Figure 1.
Oscillometric blood pressure (BP) measurement principle, which is employed by most automatic cuff devices, and associated algorithms. (A) The external pressure (Pe) of an artery is swept via cuff inflation/deflation, and Pe (i.e., cuff pressure) is measured and high-pass filtered to yield oscillations (O). Systolic BP (Ps), mean BP (Pm), and/or diastolic BP (Pd) are then estimated from the oscillogram [peak-to-peak amplitude or envelope difference of the oscillation (O) vs. Pe function] via an empirical algorithm. (B) Popular algorithms include the maximum amplitude, derivative, and fixed ratio algorithms (Ng and Small, 1994). Symbols of the features detected by each algorithm are defined as illustrated (see Glossary for text description).