Doppler evaluation of cardiac filling and ejection properties in humans during parabolic flight

Johns, Joseph P.; Vernalis, Marina; Karemaker, John M.; Latham, R. D.

doi:10.1152/jappl.1994.76.6.2621

Cited by 23 publications

(21 citation statements)

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“…While meanRR is different between standing and supine subjects in normogravity and hypergravity, these differences disappear in microgravity. Johns et al (1994) found no differences in the supine position for cardiac filling and heart rate during different phases of parabolic flight suggesting that the underlying autonomic tone was maintained.…”

Section: Discussionmentioning

confidence: 77%

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Parasympathetic heart rate modulation during parabolic flights

Beckers¹,

Seps²,

Ramaekers

et al. 2003

Eur J Appl Physiol

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During parabolic flight short periods of microgravity and hypergravity are created. These changes influence cardiovascular function differently according to posture. During the 29th parabolic flight campaign of the European Space Agency (ESA), the electrocardiogram (ECG) was recorded continuously in seven healthy volunteers in two positions (standing and supine). Five different phases were differentiated: 1 g (1 g=9.81 m/s(2)) before and after each parabola, 1.8 g at the ascending leg of the parabola (hypergravity), 0 g at the apex, 1.6 g at the descending leg (hypergravity). We assessed heart rate variability (HRV) by indices of temporal analysis [mean RR interval (meanRR), the standard deviation of the intervals (SDRR), and the square root of the mean squared differences of successive intervals (rMSSD) and coefficient of variation (CV)]. In the supine position no significant differences were shown between different gravity phases for all HRV indices. In the standing position the 0 g phase showed a tendency towards higher values of meanRR compared to the control and to the other phases ( p=NS). SDRR, rMSSD and CV were significantly higher compared to control ( p<0.05). Significantly higher values for meanRR in the supine position at 1 g and hypergravity ( p<0.05) were found when compared to standing. SDRR was significantly higher at 0 g in the standing position compared to supine [95 (44) ms vs. 50 (15) ms; p<0.05] and lower in other phases. rMSSD and CV showed the same trend ( p=NS). We confirm that, during parabolic flights, position matters for cardiovascular measurements. Time domain indices of HRV during different gravity phases showed: (1) higher vagal modulation of the autonomic nervous system in microgravity, when compared with normo- or hypergravity in standing subjects; and (2) no differences in supine subjects between different g phases.

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Section: Discussionmentioning

confidence: 77%

“…During microgravity the central blood volume increased, which caused accumulation of the blood into the head and thorax (Johns et al 1994).…”

Section: Discussionmentioning

confidence: 99%

Parasympathetic heart rate modulation during parabolic flights

Beckers¹,

Seps²,

Ramaekers

et al. 2003

Eur J Appl Physiol

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“…However, these changes are not accompanied by an increase in central venous pressure or AP. Buckey et al [5] and Foldager et al [6] measured central venous pressure during space flight, and found that it promptly dropped on entry into G. Despite the decrease in central venous pressure, the left atrial diameter, end-diastolic left ventricular volume, and cardiac output increase during G [5,7,8]. Thus, the central venous pressure might not reflect the cardiac filling pressure during exposure to G. To understand this discrepancy, the TP has to be considered.…”

Section: Discussionmentioning

confidence: 99%

Relationship between Transmural Pressure and Aortic Diameter during Free Drop-Induced Microgravity in Anesthetized Rats

