Tomohisa Mikami

Effect of reducing the shell area on the respiratory properties of chicken embryonic blood.

Abstract In hen eggs, the effect of reducing the shell area available for respiration on gas exchange in chicken embryonic blood has been studied. Gas exchange through the shell over either the air space or the narrow end was blocked by coating about one-fourth of the total shell surface with epoxy cement. P O 2 , P CO 2 , pH and Hct in the chorioallantoic venous blood were simultaneously measured at days 10, 12, 14,16 and 18. [HCO − 3 ], total-CO 2 , content in plasma and base excess were graphically determined. The respiratory parameters determined were significantly different between control group and coated groups, while the difference between the two coated groups was not statistically significant. The hatchability in coated groups was very poor and a few embryos died even after reaching the air by pipping. Thus, it appears that such embryos near hatching encounter physiologically critical limits concerning blood gas metabolism. No difference could be established in the contribution to the gas exchange between the shell area of the narrow end and the area over the air space.

Respiratory properties of chicken embryonic blood during development

Abstract Blood P O2 , P CO 2 and pH and Hct of chorioallantoic vein and artery in chicken embryos were simultaneously measured, and [HCO3−3], total-CO2 content in plasma and base excess were determined graphically by plotting P CO2 , pH and calculated Hb on the Siggaard-Andersen alignment nomogram. The experiment was carried out daily from the eighth day of incubation to the 18th day. P CO2 , [HCO3−], CO2 content and base excess gradually increase with time, while blood P O2 and pH decrease during development. The differences of these parameters between vein and artery are rather large in comparison with those in the adult human being; especially they are large in the middle stage of development and they become small with time. The changes in respiratory parameters determined have close correlation with the developing embryonic weight. It is suggested that the embryo encounters respiratory alkalosis with metabolic acidosis in the middle stage of development, and then the acid-base status approaches normal level with time.

An Optimally Controlled Respirator

An optimally controlled respirator was developed. It has three main features: 1) ventilation is controlled by the patients metabolic rate from continuously measured C0 2 output, 2) physiologic dead space approximated as a linear function of tidal volume is used to estimate alveolar ventilation, and 3) respiratory rate is computed to minimize ventilatory work.

Measurements of dental cast profile and three-dimensional tooth movement during orthodontic treatment

A system developed for measuring three-dimensional profiles of dental casts and three-dimensional tooth movement during orthodontic treatment is described. The profile measurement is based on a triangulation method which detects a laser spot on a cast using an image sensor. The system is computer-controlled and designed to achieve the depth and lateral resolutions of 0.05 mm and 0.1 mm, respectively, within a depth range of 25 mm. The movements of teeth, including rotations, were obtained by means of three-dimensional registration of tooth profiles using a computer between casts that were serially taken at different stages of the treatment. Measurements on patients over periods of 70 to 190 days revealed that this technique is capable of quantifying the difference in movements due to orthodontic therapeutics.<<ETX>>

Development of an implantable motor-driven assist pump system

A motor-driven artificial pump and its transcutaneous energy transmission (TET) system are discussed. The artificial pump consists of a high-speed DC brushless motor driving a ball screw and magnetic coupling mechanism between the blood pump and ball screw. The ball screw transfers high-speed rotary motion into low-speed rectilinear motion by a single component. Magnetic coupling enables active blood filling without applying an excess negative pressure to the pump. The transcutaneous transformer is formed from a pair of concave/convex ferrite cores. This design minimizes lateral motion of the external core. Information on motor voltage is transmitted through the skin by infrared pulses. The motor voltage is regulated by controlling the duty ratio of the square pulse supplied to the primary coil. Pump flow of 5.6 l/min was obtained with a mean outlet pressure of 100 mm Hg at a drive rate of 100 b.p.m. under preload of 15 mm Hg.<<ETX>>

In vivo viscoelastic behavior in the human aorta.

To characterize the viscoelastic properties of the human aorta in vivo, the pressure-diameter relation was determined in the abdominal aorta in 15 subjects. Diameter was measured noninvasively with a highly sensitive ultrasonic displacement meter, while intra-aortic pressure was measured with a catheter tip micromanometer inserted from the femoral artery. The frequency-dependent changes in the pressure-strain modulus (Ep) of the aorta and the phase lag of diameter to pressure were calculated by frequency analysis of these wave forms at the mean blood pressure of 109 mm Hg. The Ep and the phase lag at the fundamental frequency component (1.2 +/- 0.3 Hz, mean +/- SD) were (1.52 +/- 0.57) x 10(6) dyne/cm2 and -6.7 degrees +/- 2.1 degrees, respectively. Although the phase lag at the fundamental frequency was in good agreement with the published in vitro data, the calculated phase lags above the second harmonic were inconsistent, which was probably due to the nonlinearity in the pressure-diameter relation. To separate the effect of this nonlinearity, analysis was conducted with a model consisting of a static nonlinear component representing the elasticity and a dynamic linear component representing the viscosity. This method of analysis revealed that the phase lag due to the viscous component provided relatively flat frequency response to the 10th harmonic. It was confirmed that the aortic wall viscosity showed no apparent difference between the in vivo and the in vitro experimental conditions.

