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?
At present the L-Dex® device is only for the assessment unilateral lymphedema of the arm. Devices for the assessment of unilateral leg lymphedema and bilateral leg lymphedema are under development.
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 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 the first device to measure the extracellular fluid differences in the arms as an aid to the clinical assessment of unilateral lymphedema in the arms. Due to the basic pathophysiology of lymphedema, the measurement of this clinical compartment offers an additional aid to the clinician in their early clinical assessment. In late stage lymphedema, extracellular fluid differences have less clinical relevance, but are still important to the clinical assessment of unilateral lymphdema.
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 aid in their clinical assessment of unilateral lymphedema.
- An increase of ten (10) L-Dex units from a patient's baseline L-Dex value represents a change of three (3) standard deviations (3SD). This has been demonstrated in a matched normal population to be potentially clinically relevant to the medical provider in aiding in the clinical assessment of unilateral lymphedema of the arm.
- For an initial assessment where no measurement history exists, a range representing 3SD either side of a normal population mean is highlighted on the L-Dex scale to aid the medical provider in their clinical assessment. Medical providers need to be aware that a 3SD change can still occur within this range and where possible should utilize changes from baseline of 10 L-Dex units.
How do the L-Dex® values 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 used only as an aid in the clinical assessment of unilateral lymphedema of the arm in female breast cancer patiens and no L-Dex values have been set to grade lymphedema. 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. 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 flux 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 aid in the clinical assessment of extracellular fluid differences between the arms. Based on the pathophysiology of lymphedema, the earlier stages are often represented by changes in this compartment. In later stages, where the condition has become chronic, and tissue changes have occured due to fibrosis, extracellular fluid levels can decrease. In chronic cases, L-Dex, as an aid in the clinical assessment, has less relevance and total arm measurements need to be considered by the medical provider.
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 in 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 arm?
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, arm dominance can be assessed by simply asking the patient if they are “right” or “left handed”. Arm dominance has a slight and known affect on impedance measurements and the L-Dex® scale accounts for this effect.