| Doppler measurement of cerebral and lower limb flow during a lower body negative pressure test for predicting orthostatic intolerance. | |
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MedLine Citation:
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PMID: 11758026 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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OBJECTIVE: To quantify the cardiovascular response to an orthostatic test for predicting orthostatic intolerance. METHODS: Cerebral and lower limb arterial flow and resistance were assessed by Doppler ultrasonography during lower body negative pressure (7 minutes each at -25 and -45 mm Hg). Cardiovascular deconditioning was induced by 42 days in head-down tilt at -6 degress (7 subjects) and 6-month spaceflights (10 cosmonauts). RESULTS: Orthostatic intolerance during a stand test was observed in 57% of the head-down-tilt subjects and 83% of the cosmonauts. At the lower body negative pressure after head-down tilt and during or after flight, the average cerebral flow velocity and vascular resistance did not change significantly from before head-down tilt and before flight. Conversely, there was a lack of lower limb arterial vasoconstriction (-24% from before head-down tilt and -43% from before flight; P < .01), and the cerebral-femoral flow ratio increased less (-27% from before head-down tilt and -52% from before flight; P < .01). The lack of vasoconstriction was more pronounced in intolerant subjects (-25% from before head-down tilt and -48% from before flight) compared with tolerant subjects (-22% from before head-down tilt and -14% from before flight; P > .01). Also, the lack of a cerebral-femoral flow ratio increase was more pronounced in intolerant subjects (-49% from before head-down tilt and -55% from before flight; P < .01) than in tolerant subjects (-1% from before head-down tilt and -33% from before flight; P < .01). The cerebral flow deficit at the lower body negative pressure before head-down tilt was greater than 8% in 3 of the 4 intolerant head-down-tilt subjects and less than 8% in the 3 tolerant subjects. The 3 cosmonauts who were intolerant after flight had a preflight cerebral flow deficit greater than 8%, whereas the tolerant cosmonaut had a cerebral flow deficit less than 8%. CONCLUSION: Lack of lower limb vasoconstriction and a lower cerebral-femoral flow ratio during lower body negative pressure in disadapted subjects were associated with orthostatic intolerance. A cerebral flow deficit during lower body negative pressure before disadaptation allowed measurement of the predisposition of the subjects to become intolerant. |
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Authors:
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N Tobal; J Roumy; S Herault; G Fomina; P Arbeille |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine Volume: 20 ISSN: 0278-4297 ISO Abbreviation: J Ultrasound Med Publication Date: 2001 Nov |
Date Detail:
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Created Date: 2001-12-06 Completed Date: 2002-02-22 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 8211547 Medline TA: J Ultrasound Med Country: United States |
Other Details:
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Languages: eng Pagination: 1207-17 Citation Subset: IM |
Affiliation:
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Unité de Médecine et Physiologie Spatiales, Faculté de Médecine, Centre Hospitalier Universitaire Trousseau, Tours, France. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Blood Pressure Cerebrovascular Circulation* Head-Down Tilt* Humans Leg / blood supply* Lower Body Negative Pressure* Male Predictive Value of Tests Regional Blood Flow Space Flight* Time Factors Ultrasonography, Doppler* Vascular Resistance |
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