Why Peer-Reviewed Clinical Research Matters for Cerebral Oximetry Monitoring

Clinical studies support the assurance that healthcare decisions are made using accurate and reliable data. As healthcare providers, it’s fundamentally important to use sound science to promote positive patient outcomes. Using evidence-based research to inform your care delivery benefits your patients, your practice, and the medical community.

Reliance on clinical reference studies helps support you and the care you provide. Look at the INVOS™ cerebral oximetry system. It provides real-time monitoring of changes in regional oxygen saturation (rSO2) of blood in the brain or other tissues beneath the sensor. The INVOS™ system is considered the clinical reference standard. No other near infrared spectroscopy (NIRS) technology is backed by a comparable volume of published, peer-reviewed clinical research.1 Hundreds of studies have evaluated the unique characteristics of the INVOS™ system. These studies include diverse patient populations, settings, and various interventions.2 Because the INVOS™ system’s algorithm reacts differently to acute alterations in hemodynamics, oxygen saturation, and oxygen metabolism — this evidence may not apply to other regional oximeters.3, 4–7

Why does peer-reviewed clinical research matter?

The value of the clinical review is multifaceted. In addition to improving patient outcomes and practitioner care, clinical studies are important in identifying efficacy and safety of medical claims. Some companies will promote absolute accuracy as a product benefit; however, if you look at current peer-reviewed research on cerebral oximeter technology, absolute accuracy is unattainable because the technology doesn’t allow for those measurements.8 Instead, measuring absolute cerebral oxygenation levels is only feasible when sampling blood from a patient’s brain, which is not a function of a cerebral oximeter. The U.S. Food and Drug Administration (FDA) also doesn’t define parameters for the use of absolutes and other similar marketing terms.

Patient oxygenation fluctuations occur naturally within a normal venous range between 58 and 82 percent.8,9 Identifying a patient’s unique baseline with cerebral oximetry — prior to induction, oxygen delivery, or medication administration — is important to determine if intervention is necessary. Decreases in the INVOS™ system index value indicates desaturations that typically occur before changes in global measurement occur.10 This gives you a first alert to intervene early, before tissue ischemia occurs.10 Clinical evidence shows that the ability to quickly intervene and reverse desaturation has proven to positively impact patient outcomes.8,11-17

Clinical research also provides value in legitimizing medical claims by qualifying findings. With the INVOS™ cerebral oximeter, a unique clinical algorithm is used. This provides alerts to potential changes before other vital sign monitors even react.8, 11-16,18 Evidence-based research supports the qualification of this finding ― that the results from clinical research are not interchangeable from product-to-product.4 The American Society for Enhanced Recovery and Perioperative Quality Initiative Joint Consensus states that NIRS devices from different manufacturers have significantly different measurements and aren’t interchangeable.3

What is the value of having multiple clinical studies?

The medical community benefits holistically with the publication of various clinical studies. From introducing evolving healthcare products to maintaining professional autonomy as well as cementing a system of checks and balances — products with a myriad of studies are favorable.2

Multiple clinical studies help reinforce results from numerous researchers for more informed patient decisions. With INVOS™ cerebral oximetry, a number of use-case benefits have been identified in several studies including the following reductions:

  • Major organ morbidity and mortality (MOMM)8
  • Stroke rates and coma8,19
  • Postoperative cognitive decline8,19,20
  • Respiratory failure and time spent on the ventilator8,19
  • Patient length of stay in the ICU and overall hospital stay8,19,20

While clinical studies are meant to support patient care, products with few clinical studies focused on a specific patient subset may differ from actual patients served. That’s why multiple studies could provide a broad array of patient populations allowing for additional insights into potential baseline variants and fluctuations across a diverse patient base.

For example, studies of skin pigment have demonstrated lower than expected cerebral oximetry baselines.21-25 And while evidence reveals melanin doesn’t have much influence on what’s reported for near infrared data with cerebral oximetry, ethnicity may influence respective diseases processes.21-25 Research finds that low baselines may indicate inherent ischemia-related organ risk within each patient. That’s why understanding the unique physiology of each patient is critical to positive outcomes.21-25 Using the INVOS™ system in combination with preoperative screening supports a comprehensive understanding of distinct patient physiology and potentially improved outcomes.

