The pulse oximeter (BM1000 & BM1000C) is designed for spot checking of the functional oxygen saturation of arterial hemoglobin (SpO2) and pulse rate for adult in clinic environment. This medical device can be reused. Not for continuously monitoring.
Device Story
Fingertip pulse oximeter (models BM1000/BM1000C) for spot-checking SpO2 and pulse rate in clinic settings. Device uses optical sensors to measure arterial hemoglobin saturation; transmits data via Bluetooth to a smartphone application. BM1000 includes plethysmogram wave display; BM1000C does not. Operated by clinicians; provides real-time SpO2 and pulse rate values, pulse bar, and history trends on mobile interface. Assists clinicians in assessing patient oxygenation status during spot checks. Benefits include non-invasive, portable, reusable monitoring of vital signs.
Clinical Evidence
Prospective clinical trial per ISO 80601-2-61 on 12 healthy adult volunteers (ages 20-41). Evaluated SpO2 accuracy during steady-state, non-motion conditions across 70-100% SaO2 range compared to arterial CO-Oximetry. Results showed Arms of 1.50 for BM1000C. No adverse effects reported. Results considered applicable to BM1000 due to identical measurement technology.
Technological Characteristics
Fingertip form factor; optical sensing principle. Powered by 3.7V rechargeable lithium battery. Connectivity via Bluetooth to smartphone app. Complies with IEC 60601-1 (safety), IEC 60601-1-2 (EMC), and ISO 80601-2-61 (pulse oximeter performance). Biocompatibility per ISO 10993-5 and ISO 10993-10. Not sterile.
Indications for Use
Indicated for adult patients in a clinic environment for spot-checking functional arterial hemoglobin oxygen saturation (SpO2) and pulse rate. Not indicated for continuous monitoring.
Regulatory Classification
Identification
An oximeter is a device used to transmit radiation at a known wavelength(s) through blood and to measure the blood oxygen saturation based on the amount of reflected or scattered radiation. It may be used alone or in conjunction with a fiberoptic oximeter catheter.
{0}------------------------------------------------
Image /page/0/Picture/0 description: The image contains the logo of the U.S. Food and Drug Administration (FDA). On the left, there is the Department of Health & Human Services logo. To the right of that is the FDA logo, which is a blue square with the letters "FDA" in white. To the right of the blue square is the text "U.S. FOOD & DRUG ADMINISTRATION" in blue.
April 4, 2018
Shanghai Berry Electronic Tech Co., Ltd % Ray Wang General Manager Beijing Believe Technology Service Co., Ltd. 5-402, Building #27, No. 56, LiangXiang East Rd., FangShan District Beijing, 102401 CN
Re: K172141
Trade/Device Name: Pulse Oximeter Regulation Number: 21 CFR 870.2700 Regulation Name: Oximeter Regulatory Class: Class II Product Code: DQA Dated: March 1, 2018 Received: March 5, 2018
Dear Ray Wang:
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 adverse events) (21 CFR 803); good
{1}------------------------------------------------
manufacturing practice requirements as set forth in the quality systems (OS) regulation (21 CFR Part 820); and if applicable, the electronic product radiation control provisions (Sections 531-542 of the Act); 21 CFR 1000-1050.
Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21 CFR 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.
For comprehensive regulatory information about medical devices and radiation-emitting products, including information about labeling regulations, please see Device Advice (https://www.fda.gov/MedicalDevices/DeviceRegulationandGuidance/) and CDRH Learn (http://www.fda.gov/Training/CDRHLearn). Additionally, you may contact the Division of Industry and Consumer Education (DICE) to ask a question about a specific regulatory topic. See the DICE website (http://www.fda.gov/DICE) for more information or contact DICE by email (DICE@fda.hhs.gov) or phone (1-800-638-2041 or 301-796-7100).
