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

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

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

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

When using pressure-type plethysmography to test lung function of rodents, calculation of lung volume is always based on Boyle's law. The precondition of Boyle's law is that perfect air is static. However, air in the chamber is flowing continuously when a rodent breathes inside the chamber. Therefore, Boyle's law, a principle of air statics, may not be appropriate for measuring pressure changes of flowing air. In this study, we deduced equations for pressure changes inside pressure-type plethysmograph and then designed three experiments to testify the theoretic deduction. The results of theoretic deduction indicated that increased pressure was generated from two sources: one was based on Boyle's law, and the other was based on the law of conservation of momentum. In the first experiment, after injecting 0.1 mL, 0.2 mL, 0.4 mL of air into the plethysmograph, the pressure inside the chamber increased sharply to a peak value, then promptly decreased to horizontal pressure. Peak values were significantly higher than the horizontal values (P<0.001). This observation revealed that flowing air made an extra effect on air pressure in the plethysmograph. In the second experiment, the same volume of air was injected into the plethysmograph at different frequencies (0, 0.5, 1, 2, 3 Hz) and pressure changes inside were measured. The results showed that, with increasing frequencies, the pressure changes in the chamber became significantly higher (P<0.001). In the third experiment, small animal ventilator and pipette were used to make two types of airflow with different functions of time. The pressure changes produced by the ventilator were significantly greater than those produced by the pipette (P<0.001). Based on the data obtained, we draw the conclusion that, the flow of air plays a role in pressure changes inside the plethysmograph, and the faster the airflow is, the higher the pressure changes reach. Furthermore, the type of airflow also influences the pressure changes.
Air Movements ; Animals ; Models, Theoretical ; Plethysmography, Whole Body ; instrumentation ; methods ; Pressure ; Rats ; Respiration

OBJECTIVECerebral electrical admittance plethysmography is a novel noninvasive technique for evaluating cerebral hemodynamics. This study aimed to measure the reference values of cerebral electrical admittance plethysmogram in healthy newborns.

METHODSBilateral cerebral electrical admittance plethysmography was performed in 40 healthy newborns.

RESULTSThe values of various indexes of cerebral electrical admittance plethysmogram in 40 newborns were obtained by this technique. The index of Admittance Differential Loop (ADL) I+II at the third and fourth days after birth was significantly higher than that at the first day of life (P < 0.05). There were significant differences in the index of ADL I+II and the ratio of Hs to b-S (Hs/ b-S) among different birth weight groups (P < 0.05). No significant differences were found in all the indexes of cerebral electrical admittance plethysmogram between the left and right brain of newborns. Gender and parturition mode had also no effects on these indexes.

CONCLUSIONSThe research reported the reference values of cerebral electrical admittance plethysmogram in healthy newborns. The postnatal age and birth weight are influencing factors for the cerebral electrical admittance plethysmogram.

Age Factors ; Birth Weight ; Cerebrovascular Circulation ; Female ; Humans ; Infant, Newborn ; Male ; Plethysmography ; methods ; Reference Values

Simultaneous monitoring of penile photoelectric plethysmography, penile tumescences, penile rigidity, bulbocavernosus-ischiocavernosus EMG and EKG was attempted to investigate the age-related erectile response to short period erotic film in 50 normal males and to elucidate the range of its characteristics for the diagnosis of impotence. The results obtained were summarized as follows ; l. Variability was observed in temporal relationship between penile pulse amplitude and penile erection. Of the 45 subjects who showed erection and/or increase in penile pulse amplitude 4 categories of response could be defined : Type I was observed in 13 subjects (28.9%)-erection and increased penile pulse amplitude occurring in parallel ; Type II, in 26 subjects(57.8%)_erection with increased penile pulse amplitude during the development or decline of erection but not during maximum erection ; Type III, in 4 subjects(8. 8%)_erection with no change in penile pulse amplitude ; and Type IV, in 2 subjects (4.4 %)_increased penile pulse amplitude without any erection. These results suggest that penile erection does not exclusively depend increased penile arterial blood flow but upon the cooperative mechanisms with the action of venous blockade which corresponds flexibly to the degree of arterial blood flow. 2. Following erotic stimulation, there was tendency to delay in latency to erection with aging. However, no difference in penile tumescence and rigidity among age groups was observed. This indicates that if the subject is affected by libido owing to strong erotic stimulation, maximum erection ensues regardless of aging. 3. The fact that subjects with good erection shows enough libido and that maximum erection ensues if erection develop under strong erotic stimulation suggests visual sexual stimulation method would be useful in differentiatial diagnosis of erectile dysfunction.
Adult* ; Aging ; Diagnosis ; Electrocardiography ; Erectile Dysfunction ; Humans ; Libido ; Male ; Penile Erection ; Plethysmography