Related: Read more on the growing body of evidence for INVOS™ cerebral/somatic oximeter.

Is there a downside to clinical research and reviews?

Clinical studies that are done quickly may lead to lapses in data. This further reiterates the importance of multiple peer-review studies to validate findings. With more than one million clinical trial papers published, sifting through clinical research to obtain valuable and relevant information is time consuming.26 This could lead to knowledge gaps, which can be compounded by evolving medicine, medical devices, science, and technology.

With the INVOS™ system, it’s imperative to understand the clinical evidence behind unique patient baselines and the importance of rapid intervention to address cerebral desaturation. Without clarity of the proven evidence that supports identifying an individual normal state, false readings may be assumed during procedures. The INVOS™ system has a clinical algorithm that responds to changes in each patient’s unique baseline, or their unique normal state. Capturing a patient’s baseline prior to performing surgery is critical to diminishing false reading interpretations. Once a patient’s individual baseline is identified, interpreting fluctuations in readings could help assess intervention needs. Clinical evidence also points out that rapid detection of hemodynamic changes, supports critical clinical decisions. 8,11-17

Related: Learn more about the use of INVOS™ cerebral oximetry system for cardiac surgical patients.

The INVOS™ monitoring system should not be used as the sole basis for diagnosis or therapy and is intended only as an adjunct in patient assessment. Reliance on the INVOS™ system alone for detecting cerebral desaturation events is not recommended.


1. Yu Y, Zhang K, Zhang L, et al. Cerebral near-infrared spectroscopy (NIRS) for perioperative monitoring of brain oxygenation in children and adults (review), Cochrane Library, Cochrane Database of Systematic Reviews - Intervention Version , 2018, Issue 1. Art. No.: CD010947, DOI: 10.1002/14651858.CD010947.pub2.

2. Medtronic Inc. Data on file.

3. Thiele RH, Shaw AD, Bartels K, et al. Perioperative Quality Initiative (POQI) 6 Workgroup. American society for enhanced recovery and perioperative quality initiative joint consensus statement on the role of neuromonitoring in perioperative outcomes: cerebral near-infrared spectroscopy. Anesth Analg. 2020 Nov;131(5):1444–1455.

4. Tomlin KL, Neitenbach AM, Borg U. Detection of critical cerebral desaturation thresholds by three regional oximeters during hypoxia: a pilot study in healthy volunteers. BMC Anesthesiol. 2017;17(1):6.

5. Schmidt C, Heringlake M, Kellner P, et al. The effects of systemic oxygenation on cerebral oxygen saturation and its relationship to mixed venous oxygen saturation: A prospective observational study comparison of the INVOS and ForeSight Elite cerebral oximeters. Can J Anaesth. 2018 Jul;65(7):766–775.

6. Chung J, Ji SH, Jang YE, et al. Evaluation of Different Near-Infrared Spectroscopy Devices for Assessing Tissue Oxygenation with a Vascular Occlusion Test in Healthy Volunteers [published online ahead of print, 2020 Sep 7]. J Vasc Res. 2020;1–7.

7. Fellahi JL, Butin G, Fischer MO, Zamparini G, Gérard JL, Hanouz JL. Dynamic evaluation of near-infrared peripheraloximetry in healthy volunteers: a comparison between INVOS and EQUANOX. J Crit Care. 2013;28(5):881.e1–881.e8816.

8. Murkin JM, Adams SJ, Novick RJ, et al. Monitoring brain oxygen saturation during coronary bypass surgery: a randomized, prospective study. Anesth Analg. 2007;104(1):51–58.

9. Edmonds HL Jr, Ganzel BL, Austin EH 3rd. Cerebral oximetry for cardiac and vascular surgery. Semin Cardiothorac Vasc Anesth. 2004;8(2):147–166.

