In vivo precision assessment of a near-infrared spectroscopy-based tissue oximeter (OxyPrem v1.3) in neonates considering systemic hemodynamic fluctuations

Abstract

Abstract. The aim was to determine the precision of a noninvasive near-infrared spectroscopy (NIRS)-based tissue oximeter (OxyPrem v1.3). Using a linear mixed-effects model, we quantified the variability for cerebral tissue oxygenation (StO 2 ) measurements in 35 preterm neonates to be 2.64%, a value that meets the oftenarticulated clinicians' demand for a precise tissue oxygenation measurement. We showed that the variability of StO 2 values measured was dominated by spontaneous systemic hemodynamic fluctuations during the measurement, meaning that precision of the instrument was actually even better. Based on simultaneous and continuous measurements of peripheral arterial oxygenation and cerebral StO 2 with a second sensor, we were able to determine and quantify the physiological instability precisely. We presented different methods and analyses aiming at reducing this systematic physiological error of in vivo precision assessments. Using these methods, we estimated the precision of the OxyPrem tissue oximeter to be ≤ 1.85%. With our study, we deliver relevant information to establish highly precise cerebral oxygenation measurements with NIRS-based oximetry, facilitating the further development toward a substantially improved diagnosis and treatment of patients with respect to brain oxygenation.

Cerebral oxygenation and blood flow in normal term infants at rest measured by a hybrid near-infrared device (BabyLux)

“…Simply looking at the intra-subject standard deviation of 3.4%, not affected by the mean values, the improvement is considerable, and corresponds to a reduction in the 95% confidence interval for a measurement to ±9%-points, as opposed to ±13%-points for spatial resolved NIRS (8,9). Recently, a new SRS NIRS device has produced lower intra-subject CV for StO2, possibly related to interrogating a larger brain volume and/or an auto-calibration function (40). Reducing the confidence interval has a great impact on the clinical usefulness of a measurement as therapeutic ranges are often narrow and patient management often rely on intervention thresholds, making the reliability of the absolute value decisive.…”

Cerebral hemodynamic responses in preterm-born neonates to visual stimulation: classification according to subgroups and analysis of frontotemporal–occipital functional connectivity

“…This type of noise had been observed already by a previous analysis of measurements with our NIRS device. 25 In about 20% of the data sets, such a noise component was observed (a sinusoidal signal with a frequency of about 1 Hz and an amplitude modulation with a frequency of about 0.05 Hz). Data sets with this strong interference signal had to be completely removed from the final data sets used for the next signal-processing steps.…”

“…Before the fNIRS measurement of the stimulus-evoked HRs, baseline physiological values were measured with fNIRS, as described in a previous validation study of the new NIRS device. 25 The total measurement lasted about 15 min. The measurements were conducted by two or three persons, enabling one person to respond quickly to the behavior of the neonate while the other(s) focused on performing the measurements.…”

“…27 A similar subfigure has been already shown in a previous publication of our group. 25 removed when they exceeded a specific threshold value (T) given as T ¼ α × median [moving standard deviation (MSD)], with MSD of the whole time-series (with a window length of 20 samples i.e., 4 s) and a scaling factor that was empirically chosen (e.g., α ¼ 2.5) for each data set to ensure that no data from artifacts were present in the cleaned data. This signalprocessing step was essential to ensure that only data of sufficient quality were used in the further data analysis steps.…”

“…(1) We used a NIRS device that enables reliable measurements of cerebral oxygenation and hemodynamics with the SCMD technique. 25 (2) A bright visual stimulation has been used in our study making sure that the neonates were exposed to a sufficiently intense stimulation to elicit HRs. (3) Measurements were performed not only at the VC but also at the left FTL making it possible to investigate HRs at the left FTL as well as to investigate the fto-FC during the visual stimulation.…”