L-Dex U400® is the first clinical aid for measuring the extracellular fluid differences of the arms and legs in women and the legs in men. These L-Dex measurements can aid in the clinical assessment of unilateral lymphedema of the arm and leg in women and the leg in men.
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"It is estimated that between 3 and 5 million patients in the United States suffer from lymphedema, with a significant proportion developing the disease as a consequence of cancer or its treatment.1 In oncology, the most common etiology for the development of lymphedema is the impaired or disrupted flow of lymph fluid through the draining lymphatic vessels and lymph nodes, usually as a consequence of surgery and/or radiation therapy. If the uninjured lymphatic vessels are unable to accommodate the increased lymphatic load, an accumulation of lymph fluid develops in the dependent tissues. Without intervention, lymphedema can lead to progressive swelling, fibrosis of the soft tissues, neurologic changes (eg, pain and/or paresthesias), and infection. Early identification of the signs and symptoms of lymphedema should be integral to the management of all patients who have received surgery and/or radiation, and are thus at high risk. When treated in the earliest stages, complications of this condition may be minimized." Lawenda, Cancer 200925
Characterized by excess protein and edema in the tissues, lymphedema can be the result of radiation therapy or surgery and may occur in one or both arms or legs. "Studies show from 20% to 45% of patients who are at risk for lymphedema will eventually develop it." Wall Street Journal 20042.
Lymphedema may be extremely debilitating and although it cannot be cured, treatments often involving exercise, compression bandaging and massage can arrest the condition. Early detection and therefore early treatment are critical to providing the best patient outcome.
Until recently, techniques involving measuring limbs with a tape measure or immersing limbs in water have been favored for the diagnosis of lymphedema. These techniques, in addition to being cumbersome and time consuming, are diagnostically unreliable.3"Currently, to our knowledge there is no accepted standard for the definition of lymphedema with regard to girth and volume. The different criteria that have been used to define lymphedema to date are not equivalent, and include 2.0-cm circumferential difference, a 200-mL limb volume change, and a 10% change in limb volume. As previously mentioned, a 10% change in limb volume is considered by many lymphologists as a more useful definition of lymphedema because it takes into account the body habitus of the patient. These are some of the most reported criteria, although many more exist. This lack of a standard definition is largely responsible for the wide variation in the reported incidence of lymphedema." Lawenda, Cancer 200925
Bioimpedance, which measures the extracellular fluid (ECF) differences of the arms, is the first FDA cleared technology as an aid in the clinical assessment of unilateral lymphedema of the arm in women. A matched normal analysis gives a standardized cutoff to aid in the clinical assessment of patients for potentially clinically significant differences in extracellular fluid volumes. Figure 1 shows a lack of overlap between the affected and unaffected patient groups in the study obtained when using BIS. In contrast, the volumetric approach, which has a low inter-operator reliability, shows an overlap between the patient groups.
ImpediMed's L-Dex device aids in the clinical assessment of unilateral lymphedema of the arm in women and offers a standardized and objective procedure.
In Spite of Advances, Lymphedema Remains a Significant Problem Even With the Adoption of More Conservative Breast TreatmentEarly detection has always been a key goal in successfully treating cancer. Improved surgical techniques and targeted therapies have also extended 5 year survival rates. Yet even with such new techniques as sentinel lymph node biopsy, incidence rates of lymphedema in 4-17% are cited in the literature for breast cancer patients5,6,7,8,9,10,11.
"Today, most lymphedema is not diagnosed until it is visually apparent. By this point, fibrotic changes and lipid deposition caused by protein rich extracellular fluid stasis have already begun. Following the medical model, emerging new solutions now demonstrate that early assessment, diagnosis and intervention prevents progression and helps protect your patient’s quality of life. The early detection and treatment of lymphedema is of the utmost importance. Baseline measurements of girth and volume will assist in finding any significant changes in the size of the limb, allowing the intervention to occur as early as possible." Lawenda, Cancer 2009.
The National Institutes of Health Data - "Preoperative Assessment Enables the Early Diagnosis and Successful Treatment of Lymphedema" Cancer 200812
Note: this study used a standardized volumetric measurement and not a bioimpedance device for assessment.
Data from a five year, prospective NIH study demonstrate that it is possible to prevent the progression of lymphedema in patients at risk.13 This research supports the findings of lymphedema researchers around the globe.14,15,16 In addition, there is a growing international consensus among professional organizations in support of the prospective (pre-surgical) assessment of newly diagnosed cancer patients to identify and manage those patients at high risk for lymphedema.
In this study, pre-surgical baselines established what was “normal’ for the patients in terms of fluid levels in their arms. Periodic post-operative clinical assessment using a standardized volumetric device could detect significant changes from pre-surgical levels. An off-the-shelf compression garment has been demonstrated to be an effective intervention. In the NIH study, all women diagnosed with subclinical lymphedema returned to their pre-surgical baseline arm volume after an average of 4.4 weeks.12,13 None (0%) progressed to a Stage 2 or Stage 3 lymphedema.
