Continuous Blood Pressure Monitoring Using Nonpulsatile Photoplethysmographic Components for Low-Frequency Vascular Unloading

Abstract

Objective: Continuous blood pressure (BP) monitoring gives a better understanding of a person's cardiovascular health status than single BP measurements. The existing measurement techniques are often highly complex and expensive, or suffer from inaccuracies. We propose a simple yet effective technique for continuous blood pressure monitoring. Methods: Our method is based on the finding that the non-pulsatile (DC) component of the photoplethysmograph (PPG) correlates with blood pressure. By keeping the infrared PPG DC component constant by altering the applied external pressure using a feedback mechanism the BP can be measured continuously. This way the pressure read from the pressure sensor follows the mean intra-arterial BP. We call this low-frequency vascular unloading. We propose a method for assessing the measurement error introduced by changes in vasomotor tone. Green PPG was used for the vasomotor compensation method. We packaged the technology to a wearable finger-worn device similar to a pulse oximeter probe. Results: We measured over 90 minutes of continuous BP data from total of 7 subjects. The subjects were asked to perform different BP altering maneuvers during the measurement. The ability to track BP changes was verified by continuous mean arterial pressure (MAP) readings measured with the reference device (CNSystems CNAP 500) and our device, resulting in correlation of r = 0.894 and ((mean ± SD) mmHg) of (0.3 ± 4.3) mmHg for mean arterial pressure. Without vasomotor tone compensation the results were with slightly less accurate: r = 0.83, (−1.4±5.1) mmHg. Conclusion: The proposed technology performed well compared to traditional vascular unloading technique while requiring significantly less complex control logic and no fastswitching pneumatics. Significance: The proposed technique is simple, yet effective, low-cost solution and it can be constructed from off-the-shelf components and miniaturized into a wearable form factor. The technique has potential in the field of health wearables and remote continuous BP monitoring for personalized health applications.

Non‐Invasive Hemodynamic Monitoring System Integrating Spectrometry, Photoplethysmography, and Arterial Pressure Measurement Capabilities

“…In fact, in our previous study [ 15 ] we found that the DC component of yellow PPG reacted the most to pressure‐induced vasodilation, and in ref. [ 39 ] we showed that the DC component of green PPG can be used to compensate for vasomotor activity in a continuous BP monitoring system. A somewhat similar conclusion was made in ref.…”

Development of a Personalized Multiclass Classification Model to Detect Blood Pressure Variations Associated with Physical or Cognitive Workload

“…These devices employ multi-modal sensors that exploit diverse physical principles to extract information regarding the status of the cardiovascular system [ 9 , 10 , 11 , 12 , 13 ]. Continuous arterial BP measurement has been widely acknowledged as a more accurate determinant of cardiovascular risks since alterations in systolic or diastolic BP, along with changes in the shape of BP waveforms over time, reflect the progression of arterial and arteriolar modifications [ 14 , 15 ]. Moreover, by analyzing the arterial pressure waveforms, the cardiovascular status can be assessed through the estimation of physiological parameters [ 16 , 17 ].…”