Sincerely,
# Michael J. Ryan -S
for Tina Kiang, Ph.D. Acting Director Division of Anesthesiology, General Hospital, Respiratory, Infection Control, and Dental Devices Office of Device Evaluation Center for Devices and Radiological Health
Enclosure
{2}------------------------------------------------
# Indications for Use
510(k) Number (if known) K172141
Device Name Pulse Oximeter
Indications for Use (Describe)
The pulse oximeter (BM1000 & BM1000C) is designed for spot checking of the functional oxygen saturation of arterial hemoglobin (SpO2) and pulse rate for adult in clinic environment. This medical device can be reused. Not for continuously monitoring.
| Type of Use ( <i>Select one or both, as applicable</i> ) |
|----------------------------------------------------------|
|----------------------------------------------------------|
X Prescription Use (Part 21 CFR 801 Subpart D)
| Over-The-Counter Use (21 CFR 801 Subpart C)
#### CONTINUE ON A SEPARATE PAGE IF NEEDED.
This section applies only to requirements of the Paperwork Reduction Act of 1995.
#### *DO NOT SEND YOUR COMPLETED FORM TO THE PRA STAFF EMAIL ADDRESS BELOW.*
The burden time for this collection of information is estimated to average 79 hours per response, including the time to review instructions, search existing data sources, gather and maintain the data needed and complete and review the collection of information. Send comments regarding this burden estimate or any other aspect of this information collection, including suggestions for reducing this burden, to:
> Department of Health and Human Services Food and Drug Administration Office of Chief Information Officer Paperwork Reduction Act (PRA) Staff PRAStaff@fda.hhs.gov
"An agency may not conduct or sponsor, and a person is not required to respond to, a collection of information unless it displays a currently valid OMB number."
{3}------------------------------------------------
# Tab #3 510(k) Summary
This 510(k) Summary is being submitted in accordance with requirements of SMDA 1990 and Title 21, CFR Section 807.92.
The assigned 510(k) Number: K172141
- 1. Date of Preparation: 03/27/2018
- 2. Sponsor Identification
Shanghai Berry Electronic Tech Co., Ltd Unit C, 1st Floor, 7th Building, No.1188 Lianhang Road, Minhang District,Shanghai, China 201112 Establishment Registration Number: 3009241523
Contact Person: Xuezhi Yin Position: General Manager Tel: +86-21-5853 1958 Fax: +86-21-5853 0468 Email: berrymedical@hotmail.com
- 3. Designated Submission Correspondent
Mr. Ray Wang
#### Beijing Believe Technology Service Co., Ltd.
5-402, Building #27, YangGuang YiShang, No. 56, LiangXiang East Rd., FangShan District, BeiJing, China 102401
Tel: +86-18910677558 Fax: +86-10-80337041 Email: ray.wang@believe-med.com
{4}------------------------------------------------
#### 510(k) Summary
- Identification of Proposed Device 4.
Trade Name: Pulse Oximeter Common Name: Pulse Oximeter Model(s): BM1000/BM1000C
Regulatory Information Classification Name: Oximeter Classification:II Product Code:DQA Regulation Number: 21 CFR 870.2700 Review Panel:Anesthesiology;
Intended Use Statement:
The pulse oximeter (BM1000 & BM1000C) is designed for spot checking of the functional oxygen saturation of arterial hemoglobin (SpO2) and pulse rate for adult in clinic environment. This medical device can be reused. Not for continuously monitoring.
#### Device Description
The proposed device, pulse oximeter, includes two models in this application, BM1000C. The two proposed devices all are fingertip device; they are share the following same features:
- ★ Spot check and display SpO2 and PR value;
- ★ Low battery capacity indicator;
- ★ Finger off indicator;
- ★ wireless connection function
Beside the features above, the BM1000 can display Plethysmogram wave, but the BM1000C deoesn't have this function.
The pulse oximeter (BM1000 & BM1000C) is designed for spot checking of thefunctional oxygen saturation of arterial hemoglobin (SpO2) and pulse rate for adult in clinic environment. This medical device can be reused. Not for continuously monitoring.
The proposed device is not provided sterile and is not a reprocessed single-use device.
- 5. Identification of Predicate Device(s)
Predicate Device :
510(k) Number: K141362 Product Name: Pulse Oximeter CMS50EW
{5}------------------------------------------------
#### 510(k) Summary
Model Name: CMS50EW Manufacturer: Contec Medical System Co., Ltd.
- Non-Clinical Test Conclusion 6.
Non clinical tests were conducted to verify that the proposed device met all design specifications as was Substantially Equivalent (SE) to the predicate device. The test results demonstrated that the proposed device complies with the following standards:
- IEC 60601-1:2005/A1:2012, Medical electrical equipment- Part 1: General requirements for basic safety, a. and essential performance.
