This measures blood pressure in the fingers. There is no consistent way to translate that to a brachial artery blood pressure, which IS 'close enough' to the aortic valve. No calculations are needed, because the bloods pressure at the brachial artery will be only a few mm/Hg lower than it is at the aorta.
But on the way to the fingers, the blood pressure lowers, and a multitude of factors can influence by how much. To be clear, all of the influences that alter the peripheral blood pressure will alter core blood pressure. But the degree of alteration is going to be far more extreme and unpredictable the farther away from the heart you go.
This measures blood pressure in the fingers. There is no consistent way to translate that to a brachial artery blood pressure, which IS 'close enough' to the aortic valve. No calculations are needed, because the bloods pressure at the brachial artery will be only a few mm/Hg lower than it is at the aorta.
But on the way to the fingers, the blood pressure lowers, and a multitude of factors can influence by how much. To be clear, all of the influences that alter the peripheral blood pressure will alter core blood pressure. But the degree of alteration is going to be far more extreme and unpredictable the farther away from the heart you go.