Pulse Oximetry with Two Infrared Wavelengths without Calibration in Extracted Arterial Blood

Abstract

Oxygen saturation in arterial blood (SaO2) provides information about the performance of the respiratory system. Non-invasive measurement of SaO2 by commercial pulse oximeters (SpO2) make use of photoplethysmographic pulses in the red and infrared regions and utilizes the different spectra of light absorption by oxygenated and de-oxygenated hemoglobin. Because light scattering and optical path-lengths differ between the two wavelengths, commercial pulse oximeters require empirical calibration which is based on SaO2 measurement in extracted arterial blood. They are still prone to error, because the path-lengths difference between the two wavelengths varies among different subjects. We have developed modified pulse oximetry, which makes use of two nearby infrared wavelengths that have relatively similar scattering constants and path-lengths and does not require an invasive calibration step. In measurements performed on adults during breath holding, the two-infrared pulse oximeter and a commercial pulse oximeter showed similar changes in SpO2. The two pulse oximeters showed similar accuracy when compared to SaO2 measurement in extracted arterial blood (the gold standard) performed in intensive care units on newborns and children with an arterial line. Errors in SpO2 because of variability in path-lengths difference between the two wavelengths are expected to be smaller in the two-infrared pulse oximeter.

Cerebral oxygen saturation and cerebrovascular instability in newborn infants with congenital heart disease compared to healthy controls

“…Cerebral oxygen saturation measured with NIRS reflects tissue oxygenation in the capillary, venous, and arterial vasculature, which is weighted to the venous blood (roughly 70-80%) [12][13][14]. We also measured pulse oximetry, which requires pulsatile flow and therefore estimates arterial oxygenation [15]. First, we ensured the infant was in a comfortable resting state (e.g., provided a pacifier), then placed a neonatal cerebral oxygen saturation sensor on the center of the infant's forehead and a preductal pulse oximetry sensor on the right hand per manufacturer guidelines.…”

The Various Oximetric Techniques Used for the Evaluation of Blood Oxygenation

“…Furthermore, by replacing R in Equation (14) with R( l 2 / l 1 ), the relationship between SaO 2 and R becomes [ 39 , 41 , 44 ]: …”

“…In the last few years, pulse oximetry that makes use of two close wavelengths in the infrared has been developed [ 39 , 41 , 59 ]. The choice of light with two close wavelengths reduces the differences between their scattering constants and path-lengths, so that the error due to the inter-subject variation in l 2 / l 1 is expected to be small relative to that experienced for red and infrared pulse oximetry.…”

“…In a recent study [ 41 ] on newborns and children with an arterial line, simultaneous measurements of SpO 2 , using two infrared wavelengths and SaO 2 by blood gases analysis on extracted blood, were performed. The mean difference between SaO 2 and SpO 2 was 3%, which was corrected by multiplying the SpO 2 results by a calibration factor of 1.03.…”

“…AC is the difference between the maximal (I D ) and minimal (I S ) light transmission through the tissue; DC is the mean light transmission during the pulse. This Figure was published in Yossef Hay et al Sensors 2018 [ 41 ].…”