DR.BEAT: Initial Functional Testing of a BCG Wearable Prototype for Recording Ballistocardiographic Signals

DR.BEAT ("Digital Research on Ballistocardiography for Extraterrestrial And Terrestrial use") develops a miniaturized sensor system with signal processing to interpret ballistocardiographic signals and implements an application oriented user interface. Presented is a breadboard prototype's functional tests with regard to data completeness and plausibility. The analysis confirmed a reliability of 99.99995% over the tests and the signals displayed the expected heart-specific characteristics. These results support the ethical justifiability of an initial study.

The kinocardiograph for assessment of fluid status in patients with acute decompensated heart failure

AIMS

To improve telemonitoring strategies in heart failure patients, there is a need for novel non-obtrusive sensors that monitor parameters closely related to intracardiac filling pressures. This proof-of-concept study aims to evaluate the responsiveness of cardiac kinetic energy (KE) measured with the Kinocardiograph (KCG), consisting of a seismocardiographic (SCG) sensor and a ballistocardiographic (BCG) sensor, during treatment of patients with acute decompensated heart failure.

METHODS AND RESULTS

Eleven patients with acute decompensated heart failure who were hospitalized for treatment with intravenous diuretics received daily KCG measurements. The KCG measurements were compared with the diameter of the inferior vena cava (IVC) and body weight. Follow-up stopped at discharge, that is, in the recompensated state. Median (interquartile range) weight and IVC diameter decreased significantly after diuretic treatment [weight 74.5 (67.6-98.7) to 73.3 (66.7-95.6) kg, P = 0.003; IVC diameter 2.47 (2.33-2.99) to 1.78 (1.65-2.47) cm, P = 0.03]. In contrast with BCG measurements, significant changes in median KE measured with SCG were observed during the passive filling phase of the diastole [SGG: 0.48 (0.39-0.60) to 0.69 (0.56-0.84), P = 0.026; BCG: 0.68 (0.46-0.73) to 0.68 (0.59-0.82), P = 0.062], the active filling phase of the diastole [SCG: 0.38 (0.30-0.61) to 0.31 (0.09-0.47), P = 0.016; BCG: 0.29 (0.17-0.39) to 0.26 (0.20-0.34), P = 0.248], and the ratio between the passive and active filling phases [SCG: 2.76 (1.68-5.30) to 5.02 (3.13-10.17), P = 0.006; BCG: 5.87 (3.57-7.55) to 5.27 (3.95-9.43), P = 0.790]. The correlations between changes in KE during the passive and active filling phases, using SCG, and changes in weight or IVC were non-significant. Systolic KE did not show significant changes.

CONCLUSION

KE measured with the KCG using SCG is highly responsive to changes in fluid status. Future research is needed to confirm its accuracy in a larger study population and specifically its application for detection of clinical deterioration in the home-environment.

Classification of health deterioration by geometric invariants

BACKGROUND AND OBJECTIVES

Prediction of patient deterioration is essential in medical care, and its automation may reduce the risk of patient death. The precise monitoring of a patient's medical state requires devices placed on the body, which may cause discomfort. Our approach is based on the processing of long-term ballistocardiography data, which were measured using a sensory pad placed under the patient's mattress.

METHODS

The investigated dataset was obtained via long-term measurements in retirement homes and intensive care units (ICU). Data were measured unobtrusively using a measuring pad equipped with piezoceramic sensors. The proposed approach focused on the processing methods of the measured ballistocardiographic signals, Cartan curvature (CC), and Euclidean arc length (EAL).

RESULTS

For analysis, 218,979 normal and 216,259 aberrant 2-second samples were collected and classified using a convolutional neural network. Experiments using cross-validation with expert threshold and data length revealed the accuracy, sensitivity, and specificity of the proposed method to be 86.51 CONCLUSIONS: The proposed method provides a unique approach for an early detection of health concerns in an unobtrusive manner. In addition, the suitability of EAL over the CC was determined.

