Air plethysmography: an alternative method for assessing peripheral circulatory adaptations during spaceflights

Louisy, F.; Cauquil, D.; André-Deshays, C.; P, Schroiff; Lazerges, Michel; Lafaye, Catherine; Camus, Anne-Lise; Fomina, G

doi:10.1007/s004210100426

Cited by 9 publications

(15 citation statements)

References 3 publications

(8 reference statements)

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“…Because the latter value was measured during an actual postflight stand test, it provides the most relevant estimate of loss rate for the current simulations. This loss rate is substantially lower than the inflight rate of Louisy et al 27 Because of the small number of samples in both cases, one can only speculate whether the differences are due to individual variations, differences in the measurement protocol or changes in capillary filtration between the inflight and postflight periods.…”

Section: The Potential Role Of Capillary Transportmentioning

confidence: 82%

“…27 Baisch et al 3 confirm that inflight capillary transport measured by thigh and calf impedance changes in response to graded lower body negative pressure (LBNP) is significantly elevated compared to preflight and two days postflight. Postflight capillary transport during stand tests was elevated to nearly three times the preflight value in one Gemini-7 astronaut 10 ( Fig.…”

Section: The Potential Role Of Capillary Transportmentioning

confidence: 87%

“…The next transition to 1G standing incorporates a decrease in intrathoracic pressure to -6.3 mmHg, as well as addition of hydrostatic pressure in all compartments. Then additional cases were simulated with incremental 40 mL/min net reductions in circulating volume (from all capillary filtration and resorption mechanisms) until cerebral arterial pressure dropped below the threshold for consciousness (25)(26)(27)(28)(29)(30).…”

Section: Simulated Stand Testmentioning

confidence: 99%

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Evaluation of Mechanisms of Postflight Orthostatic Intolerance with a Simple Cardiovascular System Model

Broskey

Sharp

2007

Ann Biomed Eng

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A significant fraction of astronauts experience postflight orthostatic intolerance (POI) during 10-min stand tests conducted on landing day. The average time that nonfinishers can stand is about 7 min. This phenomenon, including the delay in occurrence of presyncope, was studied with a five-compartment model of the cardiovascular system incorporating compartments for the heart/lungs, systemic arteries and cephalic, central, and caudal veins. The model included 28 independent parameters, including factors characterizing cardiac performance, vascular resistance, intrathoracic pressure, nonlinear venous compliance and circulating blood volume, and 13 dependent parameters, including cardiac output and cardiac and vascular compartment pressures and volumes. First, a sensitivity analysis of hemodynamic indicators of presyncope to independent parameters was performed. Results demonstrated that both cardiac output and arterial pressure were most sensitive to volume-related parameters, particularly total blood volume, and less sensitive to peripheral resistance. Next, a simulated postflight stand test confirmed that fluid loss due to capillary filtration, particularly from the caudal region where transmural pressure is high during standing, is a plausible mechanism of POI that also explains the delayed onset of symptoms in most astronauts. An accumulated drop in arterial pressure sufficient to compromise cerebral perfusion and, therefore, cause syncope was reached in about 7 min with a fluid loss of 280 mL. Finally, additional simulations showed that a 75% increase in peripheral resistance, similar to finishers of stand tests, was insufficient to overcome the loss of circulating fluid associated with capillary filtration, and extended the time that the modeled astronaut could stand by only about 1 min. It is therefore concluded that capillary filtration may play a key role in producing POI and that development of countermeasures should perhaps focus on reducing postflight capillary permeability or on stimulating volume-compensating mechanisms.

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Section: The Potential Role Of Capillary Transportmentioning

confidence: 82%

Section: The Potential Role Of Capillary Transportmentioning

confidence: 87%

Section: Simulated Stand Testmentioning

confidence: 99%

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Evaluation of Mechanisms of Postflight Orthostatic Intolerance with a Simple Cardiovascular System Model

Broskey

Sharp

2007

Ann Biomed Eng

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“…This may be due to the fact that direct measurement of vein compliance in humans is still difficult. It can in fact only be estimated indirectly by plethysmography on the basis of changes in calf volume (Convertino et al 1988, 1989 b ; Louisy et al 1997, 2001). This method takes into account the main and secondary changes in both calf vein cross‐sectional area (CSA) and tissue volume, depending on tissue liquid filtration.…”

mentioning

confidence: 99%

Calf venous volume during stand‐test after a 90‐day bed‐rest study with or without exercise countermeasure

