Related Experiment Videos
Breathing affects venous return from legs in humans.
Summary
Inspiration typically increases blood flow to the heart. However, this study found that leg venous return actually decreases during inspiration due to increased abdominal pressure, especially with diaphragmatic breathing.
Area of Science:
- Cardiovascular Physiology
- Respiratory Physiology
Background:
- Venous return to the heart is conventionally thought to increase during inspiration.
- This increase is attributed to decreased intrathoracic pressure and splanchnic vein compression by the diaphragm.
Purpose of the Study:
- To test the hypothesis that venous return from the legs decreases during inspiration in humans.
- To investigate the role of increased abdominal pressure in this phenomenon.
Main Methods:
- Ten healthy subjects were studied in a recumbent position.
- Femoral vein blood flow was measured using an ultrasonic flow recorder (Doppler effect).
- Subjects performed various respiratory maneuvers, including quiet inspiration and diaphragmatic breathing.
Main Results:
- Quiet inspiration led to a significant average fall (65%) in leg venous blood flow.
- The decrease in flow was proportional to the rise in abdominal pressure and diaphragmatic contribution to breathing.
- Pure diaphragmatic breathing caused complete cessation of femoral venous blood flow.
Conclusions:
- Inspiration can decrease, rather than increase, venous return from the legs in humans.
- Increased abdominal pressure, particularly from diaphragmatic contraction, impedes leg venous return.
- Diaphragmatic contraction is not essential for impeding leg venous return during inspiration.