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Ventilation/Perfusion Ratios in the Lung

Ventilation/Perfusion Ratios in the Lung. O 2 Transport in the Blood. O 2 is bound to hemoglobin (Hb) for transport in the blood Oxyhemoglobin: O 2 bound to Hb Deoxyhemoglobin: O 2 not bound to Hb. Oxyhemoglobin Dissociation Curve. O 2 -Hb Dissociation Curve: Effect of pH.

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Ventilation/Perfusion Ratios in the Lung

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  1. Ventilation/Perfusion Ratios in the Lung

  2. O2 Transport in the Blood • O2 is bound to hemoglobin (Hb) for transport in the blood • Oxyhemoglobin: O2 bound to Hb • Deoxyhemoglobin: O2 not bound to Hb

  3. Oxyhemoglobin Dissociation Curve

  4. O2-Hb Dissociation Curve: Effect of pH • Blood pH declines during heavy exercise • Results in a “rightward” shift of the curve • Bohr effect • Favors “offloading” of O2 to the tissues

  5. pH and O2-Hem Diss. Curve

  6. O2-Hb Dissociation Curve: Effect of Temperature • Increased blood temperature results in a weaker Hb-O2 bond • Rightward shift of curve • Easier “offloading” of O2 at tissues

  7. Temp. and O2-Hem Diss. Curve

  8. O2 Transport in Muscle • Myoglobin (Mb) shuttles O2 from the cell membrane to the mitochondria • Higher affinity for O2 than hemoglobin • Even at low PO2 • Allows Mb to store O2

  9. Diss. Curve - Myoglobin vs. Hemoglobin

  10. CO2 Transport in Blood • Dissolved in plasma (10%) • Bound to Hb (20%) • Bicarbonate (70%) • CO2 + H2O  H2CO3  H+ + HCO3- • Also important for buffering H+

  11. 3 Forms of CO2 Transport in Blood

  12. CO2 Exchange in Lung

  13. Ventilation and Acid-Base Balance • Blood pH is regulated in part by ventilation • An increase in ventilation causes exhalation of additional CO2 • Reduces blood PCO2 • Lowers H+ concentration

  14. Transition from Rest to Steady State

  15. Exercise in a Hot Environment • During prolonged submaximal exercise: • Ventilation tends to drift upward • Little change in PCO2 • Higher ventilation not due to increased PCO2

  16. Ventilation vs. Hot/Humid

  17. Respiratory Parameters (Elite vs. Untrained)

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