Physiological Association between Limb Ballistocardiogram and Arterial Blood Pressure Waveforms: A Mathematical Model-Based Analysis

Abstract

By virtue of its direct association with the cardiovascular (CV) functions and compatibility to unobtrusive measurement during daily activities, the limb ballistocardiogram (BCG) is receiving an increasing interest as a viable means for ultra-convenient CV health and disease monitoring. However, limited insights on its physical implications have hampered disciplined interpretation of the BCG and systematic development of the BCG-based approaches for CV health monitoring. In this study, a mathematical model that can predict the limb BCG in responses to the arterial blood pressure (BP) waves in the aorta was developed and experimentally validated. The validated mathematical model suggests that (i) the limb BCG waveform reveals the timings and amplitudes associated with the aortic BP waves; (ii) mechanical filtering exerted by the musculoskeletal properties of the body can obscure the manifestation of the arterial BP waves in the limb BCG; and (iii) the limb BCG exhibits meaningful morphological changes in response to the alterations in the CV risk predictors. The physical insights garnered by the analysis of the mathematical model may open up new opportunities toward next generation of the BCG-based CV healthcare techniques embedded with transparency, interpretability, and robustness against the external variability.

Quantification of Resting-State Ballistocardiogram Difference Between Clinical and Non-Clinical Populations for Ambient Monitoring of Heart Failure

“…The RR-interval and BP were not related to the WFMR, suggesting that the feature was not affected by rate- or vascular-related conditions (i.e., fluctuation at rest). This effect, however, requires further study as these parameters were shown to be influenced by the vascular system, and change may manifest during a stress test [34] .…”

Pulse Transit Time-Pulse Wave Analysis Fusion Based on Wearable Wrist Ballistocardiogram for Cuff-Less Blood Pressure Trend Tracking

“…We employed a mathematical model that can predict the wrist BCG from 3 arterial BP waves: aortic inlet BP, aortic arch BP, and aortic outlet BP (shown as P0, P1, and P2 in Figure 2), which was developed in our prior work 25 . Using prespecified P0, P1,and P2 waveforms derived using in-human experimental recordings in our prior work 26 , we replicated the changes in BP by the changes in PTT and PP amplification (PPA; see Section IV.C for rationale and limitation of such replication of BP change).…”

“…Using the wrist BCG waveforms corresponding to a range of PTT and PPA values, we examined the sensitivity of the BCG PWA features with respect to BP. Our prior work illustrates that the mathematical model can robustly predict the I, J, K, and L waves in the wrist BCG ( Figure 1), while it may not predict the G and H waves ( Figure 1) since they are associated with pre-ejection activities that cannot be reproduced by arterial BP waves alone 25,27 . Hence, the mathematical model can reproduce 16 PWA features: 6 wave-to-wave time intervals (I-J, I-K, I-L, J-K, J-L, K-L), 6 wave-to-wave amplitudes (I-J, I-K, I-L, J-K, J-L, K-L), and 4 wave amplitudes (I, J, K, L).…”

“…In terms of percent sensitivity, I and I-K amplitudes were the most sensitive to BP. However, these wave amplitudes are typically very small 25 , making their accuracy prone to measurement noise and artifact common to the wearable BCG. Hence, I and I-K amplitudes were not considered.…”

The Potential of Wearable Limb Ballistocardiogram in Blood Pressure Monitoring via Pulse Transit Time

“…Given that it is the direct response to the force exerted by the blood ejected by the heart, the whole-body BCG provides rich insights on the arterial BP 16 . The whole-body BCG is also transferred to the limb sites (e.g., wrist and upper arm) to elicit the movement of the limbs (called the limb BCG) 18 . Compared with the whole-body BCG, the limb BCG is much more amenable to ultra-convenient measurement with wearable devices such as wristband.…”