Development of a Ceramic Heart Valve

A durable and thromboresistant ceramic heart valve comprised of a single crystal alumina disk and titanium nitride (TiN) valve ring has been developed. Blood compatiblity was examined by scanning electron microscopy (SEM) examinations of the valves implanted in sheep for 35 (#1), 26 (#2), 20 (#3), 23 (#4), and 26 (#5) days. The single crystal alumina and TiN surfaces were free of platelet aggregation or fibrin networks, except for some depositions of fibrin and platelets on the outflow TiN ring in #3, and isolated red cells on the outflow TiN ring in #5. Durability testing under high pressure (1750 mmHg = 233 KPa) pulsatile conditions showed that the safety factor of the ceramic valve was more than seven times greater than anticipated. The ceramic valve is promising as an artificial heart valve.

Arteriosclerotic change in the human abdominal aorta in vivo in relation to coronary heart disease and risk factors

In 137 living subjects, arteriosclerotic change in the human abdominal aorta was examined in relation to coronary heart disease (CHD) using a new ultrasonic method. The pressure strain elastic modulus (Ep) was calculated as an index of elastic properties from which arteriosclerotic change in the aorta was estimated. Thirty-one patients with CHD and 36 subjects with hypertension showed progression of the arteriosclerotic change in the abdominal aorta compared with 70 normal controls with the same age distribution (40-60 yrs). The Ep values were 1.03 +/- 0.27 X 10(6) dyne/cm2 in the normal group, and were elevated significantly (P less than 0.001) to 1.81 +/- 0.55 X 10(6) dyne/cm2 in the CHD group, and 1.95 +/- 1.31 X 10(6) dyne/cm2 in the hypertensive group. A significant correlation (r = 0.49, P less than 0.01) between the Ep values of the abdominal aorta and serum total cholesterol was observed in the CHD group. It was shown in living human subjects that the progression of arteriosclerotic change in the abdominal aorta was associated with coronary heart disease, and that some coronary risk factors, such as hypertension and serum total cholesterol, also affected arteriosclerotic change in the abdominal aorta.

Online computer for assessing respiratory and metabolic function during exercise

A microcomputer-based system for the breath-by-breath assessment of respiratory and metabolic function during exercise was developed. To minimise the load for subjects ventilation was measured by use of an impedance plethysmograph instead of a pneumotachograph. The computer calculated respiratory frequency, tidal volume, minute ventilation, end-tidal pO2 and pCO2, O2 input and CO2 output, and gas exchange ratio of each breath from the impedance pneumogram and the gas composition of the expired air. To avoid the error due to the cardiogenic oscillations appearing to overlap the impedance pneumogram, discrimination of the inspiratory and expiratory phases was achieved by detecting the temperature difference between ambient and expired air. The impedance pneumogram could follow tidal volume variations during a moderate bicycle exercise (120 W) with satisfactory accuracy, but its sensitivity is apt to fall at the severe exercise (180 W). Possible factors causing errors such as the distribution of regional ventilation and perfusion during exercise are discussed.

Effect of flow disturbances remaining at the beginning of diastole on intraventricular diastolic flow and colour M-mode Doppler echocardiograms

A computational model of the fluid dynamics of intraventricular flow was used to investigate the importance of the effects of flow disturbances existing within the left ventricle (LV) at the onset of diastole on a diastolic flow field. The simulation started with a quiescent flow state; it continued for a number of cardiac cycles to obtain a cyclically repeatable flow. After the flow became periodic, the initial diastolic flow was not quiescent: flow disturbances, remnants of a systolic flow, were present within the LV. Nevertheless, they faded away during an acceleration phase of diastole and almost ceased by the end of this phase. Consequently, a flow field during a deceleration phase of diastole, characterised by the formation of a vortex ring, was hardly affected by the initial flow disturbances. The propagation velocity of a colour M-mode Doppler echocardiogram obtained by scanning velocity along the LV long axis was 0.58ms−1 in the case where diastolic flow was initially quiescent and 0.56ms−1 in the case where flow disturbances existed at the beginning of diastole. These results indicated that the colour M-mode Doppler echocardiographic technique captures flow dynamics produced purely by ventricular expansion, with little influence from initial diastolic flow disturbances.