Hypoxemia diagnostic grading

Hypoxemia actually means that the oxygen content in a person's blood is insufficient. After the body develops hypoxemia, it needs to be actively treated. Failure to actively treat it will cause very serious complications and cause great harm to the patient's health. There are many reasons for hypoxemia, but before actively treating it, you need to find out the cause and then treat it symptomatically, so that you can directly control the condition.

What are the diagnostic grades for hypoxemia?

Mild: oxygen partial pressure is 10.7～8.0kPa.

Moderate: oxygen partial pressure is 8.0～5.3kPa.

Severe: oxygen partial pressure <5.3kPa.

diagnosis

1. The PaO2 decreases due to the low oxygen pressure diffused into the arterial blood. Too low PaO2 can directly lead to a decrease in CaO2 and SaO2.

2. If there is no abnormal change in the quality and quantity of Hb, CO2max is normal.

3. As PaO2 decreases, the 2,3-DPG in red blood cells increases, so the blood SaO2 decreases.

4. In hypotonic hypoxia, PaO2 and blood SaO2 decrease, causing CaO2 to decrease.

5. The arteriovenous oxygen difference decreases or changes little. Normally, when 100 ml of blood flows through tissues, about 5 ml of oxygen is utilized, that is, A-VdO2 is about 2.23 mmol/L (5 ml/dl). The driving force for oxygen diffusion from blood to tissues is the oxygen partial pressure difference between the two. When hypotonic hypoxia occurs, PaO2 and CaO2 are significantly reduced, which slows down the diffusion rate of oxygen. The amount of oxygen diffused to tissues by the same amount of blood is reduced, ultimately leading to a decrease in A-VdO2 and tissue hypoxia. In case of chronic hypoxia, when the tissue's ability to utilize oxygen increases compensatorily, the change in A-VdO2 may not be obvious.

6. Changes in skin and mucous membrane color: The average concentration of deoxygenated Hb in normal capillaries is 26g/L (2.6g/dl). In hypotonic hypoxia, the concentration of oxygenated Hb in both arterial and venous blood decreases, the oxygenated Hb in the capillaries will inevitably decrease, and the concentration of deoxygenated Hb will increase. When the average concentration of deoxygenated Hb in the capillaries increases to above 50g/L (5g/dl) (SaO2≤80%～85%), the skin and mucous membranes may appear bluish purple, which is called cyanosis. Cyanosis is likely to occur in chronic hypoxia. Cyanosis is a manifestation of hypoxia, but not all patients with hypoxia will have cyanosis. Similarly, patients with cyanosis may not have hypoxia. For example, patients with polycythemia vera have an abnormal increase in Hb, which makes the content of deoxygenated Hb in the capillaries easily exceed 50g/L, so cyanosis is easy to occur without symptoms of hypoxia.