Wearables in Cardiovascular Disease

Wearable devices stand to revolutionize the way healthcare is delivered. From consumer devices that provide general health information and screen for medical conditions to medical-grade devices that allow collection of larger datasets that include multiple modalities, wearables have a myriad of potential uses, especially in cardiovascular disorders. In this review, we summarize the underlying technologies employed in these devices and discuss the regulatory and economic aspects of such devices as well as the future implications of their use.

Estimation of the respiratory rate from ballistocardiograms using the Hilbert transform

Background

Measuring the respiratory rate is usually associated with discomfort for the patient due to contact sensors or a high time demand for healthcare personnel manually counting it.

Methods

In this paper, two methods for the continuous extraction of the respiratory rate from unobtrusive ballistocardiography signals are introduced. The Hilbert transform is used to generate an amplitude-invariant phase signal in-line with the respiratory rate. The respiratory rate can then be estimated, first, by using a simple peak detection, and second, by differentiation.

Results

By analysis of a sleep laboratory data set consisting of nine records of healthy individuals lasting more than 63 h and including more than 59,000 breaths, a mean absolute error of as low as 0.7 BPM for both methods was achieved.

Conclusion

The results encourage further assessment for hospitalised patients and for home-care applications especially with patients suffering from diseases of the respiratory system like COPD or sleep apnoea.

The kinocardiograph for assessment of changes in haemodynamic load in patients with chronic heart failure with reduced ejection fraction

Aims

The kinocardiograph (KCG) is an unobtrusive device, consisting of a chest sensor, which records local thoracic vibrations produced in result of cardiac contraction and ejection of blood into the great vessels [seismocardiography (SCG)], and a lower back sensor, which records micromovements of the body in reaction to blood flowing through the vasculature [ballistocardiography (BCG)]. SCG and BCG signals are translated to the integral of cardiac kinetic energy (iK) and cardiac maximum power (Pmax), which might be promising metrics for future telemonitoring purposes in heart failure (HF). As a first step of validation, this study aimed to determine whether iK and Pmax are responsive to exercise‐induced changes in the haemodynamic load of the heart in HF patients.

Methods and results

Fifteen patients with stable HF with reduced ejection fraction performed a submaximal exercise protocol. KCG and cardiac ultrasound measurements were obtained both at rest and at submaximal exercise. BCG iK over the cardiac cycle (CC) increased significantly (0.0026 ± 0.0017 to 0.0052 ± 0.0061 mJ.s.; P = 0.01) during exercise, in contrast to a non‐significant increase in SCG iK CC. BCG Pmax CC increased significantly (0.92 ± 0.89 to 2.03 ± 1.95 mJ/s; P = 0.02), in contrast to a non‐significant increase in SCG Pmax CC. When analysing the systolic phase of the CC, similar patterns were found. Cardiac output (CO) ratio (i.e. CO exercise/CO rest) showed a moderate, significant correlation with BCG Pmax CC ratio (r = +0.65; P = 0.008) and with SCG Pmax CC ratio (r = +0.54; P = 0.04).

Conclusions

iK and Pmax measured with the KCG, preferentially using BCG, are responsive to changes in the haemodynamic load of the heart in HF patients. The combination of the BCG and SCG sensor might be of added value to fully understand changes in haemodynamics and to discriminate between an HF patient and a healthy individual.

Application of mechanical trigger for unobtrusive detection of respiratory disorders from body recoil micro-movements

Background and Objectives Automatic detection of breathing disorders plays an important role in the early signalization of respiratory diseases. Measuring methods can be based on electrocardiogram (ECG), sound, oximetry, or respiratory analysis. However, these approaches require devices placed on the human body or they are prone to disturbance by environmental influences. To solve these problems, we proposed a heart contraction mechanical trigger for unobtrusive detection of respiratory disorders from the mechanical measurement of cardiac contractions. We designed a novel method to calculate this mechanical trigger purely from measured mechanical signals without the use of ECG. Methods The approach is a built-on calculation of the so-called euclidean arc length from the signals. In comparison to previous researches, this system does not require any equipment attached to a person. This is achieved by locating the tensometers on the bed. Data from sensors are fused by the Cartan curvatures method to beat-to-beat vector input for the Convolutional neural network (CNN) classifier. Results In sum, 2281 disordered and 5130 normal breathing samples was collected for analysis. The experiments with use of 10-fold cross validation show that accuracy, sensitivity, and specificity reach values of 96.37%, 92.46%, and 98.11% respectively. Conclusions By the approach for detection, the system offers a novel way for a completely unobtrusive diagnosis of breathing-related health problems. The proposed solution can effectively be deployed in all clinical or home environments.

