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Cardiovascular changes during and after different LBNP levels in men
Z László1, A Rössler, H G Hinghofer-Szalkay
1Department of Physiology, School of Medicine, Karl-Franzens University, Graz, Austria.
Aviation, Space, and Environmental Medicine
|February 6, 1998
Summary
Lower body negative pressure (LBNP) up to -65 mm Hg alters cardiovascular function, decreasing stroke volume index and increasing heart rate. Post-LBNP, heart rate drops significantly, indicating a modified cardiovascular state.
Area of Science:
- Cardiovascular Physiology
- Hemodynamics
- Biomedical Engineering
Background:
- Lower body negative pressure (LBNP) simulates microgravity effects on the cardiovascular system.
- Understanding hemodynamic responses to LBNP is crucial for spaceflight and clinical applications.
Purpose of the Study:
- To quantify hemodynamic and thoracic impedance (TI) changes across four LBNP levels (-15 to -65 mm Hg).
- To assess cardiovascular responses during and after simulated orthostasis.
Main Methods:
- Seven healthy men were subjected to LBNP at -15, -35, -55, and -65 mm Hg for 30 minutes each.
- Hemodynamic parameters including thoracic impedance (TI), stroke volume index (SVI), cardiac index, mean arterial pressure (MAP), and heart rate were monitored.
- Measurements were taken before (pre-LBNP), during, and after (post-LBNP) LBNP application, with a rest control (LBNP-0).
Main Results:
- LBNP increased thoracic impedance, indicating reduced thoracic fluid volume.
- Stroke volume index (SVI) and cardiac index progressively decreased with increasing LBNP intensity.
- Heart rate increased significantly with higher LBNP levels and exhibited post-LBNP bradycardia.
- Mean arterial pressure (MAP) remained stable at lower LBNP levels but increased at -55 and -65 mm Hg.
Conclusions:
- Different LBNP levels elicit distinct cardiovascular responses and dose-dependent patterns.
- Simulated orthostasis via LBNP up to -65 mm Hg did not induce hypotension in healthy subjects.
- Post-LBNP bradycardia and elevated peripheral resistance suggest a sustained alteration in cardiovascular state.