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  • 1
    Electronic Resource
    Electronic Resource
    Verification of Fourier phase and amplitude values from simulated heart motion using a hydrodynamic cardiac model (1986)
    Springer
    European journal of nuclear medicine 11 (1986), S. 375-380 
    Details
    ISSN: 1619-7089
    Keywords: Fourier analysis ; Cardiac phantom model ; Artificial heart
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Using pusher-plate-type artificial hearts, changes in the degree of synchrony and stroke volume were compared to phase and amplitude calculations from the first Fourier component of individual-pixel time-activity curves generated from gated radionuclide images (RNA) of these hearts. In addition, the ability of Fourier analysis to quantify paradoxical volume shifts was tested using a ventricular aneurysm model by which the Fourier amplitude was correlated to known increments of paradoxical volume. Predetermined phase-angle differences (incremental increases in asynchrony) and the mean phase-angle difference calculated from RNAs showed an agreement of -7°±4.4° (mean ±SD). A strong correlation was noted between stroke volume and Fourier amplitude (r=0.98; P〈0.0001) as well as between the paradoxical volume accepted by the ‘aneurysm’ and the Fourier amplitude (r=0.97; P〈0.0001). The degree of asynchrony and changes in stroke volume were accurately reflected by the Fourier phase and amplitude values, respectively. In the specific case of ventricular aneurysms, the data demonstrate that using this method, the paradoxically moving areas may be localized, and the expansile volume within these regions can be quantified.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00261400
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  • 2
    Electronic Resource
    Electronic Resource
    Mechanical circulatory support devices for bridge to heart transplantation, bridge to recovery, or destination therapy (2000)
    Springer
    Journal of artificial organs 3 (2000), S. 75-84 
    Details
    ISSN: 1619-0904
    Keywords: Ventricular assist device (VAD) ; Total artificial heart (TAH) ; Heart transplantation ; Bridge to transplantation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Both the ventricular assist device (VAD) and the total artificial heart (TAH) have been effective in supporting circulation of end-stage cardiac patients and in bridging to heart transplantation. However, because of a shortage of donor hearts and age limitations, destination therapy with the completely implantable VAD has also been started. The totally implantable TAH in the United States is in the final stage of development and will go into preclinical trials in 2004. In Japan, heart transplantation has been re-instituted since last year, but because of shortages of donor hearts the waiting time prior to transplantation is fairly long. To date, six heart transplantations have been carried out, of which four have been bridged transplantations, using extracorporeal or implantable VADs. With the extracorporeal VADs, patients cannot be discharge home, which increases the hospital expenses. With the implantable VADs such as Novacor and HeartMate imported from the USA, patients can be discharged home, but major threats with these devices are thromboembolic, complications and infection. These devices are also fairly large, being designed for 80-kg patients, and are thus difficult to implant in patients of 50 to 60 kg, including women. Because of these limitations, there is a strong clinical demand for a compact, high-performance, implantable, permanent-use VAD. This paper addresses the current status of the artificial heart research and development program at the Tokyo Medical and Dental University, which was started in May 1999.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02479969
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  • 3
    Electronic Resource
    Electronic Resource
    Experimental and clinical evaluation of a noninvasive reflectance pulse oximeter sensor (1992)
    Springer
    Journal of clinical monitoring and computing 8 (1992), S. 257-266 
    Details
    ISSN: 1573-2614
    Keywords: Monitoring: pulse oximetry ; Measurement techniques: pulse oximetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract The objective of this study was to evaluate a new reflectance pulse oximeter sensor. The prototype sensor consists of 8 light-emitting diode (LED) chips (4 at 665 nm and 4 at 820 nm) and a photodiode chip mounted on a single substrate. The 4 LED chips for each wavelength are spaced at 90-degree intervals around the substrate and at an equal radial distance from the photodiode chip. An optical barrier between the photodiode and LED chips prevents a direct coupling effect between them. Near-infrared LEDs (940 nm) in the sensor warm the tissue. The microthermocouple mounted on the sensor surface measures the temperature of the skin-sensor interface and maintains it at a preset level by servoregulating the current in the 940-nm LEDs. An animal study and a clinical study were performed. In the animal study, 5 mongrel dogs (weight, 10–20 kg) were anesthetized, mechanically ventilated, and cannulated. In each animal, arterial oxygen saturation (SaO2) was measured continuously by a standard transmission oximeter probe placed on the dog's earlobe and a reflectance oximeter sensor placed on the dog's tongue. In the first phase of the experiment, signals from the reflectance sensor were recorded while the dog was immersed in ice water until its body temperature decreased to 30°C. In the second phase, the animal's body temperature was normal, and the