Effects of acquisition device, sampling rate, and record length on kinocardiography during position-induced haemodynamic changes

BACKGROUND

Kinocardiography (KCG) is a promising new technique used to monitor cardiac mechanical function remotely. KCG is based on ballistocardiography (BCG) and seismocardiography (SCG), and measures 12 degrees-of-freedom (DOF) of body motion produced by myocardial contraction and blood flow through the cardiac chambers and major vessels.

RESULTS

The integral of kinetic energy ([Formula: see text]) obtained from the linear and rotational SCG/BCG signals was computed over each dimension over the cardiac cycle, and used as a marker of cardiac mechanical function. We tested the hypotheses that KCG metrics can be acquired using different sensors, and at 50 Hz. We also tested the effect of record length on the ensemble average on which the metrics were computed. Twelve healthy males were tested in the supine, head-down tilt, and head-up tilt positions to expand the haemodynamic states on which the validation was performed.

CONCLUSIONS

KCG metrics computed on 50 Hz and 1 kHz SCG/BCG signals were very similar. Most of the metrics were highly similar when computed on different sensors, and with less than 5% of error when computed on record length longer than 60 s. These results suggest that KCG may be a robust and non-invasive method to monitor cardiac inotropic activity. Trial registration Clinicaltrials.gov, NCT03107351. Registered 11 April 2017, https://clinicaltrials.gov/ct2/show/NCT03107351?term=NCT03107351&draw=2&rank=1 .

A Structured Measurement of Highly Synchronous Real-Time Ballistocardiography Signal Data of Heart Failure Patients

Ballistocardiography (BCG) has gained more attention due to the fundamental goal of medical intervention in diagnostics and follow-up. BCG is particularly suitable for the study of heart failure, which a recent study has shown. The results of this working group shall be validated and reproduced with another study trial. Therefore, acceleration sensor prototypes will be placed on various parts of the patient's body and be connected to a computer unit, which allows a high data quality and high signal resolution. A temporal shift of only 20 ns ensures real-time measurement of BCG parameters. The reference measurement will be done with a 12-channel ECG. The study will include patients with heart failure. All conducted tests take place as part of the diagnostic-therapeutic routine. The only change in the procedure concerns the additional equipment with the measuring sensors. The results will be the validation of the data from the other working group, as well as the information about the choice of sensors and clock frequency, the measuring points and the needed features for early detection of heart failure in BCG signals.

Development of a Presentation Interface for Seismo- and Ballistocardiographic Data

Ballistocardiography is a method to gain detailed information about body movements imparted by the ballistic forces associated with cardiac contraction. We measured using different setups and sensor positions to gain information of a reference signal of healthy adults. We used two resting state recordings and two recordings under physical stress (ergometer and treadmill) with stepwise increasing load. Data was gathered from 34 subjects, which results in 72 data sets, overall, more than 18h of signal data. With these data we have created a first database for BCG reference. We started data analysis and created a first naive data representation prototype. Using this naive attempt, we created a user interface for the intuitive representation of live data as well as retrospective data.

Trodden Lanes or New Paths: Ballisto- and Seismocardiography Till Now

Ballisto- and seismocardiography (BCG/SCG) are methods of studying blood circulation and cardiac function by using the vibration measurements at the body surface, e.g. via accelerometers. The aim of this work is to show the current relevance of BCG/SCG for the target medical diagnostics. To reach this goal and to examine the relevance, an overall search for all BCG and SCG articles in the databases PubMed and IEEEXplore was first carried out ("ballistocardiography OR seismocardiography") for the years till 2019. The results of this literature study show, overall 425 papers for the years from 2003 till 2019, with BCG (317) as significantly stronger represented than SCG (120). The distribution of the included subjects shows that a smaller group (n<=10) of mostly healthy people is more common. Last but not least, we examined which sensors have been included in the articles since 2003, with the result that accelerometers, whether as self-developed prototypes or installed in smartphones, were used in slightly less than 50% of the articles found. The differences in the numbers of publications between BCG and SCG may also be due to the distinction's complexity between BCG, which is more intuitive, and SCG. Looking at the number and distribution of included subjects, it is noticeable that this is rather low and primarily healthy subjects are used. However, the publication increase indicates that we are at a threshold in this topic and actual benefit to medicine.

