The noninvasive INVOS 3100A Cerebral Oximeter should be used in adults as an adjunct monitor of trends in regional hemoglobin oxygen saturation of blood in the brain of an individual. Because INVOS values are relative within an individual, the INVOS should not be used as the sole basis for decisions as to diagnosis or therapy. The value of data from the INVOS has not been demonstrated in disease states.

Device Description

The principles of operation of the cerebral oximeter system are based on the assumption that hemoglobin exists in two principal forms in the blood: oxygenated hemoglobin (HbO>) and reduced hemoglobin (Hb). Functional oxygen saturation (SO2) is defined as the ratio of oxyhemoglobin (HbO2) to total hemoglobin (HbO2 + Hb) and is commonly presented as a percentage.

SO2 = (HbO2 / (HbO2 + Hb)) * 100%

Since oxygenated and reduced hemoglobin are different colors and absorb light as a known function of wavelength, selected wavelengths of light can be used to assess the relative percentage of these two constituents. This fundamental approach of assessing the color of blood using various wavelengths of light to measure hemoglobin oxygen saturation trends is used in all currently marketed oximetry systems.

A disposable sensor of medical grade materials is applied to the patient's forehead (Figure 1). The sensor incorporates a light source and two return signal detectors at different pre-determined distances from the light source. The signal detector nearest the light source (3 cm) is considered the "shallow detector" and the further detector from the light source (4 cm) the "deep detector."

While the light reaching the deep detector has sampled about the same amount of skin, scalp, and skull as the light reaching the shallow detector, it has sampled more brain tissue. This difference is used to help separate out the brain signal and suppress anatomical differences in patients. The additional information unique to the deep signal return is predominately from brain tissue blood which is composed mostly of venous blood. The information contained in the shallow and deep signal returns is processed by an algorithm to measure changes in hemoglobin oxygen saturation in a small region of tissue beneath the sensor, predominately in the brain.

The SomaSensor is connected to a preamplifier (1.75 x 7.4 x 5.4 in.) which is placed close to the patient and amplifies the rSO2 signal. The signal is then carried to a display unit (6.5 x 12.5 x 13.5 in.) where the values and trends are displayed on the screen. The display unit controls all functions of the system with selections made by keys with on-screen labels. The system will operate for up to 20 minutes on battery, enabling patient transport without loss of data.

AI/ML Overview

Here's a breakdown of the acceptance criteria and the study that proves the device meets them, based on the provided text:

Acceptance Criteria and Reported Device Performance

Acceptance Criteria	Reported Device Performance (INVOS 3100A with SS-A SomaSensor)	Predicate Device Performance (INVOS 3100A with 3100-SD SomaSensor)
Trend Accuracy (combined bias and standard deviation)	Within ±3% (including co-oximeter and blood sampling errors)	±4.8%
Trend Correlation Coefficient (r²)	0.96	0.87
Transition Error (during increased etCO2 at constant SaO2, reflecting changes in cerebral blood flow)	Within 4% (supporting predominant brain measurement)	Within 5.4%
Overall Mean Bias (fSO2 vs. rSO2 index)	2.49 (for 19 individuals, one rejected due to low Signal Quality Index)	Not explicitly stated/compared
Mean Standard Deviation (rSO2 index)	2.1% (for all 42 individuals)	Not explicitly stated/compared
Repeatability	Tested and deemed substantially equivalent	Not Applicable (predicate)
High potential and current leakage	Tested and deemed substantially equivalent	Not Applicable (predicate)
Sensor temperature rise	Tested and deemed substantially equivalent	Not Applicable (predicate)
Sensor light output	SS-A source approximately ten times brighter than 3100-SD	Not Applicable (predicate)
System component interchangeability and safety/performance	Tested and deemed substantially equivalent	Not Applicable (predicate)

