Gas Transport

Question 1

O2 and CO2 PP Gradients

Answer 1

In alveolar air, more CO2 because eliminating it, and lower O2 because absorbing it into tissues

Alveolar Air: PO2 of 105mmHg, PCO2 of 40mmHg
Oxygenated blood: PO2 of 100mmHg, PCO2 of 40mmHg
Systemic Tissue: PO2 of 40mmHg, PCO2 of 45mmHg
Deoxygenated blood: PO2 of 40mmHg, PCO2 of 45mmHg
Atmospheric Air: PO2 of 150mmHg, PCO2 of 0.3mmHg

Question 2

PP of N2, O2, CO2, and H2O in Ambient Atmospheric Air

Answer 2

N2 = 78%
O2 = 21%
CO2 = 0.04%
H2O = 0.5%

Question 3

Total O2 Content of the Blood

Answer 3

Total O2 content of the blood = dissolved O2 + O2 Bound to Hb

Free/dissolved O2 = (0.003)(100) = 0.3

O2 bound to Hb = [Hb] (O2 binding capacity at 100% saturation) (% saturation)

[Hb] for healthy individuals = 15g Hb/dL of blood
O2 binding capacity at 100% = 1.34ml O2/g Hb

Question 4

Considerations for O2 Content

Answer 4

Total O2 content will vary with both PO2 and [Hb]
PO2 is determined only by alveolar PO2 not by [Hb]
The [Hb] affects only the amount of O2 bound to [Hb]
The PO2 affects both the amount of O2 in free solution and the amount bound to [Hb]. To determine the % saturation from the PO2 it is necessary to consult a Hb-O2 saturation curve

Question 5

Arterial PO2 during CO Poisoning

Answer 5

Arterial PO2 is usually normal, because the [CO]required to cause poisoning is low enough that it does not alter the amount of O2 dissolved in plasma. Tissues will experience hypoxia, but not cyanosis.

Question 6

O2 Unbinding from Hb to Plasma to Tissues

Answer 6

In order to get O2 from the blood plasma to the tissues, the tissues must have a lower PO2 than plasma. Once the O2 migrates from the plasma to the tissues, the PO2 decreases in plasma. To get more O2 to the plasma to continue to supply the tissues, the lowering of the PO2 in the plasma creates a gradient to allow the O2 to unbind from the Hb and released into the plasma for the cycle to continue

Question 7

Haldane Effect

Answer 7

When O2 dissociates from Hb, Hb’s binding capacity for protons and CO2 increase via the Haldane effect
CO2 produced by tissue metabolism is carried in the blood in 3 forms:
1. Dissolved bicarbonate (70%)
2. Combined with Hb as carbamino-Hb (23%)
3. Dissolved CO2 (7%)

The sequence is reversed in he lungs with Hb taking up O2 as PO2 rises, and releasing H+ and CO2

Question 8

O2 vs. CO2 Concentration Curves

Answer 8

O2 and CO2 curves: slopes are different, where O2 slope is less than CO2; range of arterial and venous mmHg is greater in O2 curve compared to CO2