firefly T-2

K201131 · Firstkind Limited · NGX · May 28, 2020 · Physical Medicine

Device Facts

• Record ID: K201131
• Device Name: firefly T-2
• Applicant: Firstkind Limited
• Product Code: NGX · Physical Medicine
• Decision Date: May 28, 2020
• Decision: SESE
• Submission Type: Special
• Regulation: 21 CFR 890.5850
• Device Class: Class 2

Intended Use

The firefly T-2 is intended for stimulation of healthy muscles in order to improve or facilitate muscle performance. The firefly™ T-2 is not intended to be used in conjunction with therapy or treatment of medical conditions of any kind.

Device Story

Disposable, fully integrated neuromuscular stimulator; constant current pulse generator; embedded software; battery; over-molded plastic casing; silver electrode with hydrogel coating. Applied to posterior aspect of knee over common peroneal nerve; stimulates calf muscles via motor neuron activation; increases blood flow. Operated by user via two buttons (On/Off, intensity adjustment). Asymmetric biphasic waveform; 1 Hz frequency; isometric stimulation of leg/foot muscles mimicking walking cadence. Output intensity controlled by pulse width (seven levels). Provides active recovery. Intended for OTC use in athletic training facilities or home. Benefits include improved muscle performance through isometric stimulation.

Clinical Evidence

Bench testing only. Verification and validation activities included electrical safety and electromagnetic compatibility testing per IEC 60601-1, IEC 60601-2-10, and IEC 60601-1-2. Hardware/firmware testing included verification of output waveform characteristics via oscilloscope at various loads (500Ω, 2kΩ, 10kΩ) and comparison of output currents against the predicate device. Results demonstrated the device meets all predefined technical and functional specifications.

Technological Characteristics

Powered muscle stimulator; constant current; asymmetric biphasic waveform; 1 Hz frequency. Materials: plastic injection molded housing, silver electrode, hydrogel. Dimensions: 7.8" x 1.2" x 0.4". Power: non-replaceable CR2032 lithium coin cell. Connectivity: standalone. Standards: IEC 60601-1:2005+A1:2012, IEC 60601-2-10:2016, IEC 60601-1-2:2014, ISO 10993-1:2009. Software: embedded firmware controlling pulse width and intensity.

Indications for Use

Indicated for stimulation of healthy muscles to improve or facilitate muscle performance in individuals. Not for use in therapy or treatment of medical diseases or conditions.

Regulatory Classification

Identification

A powered muscle stimulator is an electrically powered device intended for medical purposes that repeatedly contracts muscles by passing electrical currents through electrodes contacting the affected body area.

Predicate Devices

• firefly™ T-1 (K134001)

Submission Summary (Full Text)

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Image /page/0/Picture/0 description: The image contains the logo of the U.S. Food and Drug Administration (FDA). On the left 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.

May 29, 2020

Firstkind Limited % Sheila Hemeon-Heyer President Heyer Regulatory Solutions LLC 125 Cherry Lane Amherst, Massachusetts 01002

Re: K201131 Trade/Device Name: firefly T-2 Regulation Number: 21 CFR 890.5850 Regulation Name: Powered muscle stimulator Regulatory Class: Class II Product Code: NGX

Dear Sheila Hemeon-Heyer:

The Food and Drug Administration (FDA) is sending this letter to notify you of an administrative change related to your previous substantial equivalence (SE) determination letter dated May 28, 2020. Specifically, FDA is updating this SE Letter 510(k) summary file error as an administrative correction.

Please note that the 510(k) submission was not re-reviewed. For questions regarding this letter please contact Dr. Heather Dean, OHT5: Office of Neurological and Physical Medicine Devices, 240-402-9874, [e-mail].

Sincerely,

# Heather L. Dean -S

Heather Dean, PhD Acting Assistant Director, Acute Injury Devices DHT5B: Division of Neuromodulation and Physical Medicine Devices OHT5: Office of Neurological and Physical Medicine Devices Office of Product Evaluation and Ouality Center for Devices and Radiological Health

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Image /page/1/Picture/0 description: The image contains the logo of the U.S. Food and Drug Administration (FDA). On the left is the Department of Health & Human Services logo. To the right of that is the FDA logo in blue. Underneath the FDA logo is the text "U.S. FOOD & DRUG ADMINISTRATION".

