I feel totally lost, just want to share with brothers and sisters here.
Here is want happened to me, I started my journey from Feb due to episodic SOB and low oxygen (randomly happen), later PFT showed borderline ratio and my doctor put me on asthma treatment. During the last 8 months my respiratory symptoms fluctuated and has been totally gone since last month, meanwhile my hypoxemia has been trending worse (more frequent and predictable).
I did so many tests - CTPA, blood tests, Stress Echo, Echocardiogram, heart MRI, sputum culture, all normal, even the latest PFT gave me a ratio of >0.7 pre and post.
My SPO2 is very predictable now, my typical normal saturation is ~96%, almost always drop to 92% every time speaking loudly, laying down, sleeping, after hot bath, during and after dinner. Sometimes exertion also brings it down.
Fast and shallow breath does not help, while deep breath can always temporarily bring it back to normal.
I guess the only thing left to exclude would be pulmonary hypertension.
My doctor has ordered CPET for me, really hope it's not pulmonary hypertension.