Agreement and repeatability of a novel cerebral NIRS device (RheoPatch) compared with NIRO-200NX in healthy volunteers

Abstract To compare the agreement and repeatability of a novel near-infrared spectroscopy (NIRS) device (RheoPatch, Luciole Medical AG, Zurich, Switzerland) with an established cerebral oximetry system (NIRO-200NX, Hamamatsu Photonics, Japan) in healthy volunteers. In this prospective single-center observational study, healthy adults underwent alternating cerebral oximetry measurements with both devices in supine and 10° Trendelenburg positions. The primary endpoint was agreement between RheoPatch regional cerebral oxygen saturation (rSO₂) and NIRO-200NX Tissue Oxygenation Index (TOI) outputs. Agreement was assessed using repeated-measures Bland-Altman analysis accounting for within-subject clustering. Repeatability after sensor reapplication was evaluated using the coefficient of repeatability (CR), intraclass correlation coefficients (ICC), and variance-component analysis. A total of 194 paired measurements from 28 healthy volunteers were analyzed after exclusion of missing or technically compromised data. RheoPatch demonstrated acceptable agreement within prespecified clinical limits (± 20% points). A proportional bias was observed, with RheoPatch yielding higher values at lower saturation levels and lower values at higher saturation levels. Repeatability metrics consistently favored RheoPatch, indicating lower measurement variability after sensor reapplication. Both devices showed stable mean values during Trendelenburg positioning. No adverse events occurred. In healthy adults, RheoPatch demonstrated clinically acceptable agreement with NIRO-200NX outputs and superior repeatability during sensor reapplication. These findings support further evaluation of RheoPatch in perioperative and critical care populations using outcome-based, device-specific thresholds.