I know this is old thread however i have had a similar problem and hopefully this helps others looking into this - following the UK's Blood Pressure chart ive used the following code which is working fine for me, feel free to adapt it for you.

Note! A2 is Systolic & B2 is Diastolic

=IF(OR(A2>=140,B2>=90),"High",IF(OR(AND(A2>=120,A2<140),AND(B2>=80,B2<90)),"Pre High",IF(OR(AND(A2>=90,A2<120),AND(B2>=60,B2<80)),"Ideal",IF(OR(A2<90,B2<60),"Low",""))))