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Local pulmonary blood flow: control and gas exchange
1Hermann Rahn Laboratory, Department of Physiology, School of Medicine and Biomedical Sciences, State University of New York at Buffalo 14214.
Respiration Physiology
|October 1, 1993
Summary
Pulmonary blood flow is significantly reduced by low oxygen and high carbon dioxide levels in the lungs. This study in sheep reveals how alveolar gas tensions influence pulmonary vascular responses and models gas exchange.
Area of Science:
- Physiology
- Pulmonary Circulation
- Respiratory Physiology
Background:
- Pulmonary vasculature exhibits local responses to changes in alveolar gas composition.
- Understanding these responses is crucial for respiratory physiology and gas exchange modeling.
Purpose of the Study:
- To investigate the local pulmonary vascular response to combined alterations in alveolar partial pressure of oxygen (PO2) and partial pressure of carbon dioxide (PCO2).
- To develop a model of gas exchange incorporating the effects of alveolar gas tensions on pulmonary blood flow.
Main Methods:
- Conscious sheep were used to study the right apical lobe (RAL) under various inspired O2-CO2-N2 mixtures.
- Pulmonary blood flow to the RAL (%QRAL) was measured by methane elimination.
- End-tidal PO2 (PETO2) and end-tidal PCO2 (PETCO2) were systematically varied.
Main Results:
- A decrease in PO2 from 100 to 50 Torr reduced local blood flow by 60% in normocapnia and 66% at 60 Torr PCO2.
- Increasing PCO2 from 40 to 60 Torr nearly halved RAL blood flow (%QRAL) across all oxygenation levels.
- The developed model predicts that alveolar gas tensions significantly influence gas exchange and pulmonary hemodynamics.
Conclusions:
- Local pulmonary blood flow is sensitive to both hypoxia and hypercapnia.
- Alveolar gas tensions play a critical role in regulating pulmonary vascular resistance.
- The study provides a model for gas exchange that accounts for local blood flow control, predicting effects on alveolar-arterial gas differences and pulmonary hypertension.
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