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Respiratory System

Respiratory System. Surah: 24 Al-Noor   Aya: 19. Recap. Function of the Pulmonary Circulation When the Left Atrial Pressure Rises as a Result of Left-Sided Heart Failure. healthy person: almost never rises above +6 mm Hg, even during the most strenuous exercise

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Respiratory System

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  1. Respiratory System

  2. Surah: 24 Al-Noor   Aya: 19

  3. Recap

  4. Function of the Pulmonary Circulation When the Left Atrial Pressure Rises as a Result of Left-Sided Heart Failure • healthy person: almost never rises above +6 mm Hg, even during the most strenuous exercise • up to about 7 mm Hg→ little effect • greater than 7 or 8 mm Hg • →increased load on the right heart • →increases the capillary pressure • →pulmonary edema (safety factors) • Length of Time Blood Stays in the Pulmonary Capillaries • 0.3 second

  5. Lecture 7

  6. Capillary Exchange of Fluid in the Lungs, and Pulmonary Interstitial Fluid Dynamics • qualitatively same as for peripheral tissues • quantitatively, important differences • Forces tending to cause movement of fluid outward from the capillaries and into the pulmonary interstitium: • Capillary pressure=7   • Interstitial fluid colloid osmotic pressure=14   • Negative interstitial fluid pressure=8     TOTAL OUTWARD FORCE=29 • Forces tending to cause absorption of fluid into the capillaries: • Plasma colloid osmotic pressure=28     TOTAL INWARD FORCE=28 MEAN FILTRATION PRESSURE=+1 • slight continual flow of fluid from the pulmonary capillaries into the interstitial spaces • pumped back to the circulation through the pulmonary lymphatic system • a small amount that evaporates in the alveoli

  7. Hydrostatic and osmotic forces at the capillary (left) and alveolar membrane (right) of the lungs

  8. Mechanism for Keeping the Alveoli "Dry • Negative Pulmonary Interstitial Pressure • pulmonary capillaries • pulmonary lymphatic system

  9. Pulmonary Edema • Mechanism : • rapid leakage of both plasma proteins and fluid out of the capillaries and into both the lung interstitial spaces and the alveoli • Any factor that causes the pulmonary interstitial fluid pressure to rise • causes • Left-sided heart failure or mitral valve disease • Damage to the pulmonary blood capillary membranes • infections such as pneumonia • noxious substances such as chlorine gas or sulfur dioxide gas

  10. Rate of fluid loss into the lung tissues when the left atrial pressure (and pulmonary capillary pressure) is increased

  11. Pulmonary Edema Safety Factor • pulmonary capillary pressure must rise from the normal level of 7 mm Hg to more than 28 mm Hg to cause pulmonary edema, giving an acute safety factor against pulmonary edema of 21 mm Hg • Safety Factor in Chronic Conditions • lymph vessels expand greatly • 40 to 45 mm Hg • Rapidity of Death in Acute Pulmonary Edema • 20 to 30 minutes • in acute left-sided heart failure

  12. Fluid in the Pleural Cavity Dynamics of fluid exchange in the intrapleural space.

  13. Pleural Effusion • "Negative Pressure" in Pleural Fluid • -7 mm Hg • at least as negative as -4 mm Hg • lymphatics • causes (1) blockage of lymphatic drainage (2) cardiac failure:↑ capillary pressures (3) ↓ plasma colloid osmotic pressure (4) infection / inflammation: breaks down the capillary membranes

  14. Objectives • Pulmonary Ventilation • Pulmonary Circulation, Pulmonary Edema, Pleural Fluid • Physical Principles of Gas Exchange; Diffusion of Oxygen and Carbon Dioxide Through the Respiratory Membrane • Transport of Oxygen and Carbon Dioxide in Blood and Tissue Fluids • Regulation of Respiration • Respiratory Insufficiency-Pathophysiology, Diagnosis, Oxygen Therapy

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