10. Avery, Edwin G. IV, M.D., C.P.I., Cerebral oximetry is frequently a “first alert” indicator of adverse outcomes. Medtronic white paper, 2016.

11. Colak Z, Borojevic M, Bogovic A, et al. Influence of intraoperative cerebral oximetry monitoring on neurocognitive function after coronary artery bypass surgery: a randomized, prospective study. Eur J Cardio-Thorac Surg. 2014.

12. Deschamps A, Lambert J, Couture P, et al. Reversal of decreases in cerebral saturation in high-risk cardiac surgery. J. Cardiothorac Vasc Anesth. 2013;27(6):1260-1266. doi 10.1053/j.jvca.2013.01.019

13. Moerman A, Vandenplas G, Bové T, Wouters P F, De Hert, S. G. Relation between mixed venous oxygen saturation and cerebral oxygen saturation measured by absolute and relative near-infrared spectroscopy during off-pump coronary artery bypass grafting. Br. J. Anaesth. 2013;110(2):258–265.

14. Borg U, Ajizian S. Performance Differences Between Two Near Infrared Spectroscopy Monitors in a Porcine Hemorrhagic Shock Model. Poster presented at: 26th Annual Meeting of the European Society of Paediatric and Neonatal Intensive Care; June 2015; Vilnius, Lithuania.

15. Casati A., Fanelli G, Pietropaoli P, et al. Continuous monitoring of cerebral oxygen saturation in elderly patients undergoing major abdominal surgery minimizes brain exposure to potential hypoxia. Anesth. Analg. 2005;101(3):740–747.

16. Vretzakis G, Georgopoulou S, Stamoulis K, et al. Monitoring of brain oxygen saturation (INVOS) in a protocol to direct blood transfusions during cardiac surgery: a prospective randomized clinical trial. J Cardiothorac Surg. 2013;8:145.

17. Chieregato A, Calzolari F, Trasforini G, et al. Normal jugular bulb oxygen saturation. J Neurol Neurosurg Pshychiatry. 2003;74:784–786.

18. Based on internal study, A non-GLP comparison study of the INVOS NIRS system to competitive regional oxygen systems. 2015.

19. Goldman S, Sutter F, Ferdinand F, Trace C. Optimizing intraoperative cerebral oxygen delivery using noninvasive cerebral oximetry decreases the incidence of stroke for cardiac surgical patients. Heart Surg Forum. 2004;7(5):E376–381. 

20. Slater JP, Guarino T, Stack J, et al. Cerebral oxygen desaturation predicts cognitive decline and longer hospital stay after cardiac surgery. Ann Thorac Surg. 2009;87(1):36–44.

21. Hongo, K., Kobayashi, S., Okudera, H., Hokama, M., Nakagawa, F. Noninvasive cerebral optical spectroscopy: Depth-resolved measurements of cerebral haemodynamics using indocyanine green. 1995 April. 0161-6412 95 020089-05.

22. American Heart Association Website. https://www.heart.org/en/health-topics/high- blood-pressure/why-high-blood-pressure-is-a-silent-killer/know-your-risk-factors-for- high-blood-pressure. Reviewed: Nov. 30, 2017.

23. American Diabetes Association. https://www.diabetes.org/diabetes/genetics-diabetes.

24.  Spanakis, EK and Golden, SH. Race/Ethnic Difference in Diabetes and Diabetic Complications. Curr Diab Rep. 2014;13(6). doi: 10.1007/s11892-013-0421-9.

25. National Kidney Foundation. https://www.kidney.org/atoz/content/minorities-KD. Reviewed: Aug. 30, 2020.

26. Ioannidis JP. Why Most Clinical Research Is Not Useful. PLoS Med. 2016;13(6):e1002049. Published 2016 Jun 21. doi:10.1371/journal.pmed.1002049.

About the Author

Kevin joined Medtronic in 2019 as a clinical product specialist supporting our INVOS(TM) system on the Northeast Coast and continues to serve the area today as a NICU/OR CPS. Kevin has 12 years of clinical nursing experience.