Gas Transport - Trachte

Question 1

How is oxygen transported in the blood?

(Hint: 2 forms)

Answer 1

• Dissolved:
  
  • 0.3 mL/dL blood at P_O2 of 100 mmHg
• Associated with hemoglobin
  
  • 20 mL/dL blood at P_O2 of 100 mmHg
    
    • levels with hemoglobin of 15 mg/dL
  • This relationship is sigmoidal!

Question 2

What is the oxygen dissociation process?

Answer 2

• O₂ + Hb ⇔ HbO₂
• Maximal O₂ binding is 1.39 mL/g
  
  • (with normal hemoglobin levels)
• Maximal O₂ binding is about 20 mL/100 mL blood
• Oxygen Saturation = amount combined with Hb / maximal O₂ capacity of Hb

Question 3

How do various substances/metabolic products affect the oxygen dissociation process?

Answer 3

• Decreased hemoglobin
  
  • if Hb = 9 g/100 mL → O₂ capacity will be reduced to about 13 mL O₂/100mL blood at P_O2 of 100 mmHg
• Right shift in O₂ dissociation (decreased affinity)
  
  • decreased pH
  • increased CO₂
  • increased temperature
  • increased 2,3-diphosphoglycerate
• Left shift in O₂ dissociation (increased affinity)
  
  • increased pH
  • decreased CO
  • decreased temperature
  • decreased 2,3-DPG

Question 4

Does anemia impact P_O2?

Does anemia impact O₂ saturation?

Does anemia impact O₂ capacity?

Answer 4

• Anemia
  
  • does not impact P_O2 (based on ventilation)
  • does not impact O₂ saturation (based on Hb saturation)
  • DOES impact O₂ capacity

Question 5

How is CO₂ transported in the blood?

(Hint: 3 forms)

Answer 5

• Dissolved CO₂ (10%)
• Bicarbonate (predominant form)
  
  • Involves Carbonic Anhydrase (
    
    • HCO₃^- leaves RBC, H⁺ stays, Cl^- shifts into RBC to balance charge
• Carbamino compounds (5%)
  
  • CO₂ can bind to Hb

Question 6

What are the typical causes of respiratory acidosis?

Answer 6

• Hypoventilation
• Ventilation-perfusion mismatch

Question 7

What is the carbon dioxide dissociation process compared to O₂ dissociation?

Answer 7

• More linear, Much steeper
  
  • Blood can carry more CO₂ than O₂
  • O₂ saturation significantly affects this curve
    
    • (O₂ shifts if to the right)

Question 8

What could potentially cause hypoxia due to low O₂ delivery?

Answer 8

• Low arterial P_O2
• Anemia
• Tissue blood flow disruption
  
  • embolism, thrombus, etc.
• Poison (cyanide)