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OxiplexTS™ is a revolutionary new device allowing the measurement of oxygenated and de-oxygenated hemoglobin concentrations in tissue. The device works by emitting Near Infrared (NIR) light into tissue at known distances from a collector. Light of two different wavelengths is used and the light is modulated at an RF frequency of 110 MHz. The collected light is measured and processed, and the absorption and scattering coefficients of the medium are determined. Once the absorption and scattering are determined, the assumption that hemoglobin is the only significant absorber is applied and the oxygenated and de-oxygenated hemoglobin concentrations are calculated.

The unique feature of the ISS OxiplexTS is that it uses the theory of photon migration through highly scattering media. This patented technology allows for the first time the absolute measurement of absorption and scattering in a highly scattering medium such as human tissue.

Since OxiplexTS measures the absorption and scattering of tissues directly, it does not require any calibration, estimation, or assumption about scattering in order to make an accurate measurement of absorption and, hence, hemoglobin concentrations. This unique ability to separate scattering from absorption sets the ISS OxiplexTS above all other NIR tissue oximeter technologies.

Notice: Investigational device. Limited by Federal (or United States) law to investigational use. The ISS OxiplexTS is presently used for research only.

How OxiplexTS Works

Oxygen concentration in the blood stream can be conveniently determined in-situ by measuring the absorption coefficients of oxy- and deoxy-hemoglobin. A patented technology allows for the first time to measure the absolute scattering and absorption coefficients, and therefore, provide a system that does not require any calibration for the determination of the oxygen concentration.

The oximeter measures the absolute absorption and scattering coefficients of biological tissue. The absorption coefficient is given by the following relation:

[1]

where and are respectively the extinction coefficients at wavelength (λ) for oxy- and deoxy- hemoglobin. Once μa and μs' are determined at the two separate wavelengths, λ1 and λ2, the concentrations of the two species can be determined. The solution of the linear system [1] for two wavelengths gives:

[2]

From the concentration of the oxy and deoxy species, the hemoglobin saturation Y and the total hemoglobin content THC can be obtained, respectively:

[3]


Opportunities Provided by the OxiplexTS™

OxiplexTS provides exciting opportunities for research in tissue oxygenation. The ISS oximeter will also provide unique opportunities for research in tissue scattering. Never before have researchers been able to make simple, accurate, non-invasive real time measurements of scattering in tissue. This field of research is thus wide open for exploration.


Potential areas of Research

• Effects of exercise on muscle for the diagnosis of Peripheral Vascular Disease (PVD)
• Scanning of the muscle for the location of vascular occlusions
• Effects of pharmaceuticals and/or anesthetic gas mixtures on tissue and/or brain
• Monitoring of brain oxygenation during surgery
• Monitoring of neonatal infant brain oxygenation
• Monitoring oxygenation and hemoglobin concentration status of cancer tumors

Applications of OxiplexTS™

Several areas may benefit from the monitoring of the absolute values of tissue oxygenation, especially when pulse oximetry is not applicable because of the irregularity, or the lack of, the heartbeat, and in all the cases where the tissue oxygenation, and not the arterial oxygen saturation, is the parameter of interest. Therefore, the applications of the OxiplexTS include but are not limited to:

Premature Infant Intensive Care
Sleep Apnea
Sports Medicine & Kinesiology
Peripheral Vascular Disease
Monitoring Brain Oxygenation in OR/ER/ICU
• Attention Deficit Hyperactivity Disorder (ADHD)
• Anesthesiology
• Cardiothoracic & Vascular Surgery
• Neurosurgery
• Tumor Oxygenation
• Women's Health
• Obstetrics
• High Altitude Physiology
• Tissue Oxygenation in Hyperbaric Chambers
• Ergonomics

Measurements Acquired Using OxiplexTS

The plots below show measurements on human calf muscle during exercise. Changes in hemoglobin oxygenation and concentration can be correlated with various clinical conditions. For example, an increase in oxygenated hemoglobin concentration during exercise accompanied by no change or an increase in de-oxygenated hemoglobin concentration may indicate a venous occlusion which restricts the flow of de-oxygenated hemoglobin out of tissue. Similarly, arterial occlusions may be identified by significant decreases in oxygenated hemoglobin concentrations. The magnitude of hemoglobin changes as well as the rate of change may correlate with the type and extent of vascular disease. A wide variety of tissue oxygenation research is possible.

Figure (a) shows the ratio of Oxygenated to Total Hemoglobin Concentration as a percent. Also shown are some of the measurement parameters that can be correlated with physiological conditions including baseline (pre-exercise) value, change as a result of exercise, rates of change at the beginning and end of exercise, and final value after recovery from exercise.

Figure (b) shows Total Hemoglobin Concentration (in micromoles per liter).

Figure (c) shows Deoxygenated Hemoglobin Concentration.

Figure (d) shows Oxygenated Hemoglobin Concentration.