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Arterial pressure-flow relations in the awake standing dog
The American Journal of Physiology
|November 1, 1975
Summary
This study on dogs reveals that immediately after increasing heart rate, aortic pressure and flow suggest a downstream pressure of 49 mmHg at the arteriolar level. Pulmonary circulation indicates a 9 mmHg downstream pressure at the alveolar or arteriolar level.
Area of Science:
- Cardiovascular Physiology
- Hemodynamics
- Autonomic Reflexes
Background:
- Understanding circulatory adjustments to heart rate changes is crucial for cardiovascular research.
- The role of vascular resistance and downstream pressures in immediate hemodynamic responses requires clarification.
Purpose of the Study:
- To analyze transient circulatory changes in response to increased heart rate in unanesthetized dogs.
- To investigate the underlying mechanisms of these circulatory changes, focusing on vascular resistances.
Main Methods:
- Utilized 133 trials in 6 dogs with chronically implanted monitoring devices.
- Measured heart rate, cardiac output, aortic blood pressure, and mean right atrial pressure.
- In a subset of trials, pulmonary artery pressure, left ventricular end-diastolic pressure, and left ventricular dP/dt were also recorded.
Main Results:
- Aortic pressure and flow increased within 3 seconds of heart rate pacing, suggesting an effective downstream pressure of approximately 49 mmHg at the arteriolar level before reflex activation.
- Pulmonary circulation data over 30 seconds indicated an effective downstream pressure of 9 mmHg, likely at the alveolar or pulmonary arteriolar level, independent of left ventricular end-diastolic pressure.
Conclusions:
- The immediate hemodynamic response to increased heart rate points to significant arteriolar resistance influencing systemic pressure and flow.
- Pulmonary circulation dynamics suggest a distinct downstream pressure, highlighting regional differences in vascular control and resistance mechanisms.