K. Yamakoshi

New oscillometric method for indirect measurement of systolic and mean arterial pressure in the human finger. Part 1: model experiment.

To analyse the mechanism of the occurrence of the maximum volume pulsation in an artery during the application of counterpressure, the static, and dynamic pressure-volume (P-V) relationship was measured in excised arterial segments placed in a compression chamber. Teh volume change caused by perfusing the segment with a sinusoidal pump was detected by an infrared photoelectric plethysmograph during the application of counterpressure. It was revealed that the characteristic change in the amplitude of volume pulsation in response to the gradual change in the counterpressure was due to the nonlinearity of the P-V relation of the artery, and that the value of the counterpressure showing the maximum pulsation amplitude was coincided with the mean arterial pressure. From this evidence it was concluded that the maximum volume pulsation occurs when the transmural pressure was equal to zero, i.e. the arterial wall isunloaded. Based on the results a new oscillometric method for the indirect measurement of systolic and mean arterial pressure in an arterial segment was designed. Through the comparison of data with the actual pressure produced by perfusing the segment, it was demonstrated that systolic and mean arterial pressure can be indirectly measured by this technique within ±3 mm Hg error.

New oscillometric method for indirect measurement of systolic and mean arterial pressure in the human finger, Part 2; correlation study

With a new oscillometric method equipped with a transmittance infrared photoelectric plethysmograph, indirect systolic, and mean arterial pressures were measured in 12 normotensive and hypertensive subjects with systolic and mean arterial pressures ranging from 55 to 163 mmHg and from 95 to 200 mmHg, respectively. The pressure values obtained by this method were compared with direct measurements of the brachial intra-arterial pressure recorded simultaneously. A fairly good correlation between the pairs of simultaneous data from these two methods were obtained.

New technique for time series analysis combining the maximum entropy method and non-linear least squares method: its value in heart rate variability analysis.

A new technique for time series analysis, which is a combination of the maximum entropy method (MEM) for spectral analysis and the non-linear least squares method (LSM) for fitting analysis, is described. In this technique, the MEM power spectral density (MEMPSD) is calculated using a very large lag that could diminish the lag dependence of dominant periods estimated by the MEM analysis. The validity of this large lag is confirmed by the LSM, given that the ten dominant MEM periods are known quantities. To validate the MEM plus LSM technique, it is compared with autoregressive (AR) modelling, by analysing heart rate variability under pharmacological interventions (phenylephrine and trinitroglycerine), using 16 young males. The results indicate that the MEMPSD, when compared with the ARPSD, has numerous periods that could reproduce the original time series much more accurately, as revealed by the LSM analysis. However, both the low- and high-frequency powers with MEMPSD and ARPSDs shift in the expected directions in accordance with the pharmacological effects on the cardiovascular system. The implications of these results are discussed from the theoretical and practical standpoints of the MEM plus LSM technique, compared with AR modelling.

A portable instrument for non-invasive monitoring of beat-by-beat cardiovascular haemodynamic parameters based on the volume-compensation and electrical-admittance method

A new, portable instrument has been developed for simultaneous monitoring of blood pressure, cardiac output and other cardiovascular haemodynamic variables. The measurements are based on the volume-compensation method and the transthoracic electrical admittance method. The instrument is small and light and can be carried by the subject. The portable unit controls the measurement procedures, performs the blood pressure and cardiac output measurement, processes signals and stores almost 32 000 beats of time-series data in a fully automated manner. A conventional personal computer is used to initialise the measurement system, and to reproduce and evaluate the measurement data. The measurement system provides a means to evaluate in detail, without restriction, the subjects cardiovascular haemodynamic responses to daily physical activities as well as to various psycho-physiological stresses. The paper describes a new, portable, cardiovascular haemodynamic instrument and in-the-field test results. Twelve subjects are monitored for trials, 60–210 min, and fewer than 3% of the data in each trial are artifactuel. Artefacts are due mainly to body movements.

A new portable device for ambulatory monitoring of human posture and walking velocity using miniature accelerometers and gyroscope

Measurement of physical activity is one of the key subjects in the field of ambulatory cardiovascular monitoring using such as Holter ECG and so called ambulatory blood pressure monitor (ABPM). Rehabilitation and gerontology will also be another fields for the application of the activity monitor. From this point of view, we have developed a portable device for monitoring human posture and walking velocity in ambulatory subjects. In this paper are described, a new sensor system for this purpose using three accelerometers and one gyroscope, its availability for the accurate measurement of human posture and walking velocity, and results of preliminary study using a prototype system for ambulatory monitoring.

Noninvasive automatic monitoring of instantaneous arterial blood pressure using the vascular unloading technique

For the noninvasive monitoring of the beat-to-beat systolic and diastolic pressure and pressure waveform in the human finger, a new automated instrument was designed. This measurement is based on a principle called the vascular unloading technique. Using a hydraulic servocontrol system, the vascular volume change caused by intra-arterial pressure change can be compensated by applying counter pressure to maintain a constant vascular volume in the unloaded state. In this state the controlled counterpressure instantaneously follows the intra-arterial pressure. In this instrument all the necessary procedures, such as the setting of the reference value for the servocontrol, control of the servogain, processing and displaying of the data on a recorder, were carried out automatically. The simultaneous comparison of data with direct measurements and a few examples of the indirect pressure recordings by this instrument are shown and the principles, operation and evaluation of this method are described. This instrument was shown to permit the nonivasive and accurate tracking of instantaneous arterial pressure and to perform acceptably over a wide range of arterial pressure.

Electric impedance cuff for the indirect measurement of blood pressure and volume elastic modulus in human limb and finger arteries

AbstractA new plethysmograph, the electric impedance cuff, was designed for the indirect measurement of blood pressure, volume elastic modulus Ev and compliance Ca in human limb arteries. This comprises a compression chamber filled with electrolyte solution and a tetrapolar electric impedance plethysmograph whose electrodes are placed inside the chamber; the former for controlling transmural arterial pressure Pt, and the latter for detecting total limb volume Vo, mean arterial volumen

A Preliminary Study on Driver's Stress Index Using a New Method Based on Differential Skin Temperature Measurement

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