UB Research In Space Shows How Astronauts' Bodies Regulate Blood Pressure In Adjusting to Zero Gravity The Longer The Space Flight, The More Extended Astronauts' Adjustment Period On Return

BUFFALO, N.Y. -- Results of two NASA Space Lab 2 research projects on cardiovascular functioning and deconditioning in microgravity, designed by scientists from the University at Buffalo, have confirmed that blood pressure in flight is regulated by a decrease in vascular resistance in response to an increase in cardiac output induced by microgravity.

This phenomenon was first observed in UB research conducted on Space Lab 1.

Findings in the new studies also showed that the ability of astronauts to perform work when they returned to Earth, as measured by performance on a specific physical-exercise regimen, was decreased, and that there was a relationship between the ability to perform work and time spent in space.

Astronauts on Space Lab 2, who were in flight for 15 days, performed less well upon their return to Earth and remained limited longer than their counterparts on Space Lab 1, who were subjected to zero gravity for nine days.

Both in zero gravity and in readjusting to Earth’s gravity, the astronauts' bodies were able to regulate their blood pressure by expanding or constricting their blood vessels in the presence of increased cardiac output, the results showed, a phenomenon not observed prior to the two UB Space Lab experiments. The experiments and equipment used on both Space Lab experiments were designed by Leon E. Farhi, M.D., UB Distinguished Professor of Physiology.

Barbara E. Shykoff, Ph.D., UB research assistant professor of physiology and a lead researcher on the studies, presented the results of the UB Space Lab studies at a one-day NASA symposium in San Francisco on Sunday, Oct. 23, following a meeting of the American Society for Gravity and Space Biology.

UB's Space Lab 2 findings have resulted in a new three-year, $600,000 grant to the university from NASA to study the physiological mechanisms behind this observed cardiovascular regulatory phenomenon. Researchers will conduct the research at UB under simulated zero-gravity conditions.

“If we find something interesting through these Earth-bound experiments,” said Farhi, “we will go back to NASA for another in-flight experiment.”

The UB studies report data collected from experiments involving six astronauts, three from each flight. Measurements of cardiac output, heart rate, blood pressure, oxygen consumption and other cardiovascular variables were collected at five intervals during the six months prior to the flight and at five points during each mission. Measurements were taken while the astronauts were at rest and while they exercised on a cycle ergometer.

Earthbound research on cardiovascular functioning in simulated weightlessness has shown that when gravity is eliminated, the heart pumps more blood initially, which requires an increase in blood pressure, but the body eventually adjusts to this increased output and brings pressure back to normal by eliminating some blood plasma through urine.

However, results from the first mission, and now the second, showed that during space flight, the cardiovascular system regained its balance by readjusting the vascular tone, and that both blood pressure and blood volume remained stable.

Space Lab 2 was launched Oct. 14, 1993, and remained in space for 15 days.

UB researchers involved in the project, in addition to Farhi and Shykoff, were Christopher Eisenhart; Richard Morin; Albert J. Olszowka, M.D.; David R. Pendergast, Ph.D., and Mary Ann Rokitka, Ph.D.