Some good information from gas_dr , a front line doctor that I know. He has dealt with this on the front line to speak. Look him up.
He is right, effective in early onset.
Later on not so great, like when on a vent because of ARDS etc.
He's a good man. Goes to the same church my sister and Bro in law go (and I'm a member, but it's 475 miles away), and was involved with my brother's case when he passed on a couple of years back. Very straightforward guy.