Brochure

Background

Understanding changes in tissue perfusion can assist physicians in focusing and tailoring treatments when the perfusion to a specific tissue is at stake1. Non-invasive, easy to use and continuous measurement of blood flow to the tissue can be achieved with near-infrared light. Until now, there has not been a solution that enables a localized measurement continuously and non-invasively in an easy to use manner. UTLight™ technology, developed by Ornim, provides this solution.

How UTLight™
Works

Laser light is introduced into a tissue, much like other Near-Infrared Spectroscopy (NIRS) based devices that monitor cerebral oximetry. However, only Ornim’s monitors add rapid, brief, focused pulses of ultrasound into the tissue over the volume of interest through which light passes. Propagating through tissue slower than the light does, these ultrasound pulses create an effect, similar to the Doppler effect, on the light photons they encounter. As time progresses, the ultrasound pulse penetrates deeper into the tissue, and the phase of light emanating from this depth is shifted, or “tagged” accordingly, and can be identified later. Using this tagging mechanism, light collected by the monitor’s photoSensor can be filtered as a function of time, corresponding to relative depth, to analyze the photons emanating from a predetermined tissue volume, roughly 1cm3.

UTLight™
Flowmetry

Providing blood flow measurement using UTLight™ technology involves analyzing a Doppler shift in coherent light signals. Living tissue is never static; blood is moving all the time. The flow in the microvasculature results in a Doppler shift in the detected light signal. The higher the blood flow, the broader the Doppler shift of the scattered light. Ornim’s proprietary algorithm analyzes the Doppler shift of the tagged light signal to non-invasively determine a patient’s blood flow in the microcirculation underneath the Sensor.

This is Important Because:

  1. Physicians care about flow: Monitoring Cerebral Blood Flow (CBF) is important2 for managing patients suffering from head trauma, stroke or even under general anesthesia. In many such cases, changes in oximetry are used as a proxy to reflect changes in the underlying flow. Ornim’s UTLight™ technology provides this parameter directly.
  2. Flow is an actionable parameter: Physicians can manipulate blood flow by varying blood pressure, ventilation and feedback on these changes is imperative for management of blood pressure during cardio-pulmonary bypass and management of brain-injured patients. According to the guidelines of the Brain Trauma Foundation3 for management of Cerebral Perfusion Pressure (CPP), ancillary monitoring of CBF, oxygenation and metabolism can facilitate CPP management.
  3. Assessing Autoregulation function requires continuous monitoring of CBF: Impaired cerebral Autoregulation may predispose patients undergoing cardio-pulmonary bypass surgery to stroke injury4. Ornim’s technology provides continuous, real-time readings of changes in CBF, and combined with blood pressure or ICP readings can be used to assess Autoregulation function.
  4. Oximetry is not a direct surrogate for blood flow: Changes in oxygen saturation may not reflect changes in blood flow, and they may not be in the same direction5. An isolated vessel occlusion will lead to a decrease in both target tissue oximetry and blood flow. However, as a septic patient’s tissue oxygen demand grows, oximetry readings should decrease, whereas blood flow will likely increase, reflecting the patient’s hyperdynamic state. The point is that oxygenation and flow do not necessarily march in lockstep with one another, and it is not good practice to rely upon oximetry as a surrogate for blood flow status. By providing a real, direct indication of flow, UTLight™ makes guesswork unnecessary.
References:

  1. Fischer GW, Reich D, Plestis KA, Griepp RB, Results Utilizing Absolute Cerebral Oximetry Monitoring Suggest the Need for Tailored Patient Management during Cardiac Surgery, Presented at the Outcomes 2006: “The Key West Meeting” AND Casati A, Fanelli G, Pietropaoli P, Proietti R, Tufano R, Danelli G, Fierro G, De Cosmo G, Servillo , Continuous Monitoring of Cerebral Oxygen Saturation in Elderly Patients Undergoing Major Abdominal Surgery Minimizes Brain Exposure to Potential Hypoxia, Anesth Analg. 2005 Sep;101(3):740-7.
  2. Dagal A, Lam AM Cerebral Blood Flow and the Injured Brain: How Should We Monitor and Manipulate It? Curr Opin 2011 Apr;24(2):131-7.
  3. Bratton L., et al., Guidelines for the Management of Severe Traumatic Brain Injury. IX. Cerebral Perfusion Thresholds. J Neurotrauma 24 Suppl 1: p. S59-64, 2007.
  4. Ono M et Risks for Impaired Cerebral Autoregulation during Cardiopulmonary Bypass and Postoperative Stroke. Br J Anaesth. 2012 Sep;109(3):391-8.
  5. Schytz W. et al, a New Technology for Detecting Changes in Cerebral Blood Flow – a Comparative Study of Ultrasound Tagged Near Infrared Spectroscopy and 133Xe SPECT in Healthy Volunteers Neurocrit Care. 2012 Aug;17(1):139-45.