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Changes in cardiac output during sustained maximal ventilation in humans
Journal of Applied Physiology (Bethesda, Md. : 1985)
|July 1, 1987
Summary
Maximal breathing significantly increases cardiac output and oxygen consumption. This study estimates respiratory muscle blood flow during maximal ventilation, suggesting an upper limit of 3-5 L/min.
Area of Science:
- Cardiopulmonary Physiology
- Respiratory Muscle Metabolism
Background:
- Maximal sustained ventilation requires significant energy expenditure.
- Understanding respiratory muscle blood flow is crucial for assessing exercise capacity.
Purpose of the Study:
- To quantify the increase in cardiac output and oxygen consumption (VO2) from rest to maximal ventilation.
- To estimate respiratory muscle blood flow during maximal breathing.
Main Methods:
- Cardiac output and VO2 were measured using acetylene rebreathing in five subjects.
- Subjects breathed 5% CO2 during maximal ventilation to prevent hypocapnia.
- Respiratory muscle blood flow was estimated from the increase in cardiac output and calculated using the Fick equation.
Main Results:
- Cardiac output increased by 4.3 L/min during maximal ventilation (from 5.6 to 9.9 L/min).
- Oxygen consumption (VO2) increased from 312 to 723 ml/min.
- Oxygen extraction across respiratory muscles was 9.6 vol%.
Conclusions:
- Maximal sustained ventilation leads to a substantial increase in cardiac output and VO2.
- Estimated respiratory muscle blood flow during unloaded maximal ventilation is approximately 3-5 L/min.