Frequently Asked Questions
Can I reuse electrodes?
Electrodes are single use items. During use the electrode gel picks up skin debris and hair which reduces the efficacy of the electrode. This will affect the measurements obtained. Reuse of electrodes is also unhygienic.
Can the L-Dex® device be used to measure legs?
The L-Dex® U400 device is cleared as an aid in the clinical assessment of unilateral lymphedema of the arm and leg in women and the leg in men.
Do metal implants such as knee, shoulder and hip replacements alter
the measurements?
Metal implants may alter the measurements made by the L-Dex® device . The magnitude of this affect will be dependent on the manufacture and type of implant but in most cases the effect should be a constant offset. This offset may affect the initial reading relative to the normal L-Dex; range but should not affect the ability to track the change in the L-Dex value over time. Therefore, the progress of the condition or the effectiveness of therapy.
In cases where a knee or hip replacement is present in only one leg then we recommend placing the “black” electrode on the foot of the leg without the implant.
Does the L-Dex® device distinguish between lymphedema and other types of edema?
The L-Dex® device device is not a definitive diagnostic tool and cannot distinguish between lymphedema (swelling in the extracellular compartment) and that caused by other means such as trauma (which may include both intra and extracellular swelling). The healthcare professional should take into account the patient history when interpreting the L-Dex values.
What if both arms are at-risk of developing lymphedema?
When cancer related surgery to both breasts has occurred a patient may be at-risk of developing lymphedema in both arms known as bilateral lymphedema of the arms. The L-Dex® device relies on the use of the unaffected (not at-risk) arm as a control measurement and therefore should not be used on this patient group.
Can the L-Dex® device be used to assess late stage lymphedema of the arm?
Yes. The L-Dex® device is ideally used to assess the early and very early stages of lymphedema when the condition can be best managed. However, the L-Dex device and lymphedema index (L-Dex) can be used to assess late stage lymphedema.
How do I best use L-Dex® baselines?
The L-Dex® device software and printable report track the change in the L-Dex value over time. A healthcare professional can set any measurement as a baseline from which to document the change in the L-Dex value. Baselines may be used in the following ways.
- To document the progression of the disorder from a presurgical baseline. Health care professionals may use this method to asses the early stages of lymphedema using the presurgical “normal” measurement for a patient as a baseline.
- To document the progression of the disorder from a post surgical baseline. Healthcare professionals may use this to assess the early stages of lymphedema but should be conscious of making sure that the post surgical “normal” baseline measurement is not performed when post surgical swelling is present.
- To document the efficacy of treatment in a patient who already has developed lymphedema.
What does an L-Dex® value of 10, 20 or 30 mean?
The lymphedema index (L-Dex®) defines the normal range for a patient without lymphedema. L-Dex values greater than 10 are outside the normal range and are indicative of lymphedema. An L-Dex value of 20 puts a patient approximately two times outside the normal range and likewise, 30 is approximately 3 times outside the normal range.
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. The L-Dex scale is not intended to diagnose or predict lymphedema of an extremity.
How do the L-Dex® compare to volume measurements (tape measure)?
L-Dex® measurements are a more sensitive and direct measure of swelling in the extracellular compartment. Volume measurements can be affected by weight gain (such as fat deposition) or muscle loss (often associated with inactivity after surgery). This causes inconsistencies when trying to discern the volume changes due to lymphedema from those that are not. For this reason, “exact” comparisons between L-Dex values and volume measurements cannot be made. Statements such as “an L-Dex value of 20 is equivalent to volume of 100ml” are not verifiable because there is no practical way to ensure that the volume change measured has not been confounded by weight gain or loss (muscle or fat) in the arm.
Can L-Dex® values be used to grade lymphedema?
L-Dex® values are a relatively new technology and no L-Dex value cutoffs have been set to grade lymphedema into stage 1, stage 2 and stage 3 categories. Grading systems for lymphedema rely on a cumulative symptom assessment conducted by the healthcare professional. At this time the healthcare professional may use L-Dex to form part of this assessment but not as a definitive grading tool in itself.
What is the maximum L-Dex® value?
There is no theoretical L-Dex® maximum. In practice, early stage lymphedema will be associated with low L-Dex values just outside the normal range value of +10. L-Dex values in the range of 100-250 have been reported by healthcare professionals using the L-Dex device device to assess patients with developed lymphedema.
Should I measure a patient before of after complex physical therapy (CPT)?
Ideally, a patient should be assessed when they are in a stable rested state. Complex physical therapy (CPT) puts the patient into a state of lux where distribution of fluids is in a dynamic moment. Consequently the L-Dex® value will increase and decrease in response to this dynamic state. Therefore, for stable tracking of the L-Dex value from treatment to treatment, it is recommended to measure the patient before each CPT session.
Does fibrotic tissue alter the L-Dex® measurement?
L-Dex® is best used to pro-actively aid in the clinical assessment of extracellular fluid prior to, or during, early stage (fluid-like) lymphedema. However, L-Dex values will still respond to decreases in the extracellular fluid in the arm of fibrotic limbs. This allows the effectiveness of treatment to be assessed in patients with developed lymphedema where some fibrosis may be present. In patients with advanced cases of fibrosis where there is little excess fluid the L-Dex results may not correspond to the physical size of the arm.
How important is correct electrode placement?
Correct electrode placement is extremely important. Incorrect placement will result in incorrect L-Dex® values. Please refer to the electrode placement guidelines on pages 15-17 of the L-Dex device instructions for use.
Are there any patients I shouldn’t measure with this device?
Patients who have an implanted cardiac device such as a pacemaker or an ICD should not be measured with the L-Dex® device. Similarly, patients who are pregnant should also not be measured with the L-Dex device.
How do I know which is the dominant limb?
The dominant arm is defined as the arm with which a patient does most manual work. Predominantly this is also the arm that a patient uses to write with. Usually limb dominance can be assessed by simply asking the patient if the are “right” or “left handed”. Limb dominance has a slight and known affect on impedance measurements and the L-Dex® scale accounts for this effect.