Insufficient flow reduction during LBNP in both splanchnic and lower limb areas is associated with orthostatic intolerance after bedrest

Arbeille, Philippe; Kerbeci, P.; Mattar, Louis; Shoemaker, J. Kevin; Hughson, Richard L.

doi:10.1152/ajpheart.509.2008

Cited by 65 publications

(55 citation statements)

References 40 publications

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“…Experiments by others on subjects exposed to lower body negative pressure, which induces haemodynamic responses similar to those observed in hypergravity, showed that there are remarkable differences in regional vascular resistance among various districts (Fischer et al 2007;Arbeille et al 2008a, b), which should be taken into account for a deeper understanding of the circulatory changes that may occur in a hypergravity environment. A vasoconstrictor response may also face to the reduction in circulating blood volume related to increased venous blood stowage, especially in the splanchnic district, and to plasma leakage toward interstitial space, especially in the skin (Eichler et al 2000;Christ et al 2001;Arbeille et al 2008b). The blood pressure response was observed also by Bjurstedt et al (1974), despite the fact that their exercise at 3 g was carried out at a higher relative work load than was performed at 1 g.…”

Section: Discussionmentioning

confidence: 99%

Effects of acceleration in the Gz axis on human cardiopulmonary responses to exercise

et al. 2011

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The aim of this paper was to develop a model from experimental data allowing a prediction of the cardiopulmonary responses to steady-state submaximal exercise in varying gravitational environments, with acceleration in the G(z) axis (a (g)) ranging from 0 to 3 g. To this aim, we combined data from three different experiments, carried out at Buffalo, at Stockholm and inside the Mir Station. Oxygen consumption, as expected, increased linearly with a (g). In contrast, heart rate increased non-linearly with a (g), whereas stroke volume decreased non-linearly: both were described by quadratic functions. Thus, the relationship between cardiac output and a (g) was described by a fourth power regression equation. Mean arterial pressure increased with a (g) non linearly, a relation that we interpolated again with a quadratic function. Thus, total peripheral resistance varied linearly with a (g). These data led to predict that maximal oxygen consumption would decrease drastically as a (g) is increased. Maximal oxygen consumption would become equal to resting oxygen consumption when a (g) is around 4.5 g, thus indicating the practical impossibility for humans to stay and work on the biggest Planets of the Solar System.

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Section: Discussionmentioning

confidence: 99%

Effects of acceleration in the Gz axis on human cardiopulmonary responses to exercise

et al. 2011

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“…After 60 days in head down tilt bed rest (HDBR), the cardiovascular system is affected morphologically (e.g., myocardial atrophy, altered carotid wall thickness, venous enlargment) and the hemodynamic responses to orthostatic and exercise activities are altered Shoemaker et al 1998;Hughson et al 2004, Arbeille et al 2008bBringard et al 2010). Aerobic exercise countermeasures partially prevent muscular and cardiac atrophy and plasma volume loss Dorfman et al 2007;Trappe et al 2007), while resistive exercise alone had a limited benefit on these processes (Alkner and Tesch 2004).…”

Section: Introductionmentioning

confidence: 99%

“…Lower body negative pressure (LBNP) in association with aerobic exercise not only restores plasma volume and myocardium thickness but also reduces peripheral vascular deconditioning and orthostatic intolerance during HDBR (Guell et al 1991;Gharib et al 1992;Arbeille et al 1995;Macias et al 2007;Watenpaugh et al 2007). A nutrition countermeasure (daily amino acid supplementation) marginally maintains myocardium, but does not maintain orthostatic tolerance (Dorfman et al 2007;Guinet et al 2009;Arbeille et al 2008b).…”

Section: Introductionmentioning

confidence: 99%

Aortic, cerebral and lower limb arterial and venous response to orthostatic stress after a 60-day bedrest

Arbeille¹,

Shoemaker

Kerbeci³

et al. 2011

Eur J Appl Physiol

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The objective of this study is to assess by echography and Doppler the Cerebral (Vmca), Aortic (Vao) and Femoral (Vfem) arterial flow velocity and calf vein (Tibial, Gastrocnemius) section (Tib, Gast) during orthostatic intolerance (OI) test after a 60-day, head down tilt bed rest (HDBR). Twenty-four women (25-40 years) underwent a 60-day HDBR at -6°: eight as control (Con), eight with exercise against lower body negative pressure (Ex-Lb) and eight with nutrition supplement (Nut). Before and after (R0) HDBR, all subjects underwent a 10-min, 80° tilt followed by progressive LBNP until presyncope. After the post-HDBR Tilt + LBNP test, two groups were identified: finishers (F, n = 11) who completed the Tilt and non-finishers (NF, n = 13). A higher percentage decrease in Vao flow, higher percentage distension of Tib vein and a lack of increase in Vmca/Vfem ratio during the post-HDBR Tilt + LBNP compared to pre-HDBR were correlated to OI, but not all of these abnormal responses were present in each of the NF subjects. Abnormal responses were more frequent in Con and Nut than in Ex-Lb subjects. (1) HDBR did not affect the cardiac, arterial and venous responses to the orthostatic test to the same extent in each subject. (2) Exercise within LBNP partially preserved the cardiovascular response to Tilt, while Nutrition supplementation had no efficacy. (3) Cerebral/femoral flow ratio and aortic flow were the parameters most closely related to OI. (4) Reduction in aortic flow was not the major hemodynamic change preceding syncope.

