Diastolic blood pressure is indicated by fouh Korotkoff sound According to American Hea Association- onset of phase I Korotkoff s sound corresponds to systolic pressure and the disappearance of sounds (phase V) corresponds to diastolic pressure . More points about measuring blood pressure The standard technique for blood pressure measurement is the auscultatory technique. It was described by Nicolay Korotkoff in 1905 Mercury sphygmomanometers are considered a gold standard for blood pressure measurement, but they are being supplanted by aneroid sphygmomanometers The Korotkoff sound method tends to give values for systolic pressure that are lower than the true intra-aerial pressure, and diastolic values that are higher. Before performing a blood pressure reading, the patient should be comfoably seated with the back and arm suppoed, the legs uncrossed, and the upper arm at the level of the right atrium. The technique used to wrap the cuff is also impoant in assuring accurate readings. Cuffs that are wrapped too loose will result in falsely elevated values. Cuffs should be applied snugly,allowing only enough room for one finger to be slipped between the cuff and the skin surface. Inflation and deflation rate: Inflation and deflation rate of the manometer may affect the blood pressure reading. Inflation rate too slow -- Diastolic pressure is too high Deflation rate too fast -- Systolic pressure too low The sphygmomanometer pressure should then be reduced at 2 to 3 min/second. When measuring blood pressure, the cuff should be inflated to 30 mm Hg above the point at which the radial pulse disappears. The sphygmomanometer pressure should then be reduced at 2 to 3 min/second. Two readings should be performed at least one minute apa. An auscultatory gap is the interval of pressure where Korotkoff sounds indicating true systolic pressure fade away and reappear at a lower pressure point during the manual measurement of blood pressure. The improper interpretation of this gap may lead to errors made in the falsely low recording of systolic blood pressure. This gap usually occurs at a high pressure and can be mistaken for the silence of a pressure greater than the SBP, Except that the pulse can still be palpated. This is why it is greatly recommended to both palpate and auscultate the SBP. Spuriously high blood pressure is noted in: 1.Small cuff 2.0besity 3.Thick calcified aeries eg. Monkenberg's aeriosclerosis, atherosclerosis