async queries (libpq)

Hi, I need to execute some queries that do not return any value
for example "DELETE * FROM foo". This queries take a lot of time and I
can't put them together in a single query.
If I use the non-blocking function PQsendQuery() I have to wait until
the execution of the first query terminates before executing another
query right?
In my case (without a result for the query) is it right to check only if
PQisBusy returns 0 inside a loop before executing the next query?