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“…After HDBR, some studies have shown a greater reduction in CBFV with lower body negative pressure (LBNP) (38) or assuming an upright posture (21), suggesting an impairment in the ability to regulate cerebral blood flow when faced with an orthostatic stress. However, other research has found no difference in cerebrovascular responses to tilt or LBNP (3,4) or with rapid deflation of leg cuffs (29).…”

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confidence: 95%

“…Results from Earth-based analogs of spaceflight using head down-bed rest (HDBR) have revealed increases (21), decreases (2,4,14,18,32), or no changes (2,3,29,38) in supine CBFV. After HDBR, some studies have shown a greater reduction in CBFV with lower body negative pressure (LBNP) (38) or assuming an upright posture (21), suggesting an impairment in the ability to regulate cerebral blood flow when faced with an orthostatic stress.…”

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Impaired cerebrovascular autoregulation and reduced CO₂ reactivity after long duration spaceflight

Zuj

Arbeille

Shoemaker

et al. 2012

American Journal of Physiology-Heart and Circulatory Physiology

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Zuj KA, Arbeille P, Shoemaker JK, Blaber AP, Greaves DK, Xu D, Hughson RL. Impaired cerebrovascular autoregulation and reduced CO2 reactivity after long duration spaceflight. Am J Physiol Heart Circ Physiol 302: H2592-H2598, 2012. First published April 26, 2012 doi:10.1152/ajpheart.00029.2012.-Long duration habitation on the International Space Station (ISS) is associated with chronic elevations in arterial blood pressure in the brain compared with normal upright posture on Earth and elevated inspired CO2. Although results from short-duration spaceflights suggested possibly improved cerebrovascular autoregulation, animal models provided evidence of structural and functional changes in cerebral vessels that might negatively impact autoregulation with longer periods in microgravity. Seven astronauts (1 woman) spent 147 Ϯ 49 days on ISS. Preflight testing (30 -60 days before launch) was compared with postflight testing on landing day (n ϭ 4) or the morning 1 (n ϭ 2) or 2 days (n ϭ 1) after return to Earth. Arterial blood pressure at the level of the middle cerebral artery (BPMCA) and expired CO2 were monitored along with transcranial Doppler ultrasound assessment of middle cerebral artery (MCA) blood flow velocity (CBFV). Cerebrovascular resistance index was calculated as (CVRi ϭ BPMCA/CBFV). Cerebrovascular autoregulation and CO2 reactivity were assessed in a supine position from an autoregressive moving average (ARMA) model of data obtained during a test where two breaths of 10% CO2 were given four times during a 5-min period. CBFV and Doppler pulsatility index were reduced during Ϫ20 mmHg lower body negative pressure, with no differences pre-to postflight. The postflight indicator of dynamic autoregulation from the ARMA model revealed reduced gain for the CVRi response to BPMCA (P ϭ 0.017). The postflight responses to CO2 were reduced for CBFV (P ϭ 0.056) and CVRi (P ϭ 0.047). These results indicate that long duration missions on the ISS impaired dynamic cerebrovascular autoregulation and reduced cerebrovascular CO2 reactivity.transcranial Doppler ultrasound; cerebral blood flow; cerebrovascular resistance THE MICROGRAVITY environment, which causes cephalic fluid shifts with increased arterial pressure at the level of the brain relative to normal daily life on Earth (17), might cause alterations in cerebrovascular structure and function. The impact of microgravity on human cerebrovascular function has primarily been examined during and after short-duration spaceflights (2,5,8,20) with only a few measurements of cerebral blood flow velocity (CBFV) during or after long-duration flights (2, 33). During spaceflight, only modest changes in CBFV have been reported (2, 5) with small increases in cerebrovascular resistance after months in space that were speculated to reflect increased sympathetic vasoconstriction (2). Postflight CBFV in the supine posture was unchanged or slightly elevated from preflight (8,20). Postflight measurements of dynamic cerebrovascular autoregulatory indexes, reflecting vascular smooth muscl...

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Insufficient flow reduction during LBNP in both splanchnic and lower limb areas is associated with orthostatic intolerance after bedrest

Cited by 65 publications

References 40 publications

Effects of acceleration in the Gz axis on human cardiopulmonary responses to exercise

Effects of acceleration in the Gz axis on human cardiopulmonary responses to exercise

Aortic, cerebral and lower limb arterial and venous response to orthostatic stress after a 60-day bedrest

Impaired cerebrovascular autoregulation and reduced CO₂ reactivity after long duration spaceflight

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