Morita

Fujiki²,

Gotoh³

et al. 2003

JJP

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Recently, we have demonstrated that acute microgravity (G) induced by freefall elicits a decrease in renal sympathetic nerve activity via stimulation of the sinoaortic baroreceptors and cardiopulmonary receptors [1][2][3]. Afferent nerve activity from aortic baroreceptors is increased by G, but indicators of stimulation of aortic and cardiopulmonary receptors (i.e., the aortic pressure (AP) and central venous pressure) do not increase [3]. To understand this discrepancy, it should be noted that intrathoracic pressure (ITP) is decreased by G, resulting in an increase in the calculated transmural pressure (TPϭAPϪITP) of the aortic wall [3]. Thus, it is possible that the increased TP stretches the aortic wall, and then stimulates the aortic baroreceptor. To examine this possibility, the AP, ITP, and aortic diameter (AD) were simultaneously measured, and the relationship between AD and TP examined during 1 G and G. MethodsThe experiments were performed on male SpragueDawley rats weighing 320-360 g (nϭ6). The animals were maintained in accordance with the "Guiding Principles for Care and Use of Animals in the Field of Physiological Science" of the Physiological Society of Japan.Two weeks before the experiment, the rats were anesthetized with pentobarbital sodium (50 mg/kg b.w., I.P.) and a telemetry transmitter probe (TA11PA-C40, Data Science International, St. Paul, MN, USA) was implanted to measure the AP. Using midline laparotomy, a segment of the abdominal aorta just below the renal arteries was isolated from the surrounding tissue and the tip of the telemetry transmitter probe was inserted. The transmitter was sutured into the abdominal wall and the incision closed. The rats were given penicillin intramuscularly for 3 d and monitored to ensure that food and water intake had returned to presurgical levels. Japanese Journal of Physiology, 53, 151-155, 2003 Key words: freefall, aortic diameter, transmural pressure, arterial pressure, intrathoracic pressure. Abstract:To test the hypothesis that the aortic wall is stretched without increasing aortic pressure (AP) during microgravity (G), the AP, intrathoracic pressure (ITP), and aortic diameter (AD) were measured in anesthetized SpragueDawley rats during 4.5 s of G produced by freefall. A smooth and immediate reduction in gravity (G) occurred during freefall, G being achieved 100 ms after the start of the drop. Acute G elicited an immediate increase in AD, which was not accompanied by an increase in AP. However, the ITP decreased during G resulted in an increase in the calculated transmural pressure (TPϭAPϪITP) of the aortic wall. A simple linear regression analysis showed that the slopes of the plot of AP vs.

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“…in fact, as a consequence of changes in hydrostatic pressure gradients in a standing position, acute variations in gravity induce dramatic fluid shifts from the lower extremities of the body towards the head and thorax, altering central filling volumes and pressures and resulting in significant cardiovascular effects (BAILLIART et al, 1998;LATHERS et al, 1989;MUKAI et al, 1994;NORSK et al, 1987). These modifications, together with changes in the sympathetic activity (heart rate and inotropic status), influence LV dimensions and function (JOHNS et al, 1994).…”

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confidence: 99%

Quantification of left ventricular modification in weightlessness conditions from the spatio-temporal analysis of 2D echocardiographic images

Corsi

Lamberti

Cerutti

et al. 2004

Med. Biol. Eng. Comput.

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Two-dimensional echocardiography (2DE) performed during flights with a parabolic trajectory to simulate weightlessness provides a unique means to study left ventricular (LV) modifications to prevent post-flight orthostatic intolerance in astronauts. However, conventional analysis of 2DE is based on manual tracings and depends on experience. Accordingly, the aim was objectively to quantify, from 2DE images, the LV modifications related to different gravity levels, by applying a semi-automated level-set border detection technique. The algorithm validation was performed by the comparison of manual tracing results, obtained by two independent observers with 20 images, with the semi-automated measurements. To quantify LV modifications, three consecutive cardiac cycles were analysed for each gravity phase (1 Gz, 1.8 Gz, 0 Gz). The level-set procedure was applied frame-by-frame to detect the LV endocardial contours and obtain LV area against time curves, from which end-diastolic (EDA) and end-systolic (ESA) areas were computed and averaged to compensate for respiratory variations. Linear regression (y = 0.91x + 1.47, r = 0.99, SEE:0.80cm2) and Bland-Altman analysis (bias = -0.58 cm2, 95% limits of agreement= +/- 2.14cm2) showed excellent correlation between the semi-automatic and manually traced values. Inter-observer variability was 5.4%, and the inter-technique variability was 4.1%. Modifications in LV dimensions during the parabola were found: compared with 1 Gz values, EDA and ESA were significantly reduced at 1.8 Gz by 8.8 +/- 5.5% and 12.1 +/- 10.1%, respectively, whereas, during 0 Gz, EDA and ESA increased by 13.3 +/- 7.3% and 11.6 +/- 5.1%, respectively, owing to abrupt changes in venous return. The proposed method resulted in fast and reliable estimations of LV dimensions, whose changes caused by different gravity conditions were objectively quantified.

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Doppler evaluation of cardiac filling and ejection properties in humans during parabolic flight

Cited by 23 publications

References 0 publications

Parasympathetic heart rate modulation during parabolic flights

Parasympathetic heart rate modulation during parabolic flights

Relationship between Transmural Pressure and Aortic Diameter during Free Drop-Induced Microgravity in Anesthetized Rats

Quantification of left ventricular modification in weightlessness conditions from the spatio-temporal analysis of 2D echocardiographic images

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