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At least 19 recordsLinked to original sources
PubMed1986

Assessment of peripheral hemodynamics using impedance plethysmography.

Impedance plethysmography (IPG) is a safe, noninvasive method for measuring peripheral hemodynamics. The purpose of this article is to describe the IPG technique and its potential use by physical therapists in making hemodynamic evaluations. Impedance plethysmography requires the attachment of four circumferential Mylar band electrodes around a limb. We use a cardiograph to introduce a 4-mA current (I) at a frequency of 100 kHz in the two outer electrodes. The voltage (V) is sensed in the two center electrodes, and the resulting impedance (Z) is calculated using Ohm's law (Z = V/I). Arterial blood flow can be calculated using an impedance-related volume conduction equation. Impedance plethysmography has been shown to be economical, and any limb or limb segment can be evaluated. Applications are presented for the assessment of arterial blood flow, peripheral arterial disease, deep vein thrombosis, and venous insufficiency. Impedance plethysmography offers the physical therapist a safe and relatively simple technique to assess the peripheral vascular status of the patient.

Chronic Disease↗
PubMed1990

Diagnosis of aortic occlusive diseases using impedance plethysmography.

Impedance plethysmographic observations have been correlated with aortographic observations in 57 patients suspected of aortic occlusive diseases. Aortic occlusions have been characterised by marked decrease in blood flow index and significant increase in differential pulse arrival time at thigh level bilaterally. Atherosclerotic affection of the aorta has been featured by a bilateral decrease in the value of blood flow index as well as differential pulse arrival time at thigh level. Leriche's syndrome, however, has been found to decrease the blood flow index moderately at thigh in both the legs without any significant change in differential pulse arrival time. Aortography in all the patients has confirmed the diagnosis made by impedance plethysmography.

Aorta, Abdominal↗
PubMed1990

Diagnosis of venous disorders using impedance plethysmography.

Impedance plethysmography (IPG) was carried out in one hundred and forty-one patients suspected of venous disorders using Parulkar's method. In these patients occlusive impedance phlebography (OIP) and venography were also carried out using standard procedures. Comparison of IPG and OIP observations with venographic findings revealed sensitivity of these methods to be 65% and 77.7% in the diagnosis of primary varicosity of veins and chronic deep vein thrombosis respectively with a specificity of 85%. Occlusive impedance phlebograms showing unilateral decrease in OIP parameters were observed to be sufficiently diagnostic. IPG observations in 5 patients with arterio-venous malformation were observed to be different from those in patients with deep vein thrombosis.

Adolescent↗
PubMed1990

Diagnosis of peripheral arterial occlusive diseases using impedance plethysmography.

Impedance plethysmographic observations have been compared with arteriographic findings in 216 patients with peripheral arterial occlusive diseases. Impedance plethysmographic diagnosis in these patients was obtained by Parulkar's method without apriori knowledge of arteriographic diagnosis. But for minor discrepancy in the anatomical location of the block in few patients, impedance plethysmographic observations correlated very well with arteriographic findings. Impedance plethysmographic diagnosis was found to be correct in 312, wrong in 53, false negative in 8 limbs respectively, yielding a sensitivity of 97.5% and specificity of 98.1% of this technique.

Adolescent↗
PubMed1982

Comparison of electrical field plethysmography with electrical impedance plethysmography.

As a means for assessing cardiac function, electrical field plethysmography (EFP) has been shown to have some features quite different from electrical impedance plethysmography (EIP). Here the two techniques are compared by using the two systems simultaneously on a subject and also with independent use in different electrode configurations. The results conform with the view that EIP is related primarily to volumetric changes of the aorta, whereas EFP is affected predominantly by changes in cardiac dimensions and orientation. Because of this difference, the standard time differential formula used for EIP is not applicable for the computation of cardiac output from the EFP waveforms. An alternative method of computation based on the amplitude of the EFP waveform is suggested.

Cardiac Output↗
PubMed1988

Measurement of tidal volume during high frequency ventilation by impedance plethysmography.

