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The geko W-2 is indicated for:

• Increasing local blood circulation
• Edema reduction
• Increasing microcirculatory blood flow in lower limb soft tissue of patients with venous insufficiency and/or ischemia while the device is active

The geko™ W-2 Neuromuscular Stimulator (geko™ W-2) is a disposable, fully integrated unit composed of a constant current pulse generator with embedded software, a lithium coin-cell battery enclosed in an over-molded plastic casing, and a silver electrode with a hydrogel coating which 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 choosing one of 10 stimulus settings. The geko™ W-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 pulse rate is fixed at a frequency of 1 Hz and is used to isometrically stimulate the calf and foot muscles with a cadence and energy similar to that of walking. Each geko™ W-2 provides two 6 hour treatments with a 6 hour minimum rest period between treatments. Two optional accessories are available to hold the geko W-2 in place during treatment, if needed: a knee strap and an adhesive tape.

The provided text describes the acceptance criteria and the study results for the geko™ W-2 device, particularly focusing on the added indication for increasing microcirculatory blood flow.

Here's a breakdown of the requested information:

1. Table of Acceptance Criteria and Reported Device Performance

The FDA clearance is based on proving substantial equivalence for the new indication ("Increasing microcirculatory blood flow in lower limb soft tissue of patients with venous insufficiency and/or ischemia while the device is active"). The acceptance criteria are implicitly met by demonstrating this substantial equivalence through clinical study outcomes. The reported device performance is the statistically significant increase in both flux and pulsatility (measures of microcirculatory blood flow).

2. Sample Sizes Used for the Test Set and Data Provenance

• Study #1:
  • Sample Size: 16 subjects (10 males, 6 females).
  • Data Provenance: United Kingdom (Ealing Hospital), Retrospective (published study). The text states "This study was conducted to evaluate..." suggesting it was a specific study, not necessarily retrospective in the sense of analyzing existing patient records, but rather a completed study whose data was submitted.
• Study #2:
  • Sample Size: 8 subjects (4 males, 4 females).
  • Data Provenance: United Kingdom (Aneurin Bevan University Health Board and Cardiff and Vale University Health Board), Retrospective (published study). Similar to Study #1, it was a completed study.
• Study #3 (Safety data):
  • Sample Size: 25 patients (22 males, 3 females).
  • Data Provenance: UK (Welsh Wound Innovation Centre), Retrospective (published study).
• Study #4 (Safety data, interim report):
  • Sample Size: 33 subjects (21 male, 12 female).
  • Data Provenance: UK and EU (multi-center study), Prospective (ongoing study, interim report).

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts

The provided information does not specify the use of experts to establish a "ground truth" through a consensus read or similar method for the microcirculatory blood flow measurements. The studies used objective measurements (Laser Speckle Contrast Imaging - LSCI) to quantify blood flow. The "ground truth" here is the direct physiological measurement of blood flow changes.

4. Adjudication Method for the Test Set

Not applicable. As noted above, the "ground truth" was established through direct physiological measurements (LSCI), not through human assessment requiring adjudication.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done, And What Was the Effect Size of How Much Human Readers Improve With AI vs Without AI Assistance

Not applicable. The geko™ W-2 is a physical medical device (neuromuscular stimulator), not an AI algorithm for image analysis or diagnosis. Therefore, MRMC studies involving human readers and AI assistance are not relevant to this device.

6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done

Not applicable. This is not an AI algorithm. The device's performance is standalone in the sense that it operates as designed to stimulate muscle, leading to the physiological effect of increased blood flow.

7. The Type of Ground Truth Used

The ground truth for the effectiveness studies (Study #1 and #2) was objective physiological measurement: Laser Speckle Contrast Imaging (LSCI) data, which quantifies microcirculatory blood flow (flux and pulsatility).

8. The Sample Size for the Training Set

Not applicable. The geko™ W-2 device is a hardware device with embedded software that controls its function (e.g., pulse rate, intensity). It is not an AI/machine learning model that undergoes a "training" phase with a dataset.

9. How the Ground Truth for the Training Set Was Established

Not applicable. See point 8.

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