Closing the monitoring gap: validation of a novel micro-electromechanical systems (MEMS) humidity-sensing device for continuous respiratory monitoring during patient transfer

Transfer from the operating theatre to the post-anaesthesia care unit is a high-risk period with reduced respiratory monitoring, as conventional technologies are often impractical during patient movement. We evaluated a novel, low-cost respiratory monitor using a micro-electromechanical systems humidity sensor to detect breath-by-breath ventilation in spontaneously breathing adults. In this pilot validation study, 50 healthy volunteers wore a prototype humidity sensor mounted on a standard oxygen face mask delivering 4 l.min⁻¹ supplemental oxygen, with the device generating a visual light signal for each detected breath. Respiratory rates measured over 60 s were compared with capnography, and agreement was assessed using Bland–Altman analysis and Pearson correlation. The prototype achieved a breath detection accuracy of 98.8%, with a mean bias of 0.16 breaths.min⁻¹ and 95% limits of agreement from −1.17 to +1.49 breaths.min⁻¹. Strong correlation with capnography was observed (r = 0.98, p < 0.001), and complete agreement occurred in 47 participants (94%), with discrepancies in three cases attributed to poor mask fit. This device provides an accurate, portable and inexpensive method for respiratory monitoring, offering continuous visual assurance when conventional capnography is unavailable or impractical during patient transfer.