we conclude that both simulations are suited to simulate the cardiovascular and biomechanical conditions during activity in lunar and Martian gravities. Operational characteristics and the intended application should be considered when choosing either supine LBNP or upright LBPP to simulate partial gravities on Earth.

scholarly journals How to build a lower-body differential pressure chamber integrated on a tilt-table: A pedagogy tool to demonstrate the cardiovagal baroreflex

FACETS ◽  
2017 ◽  
Vol 1 (1) ◽  
pp. 225-244 ◽  
Author(s):  
Michael M. Tymko
Keyword(s):  
High Performance ◽  
Lower Body Negative Pressure ◽  
Body Position ◽  
Positive Pressure ◽  
Lower Body ◽  
Tilt Table ◽  
Lower Body Positive Pressure ◽  
Research And Teaching ◽  
Body Positive ◽  
Health Related

The cardiovagal baroreflex is an important physiological reflex that is commonly taught in health-related university physiology courses. This reflex is responsible for the rapid maintenance of blood pressure through dynamic changes in heart rate (HR) and vascular resistance. The use of lower-body negative pressure (LBNP) and lower-body positive pressure (LBPP) can manipulate these stretch sensitive baroreceptors. High performance and relatively inexpensive homemade LBNP and LBPP chambers can be easily constructed providing a valuable tool for both research and teaching purposes. There has been previous documentation of how to build a LBNP chamber; however, the information available usually lacks appropriate construction details, and there is currently no literature on how to build a chamber that can accommodate both LBNP and LBPP. In addition, a recently developed novel LBNP/LBPP chamber positioned on a 360° tilt-table provided the unique utility of superimposing both LBNP/LBPP and body position as independent or combined stressors to alter central blood volume. The primary purposes of this manuscript are to (1) provide step-by-step instructions on how to build a tilt-table LBNP/LBPP chamber, and (2) demonstrate the effectiveness of a tilt-table LBNP/LBPP chamber to facilitate undergraduate and graduate learning in the laboratory by effectively demonstrating the cardiovagal baroreflex.

Reflex activation of sympathetic nervous system by ANF in humans

1988 ◽  
Vol 255 (3) ◽  
pp. H685-H689
Author(s):  
T. J. Ebert
Keyword(s):  
Nervous System ◽  
Sympathetic Nervous System ◽  
Sympathetic Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Venous Pressure ◽  
Isotonic Saline ◽  
Positive Pressure ◽  
Base Line ◽  
Lower Body Positive Pressure ◽  
Sympathetic Nervous

Recent studies in experimental animal preparations suggest that ANF might alter sympathetic nervous system function. In the present investigation, direct recordings of postganglionic muscle sympathetic nerve activity were obtained from the peroneal nerve of conscious human volunteers. These data and hemodynamic parameters were recorded before and during infusions of atrial natriuretic factor (ANF, 99–126) or placebo (isotonic saline) in 10 subjects. Base-line ANF (36.5 +/- 3.8) increased to 329 +/- 22 pg/ml during 20-min infusions of ANF (15 ng.kg-1.min-1). This did not alter heart rate or blood pressure but reduced central venous pressure (CVP) by 47 +/- 10% (P less than 0.01). Base-line-integrated sympathetic activity (14.4 +/- 2.4 bursts/min) increased 30 +/- 12% during ANF infusion (P less than 0.05). However, when CVP was fixed at control levels with head-down tilt or lower body positive pressure, sympathetic activity was unchanged from pre-ANF base-line levels. These data indicate that exogenous infusions of ANF reduced CVP and unloaded cardiopulmonary baroreceptors. This elicits reflex increases of muscle sympathetic efferent activity. When CVP is maintained at control levels, ANF does not alter sympathetic neural outflow to muscles.

Influence of central venous pressure change on plasma vasopressin in humans

1986 ◽  
Vol 61 (4) ◽  
pp. 1352-1357 ◽  
Author(s):  
P. Norsk ◽  
F. Bonde-Petersen ◽  
J. Warberg
Keyword(s):  
Central Venous Pressure ◽  
Lower Body Negative Pressure ◽  
Venous Pressure ◽  
Plasma Osmolality ◽  
Hemoglobin Concentration ◽  
Positive Pressure ◽  
Fluid Restriction ◽  
Lower Body ◽  
Central Venous ◽  
The Subject

After overnight food and fluid restriction, nine healthy males were examined before, during, and after lower body positive pressure (LBPP) of 11 +/- 1 mmHg (mean +/- SE) for 30 min and before, during, and after graded lower body negative pressure (LBNP) of -10 +/- 1, -20 +/- 2, and -30 +/- 2 mmHg for 20 min each. LBPP and LBNP were performed with the subject in the supine position in a plastic box encasing the subject from the xiphoid process and down, thus including the splanchnic area. Central venous pressure (CVP) during supine rest was 7.5 +/- 0.5 mmHg, increasing to 13.4 +/- 0.8 mmHg (P less than 0.001) during LBPP and decreasing significantly at each step of LBNP to 2.0 +/- 0.5 mmHg (P less than 0.001) at 15 min of -30 +/- 2 mmHg LBNP. Plasma arginine vasopressin (AVP) did not change significantly in face of this large variation in CVP of 11.4 mmHg. Mean arterial pressure increased significantly during LBPP from 100 +/- 2 to 117 +/- 3 Torr (P less than 0.001) and only at one point during LBNP of -30 +/- 2 mmHg from 102 +/- 1 to 115 +/- 5 mmHg (P less than 0.05). Heart rate did not change during LBPP but increased slightly from 51 +/- 3 to 55 +/- 3 beats/min (P less than 0.05) only at 7 min of LBNP of -30 +/- 2 mmHg. Plasma osmolality, sodium, and potassium did not change during the experiment. Hemoglobin concentration increased during LBPP and LBNP, whereas hematocrit only increased during LBNP.(ABSTRACT TRUNCATED AT 250 WORDS)