Electrical impedance plethysmography was evaluated in lambs as a method of measuring tidal volume (VT). Over tidal volumes ranging from 15 to 414% of estimated dead space, and frequencies of 300 to 1000 breaths/min, correlation between VT measured by the impedance technique and VT measured by whole-body plethysmography was 0.98. Above 600 breaths/min, the correlation between the two methods was 0.94. Independent calibration of the impedance technique using a pneumotachograph at conventional rates of ventilation yielded absolute values of VT which closely corresponded to values obtained with the whole-body plethysmograph (slope = 1.05, intercept = 1.4 ml, r = 0.99). These results support the potential utility of impedance plethysmography in clinical applications of high frequency ventilation.

Animals↗
PubMed1987

The clinical implications of bilaterally abnormal impedance plethysmography.

Although impedance plethysmography (IPG) is a test of recognized value in the diagnosis of acute proximal deep venous thrombosis (DVT), its meaning in patients with bilaterally abnormal IPGs is unclear. Consequently, we sought to determine the clinical significance of the bilaterally abnormal IPG in hospitalized patients. In a five-month prospective study, 19% (81/425) of all IPGs done at our institution were bilaterally abnormal (55% of all abnormal IPGs). Acute proximal DVT was found in 26% (14/53) of patients with bilaterally abnormal IPGs who underwent further diagnostic testing. Thirty-five percent of the patients with DVT were found to have either bilateral lower extremity DVT or clots in the inferior vena cava. A numerical score, the venous function index (VFI), was computed for the 101 legs for which further definitive diagnostic evaluations for DVT had been completed. The mean VFI of seven for legs with acute proximal DVT was significantly less than the mean VFI of 13 for legs with no DVT. Fifty percent of legs with a VFI less than or equal to five had DVT, whereas only 7% of legs with a VFI greater than 15 had DVT. The bilaterally abnormal IPG is a common clinical occurrence, is frequently associated with acute DVT, and the VFI is helpful in discriminating legs with acute proximal DVT from normal legs in patients with a bilaterally abnormal IPG.

Adolescent↗
PubMed1985

A comparison of impedance plethysmography and strain gauge plethysmography in the diagnosis of deep venous thrombosis in symptomatic outpatients.

Strain gauge plethysmography and impedance plethysmography are non-invasive diagnostic techniques for deep venous thrombosis. In 145 consecutive out-patients presented with suspected acute deep venous thrombosis we compared these two techniques. Venography was performed if one or both tests were positive. Both tests were repeatedly normal in 91 (63%) patients, while in 38 (26%) patients both tests were abnormal and venography confirmed the presence of venous thrombosis. In six other patients the impedance plethysmography test result and venography were positive while the result of the strain gauge plethysmography test was normal. This difference was statistically significant (p less than 0.001). Four of these six patients had acute proximal thrombosis of the deep leg veins. The impedance plethysmography was falsely positive in four patients while strain gauge plethysmography was falsely abnormal in one patient. We conclude that in the diagnostic management of patients with suspected deep venous thrombosis, impedance plethysmography is superior to strain gauge plethysmography.

Diagnostic Errors↗
PubMed1990

Impedance plethysmography: basic principles.

Impedance Plethysmography technique has been discussed with explanation of two compartment model and parallel conductor theory for the estimation of peripheral blood flow and stroke volume. Various methods for signal enhancement to facilitate computation of blood flow are briefly described. Source of error in the estimation of peripheral blood flow is identified and the correction has been suggested.

Humans↗
PubMed1986

[Development of cerebral blood flow measurement using skull impedance plethysmography].

Using skull impedance plethysmography, a developmental approach was made to the measurement of mean cerebral blood flow (mCBF) from brain volume exchanging ratio (delta V) involved in bilateral jugular venous occlusion. An experimental study thereof revealed the following results: Comparative examinations were made between total cerebral blood flow obtained by the superior sagittal sinus hydrogen clearance method and delta V X t obtained by the present approach led to the establishment of a linear correlation there between and also of the following calculating formula: mCBF = k X delta V X t (omega X sec) k: proportional coefficient t: blood flow increasing time (10 sec.) The experimental results revealed that the present approach was valid enough as an index of cerebral blood flow. Some future improvements therein seem to make also its clinical application possible. The theory and method of the present approach are described with an examination of several points raised thereby.

