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 (HbO2) 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. 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. The sensor incorporates a light source and two return signal detectors at different predetermined 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. This difference is used to help separate out the brain signal and suppress tissue 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 which is placed close to the patient and amplifies the rSO2 signal. The signal is then carried to a display unit 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 onscreen labels. The system will operate for up to 20 minutes on battery, enabling patient transport without loss of data.

AI/ML Overview

The INVOS 3100A Cerebral Oximeter is designed to monitor trends in regional hemoglobin oxygen saturation in the brain. The device's acceptance criteria and the studies proving its performance are detailed below. It's important to note that this device is intended as an adjunct monitor and not for sole diagnostic or therapeutic decisions.

1. Table of Acceptance Criteria and Reported Device Performance

Acceptance Criteria Category	Specific Metric	Acceptance Criteria	Reported Device Performance
Trend Agreement (Hypoxia Study)	Mean individual r^2 (correlation between fSO2 and rSO2)	A high correlation value	0.947 (range 0.805 to 0.991)
Trend Accuracy (Hypoxia Study)	Ability to accurately measure trends (combined bias and standard deviation)	Within ±X% (implied to be clinically acceptable, often ±5%)	Within ±4.9%
Trend Measurement Correlation Coefficient (Hypoxia Study)	r (between fSO2 and rSO2)	A high correlation value	0.935
Bias (Hypoxia Study)	Overall mean bias between fSO2 and rSO2 index	Low bias (e.g., close to 0)	1.33
Standard Deviation of Absolute Difference (Hypoxia Study)	Between fSO2 and rSO2 index for individuals	Low standard deviation	Averaged 3.08
Transition Accuracy (Hypoxia Study - Systemic Hypoxia)	During changes in SaO2 (up to 27%) with constant CO2	Within X% (implied clinically acceptable, e.g., ±5.5%)	Within 5.5%
Transition Accuracy (Hypoxia Study - Cerebral Blood Flow Changes)	During changes in CO2 (4-10 mmHg) with constant SaO2	Within X% (implied clinically acceptable, e.g., ±5.5%)	Within 5.5%
Correlation with MCAVm (CEA Study)	Correlation between changes in rSO2 index and MCAVm during cross-clamp	A strong correlation value	0.806
Detection of Ischemia (CEA Study)	INVOS detection of oxygenation changes preceding EEG changes	Statistically significant precedence	p < 0.03
Device Operational Time (CEA Study)	Percentage of time INVOS was able to calculate rSO2 index	High percentage (e.g. >95%)	99.66%
Patient Safety (Both Studies)	Absence of adverse reactions or skin irritation	No instances observed	No instances of irritation or adverse reactions observed

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

Hypoxia Study: 30 volunteers.
- Data Provenance: Not explicitly stated, but implies a prospective study conducted in a controlled lab setting where hypoxia and hypercapnia were induced. The demographics (skin tone, age, gender) are provided, but country of origin is not specified.
Carotid Endarterectomy (CEA) Study: 27 patients (one operated twice for both left and right CEAs, and one additional subject for operational reliability data).
- Data Provenance: Not explicitly stated, but implies a prospective study conducted during surgical procedures. All patients were Caucasian. Country of origin is not specified.

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

Hypoxia Study: The "ground truth" (fSO2) was calculated from arterial and jugular venous blood oxygen saturations, measured off-line on a cooximeter. While a cooximeter is a device, its results are typically interpreted and validated by trained personnel. No specific "experts" are mentioned for establishing ground truth from this data itself, beyond the standard medical laboratory practices for cooximetry.
CEA Study:
- EEG Changes: "evaluated by a trained observer using 10-channel analog recordings." The specific qualifications of this "trained observer" are not provided (e.g., neurophysiologist, technician, years of experience).
- MCAVm: Measured by transcranial Doppler (TCD), which is a device-based measurement, implying a trained technician/physician to operate and interpret.
- The "gold standard" for cerebral ischemia in this context is implicitly a combination of TCD and EEG changes.

