Direct Blood Pressure Measurements

Intra-arterial pressure in the brachial artery was compared with that in the femoral artery in children. There were no significant differences in systolic, diastolic, or mean pressures. The average auscultatory systolic pressure in the arm, obtained with a cuff 20% wider than the limb, was identical to the average direct systolic pressure in the brachial and femoral arteries. The auscultatory systolic pressure in the leg, using the same criterion for cuff width, was 11 mm Hg higher than the direct pressures. The discrepancy could represent (1) a systematic error in cuff size of inadequate width or length or (2) additional systolic amplification between the femoral and popliteal arteries. Since the femoral pressure is widely used in cardiac catheterization, this pressure is suggested as the standard for calibrating auscultatory technics. For leg blood pressure measurements a cuff at least 25% wider than the average leg diameter and long enough to encircle the limb is recommended.