Hemoglobin's affinity for oxygen is affected by the following factors:
- hydrogen ion activity (blood pH)
- pCO2 and CO (carbon monoxide) levels
- body temperature
- 2,3-DPG concentration (a tissue metabolic by-product)
Hemoglobin will have an increased affinity for oxygen, resulting in less oxygen released to the tissue, when alkalosis (high pH) is present. This can occur when there are decreased amounts of H+ ions or decreased pCO2. Other conditions that can result in an increase in hemoglobin's affinity for oxygen are the presence of carbon monoxide, a decrease in 2,3-DPG levels, and a decrease in body temperature.
Table 1. Factors that Cause a Shift to the Left. | Affinity | ↑
|
| pH | ↑ (Alkalosis) |
| CO2 | ↓ |
| 2,3-DPG | ↓ |
| Body Temperature | ↓ |
| Carbon Monoxide | Present |
*Shift to the Left = Loves oxygen, decreased delivery to tissues
To summarize:
- Hypocapnia (decreased acid (CO2) will create an alkalosis)
- Carbon monoxide has 200x more affinity for hemoglobin than oxygen
- Hypothermia (low body temperature)
Hemoglobin will have a decreased affinity for oxygen, resulting in more oxygen released to the tissue, when acidosis (low pH) is present. Acidosis can be due to an increase in H+ions or increased pCO2. An increase in 2,3-DPG levels and body temperature (fever) can also result in hemoglobin having a decreased affinity for oxygen.
Table 2. Factors that Cause a Shift to the Right. | Affinity | ↓
|
| pH | ↓ (Acidosis) |
| CO2 | ↑
|
| 2,3-DPG | ↑
|
| Body Temperature | ↑
|
*Shift to the Right = Release oxygen, increased delivery to tissues
To summarize:
- Hypercapnia (increased CO2 which will lower pH to become acidic)
- 2,3-DPG facilitates oxygen to be released from the hemoglobin molecule
- High body temperature (e.g., fever) denatures the bond between hemoglobin and oxygen allowing for oxygen to be released
