Atsushi Kawarada

E-Healthcare at an Experimental Welfare Techno House in Japan

An automated monitoring system for home health care has been designed for an experimental house in Japan called the Welfare Techno House (WTH). Automated electrocardiogram (ECG) measurements can be taken while in bed, in the bathtub, and on the toilet, without the subject’s awareness, and without using body surface electrodes. In order to evaluate this automated health monitoring system, overnight measurements were performed to monitor health status during the daily lives of both young and elderly subjects.

Long-term ambulatory monitoring of indirect arterial blood pressure using a volume-oscillometric method.

A new portable instrument equipped with a microprocessor was designed for the long-term ambulatory monitoring of indirect arterial pressure in the human finger at desired intervals using a volume-oscillometric technique. All the necessary procedures such as (1) programmed control of cuff pressure, (2) detection of the systolic end-point and the point of maximum amplitude of arterial volume pulsations, (3) reading of the cuff pressures corresponding to these two points, (4) its processing and (5) recording of the systolic and mean pressure together with heart rate on a digital memory integrated circuit were performed automatically. After the monitoring, the data were reproduced and analysed by a conventional personal computer. Simultaneous comparison of the data with direct measurement, operation and evaluation of this instrument, and ambulatory monitoring were carried out. With this instrument noninvasive and accurate monitoring of arterial pressure could be made in unrestricted subjects during daily activities.

Noninvasive automatic measurement of arterial elasticity in human fingers and rabbit forelegs using photoelectric plethysmography

A new instrument for the noninvasive measurement of arterial elastic properties such as ‘pressure-volume relationship’ and ‘volume elastic modulus’ in human fingers or in rabbit forelegs has been designed using a transmittance infra-red photoelectric plethysmography technique. The measurement and display of the results by this system is carried out automatically by use of a conventional personal computer. Using this instrument, the progressive and regressive changes in arterial elastic properties have been clearly demonstrated in the forelegs of hyperlipoedemic rabbits with experimental atherosclerosis. The effect of vasodilation by isosorbide dinitrate on the finger arteries of patients with congestive heart failure was also successfully studied. This instrument is capable of a rapid and reliable measurement of arterial elasticity and appears to be useful not only in basic cardiovascular research laboratories but also in clinics.

Indirect Measurement of Eye-Level Arterial Pressure by the Volume Oscillometric Method

Eye-level blood pressure was indirectly measured in human superficial temporal arteries with a newly designed sphygmomanometer using the volume oscillometric principle. This device comprises a reflected, infrared, photoelectric plethysmograph (RIPP) for detecting arterial volume variations and an artery compression cuff. Systolic and mean arterial pressures were determined from the cuff pressure corresponding respectively to the appearance and maximum point of the arterial volume variations. Diastolic pressure was calculated from these pressure values using a conventional equation. The pressures were corrected with respect to the hydrostatic pressure difference between the heart and eye, and compared with the data simultaneously obtained by (1) auscultation method in the brachial arteries; (2) volume compensation; and (3) a volume oscillometric method in the finger arteries. The eye-level pressure and its change were recorded during rest and exercises such as bicycle ergometry, weight lifting, Masters two-step test, and acceleration loading by a human centrifuge.

Step response analyses of the cardiovascular system and their application to the measurement of systemic and pulmonary vein compliances.

SummaryA theoretical analysis of the step response in the closed cardiovascular system induced by a sudden shift of the right cardiac output curve predicted that if the relations of the right heart output (COr) and the total systemic capillary flow (CFs) to the systemic venous pressure (Psv) are linear, then the time course ofPsv change will become monexponential with a time constant T given by T=Csv/(Gr + Gs), whereCsv is the systemic vein compliance andGr andGs are the conductances of the transientCOr - Psv andCFs - Psv relationships. A similar prediction was obtained for the time constant T of the pulmonary vein pressure (Ppv) response to the step change in the left cardiac output (COl) curve, pulmonary vein compliance (Cpv) and the conductances of theCol curve, and the pulmonary capillary flow (CFp) curve againstPpv. The actualPsv orPpv changes following sudden alteration of theCOr orCOl curve by inflation and deflation of the balloon in the right or left atrium revealed monoexponential time courses. Semilogarithmic plots of the transient vein pressure changes yielded correlation coefficients of −0.995 ± 0.006 (means ± SD) in 11 curves forPsv and 0.977 ± 0.017 in 16 curves forPpv (P<0.01). The assumed linearity of dynamicCOr andCOl curves was confirmed by beat by beatCOr - Psv andCOl - Ppv relationships during the step responses, except for the first few beats immediately after the balloon maneuver. The linearity of the dynamicCFs curve was examined by measuringCFs with a double-step balloon maneuver so as to cause rapid equilibrium betweenCOr andCFs at varied moments of the transient process. The correlation coefficient betweenCFs andPsv thus obtained was 0.98 ± 0.04 (P<0.01). A similar linearity of the dynamicCFp -Ppv relationship was suggested from their steady-state curves. The values ofCsv calculated from the experimental data were 1.70 ± 0.12 ml/mmHg/kg body wt in 11 curves and those ofCpv were 0.13 ± 0.03 ml/mmHg/kg in 15 curves. These results are mostly consistent with those previously reported.