- IEC 60601-1-2:2014, Medical Electrical Equipment Part 1-2: General Requirements For Basic Safety b. And Essential Performance - Collateral Standard: Electromagnetic Disturbances - Requirements And Tests
- ISO 80601-2-61:2011,Medical electrical equipment Part 2-61: Particular requirements for basic safety C. and essential performance of pulse oximeter equipment.
- d. ISO 10993-5:2009, Biological evaluation of medical devices - Part 5: Tests for In Vitro cytotoxicity.
- ISO 10993-10:2010, Biological evaluation of medical devices Part 10: Tests for irritation and skin e. sensitization.
- Shelf Life Testing f.
- SpO2 Accuracy and Pulse Rate Accuracy Performance Testing (Test after the repeated clean & disinfection g. conditions).
- h. SpO2 Accuracy and Pulse Rate Accuracy Performance Testing (Test under the normal conditions).
- SpO2 Accuracy and Pulse Rate Accuracy Performance Testing (Test under the low perfusion conditions). i.
- SpO2 Accuracy and Pulse Rate Accuracy Performance Testing (Test under the wireless Bluetooth j. conditions without outside interference).
- SpO2 Accuracy and Pulse Rate Accuracy Performance Testing (Test under the wireless Bluetooth k. conditions with outside interference).
- Wireless coexistence testing. 1.
- FCC Part 15C Testing. m.
- Software Validation and Verification Testing. n.
- 7. Clinical Test Conclusion
The clinical trial was performed according to Clause 201.12.1.101.2 and Annex EE.2 of ISO 80601-2-61:2011 Procedure for invasive laboratory testing on healthy volunteers.
The purpose of the clinical trial was to evaluate the SpO2 accuracy performance of the BM1000C Fingertip Pulse Oximeter during stationary (non-motion) conditions over a wide range of arterial blood oxygen saturation levels as compared to arterial blood CO-Oximetry.
After Institutional Review Board (IRB) approval, 12 healthy adult volunteer subjects (ages 20-41yr, 42-95kg, 155-181cm, with light to dark pigmentation) were included in the study conducted Nov. 9-10,
{6}------------------------------------------------
#### 510(k) Summary
2013 to evaluate the SpO2 accuracy performance of proposed devices.
The system was evaluated during steady state/non-motion conditions with various levels of induced hypoxia resulting in stable oxygen saturation levels between 100% SaO2. Arterial blood samples were drawn during simultaneous data collection from the test devices. The blood was immediately analyzed on reference CO-Oximetry providing functional SaO2 for the basis of the SpO2 accuracy comparison.
No adverse effects or complications occurred during the study.
The SpO2 accuracy performance results showed the fingertip pulse oximeter to have an Arms of 1.50 (BM1000C) during steady state conditions over the range of 70-100%.
Because the BM1000C and BM1000 has only difference as Plethysmogram wave display, no difference would effects the measurement accuracy, so the clinical test result of BM1000C could be consider as applicable to BM1000.
