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Instantaneous stroke volume by PDE during and after constant LBNP (-50 torr)Six male subjects were exposed to -50 torr lower body negative pressure (LBNP) for 10 min while stroke volume was recorded beat by beat at regular intervals before, during and after release of LBNP. Stroke volume was calculated from the systolic velocity integral in the ascending aorta by pulsed Doppler echocardiography (PDE) and the cross sectional area of the vessel by M mode echocardiography. Changes in leg volume were recorded continuously and blood pressure was taken every minute. Stroke volume dropped by 51% of the control in the first 33 sec of LBNP and continued to decline slowly to -62% toward the end. Heart rate increased by 15% in the first 10 sec and was 22% above control at the end of exposure. The resulting cardiac output closely followed the course of stroke volume (-47% at 33 sec, -53% at 8 min) showing that the modest increase in heart rate did little to offset the drop in stroke volume. Leg volume increased markedly within the first 10 sec with a more gradual rise reaching +3.5% at the end. Upon sudden release of LBNP, leg volume dropped significantly during the first 3 sec simultaneously with an increase in stroke volume followed by a substantial decline in heart rate below the baseline.
Document ID
19810012182
Acquisition Source
Legacy CDMS
Document Type
Other
Date Acquired
August 11, 2013
Publication Date
July 1, 1980
Publication Information
Publication: Spec. Physiol. Studies in Support of Manned Space Flight
Subject Category
Aerospace Medicine
Accession Number
81N20711
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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