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

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

A new type of respiratory inductive plethysmography (RIP) has keen designed based on digital demodulation technique with equal relative error. Compared with former amplitude demodulation, digital modulation RIP can obtain more accurate measurements of respiration and reduce the signal interference and distortion. But the system's power consumption is still a problem which needs to be solved in the future design.
Plethysmography ; methods ; Signal Processing, Computer-Assisted ; Tidal Volume

The value of the noninvasive diagnostic methods for vascular disease is worthy of emphasis. In many studies, the diagnostic abnormal findings of the vascular disease were reported. But there were a few studies for normal human vasculatures measuring with noninvasive diagnostic methods. And more, there is few data for vasculature of Oriental people, especially of the Korean population. The authors examed 20 healthy persons without any vascular disease by using the noninvasive vascular diagnostic tool-duplex scan and air plethysmography. The knowledge of the normal data of human vasculature, especially Korean population, will improve the sensitivity and specificity of the noninvasive vascular diagnostic methods. It is not appropriate to presume that this report with analysis of only 20 cases represent the normal data of Korean population. Further collection of the data is needed to define the normal data of vasculature of Korean population.
Blood Vessels ; Hemodynamics ; Humans ; Plethysmography ; Sensitivity and Specificity ; Vascular Diseases

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.

Animals ; Body Temperature ; Mice ; Plethysmography, Whole Body ; Pressure ; Temperature

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 wearable respiratory inductive plethysmograph(RIP) system is a non-intrusive respiratory monitoring system. Sleep monitoring was performed on 9 human subjects suspected of having sleep apnea hypersomnolence syndrome (SAHS) and 7 healthy volunteers using both the wearable RIP system and the conventional polysomnography(PSG), and the sensitivity and specificity of the wearable RIP system were analyzed by comparison with the PSG results. According to the characteristic of the wearable RIP system in detecting sleep apnea/hypopnea event, the diagnostic criteria of sleep apnea/hypopnea event were put forward. All subjects with SAHS diagnosed by the wearable RIP were confirmed by PSG,the sensitivity and specificity of the wearable RIP system for detecting sleep apnea/hypopnea events were 99.0% and 94.6% respectively. The wearable RIP system can be used reliably in detecting sleep apnea/hypopnea events. This system can be used at home for detecting the sleep apnea/hypopnea events non-intrusively.
Equipment Design ; Humans ; Plethysmography ; instrumentation ; methods ; Polysomnography ; instrumentation ; methods ; Sleep Apnea Syndromes ; diagnosis ; physiopathology

OBJECTIVETo investigate the differential value of inhaled volume and exhaled volume in anesthesia mice, and its effect on the pressure change inside of plethysmograph.

METHODSPressure and temperature in head chamber of double-chamber plethysmograph were tested when mice were placed in the body chamber. The differential values of inhaled volume and exhaled volume of mice were calculated.

RESULTThe baseline pressure in head chamber increased with temperature rising within 12 minutes, then went down though temperature remained high. The inhaled volumes of 8 mice were (0.2842 + or - 0.0173)ml,and the differential value of inhaled volume and exhaled volume was (0.0012 + or - 0.0002)ml.

CONCLUSIONThe inhaled volume is larger than exhaled volume, which makes pressure baseline of plethysmograph decreased. The differential value may be generated from respiratory quotient.

Animals ; Exhalation ; physiology ; Inhalation ; physiology ; Mice ; Plethysmography ; Pressure ; Temperature ; Tidal Volume ; Vital Capacity ; physiology

BACKGROUND: Although impaired endothelial function is well known in patients with diabetes mellitus, the precise mechanism and the factors that contribute to this dysfunction remain to be clarified. We examined the effect of acute hyperglycemia on patients with impaired glucose metabolism in vivo by plethysmography. METHODS: Seven patients with diabetes mellitus or impaired glucose metabolism were studied. In each patient, endothelial function was examined in the fasting state and at two levels of hyperglycemia, which were achieved by the infusion of glucose, insulin, and somatostatin. Forearm blood flow was measured while acetylcholine was infused in increasing concentrations(7.5, 15, and 30 microgram/min) through the brachial artery. RESULTS: Glucose concentrations increased accordingly at each stage, from 135.3+/-18.4 mg/dl at stage 1(the fasting state), to 239.0+/-15.2 mg/dl at stage 2(the first level of hyperglycemia), and to 378.3+/-25.3 at stage 3 (the second level of hyperglycemia) [p<0.01]. Maximal acetylcholine-dependent vasodilation achieved by infusion of acetylcholine at 30 microgram/min was significantly aftenuated during stages 2 and 3 compared with stage 1(p<0.05 by AVOVA; forearm blood flow ratio was 2.87+/-0.18 and 2.56+/-0.14 versus 3.58+/-0.21, respectively). This was also evident during the infusion of 15 microgram/min and 7.5 microgram/min of acetylcholine. CONCLUSIONS: Endothelium-dependent vasodilation is significantly aftenuated by acute hyperglycemia in patients with diabetes mellitus or impaired glucose metabolism. Our findings suggest that elevated glucose may contribute to the endothelial dysfunction observed in patients with diabetes mellitus or impaired glucose metabolism.
Acetylcholine ; Brachial Artery ; Diabetes Mellitus* ; Endothelium ; Fasting ; Forearm ; Glucose* ; Humans ; Hyperglycemia* ; Insulin ; Metabolism* ; Plethysmography ; Somatostatin ; Vasodilation*