A bioelectrical impedance analyzer/monitor for use on adult human patients, utilizing impedance ratios that are displayed as an L-Dex ratio that supports the measurement of extra cellular fluid volume differences between the limbs and is presented to the clinician on an L-Dex scale as an aid to their clinical assessment of unilateral lymphedema of the arm and leg in women and the leg in men. The device is only indicated for patients who will have or who have had lymph nodes, from the axillary and pelvic regions, either removed, damaged or irradiated. The device is not intended to diagnose or predict lymphedema of the extremity. 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.
Device Story
Multi-frequency bioelectrical impedance analyzer; non-invasive; battery-powered. Measures current, voltage, and phase angle to calculate impedance, resistance, and reactance. Inputs: bioelectrical impedance signals from limbs via EKG-type electrodes. Outputs: L-Dex ratio representing extracellular fluid (ECF) volume differences between limbs. Used by clinicians to aid in assessment of unilateral lymphedema. Optional PC software facilitates data upload, processing, and analysis. Benefits: provides objective data to assist clinical evaluation of fluid status in patients with history of lymph node removal, damage, or irradiation.
Clinical Evidence
Clinical performance data provided in support of expanded indications. No specific metrics (e.g., sensitivity, specificity) provided in the summary document.
Technological Characteristics
Multi-frequency bioelectrical impedance analyzer. Uses EKG-type electrodes for patient interface. Complies with IEC 60601-1 (safety) and IEC 60601-1-2 (EMC/EMI). Battery-powered. Software-based processing of impedance measurements.
Indications for Use
Indicated for adult human patients who have had or will have lymph nodes from axillary or pelvic regions removed, damaged, or irradiated. Used as an aid in clinical assessment of unilateral lymphedema of the arm and leg in women and the leg in men. Contraindicated for patients with active implanted medical devices, pregnant patients (unless under specialist guidance), patients undergoing external defibrillation, or patients with allergies/skin sensitivities to electrode hydrogel or skin breakdown at electrode sites.
Regulatory Classification
Identification
An impedance plethysmograph is a device used to estimate peripheral blood flow by measuring electrical impedance changes in a region of the body such as the arms and legs.
Special Controls
*Classification.* Class II (special controls). The device, when it is a body composition analyzer which is not intended to diagnose or treat any medical condition, is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to the limitations in § 870.9.
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K100811
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NOV - 4 2011
# L-Dex® U400 ExtraCellular Fluid Analyzer
## 510(k) Traditional Premarket Notification Summary
| Device Trade or Proprietary Name: | L-Dex® U400 ExtraCellular Fluid Analyzer |
|-----------------------------------|------------------------------------------|
| Common / Classification Name: | Impedance Plethysmograph |
| Class: | II |
| Regulation Number: | 870.2770 |
| Panel: | Cardiovascular |
| Product Code: | DSB |
### Labeling:
Federal (United States) Law restricts this device to sale by or on the order of a physician or licensed healthcare professional.
#### Predicate Device for Substantial Equivalence Comparison:
The L-Dex® U400 ExtraCellular Fluid Analyzer, also referred to as the L-Dex U400 in the rest of this document, is claimed to be substantially equivalent to the following currently marketed Predicate Device and currently being marketed by ImpediMed Limited:
| Manufacturer | Device Name | 510-K<br>Number | Decision Date |
|----------------------|---------------------------------------------|-----------------|---------------|
| ImpediMed<br>Limited | L-Dex® U400 ExtraCellular Fluid<br>Analyzer | K080825 | Oct. 03, 2008 |
#### Device Description:
This premarket submission is to expand the previously cleared Indications for Use/Intended Use in the predicate device to include legs in women and men in addition to the predicate device clearance for arms in women, and clarify that it is for use on adult human patients.
The L-Dex® U400 ExtraCellular Fluid Analyzer like its predicate is a multi-frequency bioelectrical impedance analyzer. It is a non-invasive, battery powered extracellular fluid status analyzer.
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The L-Dex® U400 accurately measures current, voltage and phase angle, calculates impedance, resistance and reactance as with its predicate. These measurements and calculations are used to estimate extracellular fluid (ECF) allowing for aiding in the assessment of the development of unilateral Lymphedema of the limbs.
#### Indications for Use/Intended Use:
A bioelectrical impedance analyzer/monitor for use on adult human patients, utilizing impedance ratios that are displayed as an L-Dex ratio that supports the measurement of extra cellular fluid volume differences between the limbs and is presented to the clinician on an L-Dex scale as an aid to their clinical assessment of unilateral lymphedema of the arm and leg in women and the leg in men.
