Analyzing systolic time intervals-specifically the preejection-period (PEP)-is widely accepted as one of the few methods for the noninvasive assessment of cardiac contractility. In this paper, we investigated the ballistocardiogram (BCG) as a way to noninvasively measure myocardial contractility when combined with the ECG. Specifically, we derived a parameter from the BCG and ECG that we hypothesized would be highly correlated to PEP. This is the time delay between the J-wave peak of the BCG and the R-wave of the ECG, which we refer to as the RJ interval. The RJ interval was correlated to PEP (r(2) = 0.86) for 2126 heartbeats across ten subjects, with a y-intercept of 138 ms and slope of 1.05. This suggests that the RJ interval can be reliably used as a noninvasive assessment of cardiac contractility.

This paper presents a method of extracting primary heart sound signals from chest-worn accelerometer data in the presence of motion artifacts. The proposed method outperforms noise removal techniques such as wavelet denoising and adaptive filtering. Results from six subjects show a primary heart signal detection rate of 99.36% with a false positive rate of 1.3%.

The ballistocardiogram (BCG) is a measure of the reaction force of the body to cardiac ejection of blood. A variety of systems can be used for BCG detection, including beds, tables, chairs, and weighing scales. Weighing scales, in particular, have several practical advantages over the alternatives: low cost, small size, unobtrusiveness, and familiarity to the user; one disadvantage is that the subject must stand during the recording, rather than sit or lay supine, resulting in a higher susceptibility to motion artifacts in the measured signal. This paper evaluates the electromyogram (EMG) signal acquired from the feet of the subject during BCG recording as a noise reference for standing BCG measurements. As a subject moves while standing on the scale, muscle contractions in the feet are detected by the EMG signal, and used to flag segments of the BCG signal that are corrupted by elevated noise. For the purposes of evaluating this method, estimates of the BCG noise-to-signal ratio (NSR) were independently calculated with an ensemble average method, using the R-wave of a simultaneously-acquired chest ECG as a timing reference. The linear correlation between EMG power alone and BCG NSR from 14 subjects was found to be moderate ( r = 0.58, F-statistic p -value 0.05); combined with body-mass index (BMI), multiple linear regression yielded a stronger correlation ( r = 0.73, F -statistic p-value = 0.01). Additionally, an example usage of the lower-leg EMG for improving BCG measurement robustness is provided.

A bathroom scale ballistocardiogram (BCG) recorder has been developed in our group as a potential home monitor for heart failure outpatients. While the signal quality obtained by this device is as high as elaborate table- and bed-based BCG systems discussed previously in the literature, the standing posture required by this system may lead to undesired motion induced noise in the signal, particularly for elderly patients. Electromyogram (EMG) signals from the feet are proposed as a noise reference for the standing BCG measurement. The correlation between these signals and the BCG noise is quantified for a case with low (eyes open) and higher (eyes closed) involuntary movement on the scale. For the six subjects considered in this trial, the foot EMG appears to be a valuable reference for BCG movement noise estimation. Additionally, the fact that many bathroom scales have electrodes on the feet for various body fat percentage estimates makes the measurement highly practical for future implementations.

A novel, unobtrusive and wearable, multiparameter ambulatory physiologic monitoring system for space and terrestrial applications, termed LifeGuard, is presented. The core element is a wearable monitor, the crew physiologic observation device (CPOD), that provides the capability to continuously record two standard electrocardiogram leads, respiration rate via impedance plethysmography, heart rate, hemoglobin oxygen saturation, ambient or body temperature, three axes of acceleration, and blood pressure. These parameters can be digitally recorded with high fidelity over a 9-h period with precise time stamps and user-defined event markers. Data can be continuously streamed to a base station using a built-in Bluetooth RF link or stored in 32 MB of on-board flash memory and downloaded to a personal computer using a serial port. The device is powered by two AAA batteries. The design, laboratory, and field testing of the wearable monitors are described.

For more than three decades, it has been possible to use microlithographically fabricated extracellular electrodes to record action potential (AP) signals from electrically active cells such as neurons of intact organisms. There has also been a steady evolution of techniques to interface between electronic circuits and neural or cardiac cells cultured on arrays of such electrodes, mainly directed toward basic science goals. More recently, such combinations of living cells and electronics have been harnessed as tools for the detection of chemical and biological toxins, and for screening of pharmacologically active compounds. This paper presents a survey of the relevant technologies, cell types available, specific requirements for applications, and discussion of opportunities for future development.

The first micromachined bimorph organic ciliary array with on-chip CMOS circuitry is presented. This device is composed of an 8/spl times/8 array of cells each having four orthogonally oriented actuators in on overall die-size of 9.4 mm/spl times/9.4 mm. The polyimide based actuators were fabricated directly above the selection and drive circuitry. Selection and activation of actuators in this array shows that integration was successful. The integration of CMOS electronics and MEMS micromechanisms allows the implementation of new task-level micromanipulation strategies. New low-level control algorithms (actuator gaits) were also demonstrated. The array was programmed to perform several kinds of manipulation tasks, including linear translation, diagonal motion, as well as vector field operations such as squeeze field and radial field orienting and centering. Preliminary experiments were also performed using thin silicon dice of about 3 mm/spl times/3 mm/spl times/0.5 mm size as the object being moved.

Bulk silicon etching techniques, used to selectively remove silicon from substrates, have been broadly applied in the fabrication of micromachined sensors, actuators, and structures. Despite the more recent emergence of higher resolution, surface-micromachining approaches, the majority of currently shipping silicon sensors are made using bulk etching. Particularly in light of newly introduced dry etching methods compatible with complementary metal-oxide-semiconductors, it is unlikely that bulk micromachining will decrease in popularity in the near future. The available etching methods fall into three categories in terms of the state of the etchant: wet, vapor, and plasma. For each category, the available processes are reviewed and compared in terms of etch results, cost, complexity, process compatibility, and a number of other factors. In addition, several example micromachined structures are presented.

Distributed manipulation experiments were performed using a massively-parallel, microfabricated actuator array. An organic ciliary array of thin-film polyimide bimorph microactuators exploiting combined thermal and electrostatic control was employed to implement task-level, sensorless manipulation strategies for macroscopic objects. The tasks of parts-translation, -rotation, -orientation, and -centering were demonstrated using small integrated circuit (IC) dice. Strategies were programmed in a fine-grained SIMD (single instruction, multiple data) fashion by specifying planar force vector fields. When a part is placed on the array, the programmed vector field induces a force and moment upon it. The part's equilibrium states may be predicted and cascaded (using a sequence of fields) to bring the part to a desired final state. Vector fields with and without potential were tested in experiments, and the behavior of parts in the fields was compared with the theory of programmable vector fields. These fields were implemented by actuating the organic cilia in a cyclic, gait-like fashion. Motion in non-principal (e.g. diagonal) directions was effected by a pairwise coupling of the cilia to implement virtual cilia. These experiments suggest that MEMS actuator arrays are useful for parts-orientation, -posing, -transfer, -singulation, and -sorting.