Abstract
Despite the wide range of clinical and research applications, the reliability of the absolute oxygenation measurements of continuous wave near-infrared spectroscopy sensors is often questioned, partially due to issues of standardization. In this study, we have compared the performances of 13 units of a continuous wave near-infrared spectroscopy device (PortaMon, Artinis Medical Systems, NL) to test their suitability for being used in the HEMOCOVID-19 clinical trial in 10 medical centers around the world. Detailed phantom and in vivo tests were employed to measure the precision and reproducibility of measurements of local blood oxygen saturation and total hemoglobin concentration under different conditions: for different devices used, different operators, for probe repositioning over the same location, and over time (hours/days/months). We have detected systematic differences between devices when measuring phantoms (inter-device variability, <4%), which were larger than the intra-device variability (<1%). This intrinsic variability is in addition to the variability during in vivo measurements on the forearm muscle resulting from errors in probe positioning and intrinsic physiological noise (<9%), which was also larger than the inter-device differences (<3%) during the same test. Lastly, we have tested the reproducibility of the protocol of the HEMOCOVID-19 clinical trial; that is, forearm muscle oxygenation monitoring during vascular occlusion tests over days. Overall, our conclusion is that these devices can be used in multi-center trials but care must be taken to characterize, follow-up, and statistically account for inter-device variability.
Highlights
Continuous-wave near-infrared spectroscopy (CW-NIRS) [1,2] is a non-invasive optical technique that allows the direct determination of local tissue oxy- and deoxy-hemoglobin concentrations at the microvascular level
After turning on a device, we notice a first period of warm-up during which the tissue oxygen saturation index (TSI) rapidly increases and total hemoglobin concentration (THC) rapidly decreases towards their average stable values
We have addressed, through systematic and detailed tests, some of the possible challenges and critical issues related to utilizing multiple CW-NIRS devices for a multi-center clinical trial, such as the HEMOCOVID-19 trial, which spans several months
Summary
Continuous-wave near-infrared spectroscopy (CW-NIRS) [1,2] is a non-invasive optical technique that allows the direct determination of local tissue oxy- and deoxy-hemoglobin concentrations at the microvascular level. Past studies have questioned the reliability of absolute oxygenation measurements and highlighted differences between different devices and brands, highlighting the need for improved standardization [1,3,4,5,6,7]. Despite this variability, the use of CW-NIRS sensors for tissue oxygenation monitoring is well accepted and established in both clinical and research settings [1,2,8,9]. The best established clinical uses of CW-NIRS are in the intraoperative detection of cerebral ischemia [10,11,12] and in the cerebral and peripheral muscle hemodynamic monitoring of critically ill patients in the intensive care unit (ICU) [13,14,15,16,17,18,19]
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