Study Details

Sample Size and Data Provenance:
- Test Set: 20 volunteers (19 light and 1 dark-skinned; 12 males, 8 females; ages 20-36, median 26.5 years).
- Data Provenance: The study was a "volunteer hypoxia study," implying a prospective study conducted with human volunteers. The text does not specify the country of origin of the data, but given the submission to the US FDA, it likely took place in the US or a region with comparable medical standards.
Number of Experts and Qualifications for Ground Truth for Test Set:
- The document implies clinical experts (medical professionals) were involved in placing catheters and analyzing blood samples for co-oximetry. However, the exact number of experts and their specific qualifications (e.g., "radiologist with 10 years of experience") are not explicitly stated. The ground truth relies on objective blood gas analysis.
Adjudication Method for the Test Set:
- Not Applicable in the traditional sense of human consensus on subjective assessments. The ground truth (fSO2) was derived from objective measurements (arterial and jugular venous blood sample oxygen saturations analyzed on a co-oximeter) and a calculated formula. One data point was rejected due to sampling errors, and one subject's absolute data was rejected due to a low Signal Quality Index but their trend data was still used. This suggests objective exclusion criteria rather than human adjudication of ambiguous cases.
Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study:
- No, an MRMC comparative effectiveness study was not conducted for this device. The study compared the device's performance against a physiological ground truth (blood oxygen saturation) rather than comparing human reader performance with and without AI assistance.
Standalone Performance:
- Yes, the clinical study evaluated the standalone performance of the INVOS 3100A Cerebral Oximeter. The device's rSO2 readings were compared directly to the calculated fSO2 from blood samples, without human intervention in interpreting the INVOS readings for the performance metrics.
Type of Ground Truth Used:
- The ground truth used was a calculated estimate of regional oxygen saturation (fSO2) derived from:
  - Objective physiological measurements: arterial blood oxygen saturation (SaO2) and jugular venous blood oxygen saturation (SjvO2) obtained via catheters.
  - Co-oximetry: analysis of blood samples on a co-oximeter.
  - A formula: fSO2 = (0.25 * SaO2) + (0.75 * SjvO2).
Sample Size for the Training Set:
- The document does not explicitly mention a separate training set for the device's algorithm. The provided information focuses on the "volunteer hypoxia study" used for clinical testing and demonstrating substantial equivalence. It's possible the algorithm was developed (i.e. 'trained') using earlier, internal data that is not detailed in this 510(k) summary, or the algorithm is based on established physical principles rather than a data-driven machine learning model requiring a distinct training set as typically understood today. The device described operates on principles of light absorption by hemoglobin, a well-understood physical phenomenon.
How Ground Truth for Training Set Was Established:
- As a training set is not explicitly mentioned, the method for establishing its ground truth is also not described. If this device relies on a fixed algorithm based on established physiological optics, a "training set" in the machine learning sense might not be applicable or relevant to its regulatory submission.

Summary

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Y-111022

SOMANETICS INVOS 3100A CEREBRAL OXIMETER 510(K) PREMARKET NOTIFICATION

Section 8	510(k) Summary
1.	Date Prepared:	April 30, 1997	OCT 10 1997
2.	Submitter/Contact Person:	Ronald A. WidmanDirector of Medical AffairsSomanetics Corporation1653 East Maple RoadTroy, MI 48083Phone: (810) 689-3050Fax: (810) 689-4272
3.	Trade Name:	Somanetics INVOS® 3100A Cerebral Oximeter (INVOS)with SS-A SomaSensor®Accessories:SS-A Single-patient use sensor (SomaSensor)3100-DD Disk Drive3100-TC Travel Case3100A-M Additional User Manual311963 Null Modem Cable
4.	Classification Name:	Oximeters
5.	Common Name:	Cerebral Oximeter
6.	Predicate Device:	Somanetics INVOS® 3100A Cerebral Oximeter with 3100-SD SomaSensor® (K960614)

Indications for Use: The noninvasive INVOS 3100A Cerebral Oximeter should be used in adults as an adjunct monitor of trends in regional hemoglobin oxygen saturation of blood in the brain of an individual. Because INVOS values are relative within an individual, the INVOS should not be used as the sole basis for decisions as to diagnosis or therapy. The value of data from the INVOS has not been demonstrated in disease states.

Contraindications: None.

8. Device Description:

$$SO_2 = \frac{HbO_2}{HbO_2 + Hb} \times 100%$$

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Image /page/1/Figure/2 description: The image is a cross-section of a sensor on a forehead. The sensor has a light source, a shallow detector, and a deep detector. The forehead is made up of skin, tissue, and bone. The image is labeled as "Figure 1: Cross Section of Sensor on Forehead".

