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The Flex-MT + is a combination TENS and EMS device which delivers nerve or muscle stimulation by applying an electrical current to electrodes, which are attached on the patient's skin. The output and waveform is adjustable according to the intended treatment of patient. The stimulator has 2 output channels, accessed through jacks at the top of the housing, so that it may stimulate either 2 or 4 patient electrodes. The device is powered by 700 mAh 4.8V Ni MH rechargeable battery pack. A patient compliance timer can memorize 60 sets of operation records; the total recordable time is 999 hours.

AI/ML Overview

The provided text is a 510(k) summary for the Flex-MT+ device. It outlines the device's technical specifications and compares them to predicate devices to establish substantial equivalence.

Here's an analysis of the acceptance criteria and the "study" (in this case, performance testing) that proves the device meets them, based on the provided text:

1. A table of acceptance criteria and the reported device performance

The document does not explicitly state "acceptance criteria" for performance, but rather demonstrates substantial equivalence by comparing the Flex-MT+ device's technical characteristics and performance to two predicate devices (K083030 EMSI TENS-EMS-14 (Flex MT) and K021100 EMPI 300 PV). The "Comment" column in the provided tables effectively acts as the "acceptance criteria" by stating whether the subject device's performance is comparable to or within acceptable limits of the predicate devices and relevant standards.

Acceptance Criteria (Derived) and Reported Device Performance (Flex-MT+)

Characteristic	Acceptance Criteria (Derived from Predicates & Standards)	Reported Device Performance (Flex-MT+)	Fulfilled?
Indications for Use	Same as predicate TENS and NMES modes.	Same as K083030 EMSI TENS-EMS-14 (Flex MT) and K021100 EMPI 300 PV	Yes
Power Source	Battery operated; battery charger available (consistent with EMPI predicate).	700 mAh 4.8V Ni-MH, rechargeable battery pack and charger	Yes
Patient Leakage Current	< 1 microamp (consistent with EMSI predicate).	< 1 microamp	Yes
Number of Output Modes	2 (consistent with EMSI predicate).	2	Yes
Number of Output Channels	2 (consistent with both predicates).	2	Yes
Method of Channel Isolation	Transformer (consistent with both predicates).	Transformer	Yes
Regulated Current or Voltage?	Regulated Voltage (consistent with EMSI predicate).	Regulated Voltage	Yes
Software/Firmware/Microprocessor	Yes (consistent with both predicates).	Yes	Yes
Automatic Overload Trip?	Provides additional safety (improved over EMSI predicate).	Yes	Yes
Automatic Shut Off?	Yes (consistent with both predicates).	Yes	Yes
Patient Override Control?	Yes (consistent with both predicates).	Yes	Yes
Indicator Display (On/Off, Low Bat, Voltage/Current)	Yes (consistent with both predicates).	Yes (1-10 bars displayed for Voltage/Current Level)	Yes
Timer Range (minutes)	Minor difference from EMPI predicate is acceptable and does not affect safety/effectiveness.	5-90 minutes, or continuous	Yes
Compliance with Voluntary Standards	ANSI/AAMI ES1-1993, IEC 60601-1-2 as applicable (consistent with EMSI predicate).	ANSI/AAMI ES1-1993, IEC 60601-1-2 as applicable	Yes
Compliance with 21 CFR 898?	Yes (consistent with both predicates).	Yes	Yes
Weight & Dimensions	Minor differences do not change device performance.	156 g (with battery), 12cm x 5.4cm x 3.3cm	Yes
Housing Materials	Plastic (consistent with both predicates).	Plastic	Yes
Waveform (TENS/EMS)	Asymmetrical biphasic / Biphasic symmetrical (consistent with both predicates).	Asymmetrical biphasic / Biphasic symmetrical	Yes
Waveform Shape	Rectangular (consistent with both predicates).	Rectangular	Yes
Maximum Output Voltage	Within the range of predicates and acceptable limits of IEC 60601-1.	43.2V @ 500Ω	Yes
Maximum Output Current	Within the range of predicates and acceptable limits of IEC 60601-1.	86.4mA @ 500Ω	Yes
Pulse Width per phase	Same or increased selection as predicates.	50-400µsec (consistent with EMPI predicate)	Yes
Pulse Frequency	Same available frequencies as predicates.	2-150 Hz	Yes
Net Charge ($\mu$C per pulse)	Within acceptable limits of IEC 60601-1.	14.6 @ 500Ω (TENS), 0 (EMS)	Yes
Maximum Current Density (mA/cm²)	Within acceptable limits of IEC 60601-1.	1.83 @500Ω (TENS), 2.82 @500Ω (EMS)	Yes
Maximum Power Density (W/cm²)	Within acceptable limits to avoid thermal burn.	0.000858W/cm2 @500Ω	Yes
Additional Features	Patient compliance timer, battery charger (consistent with predicates).	Patient compliance timer, battery charger	Yes

2. Sample size used for the test set and the data provenance

The document explicitly states: "No clinical study data is provided in support of this submission."
Therefore, there is no "test set" in the sense of clinical data from patients. The evaluation is based on technical, electrical, and mechanical performance testing, likely conducted on a single or a few units of the device to verify its specifications. The document doesn't specify the sample size for these technical performance tests. The data provenance would be laboratory testing by the manufacturer (EMSI).

3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts

Not applicable. Since no clinical study or test set involving human interpretation of medical data was conducted, no experts were used to establish ground truth in that context. The "ground truth" for the technical performance is derived from recognized industry standards (IEC, ANSI/AAMI) and the specifications of the predicate devices.

4. Adjudication method (e.g. 2+1, 3+1, none) for the test set

Not applicable, as there was no test set requiring human adjudication.

5. If a multi reader multi case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance

Not applicable. This device is a powered muscle stimulator/transcutaneous nerve stimulator, not an AI-powered diagnostic or assistive tool for human readers. No MRMC study was performed.

6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done

Not applicable. This device is a stimulator, not an algorithm, and its performance is assessed based on its physical and electrical outputs, not an algorithmic standalone performance.

7. The type of ground truth used (expert consensus, pathology, outcomes data, etc)

The "ground truth" for evaluating the Flex-MT+ device's technical characteristics and performance is based on:

Industry Standards: IEC 60601-1, IEC 60601-1-2, IEC 60601-2-10, IEC 60601-1-11, EN 60601-1-4, EN 62304, and ANSI/AAMI ES1-1993. The device's compliance with these standards serves as a form of "ground truth" for safety and basic performance.
Predicate Device Specifications: The technical specifications (e.g., maximum output voltage, current, pulse width, frequency) of the legally marketed predicate devices (K083030 EMSI TENS-EMS-14 (Flex MT) and K021100 EMPI 300 PV) serve as the benchmark for substantial equivalence. The argument is that if the new device's specifications are within acceptable ranges of previously cleared devices, it is substantially equivalent.

8. The sample size for the training set

Not applicable. This device is not an AI/machine learning model, so there is no training set.

9. How the ground truth for the training set was established

Not applicable. As there is no training set for an AI/ML model, there is no ground truth established for a training set.

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