May 28, 2020

Firstkind Limited % Sheila Hemeon-Heyer President Heyer Regulatory Solutions LLC 125 Cherry Lane Amherst, Massachusetts 01002

Re: K201131

Trade/Device Name: fireflyTM T-2 Regulation Number: 21 CFR 890.5850 Regulation Name: Powered muscle stimulator Regulatory Class: Class II Product Code: NGX Dated: April 28, 2020 Received: April 28, 2020

Dear Sheila Hemeon-Heyer:

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. Although this letter refers to your product as a device, please be aware that some cleared products may instead be combination products. The 510(k) Premarket Notification Database located at https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm identifies combination product submissions. 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.

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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) for devices or postmarketing safety reporting (21 CFR 4, Subpart B) for combination products (see https://www.fda.gov/combination-products/guidance-regulatory-information/postmarketing-safety-reportingcombination-products); good manufacturing practice requirements as set forth in the quality systems (QS) regulation (21 CFR Part 820) for devices or current good manufacturing practices (21 CFR 4, Subpart A) for combination products; 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 https://www.fda.gov/medical-device-safety/medical-device-reportingmdr-how-report-medical-device-problems.

For comprehensive regulatory information about mediation-emitting products, including information about labeling regulations, please see Device Advice (https://www.fda.gov/medicaldevices/device-advice-comprehensive-regulatory-assistance) and CDRH Learn (https://www.fda.gov/training-and-continuing-education/cdrh-learn). 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 (https://www.fda.gov/medical-device-advice-comprehensive-regulatoryassistance/contact-us-division-industry-and-consumer-education-dice) for more information or contact DICE by email (DICE(@fda.hhs.gov) or phone [phone] or 301-796-7100).

Sincerely.

## Amber T. Ballard -S

For Vivek Pinto, PhD Director DHT5B: Division of Neuromodulation and Physical Medicine Devices OHT5: Office of Neurological and Physical Medicine Devices Office of Product Evaluation and Ouality Center for Devices and Radiological Health

Enclosure

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## Indications for Use

510(k) Number (if known) K201131

Device Name firefly™ T-2

Indications for Use (Describe)

The firefly T-2 is intended for stimulation of healthy muscles in order to improve or facilitate muscle performance. The firefly™ T-2 is not intended to be used in conjunction with therapy or treatment of medical conditions of any kind.

| Type of Use (Select one or both, as applicable) | |
|-------------------------------------------------|--|
|-------------------------------------------------|--|

Prescription Use (Part 21 CFR 801 Subpart D)

|X | Over-The-Counter Use (21 CFR 801 Subpart C)

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## 510(k) Summary

This summary of 510(k) safety and effectiveness information is being submitted in accordance with the requirements of 21 CFR 807.92.

| A. | Submitter: | Firstkind Limited<br>Hawk House<br>Peregrine Business Park<br>High Wycombe, UK<br>HP13 7DL |
|----|----------------------------|-------------------------------------------------------------------------------------------------------------------|
| | Contact:<br>Tel:<br>Email: | Neil Buckley, Head of Quality and Regulatory Affairs<br>[phone]<br>[e-mail] |

- Date Prepared: May 28, 2020 B.
#### C. Device Name and Classification Information:

| Trade Name: | firefly™ T-2 |
|----------------------|---------------------------------------------------|
| Common Name: | Powered Muscle Stimulator for Muscle Conditioning |
| Classification Name: | Stimulator, Muscle Powered |
| Regulation: | 21 CFR 890.5850 |
| Product Code: | NGX |
| Review Panel: | 89, Physical Medicine |

#### D. Predicate Device: K134001, firefly™ T-1

#### Device Description: ய்

The firefly™ T-2 Neuromuscular Stimulator (firefly™ T-2) is a disposable, fully integrated unit composed of a constant current pulse generator with embedded software and battery enclosed in an over-molded plastic casing, and a silver electrode with a hydrogel coating that provides a means of attachment of the device and electrical contact with the patient. Two buttons are used to control the On/Off function and increase or decrease the intensity level of the device output, which is achieved through changes in the delivered pulse width. The firefly™ T-2 is applied so that the electrodes lie over the common peroneal nerve behind the knee. Stimulation of the common peroneal nerve causes contraction of the calf muscles through the direct activation of the motor neurons, resulting in increased blood flow.

