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The circul™ pro Ring is a wireless, non-invasive, and stand-alone pulse oximeter intended to be used for spot-check and/ or continuous data collection of oxygen saturation of arterial hemoglobin (SpO2) and pulse rate (PR) through the index finger in adult patients. It can be used in home environments for up to twelve hours in non-motion and well perfused conditions. It is not intended for single-use and out-of-hospital transport use and does not have alarms.

The circul™ pro Ring is a small, wearable, non-invasive, wireless device that the user wears on one finger. The ring features an adjustable fit (by means of multiple ring sizes (S, L, XL) and a spring fit) for comfort and can be worn on any finger on either hand. The circul pro Ring relies on an optical sensor to detect oxygen saturation (SpO2) and pulse rate (PR). The sensor uses two wavelengths of LEDs: Red: with a wavelength of 660 nm ± 10 nm, Infrared: with a wavelength of 940 nm ± 20 nm. The blood oxygen percentage is calculated based on measuring the passage of the two wavelengths of light (with different absorption rates) through the body, also known as Reflective Oximetry. The integrated sensor technology works to determine the blood oxygen content by determining the light absorption when the skin is illuminated. The circul pro Ring features a spring mechanism, and the elastic structure of the embedded sensor and inner arch of the ring are ergonomically shaped to offer a snug fit, preventing it from slipping off the finger, stabilizing the sensor on the 'belly' of the finger, and minimizing twisting of the ring on the wearer's finger. This also helps to reduce the likelihood of poor SpO2 readings in patients with darker skin pigments.

Here's a breakdown of the acceptance criteria and the study proving the device meets those criteria, based on the provided FDA 510(k) summary for the circul™ pro Ring:

Acceptance Criteria and Device Performance

The primary performance metrics for this device are oxygen saturation (SpO2) and pulse rate (PR) accuracy. The acceptance criteria are largely derived from the ISO 80601-2-61:2017 standard for pulse oximeters, as well as the device's intended use and comparison with predicate devices.

Table of Acceptance Criteria and Reported Device Performance

Study Details

The study was a clinical validation performed to support the substantial equivalence claim for the circul™ pro Ring.

1. Sample Size and Data Provenance:

   • Test Set Sample Size: A total of 12 subjects were enrolled in the clinical study.
   • Data Provenance: The document does not explicitly state the country of origin for the clinical study. It describes the study as being performed "per clause 201.12.1 of ISO 80601-2-61:2017," which is an international standard. The study was conducted as a prospective clinical validation, as subjects were enrolled and measured specifically for this purpose. The document mentions four of the twelve subjects (33.3%) had dark pigmentation, indicating consideration for diverse skin tones as per pulse oximetry guidelines.

2. Number of Experts and Qualifications for Ground Truth:

   • The ground truth for SpO2 measurements was established by comparing the device readings with arterial saturation values recorded by a "Blood Oxygen, Electrolyte, and Metabolite Analyzer." This is a gold-standard method for direct arterial blood gas analysis.
   • The ground truth for pulse rate was established by comparison with a "control patient monitor (IntelliVue Patient Monitor MX500/MX550)."
   • The document does not specify the number or explicit qualifications of human experts (e.g., clinicians, laboratory technicians) involved in operating these reference devices or interpreting their output for the purpose of establishing ground truth, as the ground truth itself is derived from direct physiological measurements from a reference device.

3. Adjudication Method for the Test Set:

   • None in the context of human expert adjudication. The "ground truth" for SpO2 and PR was established by comparison with direct measurements from validated reference medical devices (Blood Oxygen, Electrolyte, and Metabolite Analyzer for SpO2; IntelliVue Patient Monitor for PR). Safety endpoints (device defects, adverse events) would have been observed and recorded by study personnel.

4. Multi Reader Multi Case (MRMC) Comparative Effectiveness Study:

   • No, an MRMC comparative effectiveness study was not performed. This study focuses on the standalone performance of the device against established reference measurements, not on its assistance to human readers or the effect on human reader performance.

5. Standalone Performance:

   • Yes, a standalone performance study (algorithm only, without human-in-the-loop performance) was performed. The study directly compared the device's measurements (SpO2 and PR) against the gold-standard reference devices.

6. Type of Ground Truth Used:

   • The ground truth used was physiological reference measurements (arterial blood gas analysis for SpO2, and a validated patient monitor for PR). This is generally considered a highly reliable and objective form of ground truth for physiological parameters.

7. Sample Size for the Training Set:

   • The document does not specify a separate training set sample size or how it was established. Given this is a 510(k) submission for a physical device (pulse oximeter) rather than a complex AI algorithm, the "training" would primarily refer to the device's internal calibration and algorithm development, which might involve laboratory testing and data collection during the R&D phase, rather than a distinct "training set" in the machine learning sense. The provided performance data relates to the validation of the finalized product.

8. How Ground Truth for Training Set Was Established:

   • As no explicit training set is mentioned in the filing for the purpose of this validation study, the method for establishing ground truth for any internal development/training data is not detailed in this document. It is implied that the device's algorithms were developed to meet the accuracy requirements of the ISO 80601-2-61 standard, which typically relies on established calibration methods and reference measurements.

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