Physicians may now potentially add to their choice of clinical aids a new device that measures specifically the extracellular fluid differences between the arms. Within the pathophysiology of lymphedema, this is recognized as the first compartment to change, thereby aiding medical providers in an earlier clincial assessment. Lawenda, Cancer 200925
"The early detection and treatment of lymphedema is of the utmost importance. Baseline measurements of girth and volume will assist in finding any significant changes in the size of the limb, allowing the intervention to occur as early as possible." Lawenda, Cancer 200925
ImpediMed's L-Dex® technology utilizes the characteristics of frequency dependent current flow to quantify changes in extracellular fluid in the patient's arm. These changes can aid medical providers in clinically assessing patients for lymphedema of the arm in women and the leg in women and men. L-Dex technology is specific for extracellular fluid. As fluid accumulates, L-Dex values increase. The device provides an immediate result and is provided with software for tracking changes in patient's L-Dex values over time.
The L-Dex U400: A bioelectrical impedance analyzer/monitor utilizing impedance ratios that supports the measurement of extracellular fluid volume differences between the limbs to aid in the clinical assessment of unilateral lymphedema of the arm in women and the leg in women and men.
Lymphedema Analysis PC Software - an optional PC software package that is intended to be used only with the ImpediMed L-Dex U400 analyzer/monitor for uploading data on to the PC from the L-Dex U400, processing and analyzing of bioimpedance measurements.
"It is our responsibility as oncologists and patient educators to become familiar with the early signs and symptoms of lymphedema, the basic pathophysiology, prevention/risk reduction behaviors, and general management techniques...
Importantly, with the early identification and management of lymphedema, we can help many of our patients maintain their quality of life by minimizing cosmetic, functional, psychoemotional, and potentially life-threatening complications.” Lawenda, Cancer 200925
Bioimpedance Analysis (BIA) was first used over 30 years ago to measure the total water content of the body. More recently, however, BIA has been applied to the quantification of unilateral lymphedema 22,23,24. BIA involves passing an extremely small electrical current through the body and measuring the opposition to the flow of this current (defined as impedance). At low frequencies, current passes through the extracellular fluid (ECF) space and does not penetrate the cell membrane. At high frequencies, however, the current passes through both the intracellular fluid (ICF) and ECF (Figure 1: Biological Current Flow).
Based on this concept, together with the fact that the impedance of a geometrical system is related to conductor length, cross sectional area and signal frequency, a value of impedance can be calculated from a current passed through the body. The measured impedance is inversely proportional to the amount of fluid. By appropriate choice of signal frequency, this can be made specific for ECF or for total fluid determination.
The L-Dex U400 is a multi frequency bioelectrical impedance analyzer. The device accurately measures current, voltage and phase angle, and calculates impedance, resistance and reactance. These measurements and calculations are used to estimate extra cellular fluid (ECF) allowing for the assessment of the development of unilateral lymphedema of the arm in women and the leg in women and men.
The ImpediMed L-Dex U400 Extra Cellular Fluid Analyzer, like the SFB7, is a battery powered, accurate, multi-frequency, bioelectrical impedance analysis instrument operating in tetra-polar mode. The device accurately measures current, voltage and phase angle, and calculates impedance, resistance and reactance.
The ImpediMed L-Dex U400 is specifically designed for segmental bioelectrical impedance analysis to measure the ECF of the limbs in which a small alternating current of 200uA RMS at a frequency of approximately 3kHz to 1000kHz is passed between two current electrodes spanning the body. The voltage drop measured between a second pair of voltage-sensing electrodes is used to calculate the impedance value.
Bioelectrical impedance analysis measures the impedance or opposition to the flow of an electric current through the body fluids contained mainly in the lean and fat tissue. Impedance is low in lean tissue, where intracellular fluid and electrolytes are primarily contained, but high in fat tissue. Impedance is thus related to total fluid volume. The tissue and organs of the body are composed of cells surrounded by a cell membrane. This membrane separates fluid inside cells called intracellularfluid (ICF) from that surrounding the cells termed as extracellular fluid (ECF) that act as conductors to the flow of current through the body.
However, the cell membrane and tissue interfaces because they are 'imperfect capacitors' act as a barrier to penetration of current at low frequencies. Thus the total impedance and phase angle of alternating current flow will be frequency dependent.
The ImpediMed L-Dex U400 is specifically designed for segmental bioelectrical impedance analysis to measure the ECF of the limbs in which a small alternating constant current of 200uA RMS at a frequency of 3 kHz to 1000 kHz is passed between two current electrodes spanning the body. The voltage drop measured between a second pair of voltage-sensing electrodes is used to calculate the impedance value. The performance of the device may be checked with the aid of a calibration circuit (supplies as an accessory) for quality assurance or servicing purposes.
Bioelectrical impedance basics, simple mathematics, bioelectrical and anthropometric parameters from peer reviewed published journal articles are used to convert measured impedance to a corresponding estimate of extra cellular fluid ratio (extra cellular fluid index or lymphedema index - referred to as L-Dex), and differences between the arms. These estimates can be used as alternatives to the current circumferential measurements and water immersion methods, to indicate trends toward the potential development of Lymphedema.
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* Note: L-Dex®values that lie outside the normal range may indicate the early signs of lymphedema and values that have changed +10 L-Dex units from baseline may also indicate early lymphedema. The L-Dex scale is a tool to assist in the clinical assessment of lymphedema by a medical provider.