Using the heart harmonics in the oscillometry to extract the blood pressure

Non-invasive measurement of the human blood pressure remains, although the commercial availability of such monitors, an active research topic. This is due to the disadvantage that the blood pressure is computed instead of directly measured. To compute the systolic and diastolic blood pressures from the oscillometry, the envelope of the oscillometric waveform is used to retrieve the systolic and diastolic pressures. This algorithm to determine the blood pressure depends on the brand of oscillometric device and as a result, this type of blood pressure measurement is scientifically ill-founded. In this paper, we investigate the possibility of extracting the systolic and diastolic blood pressures from the heart´s fundamental frequency and its harmonics. This signal´s spectrum shows similarities to the spectrum of the actual arterial blood pressure signal which is observable by invasive measurements. The algorithm we present to obtain the systolic and diastolic blood pressures from the heart harmonics operates with the same accuracy as commercial devices. Finally the new technique can be used to calibrate commercial oscillometric devices where we show an improvement of 4 mmHg.