4. Adjudication Method for the Test Set

The document does not describe a formal adjudication method (like 2+1 or 3+1 consensus) for the ground truth in either study. Ground truth appears to be based on direct physiological measurements (blood samples, TCD, EEG) interpreted by standard clinical practice or single trained observers (for EEG).

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

No MRMC comparative effectiveness study was done. The focus was on comparing the device's output to established physiological measurements and other monitoring devices (cooximeter, TCD, EEG), not on how human readers' performance improved with AI assistance.

6. Standalone Performance (Algorithm Only Without Human-in-the-Loop Performance)

Yes, the performance metrics (trend agreement, accuracy, correlation, bias, operational time) are all measurements of the device's standalone performance. The INVOS 3100A Cerebral Oximeter operates autonomously to provide rSO2 index values. The studies evaluate how well these autonomously generated values correlate with or detect physiological changes measured by other means.

7. Type of Ground Truth Used

Hypoxia Study:
- Physiological measurements: Functional oxygen saturation (fSO2) derived from arterial and jugular venous blood samples, measured off-line on a cooximeter. This is a direct physiological measurement.
CEA Study:
- Physiological measurements/clinical indicators: Changes in mean middle cerebral artery flow velocity (MCAVm) as measured by transcranial Doppler (TCD) and EEG changes evaluated by a trained observer. These serve as indicators of cerebral function and ischemia.

8. Sample Size for the Training Set

The document does not explicitly mention a "training set" in the context of machine learning or AI models. The INVOS 3100A Cerebral Oximeter operates based on spectrophotometric principles and an algorithm to process signals from its sensors. The development of this algorithm itself would have involved internal validation and calibration, but details on a separate, dedicated "training set" in the modern sense of AI algorithm development are not provided. The non-clinical testing described likely encompasses internal verification and validation of the device's fundamental function and algorithms.

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

As a "training set" is not explicitly mentioned, the method for establishing its ground truth is also not detailed. The device's underlying principles (spectrophotometry) are well-established. The algorithm's development would have relied on biophysical models and experimental data to accurately translate light absorption into regional oxygen saturation, consistent with established physiological knowledge.

Summary

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Section 8	K960614	JUN - 5 1996	510(k) Summary
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Date Prepared:	May 31, 1996
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1.	Date Prepared:	May 31, 1996
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)Accessories:3100-SD Single-patient use sensor (SomaSensor)3100-DD Disk Drive3100-TC Travel Case3100A-M Additional User Manual
4.	Classification Name:	Oximeters
5.	Common Name:	Cerebral Oximeter
6.	Predicate Devices:	Nellcor N-200 Pulse Oximeter (K863784)Baxter SAT-II Intravascular Oximetry System(K884329)

Indications for Use: The noninvasive INVOS 3100A Cerebral Oximeter should 7. 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:

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$$SO_1 = \frac{HbO_2}{HbO_2 + Hb} \times 100%$$

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.

Image /page/1/Figure/3 description: This 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 light source emits light that travels through the skin, tissue, bone, and brain. The shallow detector detects light that has traveled through the skin and tissue, while the deep detector detects light that has traveled through the skin, tissue, bone, and brain.

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 predetermined 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 This difference is used to help separate out the brain signal and suppress tissue. 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 onscreen labels. The system will operate for up to 20 minutes on battery, enabling patient transport without loss of data.

ರಿ. Substantial Equivalence:

The INVOS is substantially equivalent to the common pulse oximeter and to intravascular oximetry systems. It has the same intended use as generic oximeters (e.g. pulse oximeters, ear oximeters, and intravascular catheter oximeters), namely to measure blood oxygen saturation. All such devices utilize spectrophotometric techniques to assess the color of blood in order to determine the hemoglobin oxygen saturation.

