Manipulation of central blood volume and implications for respiratory control function

2014 ◽  
Vol 306 (12) ◽  
pp. H1669-H1678 ◽  
Author(s):  
Tadayoshi Miyamoto ◽  
Damian Miles Bailey ◽  
Hidehiro Nakahara ◽  
Shinya Ueda ◽  
Masashi Inagaki ◽  
...  
Keyword(s):  
Blood Volume ◽  
Lower Body Negative Pressure ◽  
Control Function ◽  
Minute Ventilation ◽  
Water Immersion ◽  
Respiratory Control ◽  
Intersection Point ◽  
Operating Point ◽  
Central Blood Volume ◽  
End Tidal

The respiratory operating point (ventilatory or arterial Pco2 response) is determined by the intersection point between the controller and plant subsystem elements within the respiratory control system. However, to what extent changes in central blood volume (CBV) influence these two elements and the corresponding implications for the respiratory operating point remain unclear. To examine this, 17 apparently healthy male participants were exposed to water immersion (WI) or lower body negative pressure (LBNP) challenges to manipulate CBV and determine the corresponding changes. The respiratory controller was characterized by determining the linear relationship between end-tidal Pco2 (PetCO2) and minute ventilation (V̇e) [V̇e = S × (PetCO2 − B)], whereas the plant was determined by the hyperbolic relationship between V̇e and PetCO2 (PetCO2 = A/V̇e + C). Changes in V̇e at the operating point were not observed under either WI or LBNP conditions despite altered PetCO2 ( P < 0.01), indicating a moving respiratory operating point. An increase (WI) and a decrease (LBNP) in CBV were shown to reset the controller element (PetCO2 intercept B) rightward and leftward, respectively ( P < 0.05), without any change in S, whereas the plant curve remained unaltered at the operating point. Collectively, these findings indicate that modification of the controller element rather than the plant element is the major factor that contributes toward an alteration of the respiratory operating point during CBV shifts.

Contribution of abdomen and legs to central blood volume expansion in humans during immersion

1997 ◽  
Vol 83 (3) ◽  
pp. 695-699 ◽  
Author(s):  
Lars Bo Johansen ◽  
Thomas Ulrik Skram Jensen ◽  
Bettina Pump ◽  
Peter Norsk
Keyword(s):  
Blood Volume ◽  
Volume Expansion ◽  
Protein Concentration ◽  
Water Immersion ◽  
Venous Pressure ◽  
Cuff Inflation ◽  
Central Blood Volume ◽  
Central Venous ◽  
Plasma Protein Concentration ◽  
Blood Volume Expansion

Johansen, Lars Bo, Thomas Ulrik Skram Jensen, Bettina Pump, and Peter Norsk. Contribution of abdomen and legs to central blood volume expansion in humans during immersion. J. Appl. Physiol. 83(3): 695–699, 1997.—The hypothesis was tested that the abdominal area constitutes an important reservoir for central blood volume expansion (CBVE) during water immersion in humans. Six men underwent 1) water immersion for 30 min (WI), 2) water immersion for 30 min with thigh cuff inflation (250 mmHg) during initial 15 min to exclude legs from contributing to CBVE (WI+Occl), and 3) a seated nonimmersed control with 15 min of thigh cuff inflation (Occl). Plasma protein concentration and hematocrit decreased from 68 ± 1 to 64 ± 1 g/l and from 46.7 ± 0.3 to 45.5 ± 0.4% ( P < 0.05), respectively, during WI but were unchanged during WI+Occl. Left atrial diameter increased from 27 ± 2 to 36 ± 1 mm ( P < 0.05) during WI and increased similarly during WI+Occl from 27 ± 2 to 35 ± 1 mm ( P < 0.05). Central venous pressure increased from −3.7 ± 1.0 to 10.4 ± 0.8 mmHg during WI ( P < 0.05) but only increased to 7.0 ± 0.8 mmHg during WI+Occl ( P < 0.05). In conclusion, the dilution of blood induced by WI to the neck is caused by fluid from the legs, whereas the CBVE is caused mainly by blood from the abdomen.

