Question

In which of the following situations will arterial PO₂ be closest to 100 mmHg?

1. A dog that is having a severe asthma attack
2. A horse that lives in high altitude
3. A dog that has a right-to-left cardiac shunt
4. A cat that has a left-to–right cardiac shunt
5. An animal that has pulmonary fibrosis

Answer 1

Option D is the correct answer.

In all the conditions except D the level of oxygen in the blood is decreases while in left to right shunt level of oxygen is increased.

In severe asthma attack patients cannot breath properly which leads to hypoxia.

At high altitude the pressure of oxygen is very less.

Right to left shunt avoid blood entry to pulmonary circulation.

In case of left to right shunt oxygenated blood goes to lungs again and again and thus more perfusion occurs leading to increased level of oxygen in the blood and thus PaO2 reaches at its maximum value (100 mmHg).