Development of Real-Time Cuffless Blood Pressure Measurement Systems with ECG Electrodes and a Microphone Using Pulse Transit Time (PTT)

Abstract

Research has shown that pulse transit time (PTT), which is the time delay between the electrocardiogram (ECG) signal and the signal from a photoplethysmogram (PPG) sensor, can be used to estimate systolic blood pressure (SBP) and diastolic blood pressure (DBP) without the need for a cuff. However, the LED of the PPG sensor requires the precise adjustment of both light intensity and light absorption rates according to the contact status of the light-receiving element. This results in the need for regular calibration. In this study, we propose a cuffless blood pressure monitor that measures real-time blood pressure using a microphone instead of a PPG sensor. The blood pulse wave is measured in the radial artery of the wrist using a microphone that can directly measure the sound generated by a body rather than sending energy inside the body and receiving a returning signal. Our blood pressure monitor uses the PTT between the R-peak of the ECG signal and two feature points of the blood pulse wave in the radial artery of the wrist. ECG electrodes and circuits were fabricated, and a commercial microelectromechanical system (MEMS) microphone was used as the microphone to measure blood pulses. The peak points of the blood pulse from the microphone were clear, so the estimated SBP and DBP could be obtained from each ECG pulse in real time, and the resulting estimations were similar to those made by a commercial cuff blood pressure monitor. Since neither the ECG electrodes nor the microphone requires calibration over time, the real-time cuffless blood pressure monitor does not require calibration. Using the developed device, blood pressure was measured three times daily for five days, and the mean absolute error (MAE) and standard deviation (SD) of the SBP and DBP were found to be 2.72 ± 3.42 mmHg and 2.29 ± 3.53 mmHg, respectively. As a preliminary study for proof-of-concept, these results were obtained from one subject. The next step will be a pilot study on a large number of subjects.

Intraoperative Beat-to-Beat Pulse Transit Time (PTT) Monitoring via Non-Invasive Piezoelectric/Piezocapacitive Peripheral Sensors Can Predict Changes in Invasively Acquired Blood Pressure in High-Risk Surgical Patients

“…The major advantage of PES/PCS sensors, over PPG technology, is the ability to use these sensors at sites other than the finger, as a PW can be detected with the appropriate applied pressure. Recent research has demonstrated the feasibility of using PES/PCS sensors to record continuous heart tones [ 58 ], and to decipher PWs from the neck and wrist [ 59 ]. In addition, the dual sensor components allow precise tracking of the PW using both relative pressure and absolute sensor contact pressure measurements.…”

Practical Application of a New Cuffless Blood Pressure Measurement Method

“…We previously tested a new algorithm for BP determination using ECG and PPG parameters recorded with a smartphone case against oscillometric BP measurements taken in a large sample of hypertensive patients [24]. In the present study, we compared measurements using a CardioQVARK device with measurements using a cuff-based mercury sphygmomanometer according to the standards of The Institute of Electrical and Electronics Engineers for Wearable and Cuffless Blood Pressure Measuring Devices [14,18,20]. This study included patients of different age groups and with different blood pressure levels (Table 1) and overcame some of the limitations of our previous study [24].…”

“…Based on the Rpeak measured in the electrocardiogram, either the time difference between the start points of the pulse wave of the photoplethysmography signal or the time difference between the points when the PPG signal is used; these measurements have maximum values of PTTb and PTTt, respectively [16,17]. The pulse transit time (PTT) is known to be an indicator of the BP level and may be the key to cuffless BP measurement [16][17][18], depending on its determination from ECG and photoplethysmography data [19][20][21][22]. Various models have been used for BP assessments based on the photoplethysmography method [23].…”

Non‐invasive measurement of blood pressure waveform based on spatiotemporal multi‐dimensional pulse waves

“…It is the most commonly used parameter for cuff-less BP measurement, which refers to the transmission time of pulse wave between two arterial parts, and it is inversely proportional to BP signals. [4][5][6] Pulse arrival time (PAT), similar to PTT, is defined as the time interval between ECG and PPG. 7 SBP, DBP or mean BP (MBP) can be derived by mathematical formula once PTT and PAT are determined.…”

“…Pulse transit time (PTT) is usually measured by ECG and PPG signals to estimate BP. It is the most commonly used parameter for cuff‐less BP measurement, which refers to the transmission time of pulse wave between two arterial parts, and it is inversely proportional to BP signals 4–6 . Pulse arrival time (PAT), similar to PTT, is defined as the time interval between ECG and PPG 7 .…”