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The INVOS is similar to the common pulse oximeter in its patient interface and method of operation. Both devices are applied to the surface of the skin. pass light through highly vascularized tissue, capture returned light, and analyze it to provide an estimate of functional hemoglobin oxygen saturation in the in vivo blood by analyzing the color of that blood. Both employ a two-wavelength near-infrared spectrophotometric technique using LED light sources and photodiode detectors. Pulse oximeters make their measurements on a finger, toe, or earlobe. The INVOS makes its measurement on the forehead.

Whereas pulse oximeters emphasize arterial hemoglobin oxygen saturation and the INVOS measures predominately venous hemoglobin oxygen saturation, the clinical interpretation of the INVOS measurement is similar to that of currently marketed intravascular catheter oximeter systems that measure mixed venous oxygen saturation. Specifically, intravascular catheter oximeter systems continuously measure trends in blood oxygen saturation in the pulmonary artery which is comprised of mixed venous blood. The INVOS measures trends in oxygen saturation in the region of the brain beneath the sensor which contains blood that is a majority venous blood. As with intravascular catheter oximeter systems, changes in INVOS values reflect changes in the balance between oxygen delivery and oxygen consumption and alert the clinician of the potential for a problem that is worthy of investigation.

Unlike pulse oximeters, the INVOS does not depend on a pulse signal to function. During periods when pulse signals are low or non-existent (e.g. cardiopulmonary bypass, hypothermia, hypotension, cardiac arrhythmias, etc.) the INVOS is able to continue to function, providing potentially important noninvasive information regarding oxygenation.

Unlike intravascular catheter oximetry systems, the INVOS is noninvasive and the INVOS makes venous oxygen saturation information available with less risk, enabling its use on patients for whom the use of a pulmonary artery catheter is not warranted.

10. ~ Nonclinical Testing:

The INVOS has been tested in the following areas to ensure substantial equivalence with the predicate devices:

INVOS linearity, accuracy, noise levels, operating and storage temperatures, input voltage, altitude, patient safety, user safety, EMI/RFI interference and susceptibility, battery discharge time, power consumption, component stress, component heating, fan cooling capacity, shipping carton validation and compliance with voluntary standards CSA C22.2 No. 601.1, UL 2601.1, EC Directive 93/42/EEC Annex III, Medical Devices and EN 60601-1/08.90.

The SomaSensor has been tested in the following areas to ensure substantial equivalence with the predicate devices:

Linearity, repeatability, operating and storage temperatures, potential overheating, light output, patient and user safety, biocompatability, EMI/RFI interference and

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susceptibility and compliance with voluntary standards CSA C22.2 No. 601.1, UL 2601.1, EC Directive 93/42/EEC Annex III, Medical Devices and EN 60601-1/08.90.

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.

Two clinical studies were performed in support of the premarket notification as described below.

The first was a volunteer hypoxia study whose objective was to compare the INVOS rSO2 index with blood oxygen saturation measurements performed off-line on a cooximeter during moderate hypoxia and hypercapnia. The study consisted of 30 volunteers with demographics as follows: 21 light, 5 medium and 4 dark skinned subjects; 19 males and 11 females. Age ranged from 19 to 40 years, with a median of 25 years. Six sets of data were collected comparing rSO2 to a combination of arterial and jugular venous blood oxygen saturations over an arterial saturation range of 73-100%. The six steps were then repeated at an elevated level of cerebral blood flow (CBF) obtained by increasing inspired CO2 such that CBF increased about 12-30%.

Trend agreement between fSO2 (as calculated from arterial and jugular venous blood samples) and rSO2 index at both levels of CBF was very high in individuals, mean individual r2=0.947 (range 0.805 to 0.991). The ability of the INVOS to accurately measure trends in saturation was within ±4.9% (combined bias and standard deviation). The trend measurement correlation coefficient was r=0.935 and bias and standard deviation were 0.219 ± 4.61. The overall mean bias between fSO2 and rSO2 index was 1.33. Standard deviations of the absolute difference between fSO2 and rSO2 index for individuals averaged 3.08. Skin condition was observed before and after placement of the SomaSensor. No instances of irritation were observed.

