Performance Assessment of a Commercial Continuous-Wave Near-Infrared Spectroscopy Tissue Oximeter for Suitability for Use in an International, Multi-Center Clinical Trial

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.

Keywords: continuous wave near-infrared spectroscopy; light propagation in tissue; local tissue oxygenation; medical optics; multi-center clinical trial; vascular occlusion test.

Figure 2

Experimental setup. (a) Two PortaMon (Artinis Medical Systems) devices used in this study; top and bottom view. (b) Biomimic PB312 phantom, with the custom mask for PortaMon placement. (c) One of the BioPixS phantoms, together with the custom mask (left panel, top view) and the PortaMon placed (right panel). (d) PortaMon placement for forearm muscle measurements. (e) Sketch of the VOT procedure together with a visual representation of the measured relevant parameters.

Figure 3

Overnight stability of three devices (id38, id40, and id50). In the inset, zoomed image of the $$TSI$$ and $$THC$$ during device warm-up.

Figure 4

Device characterization of Type 1 phantoms, performed on different days and months by different operators. Horizontal lines represent the average (solid line) ± standard deviation (dashed lines) over all the devices.

Figure 5

Set of 10 Type 2 phantoms measured with device id50. Horizontal lines represent the average (solid line) ± standard deviation (dashed lines) over all the phantoms. See text for details.

Figure 6

In vivo replacement tests performed with 10 devices on a single healthy subject. See text for details.

Figure 7

Parameters extracted from VOT over 20 repeated (once/day) measurements over 30 days. Horizontal lines represent the average (solid line) ± standard deviation (dashed lines) over all the measurements. See text for details.

Figure 1

A schematic summary of the challenges of a multi-center clinical study and the actions taken to address them. Icons taken from [29].