Introduction The
InSpectraTM StO2 System non invasively provides continuous, real-time and direct perfusion status information using near infrared spectroscopy and a noninvasive, single-use sensor placed on the thenar eminence (thumb muscle). Shunting of blood to vital organs during hypovolemic shock is the basis of StO
2 monitoring. By measuring tissue oxygen saturation (StO
2) in peripheral thenar muscle, the
InSpectra StO2 System uses the body’s own response mechanism to provide valuable information on the adequacy of oxygen delivery to vital organs. Tissue oxygen saturation is being clinically studied as a potential measure of hemorrhagic and septic shock status.
InSpectraTM StO2 Tissue Oxygenation Monitor
The InSpectraTM StO2 Tissue Oxygenation Monitor measures hemoglobin oxygen saturation primarily in the microcirculation of tissue by illuminating the tissue with precisely controlled wavelengths of light. The cells, blood, and other tissue components absorb and scatter the light, and a portion of the light returns to the monitor. The monitor analyzes the returned light and displays the result as percent tissue oxygen saturation (StO2).
The InSpectra StO2 Monitor uses a spectrometer to derive the InSpectraTM StO2 System Measurement from the absorbance differences at four specific wavelengths in the near-infrared (NIR) spectrum. Because NIR wavelengths are long, they penetrate tissue easily, making it possible to obtain measurements of the microcirculation from deep in muscle. The second derivative algorithm1 employed by the InSpectra StO2 System measures the rate of change of absorption as a function of wavelength, instead of simply measuring light intensity at a wavelength, and thereby inherently rejects false or interfering factors.
The InSpectra StO2 System adequately suppresses unwanted effects such as differences in blood volume in the illuminated tissue, variations in the length of the light path, and moderate motions of the patient’s arm. Therefore, InSpectra StO2 System Measurements are not just relative, but an absolute measure and are accurate over the full range of readings from 0–100%.2 Because the InSpectra StO2 System readings are absolute, they are analytically useful in the treatment of trauma and critical care patients, whose pre-admission InSpectra StO2 System Measurements are not known.3
1. US Patent 5,879,294.
2. Myers DE, Anderson LD, Seifert RP, Ortner JP, Cooper CE, Beilman GJ Mowlem JD. Noninvasive method for measuring local hemoglobin oxygen saturation tissue using wide gap second derivative near-infrared spectroscopy. J BioMed Opt. 2005;10(3):034017.
3. Cohn et. al. Tissue oxygen saturation predicts the development of organ dysfunction during traumatic shock resuscitation. J Trauma. 2007:62 (1): 44–55.