9. Substantial Equivalence:

The INVOS SS-A SomaSensor is substantially equivalent to the INVOS 3100-SD SomaSensor in that the method of measurement, physical configuration and indications for use are identical. The newer SS-A has an LED light source like the 3100-SD, however, the SS-A source is approximately ten times brighter. As a result of both bench testing and a clinical study, the SS-A SomaSensor was shown to be substantially equivalent to the 3100-SD.

10. Nonclinical Testing:

The SS-A SomaSensor and INVOS system has been tested in the following areas to ensure substantial equivalence with the predicate device:

INVOS system repeatability, high potential and current leakage, sensor temperature rise, sensor light output, system component interchangeability and safety/performance.

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The INVOS system has been granted the GS and CE marks as certification of compliance with EN 60601-1/08.90 and EC Directive 93/42/EEC Annex III, Medical Devices. The INVOS system has been granted the ETL mark as certification of compliance with UL 2601.1 and CSA C22.2 No. 601.1 safety standards.

Clinical Testing: 11.

A volunteer hypoxia study was performed with the SS-A SomaSensor in support of this premarket notification as described below.

The volunteer hypoxia study objective was to compare the INVOS rSO2 index with blood oxygen saturation measurements performed off-line on a co-oximeter during moderate hypoxia and hypercapnia. The study consisted of 20 volunteers with demographics as follows: 19 light and 1 dark skinned subjects; 12 males and 8 females. Age ranged from 20 to 36 years, with a median of 26.5 years. Five sets of data were collected comparing rSO2 to a combination of arterial and jugular venous blood oxygen saturations over an arterial saturation range of 74-100% with etCO, controlled to each individual's resting level. The same five steps were then repeated at an elevated level of etCO, to raise cerebral blood flow (CBF) by increasing inspired CO2 by 4 to 7 mmHg such that CBF increased about 12-21% above normal.

Arterial catheters were placed in the left arm in 18 subjects and in the right arm in two. Jugular venous catheters were placed in the right internal jugular vein (IJ) without incident in all subjects. One data point was rejected due to sampling errors (jugular venous sample was delayed into the next step due to catheter problems). Values of rSO2 were compared to an estimate of the saturation of all the blood in the region of brain beneath the sensor, calculated as:

$$\text{fSO}_2 = \text{(0.25 }\text{* }\text{SaO}_2\text{)} + \text{(0.75 }\text{* }\text{SjvO}_2\text{)}$$

where SaO, and SjvO, are arterial and jugular bulb venous blood sample oxygen saturations as analyzed on a co-oximeter.

Trend agreement between tSO2 (as calculated from arterial and jugular venous blood samples) and rSO2 index at both levels of CBF was very high in the 20 individuals, mean individual $r^2$=0.95 (range 0.82 to 0.99). The ability of the INVOS to accurately measure trends in saturation was within ±3%, combined bias and standard deviation, including co-oximeter and blood sampling errors. The trend measurement correlation coefficient was $r^2$=0.96 and trend bias and standard deviation were 0.3 ± 2.9%. The overall mean bias between fSO2 and rSO2 index for 19 individuals (one subject's absolute data was rejected due to low Signal Quality Index) was 2.49. The mean standard deviation of the rSO2 index for all 42 individuals was 2.1%.

12. Conclusions Drawn from the Nonclinical Testing and Clinical Study:

The nonclinical testing of the INVOS 3100A with the modified SS-A SomaSensor support the conclusion that the modified system is safe and effective for patient use and substantially equivalent to the predicate device. Additionally, the testing supports the contention that the INVOS is able to perform with similar levels of accuracy and performance as the predicate device.

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In the hypoxia study during levels of moderate hypoxia during normo- and hypercapnia, the transition accuracy of the INVOS as compared to the fSO2 estimate from blood samples was within ±3% (combined bias and standard deviation), correlation coefficient $r^2$ = 0.96 (predicate device transition accuracy is ±4.8%, $r^2$ = 0.87). Rejection of non-brain signal was evaluated during changes in etCO2 (which produced changes in cerebral blood flow) at constant SaO2 (to hold oxygen saturation in the scalp constant). Transition error was calculated during increased etCO2 of 4-7 mmHg during constant SaOn (increased cerebral blood flow) and compared to transition error during changes in $SaO_2$ of up to 25% during constant $CO_2$ (systemic hypoxia). Both were within 4%, supporting a predominant brain measurement (predicate device was within 5.4%).

