In order to determine BP in basal condition
- The patient should rest in a quiet room for 15 minutes.
- He should not have consumed coffee or tea for the preceding one hour or smoked for the preceding 15 minutes.
- He should not be on adrenergic stimulants and there should be no bladder distension.
- It is desirable to record the BP in both the arms as the differences in systolic pressure exceeding 10 mm Hg between the two arms when measured simultaneously or in rapid sequence suggest obstructive lesions of aorta, innominate or subclavian arteries.
- In vertebrobasilar insufficiency, a difference in pressure between the arms may signify that a subclavian steal is responsible for cerebrovascular symptoms.
- Normally systolic pressure in the legs is up to 20 mm Hg higher than in the arms, but diastolic BP is the same. When systolic pressure in the popliteal artery exceeds that in brachial artery by > 20 mm Hg (Hill's sign), AR is usually present. Measuring lower limb BP is useful in detecting coarctation of aorta or obstructive disease of the aorta or its immediate branches.
- When the diastolic pressure is below 90 mm Hg, a systolic pressure below 140 mm Hg indicates normal blood pressure.
- Blood pressure between 140-149 mm Hg indicates borderline isolated systolic hypertension
- Blood pressure more than 140 mm Hg or higher indicates isolated systolic hypertension.
- When there is an elevation of systolic pressure of > 30 mm Hg and a diastolic pressure of > 20 mm Hg from the basal original level, it indicates presence of hypertension.