Unconstrained heart-rate monitoring during bathing.

An unconstrained electrocardiograph (ECG) and heart-rate monitor was designed to record ECG measurements in the bathtub. The apparatus consists of analog and digital parts. In the analog part, electrocardiographic signals obtained from electrodes placed inside the bathtub were amplified approximately 4,000 times. The electrodes were made of stainless steel and were 104 x 74 x 0.5 mm in size, including the absorbent sponge covers. Each electrode fitted into a plastic case 110 x 79 x 23 mm in size. Working electrodes were placed 20 cm from the bottom of the long bathtub wall, close to the position of the immersed trunk, and a reference electrode was placed 5 cm from the bottom of the side wall close to the toe position. In the digital part of the system the heart rate was calculated from the R-R interval of each ECG pulse and the calculated data were stored in a random-access memory. These stored data were transferred to a personal computer through an RS 232C interface and analyzed. The heart rates obtained from the bathtub ECG agreed with those obtained from a body-surface ECG. During measurements in bathwater with various concentrations of sodium chloride, the amplitude of the electrocardiographic waveform decreased as the electrical conductivity increased. The frequency characteristics of the bathtub ECG varied with the bathtub dimensions and the electrical conductivity of the water. Using this apparatus, heart-rate measurements can be obtained easily and noninvasively, but interpretation of the ECG signal requires great care. This monitor could be used as a home health heart-rate monitor.

Monitoring of heart and respiratory rates by photoplethysmography using a digital filtering technique.

An apparatus for simultaneously monitoring heart and respiratory rates was developed using photoplethysmography (PPG) and digital filters, and compared with conventional methods. The PPG signal, which includes both heart and respiratory components, was measured at the earlobe with an original transmission mode photoplethysmographic device. A digital filtering technique was used to distinguish heart and respiratory signals from the PPG signal. The cut-off frequency of the respiratory signal filter was selected automatically depending on the heart rate. Using digital filtering techniques, heart and respiratory signals were separated at rest and during exercise. The digital signal processor was employed to realize an adaptive and real-time filtering. The heart rate was calculated by the zero-crossing method and the respiratory rate from the peak interval of the filtered signal. To evaluate the newly developed monitor, an ECG for heart rate and a transthoracic impedance plethysmogram for respiratory rate were monitored simultaneously. To obtain higher heart and respiratory rates, exercise was performed on an electrical bicycle ergometer. Heart and respiratory rates calculated by the new method compare to those obtained from ECG and the transthoracic impedance plethysmogram. The maximum error of heart and respiratory rates was 10 beats/min and 7 breaths/min, respectively.

A gradient method for the quantitative analysis of cell movement and tissue flow and its application to the analysis of multicellular Dictyostelium development.

We describe the application of a novel image processing method, which allows quantitative analysis of cell and tissue movement in a series of digitized video images. The result is a vector velocity field showing average direction and velocity of movement for every pixel in the frame. We apply this method to the analysis of cell movement during different stages of the Dictyostelium developmental cycle. We analysed time-lapse video recordings of cell movement in single cells, mounds and slugs. The program can correctly assess the speed and direction of movement of either unlabelled or labelled cells in a time series of video images depending on the illumination conditions. Our analysis of cell movement during multicellular development shows that the entire morphogenesis of Dictyostelium is characterized by rotational cell movement. The analysis of cell and tissue movement by the velocity field method should be applicable to the analysis of morphogenetic processes in other systems such as gastrulation and neurulation in vertebrate embryos.

Turbulent decomposition of chemical waves by spontaneously induced hydrodynamic oscillation.

The dynamic evolution of a chemical reaction-diffusion pattern and its interaction with hydrodynamic flow is investigated by two-dimensional velocimetry and spectrophotometry based on microscope video imaging techniques. Oscillatory deformation and turbulent decomposition of chemical wave fronts are observed which are induced by a pronounced oscillatory flow excited spontaneously in a Belousov-Zhabotinsky solution layer with a free surface.