Living high-training low increases hypoxic ventilatory response of well-trained endurance athletes

2002 ◽  
Vol 93 (4) ◽  
pp. 1498-1505 ◽  
Author(s):  
Nathan E. Townsend ◽  
Christopher J. Gore ◽  
Allan G. Hahn ◽  
Michael J. McKenna ◽  
Robert J. Aughey ◽  
...  
Keyword(s):  
Ventilatory Response ◽  
Minute Ventilation ◽  
Respiratory Control ◽  
Endurance Athletes ◽  
Hypoxic Exposure ◽  
Dependent Manner ◽  
Hypoxic Ventilatory Response ◽  
Ambient Conditions ◽  
Altitude Exposure ◽  
End Tidal

This study determined whether “living high-training low” (LHTL)-simulated altitude exposure increased the hypoxic ventilatory response (HVR) in well-trained endurance athletes. Thirty-three cyclists/triathletes were divided into three groups: 20 consecutive nights of hypoxic exposure (LHTLc, n = 12), 20 nights of intermittent hypoxic exposure (four 5-night blocks of hypoxia, each interspersed with 2 nights of normoxia, LHTLi, n = 10), or control (Con, n = 11). LHTLc and LHTLi slept 8–10 h/day overnight in normobaric hypoxia (∼2,650 m); Con slept under ambient conditions (600 m). Resting, isocapnic HVR (ΔV˙e/ΔSpO2 , whereV˙e is minute ventilation and SpO2 is blood O2 saturation) was measured in normoxia before hypoxia (Pre), after 1, 3, 10, and 15 nights of exposure (N1, N3, N10, and N15, respectively), and 2 nights after the exposure night 20 (Post). Before each HVR test, end-tidal Pco 2(Pet CO2 ) and V˙e were measured during room air breathing at rest. HVR (l · min−1 · %−1) was higher ( P < 0.05) in LHTLc than in Con at N1 (0.56 ± 0.32 vs. 0.28 ± 0.16), N3 (0.69 ± 0.30 vs. 0.36 ± 0.24), N10 (0.79 ± 0.36 vs. 0.34 ± 0.14), N15 (1.00 ± 0.38 vs. 0.36 ± 0.23), and Post (0.79 ± 0.37 vs. 0.36 ± 0.26). HVR at N15 was higher ( P < 0.05) in LHTLi (0.67 ± 0.33) than in Con and in LHTLc than in LHTLi. Pet CO2 was depressed in LHTLc and LHTLi compared with Con at all points after hypoxia ( P < 0.05). No significant differences were observed for V˙e at any point. We conclude that LHTL increases HVR in endurance athletes in a time-dependent manner and decreases Pet CO2 in normoxia, without change inV˙e. Thus endurance athletes sleeping in mild hypoxia may experience changes to the respiratory control system.

Cerebral hypoperfusion modifies the respiratory chemoreflex during orthostatic stress

2013 ◽  
Vol 125 (1) ◽  
pp. 37-44 ◽  
Author(s):  
Shigehiko Ogoh ◽  
Hidehiro Nakahara ◽  
Kazunobu Okazaki ◽  
Damian M. Bailey ◽  
Tadayoshi Miyamoto
Keyword(s):  
Lower Body Negative Pressure ◽  
Minute Ventilation ◽  
Regression Line ◽  
Cerebral Hypoperfusion ◽  
Orthostatic Stress ◽  
Respiratory Chemoreflex ◽  
Underlying Mechanisms ◽  
End Tidal ◽  
Induced Changes ◽  
The Relationship

The respiratory chemoreflex is known to be modified during orthostatic stress although the underlying mechanisms remain to be established. To determine the potential role of cerebral hypoperfusion, we examined the relationship between changes in MCA Vmean (middle cerebral artery mean blood velocity) and V̇E (pulmonary minute ventilation) from supine control to LBNP (lower body negative pressure; −45mmHg) at different CO2 levels (0, 3.5 and 5% CO2). The regression line of the linear relationship between V̇E and PETCO2 (end-tidal CO2) shifted leftwards during orthostatic stress without any change in sensitivity (1.36±0.27 l/min per mmHg at supine to 1.06±0.21 l/min per mmHg during LBNP; P=0.087). In contrast, the relationship between MCA Vmean and PETCO2 was not shifted by LBNP-induced changes in PETCO2. However, changes in V̇E from rest to LBNP were more related to changes in MCA Vmean than changes in PETCO2. These findings demonstrate for the first time that postural reductions in CBF (cerebral blood flow) modified the central respiratory chemoreflex by moving its operating point. An orthostatically induced decrease in CBF probably attenuated the ‘washout’ of CO2 from the brain causing hyperpnoea following activation of the central chemoreflex.