oxygen content of the ventilator was varied to alter the SaO2. In the clinical study, 18 critically ill patients were monitored perioperatively with the prototype reflectance sensor. The first phase of the study investigated the relationship between local skin temperature and the accuracy of oximeter readings with the reflectance sensor. Each measurement was taken at a high saturation level as a function of local skin temperature. The second phase of the study compared measurements of oxygen saturation by a reflectance oximeter (SpO2[r]) with those made by a co-oximeter (SaO2[IL]) and a standard transmission oximeter (SpO2[t]). Linear regression analysis was used to determine the degree of correlation between (1) the pulse amplitude and skin temperature; (2) SpO2(r) and SaO2(IL); and (3) SpO2(t) and SaO2(IL). Student'st test was used to determine the significance of each correlation. The mean and standard deviation of the differences were also computed. In the animal study, pulse amplitude levels increased concomitantly with skin temperature (at 665 nm,r=0.9424; at 820 nm,r=0.9834;p〈0.001) and SpO2(r) correlated well with SaO2(IL) (r=0.982; SEE=2.54%;p〈0.001). The results of the clinical study are consistent with these findings. The proto-type reflectance pulse oximeter sensor can yield accurate measurements of oxygen saturation when applied to the forehead or cheek. It is, therefore, an effective alternative to transmission oximeters for perioperative monitoring of critically ill patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01617907
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  • 4
    Electronic Resource
    Electronic Resource
    Clinical evaluation of the oscillometric blood pressure monitor in adults and children based on the 1992 AAMI SP-10 standards (1995)
    Springer
    Journal of clinical monitoring and computing 11 (1995), S. 123-130 
    Details
    ISSN: 1573-2614
    Keywords: Noninvasive blood pressure monitor ; Oscillometric sphygmomanometer ; Auscultatory blood pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract Objective and Methods. A noninvasive blood pressure monitor (model BP8800MS, Colin Medical Instruments Corp., San Antonio, TX) that uses the oscillometric principle was evaluated against the manual auscultatory method in 85 adults and 85 children following the requirements of the 1992 AAMI SP-10 standard. This was the first evaluation study of the electronic sphygmomanometers according to the new AAMI standards.Results. In adult subjects, the mean difference and standard deviation of the differences between the oscillometric and auscultatory methods were 2.81 ± 5.35 mm Hg (mean ± SD) for systolic and 0.04 ± 4.90 mm Hg for diastolic; in children, they were 3.18 ± 5.96 mm Hg for systolic and −0.82 ± 5.24 mm Hg for diastolic. Excellent correlation between the oscillometric and auscultatory methods, particularly the diastolic pressure, is due to usage of the Phase V Korotkoff's sounds for auscultatory detection of the diastolic pressure, increased accuracy of the two observers' measurements, and proper selection of cuff sizes depending on the mid-arm circumference. Five different-sized cuffs were used in this study. The cuff-width-to-midarm circumference ratio was adjusted to be 0.4 or larger to minimize the measurement error associated with mismatch of cuff-size/arm-size relationship. The distribution of errors associated with each cuff was nearly the same.Conclusions. The 1992 AAMI SP-10 standards offer a thorough evaluation of the oscillometric sphygmomanometer by enforcing more stringent criteria on (1) agreement between two observers, (2) wide spectrum of blood pressure from hypertensive (above 180 mm Hg) to hypotensive, and (3) data analysis. The oscillometric blood pressure monitor evaluated in this study meets the specifications of the new AAMI SP-10 standards and can offer an accurate, automatic, and noninvasive measure of both systolic and diastolic blood pressure in adults and children. It can safely replace the manual or automatic auscultatory system in various clinical settings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01617734
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  • 5
    Electronic Resource
    Electronic Resource
    A noninvasive tissue reflectance oximeter (1980)
    Springer
    Annals of biomedical engineering 8 (1980), S. 1-15 
    Details
    ISSN: 1573-9686
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract A newly developed noninvasive tissue reflectance oximeter utilizes 5 light emitting diodes operating at the wavelengths of 0.635, 0.665, 0.795, 0.910, and 0.955 μ, and photodiodes to sample the tissue reflectance spectra. Since the tissue reflectance is affected by changes in both hemoglobin content (Hb T) and hemoglobin oxygen saturation (OS T),Hb T is first determined using the reflectance at 0.795 μ. The hemoglobinOS T is then estimated using the reflectances at the 5 wavelengths in conjunction with the diffuse reflectance equation which has previously been verified applicable to tissue reflectance oximetry. A quantitative estimation of bothHb T andOS T in intestinal mucosa of dogs obtained using this instrument showed thatHb T values agreed fairly well with those of others and that the standard errors ofOS T were around 5.0% inOS as compared with theOS values of blood samples for minimized arterial-venousOS differences. The continuous on-line measurement ofHb T andOS T should be possible using the reflectance technique and should be valuable for clinical evaluation of the patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02363167
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