Blood oxygen levels are important for our health. Let’s look at how they work in two parts of our body: pulmonary circulation and systemic circulation.

1. Pulmonary Circulation:

   • What it does: This part brings blood to the lungs to get oxygen.
   • Oxygen Levels: The blood here has a lot of oxygen (high $O_2$) and not much carbon dioxide (low $CO_2$).

2. Systemic Circulation:

   • What it does: This part takes the oxygen-rich blood and delivers it to the rest of the body.
   • Oxygen Levels: The amount of oxygen can change; when we exercise, the oxygen levels may go down.

Even with these differences, we can help our lungs work better. For example, using extra oxygen can help increase the amount of oxygen in the blood. This can make things better for both parts of our circulatory system.