The device is only indicated for patients who will have or who have had lymph nodes, from the axillary and pelvic regions, either removed, damaged or irradiated. The device is not intended to diagnose or predict lymphedema of the extremity.
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.
### Contraindications for Use:
Patients with active implanted medical devices, pregnant patients (unless under the guidance of a medical specialist), and patients undergoing external defibrillation.
Patients with allergies to electrode hydrogel, skin sensitivities to electrode hydrogel and skin breakdown in areas where the L-Dex electrode placement is required.
This device is contraindicated for use on compromised skin surfaces primarily due to the adherence of the EKG type electrodes used.
### Clinical Performance Data:
Clinical Performance data in support of the expanded indications for use is included within this submission.
#### Rationale for Substantial Equivalence:
- 1. The L-Dex® U400 employs the same patient interface design as the predicate device.
- 2. The hardware and software of the L-Dex® U400 is identical in design, construction and manufacturer as the predicate device.
- 3. The operational features of the L-Dex® U400 are the same as those of the predicate device.
- 4. The safety features of the L-Dex® U400 are the same as those of the predicate device.
Therefore, in summary, the L-Dex® U400 ExtraCellular Fluid Status Analyzer is substantially equivalent to the predicate device.
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#### Safety and Effectiveness
The L-Dex® U400 ExtraCellular Fluid Analyzer complies with the electrical standards for Safety and Electro Magnetic Compatibility / Immunity (EMC / EMI) in accordance with the International Standards IEC 60101-1 and IEC 60601-1-2. This testing to the low voltage directive and to emissions / immunity requirements for EMC/EMI requirements reasonably assures the device is safe when used as directed for its prescribed intended use.
The L-Dex® U400 ExtraCellular Fluid Status Analyzer does not raise any new issues of safety, effectiveness or performance of the device when compared to the existing predicate device.
Conclusions:
The data submitted in this 510(k) Premarket Notification, for the L-Dex® U400
ExtraCellular Fluid Status Analyzer demonstrates that this product is substantially
equivalent with respect to the indications for use, operating principles, operational features
and safety features to the legally marketed predicate device. With the information
provided, the safety and effectiveness of the product can be reasonably assured, and we
believe that this device clearly meets the requirements for a "Substantial Equivalence"
decision in accordance with the 510(k) guidelines.
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Image /page/3/Picture/1 description: The image shows the logo for the U.S. Department of Health & Human Services. The logo consists of a stylized eagle with its wings spread, enclosed within a circle. The text "DEPARTMENT OF HEALTH & HUMAN SERVICES USA" is arranged around the upper portion of the circle.
Food and Drug Administration 10903 New Hampshire Avenue Document Mail Center - WO66-G609 Silver Spring, MD 20993-0002
NOV - 4 2011
ImpediMed Limited % Mr. Alden Kav Vice President Quality & Regulatory ImpediMed Limited 5959 Cornerstone Court West, Suite 100 SAN DIEGO CA 92121 ·
Re: K100811
Trade/Device Name: L-Dex® U400 ExtraCellular Fluid Analyzer Regulation Number: 21 CFR& 870.2770 Regulation Name: Impedance plethysmograph Regulatory Class: II Product Code: OBH Dated: May 16, 2011 Received: May 18, 2011
Dear Mr. Kay:
We have reviewed your Section 510(k) premarket notification of intent to market the device referenced above and have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to legally marketed predicate devices marketed in interstate commerce prior to May 28, 1976, the enactment date of the Medical Device Amendments, or to devices that have been reclassified in accordance with the provisions of the Federal Food, Drug, and Cosmetic Act (Act) that do not require approval of a premarket approval application (PMA). You may, therefore, market the device, subject to the general controls provisions of the Act. The general controls provisions of the Act include requirements for annual registration, listing of devices, good manufacturing practice, labeling, and prohibitions against misbranding and adulteration. Please note: CDRH does not evaluate information related to contract liability warranties. We remind you, however, that device labeling must be truthful and not misleading.
If your device is classified (see above) into either class II (Special Controls) or class III (PMA), it may be subject to additional controls. Existing major regulations affecting your device can be found in the Code of Federal Regulations, Title 21, Parts 800 to 898. In addition, FDA may publish further announcements concerning your device in the Federal Register.
Please be advised that FDA's issuance of a substantial equivalence determination does not mean that FDA has made a determination that your device complies with other requirements of the Act or any Federal statutes and regulations administered by other Federal agencies. You must comply with all the Act's requirements, including, but not limited to: registration and listing (21 CFR Part 807); labeling (21 CFR Part 801); medical device reporting of medical device-related
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#### Page 2
adverse events) (21 CFR 803); good manufacturing practice requirements as set forth in the quality systems (QS) regulation (21 CFR Part 820); and if applicable, the electronic product radiation control provisions (Sections 531-542 of the Act); 21 CFR 1000-1050.
