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Blood Pressure

Blood pressure is the lateral force exerted by the blood column per unit area of the vascular wall that is expressed in mm of Hg.
Korotkoff Sounds
Korotkoff sounds should be examined preferably with bell of the stethoscope. There are five phases of korotkoff sounds, i.e., the sounds produced by the flow of blood as the constricting BP cuff is gradually released.
Phase I      First appearance of clear, tapping sound. It represents the systolic blood pressure
Phase II Tapping sounds are replaced by soft murmurs
Phase III   Murmurs become louder
Phase IV Muffling of sounds
Phase V Disappearance of sounds.
Diastolic pressure closely corresponds to phase V.
However, in aortic regurgitation, the disappearance point is extremely low, sometimes 0 mm Hg and so phase IV is taken as diastolic BP in adults as well as children.
When Korotkoff sounds are not heard while recording BP, ask the patient to raise the cuffed upper limb and ask him to open and close the fist of that hand repeatedly and then record the BP.
The BP apparatus
The length of the bladder is approximately twice that of the width. The average length of the rubber bag is 25 cm.
The air bag within the cuff should extend for at least 2 /3rd of the arm length and circumference.
Various Cuff Sizes for BP Measurement
Age in Years Width of the bladder of the cuff

< 1 yr                 2.5cm
1-5 yr                 5cm
6-10 yre             10 cm
Normal adult   12.5cm
Obese adult     14cm