The second study evaluated 27 patients during carotid endarterectomy (CEA) with demographics as follows: 21 males and 6 females, all Caucasian. Its purpose was to evaluate the ability of the INVOS system to detect and differentiate mild to severe ischemia caused by clamping of the common carotid artery. Twenty-two of this group had surgery performed under general anesthesia and five under regional anesthesia. One patient was operated twice for both left and right CEAs. Changes in rSO2 index were compared to changes in mean middle cerebral artery flow velocity (MCAVm) as measured by transcranial Doppler (TCD) and EEG changes as evaluated by a trained observer using 10-channel analog recordings.

Correlation between changes in rSO2 index and changes in MCAVm during cross-clamp of the common carotid artery was r=0.806. The INVOS detected changes in oxygenation

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which preceded EEG changes during cross-clamp of the carotid artery, p<0.03. Comparison of the changes in MCAVm and rSO2 index were made during cross-clamp of only the external carotid artery in six of the 27 subjects. The percentage change in both rSO2 index and MCAVm when clamping the external carotid was generally lower than when clamping the common carotid, although, due to the small sample, statistical significance could not be reached.

Skin condition was observed in the twenty-seven study subjects (one twice) and one (008) who had a sensor placed but on whom TCD monitoring could not be accomplished. Condition was evaluated immediately after removal of the sensor in all twenty-eight and included a 24-hour follow-up in eleven. No instances of adverse reactions or skin irritation were observed.

Using continuous data recorded during the CEA study on disk, the amount of time was calculated when, due to noise, electrical interference, excessive ambient light or other events, the INVOS was not able to calculate a value for rSO2 index. Combining all patients enrolled in the study and 1 additional subject (008) who was not enrolled in the study due to lack of TCD monitoring, the INVOS was operational 99.66% of the time in the O.R. or less than 10 minutes of data were lost in over 48 hours of monitoring.

12. Conclusions Drawn from the Nonclinical and Clinical Studies:

The nonclinical testing of the INVOS and the SomaSensor support the conclusion that the INVOS system is safe for patient use, similar to the predicate devices. Additionally, the testing supports the contention that the INVOS is able to perform with similar levels of accuracy and performance as the predicates.

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 ±5% (combined bias and standard deviation), correlation coefficient r = 0.935. Cerebral trending accuracy was measured by calculating transition error during changes in CO2 of 4-10 mmHg during constant SaO2 (changes in cerebral blood flow) and transition error during changes in SaO2 of up to 27% during constant CO2 (systemic hypoxia). Both were within 5.5%, supporting a predominant brain measurement.

In the carotid endarterectomy study, changes in rSO2 index correlated well with MCA Vm changes and its performance supported its substantial equivalence with other measures of cerebral function monitoring. The ability of the INVOS to document periods of cerebral ischemia as confirmed by EEG changes was as good as TCD measurement of changes in MCAVm (p<0.01). Changes in rSO2 index during extracranial ischemia (caused by clamping just the external carotid artery) were small compared to intracranial ischemia. When sufficient collateral flow was present in the brain, changes in rSO2 index during clamping were minimal despite presumed extracranial desaturation (since established collaterals do not exist extracranially), providing evidence for an INVOS measurement predominately from the brain.

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No complications or side effects directly attributable to the Oximeter were reported during either study. No adverse reactions to the sensor adhesive were reported.

The INVOS system provided reliable monitoring 99.66% of the time in 28 cases during use in the operating room.

The combined nonclinical and clinical testing support the conclusion that the INVOS can measure trends in regional hemoglobin oxygen saturation of blood in the brain of an individual and is substantially equivalent to the predicate devices.

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).