If you desire specific advice for your device on our labeling regulation (21 CFR Part 801), please go to http://www.fda.gov/AboutFDA/CentersOffices/CDRH/CDRHOffices/ucm115809.htm for the Center for Devices and Radiological Health's (CDRH's) Office of Compliance. Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21CFR Part 807.97). For questions regarding the reporting of adverse events under the MDR regulation (21 CFR Part 803), please go to
http://www.fda.gov/MedicalDevices/Safety/ReportaProblem/default.htm for the CDRH's Office of Surveillance and Biometrics/Division of Postmarket Surveillance.
You may obtain other general information on your responsibilities under the Act from the Division of Small Manufacturers, International and Consumer Assistance at its toll-free number (800) 638-2041 or (301) 796-7100 or at its Internet address
http://www.fda.gov/MedicalDevices/Resourcesfor You/Industry/default.htm.
Sincerely yours,
Hubert Lemmer MD
Herbert P. Lerner, M.D., Director (Acting) Division of Reproductive, Gastro-Renal and Urological Devices Office of Device Evaluation Center for Devices and Radiological Health
#### Enclosure
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#### K100811 510(k) Number: L-Dex® U400 ExtraCellular Fluid Analyzer Device Name:
#### Indications for Use/Intended Use:
A bioclectrical impedance analyzer/monitor for use on adult human patients, utilizing impedance ratios that are displayed as an L-Dex ratio that supports the measurement of extra cellular fluid volume differences between the limbs and is presented to the clinician on an L-Dex scale as an aid to their clinical assessment of unilateral lymphedema of the arm and leg in women and the leg in men.
The device is only indicated for patients who will have or who have had lymph nodes, from the axillary and pelvic regions, either removed, damaged or irradiated.
The device is not intended to diagnose or predict lymphedema of the extremity.
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.
#### PLEASE DO NOT WRITE BELOW THIS LINE-CONTINUE ON ANOTHER PAGE IF NEEDED)
Concurrence of CDRH, Office of Device Evaluation (ODE)
Prescription Use _____ (Per 21 CFR 801.109)
Hulut
(Division Sign-Off)
Division of Reproductive, Gastro-Renal, and
Urological Devices
K100811
510(k) Number
Two short videos show you everything — or skip straight to the written tutorial if you'd rather read. You can reopen this any time from the Tutorial button in the top bar.
Part 1 — Search, results, and everyday workflows 16 min
Part 2 — Embeddings: the galaxy map 3 min
1. Search: exact and fuzzy
Type a phrase like "coronary artery calcification" into the search box. You get two kinds of results. Exact results match the literal phrase — prefix searches work ("coronary artery calcificati") but suffix searches do not. Fuzzy results match on the meaning and intent of your phrase rather than the exact words, and are sorted by relevance score. Hover over the Exact or Fuzzy badge on any row to see exactly why it matched.
Use the checkboxes above the results to narrow: SaMD keeps only software-only devices, AI / ML keeps only devices with AI.
Exact vs. fuzzy search: what's the difference?
Exact matches on the literal phrase (prefix search works, suffix does not). Fuzzy matches on the meaning and intent of the phrase rather than the exact words. Hover over the badge on any row to see why it matched.
You search "coronary artery calcification" and want only software devices with AI. What two filters do you apply?
Narrow by SaMD (software-only devices), then narrow by AI/ML (devices with AI).
2. The results table
Scroll right in the results table. The intended use is extracted for you — no need to open the PDF. The device story gives a high-level snapshot of what the device does and how it's used. The AI Performance sub-table shows each output name, acceptance criteria, observed values, and development/test dataset descriptions — the same format Innolitics uses for regulatory strategy outputs, and the fastest high-level fingerprint of an AI device. It is AI-generated but has been very reliable in practice.
Where do you find a device's intended use without opening the PDF?
Scroll right in the search results table. The intended use column is extracted for you; no need to dig into the 510(k) summary PDF.
What does the AI Performance sub-table show, and why is it useful?
Output name, acceptance criteria, observed values, development dataset description, and test dataset description. It's the same format we use for regulatory strategy output and Fast 510(k) input, and the fastest high-level fingerprint of an AI device. AI-generated but reliable in practice.
