Strain gauge plethysmography for the detection of deep venous thrombosis.
ABSTRACT Deep venous thrombosis is a widely recognized medical problem which results in significant morbidity and mortality. Venography is the current 'gold standard' diagnostic test for deep venous thrombosis; however it is costly, invasive and is unnecessarily performed in 50% of cases. This paper describes a self-contained, non-invasive system for automatic venous occlusion plethysmographic measurement and analysis. An examination of 274 symptomatic limbs was conducted using strain gauge plethysmography and a subsequent venographic examination was then performed. The plethysmographic results were then compared with venography so as to develop a means of discrimination for thrombotic and non-thrombotic limbs. Strain gauge plethysmography using the Belfast DVT Screener yielded a sensitivity of 100% and a sensitivity of 66.3% for proximal segment DVT. The efficacy of the discriminatory algorithm was then tested for the diagnosis of DVT in a further 101 symptomatic patients. A sensitivity of 94.7% and a specificity of 81.7% were observed for strain gauge plethysmography for proximal segment thrombosis in this patient group. The Belfast DVT Screener is highly sensitive for deep venous thrombosis and may be used to reduce the need for venography, which is of benefit to both the patient and clinician.
- SourceAvailable from: Mohamed Elgendi[Show abstract] [Hide abstract]
ABSTRACT: Photoplethysmography (PPG) is used to estimate the skin blood flow using infrared light. Researchers from different domains of science have become increasingly interested in PPG because of its advantages as non-invasive, inexpensive, and convenient diagnostic tool. Traditionally, it measures the oxygen saturation, blood pressure, cardiac output, and for assessing autonomic functions. Moreover, PPG is a promising technique for early screening of various atherosclerotic pathologies and could be helpful for regular GP-assessment but a full understanding of the diagnostic value of the different features is still lacking. Recent studies emphasise the potential information embedded in the PPG waveform signal and it deserves further attention for its possible applications beyond pulse oximetry and heart-rate calculation. Therefore, this overview discusses different types of artifact added to PPG signal, characteristic features of PPG waveform, and existing indexes to evaluate for diagnoses.Current Cardiology Reviews 02/2012; 8(1):14-25.
- [Show abstract] [Hide abstract]
ABSTRACT: Strain gauge plethysmography (SGP) is a non-invasive method used in the detection of deep venous thrombosis (DVT). The technique is based on the measurement of calf volume changes in response to venous occlusion by a thigh cuff, the volume changes reflecting the rates of arterial inflow and venous outflow. A numerical model of the blood circulation within the limb and the response of this to a SGP test has been derived, based on treating the different parts of the circulatory system in the leg as resistance and capacitance elements. The simulation results were compared with clinical studies and support the ability of SGP to detect non-occlusive clots of more than 50-60% of the lumen, as well detecting calf vein occlusion. The non-linear behaviour of the venous compliance with intra-luminal pressure appears to be a particularly important factor within the model. In addition, increases in venous tone due to post-operative venospasm were shown to be a potential source of false positive results.Medical & Biological Engineering & Computing 06/2000; 38(3):348-55. · 1.79 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: The mechanisms by which graduated compression stockings prevent deep venous thrombosis are not completely understood. In the current study the physiologic effect of low-pressure graduated compression stockings on the venous blood flow in the lower limb and the practical aspects of their use were assessed. Patients having elective orthopaedic surgery at a university orthopaedic department were randomized into five groups to wear two different types of graduated compression stockings in thigh and knee lengths. Patients in the fifth control group did not wear graduated compression stockings. Venous occlusion strain gauge plethysmography was used to measure venous flow. After 20-minutes bed rest there was a highly significant increase in venous capacitance and venous outflow in patients in all of the four groups wearing stockings. There was no difference in the mean of the percentage change of venous capacitance in patients in the four groups wearing stockings. The knee length Brevet stockings were less efficient in increasing the venous outflow. There was no significant change in the venous capacitance and venous outflow in patients in the control group. Visual assessment of the fit and use of stockings was done, and patients' subjective opinion of comfort was sought. The knee length graduated compression stockings wrinkled significantly less, and significantly fewer patients reported discomfort with them. All stockings were reported to be difficult to use. Thigh and knee length stockings have a significant effect on decreasing venous stasis of the lower limb. Knee length graduated compression stockings are similarly efficient in decreasing venous stasis, but they are more comfortable to wear, and they wrinkle less.Clinical Orthopaedics and Related Research 03/2001; · 2.79 Impact Factor