Lecture 20: Oxygen Carriage in Blood
High Altitude

Oxygen Uptake in the Lungs is Increased About 70X by Hemoglobin in the Red Cells

Each Hemoglobin Can Bind Four O2 Molecules (100% Saturation)

The Normal Blood Hematocrit is Just Below 50%

At Sea Level the Partial Pressure of O2 is High Enough to Give Nearly 100% Saturation of Hemoglobin

At High Altitudes Hemoglobin Saturation May be Well Below 100%

Fetuses Live in a Low Oxygen Environment and Require a Special Hemoglobin

Acid Conditions Help Release O2 in the Tissues

The left (black) curve is at pH 7.4, the middle (red) curve is at pH 7.1, and the right (blue) curve is at pH 6.8. For any pO2 the hemoglobin is more saturated at pH 7.4 than at pH 6.8.

Hypoxia Can Have Several Causes

Type of
O2 Uptake
in Lungs
 Tissue O2
 Hypoxic  Low Normal Nornal Normal
 Anemic  Normal  Low Normal Normal
 Ischemic  Normal Normal  Low Normal
 Histotoxic  Normal Normal Normal  Low