writting a case statement in Ms SQL

writting a case statement in Ms SQL

After i run my select statement i get the following values "see image"
want i would like to di is have case statement to check if
"BloodPressureSystolic == 0 and if BloodPressureDiastolic == 0" then pull
the values from "BPSRSit and BPSRSit" and add then add the values to the
temp table like this "115/65" can someone show me how to write a case like
that.

here is my select statement that i would like to add a case statement to
select ad.ApptDate ,
ISNULL(v.Temperature, 0) as Temperature,
ISNULL(v.PS, 0) as PerfStatus,
v.*
from vitals v,AppointmentData ad
Where v.PatientId = 11
And ad.ApptId = v.ScheduleId
and ad.ApptDate < GETDATE()
and ad.StatusId not in (3,8)