Transcapillary fluid responses to lower body negative pressure

1993 ◽  
Vol 74 (6) ◽  
pp. 2763-2770 ◽  
Author(s):  
M. Aratow ◽  
S. M. Fortney ◽  
D. E. Watenpaugh ◽  
A. G. Crenshaw ◽  
A. R. Hargens
Keyword(s):  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Venous Pressure ◽  
Isotonic Saline ◽  
Whole Body ◽  
Chamber Pressure ◽  
Fluid Loss ◽  
Lower Body ◽  
Urine Production ◽  
Saline Ingestion

The effect of lower body negative pressure (LBNP) on transcapillary fluid balance is unknown. Therefore, our objective was to assess leg interstitial fluid pressures (IFP), leg circumference, plasma volume (PV), and net whole body transcapillary fluid transport (TFT) during and after supine LBNP and to evaluate the addition of oral saline ingestion on transcapillary exchange. Six healthy men 23–41 yr old underwent 4 h of 30 mmHg LBNP, followed by 50 min of supine recovery on two separate occasions, once with and once without ingestion of 1 liter of isotonic saline. IFP was measured continuously in subcutis as well as superficial and deep regions of the tibialis anterior muscle by slit catheters. TFT was calculated by subtracting urine production and calculated insensible fluid loss from changes in PV. During exposure to LBNP, IFP decreased in parallel with chamber pressure, foot venous pressure did not change, leg circumference increased by 3 +/- 0.35% (SE) (P < 0.05), and PV decreased by 14 +/- 2.3%. IFP returned to near control levels after LBNP. At the end of minute 50 of recovery, PV remained decreased (by 7.5 +/- 5.2%) and leg circumference remained elevated (by 1 +/- 0.37%). LBNP alone produced significant movement of fluid into the lower body but no net TFT (-7 +/- 12 ml/h). During LBNP with saline ingestion, 72 +/- 4% of the ingested fluid volume filtered out of the vascular space (TFT = 145 +/- 10 ml/h), and PV decreased by 6 +/- 3%.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Preliminary Evidence of Orthostatic Intolerance and Altered Cerebral Vascular Control Following Sport-Related Concussion

2021 ◽  
Vol 12 ◽  
Author(s):  
Morgan L. Worley ◽  
Morgan C. O'Leary ◽  
James R. Sackett ◽  
Zachary J. Schlader ◽  
Barry Willer ◽  
...  
Keyword(s):  
Vascular Function ◽  
Orthostatic Intolerance ◽  
Lower Body Negative Pressure ◽  
Preliminary Evidence ◽  
Positive Pressure ◽  
Lower Body ◽  
Vascular Control ◽  
Lower Body Positive Pressure ◽  
Body Positive ◽  
Cerebral Vascular

Concussions have been shown to result in autonomic dysfunction and altered cerebral vascular function. We tested the hypothesis that concussed athletes (CA) would have altered cerebral vascular function during acute decreases and increases in blood pressure compared to healthy controls (HC). Ten CA (age: 20 ± 2 y, 7 females) and 10 HC (age: 21 ± 2 y, 6 females) completed 5 min of lower body negative pressure (LBNP; −40 mmHg) and 5 min of lower body positive pressure (LBPP; 20 mmHg). Protocols were randomized and separated by 10 min. Mean arterial pressure (MAP) and middle cerebral artery blood velocity (MCAv) were continuously recorded. Cerebral vascular resistance (CVR) was calculated as MAP/MCAv. Values are reported as change from baseline to the last minute achieved (LBNP) or 5 min (LBPP). There were no differences in baseline values between groups. During LBNP, there were no differences in the change for MAP (CA: −23 ± 18 vs. HC: −21 ± 17 cm/s; P = 0.80) or MCAv (CA: −13 ± 8 vs. HC: −18 ± 9 cm/s; P = 0.19). The change in CVR was different between groups (CA: −0.08 ± 0.26 vs. HC: 0.18 ± 0.24 mmHg/cm/s; P = 0.04). Total LBNP time was lower for CA (204 ± 92 s) vs. HC (297 ± 64 s; P = 0.04). During LBPP, the change in MAP was not different between groups (CA: 13 ± 6 vs. HC: 10 ± 7 mmHg; P = 0.32). The change in MCAv (CA: 7 ± 6 vs. HC: −4 ± 13 cm/s; P = 0.04) and CVR (CA: −0.06 ± 0.27 vs. HC: 0.38 ± 0.41 mmHg/cm/s; P = 0.03) were different between groups. CA exhibited impaired tolerance to LBNP and had a different cerebral vascular response to LBPP compared to HC.

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