New System Provides Noninvasive Tissue Oxygenation Monitoring

An innovative spectroscopic system monitors tissue oxygenation, a new vital sign with broad applications for critical care medicine.

The InSpectra StO2 tissue oxygenation monitoring system provides continuous, real-time information for perfusion status monitoring, helping clinicians reduce risks and costs by enabling faster and more precise assessment of oxygen delivery to vital organs and tissue. The system provides continuous information using near-infrared spectroscopy and a noninvasive, single-use sensor placed on the thenar eminence (the thumb muscle). No calibration is required, and the system is operated by two buttons. The large numeric display is visible at a distance, and is accompanied by user-adjustable StO2 audible high- and low-level alarms. A tissue hemoglobin index (THI) indicates signal strength and helps sensor placement. The rugged monitor is accompanied by a steel reinforced optical cable, protecting the system from damage.

The monitor measures microcirculation hemoglobin oxygen saturation by illuminating the tissue with precisely controlled wavelengths of light in the near-infrared (NIR) spectrum. The cells, blood, and other tissue components absorb and scatter the light, and a portion of the light returns to the monitor, which then analyzes the returned light and displays the result as percentage of StO2. Because NIR wavelengths are long, they penetrate tissue easily, making it possible to obtain measurements of the microcirculation from deep inside the muscle. The second derivative algorithm employed by the system measures the rate of change of absorption as a function of wavelength, thereby inherently rejecting false or interfering factors. The InSpectra StO2 tissue oxygenation monitoring system is a product of Hutchinson Technology (Hutchinson, MN, USA).

Shunting of blood to vital organs during hypovolemic shock is the basis of StO2 monitoring; by measuring tissue oxygen saturation (StO2) in peripheral thenar muscle, the body's own response mechanism is used to provide valuable information on the adequacy of oxygen delivery to vital organs. Tissue oxygen saturation is also being clinically studied as a potential measure of hemorrhagic and septic shock status.

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