Chantemèle

Pascaud

Custaud

et al. 2004

The Journal of Physiology

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The objectives to determine both the contribution to orthostatic intolerance (OI) of calf venous volume during a stand-test, and the effects of a combined eccentric-concentric resistance exercise countermeasure on both vein response to orthostatic test and OI, after 90-day head-down tilt bed-rest (HDT). The subjects consisted of a control group (Co-gr, n = 9) and an exercise countermeasure group (CM-gr, n = 9). Calf volume and vein cross-sectional area (CSA) were assessed by plethysmography and echography during pre-and post-HDT stand-tests. From supine to standing (post-HDT), the tibial and gastronemius vein CSA increased significantly in intolerant subjects (tibial vein, +122% from pre-HDT; gastronemius veins, +145%; P < 0.05) whereas it did not in tolerant subjects. Intolerant subjects tended to have a higher increase in calf filling volume than tolerant subjects, in both sitting and standing positions. The countermeasure did not reduce OI. Absolute calf volume decreased similarly in both groups. Tibial and gastrocnemius vein CSA at rest did not change during HDT in either group. During the post-HDT stand-test, the calf filling volume increased more in the CM-gr than in the Co-gr both in the sitting (+1.3 ± 5.1%, vs. -7.3 ± 4.3%; P < 0.05) and the standing positions (+56.1 ± 23.7% vs. +1.6 ± 9.6%; P < 0.05). The volume ejected by the muscle venous pump increased only in the CM-gr (+38.3 ± 21.8%). This study showed that intolerant subjects had a higher increase in vein CSA in the standing position and a tendency to present a higher calf filling volume in the sitting and standing positions. It also showed that a combined eccentric-concentric resistance exercise countermeasure had no effects on either post-HDT OI or on the venous parameters related to it.

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“…Therefore, the two methods give quantitatively different, but qualitatively identical information. 113 Both methods require considerable patient cooperation. Inconsistency in performing exercise, maintaining position, and distributing weight between the legs contributes significantly to variability of results.…”

Section: Chronic Venous Diseasementioning

confidence: 99%

The hemodynamics and diagnosis of venous disease

Meissner

Moneta

Burnand

et al. 2007

Journal of Vascular Surgery

313

233

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The venous system is, in many respects, more complex than the arterial system and a thorough understanding of venous anatomy, pathophysiology, and available diagnostic tests is required in the management of acute and chronic venous disorders. The venous system develops through several stages, which may be associated with a number of development anomalies. A thorough knowledge of lower extremity venous anatomy, anatomic variants, and the recently updated nomenclature is required of all venous practitioners. Effective venous return from the lower extremities requires the interaction of the heart, a pressure gradient, the peripheral muscle pumps of the leg, and competent venous valves. In the absence of pathology, this system functions to reduce venous pressure from approximately 100 mm Hg to a mean of 22 mm Hg within a few steps. The severe manifestations of chronic venous insufficiency result from ambulatory venous hypertension, or a failure to reduce venous pressure with exercise. Although the precise mechanism remains unclear, venous hypertension is thought to induce the associated skin changes through a number of inflammatory mechanisms. Several diagnostic tests are available for the evaluation of acute and chronic venous disease. Although venous duplex ultrasonography has become the standard for detection of acute deep venous thrombosis, adjuvant modalities such as contrast, computed tomographic, and magnetic resonance venography have an increasing role. Duplex ultrasonography is also the most useful test for detecting and localizing chronic venous obstruction and valvular incompetence. However, it provides relatively little quantitative hemodynamic information and is often combined with measurements of hemodynamic severity determined by a number of plethysmographic methods. Finally, critical assessment of venous treatment modalities requires an understanding of the objective clinical outcome and quality of life instruments available.

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Air plethysmography: an alternative method for assessing peripheral circulatory adaptations during spaceflights

Cited by 9 publications

References 3 publications

Evaluation of Mechanisms of Postflight Orthostatic Intolerance with a Simple Cardiovascular System Model

Evaluation of Mechanisms of Postflight Orthostatic Intolerance with a Simple Cardiovascular System Model

Calf venous volume during stand‐test after a 90‐day bed‐rest study with or without exercise countermeasure

The hemodynamics and diagnosis of venous disease

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