No complications or side effects directly attributable to the Oximeter were reported during the study. No adverse reactions to the sensor adhesive were reported. The SQI (Signal Quality Index), which evaluates whether conditions are optimum for accurate absolute measurements, indicated the data from one subject was not suitable for absolute comparisons of $rSO_2$ and $fSO_2$. In this subject, however, the trend data was good and was included in the trend accuracy statistics.

Since there were improvements in virtually all of the accuracy and safety areas, the combined non-clinical and clinical testing support the conclusion that the INVOS is safe, can accurately measure trends in regional hemoglobin oxygen saturation of blood in the brain of an individual and is substantially equivalent to the predicate device.

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Image /page/4/Picture/2 description: The image shows the logo for the U.S. Department of Health & Human Services. The logo consists of a stylized eagle with three stripes representing the human services aspect. The text "DEPARTMENT OF HEALTH & HUMAN SERVICES - USA" is arranged in a circular fashion around the eagle symbol.

Food and Drug Administration 9200 Corporate Boulevard Rockville MD 20856

Mr. Ronald A. Widman Director of Medical Affairs Somanetics Corporation 1653 East Maple Road Troy, Michigan 48083

OCT 1 0 1997

Re: K971628 Somanetics INVOS® 3100A Cerebral Oximeter for use Trade Name: with modified SS-A SomaSensor Requlatory Class: II Product Code: 74DQA Dated: April 30, 1997 Received: May 2, 1997

Dear Mr. Widman:

We have reviewed your Section 510(k) notification of intent to market the device referenced above and we have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to devices marketed in interstate commerce prıor 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, Druq, and Cosmetic Act (Act). 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.

If your device is classified (see above) into either class II (Special Controls) or class III (Premarket Approval), it may be subject to such additional controls. Existing major requlations affecting your device can be found in the Code of Federal Regulations, Title 21, Parts 800 to 895. A substantially equivalent determination assumes compliance with the Good Manufacturing Practice for Medical Devices: General (GMP) requlation (21 CFR Part 820) and that, through periodic GMP inspections, the Food and Drug Administration (FDA) will verify such assumptions. Failure to comply with the GMP regulation may result in regulatory action. In addition, FDA may publish further announcements concerning your device in the Federal Register. Please note: this response to your premarket notification submission does not affect any obligation you might have under sections 531 through 542 of the Act for devices under the Electronic Product Radiation Control provisions, or other Federal laws or requlations.

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This letter will allow you to begin marketing your device as described in your 510(k) premarket notification. The FDA finding of substantial equivalence of your device to a legally marketed predicate device results in a classification for your device and thus, permits your device to proceed to the market.

If you desire specific advice for your device on our labeling regulation (21 CFR Part 801 and additionally 809.10 for in vitro diganostic devices), please contact the Office of Compliance at (301) 594-4648. Additionally, for questions on the promotion and advertising of your device, please contact the Office of Compliance at (301) 594-4639. Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21 CFR 807.97). Other general information on your responsibilities under the Act may be obtained from the Division of Small Manufacturers Assistance at its toll-free number (800) 638-2041 or (301) 443-6597 or at its internet address "http://www.fda.gov/cdrh/dsmamain.html".

Sincerely yours,

Thomas J. Callahan

Thomas J. CallaWan, Ph.D Director Division of Cardiovascular, Respiratory, and Neurological Devices Office of Device Evaluation Center for Devices and Radiological Health

Enclosure

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1 of 1 Page

K971628 510(k) Number (if known):

Somanetics INVOS® 3100A Cerebral Oximeter and SS-A SomaSensor Device Name:

Indications For Use:

" The noninvasive INVOS 3100A Cerebral Oximeter is intended for use in adults as an adjunct monitor of trends in regional hemoglobin oxygen saturation of blood in the brain of an individual. Because INVOS values are relative within an individual, the INVOS should not be used as the sole basis for decisions as to diagnosis or therapy. The value of data from the INVOS has not been demonstrated in disease states.

(PLEASE DO NOT WRITE BELOW THIS LINE-CONTINUE ON ANOTHER PAGE IF NEEDED)

Concurrence of CDRH, Office of Device Evaluation (ODE)

Prescription Use (Per 21 CFR 801.109)

Over-The-Counter Use__________________________________________________________________________________________________________________________________________________________

(Optional Format 1-2-96)

Regulation Number and Section

§ 870.2700 Oximeter.

(a)
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.(b)
Classification. Class II (performance standards).