Hemodynamic and neurohormonal responses to extreme orthostatic stress in physically fit young adults

Grasser, Erik Konrad; Goswami, Nandu; Rössler, Andreas; Vrecko, Karoline; Hinghofer‐Szalkay, Helmut

doi:10.1016/j.actaastro.2008.11.002

Cited by 33 publications

(32 citation statements)

References 35 publications

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“…Postural reflexes occur because arterial/venous hydrostatic indifference locations are below those of corresponding baroreceptors. Increased sympathetic activity, positive chronotropic and inotropic effects, and an instant rise in blood norepinephrine, followed by a multitude of endocrine changes that are aimed at stabilizing central blood volume (Sander-Jensen et al 1986;Kamegai et al 1992;Hinghofer-Szalkay et al 1996Jacob et al 1998;Rössler et al 1999;Laszlo et al 2001;Grasser et al 2009). …”

Section: Baroreflex Patternmentioning

confidence: 94%

Gravity, the hydrostatic indifference concept and the cardiovascular system

Hinghofer‐Szalkay

2010

Eur J Appl Physiol

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Gravity, like any acceleration, causes a hydrostatic pressure gradient in fluid-filled bodily compartments. At a force of 1G, this pressure gradient amounts to 10 kPa/m. Postural changes alter the distribution of hydrostatic pressure patterns according to the body's alignment to the acceleration field. At a certain location--referred to as hydrostatically indifferent--within any given fluid compartment, pressure remains constant during a given change of position relative to the acceleration force acting upon the body. At this specific location, there is probably little change in vessel volume, wall tension, and the balance of Starling forces after a positional manoeuvre. In terms of cardiac function, this is important because arterial and venous hydrostatic indifference locations determine postural cardiac preload and afterload changes. Baroreceptors pick up pressure signals that depend on their respective distance to hydrostatic indifference locations with any change of body position. Vascular shape, filling volume, and compliance, as well as temperature, nervous and endocrine factors, drugs, and time all influence hydrostatic indifference locations. This paper reviews the physiology of pressure gradients in the cardiovascular system that are operational in a gravitational/acceleration field, offers a broadened hydrostatic indifference concept, and discusses implications that are relevant in physiological and clinical terms.

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Section: Baroreflex Patternmentioning

confidence: 94%

Gravity, the hydrostatic indifference concept and the cardiovascular system

Hinghofer‐Szalkay

2010

Eur J Appl Physiol

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“…Using typical cardiovascular changes during orthostatic loading from previous studies [18][19][20], error probability (a) of 0.05, power (1Àb) of 0.80 and considering an average effect size (d) of 0.5, we estimated number of subjects required to be 15.…”

Section: Analysis Of Datamentioning

confidence: 99%

Does mental arithmetic before head up tilt have an effect on the orthostatic cardiovascular and hormonal responses?

et al. 2011

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Passive head up tilt (HUT) and mental arithmetic (MA) are commonly used for providing mental and orthostatic challenges, respectively. In animal experiments, even a single exposure to a stressor has been shown to modify the response to subsequent stress stimulus. We investigated whether MA applied before HUT elicits synergistic responses in orthostatic heart rate (HR), cardiac output (CO), heart rate variability and arterial blood pressure. The 15 healthy young males were subjected to two randomized protocols: (a) HUT and (b) HUT preceded by MA, with sessions randomized and Z2 weeks apart. Beat to beat continuous hemodynamic variables were measured and saliva samples taken for hormonal assay. HUT alone increased HR from 5977 (baseline) to 80710 bpm (mean7SD) and mean blood pressure (MBP) from 88710 to 91714 mmHg. HUT results after MA were not different from those with HUT alone. The activity of alpha amylase showed differences during the experiments irrespective of the protocols. We conclude that mental challenge does not affect orthostatic cardiovascular responses when applied before; the timing of mental loading seems to be critical if it is intended to alter cardiovascular responses to upright standing.

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“…Using typical cardiovascular changes during orthostatic loading from previous studies (Gao et al, 2008;Grasser et al, 2009;HinghoferSzalkay et al, 2008), error probability (α) of 0.05 and power (1−ß) of 0.80 we estimated the number of participants required to be 15.…”

Section: Sample Size and Data Analysismentioning

confidence: 99%

Time course of cardiovascular responses induced by mental and orthostatic challenges

Lackner

Goswami

Papousek

et al. 2010

International Journal of Psychophysiology

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Cardiovascular responses to single stressors diminish over time. Interaction of different stressors influencing hemodynamic variables, indicative of stress-induced reactivity and physiological responses are, however, poorly understood. We investigated time course of mental (using mental arithmetic, MA) and orthostatic (using head up tilt, HUT) challenges induced responses in 16 males. Three protocols were used: HUT, MA and MA + HUT, with sessions randomized and two weeks apart. Hemodynamic responses were compared for 30 s epochs of stress application (stress T1 , stress T2 …). Compared to baseline, HUT, HUT + MA and MA applications affected heart rate (HR) (+ 15.1 ± 8.0 bpm, + 20.0 ± 9.2 bpm, + 11.9 ± 7.2 bpm, all p's b .001, respectively) and stroke volume (SV) (− 22.3 ± 8.1 ml, − 22.0 ± 10.4 ml, − 7.6 ± 8.7 ml, all p's b .001, respectively). HUT and MA + HUT induced HR increases were higher in stress T2 compared to stress T1 (p b .05) and reached maximum at stress T2 . HUT and MA + HUT further reduced SV in stress T2 as compared to stress T1 (p b .001); lowest SV was in stress T2 . Mean arterial pressure reached its minimum in stress T1 during HUT and MA + HUT (− 6.0 ± 8.5 mm Hg, p b .001, − 4.4 ± 9.7 mm Hg, p b .01, respectively) but increased in MA (+ 4.3 ± 3.7 mm Hg, p b .01). Combination of MA + HUT resulted in different time courses of blood pressure responses as compared to HUT alone. We conclude that application of single or combined stress challenges lead to stressor-and time dependent-initial changes in cardiovascular responses. Our findings provide novel insights regarding the duration a stressor must be applied to elicit maximal cardiovascular responses.

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Hemodynamic and neurohormonal responses to extreme orthostatic stress in physically fit young adults

Cited by 33 publications

References 35 publications

Gravity, the hydrostatic indifference concept and the cardiovascular system

Gravity, the hydrostatic indifference concept and the cardiovascular system

Does mental arithmetic before head up tilt have an effect on the orthostatic cardiovascular and hormonal responses?

Time course of cardiovascular responses induced by mental and orthostatic challenges

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