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Lower-body suction and cardiovascular reflexes: physiological and applied considerations
1Department of Physiology, Armed Forces Medical College, Pune.
Indian Journal of Physiology and Pharmacology
|January 1, 1990
Summary
Lower body subatmospheric pressure (LBSP) safely simulates standing by creating controlled hypovolemia. This method differentiates cardiovascular reflexes and aids in assessing autonomic function and orthostatic tolerance.
Area of Science:
- Cardiovascular Physiology
- Autonomic Nervous System Function
Background:
- Lower body subatmospheric pressure (LBSP) provides a method to elicit cardiovascular reflexes without postural changes.
- It induces controlled, non-hemorrhagic hypovolemia, simulating reduced central blood volume.
Purpose of the Study:
- To differentiate reflex cardiovascular effects from low-pressure receptor deactivation versus arterial baroreceptor deactivation.
- To evaluate LBSP's utility in aeromedical assessments and autonomic neuropathy diagnostics.
Main Methods:
- Applying graded LBSP up to the iliac crest in supine subjects.
- Monitoring cardiovascular responses including vascular resistance, heart rate, blood pressure, CVP, and cardiac output.
Main Results:
- LBSP < 30 mmHg affects low-pressure receptors, increasing limb vascular resistance without altering heart rate or blood pressure.
- LBSP > 30 mmHg affects arterial baroreceptors, causing tachycardia and altered blood pressure.
- Responses to -40 mmHg LBSP mimic postural changes from supine to standing; syncope increases above -60 mmHg.
Conclusions:
- LBSP is a valuable tool for assessing cardiovascular reflexes and autonomic function.
- It aids in evaluating orthostatic intolerance, physiological interventions, and autonomic neuropathies.
- LBSP enables safe, controlled induction of syncope for research purposes.