No abstract available.
Electric Impedance* ; Plethysmography, Impedance*

A double feedback current source for biologic impedance measurement is designed in order to solve the problem on the poor constant-current characteristic under higher frequency and meet the request for the ability to eliminate the direct current signal. The voltage controlled current source based on the second generation current conveyor theory is presented, which has good output impedance and anti-direct current characteristics by using the direct current feedback unit and input buffer. The closed loop control of current amplitude is implemented by means of the direct digital synthesizer and multiplication demodulation technique, which improves the constant-current characteristic of the current source.
Equipment Design ; Plethysmography, Impedance ; instrumentation

OBJECTIVE: To investigate the diagnostic validity of doppler ultrasonography (US) and impedance plethysmography (IPG) using photoplethysmography for evaluation of varicose vein of the lower extremities. METHOD: One hundred sixty-six limbs in 83 consecutive patients with varicose vein were included. Venous reflux and deep venous lesions were assessed by doppler US. Venous filling time was evaluated using IPG. Diagnostic capabilities of two methods were analyzed using Receiver Operating Characteristic (ROC) curve. RESULTS: Doppler US identified superficial venous reflux in sixty-nine of 119 limbs with varicose vein and no abnor malities in 34 of 47 normal limbs (sensitivity, 58%; specifi-city, 75%). IPG demonstrated superficial venous insufficiency in 75 of the affected limbs and normal refill time in 38 of the normal limbs (sensitivity, 63%; specificity, 81%). Sensitivity was increased to 82% when both tests were used together. Area under the ROC curve was 0.66 in doppler US, 0.72 in IPG, and 0.76 in both tests. Deep venous lesion was found in 31 limbs using the both tests; 15 limbs with doppler US and 18 limbs with IPG. CONCLUSION: IPG was more superior to doppler US in diagnosing venous insufficiency. The combination of both tests provided more accurate diagnostic information in assessing venous valvular function
Electric Impedance* ; Extremities ; Humans ; Lower Extremity* ; Photoplethysmography ; Plethysmography ; Plethysmography, Impedance* ; ROC Curve ; Sensitivity and Specificity ; Ultrasonography ; Ultrasonography, Doppler* ; Varicose Veins* ; Venous Insufficiency

The current emphasis on the acquisition of physiological data by noninvasive means for mass medical screening and patient monitoring has increased interest in the use of electrical impedance for the measurement of physiological events. The technique has gained some degree of acceptance for monitoring respiration (Baker and Geddes, 1970), and much interest has been displayed recently in use of the technique to measure cardiac output including studies by Kubicek et al. (1966) Judy et al. (1969), and Mohapatra (1981). Other applications using the impedance technique include thoracic fluid accumulation, peripheral blood flow, cerebral blood flow, muscle contraction, eye movement, and uterine contraction, etc. The purpose of this article is to introduce the various impedance techniques for the measurement of physiological variables.
Cardiography, Impedance ; Cerebrovascular Circulation ; Extremities/blood supply ; Female ; Human ; *Plethysmography, Impedance ; Regional Blood Flow ; Respiration ; Uterine Contraction

Studying rheography of 32 patients with cerebrovascular insufficient treated by artificial magnetic fields at Central Military Hospital from June to December 2002. Results: treating by artificial magnetic fields gave significant improvements on the rheographic index such as reduce of  time and normalization of /T ratio, increase of Ri index and cerebrovascular volume to normal levels; artificial magnetic fields also improved imagines of rheographic waves. These results demonstrated the improvements in regulation of vascular tonicity, and promoting blood flow at treated areas
Plethysmography, Impedance ; Cerebrovascular Disorders ; Therapeutics ; Magnetics

The in vivo techniques for studying human body composition have built up an important field and are continuing to be developed. This review provides an overview of the present status of this field and describes the in vivo techniques used in mearsuring human body composition such as anthropometry, metabolites method, densitometry, dilution method, total body potassium, neutron activation analysis, bioelectrical impedance analysis, dual energy X ray absorptiometry and imaging method. The review also introduces the principle, method and value of these techniques.
Anthropometry ; methods ; Body Composition ; Densitometry ; methods ; Humans ; Magnetic Resonance Spectroscopy ; methods ; Plethysmography, Impedance ; methods ; Whole Body Imaging ; methods

OBJECTIVETo observe temperature and pressure changes inside plethysmograph produced by body temperature of anesthetized mice.

