B3L5 O2 and CO2 transport

How is oxygen transported throughout the body?

1. Dissolved in plasma (~1.5% of O₂)

2. Bound to hemoglobin (~98.5% of O₂)

How do you calculate how much the total O₂ content?

Add the O2 dissolved in plasma + O2 bound to hemoglobin

How do you calculate O2 dissolved in plasma in arteries?

Solubility constant x pressure

• ((0.003 mL O₂ / 100 mL blood) / 1 mmHg) x 90 mmHg = 0.27 mL O2/100 mL blood

  • 90 mmHg because that is the PO2 in the arteries

How do you calculate O2 bound to hemoglobin in arteries?

amount of O2 per Hb (constant) x g of Hb x % saturation

• (1.34 mL O2/1g Hb) x 15 g Hb x 98% = 19.7 mL O2/100 mL blood

Describe the O₂/hemoglobin saturation curve

Describes the binding affinity of oxygen to hemoglobin relative to the PO₂ in the body

What does it mean for the saturation/PO2 saturation curve to move left or right?

LEFT: Hb has a higher affinity/holds on more tightly to O2 (less O2 to the muscles)

RIGHT: Hb has a lower affinity to O2/lets go more easily (more O2 to the muscles)

What conditions would affect the saturation curve left/right?

LEFT:

• low temp, low CO2, high pH

RIGHT:

• high temp, high CO2, low pH

Describe PO2 relative to exercise intensity in the alveoli and in the arteries?

Alveolar and arterial PO2 will plateau and then increase with exercise intensity because you are taking in more oxygen per breath

Describe PAO2

PAO2 is proportional to alveolar ventilation and inversely proportional to oxygen consumption

Describe the content of oxygen in the arteries and veins relative to exercise intensity

Arterial O2 content does plateaus because Hb is fully saturated and cannot increase any more

Venous O2 content decreases because that oxygen is being used up by the tissues

What is extraction?

The different in CaO2 and CvO2

What is the exception to the rule that the CaO2 will not decrease?

EIAH (exercise-induced arterial hypoxemia)

• Highly endurance-trained female athletes will experience a very short transit time that does not allow the blood to equilibrate with alveolar PO2 and therefore her blood will have less oxygen

  • She does compensate with an increased cardiac output

How is CO₂ transported throughout the body?

1. Dissolved in plasma (~7%)

2. Bound to carbamino compounds, such as carbaminohemoglobin (~23%)

3. Carried as bicarbonate ions (~70%)

What is the carbonic anhydrase rxn?

CO₂ + H₂O → H₂CO₃ → H⁺ + HCO₃^-

T/F: Only the O2/CO2 dissolved in plasma contributes to the PO2/PCO2

True

What is the chloride shift?

The passage of Cl- ions from plasma into the RBCs in exchange for HCO₃^- for loading and unloading of CO₂

Describe the CO2 content relative to PCO2 graph

• Two lines; one representing venous blood (top; 20-45) and one representing arterial blood (bottom; (15-40))

Describes the fact that venous blood will always have more carbon dioxide than arterial blood because when CO2 binds to Hb, Hb loses affinity for O2

Describe what influences PACO2

PACO2 is proportional to VCO2 output and inversely proportional to alveolar ventilation

• PACO2 = (VCO2)/VA

Describe PaCO2 relative to % VO2 max

PaCO2 decreases as %VO2 max increases because CO2 is being blown off