Effect of central hypervolemia on cardiac performance during exercise

1984 ◽  
Vol 57 (6) ◽  
pp. 1662-1667 ◽  
Author(s):  
L. M. Sheldahl ◽  
L. S. Wann ◽  
P. S. Clifford ◽  
F. E. Tristani ◽  
L. G. Wolf ◽  
...  
Keyword(s):  
Heart Rate ◽  
Blood Volume ◽  
Water Immersion ◽  
Left Ventricular ◽  
Cardiac Performance ◽  
Central Blood Volume ◽  
Supine Posture ◽  
Left Ventricular Dimensions ◽  
Submaximal Work ◽  
And Performance

To investigate the effect of different levels of central blood volume on cardiac performance during exercise, M-mode echocardiography was utilized to determine left ventricular size and performance during cycling exercise in the upright posture (UP), supine posture (SP), and head-out water immersion (WI). At submaximal work loads requiring a mean O2 consumption (Vo2) of 1.2 1/min and 1.5 1/min, mean left ventricular end-diastolic and end-systolic dimensions were significantly greater (P less than 0.05) with WI than UP. In the SP during exercise, left ventricular dimensions were intermediate between UP and WI. Heart rate did not differ significantly among the three conditions at rest and at submaximal exercise up to a mean Vo2 of 1.8 1/min. However, at a mean Vo2 of 2.4 1/min, heart rate in the UP was significantly greater than WI (P less than 0.01) and the SP (P less than 0.05). Maximal Vo2 did not differ statistically in the three conditions. These data indicate that a change in central blood volume results in alterations in left ventricular end-diastolic and end-systolic dimensions during moderate levels of exercise and a change in heart rate at heavy levels of exercise.

Are you bleeding? Validation of a machine-learning algorithm for determination of blood volume status: application to remote triage

2014 ◽  
Vol 116 (5) ◽  
pp. 486-494 ◽  
Author(s):  
Caroline A. Rickards ◽  
Nisarg Vyas ◽  
Kathy L. Ryan ◽  
Kevin R. Ward ◽  
David Andre ◽  
...  
Keyword(s):  
Machine Learning ◽  
Heart Rate ◽  
Blood Volume ◽  
Learning Algorithm ◽  
Lower Body Negative Pressure ◽  
Physiological Signals ◽  
Machine Learning Algorithm ◽  
Central Blood Volume ◽  
Low Level ◽  
Skin Response

Due to limited remote triage monitoring capabilities, combat medics cannot currently distinguish bleeding soldiers from those engaged in combat unless they have physical access to them. The purpose of this study was to test the hypothesis that low-level physiological signals can be used to develop a machine-learning algorithm for tracking changes in central blood volume that will subsequently distinguish central hypovolemia from physical activity. Twenty-four subjects underwent central hypovolemia via lower body negative pressure (LBNP), and a supine-cycle exercise protocol. Exercise workloads were determined by matching heart rate responses from each LBNP level. Heart rate and stroke volume (SV) were measured via Finometer. ECG, heat flux, skin temperature, galvanic skin response, and two-axis acceleration were obtained from an armband (SenseWear Pro2) and used to develop a machine-learning algorithm to predict changes in SV as an index of central blood volume under both conditions. The algorithm SV was retrospectively compared against Finometer SV. A model was developed to determine whether unknown data points could be correctly classified into these two conditions using leave-one-out cross-validation. Algorithm vs. Finometer SV values were strongly correlated for LBNP in individual subjects (mean r = 0.92; range 0.75–0.98), but only moderately correlated for exercise (mean r = 0.50; range −0.23–0.87). From the first level of LBNP/exercise, the machine-learning algorithm was able to distinguish between LBNP and exercise with high accuracy, sensitivity, and specificity (all ≥90%). In conclusion, a machine-learning algorithm developed from low-level physiological signals could reliably distinguish central hypovolemia from exercise, indicating that this device could provide battlefield remote triage capabilities.