The stimulus intensity varies with the pulse width, which can be set to one of seven levels for the firefly™ T-2. The asymmetric biphasic waveform results in a net charge of zero to the patient during each pulse cycle. The pulse rate is fixed at a frequency of 1 Hz and is

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used to isometrically stimulate the leg and foot muscles with a cadence and energy similar to that of walking.

Electrical contact is made with the patient through a hydrogel layer applied during manufacture to the integrated electrode. The patient contacting materials have been previously tested per the requirements of ISO 10993-1 and shown to be biocompatible for prolonged (up to 30 days) contact with intact skin. There are no separate electrode leads or electrodes.

## F. Indications for Use:

The firefly™ T-2 is intended for stimulation of healthy muscles in order to improve or facilitate muscle performance. The firefly™ T-2 is not intended to be used in conjunction with therapy or treatment of medical diseases or medical conditions of any kind.

| Parameter | Predicate Device<br>firefly™ T-1 (K134001) | Subject Device<br>firefly™ T-2 | Comparison |
|---------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------|
| Use environment | Over-the-counter (non-prescription) use in athletic training facilities or the home. | Over-the-counter (non-prescription) use in athletic training facilities or the home. | Same |
| Anatomical Sites | The firefly with the embedded electrodes is applied to the posterior aspect of the knee only for stimulation of the peroneal nerve. | The firefly with the embedded electrodes is applied to the posterior aspect of the knee only for stimulation of the peroneal nerve. | Same |
| Stimulator Parameters | | | |
| Power source | One CR2032 primary lithium coin cell. Not replaceable by user | One CR2032 primary lithium coin cell. Not replaceable by user | Same |
| -Method of Line Current Isolation | N/A | N/A | Same |
| -Patient Leakage Current<br>-Normal Condition | < 20μΑ | < 20μΑ | |
| -Single Fault<br>Condition | < 20μΑ | < 20μΑ | |
| Parameter | firefly™ T-1 | firefly™ T-2 | Comparison |
| Number of output<br>modes | Single mode with seven<br>discrete stimulation settings<br>corresponding to the seven<br>pulse widths. | Single mode with seven<br>discrete stimulation settings<br>corresponding to the seven<br>pulse widths. | Same |
| Number of output<br>channels /<br>synchronous or<br>alternating? | Single channel<br>N/A | Single channel<br>N/A | Same |
| -Method of channel<br>isolation | N/A (single channel) | N/A (single channel) | Same |
| Regulated current<br>or regulated<br>voltage | Current | Current | Same |
| Microprocessor<br>controlled? | Yes | Yes | Same |
| Automatic<br>overload trip | Yes | Yes | Same |
| Automatic no-load<br>trip | Yes | Yes | Same |
| Automatic shut-off | Yes | Yes | Same |
| User over-ride<br>control | Yes | Yes | Same |
| Indicator display:<br>- On/Off status | Yes | Yes | Same |
| - Low battery<br>-Voltage / current<br>level | Yes (device switches off)<br>N/A (device has fixed<br>constant current). Stimulus<br>level is indicated by flashing<br>LED. | Yes (device switches off)<br>N/A (device has fixed<br>constant current). Stimulus<br>level is indicated by flashing<br>LED. | Same |
| Timer range in<br>minutes | 1800 minutes maximum<br>(device is disabled after 30<br>hours battery run time) | 1800 minutes maximum<br>(device is disabled after 30<br>hours battery run time) | Same |
| Compliance with<br>voluntary<br>standards | Yes<br>IEC 60601-1:1998 A1, A2<br>IEC 60601-2-10:1987, A1<br>EN 60601-1-2:2007<br>ISO 10993-1:2009 | Yes<br>IEC 60601-1:2005<br>IEC 60601-2-10:2012<br>EN 60601-1-2:2015<br>ISO 10993-1:2009 | firefly T-2 complies<br>with current<br>recognized versions of<br>applicable standards. |