METHODSThe temperature and pressure changes inside whole body plethysmograph generated from anesthetized mice were compared with those from dead mice. The temperature and pressure changes inside body chamber and head chamber of double-chamber with anesthetized mice in body chamber were synchronously measured. The respiratory frequencies and amplitudes of mice inside two kinds of head-out plethysmographs were synchronously measured. One of these two plethysmographs kept sealed all the time and the other was opened to the atmosphere for 1 min every 2 min.

RESULTTemperature and pressure of air in the anesthetized mice chamber increased 1.18 degree and 2.710 mmHg within 6 min, and data from dead mice were 1.17 degree and 2.671 mmHg. There were no significant differences between these two groups. The temperature inside body chamber increased 1.92 degree in 20 min and the pressure was 5.554 mmHg, which were significantly higher than those of head chamber (0.09 degree and 0.627 mmHg). The respiratory frequencies of mice in the sealed head-out plethysmograph increased from 125.04 per min to 168.45 per min, and amplitudes of pressure changes generated from mice breath decreased from 1.090 mmHg to 0.883 mmHg. Significant differences occurred between different observation time points. Meanwhile respiratory frequencies in the open head-out plethysmograph were around 120 per min and amplitude of pressure changes kept about 1 mmHg. There were no significant differences between different time points.

CONCLUSIONIncrease of temperature and pressure inside pressure whole-body plethysmograph are mainly from body temperature of mice, and the increased pressure significantly influences respiration of mice.

In this paper, a simulation research software platform for EIT electrode structure and parameter optimizing design has been developed, which is based on the coercive equipotential node model of line electrode. By the method, which is presented for electrode structure and parameter optimizing design, the influences of electrode structure parameters on reconstructed image and measure sensitivity have been studied and the optimal structure parameters of electrode for the object in different depth have been determined.
Computer Simulation ; Electric Impedance ; Electrodes ; Electromagnetic Fields ; Equipment Design ; Humans ; Models, Biological ; Plethysmography, Impedance ; instrumentation ; methods ; Software ; Tomography ; methods

BACLGROUND: It is essential to evaluate hemodynamics of vascular disease in addition to anatomic details. It has been known that the plethysmography represents intravascular(arterial or venous) volume or pressure. Photoplethysmography(PPG) is convenient to use and has been widely used for measurement of venous refill time(VRT). However, it has not been used for evaluation of venous function. OBJECTIVE: Our study aims at testing the feasibility of evaluation of venous function using PPG. METHODS: The maneuver established for air PG was slightly modified and applied for the PPG. The test was performed with the object seated in a chair and the legs dependent. The PPG probe was attached to the limbs within 5 cm from medial malleolus. After standardized procedure of leg-raising, putting the leg in dependent position, 1 tip-toe exercise, and 10 tip-toe exercises, the measured parameters were initial emptying time(E1), amount of volume change(V1), refilling time by hydrostatic pressure(F1), refilling time after 1 tip-toe exercise(F2), and ejected volume(V2) and refilling time after 10tip-toe exercises(F3).
Exercise ; Extremities ; Hemodynamics ; Hydrostatic Pressure ; Leg ; Photoplethysmography ; Plethysmography ; Vascular Diseases ; Veins

Piglets having each a body weight of 20-30 kg and an abdominal perimeter like human's were used in the experiment. Being guided by ultrasound, we stabbed the piglet's abdomen, placed a catheter on the liver's lower margin, then injected the anticoagulated blood through the catheter by electrical infusion pump with constant speed respectively, and monitored the whole process by EIT. We observed the image change, using Ultrasound and CT to examine the area of blood injection after the end of monitoring,and we dissected to check the result of observations. The results reveal: (1) Ultrasound, CT and dissection are all able to find out a large amount of blood in piglet's abdominal cavity; (2) The pixel value of EIT target area decreases with the increase of blood, and the change in impedance image can be obviously observed. Therefore, this animal model is suitable for simulating intraperitoneal bleeding, and the speed of bleeding therein can be controlled. We can get a limpid image when EIT is used for monitoring the intraperitoneal bleeding simulated by this animal model.
Animals ; Electric Impedance ; Female ; Hemorrhage ; diagnosis ; etiology ; physiopathology ; Image Interpretation, Computer-Assisted ; methods ; Male ; Monitoring, Physiologic ; methods ; Peritoneal Diseases ; diagnosis ; etiology ; physiopathology ; Plethysmography, Impedance ; methods ; Swine ; Tomography ; methods