Final answer:
Orthostatic blood pressure measurements are taken to diagnose orthostatic hypotension, a condition that causes dizziness upon standing due to a drop in blood pressure stemming from challenges in cardiovascular compensation against gravity.
Step-by-step explanation:
We obtain orthostatic blood pressure measurements to assess how the cardiovascular system responds to a change in body position, specifically from sitting or lying down to standing. This assessment helps in diagnosing orthostatic hypotension, a condition where blood pressure falls significantly when a person stands up, leading to dizziness or light-headedness due to a temporary reduction in blood flow to the brain. The drop in blood pressure is due to the hydrostatic pressure exerted by gravity on the circulating blood, which increases the challenge for the heart to pump blood against gravity.
There are different reasons for orthostatic hypotension to occur. One reason can be hypovolemia, where there is not enough blood volume, often due to dehydration or the effect of certain medications like diuretics and vasodilators. Another reason can be a failure of the sympathetic reflex to compensate by increasing the heart rate and constricting blood vessels to maintain cerebral blood flow. Measuring orthostatic blood pressure helps determine if the symptoms are caused by a benign 'head rush' or an underlying medical condition that needs further investigation and management.