Towards health monitoring using remote heart rate measurement using digital camera: A feasibility study

The paper presents a feasibility study for heart rate measurement using a digital camera to perform health monitoring. The feasibility study investigates the reliability of the state of the art heart rate measuring methods in realistic situations. Therefore, an experiment was designed and carried out on 45 subjects to investigate the effects caused by illumination, motion, skin tone, and distance variance. The experiment was conducted for two main scenarios; human-computer interaction scenario and health monitoring scenario. The human-computer scenario investigated the effects caused by illumination variance, motion variance, and skin tone variance. The health monitoring scenario investigates the feasibility of health monitoring at public spaces (i.e. airports, subways, malls). Five state of the art heart rate measuring methods were re-implemented and tested with the feasibility study database. The results were compared with ground truth to estimate the heart rate measurement error. The heart rate measurement error was analyzed using mean error, standard deviation; root means square error and Pearson correlation coefficient. The findings of this experiment inferred promising results for health monitoring of subjects standing at a distance of 500 cm.

First Feasibility Analysis of Ballistocardiography on a Passenger Flight

The project SCARAB2 (Scalable, Robust and Adaptive on Board Ballistocardiography) aims to use Ballistocardiography (BCG) to monitor flight passengers. In order to show that recorded BCG data from flights give evaluable information even in the noisy environment of an airplane, we monitored a heart-healthy passenger using BCG. Furthermore, we show that there can be a conclusion to heart activities from the recorded ballistocardiogram by comparing the data to a concurrently recorded electrocardiogram (ECG).

Nonintrusive Remote Monitoring of Sleep in Home-Based Situation

Sleep deprivation can lead to loss of concentration, and risky decision-making. Nevertheless, some people may underestimate the importance of getting quality sleep. The standard health care systems might not be suitable for long-term monitoring of sleep. As an example, the polysomnography, i.e., the gold standard for assessing sleep disorders is cumbersome, expensive, and time-consuming. As a result, portable, nonintrusive and inexpensive systems for monitoring quality of sleep are greatly needed. This paper demonstrates a novel nonintrusive system for monitoring quality of sleep using an optical fiber embedded sensor mat. The proposed system is deployed in real-life conditions over a one-month period. Three senior female residents were enrolled for the study, where the sensor mat is placed under the bed mattress. Sleep quality is assessed based on several parameters, such as duration of sleep, sleep interruption, vital signs (heart rate and respiration). The proposed system shows an agreement with a user's survey collected before the study. Furthermore, the system is integrated within an existing ambient assisted living platform with a user-friendly interface to make it more convenient for the caregivers to follow-up the sleep parameters of the residents.

Theory and developments in an unobtrusive cardiovascular system representation: ballistocardiography

Due to recent technological improvements, namely in the field of piezoelectric sensors, ballistocardiography - an almost forgotten physiological measurement - is now being object of a renewed scientific interest.Transcending the initial purposes of its development, ballistocardiography has revealed itself to be a useful informative signal about the cardiovascular system status, since it is a non-intrusive technique which is able to assess the body's vibrations due to its cardiac, and respiratory physiological signatures.Apart from representing the outcome of the electrical stimulus to the myocardium - which may be obtained by electrocardiography - the ballistocardiograph has additional advantages, as it can be embedded in objects of common use, such as a bed or a chair. Moreover, it enables measurements without the presence of medical staff, factor which avoids the stress caused by medical examinations and reduces the patient's involuntary psychophysiological responses.Given these attributes, and the crescent number of systems developed in recent years, it is therefore pertinent to revise all the information available on the ballistocardiogram's physiological interpretation, its typical waveform information, its features and distortions, as well as the state of the art in device implementations.