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Understanding Pulmonary Blood Flow & Circulation: Lectures on Respiratory Physiology

Dive deep into the mechanisms of pulmonary and systemic circulations, exploring the intricate network of alveoli, capillaries, and vessels. Learn about compression, resistance, recruitment, and distension of capillaries, as well as the effects of pressure changes on vascular resistance. Discover the Fick principle, uneven blood flow distribution, and the impact of posture, exercise, and lung volume on pulmonary circulation. Explore various models and factors affecting pulmonary blood flow and resistance, including hypoxic vasoconstriction and the evolutionary aspects of pulmonary circulation.

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Understanding Pulmonary Blood Flow & Circulation: Lectures on Respiratory Physiology

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  1. Pulmonary Blood Flow Lectures on respiratory physiology

  2. Pulmonary and systemic circulations

  3. Alveoli with capillaries

  4. Compression of capillaries

  5. Pulmonary capillary has a very thin wall

  6. Small pulmonary vein

  7. Alveolar and extra-alveolar vessels

  8. Comparison of vascular and electrical resistance Pin Pout FLOW INPUT PRESSURE – OUTPUT PRESSURE VASCULAR RESISTANCE = FLOW INPUT VOLTAGE – OUTPUT VOLTAGE ELECTRICAL RESISTANCE = CURRENT

  9. Effects of increased pressures on vascular resistance

  10. Recruitment and distension of capillaries

  11. Pulmonary capillary has a very thin wall

  12. Demonstration of recruitment

  13. Demonstration of distension

  14. Effect of lung volume on resistance

  15. Measurement of total pulmonary blood flow . Vo2 FICK PRINCIPLE - C vo2 Ca o2 . . - = - Ca Q ( C Vo2 ) o2 vo2 . . Vo2 = Q - - Ca C o2 vo2

  16. Uneven distribution of blood flow

  17. Effects of change of posture and exercise

  18. Normal distribution in isolated lung

  19. Effect of reducing pulmonary artery pressure

  20. Effect of raising pulmonary venous pressure

  21. Three zone model of distribution of blood flow

  22. Compression of capillaries

  23. Three zone model of distribution of blood flow

  24. Model of a Starling resistor

  25. Three zone model of distribution of blood flow

  26. Non-gravitational causes of uneven blood flow • Random variations in the resistance of blood vessels • Some evidence that proximal regions of an acinus receive more blood flow than distal regions • In some animals some regions of the lung have an intrinsically higher vascular resistance

  27. Effect of breathing 10% oxygen

  28. Effect of reducing the alveolar PO2

  29. Alveolar gas is very close to the wall of the artery

  30. Low alveolar PO2 causes vasoconstriction

  31. Evolutionary pressure for hypoxic pulmonary vasoconstriction • Pulmonary blood flow in the fetus is only about 15% of the cardiac output • Most of the output of the right ventricle bypasses the lung through the ductus arteriosus • The pulmonary vascular resistance is high because of hypoxic vasoconstriction in the very muscular pulmonary arteries • Immediately after birth, and pulmonary blood flow must increase dramatically • The great fall in pulmonary vascular resistance is due mainly to the release of hypoxic vasoconstriction • In addition the ductus arteriosus gradually closes

  32. Substances metabolized by the lung • Biological activation: Angiotensin I is converted to the vasoconstrictor, angiotensin II via ACE • Biological inactivation:. Examples include bradykinin, serotonin, prostaglandins E1, E2, and F2 alpha. Norepinephrine is also partially inactivated • Not affected: Examples include epinephrine, prostaglandins A1 and A2, angiotensin II and vasopressin. • Metabolized and released: Examples include the arachidonic acid metabolites - the leukotrienes, and prostaglandins. • Secreted: Immunoglobulins, particularly IgA, in bronchial mucus.

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