Central blood volume and blood pressure in conscious primates

1988 ◽  
Vol 254 (4) ◽  
pp. H693-H701 ◽  
Author(s):  
K. G. Cornish ◽  
J. P. Gilmore ◽  
T. McCulloch
Keyword(s):  
Blood Pressure ◽  
Blood Volume ◽  
Pulse Pressure ◽  
Left Atrial ◽  
Venous Return ◽  
Lower Body Negative Pressure ◽  
Lower Body ◽  
Central Blood Volume ◽  
Arterial Baroreflex ◽  
Arterial Blood

Conscious intact (I) and sinoaortic-denervated monkeys (SAD) were studied to determine the extent to which high-pressure receptors contribute to the maintenance of arterial blood pressure (BP) when venous return is decreased by hemorrhage (H) or lower body negative pressure (LBNP). In the I animals, mean BP did not decrease significantly until 5% of the estimated blood volume (EBV) was removed, whereas, with sinoaortic denervation, mean BP decreased significantly when less than 2% of EBV was removed. Left atrial pressure (LAP) decreased similarly in both groups of animals. In the I group during LBNP, mean BP did not change significantly, whereas pulse pressure decreased significantly when LBNP was decreased to -5 cmH2O. In the SAD animals, mean BP decreased significantly at an LBNP of -2 cmH2O, and at -5 cmH2O mean BP declined from 134.1 +/- 4 to 102.7 +/- 7 mmHg. LAP decreased similarly in both groups of animals. The data support the view that a nonhypotensive reduction in venous return unloads arterial baroreceptors sufficiently to activate the arterial baroreflex, probably through reductions in pulse pressure. In addition, low-pressure receptors by themselves do not appear to contribute importantly to blood pressure maintenance when venous return is decreased by either LBNP or a nonhypotensive hemorrhage.

Mechanism of attenuated thirst in aging: role of central volume receptors

1997 ◽  
Vol 272 (1) ◽  
pp. R148-R157 ◽  
Author(s):  
N. S. Stachenfeld ◽  
L. DiPietro ◽  
E. R. Nadel ◽  
G. W. Mack
Keyword(s):  
Older People ◽  
Blood Volume ◽  
Volume Expansion ◽  
Water Immersion ◽  
Inhibitory Influence ◽  
Central Blood Volume ◽  
Arterial Blood ◽  
Blood Volume Expansion ◽  
Central Volume ◽  
Older Subjects

To test the hypothesis that the inhibitory action of central blood volume expansion on thirst and renal fluid regulation is attenuated with aging, we monitored the drinking and renal responses of dehydrated older (70 +/- 2 yr, n = 6) and younger (24 +/- 1 yr, n = 6) subjects during 195 min of head-out water immersion (HOI), which shifts blood centrally and increases plasma volume (PV). Subjects dehydrated by exercising for 2 h at 36 degrees C in the evening and refraining from fluids overnight before HOI in 34 degrees C water or a seated control in water perfusion suit [time control (TC)] the next morning. Ad libitum water intake was allowed after 15 min of HOI. Dehydration decreased PV by 10.6 +/- 1 and 7.3 +/- 1.8% (P < 0.05) and increased plasma osmolality by 6 +/- 2 and 7 +/- 1 mosmol/kg H2O (P < 0.05) in older and younger subjects, respectively. Thirst ratings increased in both groups, but pre-HOI thirst perception on a line rating scale was lower in older (69 +/- 8 mm) than younger (94 +/- 6 mm, P < 0.05) subjects. Fifteen minutes of HOI restored PV by 7.8 +/- 1.0 and 5.7 +/- 1.0% in older and younger subjects, respectively, but suppressed thirst rating in younger subjects only (P < 0.05). Fluid intake was reduced in HOI compared with TC in younger (6.3 +/- 0.5 vs. 14.3 +/- 2.2 ml/kg, P < 0.05) but not in older (6.7 +/- 2.1 vs. 8.4 +/- 3.3 ml/kg) subjects. During HOI, older subjects had smaller suppression of plasma renin activity and aldosterone concentration but a greater increase in the plasma atrial natriuretic peptide concentration (P[ANP], P < 0.05). HOI increased fractional sodium excretion in both groups, but mean arterial pressure increased only in the older subjects (P < 0.05). We conclude that the inhibitory influence of central volume expansion on thirst and drinking behavior is diminished with aging. Furthermore, in contrast to younger people, HOI natriuresis is associated with exaggerated increases in P[ANP] and arterial blood pressure in older people, suggesting arterial baroreceptors may be involved in the fluid regulatory response to central blood volume expansion in older people.