3. Judging fuzzy relevance
Fuzzy results trail off in relevance as you scroll. Use three signals to decide how far down to go: the fuzzy badge explanations, the intended use column, and whether your target output (e.g., Cobb angle) still appears in the AI Performance sub-table. Once it stops appearing, you're past the relevant zone. A top hit with a low score (~0.4) and a stretched explanation is a hint the closest predicates are far away — the project may be headed for De Novo. Note the fuzzy search is a pattern match: it doesn't handle negation ("not") well, and hardware devices can appear — filter by SaMD/AI ML to cut them.
How do you judge how far down fuzzy search results to go?
Use the relevancy signals: the fuzzy badge explanations, the intended use column, and whether the target output (e.g., Cobb angle) still appears in the AI Performance sub-table. Once it stops appearing, results are trailing off in relevancy.
4. Device detail page: chat and citations
Click a device name to open its detail page: device facts on the left, a chat window on the right. Ask something like "Describe the training data". The answer carries little citation bubbles — click one to jump to the highlighted passage in the source PDF, so you can verify every AI answer against the document. There's also a Download PDF button for sharing.
How do you verify an AI chat answer on the device detail page?
Click the citation bubbles to jump to the relevant highlight in the source document.
Reading rule for every project: how many summaries do you read in full?
At least the three most relevant 510(k) or De Novo summaries, in full. After that, use targeted chat questions to confirm your memory quickly. The tool supports this professional habit — it doesn't replace it.
5. Side-by-side comparison
Select multiple rows in the results table (aim for under ~10), then open the PDF Viewer tab. Ask one question — it goes to all selected devices in parallel, each with citations. This is the fastest way to compare and contrast devices: training data, PCCP scope, how they handled adding new scanners, and so on.
What does the side-by-side PDF viewer mode do?
Select multiple devices, open the PDF viewer tab, and ask one question (e.g., "Describe the training data"). It queries all selected devices simultaneously with citations, so you can compare and contrast quickly.
6. Collections
With rows selected, go to the Collections tab and create a labeled collection (e.g., "Cobb Angle Project"). Reload that selection any time — before a client call, pull up the collection and ask questions across all of its devices at once.
How do you save a set of selected devices for later use?
Select the rows, go to the Collections tab, and create a labeled collection (e.g., "Cobb Angle Project"). You can reload the selection anytime and carry it into the PDF viewer and other tabs that support selections.
7. Product codes and the regulations tree
Click a product code in the results to jump to it in the regulations tree — identification text, sibling product codes, and devices you can open in a PDF viewer on the right. Click a regulation number to see its identification, special controls, and related product codes. You can also search by product code or regulation number at the top of the tree. Always read the special controls if any exist for your device — it broadens your search and sharpens pre-kickoff research.
What can you do from the regulations tree view?
Browse product codes and regulation numbers, read the identification text and special controls, browse sibling product codes, open device PDFs on the right, and search by product code or regulation number at the top of the tree.
8. Chart view
Click Show Chart and segment by regulation number (or product code) to see which regulations dominate your result set. Clicking a regulation takes you into the regulations tree. Great for spotting that most matches are, say, hardware laparoscopic devices — a cue to go back and filter.
How do you see which regulations dominate a search result set?
Click "Show Chart" and segment by Regulation Number. Clicking a regulation takes you to the regulations tree.
9. The predicate graph
Open the Predicates tab for a family-tree view of predicate relationships. Click a node to trace its parents and children; selections from search carry over pre-selected. Commonly predicated devices are worth reading — a lot of people predicated them for a reason. The visual lineage is also handy on client calls, e.g. to show how a predicate family evolved and justify why your predicate still holds.
In the predicate graph, why are commonly predicated devices worth reading?
A lot of people predicated them for a reason. Clicking a node traces parents and children, and selections from search carry over pre-selected.
10. Embeddings: the galaxy map
The Embeddings tab plots every matching document in a 2-D "galaxy map" where semantically similar devices cluster together. Hover or click clusters to explore, and let AI label the clusters for you. Embeddings beat product codes for grouping: two devices can carry different product codes (LLZ vs. QIH) yet do the same thing — the embedding captures the meaning of the intended use and device story. This is also exactly how retrieval-augmented generation (RAG) works under the hood, and it makes a great visual on client calls.
Try it yourself
Head to the search page and work through a few of these AI/ML fuzzy searches to build intuition: perivascular fat on CT · aortic valve calcification opportunistic screening on noncontrast CT · breast cancer prediction on digital pathology slides · autism detection · gestational age prediction · a hearing aid that can also detect a pulse · foundation model based analysis of ECG · large language models · penetration test. Watch how the relevance scores, intended use, and AI Performance tables tell you when results stop being meaningful.