Kawai Y, Puma SC, Hargens AR, Murthy G.
ASGSB Bull. 1992 Oct; 6: 82.
Life Science Division, NASA Ames Research Center, Moffett Field, CA.
The study was undertaken to investigate cerebral blood flow (CBF) velocity during centrifugation with and without straining. Blood flow velocities in the right middle cerebral artery were measured in 5 healthy males by transcranial Doppler ultrasonography. After control measurements in the seated position were obtained, subjects were exposed to +Gz acceleration with onset rate of 0.1 G/sec. Peripheral loss of vision (less than or equal to 60 degrees) was defined as the physiological end-point. During centrifugation without straining, mean CBF velocity decreased from 59.4 +/- 5.0 cm/sec. at 1 Gz control to 31.0 +/- 2.5 cm/sec at end-point (5.7 +/- 0.4 Gz). Mean CBF velocity correlated well with Gz force (R=0.89, p < 0.001). Subjects tolerated up to 7.3 +/- 0.6 Gz during centrifugation with straining (Valsalva maneuver). Mean CBF velocity recovered transiently by forcing the lungs against a closed glottis. At the physiological end-point, however, there was no significant difference in mean CBF velocity between the subjects with and without straining. These results suggest that the straining maneuver counteracts Gz-induced reduction of CBF velocity, which in turn increases +Gz tolerance.
Publication Types:
Keywords:
- Acceleration
- Angiography
- Animals
- Blood Circulation Time
- Blood Flow Velocity
- Brain
- Centrifugation
- Cerebrovascular Circulation
- Humans
- Male
- Oxidation-Reduction
- Ultrasonography, Doppler, Transcranial
- Valsalva Maneuver
- radiography
- ultrasonography
- NASA Center ARC
- NASA Discipline Cardiopulmonary
- NASA Discipline Number 14-10
- NASA Program Space Physiology and Countermeasures
Other ID:
UI: 102212526
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