Animals↗
PubMed1975

Evaluation of a microcrystalline bovine collagen hemostatic agent in canine solid viscera injury using abdominal impedance plethysmography.

Bioelectric impedance as a sensitive noninvasive technique for detecting and monitoring changes in compartmental body fluid volume was used to compare the efficacy of two hemostatic agents in controlling postoperative abdominal bleeding following surgically induced solid viscera injury. Gelatin foam-oxidized cellulose sponge and bovine MCHH were both effective topical hemostatic agents. It appears that MCCH has certain advantages over conventional agents.

Abdominal Injuries↗
PubMed1977

Impedance plethysmography: correlation with contrast venography.

Impedance plethysmography is a noninvasive, indirect test for deep venous occlusion in the lower limbs. The results of ascending contrast venography impedance plethysmography have been compared in 315 limbs. Impedance plethysmography was positive in 77 of 79 limbs with acute deep vein thrombosis proximal to the calf. It was positive in 6 of 27 limbs with clot isolated in the calf. Only 7 false-positive plethysmograms were found in 161 normal contrast venograms. The clinical implications of these data are discussed.

False Positive Reactions↗
PubMedDate not supplied

Noninvasive detection of axillary and subclavian venous thrombosis by impedance plethysmography.

Venous occlusion impedance plethysmography (IPG) is an objective noninvasive test which is widely employed for the detection of deep venous thrombosis (DVT) in the lower extremities. The IPG technique is easily adapted to the evaluation of upper extremity venous thrombosis, as demonstrated in 46 patients with symptoms of axillary and subclavian venous thrombosis (88 limbs) and 26 normal volunteers (52 limbs). Venograms were obtained in 18 patients (22 limbs) and correlated in all cases with the previous IPG interpretation. The test procedure and interpretation criteria for the noninvasive detection of upper extremity deep venous thrombosis are similar to those previously developed for the lower extremities, but with more emphasis on comparison with the contralateral limb. Vascular laboratories performing IPG for lower extremity DVT should be able to employ this test for the detection of upper extremity venous thrombosis as well.

Adolescent↗
PubMed1985

Diagnostic efficacy of impedance plethysmography for clinically suspected deep-vein thrombosis. A randomized trial.

Impedance plethysmography is an accurate noninvasive method to test for proximal vein thrombosis, but it is insensitive to calf-vein thrombi. We randomly assigned patients on referral with clinically suspected deep-vein thrombosis and normal impedance plethysmographic findings to either serial impedance plethysmography alone or combined impedance plethysmography and leg scanning (which has been shown to be essentially as sensitive as venography) and compared the long-term outcomes. During the initial surveillance, deep-vein thrombosis was detected in 6 of 311 patients (1.9%) tested by serial impedance plethysmography alone and in 30 of 323 patients (9.3%) (most with calf-vein thrombi) tested by the combined approach (p less than 0.001). During long-term follow-up, no patient died from pulmonary embolism; but 6 patients (1.9%; 95% confidence limits, 0.7% to 4.2%) tested by serial impedance plethysmography developed deep-vein thrombosis compared with 7 patients (2.2%; 95% confidence limits, 0.9% to 4.4%) tested by the combined approach. Serial impedance plethysmography used alone is an effective strategy to evaluate such symptomatic patients.

Adult↗
PubMed1990

Impedance plethysmography.

The technique of impedance plethysmography is described and its application to observation of lung volume changes in the horse at exercise is discussed. The results from horse at rest show that there is a close relationship between rate of lung volume change (flow rate) and the associated impedance changes during both inspiration and expiration. Impedance changes during exercise were related to inspiration and expiration by observation of associated respiratory sounds. Artefacts related to technical difficulties are also indicated.

Animals↗