What I can't Find

I have been unable to find anything that says whether Covid-19 patients have normal levels of nitric oxide (NO).  I have, in contrast, found multiple references to inhaled NO therapies being trialed.  

I have been looking for something to support or refute the idea that the coronavirus depresses NO levels by causing hemoglobin to leak out of red blood cells and into the blood plasma.  It was the idea that low NO levels might be causing the Covid toes phenomenon that started me down this path.  

It's not a direct refutation, but I found the reason why there is no blood test for NO.  

"Direct NO detection in blood is very challenging due to its high reactivity with cell-free hemoglobin that limits NO half-life to the millisecond range." 

So if NO in the blood is always zapped within milliseconds by cell-free hemoglobin, it's hard to see how a little more spilled hemoglobin could alter the normal picture if NO is "scavenged" out of the blood in milliseconds in healthy people.  

In passing, I found this odd thread of research that says humming increases the level of NO in the nose and sinuses.   Who would have ever guessed that.   But the original research seems to have been replicated.  

So at this point, it seems there is a lot of interest in NO supplementation as a therapy.  As to the secondary question of how it helps, the answer seems to be the inhibitory effect on viral replication.  I cannot find any answer to my question about whether NO supplementation brings other bodily processes that are regulated by NO back to their normal range.