| Compliance with<br>21 CFR 898 | N/A (electrodes are integral<br>with the device, there are no<br>separate leads) | N/A (electrodes are integral<br>with the device, there are no<br>separate leads) | Same |
| Parameter | firefly™ T-1 | firefly™ T-2 | Comparison |
| Weight | 18 g | 10g | firefly T-2 is slightly<br>lighter than T-1. |
| Dimensions | 6" x 1.6" x 0.4" | 7.8" x 1.2" x 0.4" | firefly T-2 is slightly<br>longer and narrower<br>than T-1. |
| Housing material<br>and construction | Plastic injection molding | Plastic injection molding | Same |
| Waveform Parameters | | | |
| Mode or Program<br>Name | N/A, single mode<br>Used for Active Recovery | N/A, single mode<br>Used for Active Recovery | Same |
| Waveform<br>- Pulsed<br>monophasic or<br>biphasic<br>- Shape | Biphasic (asymmetrical<br>biphasic with zero net DC)<br>Rectangular, with charge<br>balancing second phase | Biphasic (asymmetrical<br>biphasic with zero net DC)<br>Rectangular, with charge<br>balancing second phase | Same |
| Maximum output<br>voltage (± 15%) | 13.5 V @ 500 Ω<br>54 V @ 2 kΩ<br>110 V @ 10 k Ω | 14.0 V @ 500 Ω<br>53.5 V @ 2 kΩ<br>255 V @ 10 k Ω | Design of firefly T-2 has<br>been improved to<br>maintain desired<br>current output even at<br>high loads. |
| Maximum output<br>current (± 15%) | 27 mA @ 500 Ω<br>27 mA @ 2 kΩ<br>11 mA @ 10 kΩ | 27.9 mA @ 500 Ω<br>26.8 mA @ 2 kΩ<br>25.5 mA @ 10 kΩ | Design of firefly T-2<br>has been improved to<br>maintain desired<br>current output even at<br>high loads. |
| Pulse widths | 70, 100, 140, 200, 280, 400,<br>560 µs | 50, 70, 100, 140, 200, 280,<br>400 µs | firefly T-2 pulse widths<br>decreased at each<br>setting to compensate<br>for better current<br>output. |
| Frequency | 1 Hz | 1 Hz | Same |
| For interferential<br>modes only:<br>-Beat Frequency<br>(Hz) | N/A | N/A | Same |
| For multiphasic<br>waveforms only<br>-Symmetrical | No | No | Same |
| phases<br>-Phase<br>duration(s) | 70-560 µs for positive phase,<br>second (negative) phase is an<br>exponential decay with a 0.1 s<br>time constant. | 50-400 µs for positive phase,<br>second (negative) phase is<br>an exponential decay with a<br>0.1 s time constant. | Same except for<br>reduced pulse<br>duration at each<br>setting for firefly T-2 |
| Parameter | firefly™ T-1 | firefly™ T-2 | Comparison |
| Net charge | 0 μC at 500 Ω | 0 μC at 500 Ω | Same |
| -How achieved | Capacitor coupling | Capacitor coupling | Same |
| Maximum phase<br>charge (@500Ω) | 18.3 μC | 18.3 μC | Same |
| Maximum current<br>density (@500Ω) | 0.169 mA/cm² rms | 0.169 mA/cm² rms | Same |
| Maximum avg<br>current (average<br>absolute value),<br>mA (@500Ω) | 0.037 mA | 0.037 mA | Same |
| Maximum avg<br>power density<br>(using smallest<br>electrodes)<br>(@500Ω) | 0.000044 W/cm² | 0.000044 W/cm² | Same |
| Burst mode | N/A, single pulse, no burst<br>mode | N/A, single pulse, no burst<br>mode | Same |
| ON Time (seconds)<br>/ OFF Time<br>(seconds) | N/A Stimulation is continually<br>on or off when power is on or<br>off. | N/A Stimulation is continually<br>on or off when power is on or<br>off. | Same |
| Electrodes | Two electrodes integrated<br>within the device. A single<br>piece of hydrogel covers the<br>electrodes and the underside of<br>the electronics housing.<br>Biocompatibility for the<br>hydrogel has been established. | Two electrode integrated<br>within the device. The<br>hydrogel is in 3 discrete<br>sections covering each of<br>the electrodes and the<br>anterior section of strap.<br>Biocompatibility for the<br>hydrogel has been<br>established. | Design of firefly T-2 has<br>been improved to<br>prevent leakage current<br>between the two<br>electrodes through the<br>hydrogel. |
| Cables/ connectors | Integrated device: no<br>separate cables | Integrated device: no<br>separate cables | Same |
| User Contact | Contact is made through<br>integrated self-adhesive<br>electrodes. The firefly T-1 is a<br>single channel device | Contact is made through<br>integrated self-adhesive<br>electrodes. The firefly T-2 is a<br>single channel device | Same |

