Getting The Middle Initial From A Name Column

-- I have a first name field that sometimes contains only the first name,
-- sometimes contains the first name and the middle initial, and
-- sometimes contains the first name, a space, followed by NMI (for no middle initial)
-- how do I correctly grab the first letter of the middle initial in all cases?
-- I have been playing with patindex but its harder than I thought. guess I need a case
-- statement in addition to this. Any idea how I can do this?
-- thanks!

create table UHS_t1 (c1 varchar(20))
insert UHS_t1 select 'john a'
insert UHS_t1 select 'jeff b'
insert UHS_t1 select 'sue z'
insert UHS_t1 select 'joe nmi'
insert UHS_t1 select 'jamie'


select *, substring(c1, patindex('%[ ]%', c1)+1, 1) as middle_name
from UHS_t1
go
drop table UHS_t1