​{ngI'} means "weigh, have a weight of". In the context of air pressure, {ngI'chu'} is used to mean "be properly pressurized"​ but really means something like "weigh perfectly, have the perfect weight". This makes sense for air, because air mainly exerts its pressure by weighing down on things. Blood, on the other hand, exerts pressure through the force of the heart's contractions, so I wouldn't automatically assume {ngI'} would work for blood pressure. (It might -- there's a reasonably obvious metaphorical association between weight and pressure, so I could see a word for weight being used for pressure also. But we don't know for sure.)

Perhaps something like {joqpu'ghach HoS} "strength/power of a heartbeat" might work until we get clearer insight from Maltz.