Timing detection and seismocardiography waveform extraction

Abstract

Described herein is a new and robust method to extract heart-beat timing from seismocardiogram (SCG). This timing indicates the precise time location of each heart beat and therefore directly conveys heart rate information. Knowledge of the time location of each occurrence of the underlying SCG waveform allows us to obtain a clean SCG waveform estimate by time averaging noisy segments of an SCG time series. The algorithm can be implemented in wearable SCG-based devices to provide heart monitoring or diagnosis capabilities without relying on any other methodology, such as electrocardiography, as a timing reference.

Evidence towards Improved Estimation of Respiratory Muscle Effort from Diaphragm Mechanomyographic Signals with Cardiac Vibration Interference Using Sample Entropy with Fixed Tolerance Values

“…Thus, the SampEn is not just measuring the complexity of the signal but also changes in signal amplitude. Since heart sounds have a deterministic and repetitive pattern [8],[9],[10] and MMGdi vibrations are random in nature [3], the fSampEn is less influenced by cardiac vibrations than the ARV and RMS parameters. Analysis of synthetic MMGdi signals has allowed us to explore the relationship between the amplitude of heart vibrations and the amplitude of the MMGdi signal.…”

“…During apnea the respiratory muscle activity is minimal so that this MMGdi signal mainly contains MCG activity. The MCG has a stable and repetitive pattern and contains clearly defined points associated with the cardiac cycle [8], [9],[10]. To obtain a good estimation of the MCG pattern we generated an MCG signal using a template.…”

“…During the recording of MMGdi signals several potential sources of contamination in addition to environmental noise must be eliminated or controlled, cardiac vibrations, detected in seismocardiograms or mechanocardiograms (MCGs), typically causing the most interference. MCGs have a deterministic and repetitive pattern, and contain clearly defined points associated with the cardiac cycle [8], [9], [10]. The MCG signal can be detected in both hemidiaphragms, being stronger on the left side [11], and its frequency content is below 20 Hz [12], [13].…”