respiratory disorders

Had 2nd O2 walking test.  1st one o2 levels dropped below 90 upon exertion and became normal when sitting down and this 2nd test the person conducting test said my o2 didn't drop as much but heart rate went up 30 beats just walking around and when sat down went back to normal. Test done without O2 on. Does that mean my heart beating faster because i am not getting enough oxygen?   From the 1st test i'm suppose to be using oxygen upon exertion.   TR

[caregiver222]

It means that when exercising the muscles require additional oxygen. The oxygen delivered to the lungs is a function of units of oxygenated blood per second. The heart rate speeds up to provide this additional blood.

There are many possible etiologies, ranging from a failure of the lungs to transfer oxygen, to the erythrocytes being in limited quantity or deformed, to a problem with circulation.

You really have to tell your doctor to take a bit more time to explain everything.