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Background Assessment of fluid responsiveness is problematic in intensive care unit (ICU) patients, in particular for those undergoing modes of partial support, such as pressure support ventilation (PSV). We propose a new test, based on application of a ventilator-generated sigh, to predict fluid responsiveness in ICU patients undergoing PSV. Methods This was a prospective bi-centric interventional study conducted in two general ICUs. In 40 critically ill patients with a stable ventilatory PSV pattern and requiring volume expansion (VE), we assessed the variations in arterial systolic pressure (SAP), pulse pressure (PP) and stroke volume index (SVI) consequent to random application of 4-s sighs at three different inspiratory pressures. A radial arterial signal was directed to the MOSTCARE™ pulse contour hemodynamic monitoring system for hemodynamic measurements. Data obtained during sigh tests were recorded beat by beat, while all the hemodynamic parameters were averaged over 30 s for the remaining period of the study protocol. VE consisted of 500 mL of crystalloids over 10 min. A patient was considered a responder if a VE-induced increase in cardiac index (CI) ≥ 15% was observed. Results The slopes for SAP, SVI and PP of were all significantly different between responders and non-responders ( p  < 0.0001, p  = 0.0004 and p  < 0.0001, respectively). The AUC of the slope of SAP (0.99; sensitivity 100.0% (79.4–100.0%) and specificity 95.8% (78.8–99.9%) was significantly greater than the AUC for PP (0.91) and SVI (0.83) ( p  = 0.04 and 0.009, respectively). The SAP slope best threshold value of the ROC curve was − 4.4° from baseline. The only parameter found to be independently associated with fluid responsiveness among those included in the logistic regression was the slope for SAP ( p  = 0.009; odds ratio 0.27 (95% confidence interval (CI 95 ) 0.10–0.70)). The effects produced by the sigh at 35 cmH 2 0 (Sigh 35 ) are significantly different between responders and non-responders. For a 35% reduction in PP from baseline, the AUC was 0.91 (CI 95 0.82–0.99), with sensitivity 75.0% and specificity 91.6%. Conclusions In a selected ICU population undergoing PSV, analysis of the slope for SAP after the application of three successive sighs and the nadir of PP after Sigh 35 reliably predict fluid responsiveness. Trial registration Australian New Zealand Clinical Trials Registry, ACTRN12615001232527 . Registered on 10 November 2015.

The demand for faster and more efficient optical communication systems has driven significant advancements in integrated photonic technologies, with optical switches playing a pivotal role in high-speed, low-latency data transmission. In this work, we introduce a novel design for an adiabatic optical switch based on the thermo-optic effect using silicon-on-insulator (SOI) technology. The approach relies on slow optical signal evolution, minimizing power dissipation and addressing challenges of traditional optical switches. Machine learning (ML) techniques were employed to optimize waveguide designs, ensuring polarization-independent (PI) and single-mode (SM) conditions. The proposed design achieves low-loss and high-performance operation across a broad wavelength range (1500–1600 nm). We demonstrate the effectiveness of a Y-junction adiabatic switch, with a tapered waveguide structure, and further enhance its performance by employing thermo-optic effects in hydrogenated amorphous silicon (a-Si:H). Our simulations reveal high extinction ratios (ERs) exceeding 30 dB for TE mode and 15 dB for TM mode, alongside significant improvements in coupling efficiency and reduced insertion loss. This design offers a promising solution for integrating efficient, low-energy optical switches into large-scale photonic circuits, making it suitable for next-generation communication and high-performance computing systems.