## G. Technical Comparison with the Predicate Device and Discussion of Differences

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## Discussion of differences

The firefly™ T-2 device has been redesigned from the original firefly™ T-1 device for more efficient current delivery, enabling shorter pulse widths at each stimulus level. Because the T-1 device had a sinqle piece of hydrogel covering both electrodes: there was a small amount of leakage current between the electrodes. The leakage current could reduce the effectiveness of stimulation in users with high skin resistance. The T-2 device was redesigned using discrete pieces of hydrogel over each electrodes to prevent any current leakage. To compensate for the result that more current is available to the uiser, the pulse widths have been reduced to ensure that the same charge is delivered for each pulse width setting.

The firefly™ T-2 interface has been designed to improve ease of use. Using + and buttons to increase and decrease intensity is somewhat easier than using different length presses on a single button. The two LED indicators used with the T-2 make it easier to see whether the device is operating. One LED for the T-2 device flashes rapidly when the switch is operated by a button press, providing the operator with visual feedback that the button has been operated. The other LED indicates the stimulation level in the same manner as for the T-1.

The changes resulting in the firefly™ T-2 device do not alter the device intended use, indications for use or fundamental scientific technology, and none of the changes significantly affect the safety or effectiveness of the device.

## H. Testing to Validate Changes

The device changes described in this Special 510(k) were implemented under the company's design change procedures. A risk assessment of the changes resulted in the following verification and validation activities:

Electrical Safety and Electromagnetic Compatibility Testing - The firefly™ T-2 has been certified to comply with the applicable clauses of the following standards:

- o IEC 60601-1:2005 + A1:2012: Medical Electrical Equipment - Part 1: General Requirements for Safety (FDA recognition #19-40
- IEC 60601-2-10:2016 Medical electrical equipment Part 2-10: Particular . requirements for the safety of nerve and muscle stimulators (FDA recognition # 17-16)
- . IEC 60601-1-2: 2014 Medical electrical equipment - Part 1-2: General requirements for basic safety and essential performance - Collateral standard: Electromagnetic compatibility - Requirements and tests (FDA recognition #19-8)

## Hardware/Firmware Testing

As with the predicate device, the firefly™ T-2 hardware and firmware work together and need to be tested together in order to verify the correct functioning of the device. Testing included the following:

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- Verification of output waveform characteristics via oscilloscope output tracings at . 500Ω, 2kΩ and 10kΩ
- Measurements to compare the firefly™ T-2 output currents to those of the firefly™ . T-1 under loads ranging from 500Ω to 10kΩ
- Validation of all firefly™ T-2 hardware and firmware functionality ●

All test results demonstrated that the firefly™ T-2 meets the predefined device technical and functional requirements specifications.

## I. Conclusions

The information and testing presented in this 510(k) demonstrate that the firefly™ T-2 performs as designed and intended and is substantially equivalent to the predicate device, the firefly™ T-1.