Lower body negative pressure: the second manned Skylab mission

Area of Science:

• Space medicine
• Human physiology
• Cardiovascular research

Background:

• Astronauts experience physiological changes in microgravity.
• Orthostatic intolerance is a common issue post-spaceflight.
• Previous Skylab missions provided insights into these adaptations.

Purpose of the Study:

• To evaluate orthostatic tolerance in Skylab 3 astronauts.
• To assess the effects of lower body negative pressure (LBNP) stress.
• To compare inflight and postflight physiological responses.

Main Methods:

• Utilized lower body negative pressure (LBNP) stress tests.
• Conducted orthostatic evaluations inflight and postflight.
• Monitored heart rate, pulse pressure, and calf size/leg volume.

Main Results:

• Elevated heart rates and decreased pulse pressure during LBNP indicated lowered orthostatic tolerance.
• Significant headward fluid shifts were observed, shown by reduced calf size and leg volume.
• Inflight calf volume changes during LBNP differed from pre/postflight responses.

Conclusions:

• Skylab 3 findings support hypotheses from Skylab 2 regarding fluid shifts and orthostatic intolerance.
• Physiological responses during LBNP stress highlight cardiovascular deconditioning.
• Further data from longer missions are needed to fully clarify spaceflight-induced adaptations.