{7}------------------------------------------------
### 8. Substantially Equivalent (SE) Comparison
## Table 7-1 Comparison of Technology Characteristics
| ITEM | Proposed Device<br>Pulse Oximeter (BM1000 & BM1000C) | Predicate Device Pulse Oximeter CMS50EW (K141362) | Remark | |
|------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------|-----------|
| Product Code | DQA | DQA | SE | |
| Regulation No. | 21 CFR 870.2700 | 21 CFR 870.2700 | SE | |
| Class | 2 | 2 | SE | |
| Intended Use | The pulse oximeter (BM1000 & BM1000C) is designed for spot checking of the functional oxygen saturation of arterial hemoglobin (SpO2) and pulse rate for adult in clinic environment. This medical device can be reused. Not for continuously monitoring. | The Pulse Oximeter CMS50EW is a non-invasive device intended for spot-check or continuous monitoring of non-invasive oxygen saturation of arterial hemoglobin (SpO2) and the pulse rate through the finger of adult patients in home and hospital environments (including clinical use internist/surgery,anesthesia, and intensive care settings). The device is reusable and not intended for out-of-hospital transport use. | Analysis 1 | |
| Features | BM1000 %SpO2 and PR measurement, Plethysmogram wave, Bluetooth | %SpO2 and PR measurement, Pulse bar, Pulse wave | SE | |
| | BM1000C %SpO2 and PR measurement, Bluetooth | Alarm function, Bluetooth | SE | |
| configuration | | Fingertip | Fingertip | SE |
| SpO2 measurement range | | 0%-100% | 0%-100% | SE |
| SpO2accuracy | | $±3% (70%~100%); Undefined for <70%$ | $70%~100%:±2%, 0~69%,unspecified$ | Analyse 2 |
| PR measurement range | | 25~250bpm | 30bpm~250bpm | Analyse 3 |
| PR accuracy | | $±2 bpm$ | $±2bpm or ±2% (select the larger)$ | SE |
| Power Supplier | | Two 1.5V AAA alkaline batteries | Voltage 3.7 rechargeable lithium battery | Analyse 4 |
| Wireless Connection | | Bluetooth | Bluetooth | SE |
{8}------------------------------------------------
| The data transported via<br>wireless connection | SpO2 value, PR value and Pulse Bar | SpO2 value, PR value, Pulse Wave, Pulse Bar and Alarm<br>Set parameters | |
|-------------------------------------------------|-----------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|
| Data received terminal | Smart Phone loaded App | PC with BT adaptor | Analyse 5 |
| Terminal Functions | SpO2 display, PR display, Pulse Bar display, data storage,<br>history data trend drawn, User Registration | SpO2 display, PR display, Pulse Wave display, Pulse Bar<br>display, alarm limits setting, data storage, history data<br>trend drawn, User information management, print report | |
| Electrical Safety | Comply with IEC 60601-1 | Comply with IEC 60601-1 | SE |
| EMC | Comply with IEC 60601-1-2 | Comply with IEC 60601-1-2 | SE |
| Performance | Comply with ISO 80601-2-61 | Comply with ISO 80601-2-61 | SE |
| Biocompatibility | ISO10993-5&ISO10993-10 | ISO10993-5&ISO10993-10 | SE |
| Label and Labeling | Meet FDA's Requirements | Meet FDA's Requirements | SE |
{9}------------------------------------------------
#### SE Analysis :
The proposed device has same classification for use, similar technical specifications, same applied Standards with the predicate device.
The main differences are included as followings:
Analysis 1: The indication for use of proposed device, but the differences are indication reduction reduction, the proposed device does not include the indications, such as "continuous monitoring" and "home predicate device, such indications retuction do not raise different questions of safety or effectiveness, because the use environment for the use environment of the predicate device and the proposed device still maintains the core function as the oximeter, spot-check of non-invention of arterial hemoglobin (SpO2), and which has been validated by the non-clinical tests conducted.
Analyse 2: The SpO2 accuracy of proposed device. However it meets the requirements of ISO 80601-2-61, which FDA reognizes. Therefore, this difference is considered to not raise different questions of safety or effectiveness.
Analyse 3 . The PR measurement range of the is different than that of the measurement range is considered to be able to cover the general pulse rate of healthy people and patients. In a PR measurement range is clearly on the proposed labeling to remind the user. This difference is considered to not raise different questions of safety or effectiveness.
Analyse 4: Athough the Power supply specifications of of the proposed device.but both the predicate device and the proposed device have passed the IEC60601-1 standard, we believe the stirent grestions of the effectiveness and safety compared with the predicate device.
Analyse 5: The proposed device and predicate device terminal, Smart Phone VS PC, we have conducted the Wireless Coesistence Test and the results shown that the different receiver terminal will not raise different questions of the effectiveness and safety.
The proposed device and predicate device has different in wiretions, but all such functions of proposed device are covered by prodicate's, so we believe these differences will not raise different questions of the effectiveness and safety compared with the predicate device.
{10}------------------------------------------------
### 9. Substantially Equivalent (SE) Conclusion
The clinical and non-clinical data support that the proposed device is as safe and as effective as the predicate device and does meet its design specification, and which are comparable to the predicate device. Also, the differences in the technological characteristics have been demonstrated to be substantially equivalent and thus the subject device is considered substantially equivalent to the predicate device.
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.