RESUMO
A continuous noninvasive method for blood pressure (BP) estimation by pulse wave transit time (PWTT) is described. A constant linear relation is available between PWTT and BP, but characteristic parameter for the relation is different for different persons. According to hydrostatics, BP in some vessel changes with different body postures. In this paper, the difference, i.e. △BP, between two BP values with different body postures is gained. ECGs and surface pulse waves are also obtained, and then values of PWTT are calculated. Through the A BP and PWTT acquired above, parameter b of BP equation can be determined, and then parameter a is computerized through the measurements and one BP value. Thus a BP equation is got, which can be used to estimate BP values through continuous measurement of PWTT. Compared with the value from invasive BP measurement, the value from this method has an error rate less than 5%. The method is feasible for noninvasive continuous BP monitoring.