Effects of changes in central blood volume on carotid-vasomotor baroreflex sensitivity at rest and during exercise

2006 ◽  
Vol 101 (1) ◽  
pp. 68-75 ◽  
Author(s):  
Shigehiko Ogoh ◽  
R. Matthew Brothers ◽  
Quinton Barnes ◽  
Wendy L. Eubank ◽  
Megan N. Hawkins ◽  
...  
Keyword(s):  
Blood Volume ◽  
Baroreflex Sensitivity ◽  
Lower Body Negative Pressure ◽  
Venous Pressure ◽  
Central Blood Volume ◽  
Arterial Blood ◽  
Baroreflex Function ◽  
Maximal Gain ◽  
Neck Pressure ◽  
The Relationship

The purpose of this investigation was to examine whether the effect of changes in central blood volume on carotid-vasomotor baroreflex sensitivity at rest was the same during exercise. Eight men (means ± SE: age 26 ± 1 yr; height 180 ± 3 cm; weight 86 ± 6 kg) participated in the present study. Sixteen Torr of lower body negative pressure (LBNP) were applied to decrease central venous pressure (CVP) at rest and during steady-state leg cycling at 50% peak O2 uptake (104 ± 20 W). Subsequently, infusions of 25% human serum albumin solution were administered to increase CVP at rest and during exercise. During all protocols, heart rate, arterial blood pressure, and CVP were recorded continuously. At each stage of LBNP or albumin infusion, the maximal gain (Gmax) of the carotid-vasomotor baroreflex function curve was measured using the neck pressure and neck suction technique. LBNP reduced CVP and increased the Gmax of the carotid-vasomotor baroreflex function curve at rest (+63 ± 25%, P = 0.006) and during exercise (+69 ± 19%, P = 0.002). In contrast to the LBNP, increases in CVP resulted in the Gmax of the carotid-vasomotor baroreflex function curve being decreased at rest −8 ± 4% and during exercise −18 ± 5% ( P > 0.05). These findings indicate that the relationship between CVP and carotid-vasomotor baroreflex sensitivity was nonlinear at rest and during exercise and suggests a saturation load of the cardiopulmonary baroreceptors at which carotid-vasomotor baroreflex sensitivity remains unchanged.

Cardiovascular and neuroendocrine responses to water immersion in compensated heart failure

2000 ◽  
Vol 279 (4) ◽  
pp. H1931-H1940 ◽  
Author(s):  
Anders Gabrielsen ◽  
Vibeke B. Sørensen ◽  
Bettina Pump ◽  
Søren Galatius ◽  
Regitze Videbæk ◽  
...  
Keyword(s):  
Heart Failure ◽  
Heart Rate ◽  
Ejection Fraction ◽  
Blood Volume ◽  
Vascular Resistance ◽  
Volume Expansion ◽  
Water Immersion ◽  
Central Blood Volume ◽  
Blood Volume Expansion ◽  
Neuroendocrine Responses

The hypothesis was tested that cardiovascular and neuroendocrine (norepinephrine, renin, and vasopressin) responses to central blood volume expansion are blunted in compensated heart failure (HF). Nine HF patients [New York Heart Association class II–III, ejection fraction = 0.28 ± 0.02 (SE)] and 10 age-matched controls (ejection fraction = 0.68 ± 0.03) underwent 30 min of thermoneutral (34.7 ± 0.02°C) water immersion (WI) to the xiphoid process. WI increased ( P < 0.05) central venous pressure by 3.7 ± 0.6 and 3.2 ± 0.4 mmHg and stroke volume index by 12.2 ± 2.1 and 7.2 ± 2.1 ml · beat−1 · m−2 in controls and HF patients, respectively. During WI, systemic vascular resistance decreased ( P < 0.05) similarly by 365 ± 66 and 582 ± 227 dyn · s · cm−5 in controls and HF patients, respectively. Forearm subcutaneous vascular resistance decreased by 19 ± 7% ( P < 0.05) in controls but did not change in HF patients. Heart rate decreased less during WI in HF patients, whereas release of norepinephrine, renin, and vasopressin was suppressed similarly in the two groups. We suggest that reflex control of forearm vascular beds and heart rate is blunted in compensated HF but that baroreflex-mediated systemic vasodilatation and neuroendocrine responses to central blood volume expansion are preserved.

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