First author unreachable

Hi all,
I'm trying to draft the letter for the first author (my PhD advisor) to sign for my EB1a case. But he is in a very bad health condition now and what if I can't get his signature? How do I revolve this issue?

to Pedro:

I'm really sorry about that. I can't help on this issue, but I hope he recovers. I wonder if 2nd author letter/signature can help? does anyone know?