Blood pressure measurement in the elderly: correlation of arterial stiffness with difference between intra-arterial and cuff pressures.

Intra-arterial (radial) blood pressure (BP) measurement was compared with the indirect cuff method in 55 healthy volunteers aged from 59-80 years (mean 68.6 +/- 5.2 s.d.). On average, the cuff method underestimated systolic BP by 5 mmHg and overestimated diastolic BP by 8 mmHg. Cuff measurement underestimated systolic BP by greater than 10 mmHg in 17 cases, and by greater than 20 mmHg in three cases. The cuff method overestimated diastolic BP by greater than 10 mmHg in nine cases (one greater than 20 mmHg) and in two cases the cuff overestimated diastolic BP by greater than 30 mmHg, compared with intra-arterial pressures. The differences correlated with pulse wave velocity, an index of arterial stiffness. A pulse wave velocity index reflecting the entire length from the aortic root to the posterior tibial artery (PWVI/ao-pt) gave a correlation (r) of 0.48 (P less than 0.0005) with systolic arterial/cuff (A/C) difference, a correlation of 0.43 (P less than 0.001) with diastolic A/C difference, and a correlation of 0.57 (P less than 0.00001) with the A/C difference in measurement of mean arterial pressure. A positive but weaker correlation was observed between A/C difference and PWVI aorta-femoral. Although the pressure differences were not as great in these healthy elderly subjects as in previous studies of patients suspected of having pseudo-hypertension, caution still appears to be indicated in the interpretation of cuff blood pressure measurement in the elderly.