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Posturally induced leg vasoconstrictive responses: relationship to standing duration, impedance and volume changes
1Miami Heart Research Institute, FL 33140, USA.
Clinical Physiology (Oxford, England)
|August 26, 1998
Summary
Physiological vasoconstrictive responses in the legs are maintained during prolonged standing, confirming their diagnostic utility. Extended test durations are unlikely to provide additional diagnostic information beyond initial measurements.
Area of Science:
- Physiology
- Vascular Biology
- Diagnostic Testing
Background:
- Gravity-dependent leg posture induces vasoconstriction, used in diagnostic tests.
- The maintenance and determinants of this response over time are not well understood.
Purpose of the Study:
- To investigate the duration of leg vasoconstrictive responses to standing.
- To determine if response magnitude depends on limb volume changes.
Main Methods:
- Measured blood perfusion (laser Doppler) and below-knee volume/impedance changes in 10 healthy volunteers during 30 minutes of standing.
- Assessed initial and sustained responses.
Main Results:
- Initial perfusion decreases (ankle: 66.4%, foot: 49.3%) were fully maintained throughout sustained standing.
- Response magnitude was independent of leg volume changes.
- Impedance measurements correlated well with volume changes, indicating their utility.
Conclusions:
- Sustained vasoconstriction occurs during prolonged standing.
- Extended diagnostic test durations are unlikely to yield further diagnostic information.
- Impedance is a viable method for assessing dynamic limb volume changes.