Feedback Control of Mean Aortic Pressure in a Dynamic Model of the Cardiovascular System

O'Leary, Daniel S.; Gm, Pantalos; Mk, Sharp

doi:10.1097/00002480-199911000-00014

Cited by 5 publications

(4 citation statements)

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“…The decrease in fluid volume induced a decrease in CO, which could partly involve lowering of blood pressure [1, 2]. CO has been demonstrated to reduce by approximately 15% from the preflight level in astronauts during sustained spaceflight [5, 6]. Fritsch-Yelle et al [7] reported that diastolic pressure and heart rate significantly decreased and that systolic pressure tended to fall during spaceflight in humans.…”

Section: Discussionmentioning

confidence: 99%

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Spaceflight Affects Postnatal Development of the Aortic Wall in Rats

Katsuda

Yamasaki

Waki

et al. 2014

BioMed Research International

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We investigated effect of microgravity environment during spaceflight on postnatal development of the rheological properties of the aorta in rats. The neonate rats were randomly divided at 7 days of age into the spaceflight, asynchronous ground control, and vivarium control groups (8 pups for one dam). The spaceflight group rats at 9 days of age were exposed to microgravity environment for 16 days. A longitudinal wall strip of the proximal descending thoracic aorta was subjected to stress-strain and stress-relaxation tests. Wall tensile force was significantly smaller in the spaceflight group than in the two control groups, whereas there were no significant differences in wall stress or incremental elastic modulus at each strain among the three groups. Wall thickness and number of smooth muscle fibers were significantly smaller in the spaceflight group than in the two control groups, but there were no significant differences in amounts of either the elastin or collagen fibers among the three groups. The decreased thickness was mainly caused by the decreased number of smooth muscle cells. Plastic deformation was observed only in the spaceflight group in the stress-strain test. A microgravity environment during spaceflight could affect postnatal development of the morphological and rheological properties of the aorta.

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Section: Discussionmentioning

confidence: 99%

“…Central venous pressure (CVP) [3, 4], cardiac output (CO) [5, 6], and arterial pressure (AP) [7, 8] have been reported to instantaneously increase after exposure to μ G and then decrease in the process of adapting to μ G environment during spaceflight in humans.…”

Section: Introductionmentioning

confidence: 99%

Spaceflight Affects Postnatal Development of the Aortic Wall in Rats

Katsuda

Yamasaki

Waki

et al. 2014

BioMed Research International

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“…The distal resistance element contained 1/4" thick porous plastic sheeting to provide linear resistance much like the natural circulation. The porous sheet was contained in a cartridge with a servo-controlled guillotine plate to adjust the peripheral resistance so that the mean outflow (aortic) pressure could be automatically regulated to 95±3 mm Hg for each test condition [29]. A 40 µm arterial filter (Medtronic, Minneapolis, MN) was incorporated downstream of the aortic flow probe to mimic the proximal aortic resistance and to filter any debris from the flow stream.…”

Section: Methodsmentioning

confidence: 99%

“…The pressure sensors were then re-exposed to the fluid loop and the heart controller turned back on as the next preload condition was created by the addition or withdrawal of fluid and regulation of afterload pressure. Details of this experiment control scheme have been reported previously [29].…”

Section: )) a Compliant Artificialmentioning

confidence: 99%

The Effect of Gravitational Acceleration on Cardiac Diastolic Function: A Biofluid Mechanical Perspective with Initial Results

Pantalos

Bennett²,

Sharp³

et al. 2005

CPB

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Echocardiographic measurements of astronaut cardiac function have documented an initial increase, followed by a progressive reduction in both left ventricular end-diastolic volume index and stroke volume with entry into microgravity (micro-G). The investigators hypothesize that the observed reduction in cardiac filling may, in part, be due to the absence of a gravitational acceleration dependent, intraventricular hydrostatic pressure difference in micro-G that exists in the ventricle in normal gravity (1-G) due to its size and anatomic orientation. This acceleration-dependent pressure difference, DeltaP(LV), between the base and the apex of the heart for the upright posture can be estimated to be 6660 dynes/cm(2) ( approximately 5 mm Hg) on Earth. DeltaP(LV) promotes cardiac diastolic filling on Earth, but is absent in micro-G. If the proposed hypothesis is correct, cardiac pumping performance would be diminished in micro-G. To test this hypothesis, ventricular function experiments were conducted in the 1-G environment using an artificial ventricle pumping on a mock circulation system with the longitudinal axis anatomically oriented for the upright posture at 45 degrees to the horizon. Additional measurements were made with the ventricle horizontally oriented to null DeltaP(LV)along the apex-base axis of the heart as would be the case for the supine posture, but resulting in a lesser hydrostatic pressure difference along the minor (anterior-posterior) axis. Comparative experiments were also conducted in the micro-G environment of orbital space flight on board the Space Shuttle. This paper reviews the use of an automated cardiovascular simulator flown on STS-85 and STS-95 as a Get Away Special payload to test this hypothesis. The simulator consisted of a pneumatically actuated, artificial ventricle connected to a closed-loop, fluid circuit with adjustable compliance and resistance elements to create physiologic pressure and flow conditions. Ventricular instrumentation included pressure transducers in the apex and base as well as immediately upstream of the inflow valve and downstream of the outflow valve, and a flow probe downstream of the outflow valve. By varying the circulating fluid volume, ventricular function could be determined for varying preload pressures at a regulated, mean afterload pressure of 95 mm Hg. This variation in preload condition permitted the construction of a ventricular function curve for the micro-G environment for comparison to the same curve for the 1-G environment. Data were collected from both missions at the upper end of the ventricular function curve. Experiment operation in the 1-G, supine orientation or in the micro-G environment eliminated the DeltaP(LV) observed in the 1-G, upright orientation. Consistent with the hypothesis, additional atrial pressure was required in micro-G to obtain stroke volumes and flow rates similar to those measured in 1-G for the upright posture. The necessary increase in atrial pressure was approximately 5 mm Hg in these experiments. In the same range ...

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Models of the Cardiovascular System

Sharp

2018

Theory and Applications of Heat Transfer in Humans

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Feedback Control of Mean Aortic Pressure in a Dynamic Model of the Cardiovascular System

Cited by 5 publications

References 0 publications

Spaceflight Affects Postnatal Development of the Aortic Wall in Rats

Spaceflight Affects Postnatal Development of the Aortic Wall in Rats

The Effect of Gravitational Acceleration on Cardiac Diastolic Function: A Biofluid Mechanical Perspective with Initial Results

Models of the Cardiovascular System

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